- Pediatric Cardiology
- Pediatric Heart Transplantation
- Pediatric Heart Failure
Chief, Division of Pediatric Cardiology, Stanford University (1994 - 2011)
Director, Children's Heart Center, Packard Children's Hospital at Stanford (2001 - 2011)
Honors & Awards
Alfred Woodley Salter and Mabel G. Salter Endowed Professor of Pediatrics, Stanford University (April 2004-present)
Residency:Montefiore Medical Center/Albert Einstein COM (1981) NY
Board Certification: Pediatrics, American Board of Pediatrics (1984)
Medical Education:New York University - School Of Medicine (1978) NY
Internship:Montefiore Medical Center/Albert Einstein COM (1979) NY
Board Certification: Pediatric Cardiology, American Board of Pediatrics (1985)
Fellowship:UCSF Medical Center (1986) CA
Fellowship:Albert Einstein College of Medicine (1983) NY
Current Research and Scholarly Interests
Our lab has several major focuses:
1. The role of the G protein coupled receptors in regulating cardiac function, and specifically mitochondrial structure and function.
2. Differences between right and left ventricular responses to stress and in their modes of failure, including gene expression and miR regulation.
3. Using iPSC-derived myocytes to understand heart failure and congenital heart disease.
4. We develop tools for evaluation of cardiovascular physiology in transgenic and knockout mice and in isolated cardiomyocytes.ce.
Specific projects underway in our lab include:
1. Evaluation of the role of beta1 and beta2 adrenergic receptor subtypes in regulating cardiac structure and function by studying mice with targeted gene disruption of these receptors. Evaluation of the role of crosstalk between beta receptors and other signaling pathways in regulating cardiac structure and function.
2. Role of beta receptors in regulation of mitochondrial structure and function, including processes of mitofusion, mitofission, autophagy and mitophagy.
3. Role of beta receptors in adriamycin cardiotoxicity.
4. Differences between the right and left ventricles in their responses to stresses such as increased afterload and increased preload, including gene expression and gene regulation by micro-RNAs.
5. Using patient-derived iPSC-cardiomyocytes to understand the mechanisms of cardiomyopathies common in children. Evaluation of mitochondrial function in iPSC-CMs and the ability of these cells to recapitulate mitochondrial abnormalities seen in patients with cardiomyopathy. Using iPSC-CMs to understand the mechanisms of heart failure in congenital heart disease, specifically in patients with systemic right ventricles.
6. Development of micro-engineered platforms for assessment of biomechanics of single native or iPSC-derived cardiomyocytes.
We also are interested in clinical cardiac transplantation in children, specifically:
1. Understanding the mechanisms of antibody mediated rejection.
2. Development of biomarkers for the detection and monitoring of post-transplant lymphoproliferative disorder in pediatric transplant patients.
Biomarkers for Post-Transplant Lymphoproliferative Disorders in Children
Solid organ transplantation is an important therapeutic option for children with a variety of end stage diseases. However, the same immunosuppressive medications that are required to prevent the child's immune system from attacking and rejecting the transplanted organ can predispose these individuals to developing a very serious cancer that is linked to Epstein-Barr virus (EBV).
Stanford is currently not accepting patients for this trial. For more information, please contact Sheri Krams, PhD, 650-498-6246.
Independent Studies (6)
- Directed Reading in Pediatrics
PEDS 299 (Aut, Win, Spr, Sum)
- Early Clinical Experience
PEDS 280 (Aut, Win, Spr, Sum)
- Graduate Research
PEDS 399 (Aut, Win, Spr, Sum)
- Medical Scholars Research
PEDS 370 (Aut, Win, Spr, Sum)
- Out-of-Department Advanced Research Laboratory in Experimental Biology
BIO 199X (Sum)
- Undergraduate Directed Reading/Research
PEDS 199 (Aut, Win, Spr, Sum)
- Directed Reading in Pediatrics
Quality of life and metrics of achievement in long-term adult survivors of pediatric heart transplant.
2015; 19 (1): 76-81
Many children who undergo heart transplantation will survive into adulthood. We sought to examine the QOL and capacity for achievement in long-term adult survivors of pediatric heart transplantation. Adults >18 yr of age who received transplants as children (≤18 yr old) and had survived for at least 10 yr post-transplant completed two self-report questionnaires: (i) Ferrans & Powers QLI, in which life satisfaction is reported as an overall score and in four subscale domains and is then indexed from 0 (very dissatisfied) to 1 (very satisfied); and (ii) a "Metrics of Life Achievement" questionnaire regarding income, education, relationships, housing status, and access to health care. A total of 20 subjects completed the survey. The overall mean QLI score was 0.77 ± 0.16. Subjects were most satisfied in the family domain (0.84 ± 0.21) and least satisfied in the psychological/spiritual domain (0.7 ± 0.28). Satisfaction in the domains of health/functioning and socioeconomic were intermediate at 0.78 and 0.76, respectively. Most respondents had graduated from high school, reported a median annual income >$50 000/yr, and lived independently. Adult survivors of pediatric heart transplant report a good QOL and demonstrate the ability to obtain an education, work, and live independently.
View details for DOI 10.1111/petr.12384
View details for PubMedID 25388808
Multi-institutional Study of Outcomes After Pediatric Heart Transplantation: Candidate Gene Polymorphism Analysis of ABCC2.
The journal of pediatric pharmacology and therapeutics : JPPT : the official journal of PPAG
2014; 19 (1): 16-24
Earlier studies have indicated that the pharmacokinetics of mycophenolic acid (MPA) is influenced by polymorphisms of ABCC2, which encodes for the membrane transporter MRP2. The ABCC2 rs717620 A allele has been associated with enterohepatic recirculation of MPA, and our previous work had correlated the discontinuance of MPA with this allele in pediatric heart transplant patients. Therefore, we hypothesized that the ABCC2 rs717620 A allele would be associated with poorer outcomes including rejection with hemodynamic compromise (RHC), graft failure, and death in the pediatric heart transplant (PHTx) population receiving MPA.PHTx recipients from 6 institutions in the Pediatric Heart Transplantation Study (PHTS) from the period of 1993-2009, receiving MPA therapy, were genotyped for ABCC2 rs717620. Genotyping was accomplished by direct sequencing. Demographic and outcome data were limited to the data routinely collected as part of the PHTS and included RHC and mortality.Two hundred ninety patients were identified who received MPA at some point post transplantation, of which 200 carried the GG genotype, 81 carried the AG genotype, and 9 carried the AA genotype. Follow-up time after transplantation was 6 years. RHC occurred in 76 patients and 18 patients died. In the 281 patients followed up more than 1 year, late RHC (>1 year post transplantation) occurred in 42 patients. While both RHC and late RHC were associated with the ABCC2 rs717620 GG genotype (hazard ratios: 1.80 and 4.57, respectively, p<0.05) in all patients, this association was not significant in PHTx patients receiving only MPA as the antiproliferative agent from the time of transplant (n=142).ABCC2 rs717620 polymorphisms varied within racial groups. As a candidate gene assessment, the ABCC2 rs717620 AG and AA genotypes may be associated with improved, rather than poorer, RHC in PHTx patients receiving MPA therapy. ABCC2 rs717620 polymorphisms should be included in any expanded pharmacogenomic analysis of outcomes after pediatric heart transplantation.
View details for DOI 10.5863/1551-6776-19.1.16
View details for PubMedID 24782687
Orthotopic heart transplantation in two infants with histiocytoid cardiomyopathy and left ventricular non-compaction
2013; 17 (7): E165-E167
HC is a rare cause of congestive heart failure that typically presents with malignant ventricular arrhythmias in infants, often requiring urgent intervention. Successful heart transplantation in a patient with HC has only been reported once (J Heart Lung Transplant 2004: 23: 902). The combination of HC with concurrent LVNC has only been described three times (Int J Legal Med 2009: 123: 47; Hum Pathol 2005: 36: 403; Pediatr Dev Pathol 2012: 15: 397). We report two rare cases of HC with LVNC in two infants presenting with cardiogenic shock, one requiring ECMO support who was successfully bridged to orthotopic heart transplantation with a Berlin Heart LVAD.
View details for DOI 10.1111/petr.12141
View details for Web of Science ID 000325369400004
View details for PubMedID 24099092
Deletion of the beta 2-adrenergic receptor prevents the development of cardiomyopathy in mice
JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY
2013; 63: 155-164
Beta adrenergic receptor (β-AR) subtypes act through diverse signaling cascades to modulate cardiac function and remodeling. Previous in vitro studies suggest that β1-AR signaling is cardiotoxic whereas β2-AR signaling is cardioprotective, and may be the case during ischemia/reperfusion in vivo. The objective of this study was to assess whether β2-ARs also play a cardioprotective role in the pathogenesis of non-ischemic forms of cardiomyopathy. To dissect the role of β1 vs β2-ARs in modulating MLP (Muscle LIM Protein) cardiomyopathy, we crossbred MLP-/- with β1-/- or β2-/- mice. Deletion of the β2-AR improved survival, cardiac function, exercise capacity and myocyte shortening; by contrast haploinsufficency of the β1-AR reduced survival. Pathologic changes in Ca(2+) handling were reversed in the absence of β2-ARs: peak Ca(2+) and SR Ca(2+) were decreased in MLP-/- and β1+/-/MLP-/- but restored in β2-/-MLP-/-. These changes were associated with reversal of alterations in troponin I and phospholamban phosphorylation. Gi inhibition increased peak and baseline Ca(2+), recapitulating changes observed in the β2-/-/MLP-/-. The L-type Ca(2+) blocker verapamil significantly decreased cardiac function in β2-/-MLP-/- vs WT. We next tested if the protective effects of β2-AR ablation were unique to the MLP model using TAC-induced heart failure. Similar to MLP, β2-/- mice demonstrated delayed progression of heart failure with restoration of myocyte shortening and peak Ca(2+) and Ca(2+) release. Deletion of β2-ARs prevents the development of MLP-/- cardiomyopathy via positive modulation of Ca(2+) due to removal of inhibitory Gi signaling and increased phosphorylation of troponin I and phospholamban. Similar effects were seen after TAC. Unlike previous models where β2-ARs were found to be cardioprotective, in these two models, β2-AR signaling appears to be deleterious, potentially through negative regulation of Ca(2+) dynamics.
View details for DOI 10.1016/j.yjmcc.2013.07.016
View details for Web of Science ID 000325387300017
View details for PubMedID 23920331
Lower socioeconomic status is associated with worse outcomes after both listing and transplanting children with heart failure
2013; 17 (6): 573-581
The relationship between SES and outcomes surrounding pediatric cardiac transplantation is complex and influenced by recipient race. Broad-based studies of SES have not been performed. A retrospective review of all 5125 primary pediatric heart transplants performed in the United States between 2000 and 2011. Patients were stratified by SES based on zip code of residence and U.S. census data (low SES: 1637; mid-SES: 2253; high SES: 1235). Survival following listing and transplantation was compared across strata. Risk-adjusted long-term mortality on the waitlist was higher among low SES patients (hazard 1.32, CI 1.07-1.63). The relationship between SES and outcomes varied by race. Early risk-adjusted post-transplant outcomes were worst among high SES patients (10.8% vs. low SES: 8.9%, p < 0.05). The incidence of non-compliance was higher among low SES patients (p < 0.0001). Long-term risk-adjusted patient survival was poorer among low (hazard 1.41, CI 1.10-1.80) and mid-SES (1.29, 1.04-1.59) groups. Low SES is associated with worse outcomes on both the waitlist and late following transplantation. Higher SES patients had more complex transplants with higher early mortality. Further research should be directed at identifying and addressing underlying causal factors for these disparities.
View details for DOI 10.1111/petr.12117
View details for Web of Science ID 000322317700015
View details for PubMedID 23834560
Role of telomere dysfunction in cardiac failure in Duchenne muscular dystrophy.
Nature cell biology
2013; 15 (8): 895-904
Duchenne muscular dystrophy (DMD), the most common inherited muscular dystrophy of childhood, leads to death due to cardiorespiratory failure. Paradoxically, mdx mice with the same genetic deficiency of dystrophin exhibit minimal cardiac dysfunction, impeding the development of therapies. We postulated that the difference between mdx and DMD might result from differences in telomere lengths in mice and humans. We show here that, like DMD patients, mice that lack dystrophin and have shortened telomeres (mdx/mTR(KO)) develop severe functional cardiac deficits including ventricular dilation, contractile and conductance dysfunction, and accelerated mortality. These cardiac defects are accompanied by telomere erosion, mitochondrial fragmentation and increased oxidative stress. Treatment with antioxidants significantly retards the onset of cardiac dysfunction and death of mdx/mTR(KO) mice. In corroboration, all four of the DMD patients analysed had 45% shorter telomeres in their cardiomyocytes relative to age- and sex-matched controls. We propose that the demands of contraction in the absence of dystrophin coupled with increased oxidative stress conspire to accelerate telomere erosion culminating in cardiac failure and death. These findings provide strong support for a link between telomere length and dystrophin deficiency in the etiology of dilated cardiomyopathy in DMD and suggest preventive interventions.
View details for DOI 10.1038/ncb2790
View details for PubMedID 23831727
- Role of telomere dysfunction in cardiac failure in Duchenne muscular dystrophy NATURE CELL BIOLOGY 2013; 15 (8): 895-U300
Physiologic and molecular characterization of a murine model of right ventricular volume overload.
American journal of physiology. Heart and circulatory physiology
2013; 304 (10): H1314-27
Pulmonary insufficiency (PI) is a common long-term sequel after repair of tetralogy of Fallot, causing progressive right ventricular (RV) dilation and failure. We describe the physiologic and molecular characteristics of the first murine model of RV volume overload. PI was created by entrapping the pulmonary valve leaflets with sutures. Imaging, catheterization, and exercise testing were performed at 1, 3, and 6 mo and compared with sham controls. RNA from the RV free wall was hybridized to Agilent whole genome oligonucleotide microarrays. Volume overload resulted in RV enlargement, decreased RV outflow tract shortening fraction at 1 mo followed by normalization at 3 and 6 mo (39 ± 2, 44 ± 2, and 41 ± 2 vs. 46 ± 3% in sham), early reversal of early and late diastolic filling velocities (E/A ratio) followed by pseudonormalization (0.87 ± 0.08, 0.82 ± 0.08, and 0.96 ± 0.08 vs. 1.04 ± 0.03; P < 0.05), elevated end-diastolic pressure (7.6 ± 0.7, 6.9 ± 0.8, and 7 ± 0.5 vs. 2.7 ± 0.2 mmHg; P < 0.05), and decreased exercise duration (26 ± 0.4, 26 ± 1, and 22 ± 1.3 vs. 30 ± 1.1 min; P < 0.05). Subendocardial RV fibrosis was evident by 1 mo. At 1 mo, 372 genes were significantly downregulated. Mitochondrial pathways and G protein-coupled receptor signaling were the most represented categories. At 3 mo, 434 genes were upregulated and 307 downregulated. While many of the same pathways continued to be downregulated, TNF-α, transforming growth factor-β1 (TGF-β1), p53-signaling, and extracellular matrix (ECM) remodeling transitioned from down- to upregulated. We describe a novel murine model of chronic RV volume overload recapitulating aspects of the clinical disease with gene expression changes suggesting early mitochondrial bioenergetic dysfunction, enhanced TGF-β signaling, ECM remodeling, and apoptosis.
View details for DOI 10.1152/ajpheart.00776.2012
View details for PubMedID 23504182
- Physiologic and molecular characterization of a murine model of right ventricular volume overload AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY 2013; 304 (10): H1314-H1327
Abdominal complaints as a common first presentation of heart failure in adolescents with dilated cardiomyopathy
AMERICAN JOURNAL OF EMERGENCY MEDICINE
2013; 31 (4): 684-686
We hypothesized that isolated gastrointestinal complaints (abdominal pain, nausea, anorexia, weight loss), in the absence of other symptoms, were a common mode of initial presentation in children with congestive heart failure (CHF).Ninety-eight patients younger than 18 years hospitalized with dilated cardiomyopathy at a single institution between January 1, 2000, and December 31, 2009, were included. Retrospective review of their presenting complaints was recorded and analyzed according to 3 age groups: 0 to 1 year (infants), 1 to 10 years (children), and 11 to 18 years (adolescents) of age.Respiratory symptoms were common in all age groups (range, 56%-63%). Gastrointestinal complaints were also common in all age groups (42%, 28%, and 65%, respectively) and were more frequent than respiratory complaints in adolescents. Adolescents were likely to present with abdominal pain as their only complaint (10/43, 23%). Chest pain, syncope, or cardiac arrest occurred rarely.Abdominal complaints are a common component of the presenting symptom complex of CHF in pediatric dilated cardiomyopathy in all age groups. In adolescents, abdominal complaints occur more frequently than respiratory complaints and often in the absence of any other symptoms. Unlike CHF in adults, chest pain, arrhythmia, or cardiac arrest occurs rarely at presentation in pediatric patients. Recognition of the different presenting symptoms of heart failure in children by primary providers is crucial to ensuring prompt diagnosis and timely initiation of therapy.
View details for DOI 10.1016/j.ajem.2012.12.009
View details for Web of Science ID 000316723400010
View details for PubMedID 23380118
Intermediate-term outcomes after combined heart-liver transplantation in children with a univentricular heart
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2013; 32 (3): 368-370
For patients with end-stage hepatic failure secondary to failing hemodynamics, combined heart-liver transplant (H-LT) remains the only option for long-term survival. We report a series of three pediatric patients who successfully underwent orthotopic H-LT for failed single-ventricle palliation. All three patients are currently living, now two, three, and five years post-transplant, and remain completely free of cardiac cellular allograft rejection despite reduced immunosuppression protocols. One patient, however, did develop acute antibody-mediated rejection in the immediate post-transplant period, suggesting that this protective effect may be less effective in attenuating humoral mechanisms of rejection.
View details for DOI 10.1016/j.healun.2012.11.023
View details for Web of Science ID 000315664600014
Sacrificial layer technique for axial force post assay of immature cardiomyocytes
2013; 15 (1): 171-181
Immature primary and stem cell-derived cardiomyocytes provide useful models for fundamental studies of heart development and cardiac disease, and offer potential for patient specific drug testing and differentiation protocols aimed at cardiac grafts. To assess their potential for augmenting heart function, and to gain insight into cardiac growth and disease, tissue engineers must quantify the contractile forces of these single cells. Currently, axial contractile forces of isolated adult heart cells can only be measured by two-point methods such as carbon fiber techniques, which cannot be applied to neonatal and stem cell-derived heart cells because they are more difficult to handle and lack a persistent shape. Here we present a novel axial technique for measuring the contractile forces of isolated immature cardiomyocytes. We overcome cell manipulation and patterning challenges by using a thermoresponsive sacrificial support layer in conjunction with arrays of widely separated elastomeric microposts. Our approach has the potential to be high-throughput, is functionally analogous to current gold-standard axial force assays for adult heart cells, and prescribes elongated cell shapes without protein patterning. Finally, we calibrate these force posts with piezoresistive cantilevers to dramatically reduce measurement error typical for soft polymer-based force assays. We report quantitative measurements of peak contractile forces up to 146 nN with post stiffness standard error (26 nN) far better than that based on geometry and stiffness estimates alone. The addition of sacrificial layers to future 2D and 3D cell culture platforms will enable improved cell placement and the complex suspension of cells across 3D constructs.
View details for DOI 10.1007/s10544-012-9710-3
View details for Web of Science ID 000313517800018
Brg1 governs distinct pathways to direct multiple aspects of mammalian neural crest cell development
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2013; 110 (5): 1738-1743
Development of the cerebral vessels, pharyngeal arch arteries (PAAs). and cardiac outflow tract (OFT) requires multipotent neural crest cells (NCCs) that migrate from the neural tube to target tissue destinations. Little is known about how mammalian NCC development is orchestrated by gene programming at the chromatin level, however. Here we show that Brahma-related gene 1 (Brg1), an ATPase subunit of the Brg1/Brahma-associated factor (BAF) chromatin-remodeling complex, is required in NCCs to direct cardiovascular development. Mouse embryos lacking Brg1 in NCCs display immature cerebral vessels, aberrant PAA patterning, and shortened OFT. Brg1 suppresses an apoptosis factor, Apoptosis signal-regulating kinase 1 (Ask1), and a cell cycle inhibitor, p21(cip1), to inhibit apoptosis and promote proliferation of NCCs, thereby maintaining a multipotent cell reservoir at the neural crest. Brg1 also supports Myosin heavy chain 11 (Myh11) expression to allow NCCs to develop into mature vascular smooth muscle cells of cerebral vessels. Within NCCs, Brg1 partners with chromatin remodeler Chromodomain-helicase-DNA-binding protein 7 (Chd7) on the PlexinA2 promoter to activate PlexinA2, which encodes a receptor for semaphorin to guide NCCs into the OFT. Our findings reveal an important role for Brg1 and its downstream pathways in the survival, differentiation, and migration of the multipotent NCCs critical for mammalian cardiovascular development.
View details for DOI 10.1073/pnas.1218072110
View details for Web of Science ID 000314558100038
View details for PubMedID 23319608
Loss of adenomatous poliposis coli-a3 integrin interaction promotes endothelial apoptosis in mice and humans.
2012; 111 (12): 1551-1564
Pulmonary hypertension (PH) is characterized by progressive elevation in pulmonary pressure and loss of small pulmonary arteries. As bone morphogenetic proteins promote pulmonary angiogenesis by recruiting the Wnt/?-catenin pathway, we proposed that ?-catenin activation could reduce loss and induce regeneration of small pulmonary arteries (PAs) and attenuate PH.This study aims to establish the role of ?-catenin in protecting the pulmonary endothelium and stimulating compensatory angiogenesis after injury.To assess the impact of ?-catenin activation on chronic hypoxia-induced PH, we used the adenomatous polyposis coli (Apc(Min/+)) mouse, where reduced APC causes constitutive ?-catenin elevation. Surprisingly, hypoxic Apc(Min/+) mice displayed greater PH and small PA loss compared with control C57Bl6J littermates. PA endothelial cells isolated from Apc(Min/+) demonstrated reduced survival and angiogenic responses along with a profound reduction in adhesion to laminin. The mechanism involved failure of APC to interact with the cytoplasmic domain of the ?3 integrin, to stabilize focal adhesions and activate integrin-linked kinase-1 and phospho Akt. We found that PA endothelial cells from lungs of patients with idiopathic PH have reduced APC expression, decreased adhesion to laminin, and impaired vascular tube formation. These defects were corrected in the cultured cells by transfection of APC.We show that APC is integral to PA endothelial cells adhesion and survival and is reduced in PA endothelial cells from PH patient lungs. The data suggest that decreased APC may be a cause of increased risk or severity of PH in genetically susceptible individuals.
View details for DOI 10.1161/CIRCRESAHA.112.267849
View details for PubMedID 23011394
- Loss of Adenomatous Poliposis Coli-alpha 3 Integrin Interaction Promotes Endothelial Apoptosis in Mice and Humans CIRCULATION RESEARCH 2012; 111 (12): 1551-?
Renal function and genetic polymorphisms in pediatric heart transplant recipients
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2012; 31 (9): 1003-1008
Common genetic variations influence rejection, infection, drug metabolism, and side effect profiles after pediatric heart transplantation. Reports in adults suggest that genetic background may influence post-transplant renal function. In this multicenter study, we investigated the association of genetic polymorphisms (GPs) in a panel of candidate genes on renal function in 453 pediatric heart transplant recipients.We performed genotyping for functional GPs in 19 candidate genes. Renal function was determined annually after transplantation by calculation of the estimated glomerular filtration rate (eGFR). Mixed-effects and Cox proportional hazard models were used to assess recipient characteristics and the effect of GPs on longitudinal eGFR and time to eGFR < 60 mL/min/1.73m(2).Mean age at transplantation was 6.2 ± 6.1 years. Mean follow-up was 5.1 ± 2.5 years. Older age at transplant and black race were independently associated with post-transplant renal dysfunction. Univariate analyses showed FASL (C-843T) T allele (p = 0.014) and HO-1 (A326G) G allele (p = 0.0017) were associated with decreased renal function. After adjusting for age and race, these associations were attenuated (FASL, p = 0.075; HO-1, p = 0.053). We found no associations of other GPs with post-transplant renal function, including GPs in TGF?1, CYP3A5, ABCB1, and ACE.In this multicenter, large, sample of pediatric heart transplant recipients, we found no strong associations between GPs in 19 candidate genes and post-transplant renal function. Our findings contradict reported associations of CYP3A5 and TGF?1 with renal function and suggest that genotyping for these GPs will not facilitate individualized immunosuppression for the purpose of protecting renal function after pediatric heart transplantation.
View details for DOI 10.1016/j.healun.2012.05.010
View details for Web of Science ID 000308120200011
View details for PubMedID 22789135
Outcomes of Children Following a First Hospitalization for Dilated Cardiomyopathy
2012; 5 (4): 437-443
We hypothesized that children with dilated cardiomyopathy who require hospital admission are at increased risk for death or transplantation during their first hospitalization and in the first year that follows. We also assessed the value of routine data collected during that time to predict death or the need for transplantation prior to discharge and within 1 year of admission.We conducted a retrospective review of 83 pediatric patients with dilated cardiomyopathy whose initial hospitalization fell between 2004 and 2009. The mean age at hospitalization was 7 years. The majority of patients demonstrated moderate or severe left ventricular dysfunction on initial echocardiogram (80%) and/or the need for intravenous inotropes within 7 days of hospital admission (69%). Five patients (6%) died, and 15 (18%) were transplanted in the initial hospitalization. At 1 year, 11/71 (15%) had died, and 27/71 (38%) were transplanted. The overall freedom from death, transplantation, or rehospitalization at 1 year following admission was 21%. Fractional shortening, left ventricular ejection fraction, serum cholesterol, uric acid, mixed venous saturation, and atrial filling pressures were all predictive of death or transplantation during the initial hospitalization. Left ventricular ejection fraction was predictive of death or transplantation at 1 year.The first hospitalization for dilated cardiomyopathy marks a period of high risk for clinical decline, end stage heart failure, and the need for cardiac transplantation. Echocardiographic function and hemodynamic and serum measurements may aid in predicting outcomes. Despite medical management, most patients will be rehospitalized and/or require cardiac transplantation within 1 year of admission.
View details for DOI 10.1161/CIRCHEARTFAILURE.111.964510
View details for Web of Science ID 000313578100013
View details for PubMedID 22570362
Dynamic microRNA expression during the transition from right ventricular hypertrophy to failure
2012; 44 (10): 562-575
MicroRNAs (miRs) are small, noncoding RNAs that are emerging as crucial regulators of cardiac remodeling in left ventricular hypertrophy (LVH) and failure (LVF). However, there are no data on their role in right ventricular hypertrophy (RVH) and failure (RVF). This is a critical question given that the RV is uniquely at risk in patients with congenital right-sided obstructive lesions and in those with systemic RVs. We have developed a murine model of RVH and RVF using pulmonary artery constriction (PAC). miR microarray analysis of RV from PAC vs. control demonstrates altered miR expression with gene targets associated with cardiomyocyte survival and growth during hypertrophy (miR 199a-3p) and reactivation of the fetal gene program during heart failure (miR-208b). The transition from hypertrophy to heart failure is characterized by apoptosis and fibrosis (miRs-34, 21, 1). Most are similar to LVH/LVF. However, there are several key differences between RV and LV: four miRs (34a, 28, 148a, and 93) were upregulated in RVH/RVF that are downregulated or unchanged in LVH/LVF. Furthermore, there is a corresponding downregulation of their putative target genes involving cell survival, proliferation, metabolism, extracellular matrix turnover, and impaired proteosomal function. The current study demonstrates, for the first time, alterations in miRs during the process of RV remodeling and the gene regulatory pathways leading to RVH and RVF. Many of these alterations are similar to those in the afterload-stressed LV. miRs differentially regulated between the RV and LV may contribute to the RVs increased susceptibility to heart failure.
View details for DOI 10.1152/physiolgenomics.00163.2011
View details for Web of Science ID 000304367600003
View details for PubMedID 22454450
- Use of the Impella 5.0 as a bridge from ECMO to implantation of the HeartMate II left ventricular assist device in a pediatric patient PEDIATRIC TRANSPLANTATION 2012; 16 (2): 205-206
In Vivo Functional and Transcriptional Profiling of Bone Marrow Stem Cells After Transplantation Into Ischemic Myocardium
ARTERIOSCLEROSIS THROMBOSIS AND VASCULAR BIOLOGY
2012; 32 (1): 92-102
Clinical trials of bone marrow-derived stem cell therapy for the heart have yielded variable results. The basic mechanism(s) that underlies their potential efficacy remains unknown. In the present study, we evaluated the survival kinetics, transcriptional response, and functional outcome of intramyocardial bone marrow mononuclear cell (BMMC) transplantation for cardiac repair in a murine myocardial infarction model.We used bioluminescence imaging and high-throughput transcriptional profiling to evaluate the in vivo survival kinetics and gene expression changes of transplanted BMMCs after their engraftment into ischemic myocardium. Our results demonstrate short-lived survival of cells following transplant, with less than 1% of cells surviving by 6 weeks posttransplantation. Moreover, transcriptomic analysis of BMMCs revealed nonspecific upregulation of various cell regulatory genes, with a marked downregulation of cell differentiation and maturation pathways. BMMC therapy caused limited improvement of heart function as assessed by echocardiography, invasive hemodynamics, and positron emission tomography. Histological evaluation of cell fate further confirmed findings of the in vivo cell tracking and transcriptomic analysis.Collectively, these data suggest that BMMC therapy, in its present iteration, may be less efficacious than once thought. Additional refinement of existing cell delivery protocols should be considered to induce better therapeutic efficacy.
View details for DOI 10.1161/ATVBAHA.111.238618
View details for Web of Science ID 000298288700014
View details for PubMedID 22034515
Pharmacological inhibition of beta IIPKC is cardioprotective in late-stage hypertrophy
JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY
2011; 51 (6): 980-987
We previously found that in the hearts of hypertensive Dahl salt-sensitive rats, ?IIPKC levels increase during the transition from compensated cardiac hypertrophy to cardiac dysfunction. Here we showed that a six-week treatment of these hypertensive rats with a ?IIPKC-specific inhibitor, ?IIV5-3, prolonged their survival by at least 6weeks, suppressed myocardial fibrosis and inflammation, and delayed the transition from compensated hypertrophy to cardiac dysfunction. In addition, changes in the levels of the Ca(2+)-handling proteins, SERCA2 and the Na(+)/Ca(2+) exchanger, as well as troponin I phosphorylation, seen in the control-treated hypertensive rats were not observed in the ???PKC-treated rats, suggesting that ???PKC contributes to the regulation of calcium levels in the myocardium. In contrast, treatment with the selective inhibitor of ?IPKC, an alternative spliced form of ?IIPKC, had no beneficial effects in these rats. We also found that ?IIV5-3, but not ?IV5-3, improved calcium handling in isolated rat cardiomyocytes and enhanced contractility in isolated rat hearts. In conclusion, our data using an in vivo model of cardiac dysfunction (late-phase hypertrophy), suggest that ?IIPKC contributes to the pathology associated with heart failure and thus an inhibitor of ?IIPKC may be a potential treatment for this disease.
View details for DOI 10.1016/j.yjmcc.2011.08.025
View details for Web of Science ID 000296943800014
View details for PubMedID 21920368
beta 2-adrenergic receptors mediate cardioprotection through crosstalk with mitochondrial cell death pathways
JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY
2011; 51 (5): 781-789
?-adrenergic receptors (?-ARs) modulate cardiotoxicity/cardioprotection through crosstalk with multiple signaling pathways. We have previously shown that ?2-ARs are cardioprotective during exposure to oxidative stress induced by doxorubicin (DOX). DOX cardiotoxicity is mediated in part through a Ca(2+)-dependent opening of the mitochondrial permeability transition (MPT), however the signals linking a cell surface receptor like the ?2-AR to regulators of mitochondrial function are not clear. The objective of this study was to assess mechanisms of crosstalk between ?2-ARs and mitochondrial cell death pathways. DOX administered to WT mice resulted in no acute mortality, however 85% of ?2-/- mice died within 30 min. Several pro- and anti-survival pathways were altered. The pro-survival kinase, ?PKC, was decreased by 64% in ?2-/- after DOX vs WT (p<0.01); the ?PKC activator ??RACK partially rescued these mice (47% reduction in mortality). Activity of the pro-survival kinase Akt decreased by 76% in ?2-/- after DOX vs WT (p<0.01). The ?1-antagonist prazosin restored Akt activity to normal and also partially reversed the mortality (45%). Deletion of the ?2-AR increased rate of Ca(2+) release by 75% and peak [Ca(2+)](i) by 20% respectively in isolated cardiomyocytes; the Ca(2+) channel blocker verapamil also partially rescued the ?2-/- (26%). Mitochondrial architecture was disrupted and complex I and II activities decreased by 40.9% and 34.6% respectively after DOX only in ?2-/-. The MPT blocker cyclosporine reduced DOX mortality by 41% and prazosin plus cyclosporine acted synergistically to decrease mortality by 85%. ?2-ARs activate pro-survival kinases and attenuate mitochondrial dysfunction during oxidative stress; absence of ?2-ARs enhances cardiotoxicity via negative regulation of survival kinases and enhancement of intracellular Ca(2+), thus predisposing the mitochondria to opening of the MPT.
View details for DOI 10.1016/j.yjmcc.2011.06.019
View details for Web of Science ID 000295604500018
View details for PubMedID 21756913
Cardiac pressure overload hypertrophy is differentially regulated by beta-adrenergic receptor subtypes
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2011; 301 (4): H1461-H1470
In isolated myocytes, hypertrophy induced by norepinephrine is mediated via ?(1)-adrenergic receptors (ARs) and not ?-ARs. However, mice with deletions of both major cardiac ?(1)-ARs still develop hypertrophy in response to pressure overload. Our purpose was to better define the role of ?-AR subtypes in regulating cardiac hypertrophy in vivo, important given the widespread clinical use of ?-AR antagonists and the likelihood that patients treated with these agents could develop conditions of further afterload stress. Mice with deletions of ?(1), ?(2), or both ?(1)- and ?(2)-ARs were subjected to transverse aortic constriction (TAC). After 3 wk, ?(1)(-/-) showed a 21% increase in heart to body weight vs. sham controls, similar to wild type, whereas ?(2)(-/-) developed exaggerated (49% increase) hypertrophy. Only when both ?-ARs were ablated (?(1)?(2)(-/-)) was hypertrophy totally abolished. Cardiac function was preserved in all genotypes. Several known inhibitors of cardiac hypertrophy (FK506 binding protein 5, thioredoxin interacting protein, and S100A9) were upregulated in ?(1)?(2)(-/-) compared with the other genotypes, whereas transforming growth factor-?(2), a positive mediator of hypertrophy was upregulated in all genotypes except the ?(1)?(2)(-/-). In contrast to recent reports suggesting that angiogenesis plays a critical role in regulating cardiac hypertrophy-induced heart failure, we found no evidence that angiogenesis or its regulators (VEGF, Hif1?, and p53) play a role in compensated cardiac hypertrophy. Pressure overload hypertrophy in vivo is dependent on a coordination of signaling through both ?(1)- and ?(2)-ARs, mediated through several key cardiac remodeling pathways. Angiogenesis is not a prerequisite for compensated cardiac hypertrophy.
View details for DOI 10.1152/ajpheart.00453.2010
View details for Web of Science ID 000295360100028
View details for PubMedID 21705675
Familial Cardiac Valvulopathy Due to Filamin A Mutation
AMERICAN JOURNAL OF MEDICAL GENETICS PART A
2011; 155A (9): 2236-2241
We report on the clinical findings in siblings affected by the recently characterized X-linked form of hereditary cardiac valvular dystrophy or cardiac valve disease (OMIM 314400) due to mutations in the FLNA gene and review the literature on this condition. Although FLNA related cardiac valve disease is presumed to be a rare disorder, it is likely underdiagnosed. Several features of this condition may aid in its identification. FLNA related valvular disease can be recognized on the basis of its distinctive inheritance, early age of onset, and frequent multi-valve involvement.
View details for DOI 10.1002/ajmg.a.34132
View details for Web of Science ID 000294182500031
View details for PubMedID 21815255
Gene Polymorphisms Impact the Risk of Rejection With Hemodynamic Compromise: A Multicenter Study
2011; 91 (12): 1326-1332
Rejection with hemodynamic compromise (RHC) is associated with high mortality in heart recipients. This study investigates the association between genetic polymorphisms and RHC in pediatric heart recipients.Data from 532 pediatric heart recipients from six centers in the Pediatric Heart Transplant Study were analyzed for time to RHC by recipient race, age at transplantation, and genotype at 13 genetic polymorphisms (TNF-? A-308G, IL-6 G-174C, INF-? T+874A, IL-10 G-1082A, C-819T, and C-592A; FAS A-670G, FASL C-843T, and ACE I/D; and VEGF A-2578C, C-1451T, C+405G, and -2549 I/D).RHC occurred in 126 (23.7%) patients during the study period. Adjusting for age and race, IL-10 G-1082A, FAS A-670G, and ACE I/D genotypes were associated with RHC. IL-10 G-1082A GG genotype was associated with decreased risk of RHC with an adjusted hazard ratio (HR) of 0.49 (95% confidence interval [CI], 0.27-0.90; P=0.020). FAS A-670G AA genotype was associated with increased risk of RHC with an adjusted HR of 1.84 (95% CI, 1.25-2.69; P=0.002). ACE II genotype was associated with decreased risk of RHC with an adjusted HR of 0.58 (95% CI, 0.36-0.95; P=0.031).Recipients with a high anti-inflammatory and immune-regulatory genetic profile (high interleukin-10) were protected from RHC. Conversely, recipients with a pro-apoptotic genetic profile (high Fas) or high angiotensin-1-converting enzyme producing genotype were at increased risk of RHC. This represents progress toward understanding the genetic risk factors of posttransplantation outcomes in pediatric heart recipients.
View details for DOI 10.1097/TP.0b013e31821c1e10
View details for Web of Science ID 000291430500007
View details for PubMedID 21659963
- Calibrated micropost arrays for biomechanical characterisation of cardiomyocytes MICRO & NANO LETTERS 2011; 6 (5): 317-322
Clinical usefulness of a novel C1q assay to detect immunoglobulin G antibodies capable of fixing complement in sensitized pediatric heart transplant patients
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2011; 30 (2): 158-163
Donor-specific antibodies (DSA) against human leukocyte antigens complicate transplantation with the potential for acute antibody-mediated rejection (AMR). Complement-fixing antibodies are required to initiate the complement cascade. Not all DSAs, however, can fix complement.A novel C1q assay was developed to detect the sub-set of immunoglobulin G (IgG) antibodies capable of fixing complement. Sera from 18 pediatric heart transplant patients were analyzed for DSAs using a Luminex platform (Luminex Inc, Austin, TX) and commercially available single-antigen bead assay kits. Biopsy specimens were assessed for AMR using histopathologic criteria and immunohistochemical staining.During the study period, 5 patients had AMR; of these, 2 were C1q virtual crossmatch positive (VXM+) and had persistent C1q DSAs after transplant, and 3 were C1q VXM- but antibody developed immediately after transplant. A positive C1q assay in the immediate post-transplant period had a positive predictive value (PPV) of 100% and a negative predictive value (NPV) of 100%, with 100% sensitivity and 100% specificity (Fisher exact p = 0.001). Of 11 patients who were IgG VXM+, 5 had AMR; the IgG VXM had a PPV of 45% and NPV of 100%, with 100% sensitivity and 54% specificity (Fisher exact p = 0.101).The C1q assay can detect a sub-set of antibodies capable of fixing complement and predicts AMR early after transplant. Avoiding only the donor antigens that would be recognized by the C1q assay may accelerate time to transplant by expansion of the donor pool and potentially allows transplantation of previously "incompatible" organs.
View details for DOI 10.1016/j.healun.2010.08.020
View details for Web of Science ID 000286545200008
View details for PubMedID 20951058
NEW DIRECTIONS IN BASIC RESEARCH IN HYPERTROPHY AND HEART FAILURE: RELEVANCE FOR PEDIATRIC CARDIOLOGY.
Progress in pediatric cardiology
2011; 32 (1): 5-9
View details for PubMedID 21927547
THE ROLE OF ?-ADRENERGIC RECEPTORS IN HEART FAILURE: DIFFERENTIAL REGULATION OF CARDIOTOXICITY AND CARDIOPROTECTION.
Progress in pediatric cardiology
2011; 31 (1): 35-38
?-adrenergic receptor blockers have demonstrated significant survival benefit and have become standard therapy for adults with dilated cardiomyopathy, although their efficacy in pediatric patients is still unproven. Recent data suggests that the two major cardiac ?-adrenergic receptor subtypes (?1 and ?2) couple differentially to intracellular signaling pathways regulating contractility and remodeling. This has led some to suggest that the ?1 receptor is the "cardiotoxic subtype" whereas the ?2 receptor is "cardioprotective." Given this paradigm, there could be situations where subtype selective ?-blockade or even subtype selective ?-stimulation might be beneficial. However, since most of these studies have been performed in isolated cardiomyocytes, their application to clinical practice is unclear. To better understand the roles of ?1- vs. ?2-receptors in the pathogenesis of clinical cardiomyopathy, we and others have taken advantage of several well-characterized murine models of cardiovascular disease. These studies demonstrate that ?-receptor regulation of the balance between cardioprotection and cardiotoxicity is even more complex than previously appreciated: the role of each ?-receptor subtype may vary depending on the specific cardiac stressor involved (e.g. ischemia, pressure overload, genetic mutation, cardiotoxin). Furthermore, the remodeling effects of ?-receptor signaling have a temporal component, depending on whether a cardiac stress is acute vs. chronic.
View details for PubMedID 21765627
Association of genetic polymorphisms and risk of Late post-transplantation infection in pediatric heart recipients
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2010; 29 (12): 1342-1351
Late infections are common causes of morbidity and mortality after pediatric heart transplantation. In this multicenter study from 6 centers, we investigated the association between genetic polymorphisms (GPs) in immune response genes and late post-transplantation infections in 524 patients.Late infection was defined as a clinical infectious process occurring >60 days after transplantation and requiring hospitalization, intravenous antimicrobial therapy, or a life-threatening infection requiring oral therapy. All patients provided a blood sample for GP analyses of 18 GPs in cytokine, growth factor, and effector molecule genes by single specific primer-polymerase chain reaction and/or sequencing. Significant associations in univariable analyses were tested in multivariable Cox regression models.Late infection was common, with 48.7% of patients experiencing ? 1 late infection, 25.2% had ? 1 late bacterial infection, and 30.5% had ? 1 late viral infection. Older age at transplantation was a protective factor for late infection, both bacterial and viral (hazard ratio [HR] 0.89-0.92 per 1-year age increase, p < 0.001). Adjusting for age, race, and transplant etiology, late bacterial infection was associated with HMOX1 A+326G AG and GG genotypes (HR, 2.41, 95% confidence interval [CI] 1.35-4.30; p = 0.003) and GZMB A-295G AA genotype (HR, 1.47; 95% CI; 1.03-2.1; p = 0.036). Late viral infection was associated with FAS A-670G GG genotype (HR, 1.42; 95% CI, 1.00-2.00; p = 0.050) in the adjusted model and with CTLA4 A+49G AA and AG genotypes (HR, 1.49; 95% CI, 1.02-2.19; p = 0.041) in univariable analysis.We found an association between late bacterial infection and GP of HMOX1, which may control macrophage activation. A weaker association was also found between late viral infection and GP of CTLA4, a regulator of T-cell activation. This represents progress toward understanding the clinical and genetic risk factors of outcomes after transplantation.
View details for DOI 10.1016/j.healun.2010.07.013
View details for Web of Science ID 000285220700004
View details for PubMedID 20869265
Behcet's disease and heart transplantation: A word of caution
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2010; 29 (11): 1306-1308
Behcet's disease is a rare autoimmune disease characterized by oral and genital ulcers, and by multisystem disease, including arthritis, neurologic complications and vasculitis. Large-vessel and coronary artery aneurysms are often an indication for surgery, but the return of aneurysms, thrombosis, and the tendency to exhibit an exaggerated inflammatory response at puncture sites (pathergy) complicate surgical recovery. As such, cardiac transplantation, which requires atrial and large-vessel anastomoses, has not been reported in patients with Behcet's disease. We report the first orthotopic heart transplant with >1-year survival in a patient with Behcet's disease despite major complications. The investigators remain pessimistic about cardiac transplantation in patients with Behcet's disease until advances in preventing recurrent vascular pathology ensue.
View details for DOI 10.1016/j.healun.2010.07.010
View details for Web of Science ID 000284030700015
View details for PubMedID 20822920
Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS)-Defined Morbidity and Mortality Associated With Pediatric Ventricular Assist Device Support at a Single US Center The Stanford Experience
2010; 3 (6): 682-688
The use of ventricular assist devices (VADs) to bridge pediatric patients to heart transplantation has increased dramatically over the last 15 years. In this report, we present the largest US single-center report of pediatric VAD use to date. We present detailed descriptions of morbidity and mortality associated with VAD support, using standard Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) criteria for pediatrics to facilitate the comparison of these results to other studies.We retrospectively identified 25 patients younger than 18 years with 27 episodes of mechanical circulatory support using VADs as bridge to heart transplantation from January 1998 to December 2007. Survival to transplant for the entire cohort was 74%. The most common major morbidities, as defined by INTERMACS criteria for a pediatric population, were respiratory failure, major localized infections, major bleeding events, hepatic dysfunction, and right heart failure. Major neurological events occurred in 48% of the study population. The median time to the first occurrence of an adverse event was less than 14 days for respiratory failure, right heart failure, major localized infection, and major bleeding. Patients who died before transplantation had significantly more adverse events per day of support than did those who were successfully transplanted. Episodes of major bleeding, tamponade, acute renal failure, respiratory failure, and right heart failure were all associated with increased risk of mortality.INTERMACS criteria can be successfully used to analyze pediatric VAD outcomes. These data serve as a baseline for future studies of VAD support in children and indicate good survival rates but considerable morbidity.
View details for DOI 10.1161/CIRCHEARTFAILURE.109.918672
View details for Web of Science ID 000284261600011
View details for PubMedID 20807863
Endogenous regulation of cardiovascular function by apelin-APJ
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2009; 297 (5): H1904-H1913
Studies have shown significant cardiovascular effects of exogenous apelin administration, including the potent activation of cardiac contraction. However, the role of the endogenous apelin-APJ pathway is less clear. To study the loss of endogenous apelin-APJ signaling, we generated mice lacking either the ligand (apelin) or the receptor (APJ). Apelin-deficient mice were viable, fertile, and showed normal development. In contrast, APJ-deficient mice were not born in the expected Mendelian ratio, and many showed cardiovascular developmental defects. Under basal conditions, both apelin and APJ null mice that survived to adulthood manifested modest decrements in contractile function. However, with exercise stress both mutant lines demonstrated consistent and striking decreases in exercise capacity. To explain these findings, we explored the role of autocrine signaling in vitro using field stimulation of isolated left ventricular cardiomyocytes lacking either apelin or APJ. Both groups manifested less sarcomeric shortening and impaired velocity of contraction and relaxation with no difference in calcium transient. Taken together, these results demonstrate that endogenous apelin-APJ signaling plays a modest role in maintaining basal cardiac function in adult mice with a more substantive role during conditions of stress. In addition, an autocrine pathway seems to exist in myocardial cells, the ablation of which reduces cellular contraction without change in calcium transient. Finally, differences in the developmental phenotype between apelin and APJ null mice suggest the possibility of undiscovered APJ ligands or ligand-independent effects of APJ.
View details for DOI 10.1152/ajpheart.00686.2009
View details for Web of Science ID 000271143400045
View details for PubMedID 19767528
Association of Left Ventricular Dilation at Listing for Heart Transplant With Postlisting and Early Posttransplant Mortality in Children With Dilated Cardiomyopathy
2009; 2 (6): 591-U100
In patients with dilated cardiomyopathy, the magnitude of cardiac remodeling often correlates with the clinical severity of heart failure. We sought to determine whether measures of left ventricular (LV) dilation and systolic dysfunction in children with dilated cardiomyopathy at the time of listing for cardiac transplantation are associated with survival while waiting for and early after transplant.We analyzed echocardiographic data obtained within 6 months of listing for heart transplant and clinical data from 261 children with dilated cardiomyopathy who were included in both the Pediatric Cardiomyopathy Registry and the Pediatric Heart Transplant Study. Median time to listing after diagnosis was 1.9 months and to transplant after listing was 0.8 months. There were 42 deaths (29 waiting and 13 within 6 months after transplant). We found a significant age-dependent association of LV end-diastolic dimension z score (n=204, 31 deaths) with death controlling for race, transplant status, and medical insurance. The association was strongest for infants younger than 6 months at diagnosis (hazard ratio 1.47, P=0.008) and was not significant in children older than 5 years at diagnosis. A similar interaction was identified between age and LV end-systolic dimension z score (P=0.04). Neither LV function nor mass was associated with death, overall, or in subgroups.The severity of LV dilation at listing for heart transplant is associated with outcome in infants and young children with dilated cardiomyopathy, whereas the severity of LV systolic dysfunction is not. These findings should be considered in risk stratification of these children at listing.
View details for DOI 10.1161/CIRCHEARTFAILURE.108.839001
View details for Web of Science ID 000271893100010
View details for PubMedID 19919984
Hypercholesterolemia impairs exercise capacity in mice
2009; 14 (3): 249-257
We previously reported an attenuation of both exercise hyperemia and measures of aerobic capacity in hypercholesterolemic mice. In this study, we expanded upon the previous findings by examining the temporal and quantitative relationship of hypercholesterolemia to aerobic and anaerobic capacity and by exploring several potential mechanisms of dysfunction. Eight-week-old wild type (n = 123) and apoE knockout (n = 79) C57BL/6J mice were divided into groups with distinct cholesterol levels by feeding with regular or high-fat diets. At various ages, the mice underwent treadmill ergospirometry. To explore mechanisms, aortic ring vasodilator function and nitrate (NO(x)) activity, urinary excretion of NO(x), running muscle microvascular density and citrate synthase activity, as well as myocardial mass and histologic evidence of ischemia were measured. At 8 weeks of age, all mice had similar measures of exercise capacity. All indices of aerobic exercise capacity progressively declined at 12 and 20 weeks of age in the hypercholesterolemic mice as cholesterol levels increased while indices of anaerobic capacity remained unaffected. Across the four cholesterol groups, the degree of aerobic dysfunction was related to serum cholesterol levels; a relationship that was maintained after correcting for confounding factors. Associated with the deterioration in exercise capacity was a decline in measures of nitric oxide-mediated vascular function while there was no evidence of aberrations in functional or oxidative capacities or in other components of transport capacity. In conclusion, aerobic exercise dysfunction is observed in murine models of genetic and diet-induced hypercholesterolemia and is associated with a reduction in vascular nitric oxide production.
View details for DOI 10.1177/1358863X08100040
View details for Web of Science ID 000268568300008
View details for PubMedID 19651675
Genotypic Variation and Phenotypic Characterization of Granzyme B Gene Polymorphisms
2009; 87 (12): 1801-1806
Granzyme B has been associated with allograft rejection in solid organ transplantation. Single nucleotide polymorphisms (SNPs) in the granzyme B gene might impact its expression. The aims of this study were (1) to establish the frequency of two granzyme B SNPs (A-295G; Q-55R) in pediatric heart transplant (PHTx) recipients and (2) to determine their phenotypic expression in healthy individuals.Three hundred ninety-six PHTx patients (245 white non-Hispanic, 49 black non-Hispanic, 82 Hispanics, and 20 others) and 52 healthy controls were screened for Q-55R and A-295G. For the control samples, we assessed the frequency of granzyme B positive cells by ELISPOT assay after mitogen stimulation.Among the PHTx recipients, 57% percent of the population carried the Q/Q genotype, whereas 6% were R/R homozygotes. Seven of 49 (14%) black non-Hispanics were R/R homozygotes, whereas 13 of 245 (5%) of white non-Hispanics and 5 of 82 (6%) Hispanics carried the R/R genotype (P=0.02). The A allele frequency of granzyme B A-295G (49.6%) was similar to that of the G allele (50.4%). However, 80% of Black non-Hispanics were A allele carriers compared with 68% of White non-Hispanics (P<0.0001). After mitogen stimulation, the frequency of granzyme B positive cells was higher in the Q/Q homozygotes compared with R/R carriers (P=0.006), whereas a similar frequency of granzyme B positive cells was noticed among the genotypes of A-295G SNP.These data indicate that 55 Q/Q genotype is associated with increased in vitro expression of granzyme B.
View details for DOI 10.1097/TP.0b013e3181a755a4
View details for Web of Science ID 000267361000007
View details for PubMedID 19543056
Molecular and physiological characterization of RV remodeling in a murine model of pulmonary stenosis
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2008; 295 (3): H1351-H1368
Right ventricular (RV) dysfunction is a common long-term complication in patients after the repair of congenital heart disease. Previous investigators have examined the cellular and molecular mechanisms of left ventricular (LV) remodeling, but little is known about the stressed RV. Our purpose was to provide a detailed physiological characterization of a model of RV hypertrophy and failure, including RV-LV interaction, and to compare gene alterations between afterloaded RV versus LV. Pulmonary artery constriction was performed in 86 mice. Mice with mild and moderate pulmonary stenosis (PS) developed stable hypertrophy without decompensation. Mice with severe PS developed edema, decreased RV function, and high mortality. Tissue Doppler imaging demonstrated septal dyssynchrony and deleterious RV-LV interaction in the severe PS group. Microarray analysis showed 196 genes with increased expression and 1,114 with decreased expression. Several transcripts were differentially increased in the afterloaded RV but not in the afterloaded LV, including clusterin, neuroblastoma suppression of tumorigenicity 1, Dkk3, Sfrp2, formin binding protein, annexin A7, and lysyl oxidase. We have characterized a murine model of RV hypertrophy and failure, providing a platform for studying the physiological and molecular events of RV remodeling. Although the molecular responses of the RV and LV to afterload stress are mostly concordant, there are several key differences, which may represent targets for RV failure-specific therapy.
View details for DOI 10.1152/ajpheart.91526.2007
View details for Web of Science ID 000258949200055
View details for PubMedID 18586894
Genetic polymorphisms impact the risk of acute rejection in pediatric heart transplantation: A multi-institutional study
2008; 85 (11): 1632-1639
The objective of this study was to determine the association between the genetic polymorphisms of proinflammatory and regulatory cytokines and long-term rates of repeat and late acute rejection episodes in pediatric heart transplant (PHTx) recipients.Three hundred twenty-three PHTx recipients: 205 White non-Hispanic, 43 Black non-Hispanic, and 75 Hispanic were analyzed for time to first repeat and late acute rejection episodes by race, age at transplantation, and gene polymorphism (interleukin [IL]-6, -174 G/C, IL-10, -1082 G/A, -819 C/T, 592 C/A; vascular endothelial growth factor (VEGF) -2578 C/A, -460 C/T, +405 C/G; tumor necrosis factor alpha (TNF-alpha)-308 G/A).Recipient black race and older age at transplant were risk factors for both repeat and late rejections, though black race was more significantly related to late rejection (P=0.006). Individually, TNF-alpha high, IL-6 high, VEGF high, and IL-10 low phenotypes did not impact the risk of repeat or late rejection. However, the combination VEGF high/IL-6 high and IL-10 low was associated with increased estimated risk of late rejection (P=0.0004) and only marginally with repeat rejection (P=0.051). In a multivariate analysis, adjusting for age and race, VEGF high/IL-6 high and IL-10 low still remained an independent risk factor for late acute rejection (RR=1.91, P<0.001).This is the largest multicenter study to document the impact of genetic polymorphism combinations on PHTx recipients' outcome. The high proinflammatory (VEGF high/IL-6 high) and lower regulatory (IL-10 low) cytokine gene polymorphism profile exhibited increased risk for late rejection, irrespective of age and race/ethnicity.
View details for DOI 10.1097/TP.0b013e3181722edc
View details for Web of Science ID 000256712900018
View details for PubMedID 18551071
Prevention of pediatric graft coronary artery disease: Atorvastatin
2008; 12 (4): 442-446
Graft coronary artery disease is a significant cause of late graft failure and death after cardiac transplantation. HMG-coenzyme A reductase inhibitors have been used safely in children but their preventative effects against GCAD are not well known. We investigated whether atorvastatin when initiated early could prevent against the development of pediatric GCAD. Pediatric patients (transplanted between October 28, 1992 and July 9, 2004) were stratified into two groups based on whether or not they received atorvastatin early after transplant. Angiograms were reviewed by a single observer blinded to the treatment strategies and clinical outcomes. Actuarial survival method and the Mantel-Cox test were used to assess statistical significance. Freedom from GCAD was higher among those treated with atorvastatin early in the post-transplant course. One, three, and five-yr freedom from GCAD was significantly greater in the early treatment group (97%, 93%, and 93% respectively) compared with the control group (72%, 65%, and 60% respectively, p < 0.005). The early treatment group was also noted for fewer rejection episodes in the first post-transplant year. The use of atorvastatin when initiated early in the post-transplant course appears protective against graft coronary artery disease.
View details for DOI 10.1111/j.1399-3046.2007.00827.x
View details for Web of Science ID 000255551700013
View details for PubMedID 18466431
Microsystems for biomechanical measurements
2008; 63 (5): 576-583
The use of microtechnology to make biomechanical measurements allows for the study of cellular and subcellular scale mechanical forces. Forces generated by cells are in the few nanoNewton to several microNewton range and can change spatially over subcellular size scales. Transducing forces at such small size and force scales is a challenging task. Methods of microfabrication developed in the integrated circuit industry have allowed researchers to build platforms with cellular and subcellular scale parts with which individual cells can interact. These parts act as transducers of stresses and forces generated by the cell during migration or in the maintenance of physical equilibrium. Due to the size and sensitivity of such devices, quantitative studies of single cell and even single molecule biomechanics have become possible. In this review we focus on two classes of cellular force transducers: silicon-based devices and soft-polymer platforms. We concentrate on the biomechanical discoveries made with these devices and less so on the engineering behind their development because this is covered in great detail elsewhere.
View details for Web of Science ID 000255311900018
View details for PubMedID 18427304
Gene expression profiling distinguishes a molecular signature for grade 1B mild acute cellular rejection in cardiac allograft recipients
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2007; 26 (12): 1270-1280
Gene expression profiling distinguishes the absence or presence of moderate to severe grades of acute cellular rejection in cardiac allograft recipients using a 20-gene classifier. We explored the hypothesis that the rejection classifier also differentiates various forms of mild rejection and we performed sub-analyses based on time post-transplant and confirmatory pathology interpretations.A post hoc analysis of 265 CARGO study patients and 714 clinical encounters focused on the correlation of rejection classifier-derived gene expression (GE) scores for blood samples accompanying endomyocardial biopsies. Biopsy grades assigned by a study center pathologist (center) were re-interpreted by three pathologists (panel) in a blinded manner.Mean GE scores not only differentiated Grades >or=3A from Grade 0 (p < 0.00001, center or panel), but also from Grades 1A or 2 (p < 0.05, center or panel), based on mild rejection sub-groups defined by the ISHLT 1990 grading system. In contrast, mean GE scores for Grades 1B and >or=3A were indistinguishable, using either center or panel interpretation. Sub-group analyses of encounters from 2 to 6 months or >6 months post-transplant showed similar results for the classifier's ability to discriminate moderate to severe rejection from Grades 1A and 2 mild rejection, but indistinguishable mean GE scores for Grades >or=3A and the Grade 1B sub-group. Of the classifier's 11 informative genes, expression of MIR and WDR40 showed statistically significant increases for both Grade 1B and Grade >or=3A rejection, while expression of PDCD1 or SEMA7A showed similar directional patterns without achieving statistical significance.These data demonstrate that GE scores discriminate moderate to severe rejection from Grades 1A and 2 mild rejection. However, a sub-group of mild rejection cases, defined as Grade 1B according to the 1990 grading system, share a molecular signature more consistent with moderate to severe rejection. The clinical relevance of these data remains to be defined.
View details for DOI 10.1016/j.healun.2007.09.017
View details for Web of Science ID 000251993500007
View details for PubMedID 18096478
Indications for heart transplantation in pediatric heart disease - A scientific statement from the American Heart Association Council on Cardiovascular Disease in the Young; the Councils on Clinical Cardiology, Cardiovascular Nursing, and Cardiovascular Surgery and Anesthesia; and the Quality of Care and Outcomes Research Interdisciplinary Working Group
2007; 115 (5): 658-676
Since the initial utilization of heart transplantation as therapy for end-stage pediatric heart disease, improvements have occurred in outcomes with heart transplantation and surgical therapies for congenital heart disease along with the application of medical therapies to pediatric heart failure that have improved outcomes in adults. These events justify a reevaluation of the indications for heart transplantation in congenital heart disease and other causes of pediatric heart failure.A working group was commissioned to review accumulated experience with pediatric heart transplantation and its use in patients with unrepaired and/or previously repaired or palliated congenital heart disease (children and adults), in patients with pediatric cardiomyopathies, and in pediatric patients with prior heart transplantation. Evidence-based guidelines for the indications for heart transplantation or retransplantation for these conditions were developed.This evaluation has led to the development and refinement of indications for heart transplantation for patients with congenital heart disease and pediatric cardiomyopathies in addition to indications for pediatric heart retransplantation.
View details for DOI 10.1161/CIRCULATIONAHA.106.180449
View details for Web of Science ID 000244000800018
View details for PubMedID 17261651
Disparate distribution of 16 candidate single nucleotide polymorphisms among racial and ethnic groups of pediatric heart transplant patients
2006; 82 (12): 1774-1780
Allograft failure in African-Americans remains higher than in Caucasians. Single nucleotide polymorphisms (SNPs) have been associated with altered allograft outcomes.In this multi-center study we compared SNP frequencies in 364 pediatric heart recipients from three ethnic/racial groups: Caucasian (n = 243), African-American (n = 39), and Hispanic (n = 82). The target genes were: tumor necrosis factor-alpha, interleukin (IL)-10, IL-6, interferon (IFN)-gamma, vascular endothelial growth factor (VEGF), transforming growth factor-beta1, Fas, FasL, granzyme B, ABCB1, CYP3A5.Compared to Caucasians, African-Americans exhibited a higher prevalence of genotypes associated with low expression of IFN-gamma (24% vs. 45.7%, P < 0.001) and IL-10 (33% vs. 57.1%, P = 0.052). African-Americans also exhibited an increased prevalence of high IL-6 (82.9% vs. 38.1%; P < 0.001). VEGF -2578 C/C and -460 C/C genotypes were found more frequently in African-Americans and Hispanics as compared to Caucasians (P < 0.001). G/G genotype of Fas and T/T genotype of FasL were expressed more often by African-American recipients. The prevalence of Granzyme B (-295A/G) genotype was differentially distributed in the three groups. Compared with Caucasians, African-Americans were twice as likely to carry the ABCB1 2677 G/G genotype (78.6% vs. 33.7%, P < 0.0025), and they were more frequent carriers of the CYP3A5 *1/*1 genotype (35.7% vs. 0.6% in Caucasians and 7.2% in Hispanics; P < 0.001).African-Americans have a genetic background that may predispose to proinflammatory/lower regulatory environment, reduced drug exposure and immunosuppressive efficacy. In this ongoing multicenter study, these gene polymorphisms differences among ethnic/racial groups are being documented so that therapeutic strategies can be devised to optimize outcomes for pediatric transplant recipients.
View details for DOI 10.1097/01.tp.0000250656.33731.08
View details for Web of Science ID 000243178200046
View details for PubMedID 17198275
Pediatric cardiac transplantation.
Seminars in pediatric surgery
2006; 15 (3): 188-198
Pediatric heart transplantation has undergone major changes over the past two decades, marked by a substantial improvement in survival, reduction in posttransplant complications, and enhancement in quality of life for transplant recipients. Actuarial survival has improved substantially in the last decade. Indications for pediatric heart transplant have changed as surgery for complex congenital heart lesions has evolved. There are now left and right ventricular assist devices that are suitable for use in infants as a bridge to transplantation. New immunosuppressive agents have reduced the risk of rejection while minimizing side effects and strategies to reduce the risk of graft coronary disease are beginning to show promise. Finally, true long-term survival for children after heart transplant has now been demonstrated and quality of life is excellent.
View details for PubMedID 16818140
Outcome of listing for cardiac transplantation for failed Fontan - A multi-institutional study
2006; 114 (4): 273-280
The Fontan procedure is a successful palliation for children with single-ventricle physiology; however, many will eventually require heart transplantation. The purpose of this study was to determine risk factors for death awaiting transplantation and to examine results after transplantation in Fontan patients.A retrospective, multi-institutional review was performed of 97 Fontan patients <18 years of age listed at 17 Pediatric Heart Transplant Study centers from 1993 to 2001. Mean age at listing was 9.7 years (0.5 to 17.9 years); 25% were <4 years old; 53% were United Network for Organ Sharing status 1; 18% required ventilator support. Pretransplantation survival was 78% at 6 months and 74% at 12 months and was similar to 243 children with other congenital heart disease (CHD) and 747 children without congenital heart disease (No-CHD), who were also awaiting transplantation. Patients who were younger, status 1, had shorter interval since Fontan, or were on a ventilator were more likely to die while waiting. At 6 months, the probability of receiving a transplant was similar for status 1 and 2 (65% versus 68%); however, the probability of death was higher for status 1 (22% versus 5%). Seventy patients underwent transplantation. Survival was 76% at 1 year, 70% at 3 years, and 68% at 5 years, slightly less than CHD and No-CHD patients. Causes of death included infection (30%), graft failure (17%), rejection (13%), sudden death (13%), and graft coronary artery disease (9%). Protein-losing enteropathy (present in 34 patients) resolved in all who survived >30 days after transplantation.Heart transplantation is an effective therapy for pediatric patients with a failed Fontan. Although early posttransplantation survival is slightly lower than other patients with CHD, long-term results are encouraging, and protein-losing enteropathy can be expected to resolve.
View details for DOI 10.1161/CIRCULATIONAHA.105.548016
View details for Web of Science ID 000239237200007
View details for PubMedID 16847155
Neurologic events in neonates treated surgically for congenital heart disease
JOURNAL OF PERINATOLOGY
2006; 26 (4): 237-242
The incidence of acute neurologic events prior to discharge in neonates with congenital heart disease (CHD) was determined and peri-operative characteristics predictive of a neurologic event were identified.A retrospective chart review over 1 year was conducted of infants <1 month of age with a diagnosis of CHD. Outcomes were measured by the occurrence of an acute neurologic event defined as electroencephalogram (EEG)-proven seizure activity, significant hypertonia or hypotonia, or choreoathetosis prior to hospital discharge. Stepwise logistic regression identified variables most likely to be associated with an acute neurologic event.Surgical intervention occurred in 95 infants who were admitted with a diagnosis of CHD. The survival rate was 92%. Of the survivors, 16 (17%) had an acute neurologic event, with 19% of events occurring preoperatively. Factors associated with neurologic events included an elevated nucleated red blood cell (NRBC) count, an abnormal preoperative brain imaging study, and a 5-min Apgar score <7 (P<0.05).Neonates with CHD have a significant risk of neurologic events. Preoperative brain imaging, the 5-min Apgar score, and initial serum NRBC counts may identify infants at highest risk for central nervous system injury.
View details for DOI 10.1038/sj.jp.7211459
View details for Web of Science ID 000241843200006
View details for PubMedID 16496014
Differential cardiotoxic/cardioprotective effects of beta-adrenergic receptor subtypes in myocytes and fibroblasts in doxorubicin cardiomyopathy
JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY
2006; 40 (3): 375-383
beta-Adrenoceptor (beta-AR) subtypes act through different signaling pathways to regulate cardiac function and remodeling. Previous in vivo data show a markedly enhanced cardiotoxic response to doxorubicin in beta2-/- mice, which is rescued by the additional deletion of the beta1-AR. We determined whether this differential response was myocyte specific by examining the effects of doxorubicin in myocytes and fibroblasts from WT and beta1, beta2 and beta1/beta2-/- mice. Cells were exposed to doxorubicin at 1-50 microM and viability and apoptosis assessed at 6, 24 and 48 h. WT myocytes showed a time and dose-dependent decrease in viability (42% decrease at 1 microM after 24 h). beta2-/- Myocytes showed a greater decrease in viability vs. WT (20.8% less at 6 h; 14% less at 24 h, P<0.05); beta1-/- and beta1/beta2-/- myocytes showed enhanced survival (beta1-/- 11%; beta1/beta2-/- 18% greater than WT, P<0.05). TUNEL staining demonstrated a similar differential susceptibility (WT 26% apoptotic nuclei, beta2-/- 45.9%, beta1/beta2-/- 16.8%, P<0.05). beta2-/- Fibroblasts also showed enhanced toxicity. Pertussis toxin pretreatment of WT cells decreased survival similar to the beta2-/-, suggesting a role for Gi signaling. JNK was differentially activated in beta2-/- myocytes after doxorubicin and its inhibition increased cardiotoxicity. In conclusion, the differential cardioprotective/cardiotoxic effects mediated by beta1 vs. beta2-AR subtypes in knockout mice are recapitulated in myocytes isolated from these mice. beta2-ARs appear to play a cardioprotective role, whereas beta1-ARs a cardiotoxic role.
View details for DOI 10.1016/j.yjmcc.2005.12.004
View details for Web of Science ID 000236059300006
View details for PubMedID 16458323
Ten- and 20-year survivors of pediatric orthotopic heart transplantation
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2006; 25 (3): 261-270
Pediatric heart transplantation is entering its third decade, allowing for the first time an analysis of a large group of true long-term survivors, specifically children who have survived > or =10 years post-transplantation.Fifty-two patients < or =18 years, who had undergone heart transplantation at Stanford between August 1974 and June 1993 and survived > or =10 years, were retrospectively reviewed.Forty (77%) patients are currently alive. Thirteen survived >15 years and 5 >20 years (the longest being 26 years). Actuarial survival was 79.4% at 14 years and 53.1% at 20 years. Cardiomyopathy was the reason for transplantation in 71% and congenital heart disease (CHD) in 29%. At last evaluation, 71% were on a cyclosporine-based regimen and 23% a tacrolimus-based regimen; 33% were steroid-free. Twenty-seven percent were totally free from treatable rejection, 44% developed serious infections, 69% were receiving anti-hypertensives, and 8% required renal transplantation. Neoplasms occurred in 23%, graft coronary artery disease (CAD) in 31%, and 15% required re-transplantation. Of the 12 deaths, CAD was the most common cause (n = 4), followed by non-specific late graft failure (n = 3), infection (n = 2), rejection (n = 1), non-lymphoid cancer (n = 1) and lymphoid cancer (n = 1). Physical rehabilitation and return to normal lifestyle has been nearly 100%.Heart transplantation in pediatric patients is compatible with true long-term survival with a growing cohort of children approaching their second and third decades. The gradual constant-phase decrease in survival noted in earlier studies appears to be continuing. Rejection and infection are low but persistent risks after the first years. Graft CAD and non-specific late graft dysfunction are the leading causes of death after 10 years. Rehabilitation is excellent.
View details for DOI 10.1016/j.healun.2005.09.011
View details for Web of Science ID 000235946000001
View details for PubMedID 16507417
Effect of targeted deletions of beta(1)- and beta(2)-adrenergic-receptor subtypes on heart rate variability
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2006; 290 (1): H192-H199
Beta-adrenergic receptors (beta-ARs) play a major role in regulating heart rate (HR) and contractility in the intact cardiovascular system. Three subtypes (beta1, beta2, and beta3) are expressed in heart tissue, and the role of each subtype in regulating cardiac function has previously been determined by using both pharmacological and gene-targeting approaches. However, previous studies have only examined the role of beta-ARs in the macrolevel regulation of HR. We employed three knockout (KO) mouse lines, beta1-KO, beta2-KO, and beta1/beta2 double KO (DL-KO), to examine the role that beta-AR subtypes play in HR variability (HRV) and in the sympathetic and parasympathetic inputs into HR control. Fast Fourier transformation (FFT) in frequency domain methods of ECG spectral analysis was used to resolve HRV into high- and low-frequency (HF and LF) powers. Resting HR (in beats/min) was decreased in beta1-KO [488 (SD 27)] and DL-KO [495 (SD 12)] mice compared with wild-type [WT; 638 (SD 30)] or beta2-KO [656 (SD 51)] (P < 0.0005) mice. Mice lacking beta1-ARs (beta1-KO and DL-KO) had increased HRV (as illustrated by the standard deviation of normal R-R intervals) and increased normalized HF and LF powers compared with mice with intact beta1-ARs (WT and beta2-KO). These results demonstrate the differential role of beta-AR subtypes in regulating autonomic signaling.
View details for DOI 10.1152/ajpheart.00032.2005
View details for Web of Science ID 000234148200023
View details for PubMedID 16113068
Differential cardioprotective/cardiotoxic effects mediated by ss-adrenergic receptor subtypes
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2005; 289 (6): H2441-H2449
Recent data suggest that beta-adrenergic receptor subtypes couple differentially to signaling pathways regulating cardiac function vs. cardiac remodeling. To dissect the roles of beta1- vs. beta2-receptors in the pathogenesis of cardiomyopathy, doxorubicin was administered to beta1, beta2, and beta1/beta2 knockout (-/-) and wild-type mice. Expression and activation of MAPKs were measured. Wild-type and beta1-/- mice showed no acute cardiovascular effects, whereas beta2-/- mice all died within 30 min. The additional deletion of the beta1-receptor (beta1/beta2-/-) totally rescued this toxicity. beta2-/- mice developed decreased contractile function, hypotension, QTc prolongation, and ST segment changes and a 20-fold increase in p38 MAPK activity not seen in the other genotypes. The MAPK inhibitor SB-203580 rescued beta2-/- mice from this acute toxicity. The enhanced toxicity in beta2-/- mice was also recapitulated in wild-type mice with the beta2-selective antagonist ICI-118,551, although the rescue effect of the beta1-deletion was not recapitulated using the beta1-selective antagonist metoprolol or the nonselective beta-antagonist propranolol. These data suggest that beta2-adrenergic receptors play a cardioprotective role in the pathogenesis of cardiomyopathy, whereas beta1-adrenergic receptors mediate at least some of the acute cardiotoxicity of anthracyclines. Differential activation of MAPK isoforms, previously shown in vitro to regulate beta-agonist as well as doxorubicin cardiotoxicity, appears to play a role in mediating the differential effects of these beta-adrenergic receptor subtypes in vivo.
View details for DOI 10.1152/ajpheart.00005.2005
View details for Web of Science ID 000233176600023
View details for PubMedID 16040722
Increased fibulin-5 and elastin in S100A4/Mts1 mice with pulmonary hypertension
2005; 97 (6): 596-604
Transgenic mice overexpressing the calcium binding protein, S100A4/Mts1, occasionally develop severe pulmonary vascular obstructive disease. To understand what underlies this propensity, we compared the pulmonary vascular hemodynamic and structural features of S100A4/Mts1 with control C57Bl/6 mice at baseline, following a 2-week exposure to chronic hypoxia, and after 1 and 3 months "recovery" in room air. S100A4/Mts1 mice had greater right ventricular systolic pressure and right ventricular hypertrophy at baseline, which increased further with chronic hypoxia and was sustained after 3 months "recovery" in room air. These findings correlated with a heightened response to acute hypoxia and failure to vasodilate with nitric oxide or oxygen. S100A4/Mts1 mice, when compared with C57Bl/6 mice, also had impaired cardiac function judged by reduced ventricular elastance and decreased cardiac output. Despite higher right ventricular systolic pressures with chronic hypoxia, S100A4/Mts1 mice did not develop more severe PVD, but in contrast to C57Bl/6 mice, these features did not regress on return to room air. Microarray analysis of lung tissue identified a number of genes differentially upregulated in S100A4/Mts1 versus control mice. One of these, fibulin-5, is a matrix component necessary for normal elastin fiber assembly. Fibulin-5 was localized to pulmonary arteries and associated with thickened elastic laminae. This feature could underlie attenuation of pulmonary vascular changes in response to elevated pressure, as well as impaired reversibility.
View details for DOI 10.1161/01.RES.00000182425.49768.8a
View details for Web of Science ID 000231896500013
View details for PubMedID 16109920
Induction therapy for pediatric and adult heart transplantation: Comparison between OKT3 and daclizumab
2005; 80 (4): 477-481
Induction therapy can reduce morbidity and early mortality in pediatric and adult heart transplant recipients. Monoclonal and polyclonal agents are most widely used; they nonspecifically deplete the T-cell pool and are thus associated with drug-induced side effects. The cytokine release syndrome is one of the most problematic events associated with induction. Daclizumab, a highly humanized, specific interleukin-2 receptor blocker, may be efficacious to the monoclonal agent, OKT3. Due to its specific action and properties, the safety profile of this agent may be superior to OKT3.Forty subjects received daclizumab and their clinical outcomes were compared against a historical group of 40 subjects who received OKT3. Three- and six-month outcome measures included survival, rejection history, steroid burden, and complications.Mortality was low between the groups with equivalent 6-month survival. No differences in rejection profile or time to the first significant rejection event were detected; no subject had severe acute rejection within the first 180 days. Steroid requirement for maintenance immunosuppression and treatment of rejection was also similar between the groups. Six-month prevalence for complications were significantly different; 55% of OKT3-treated subjects having at least one event compared to 33% of daclizumab-treated subjects (P=0.04). The likelihood of complications occurred within the first month after transplantation.Daclizumab induction therapy is as efficacious as OKT3 in the prevention of early acute rejection after heart transplantation among pediatric and adult subjects. Complications related to the induction agent are significantly lower in the humanized product.
View details for DOI 10.1097/01.tp.0000168153.50774.30
View details for Web of Science ID 000231566800008
View details for PubMedID 16123721
Experience of percutaneous coronary intervention in the management of pediatric cardiac allograft vasculopathy
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2005; 24 (6): 769-773
In a retrospective study, we examined the procedural success rate and the short-, intermediate-, and long-term outcomes of coronary interventional procedures in children with cardiac allograft vasculopathy. Seven patients underwent 13 interventional procedures: balloon angioplasty alone (n = 3), angioplasty with stenting (n = 9), or angioplasty with brachytherapy (n = 1), with procedural success in all. Two major complications (cardiac arrest) and a single death occurred in the immediate postprocedural period. Five (83%) of the remaining 6 patients developed moderate to severe restenosis, diffuse disease, or progressive vasculopathy; 3 have been retransplanted, 1 died from progressive cardiac allograft vasculopathy, and 1 is awaiting retransplantation, 40 months after the procedure.
View details for DOI 10.1016/j.healun.2004.04.009
View details for Web of Science ID 000229869700018
View details for PubMedID 15949739
The role of beta-adrenergic receptor signaling in cardioprotection.
2005; 19 (8): 983-985
This study examines the role of the beta2-adrenergic receptor (beta2-AR) in cardioprotection. The beta2-AR couples to Gs and Gi proteins. Gs activates PKA, which phosphorylates the receptor and switches beta2-AR coupling from Gs to Gi. Prior to 20 min of global ischemia, mouse hearts were either perfused for 30 min without treatment (control), treated with 10 nmol/L of isoproterenol (ISO) for 5 min followed by 5 min washout, or preconditioned with 4 cycles of 5 min ischemia and 5 min reflow (PC). Recovery of left ventricular developed pressure (LVDP) and infarct size were measured. Intermittent ISO treatment improved post-ischemic recovery of LVDP (58.5+/-4.8% vs. 22.0+/-6.3% in control) and reduced infarct size (31.0+/-2.4% vs. 53.0+/-4.6% in control). The Gi inhibitor pertussis toxin blocked the ISO-induced improvement in postischemic LVDP and infarct size. To test the role of beta2-AR in PC, we studied mice lacking beta2-AR (beta2-AR-/-) and found that PC had no effect on postischemic LVDP or infarct size in beta2-AR-/-. To test whether PKA is required for the PC and ISO-induced protection, hearts were treated with the PKA inhibitors PKI and H-89. We found that PKI and H-89 blocked the PC- and ISO-induced improvement in postischemic LVDP and infarct size. These data show an important role for beta2-AR in cardioprotection and support the novel hypothesis that preconditioning involves switching of beta2-AR coupling from Gs to Gi.
View details for PubMedID 15802488
- The role of beta-adrenergic receptor signaling in cardioprotection FASEB JOURNAL 2005; 19 (3): 983-?
The endogenous peptide apelin potently improves cardiac contractility and reduces cardiac loading in vivo
2005; 65 (1): 73-82
The endogenous peptide apelin is differentially regulated in cardiovascular disease but the nature of its role in cardiac function remains unclear.We investigated the functional relevance of this peptide using ECG and respiration gated magnetic resonance imaging, conductance catheter pressure-volume hemodynamic measurements, and echocardiography in vivo. In addition, we carried out histology and immunohistochemistry to assess cardiac hypertrophy and to localize apelin and APJ in the adult and embryonic mouse heart.Intraperitoneal injection of apelin (300 microg/kg) resulted in a decrease in left ventricular end diastolic area (pre: 0.122+/-0.007; post: 0.104+/-0.005 cm(2), p=0.006) and an increase in heart rate (pre: 537+/-20; post: 559+/-19 beats per minute, p=0.03). Hemodynamic measurements revealed a marked increase in ventricular elastance (pre: 3.7+/-0.9; post: 6.5+/-1.4 mm Hg/RVU, p=0.018) and preload recruitable stroke work (pre: 27.4+/-8.0; post: 51.8+/-3.1, p=0.059) with little change in diastolic parameters following acute infusion of apelin. Chronic infusion (2 mg/kg/day) resulted in significant increases in the velocity of circumferential shortening (baseline: 5.36+/-0.401; 14 days: 6.85+/-0.358 circ/s, p=0.049) and cardiac output (baseline: 0.142+/-0.019; 14 days: 0.25+/-0.019 l/min, p=0.001) as determined by 15 MHz echocardiography. Post-mortem corrected heart weights were not different between apelin and saline groups (p=0.5) and histology revealed no evidence of cellular hypertrophy in the apelin group (nuclei per unit area, p=0.9). Immunohistochemistry studies revealed APJ staining of myocardial cells in all regions of the adult mouse heart. Antibody staining, as well as quantitative real time polymerase chain reaction identified expression of both APJ and apelin in embryonic myocardium as early as embryonic day 13.5.Apelin reduces left ventricular preload and afterload and increases contractile reserve without evidence of hypertrophy. These results associate apelin with a positive hemodynamic profile and suggest it as an attractive target for pharmacotherapy in the setting of heart failure.
View details for DOI 10.1016/j.cardiores.2004.08.018
View details for Web of Science ID 000226477600011
View details for PubMedID 15621035
Pharmacotherapy of hyperlipidemia in pediatric heart transplant recipients: current practice and future directions.
2005; 7 (6): 391-396
Lipoprotein abnormalities are fairly common after pediatric heart transplantation. Graft coronary artery disease (GCAD) limits long-term survival and has been linked to elevated serum triglyceride levels and decreased high-density lipoprotein levels. Histologically, GCAD represents intimal hyperplasia of the coronary vessel and is best imaged by intravascular ultrasound.A number of pharmacologic agents are available for the management of lipid disorders but experience with these drugs has mainly been in adults. HMG-CoA reductase inhibitors (statins) are currently used by many adult transplantation centers to alter lipid profiles in the hope of reducing GCAD. The use of statins among pediatric heart transplant centers is more limited. Although rhabdomyolysis is a concern with these agents, the incidence among individuals receiving immunosuppressant therapy is low. Aside from their lipid-lowering properties, statins may also protect against graft failure and rejection.
View details for PubMedID 16356026
Genome-wide expression profiling of a cardiac pressure overload model identifies major metabolic and signaling pathway responses
JOURNAL OF MOLECULAR AND CELLULAR CARDIOLOGY
2004; 37 (6): 1159-1170
Cardiac hypertrophy is a predictor of cardiovascular morbidity and mortality independent of other risk factors. Pressure overload induces the development of left ventricular hypertrophy (LVH) and left atrial enlargement (LAE) in the mammalian heart. To systematically investigate the transcriptional changes, which mediate these processes, we have performed a genome-wide transcriptional profiling of each of the four heart chambers from mice subjected to transverse aortic constriction (TAC). A major new finding of this analysis is that during enlargement the left atrium undergoes radical changes in gene transcription that may play a significant role in pathophysiology. Structural changes in the LA and LV are correlated with significant changes in the transcriptional profile of these chambers, with thousands of differentially expressed known and novel factors. Statistical analysis of the results identified Gene Ontology biological process groups with significant group-wide changes, including angiogenesis, energy pathways, fatty acid oxidation, oxidative phosphorylation, cytoskeletal and matrix reorganization, and G-protein coupled receptor (GPCR) signaling. To facilitate future research, a searchable annotated Internet database has been constructed that allows access to the expression data presented here. Further study of these genes and processes will lead to better understanding of pathways involved in the pathophysiology of the cardiac response to pressure overload.
View details for DOI 10.1016/j.yjmcc.2004.09.003
View details for Web of Science ID 000225905300007
View details for PubMedID 15572046
- International society for heart and lung transplantation: Practice guidelines for management of heart failure in children JOURNAL OF HEART AND LUNG TRANSPLANTATION 2004; 23 (12): 1313-1333
The mouse as a model of cardiovascular adaptations to microgravity
JOURNAL OF APPLIED PHYSIOLOGY
2004; 97 (5): 1686-1692
There are a multitude of physiological adaptations to microgravity, involving the cardiovascular, neuromuscular, and neuroendocrine systems. Some of these adaptations lead to cardiovascular deconditioning on return to normal gravity, posing a threat to human functional integrity after long-term spaceflight. Animal models of microgravity, e.g., tail suspension in rats, have yielded important information regarding the mechanism of these adaptations and have been useful in the design of countermeasures. The mouse could potentially be a useful experimental model, given its small size (smaller and lighter payload) and the powerful tools of experimental mouse genetics, which allow us to dissect mechanisms on a gene-specific basis. We show that the mouse demonstrates a wide range of cardiovascular responses to simulated microgravity, including alterations in heart rate, exercise capacity, peripheral arterial vasodilatory responsiveness, and baroreflex response. These responses are qualitatively similar to many of those demonstrated in humans during spaceflight and in rats using tail suspension, although there are some important differences. Thus the mouse has value as a model for studies of cardiovascular changes during microgravity; however, investigators must maintain an appreciation of important species differences.
View details for DOI 10.1152/japplphysiol.00925.2003
View details for Web of Science ID 000224361700020
View details for PubMedID 15258130
Microarray analysis of gene expression after transverse aortic constriction in mice
2004; 19 (1): 93-105
Cardiac hypertrophy is a compensatory response initially beneficial to heart function but can ultimately lead to cardiac decompensation. It is an integrated process involving multiple cellular signaling pathways and their cross talk. Microarray GeneChip technology is a powerful new tool to identify gene expression profiles of cardiac hypertrophy. To identify well-characterized as well as novel adaptive mechanisms, we utilized a murine model of compensated pressure overload hypertrophy (transverse aortic constriction, TAC). At 48 h, 10 days, and 3 wk, hearts were harvested and total RNA hybridized to Affymetrix U74Av2 GeneChips, which contain a 12,488-gene/EST probe set. Verification of gene expression was performed by SYBR quantitative real-time RT-PCR (QRT-PCR) for selected genes. A rigorous evaluation of the adequacy of the control condition was also performed. For statistical analysis we generated a four-step filtering criteria. Our results show an upregulation of 38 genes (48 h), 269 genes (10 days), and 203 genes (3 wk) and downregulation of 15 genes (48 h), 160 genes (10 days), and 124 genes (3 wk). Transcripts differentially expressed after TAC were categorized into 12 functional groups and revealed the presence of several intriguing transcripts, e.g., cell proliferation-related Ki-67 and several apoptosis-related genes. Overall changes in QRT-PCR were in accordance with GeneChip data, with the highest correlation for genes with the largest up- or downregulation with TAC. Thus TAC results in altered expression of genes in several pathways regulating both cardiac structure and function. However, for in vivo gene microarray experiments, it is critical to define adequate controls, perform rigorous statistical analysis, and provide validation by alternative methods.
View details for DOI 10.1152/physiolgenomics.00040.2004
View details for Web of Science ID 000224259700010
View details for PubMedID 15292486
- Linearity versus cross-talk: Biological models and the role of the society for pediatric research in the 21st century PEDIATRIC RESEARCH 2004; 56 (2): 177-183
Identifying cardiac transplant rejection in children: Diagnostic utility of echocardiography, right heart catheterization and endomyocardial biopsy data
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2004; 23 (3): 323-329
There has been a continued search for alternative diagnostic techniques that do not necessitate endomyocardial biopsy for diagnosing rejection in cardiac transplant recipients. The purpose of this study is to evaluate the role of echocardiography and hemodynamic catheterization data compared with endomyocardial biopsy results, in rejection surveillance for the pediatric heart transplant recipient.A prospective, blinded evaluation was performed utilizing echocardiographic and standard right heart catheterization parameters to predict acute rejection episodes.Forty-nine patients underwent 281 biopsies. Two groups were defined: those with Grade <2 rejection and those with grade > or =2 rejection. None of the echocardiographic variables showed significant differences between the study groups and all group data were within normal limits. Mixed venous saturation, mean right atrial pressure, right ventricular end-diastolic pressure and mean pulmonary artery pressure were found to be statistically significant between groups. Receiver-operator characteristic (ROC) curves were constructed to determine the extent to which the various parameters were clinically useful. The ROC found little clinical usefulness for all variables, including those found to be statistically significant.Differences in both echocardiographic and hemodynamic data were not clinically significant between the 2 groups of patients. Although many of the catheterization-derived parameters were statistically significant, they did not permit effective discrimination between groups. This is the only clinically relevant application of such data and may explain the conflicting previous reports. It is only through analyses such as ROC that the clinical application (or lack thereof) can be appreciated in this population.
View details for DOI 10.1016/S1053-2498(03)00209-2
View details for Web of Science ID 000220155700009
View details for PubMedID 15019642
Risk factors for recurrent rejection in pediatric heart transplantation: A multicenter experience
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2004; 23 (2): 178-185
Cardiac allograft rejection remains as a primary cause of death in the first 3 years after pediatric heart transplantation. Multiple episode of acute rejection in adult heart transplant recipients may accelerate the development of graft vasculopathy. We sought to quantify the time-related probability of recurrent rejection and identify risk factors for the development of recurrent rejection.We analyzed data from 847 pediatric recipients who underwent transplantation between January 1, 1993 and December 31, 1998 at 22 centers in the Pediatric Heart Transplant Study (PHTS). Recurrent rejection and risk factors were evaluated using univariate and multivariate analyses.Five hundred fifty two patients had 1,072 rejection events and were the subject of the analyses. The highest risk of recurrent rejection occurs within 1 month after resolution of a previous rejection episode. Risk factors for recurrent rejection include the number of previous rejection events, the elapsed time since a previous rejection episode, and subjects of either Hispanic or African-American descent. Rejection associated with hemodynamic compromise and late rejection is associated with higher mortality.Recurrent rejection is a risk factor for mortality, especially in the presence of hemodynamic compromise. This association appears independent of the time post-transplantation. Use of surveillance biopsies appears warranted throughout the life of the transplant individual. Retransplantation should be considered among these subjects with recurrent rejection.
View details for DOI 10.1016/S1053-2498(03)00059-7
View details for Web of Science ID 000188759100004
View details for PubMedID 14761765
Atrial tachyarrhythmias and permanent pacing after pediatric heart transplantation
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2003; 22 (10): 1126-1133
Atrial tachyarrhythmias have been reported in as high as 50% of adult heart recipients. Limited information is available on arrhythmias in pediatric transplant patients. Our objective was to determine the prevalence and significance of atrial tachyarrhythmias and permanent pacing following pediatric heart transplantation.A retrospective review of the medical records, electrocardiograms, and Holter recordings of all consecutive patients following heart transplantation at Children's Hospital, Boston (n = 104) and Lucile Packard Children's Hospital, Stanford (n = 123) was performed. The study group consisted of 227 patients with a median age at transplant of 10.2 yrs (1 day-23.3 yrs).Atrial tachyarrhythmias occurred in 32 patients (14%) at a median of 15 days post-transplant (1 day-9.2 yrs) and included atrial flutter (n = 13), atrial fibrillation (n = 7), ectopic atrial tachycardia (n = 5), atrioventricular reciprocating tachycardia or atrioventricular node reentry (n = 5), and other (n = 2). Atrial flutter was the only tachyarrhythmia associated with allograft rejection (6/13 atrial flutter vs. 0/7 atrial fibrillation vs. 0/5 ectopic atrial tachycardia, p = 0.03). Patients with atrial fibrillation had a 2.5 fold (95%CI 1.7-3.5) higher risk of death or retransplant compared to patients without atrial fibrillation. Ectopic atrial tachycardia tended to occur in younger recipients compared to atrial fibrillation and flutter (2.7 yrs vs 18.6 yrs and 8.5 yrs respectively, p = 0.06) and was associated with a benign clinical course. There was no association between atrial tachyarrhythmias and graft ischemic time, surgical technique, or coronary artery disease. Pacemakers were required in 12 patients (5.2%), 7 with sinus node dysfunction and 5 for intermittent complete atrioventricular block. There was no consistent association between the need for permanent pacing and coronary artery disease, rejection, or surgical technique.Atrial tachyarrhythmias and permanent pacing were uncommon in this cohort of pediatric heart transplant recipients. Association with cardiac rejection, clinical course, and mortality varied depending on the tachyarrhythmia mechanism.
View details for DOI 10.1016/S1053-2498(02)01193-2
View details for Web of Science ID 000185764400007
View details for PubMedID 14550822
Exercise assessment of transgenic models of human cardiovascular disease
2003; 13 (3): 217-226
Exercise provides one of the most severe, yet physiological, stresses to the intact cardiovascular system and is a major determinant of the utilization of metabolic substrates. The adaptations to exercise are the result of a coordinated response of multiple organ systems, including cardiovascular, pulmonary, endocrine-metabolic, immunologic, and skeletal muscle. With the proliferation of genetically altered murine models of cardiovascular disease, the importance of developing methods of accurate physiological phenotyping is critical. There are numerous examples of transgenic models in which the baseline cardiovascular phenotype is unchanged or minimally changed from the wild type, only to become manifest during the stress of exercise testing. In this review, we cover the basics of the murine cardiovascular response to exercise and the importance of attending to strain differences, compare different exercise methodologies (constant workload treadmill, incremental workload treadmill, swimming) and hemodynamic monitoring systems, and examine the murine response to exercise conditioning. Several examples where exercise studies have contributed to the elucidation of cardiovascular phenotypes are reviewed: the beta-adrenergic receptor knockouts, phospholamban knockout, dystrophin knockout (mdx), and the mutant alpha-myosin heavy chain (R403Q) transgenic.
View details for DOI 10.1152/physiolgenomics.00188.2002
View details for Web of Science ID 000182853000005
View details for PubMedID 12746466
Efficacy and safety of atorvastatin after pediatric heart transplantation
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2002; 21 (11): 1213-1217
Lipid abnormalities are prevalent after pediatric and adult heart transplantation. 3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors are efficacious and safe and can lower the incidence of graft coronary artery disease after heart transplantation in adults. Given the high prevalence of lipid abnormalities and the increased recognition of graft coronary disease in children, we retrospectively investigated the efficacy and safety of atorvastatin among pediatric heart transplant recipients.Thirty-eight patients were started on atorvastatin 48.2 +/- 54.4 months after transplantation. Atorvastatin dosage was 0.2 +/- 0.1 mg/kg per day. No patient had changes in drug dose unless there was evidence for rhabdomyolysis, myositis or an asymptomatic rise in creatine kinase above normal. Laboratory studies included total cholesterol, triglycerides; high, low and very low-density lipoproteins (HDL, LDL and VLDL, respectively); creatine kinase; creatine; and serum alanine transaminase.Significant declines in total cholesterol (20%), triglyceride (18%) and LDL (26%) were observed after starting atorvastatin therapy. There were no significant changes in HDL or VLDL compared with baseline. There were also no differences in alanine transaminase pre- vs post-atorvastatin therapy. Complications included muscle pain (n = 2) and asymptomatic elevations in creatine kinase (n = 2). Two of these 4 patients developed rhabdomyolysis. Excluding these 4 patients, creatine kinase did not rise compared with baseline. No patient developed alterations in renal function.Use of atorvastatin in pediatric heart transplant recipients is effective in lowering total cholesterol, triglyceride and LDL without altering HDL levels. Complications included rhabdomyolysis, seen in 5%. Baseline and routine screening of creatine kinase should be employed in all pediatric patients undergoing HMG-CoA reductase inhibitor therapy.
View details for Web of Science ID 000179183900006
View details for PubMedID 12431495
Abnormal cardiac function associated with sympathetic nervous system hyperactivity in mice
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
2002; 283 (5): H1838-H1845
alpha(2A)-Adrenergic receptors (ARs) in the midbrain regulate sympathetic nervous system activity, and both alpha(2A)-ARs and alpha(2C)-ARs regulate catecholamine release from sympathetic nerve terminals in cardiac tissue. Disruption of both alpha(2A)- and alpha(2C)-ARs in mice leads to chronically elevated sympathetic tone and decreased cardiac function by 4 mo of age. These knockout mice have increased mortality, reduced exercise capacity, decreased peak oxygen uptake, and decreased cardiac contractility relative to wild-type controls. Moreover, we observed significant abnormalities in the ultrastructure of cardiac myocytes from alpha(2A)/alpha(2C)-AR knockout mice by electron microscopy. Our results demonstrate that chronic elevation of sympathetic tone can lead to abnormal cardiac function in the absence of prior myocardial injury or genetically induced alterations in myocardial structural or functional proteins. These mice provide a physiologically relevant animal model for investigating the role of the sympathetic nervous system in the development and progression of heart failure.
View details for DOI 10.1152/ajpheart.01063.2001
View details for Web of Science ID 000178625800012
View details for PubMedID 12384461
Cardiovascular and metabolic alterations in mice lacking beta 1- and beta 2-adrenergic receptors
TRENDS IN CARDIOVASCULAR MEDICINE
2002; 12 (7): 287-294
Targeted disruption of murine beta-adrenergic receptor (beta-AR) genes has helped to clarify the role of specific beta-AR subtypes in regulating cardiovascular development and function. In the mouse, the beta1-AR is primarily responsible for sympathetic regulation of both cardiac chronotropy and inotropy. In contrast, all three beta-ARs play a role in regulating peripheral vascular tone. The impact of ablation of both beta1- and beta2-ARs on cardiac development and on resting cardiovascular and metabolic parameters is remarkably minimal. However, exercise stress reveals additional important contributions of beta1- and beta2-ARs to cardiovascular performance.
View details for Web of Science ID 000178580700002
View details for PubMedID 12458090
Long-term follow-up after total lymphoid irradiation in pediatric heart transplant recipients
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2002; 21 (6): 667-673
Total lymphoid irradiation (TLI) is used to treat recurrent allograft rejection. Short-term success and complication rates have been reported in pediatric and adult cardiac transplant populations. We report the long-term efficacy and safety of TLI in treating intractable rejection in pediatric patients.Eight pediatric patients were treated with TLI (7 for recurrent rejection, 1 for risk of medication non-compliance). Therapy consisted of a mid-plane dose of 8 Gy administered with a 6-MeV linear accelerator using an anterior-posterior opposed technique. We reviewed outcomes for a total of 40 patient-years of follow-up.We encountered rejection (>Grade 2 by International Society for Heart and Lung Transplantation criteria) in 56.7% +/- 34.7% of biopsies performed within 90 days before TLI. Rejection rates dropped to 3.1% +/- 8.8% within the first 90 days (p < 0.005) after therapy and remained low at 5.6% +/- 1.3% (p < 0.05) during the first year after completion of TLI. Median time from TLI to the first subsequent rejection episode was 305 days (range, 77-1,920 days). Long-term follow-up (>3 years) of 5 patients demonstrated a continuing low incidence of rejection. Non-Hodgkin's lymphoma was diagnosed in 1 of 8 patients, graft coronary artery disease in 4 of 8 patients, and restrictive cardiomyopathy in 1 of 8 patients after TLI.Total lymphoid irradiation is an effective treatment for recurrent rejection and has short- and long-term efficacy. Morbid events may include cancer, graft coronary artery disease, and restrictive cardiomyopathy.
View details for Web of Science ID 000176074500008
View details for PubMedID 12057700
Infant heart transplantation at Stanford: Growth and neurodevelopmental outcome
2002; 109 (1): 1-7
To evaluate the growth and neurodevelopmental outcome of 18 surviving Stanford patients who received heart transplantations before their second birthday.We compared the growth and neurodevelopmental outcome of these 18 patients with a second group of age-matched comparison patients who underwent other heart surgery requiring cardiopulmonary bypass.Difficulties with growth and development were more common in the transplant group as were neurologic abnormalities. Speech and language delays as well as hearing problems were also more common in the transplant group.Multicenter prospective longitudinal neurodevelopmental outcome studies of infant heart transplant patients should be conducted to provide a more efficient basis for evaluating management protocols and assessment of long-term outcomes and of the need for early intervention services.
View details for Web of Science ID 000173006600019
View details for PubMedID 11773534
- Survey of current practices in use of amiodarone and implantable cardioverter defibrillators in pediatric patients with end-stage heart failure AMERICAN JOURNAL OF CARDIOLOGY 2001; 88 (7): 809-?
L-Arginine enhances aerobic exercise capacity in association with augmented nitric oxide production
JOURNAL OF APPLIED PHYSIOLOGY
2001; 90 (3): 933-938
We tested whether supplementation with L-arginine can augment aerobic capacity, particularly in conditions where endothelium-derived nitric oxide (EDNO) activity is reduced. Eight-week-old wild-type (E(+)) and apolipoprotein E-deficient mice (E(-)) were divided into six groups; two groups (LE(+) and LE(-)) were given L-arginine (6% in drinking water), two were given D-arginine (DE(+) and DE(-)), and two control groups (NE(+) and NE(-)) received no arginine supplementation. At 12-16 wk of age, the mice were treadmill tested, and urine was collected after exercise for determination of EDNO production. NE(-) mice demonstrated a reduced aerobic capacity compared with NE(+) controls [maximal oxygen uptake (VO(2 max)) of NE(-) = 110 +/- 2 (SE) vs. NE(+) = 122 +/- 3 ml O(2). min(-1). kg(-1), P < 0.001]. This decline in aerobic capacity was associated with a diminished postexercise urinary nitrate excretion. Mice given L-arginine demonstrated an increase in postexercise urinary nitrate excretion and aerobic capacity in both groups (VO(2 max) of LE(-) = 120 +/- 1 ml O(2). min(-1). kg(-1), P < 0.05 vs. NE(-); VO(2 max) of LE(+) = 133 +/- 4 ml O(2). min(-1). kg(-1), P < 0.01 vs. NE(+)). Mice administered D-arginine demonstrated an intermediate increase in aerobic capacity in both groups. We conclude that administration of L-arginine restores exercise-induced EDNO synthesis and normalizes aerobic capacity in hypercholesterolemic mice. In normal mice, L-arginine enhances exercise-induced EDNO synthesis and aerobic capacity.
View details for Web of Science ID 000167051400024
View details for PubMedID 11181603
Efficacy and safety of atorvastatin after pediatric cardiac transplantation.
The Journal of heart and lung transplantation : the official publication of the International Society for Heart Transplantation
2001; 20 (2): 230
View details for PubMedID 11250440
Outcome while awaiting heart transplantation in children: A comparison of congenital heart disease and cardiomyopathy
JOURNAL OF HEART AND LUNG TRANSPLANTATION
2000; 19 (8): 751-755
Outcomes for children who undergo heart transplantation differ for children with congenital heart disease as compared to those with structurally normal hearts. Similar data have not been reported for these groups of patients for the morbidity and mortality associated with waiting for a donor. We report these data.A retrospective review was performed for all pediatric patients who were listed for heart transplantation at Stanford from 1977 to 1996, comparing mortality and major morbidity for patients with congenital heart disease and those with cardiomyopathy and structurally normal hearts.There were 96 patients who met study criteria, of whom 67 were successfully transplanted. The median waiting time was 23 days. Survival at 30 days was 93% and at 90 days was 81%, with no difference between groups. Major complications were identified in 38% of patients with structurally normal hearts, vs 9% of patients with congenital heart disease (p < 0.001).Overall mortality is similar for patients with congenital heart disease and those with structurally normal hearts while listed for heart transplantation, but patients with congenital heart disease have fewer episodes of major morbidity during this time.
View details for Web of Science ID 000089041400005
View details for PubMedID 10967268
Lipoprotein abnormalities are highly prevalent in pediatric heart transplant recipients.
2000; 4 (3): 193-199
The role of hyperlipidemia in graft coronary artery disease (GCAD) is controversial although hyper-triglyceridemia is an independent risk factor. Recent studies show that 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) inhibitors decrease the incidence of GCAD in adults. The incidence of GCAD in pediatric patients is lower than in adults; it is not clear whether age-related differences in lipid metabolism account for some of this protection. This study was performed to: characterize the lipoprotein profile in children after heart transplantation; demonstrate that total cholesterol (TC) is a poor marker for underlying lipoprotein abnormalities; and to compare lipid abnormalities in patients who had been converted from cyclosporin A (CsA) to tacrolimus. Seventy-one determinations of fasting lipoprotein profiles were performed in a cohort of 28 children. Each child had at least two determinations on separate occasions. TC, low-density lipoprotein (LDL), and serum triglyceride (TG) levels were categorized as abnormal if greater than the 75th percentile for age and gender. A high-density lipoprotein (HDL) level less than the 25th percentile was considered abnormal. Immunosuppression included CsA or tacrolimus, azathioprine, and prednisone. We found that 90% of the patients studied had abnormalities of either TG or HDL. In contrast, LDL tended to be normal when adjusted for age and gender. TC was a poor indicator of any underlying abnormality in TG, LDL, or HDL. In patients converted to tacrolimus, no significant differences were found in the levels of TG, LDL or HDL compared with each patient's respective values while receiving CsA. Hence, lipoprotein abnormalities among pediatric heart transplant recipients are highly prevalent. TC is a poor screening tool in the evaluation for lipid abnormalities. Lipoprotein profiles remain statistically unchanged after conversion from CsA to tacrolimus.
View details for PubMedID 10933319
Safety and utility of the routine surveillance biopsy in pediatric patients 2 years after heart transplantation
JOURNAL OF PEDIATRICS
2000; 136 (2): 238-242
The standard for diagnosing allograft rejection after heart transplantation is the endomyocardial biopsy, but the value of routine surveillance biopsies after 2 years after transplant is controversial. The objective of this study was to determine the necessity and safety of surveillance biopsies and to correlate rejection with signs and symptoms beyond the second post-transplant anniversary in pediatric patients.We reviewed the results of 899 biopsies and coincident clinical histories in 56 pediatric patients, comprising 314 patient-years of follow-up. Patients were classified as having symptoms or not based on a blinded review of their clinical status and echocardiograms. Biopsies were classified as negative or positive with established criteria.After biopsies performed less than 2 years after transplant or as a follow-up for a positive biopsy were excluded, 481 biopsies were available for analysis, of which 20 (4%) were positive. Positive biopsies were found in 15 (3%) of 456 biopsies in patients without symptoms compared with 5 (20%) of 25 biopsies in patients with symptoms. Patients with symptoms were 6 times more likely to have a positive biopsy compared with patients without symptoms. Of the positive rejection episodes, 75% occurred in patients without symptoms.Although rejection is uncommon in pediatric patients greater than 2 years after transplant, episodes of treatable allograft rejection can occur in the absence of clinical signs and symptoms. This study emphasizes the safety of and the need to continue to perform routine surveillance biopsies in patients without symptoms, even after the second post-transplant year.
View details for Web of Science ID 000085289400023
View details for PubMedID 10657832
The use of advanced-age donor hearts adversely affects survival in pediatric heart transplantation.
1999; 3 (4): 309-314
There is a limited supply of adequate donor hearts for cardiac transplantation. The safety of using advanced-age donor hearts has been debated in adult transplantation but has not been studied previously in pediatric recipients. In this retrospective study, survival of 79 pediatric heart transplant recipients was reviewed. Pediatric recipient groups were stratified based on donor age (group 1 donor age > 40 yr, n = 5; group 2 donor age < or = 40 yr, n = 74). Survival of 267 adolescent (ages 11-17) heart transplant recipients in the United Network for Organ Sharing (UNOS) database was also reviewed. Patients were likewise divided into two groups based on donor age (> 40 yr, n = 12; < or = 40 yr, n = 255). Survival at one yr was 20% in group 1 vs. 78% in group 2 (p < 0.005). Cause of death in all group 1 patients was graft failure secondary to acute rejection. Analysis of risk of death was only significantly attributable to the age of the donor. The increased risk attributable to advanced donor age was also supported by the UNOS data. The UNOS one and two-year Kaplan-Meier survival curves were significantly lower in adolescent patients who received donor hearts > 40 yr of age. One-year survival was 58% (older donors) vs. 85% (younger donors, p < 0.005) and two-year survival was 44% (older donors) vs. 79% (younger donors, p < 0.005). Advanced-age donor hearts should be contraindicated in pediatric transplantation with the exception of critically ill patients who may not be able to wait for a younger heart.
View details for PubMedID 10562976
Heart transplantation in children: indications. Report of the Ad Hoc Subcommittee of the Pediatric Committee of the American Society of Transplantation (AST).
1999; 3 (4): 333-342
This review details the indications for heart transplantation in children. Contraindications have evolved from absolute to relative. Controversial issues remain and this paper represents a consensus of more than a dozen centers that have programs that remain active performing pediatric heart transplants.
View details for PubMedID 10562980
QT dispersion predicts ventricular arrhythmia in pediatric cardiomyopathy patients referred for heart transplantation
JOURNAL OF HEART AND LUNG TRANSPLANTATION
1999; 18 (8): 781-785
QT dispersion has been used in stratifying risk for sudden death in adults with dilated cardiomyopathy, but its role in the pediatric population has not been delineated.We reviewed electrocardiograms in pediatric patients with dilated cardiomyopathy referred for heart transplantation, to evaluate the role of QT dispersion in predicting malignant arrhythmias in these patients. Three groups were defined: Group I (n = 13) had dilated cardiomyopathy and malignant ventricular arrhythmias, Group II (n = 13) had dilated cardiomyopathy with no ventricular arrhythmias and Group III (n = 30) consisted of normals. QT dispersion was defined as the duration of the shortest QT subtracted from that of the longest. In addition, the standard deviation of the QT intervals was calculated for each ECG, using 12 leads.QT dispersion was significantly prolonged in Group I (97 +/- 33 msec) compared to Group II (74 +/- 19 msec) and Group III (42 +/- 17 msec). QT standard deviation was also prolonged in Group I (30 +/- 11 msec) vs Group II (22 +/- 5 msec) and Group III (13 +/- 4 msec). Using a threshold value of 90 msec for QT dispersion or 25 msec for QT standard deviation, a sensitivity of 78% and a specificity of 70% was obtained for identifying patients who would subsequently develop ventricular arrhythmias.In pediatric heart transplant candidates with dilated cardiomyopathy, QT dispersion and QT standard deviation identify patients at higher risk for the development of malignant ventricular arrhythmia. This simple test can be helpful in the evaluation and management of these patients awaiting transplantation.
View details for Web of Science ID 000082347500007
View details for PubMedID 10512525
Abnormal regulation of the sympathetic nervous system in alpha(2A)-adrenergic receptor knockout mice
1999; 56 (1): 154-161
alpha2-Adrenergic receptors (ARs) play a key role in regulating neurotransmitter release in the central and peripheral sympathetic nervous systems. To date, three subtypes of alpha2-ARs have been cloned (alpha2A, alpha2B, and alpha2C). Here we describe the physiological consequences of disrupting the gene for the alpha2A-AR. Mice lacking functional alpha2A subtypes were compared with wild-type (WT) mice, with animals lacking the alpha2B or alpha2C subtypes, and with mice carrying a point mutation in the alpha2A-AR gene (alpha2AD79N). Deletion of the alpha2A subtype led to an increase in sympathetic activity with resting tachycardia (knockout, 581 +/- 21 min-1; WT, 395 +/- 21 min-1), depletion of cardiac tissue norepinephrine concentration (knockout, 676 +/- 31 pg/mg protein; WT, 1178 +/- 98 pg/mg protein), and down-regulation of cardiac beta-ARs (Bmax: knockout, 23 +/- 1 fmol/mg protein; WT, 31 +/- 2 fmol/mg protein). The hypotensive effect of alpha2 agonists was completely absent in alpha2A-deficient mice. Presynaptic alpha2-AR function was tested in two isolated vas deferens preparations. The nonsubtype-selective alpha2 agonist dexmedetomidine completely blocked the contractile response to electrical stimulation in vas deferens from alpha2B-AR knockout, alpha2C-AR knockout, alpha2AD79N mutant, and WT mice. The maximal inhibition of vas deferens contraction by the alpha2 agonist in alpha2A-AR knockout mice was only 42 +/- 9%. [3H]Norepinephrine release studies performed in vas deferens confirmed these findings. The results indicate that the alpha2A-AR is a major presynaptic receptor subtype regulating norepinephrine release from sympathetic nerves; however, the residual alpha2-mediated effect in the alpha2A-AR knockout mice suggests that a second alpha2 subtype (alpha2B or alpha2C) also functions as a presynaptic autoreceptor to inhibit transmitter release.
View details for Web of Science ID 000081240600019
View details for PubMedID 10385696
Targeted disruption of the beta 2 adrenergic receptor gene
JOURNAL OF BIOLOGICAL CHEMISTRY
1999; 274 (24): 16694-16700
beta-Adrenergic receptors (beta-ARs) are members of the superfamily of G-protein-coupled receptors that mediate the effects of catecholamines in the sympathetic nervous system. Three distinct beta-AR subtypes have been identified (beta1-AR, beta2-AR, and beta3-AR). In order to define further the role of the different beta-AR subtypes, we have used gene targeting to inactivate selectively the beta2-AR gene in mice. Based on intercrosses of heterozygous knockout (beta2-AR +/-) mice, there is no prenatal lethality associated with this mutation. Adult knockout mice (beta2-AR -/-) appear grossly normal and are fertile. Their resting heart rate and blood pressure are normal, and they have a normal chronotropic response to the beta-AR agonist isoproterenol. The hypotensive response to isoproterenol, however, is significantly blunted compared with wild type mice. Despite this defect in vasodilation, beta2-AR -/- mice can still exercise normally and actually have a greater total exercise capacity than wild type mice. At comparable workloads, beta2-AR -/- mice had a lower respiratory exchange ratio than wild type mice suggesting a difference in energy metabolism. beta2-AR -/- mice become hypertensive during exercise and exhibit a greater hypertensive response to epinephrine compared with wild type mice. In summary, the primary physiologic consequences of the beta2-AR gene disruption are observed only during the stress of exercise and are the result of alterations in both vascular tone and energy metabolism.
View details for Web of Science ID 000080780400007
View details for PubMedID 10358008
Cardiovascular and metabolic alterations in mice lacking both beta 1-and beta 2-adrenergic receptors
JOURNAL OF BIOLOGICAL CHEMISTRY
1999; 274 (24): 16701-16708
The activation state of beta-adrenergic receptors (beta-ARs) in vivo is an important determinant of hemodynamic status, cardiac performance, and metabolic rate. In order to achieve homeostasis in vivo, the cellular signals generated by beta-AR activation are integrated with signals from a number of other distinct receptors and signaling pathways. We have utilized genetic knockout models to test directly the role of beta1- and/or beta2-AR expression on these homeostatic control mechanisms. Despite total absence of beta1- and beta2-ARs, the predominant cardiovascular beta-adrenergic subtypes, basal heart rate, blood pressure, and metabolic rate do not differ from wild type controls. However, stimulation of beta-AR function by beta-AR agonists or exercise reveals significant impairments in chronotropic range, vascular reactivity, and metabolic rate. Surprisingly, the blunted chronotropic and metabolic response to exercise seen in beta1/beta2-AR double knockouts fails to impact maximal exercise capacity. Integrating the results from single beta1- and beta2-AR knockouts as well as the beta1-/beta2-AR double knock-out suggest that in the mouse, beta-AR stimulation of cardiac inotropy and chronotropy is mediated almost exclusively by the beta1-AR, whereas vascular relaxation and metabolic rate are controlled by all three beta-ARs (beta1-, beta2-, and beta3-AR). Compensatory alterations in cardiac muscarinic receptor density and vascular beta3-AR responsiveness are also observed in beta1-/beta2-AR double knockouts. In addition to its ability to define beta-AR subtype-specific functions, this genetic approach is also useful in identifying adaptive alterations that serve to maintain critical physiological setpoints such as heart rate, blood pressure, and metabolic rate when cellular signaling mechanisms are perturbed.
View details for Web of Science ID 000080780400008
View details for PubMedID 10358009
- American Pediatric Society Society for Pediatric Research code of responsible conduct of research PEDIATRIC RESEARCH 1999; 45 (5): 613-614
Phospholamban deficiency does not compromise exercise capacity
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
1999; 276 (4): H1172-H1177
Deficiency of phospholamban (PLB) results in enhancement of basal murine cardiac function and an attenuated response to beta-adrenergic stimulation. To determine whether the absence of PLB also reduces the reserve capacity of the murine cardiovascular system to respond to stress, we evaluated the heart rate (HR), blood pressure, and metabolic responses of PLB-deficient (PLB-/-) mice to graded treadmill exercise (GTE). PLB-/- mice were hypertensive at rest (125 +/- 19 vs. 109 +/- 16 mmHg, P < 0.05) but had normal tachycardic and hypotensive responses to isoproterenol. The HR response to GTE was normal; however, the hypertension in PLB-/- mice normalized at peak exercise. Their exercise capacities, as measured by duration of exercise and peak oxygen consumption (VO2), were normal. The oxygen pulse (VO2/HR) curve was also normal in PLB-/- mice, suggesting an ability to appropriately increase stroke volume and oxygen extraction during GTE, despite an inability to increase beta-adrenergically stimulated cardiac contractility. Thus deficiency of PLB, although resulting in diminished beta-adrenergic inotropic reserve, does not compromise cardiac performance during exercise.
View details for Web of Science ID 000079554200009
View details for PubMedID 10199840
Impaired aerobic capacity in hypercholesterolemic mice: partial reversal by exercise training
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
1999; 276 (4): H1346-H1354
The present study assessed whether impaired aerobic capacity previously observed in hypercholesterolemic mice is reversible by exercise training. Seventy-two 8-wk-old female C57BL/6J wild-type (+, n = 42) and apolipoprotein E-deficient (-, n = 30) mice were assigned to the following eight interventions: normal chow, sedentary (E+, n = 17; E-, n = 8) or exercised (E+ex, n = 13; E-ex, n = 7) and high-fat chow, sedentary (E+chol, n = 6; E-chol, n = 8) or exercised (E+chol-ex, n = 6; E-chol-ex, n = 7). Mice were trained on a treadmill 2 x 1 h/day, 6 days/wk, for 4 wk. Cholesterol levels correlated inversely with maximum oxygen uptake (r = -0.35; P < 0. 02), which was blunted in all hypercholesterolemic sedentary groups (all P < 0.05). Maximum oxygen uptake improved in all training groups but failed to match E+ex (all P < 0.05). Vascular reactivity and nitric oxide (NO) synthesis correlated with anaerobic threshold (r = 0.36; P < 0.025) and maximal distance run (r = 0.59; P < 0.007). We conclude that genetically induced hypercholesterolemia impairs aerobic capacity. This adverse impact of hypercholesterolemia on aerobic capacity may be related to its impairment of vascular NO synthesis and/or vascular smooth muscle sensitivity to nitrovasodilators. Aerobic capacity is improved to the same degree by exercise training in normal and genetically hypercholesterolemic mice, although there remains a persistent difference between these groups after training.
View details for Web of Science ID 000079554200030
View details for PubMedID 10199861
Limb blood flow during exercise is dependent on nitric oxide
1998; 98 (4): 369-374
We have recently reported that hypercholesterolemia reduces aerobic exercise capacity in mice and that this is associated with a reduced endothelium-dependent vasodilator function, endothelium-derived nitric oxide (EDNO) production, and urinary nitrate excretion. These findings led us to test the hypothesis that EDNO production contributes significantly to limb blood flow during exercise and to determine whether loss of EDNO production is responsible for the decline in exercise capacity observed in hypercholesterolemia.Twelve-week-old wild-type (E+; n=9) and apoE-deficient (E-; n=9) C57BL/6J mice were treadmill-tested to measure indices defining exercise capacity on a metabolic chamber-enclosed treadmill capable of measuring oxygen uptake and carbon dioxide excretion. Urine was collected before and after treadmill exercise for determination of vascular NO production assessed by urinary nitrate excretion. The wild-type mice were then given nitro-L-arginine (E+LNA) in the drinking water (6 mg/dL) for 4 days before undergoing a second treadmill testing and urinary nitrate measurement. An additional set of 12-week-old wild-type mice was divided into 2 groups: 1 receiving regular water (E+; n=8) and 1 administered LNA for 4 days (E+LNA; n=8). These mice, along with an additional set of E mice (n=8), underwent treadmill testing to determine maximal oxygen uptake (VO2max). The mice were then cannulated such that the tip of the tubing was positioned in the ascending aorta. Fluorescent microspheres (20000) were infused into the carotid cannula while the mice were sedentary and again while approaching VO2max. When the mice were euthanized, the running muscles were collected and fluorescence intensity was measured to determine the peak-exercise redistribution of blood flow to the running muscles (expressed as percentage of total cardiac output, %COrm) during both states. Both E+LNA and E- mice demonstrated a markedly reduced postexercise urinary nitrate excretion, aerobic capacity, and %COrm at VO2max compared with E+.EDNO contributes significantly to limb blood flow during exercise. Conditions that reduce EDNO production disturb the hyperemic response to exercise, resulting in a reduced exercise capacity.
View details for Web of Science ID 000074984800014
View details for PubMedID 9711943
Alterations in dynamic heart rate control in the beta(1)-adrenergic receptor knockout mouse
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
1998; 274 (4): H1184-H1193
beta 1-Adrenergic receptors (beta 1-ARs) are key targets of sympathetic nervous system activity and play a major role in the beat-to-beat regulation of cardiac chronotropy and inotropy. We employed a beta 1-AR gene knockout model to test the hypothesis that beta 1-AR function is critical for maintenance of resting heart rate and baroreflex responsiveness and, on the basis of its important role in regulating chronotropy and inotropy, is also required for maximal exercise capacity. Using an awake unrestrained mouse model, we demonstrate that resting heart rate and blood pressure are normal in beta 1-AR knockouts and that the qualitative responses to baroreflex stimulation are intact. Chronotropic reserve in beta 1-AR knockouts is markedly limited, with peak heart rates approximately 200 beats/min less than wild types. During graded treadmill exercise, heart rate is significantly depressed in beta 1-AR knockouts at all work loads, but despite this limitation, there are no reductions in maximal exercise capacity or metabolic indexes. Thus, in mice, the beta 1-AR is not essential for either maintenance of resting heart rate or for maximally stressed cardiovascular performance.
View details for Web of Science ID 000072839800015
View details for PubMedID 9575921
Elective transplant pneumonectomy
JOURNAL OF PEDIATRIC SURGERY
1998; 33 (4): 655-656
The use of a single lung transplant, modified with removal of the middle lobe of the donor right lung, has been described for a term neonate with respiratory distress secondary to right-sided congenital diaphragmatic hernia. The successful transplant allowed the patient to be successfully weaned from extracorporeal membrane oxygenation. Because of the early age of the patient at transplantation (3 weeks), it was unclear how the patient's left lung would develop, and there was uncertainty regarding the risk of life-time immunosuppression. By the age of 4 years, 10 months, she was demonstrating some failure to thrive, hypertension, and hirsutism, obvious side effects of chronic immunosuppression. The question was raised as to the potential for transplant pneumonectomy. A ventilation-perfusion scan demonstrated a decrease of right lung ventilation compared with the immediate postoperative period (27% versus 43%); right heart catheterization with balloon occlusion of the right main pulmonary artery suggested that the patient would tolerate right pneumonectomy. After discussion with the family, the patient underwent transplant pneumonectomy via a right posterolateral approach. Findings at the time of operation included mild to moderate adhesions as well as recurrence of the diaphragmatic hernia. She tolerated the procedure well and was discharged home on the fifth postoperative day with cessation of her immunosuppression. The immediate and medium-term success of this procedure suggests the potential for temporizing transplantation as a palliation to promote survival until the remaining native lung can provide sufficient ventilation.
View details for Web of Science ID 000073170200027
View details for PubMedID 9574774
The developmental and physiological consequences of disrupting genes encoding beta 1 and beta 2 adrenoceptors.
Advances in pharmacology (San Diego, Calif.)
1998; 42: 499-501
View details for PubMedID 9327949
Survival and risk factors for death after cardiac transplantation in infants - A multi-institutional study
1997; 96 (1): 227-231
View details for Web of Science ID A1997XJ44200037
Predicting outcome after listing for heart transplantation in children: Comparison of Kaplan-Meier and parametric competing risk analysis
JOURNAL OF HEART AND LUNG TRANSPLANTATION
1997; 16 (7): 713-722
View details for Web of Science ID A1997XN72100002
Cardiovascular indexes in the mouse at rest and with exercise: New tools to study models of cardiac disease
AMERICAN JOURNAL OF PHYSIOLOGY-HEART AND CIRCULATORY PHYSIOLOGY
1997; 272 (2): H1053-H1061
Manipulations of the murine genome that alter cardiovascular function have created the need for methods to study cardiovascular physiology in genetically altered animals in vivo. We adapted chronic physiological measurement techniques to the nonanesthetized, nonrestrained murine model, established strain-specific cardiovascular and metabolic norms, and evaluated responses to anesthesia, exercise, and adrenergic stimulation. Anesthesia resulted in alterations in heart rate (HR), blood pressure (BP), and O2 consumption (V(O2)) and CO2 production (V(CO2)) for up to 6 h postoperatively. There were significant interstrain differences in resting values of HR and BP Graded treadmill exercise resulted in linear increases in HR, V(O2), V(CO2), and respiratory exchange ratio (RER) similar to those seen in larger species. Response to beta-adrenergic stimulation showed a classic sigmoidal dose-response curve; however, there was very little tachycardiac response to vagal blockade, indicating low resting vagal tone. This study demonstrates the feasibility of performing chronic cardiovascular measurements in nonanesthetized mice and stresses the importance of allowing for anesthetic recovery and strain variability. Murine cardiovascular responses to exercise can be reliably measured and are qualitatively similar to those in humans.
View details for Web of Science ID A1997WJ80900057
View details for PubMedID 9124413
Cardiovascular regulation in mice lacking alpha(2)-adrenergic receptor subtypes b and c
1996; 273 (5276): 803-805
alpha2-Adrenergic receptors (alpha2ARs) are essential components of the neural circuitry regulating cardiovascular function. The role of specific alpha2AR subtypes (alpha2a, alpha2b, and alpha2c) was characterized with hemodynamic measurements obtained from strains of genetically engineered mice deficient in either alpha2b or alpha2c receptors. Stimulation of alpha2b receptors in vascular smooth muscle produced hypertension and counteracted the clinically beneficial hypotensive effect of stimulating alpha2a receptors in the central nervous system. There were no hemodynamic effects produced by disruption of the alpha2c subtype. These results provide evidence for the clinical efficacy of more subtype-selective alpha2AR drugs.
View details for Web of Science ID A1996VB42900045
View details for PubMedID 8670422
Targeted disruption of the mouse beta 1-adrenergic receptor gene: Developmental and cardiovascular effects
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1996; 93 (14): 7375-7380
At least three distinct beta-adrenergic receptor (beta-AR) subtypes exist in mammals. These receptors modulate a wide variety of processes, from development and behavior, to cardiac function, metabolism, and smooth muscle tone. To understand the roles that individual beta-AR subtypes play in these processes, we have used the technique of gene targeting to create homozygous beta 1-AR null mutants (beta 1-AR -/-) in mice. The majority of beta 1-AR -/- mice die prenatally, and the penetrance of lethality shows strain dependence. Beta l-AR -/- mice that do survive to adulthood appear normal, but lack the chronotropic and inotropic responses seen in wild-type mice when beta-AR agonists such as isoproterenol are administered. Moreover, this lack of responsiveness is accompanied by markedly reduced stimulation of adenylate cyclase in cardiac membranes from beta 1-AR -/- mice. These findings occur despite persistent cardiac beta 2-AR expression, demonstrating the importance of beta 1-ARs for proper mouse development and cardiac function, while highlighting functional differences between beta-AR subtypes.
View details for Web of Science ID A1996UW79200098
View details for PubMedID 8693001
CARDIAC TRANSPLANTATION FOR HYPERTROPHIC CARDIOMYOPATHY ASSOCIATED WITH SENGERS-SYNDROME
ANNALS OF THORACIC SURGERY
1995; 60 (5): 1425-1427
Sengers' syndrome is a rare condition consisting of congenital cataracts, mitochondrial myopathy, and hypertrophic cardiomyopathy. The syndrome is transmitted in an autosomal recessive pattern. Progressive cardiac failure is the cause of death in most patients. This report describes cardiac transplantation for the treatment of the cardiomyopathy associated with Sengers' syndrome.
View details for Web of Science ID A1995TE95600056
View details for PubMedID 8526648
COLCHICINE AND CYTOCHALASIN-B ENHANCE CYCLIC-AMP ACCUMULATION VIA POSTRECEPTOR ACTIONS
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
1995; 274 (2): 937-942
The role of cytoskeletal microtubules and microfilaments in modulating cAMP generation in S49 lymphoma cells was investigated using the agents colchicine and cytochalasin B, respectively, which are known to disrupt these structures. A 1-hr pretreatment of S49 cells with 10 microM colchicine typically enhanced maximal isoproterenol-(beta-adrenergic receptor) stimulated cAMP accumulation by 100%, whereas cytochalasin B increased isoproterenol-stimulated cAMP by 30%. The combination of colchicine and cytochalasin B synergistically enhanced agonist-stimulated cAMP to 225% over control values. A synergistic increase in cAMP accumulation was also observed in cells treated with the agonist prostaglandin E1 or cholera toxin (which activates the stimulatory guanine nucleotide regulatory (Gs) protein). Colchicine and cytochalasin B did not ablate the inhibitory effects of somatostatin or the stimulatory effect of pertussis toxin treatment on beta-receptor-stimulated cAMP accumulation, indicating that these cytoskeletal disrupting agents do not enhance responsiveness in S49 cells via alterations in the inhibitory guanine nucleotide regulatory protein pathway. Moreover, colchicine, but not cytochalasin B treatment, enhances expression of isoproterenol-promoted 3H-forskolin binding in intact cells (a measure of Gs/adenylyl cyclase coupling). Thus, colchicine and cytochalasin B appear to enhance signaling in the Gs/adenylyl cyclase pathway by alterations of components distal to hormone receptors, most likely at the Gs protein and/or via cAMP generation. These results imply that microtubules and microfilaments can interact in the regulation of this pathway and that increases in cellular cAMP may contribute to the action of drugs that alter function of these cytoskeletal elements.
View details for Web of Science ID A1995RN98300048
View details for PubMedID 7636757
ARTERIAL SWITCH AND RESECTION OF HEPATIC HEMANGIOENDOTHELIOMA
ANNALS OF THORACIC SURGERY
1995; 59 (6): 1575-1577
We report on the management of a neonate undergoing arterial switch for transposition of the great arteries and concomitant resection of a hepatic infantile hemangioendothelioma. A preoperative aortogram demonstrated the arterial supply of the hepatic hemangioendothelioma. Pulmonary artery hypertension and myocardial ischemia were noted after separation from cardiopulmonary bypass. Resection of the hepatic malformation produced an immediate reduction in pulmonary hypertension and resolution of the myocardial ischemia. The patient had an uneventful postoperative recovery.
View details for Web of Science ID A1995RB62100052
View details for PubMedID 7771849
Pediatric cardiac transplantation. The Stanford experience.
1994; 90 (5): II51-5
Cardiac transplantation for children with endstage heart disease has become an accepted form of therapy and is being practiced with increasing frequency and improving short-term outcome.To assess the medium-term outcome of pediatric cardiac transplantation, we analyzed our experience with 72 patients under the age of 18 (range, 0.1 to 17.7 years; mean, 9 +/- 6.4 [SD]) who underwent orthotopic cardiac transplantation at Stanford University between 1977 and 1993. There were 38 male and 34 female patients. Preoperative diagnoses included congenital heart disease in 24 (33%), idiopathic cardiomyopathy in 27 (37%), viral cardiomyopathy in 12 (17%), and familial cardiomyopathy in 7 (10%) patients. Immunosuppressive management has evolved over time and has included a tapering schedule of steroids, azathioprine, rabbit antithymocyte globulin, cyclosporine in all patients after 1980, and induction with OKT3 since 1987. Operative mortality rate was 12.5 +/- 4.0% (mean +/- 70% confidence intervals). Actuarial survival estimates at 1, 5, and 10 years are 75 +/- 7.1%, 60 +/- 6.4%, and 50 +/- 8.1% (mean +/- 1 SEM), respectively. Causes of death included infection in 8 (28% of deaths), rejection in 7 (24%), graft coronary disease in 5 (17%), pulmonary hypertension in 4 (14%), and nonspecific graft failure in 2 (7%) patients. Survival rates were similar for patients over and those under age 10 years (including the infant cohort of 18 patients transplanted since 1986). Currently, there are 43 patients alive, all in New York Heart Association functional class I. Only 22 +/- 5.6% of patients were free of rejection at 1 year, but 86 +/- 5.4% were free of rejection-related death at 10 years. At 1 year, only 37 +/- 6% of patients were free from any infection, but 88 +/- 4.2% remained free of infection-related death at 5 years. Actuarial freedom from graft coronary artery disease (angiographic or autopsy proven) was 85 +/- 6.6% at 5 years and from coronary artery disease-related death was 91 +/- 4.7%.These data demonstrate satisfactory medium-term outcome of cardiac transplantation in selected pediatric patients with end-stage heart disease, but further progress is necessary to more effectively control rejection, infection, and graft coronary disease.
View details for PubMedID 7955282
- SUCCESSFUL THROMBOLYSIS OF A THROMBOSED ST-JUDE MEDICAL MITRAL PROSTHESIS IN A 2-MONTH-OLD INFANT JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY 1994; 108 (1): 187-187
Neoplastic disorders after pediatric heart transplantation.
1993; 88 (5): II230-7
Because of their life-long requirement for immunosuppressive therapy, neoplastic disorders could represent a significant threat to long-term survival in infants and children after heart transplantation. This study determined the incidence and clinical spectrum of neoplastic disorders in 80 pediatric patients who underwent heart transplantation between 1974 and 1992.Follow-up ranged from 6 to 189 months (mean, 50.0 months). Tumors occurred in 10 patients (12.5%). Time to detection ranged from 3.3 to 139.2 months (mean, 52.7 months). Tumor incidence was greatest in 9 patients transplanted before the cyclosporine era (44%) compared with the subsequent 71 patients (8.5%, P < .05). There was no increase in risk related to sex, age, underlying disease, or blood type; however, patients with tumors received higher initial doses of cyclosporine and prednisone and had more rejection episodes in the first 3 months (P < .05). There was an increased risk associated with anti-thymocyte globulin (33%, P < .05) but not with OKT3 (6%, P = NS). There were eight lymphoproliferative disorders (four B-cell, one T-cell, three not determined) and one hepatocellular and one squamous cell carcinomas. Six cases of lymphoproliferative disorder had in situ evidence of Epstein-Barr virus. Patients were treated by reducing immunosuppression (7), radiotherapy (2), and chemotherapy (1). There were five deaths: two tumor related and the others due to rejection, renal failure, and infection. Of 5 survivors, 1 had tumor recurrence 4 years after diagnosis, and 4 are disease free.Tumors represent a small but serious long-term risk to pediatric heart transplant recipients. The incidence in children transplanted in the cyclosporine era is similar to that in adults, and the majority of tumors are lymphoproliferative disorders that often regress by reducing immunosuppression.
View details for PubMedID 8222159
NEOPLASTIC DISORDERS AFTER PEDIATRIC HEART-TRANSPLANTATION
1993; 88 (5): 230-237
View details for Web of Science ID A1993ME83400032
HEART-TRANSPLANTATION IN INFANCY
PROGRESS IN PEDIATRIC CARDIOLOGY
1993; 2 (4): 20-28
View details for Web of Science ID A1993MM33200005
PRIMARY STRUCTURE OF THE MOUSE BETA(1)-ADRENERGIC RECEPTOR GENE
BIOCHIMICA ET BIOPHYSICA ACTA
1993; 1178 (3): 307-309
The mouse beta 1-adrenergic receptor was isolated from a genomic library and cloned into pBluescript SK-. Characterization of the clone revealed an open reading frame which encodes a predicted protein of 466 amino acids. The mouse beta 1 receptor is 92.7% identical to the human sequence, 98.5% identical to the rat sequence, and contains a consensus site for N-linked glycosylation at Asn-15 and a cAMP-dependent protein kinase phosphorylation site at Ser-301.
View details for Web of Science ID A1993LX80300011
View details for PubMedID 8395893
Update on cardiac transplantation in infants and children.
Critical care medicine
1993; 21 (9): S354-5
View details for PubMedID 8365223
ALTERATION IN GS-MEDIATED SIGNAL TRANSDUCTION IN S49 LYMPHOMA-CELLS TREATED WITH INHIBITORS OF MICROTUBULES
JOURNAL OF BIOLOGICAL CHEMISTRY
1993; 268 (6): 3833-3837
We have assessed the possible interaction between the microtubular component of the cytoskeleton and signal transducing GTP-binding (G) proteins by examining the ability of colchicine and vinblastine (two microtubule disrupters) to alter Gs and Gi protein activity in S49 lymphoma cells. Treatment of wild type S49 cells with cholchicine and vinblastine increased beta-adrenergic agonist- and prostaglandin (PG) E1-stimulated formation of cAMP. The microtubular inhibitor nocodazole also enhanced isoproterenol-stimulated cAMP accumulation, whereas the inactive analog of colchicine, beta-lumicolchicine, did not have this action. Based on data obtained with wild type, cyc-, and UNC S49 cells, we determined that enhancement in cyclic AMP accumulation is proximal to the catalytic (C) unit of adenylylcyclase, distal to hormone receptors, and seems to be located on Gs. Treatment with colchicine increased guanosine 5'-(gamma-thio)triphosphate-stimulated accumulation of cAMP in permeabilized wild type cells. The increase in activity of Gs appeared not to result from a change in the intracellular concentration of GTP. Treatment of cells with colchicine or vinblastine also increased the amount of the alpha s-C complex, as assessed by the binding of [3H]forskolin to intact cells at 37 degrees C. In contrast to the observed effect on Gs, treatment of wild type S49 cells with colchicine failed to modify the degree of inhibition of cAMP formation produced by somatostatin, which acts via the activation of Gi. These data suggest that microtubules regulate the ability of Gs to interact with and activate the catalyst of adenylylcyclase.
View details for Web of Science ID A1993KN53300010
View details for PubMedID 8095044
TRANSCRIPTIONAL REGULATION OF LEFT-VENTRICULAR BETA-ADRENERGIC RECEPTORS DURING CHRONIC HYPOXIA
1992; 71 (6): 1465-1471
beta-Adrenergic receptor downregulation is the end result of cellular adaptation to prolonged agonist exposure. The factors mediating receptor downregulation include receptor phosphorylation, receptor movement from the plasma membrane to intracellular sites, and alterations in nascent receptor synthesis. We have previously demonstrated a downregulation of the left ventricular beta-receptor during chronic hypoxia in vivo. To determine the mechanism of this downregulation, we produced chronic hypoxia in seven newborn lambs by creating right ventricular outflow obstruction and an atrial septal defect. Oxygen saturation was reduced to 65-74% for 2 weeks. Six lambs served as normoxic controls. Sarcolemmal membrane and cytosolic fractions were prepared from left ventricular free wall samples. beta-Receptor density in each fraction was determined with the radioligand [125I]iodocyanopindolol. Steady-state levels of beta-receptor mRNA were determined by Northern blot analysis using a beta 1-adrenergic receptor cDNA probe. During chronic hypoxia, left ventricular membrane beta-adrenergic receptor density decreased by 55% (153 +/- 28 fmol/mg for hypoxic lambs versus 342 +/- 79 fmol/mg for control lambs, p < 0.05). There was no corresponding increase in beta-receptor density in the cytosolic fraction (23 +/- 3 fmol/mg for hypoxic lambs versus 33 +/- 9 fmol/mg for control lambs, p = NS), nor was there a significant change in the ratio of beta 1-receptor/beta 2-receptor subtypes as assessed by radioligand binding (beta 1 subtype, 84.1 +/- 10.1% for hypoxic lambs versus 93.2 +/- 8.8% for control lambs; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1992JZ07200019
View details for PubMedID 1330359
CURRENT APPROACH TO HYPOPLASTIC LEFT HEART SYNDROME - PALLIATION, TRANSPLANTATION, OR BOTH
JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY
1992; 104 (1): 189-195
Over the past 3 years, 35 newborn infants have been referred for surgical management of hypoplastic left heart syndrome. Surgical palliation (first-stage Norwood) or cardiac transplantation was offered. Twenty-four families (68%) chose palliation and 11 families (32%) chose cardiac transplantation. Of the 11 infants listed for cardiac transplantation, five underwent transplantation. Because of a lack of donors after an average wait of 25 days (19 to 31), the remaining six infants underwent palliation, with no perioperative deaths. Of the 30 infants undergoing palliation, including crossovers, 20 (67%) survived the first operative stage. Among the last 19 infants undergoing palliation in 1990, the early survival was 84%. Risk factors determined for poor outcome were year of operation (p less than 0.001) and circulatory arrest time greater than 50 minutes (p less than 0.001). Among the 13 infants undergoing palliation with a circulatory arrest time of less than 50 minutes, there were 12 survivors (92%); among 12 having a circulatory arrest time of more than 50 minutes, there were four survivors (33%). At intermediate follow-up, six infants have undergone second-stage procedures (Glenn), with five survivors. There were eight late deaths, four caused by respiratory infections and four caused by cardiac problems, including a thrombosed shunt in one infant. Three of five infants are alive and doing well after cardiac transplantation. Size of aorta, tricuspid regurgitation, and ventricular wall thickness did not prove to be risk factors. Given the existing data, we believe these infants should be managed selectively on the basis of donor availability and family wishes.
View details for Web of Science ID A1992JD13800025
View details for PubMedID 1377313
CARDIAC GROWTH AFTER PEDIATRIC HEART-TRANSPLANTATION
1992; 85 (4): 1433-1439
To assess whether normal cardiac growth occurs after heart transplantation in the pediatric age group, we performed a study of 13 infants and children who underwent orthotopic heart transplantation at Stanford.The echocardiographic data from a population of 93 normal children were analyzed to determine estimates of the fifth, 25th, 50th, 75th, and 95th percentiles of the normal pediatric population. Growth curves for each of the cardiac dimensions were stratified into six classes representing each of the percentile bands, and dimensions for the 13 patients were tracked between early postoperative (early) and point of maximal follow-up (late). Results were compared by Student's paired t test to determine whether normal growth was occurring. The mean age at transplant was 5.0 +/- 1.3 years (mean +/- SEM) (range, 0.4-12.8 years), duration of follow-up was 3.1 +/- 0.4 years (1.3-5.8 years), and change in body surface area was 0.24 +/- 0.03 m2 (0.12-0.50 m2). Both right ventricular (RV) and left ventricular (LV) chamber dimensions were within the normal range at both early and late time points and grew normally as assessed by a lack of class changes. Early wall thickness measurements were above the 95th percentile in seven of 13 patients (LV), 12 of 13 patients (septum), and four of 13 patients (RV). Wall thickness measurements remained above normal, and there were no significant class changes at late follow-up. Histological examination in five patients showed markedly increased septal myocyte width, indicating myocyte hypertrophy. Atrial and great vessel anastomotic sites showed no evidence of obstruction by Doppler and catheterization studies.These data demonstrate that normal cardiac chamber dimensional growth occurs at greater than 3 years' follow-up after pediatric heart transplantation. Significant LV and septal (and to a lesser extent RV) hypertrophy persists and may have implications for long-term allograft growth and function.
View details for Web of Science ID A1992HN04900024
View details for PubMedID 1532543
DECREASED SERUM INSULIN-LIKE GROWTH FACTOR-I ASSOCIATED WITH GROWTH FAILURE IN NEWBORN LAMBS WITH EXPERIMENTAL CYANOTIC HEART-DISEASE
JOURNAL OF CLINICAL INVESTIGATION
1992; 89 (4): 1128-1132
To determine whether chronic hypoxemia results in alterations in endocrine function that may contribute to growth failure, we measured growth hormone (GH), somatomedins (insulin-like growth factors I and II, IGF-I and IGF-2), hepatic growth hormone receptors, and circulating IGF-binding proteins IGFBP-3 and IGFBP-2 in 12 newborn lambs with surgically created pulmonic stenosis and atrial septal defect, and in 10 controls. During chronic hypoxemia (oxygen saturation of 60-74% for 2 wk), weight gain was 60% of control (hypoxemic, 135 +/- 20 vs. control, 216 +/- 26 g/d, P less than 0.02). IGF-I was decreased by 43% (hypoxemic 253.6 +/- 29.3 SE vs. control 448.0 +/- 75.5 ng/ml, P = 0.01), whereas GH was unchanged (19.9 +/- 5.1 vs. 11.9 +/- 3.0 ng/ml, NS). The increase in IGF-1 was associated with a decrease in IGFBP-3 (hypoxemic, 5.09 +/- 1.25 vs. control, 11.2 +/- 1.08 arbitrary absorbency units per mm (Au.mm), P less than 0.01), and increase in IGFBP-2 (0.47 +/- 0.03 vs. 0.19 +/- 0.13 Au.mm, P less than 0.05), but no significant downregulation of hepatic GH receptors (hypoxemic, 106.1 +/- 20.1 vs. control, 147.3 +/- 25.9 fmol/mg, NS). Thus, chronic hypoxemia in the newborn is associated with a decrease in IGF-I and IGFBP-3 in the face of normal GH. This suggests peripheral GH unresponsiveness, similar to protein-calorie malnutrition or GH receptor deficiency dwarfism, but mediated at a level distal to the hepatic GH receptor.
View details for Web of Science ID A1992HL84000010
View details for PubMedID 1372914
ALTERATIONS IN POSTNATAL INTESTINAL FUNCTION DURING CHRONIC HYPOXEMIA
1992; 31 (3): 234-238
Growth failure is a major complication of chronic hypoxemia, as seen in infants and children with cyanotic congenital heart disease. To determine whether chronic hypoxemia during infancy affects the gastrointestinal tract, we examined small intestinal growth and digestive enzyme activities in chronically hypoxemic newborn lambs and in age-matched controls. Chronic hypoxemia was produced by placing an inflatable occluder around the main pulmonary artery and performing a balloon atrial septostomy. Aortic oxygen saturation was reduced to 60-74% for 2 wk, after which the small intestine was removed for analysis. During chronic hypoxemia, somatic growth rate was decreased to 60% of control (hypoxemic, 135 +/- 20 versus control, 216 +/- 26 g/d, p less than 0.02). No differences in caloric intake were found (hypoxemic, 129 +/- 4 versus control, 128 +/- 4 kcal/kg/d). Chronic hypoxemia did not alter small intestinal growth, as measured by jejuno-ileal weight, jejuno-ileal length, mucosal weight, or mucosal protein or DNA contents. However, sp act of lactase, the principal disaccharidase of the infant lamb intestine, were significantly decreased (hypoxemic, 0.08 +/- 0.01 versus control, 0.146 +/- 0.03 units of enzyme activity/mg DNA, p less than 0.05), as were the total small intestinal contents of lactase (hypoxemic, 61.7 +/- 7.0 versus control, 120.6 +/- 21.7 units of enzyme activity, p less than 0.01). There also were decreases in specific and total activities of other digestive enzymes such as maltase, amino-oligopeptidase, and alkaline phosphatase in hypoxemic intestine that did not achieve statistical significance.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1992HF34600007
View details for PubMedID 1561008
HEART, HEART-LUNG, AND LUNG TRANSPLANTATION IN THE 1ST YEAR OF LIFE
ANNALS OF THORACIC SURGERY
1992; 53 (2): 306-310
Seventeen infants less than 1 year of age have undergone heart (12), heart-lung (3), and lung (2) transplantation for end-stage cardiopulmonary disease. The infants undergoing heart transplantation had a mean age of 4.5 months (range, 19 days to 12 months) with the diagnosis of cardiomyopathy in 4 and congenital heart disease in 8. Four of the 8 patients (50%) had hypoplastic left heart syndrome. Actuarial survival at 1 and 2 years was 74% and compared favorably with the survival of older children at 1 and 2 years of 82% and 69%. The linearized rejection rate was less in infants as compared with children more than 1 year of age (0.61 versus 1.48 episodes per 100 patient days). In intermediate follow-up, no graft atherosclerosis has been noted. Immunosuppression has included a three-drug protocol of cyclosporine, azathioprine, and prednisone. A steroid taper to alternate day steroids or off completely by 6 months has been the goal and has been accomplished in 6 of 12 infants. Heart-lung and lung transplantation has been performed in 5 infants. One infant in each group died: 1 infant secondary to airway complications and sepsis and another due to pulmonary sepsis. A pulmonary lobe from a larger and older donor was transplanted into a 4-week-old infant as a single-lung transplant with good outcome. The 3 surviving infants are well 24, 18, and 2 months after transplantation. Obliterative bronchiolitis has not been clinically apparent in this group. These data support the clinical efficacy of heart, heart-lung, and lung transplantation in the first year of life.
View details for Web of Science ID A1992HB90700022
View details for PubMedID 1731673
REGULATION OF ATRIAL AUTONOMIC RECEPTORS IN EXPERIMENTAL CYANOTIC HEART-DISEASE
AMERICAN JOURNAL OF PHYSIOLOGY
1991; 261 (4): H1135-H1140
During chronic hypoxemia, left ventricular beta-adrenergic receptor density is decreased and a dissociation occurs between increased chronotropic and decreased inotropic responses to chronically elevated sympathetic tone. To determine whether this dissociation was related to alterations in autonomic receptor populations in the right atrium, we studied right atrial cholinergic and beta-adrenergic receptors in chronically hypoxemic newborn lambs and in normoxemic controls. Heart rate response was determined by infusing isoproterenol at 0.1 or 0.5 microgram.kg-1.min-1. Muscarinic receptors were quantified with [3H]quinuclidinyl benzilate and beta-adrenergic receptors with [125I]iodocyanopindolol. Competition with ICI 118,551 was used to determine beta 1- vs. beta 2-receptor subtypes. In the hypoxemic lambs, isoproterenol resulted in a lesser percentage increase in heart rate (hypoxemic, 46 +/- 6% vs. control, 89 +/- 17%, P less than 0.05); however, because baseline heart rate was higher in the hypoxemic lambs (213 +/- 7 vs. 177 +/- 12 beats/min, P less than 0.05), maximal heart rate responses were similar (310 +/- 7 vs. 326 +/- 6 beats/min, NS). There was no change in receptor density or affinity of either muscarinic or beta-adrenergic receptors and no change in the proportion of beta 1- vs. beta 2-receptor subtypes. Thus the dissociation between the chronotropic and inotropic responses to chronic hypoxemia may be in part secondary to a differential regulation of beta-adrenergic receptors between the left ventricle and the right atrium.
View details for Web of Science ID A1991GK86900023
View details for PubMedID 1656786
PEDIATRIC HEART-TRANSPLANTATION AT STANFORD - RESULTS OF A 15-YEAR EXPERIENCE
1991; 88 (2): 203-214
The long-term results of pediatric heart transplantation were evaluated in 53 patients, aged 0.25 to 18.94 years, who received transplants at Stanford University Medical Center between 1974 and 1989. Indications for transplantation were idiopathic cardiomyopathy (68%), congenital heart disease (21%), endocardial fibroelastosis (8%), and doxorubicin cardiomyopathy (3%). Immunosuppression was achieved with combinations of cyclosporine, prednisone, and azathioprine. Thirty-seven of 42 recipients leaving the hospital after transplantation were alive and in New York Heart Association class I at study's end. Cumulative survival was 79% at 1 year, 76% at 3 years, and 69% at 5 years. Fourteen recipients have survived more than 5 years (5.1 to 12.4 years). Hospital readmission for illness has been infrequent, decreasing from 6.8 days to 0.9 days per year over 5 years. Eleven patients have required no rehospitalization. Posttransplant deaths were due to infection (19%), rejection (4%), pulmonary hypertension (4%), coronary artery disease (2%), and lymphoproliferative disease (2%). Retransplantation was required for intractable rejection in 4 patients and advanced coronary artery disease in 2. Hypertension and elevated blood urea nitrogen and creatinine levels were common in individuals receiving cyclosporine. Growth was often impaired in prepubertal children receiving daily prednisone. Based on this 15-year experience, it is concluded that heart transplantation represents a reasonable alternative for selected young patients with end-stage cardiac disease.
View details for Web of Science ID A1991GA16400002
View details for PubMedID 1861916
EBSTEINS-ANOMALY APPEARING IN THE NEONATE - A NEW SURGICAL APPROACH
JOURNAL OF THORACIC AND CARDIOVASCULAR SURGERY
1991; 101 (6): 1082-1087
Ebstein's anomaly appearing during the neonatal period carries a high mortality rate. These infants exhibit cyanosis, acidosis, and congestive heart failure. The pathophysiologic characteristics consist of severe tricuspid regurgitation and functional pulmonary atresia. As a result of the inability of the right ventricle to generate forward flow through the pulmonary arteries, these infants remain dependent on ductal patency. Since May 1988, five newborn infants with severe Ebstein's anomaly have been admitted for treatment at our institution. At initial examination, they weighed 3.6 +/- 1.8 kg and had a mean oxygen tension of 29.6 +/- 2.3 mm Hg and a mean pH of 7.20 +/- 0.05. Chest roentgenography demonstrated a mean cardiothoracic ratio of 0.81 +/- 0.02. As determined by echocardiography, the right atria were massively enlarged, severe tricuspid regurgitation was present in all patients, and the pulmonary valves were not opening. All infants were dependent on prostaglandin E1 and attempts to wean them from this drug were unsuccessful. Palliative treatment consisted of tricuspid closure with autologous pericardium and an aortopulmonary shunt of 4 mm polytetrafluoroethylene tubing. There were no operative or late deaths. At discharge, mean oxygen tension was 42.2 +/- 0.85 mm Hg and mean systemic oxygen saturation was 83.2% +/- 1.94%. Infants have grown satisfactorily during the follow-up period. Three infants have since returned for further surgical intervention. One infant, at 11 months of age, underwent a Glenn anastomosis for progressive oxygen desaturation. Two infants have returned, at ages 23 and 22 months, for Fontan procedures, which represent their definitive operative management. We believe this new procedure offers excellent palliative treatment for Ebstein's anomaly in critically ill neonates. Feasibility of later definitive correction is demonstrated by the good results obtained with the Fontan procedure in two infants.
View details for Web of Science ID A1991FQ11100018
View details for PubMedID 2038202
COMPARATIVE CIRCULATORY EFFECTS OF ISOPROTERENOL AND DOPAMINE IN LAMBS WITH EXPERIMENTAL CYANOTIC HEART-DISEASE
1991; 29 (4): 323-328
To determine whether the hemodynamic responses to adrenergic agonists are altered during chronic hypoxemia secondary to an intracardiac right to left shunt, we studied seven lambs with surgically created pulmonic stenosis and atrial septal defect and nine controls during infusions of isoproterenol at 0.1 and 0.5 micrograms/kg/min and dopamine at 5 and 20 micrograms/kg/min. Isoproterenol increased heart rate by 89 +/- 17% in control but only 46 +/- 6% in experimental lambs (p less than 0.05). However, because resting heart rate was higher in experimental lambs (213 +/- 7 versus 177 +/- 12 beats/min, p less than 0.05), maximal heart rates were similar (310 +/- 7 versus 326 +/- 6 beats/min; NS). Cardiac output increased during isoproterenol from 219 +/- 20 to 425 +/- 54 mL/min/kg in experimental lambs (p less than 0.05) and, similarly, from 180 +/- 20 to 425 +/- 71 in controls (p less than 0.05) (experimental versus control; NS). Dopamine also increased cardiac output similarly in both groups, at both doses, but without changing heart rate. Isoproterenol did not alter aortic oxygen saturation and increased systemic oxygen transport more than oxygen consumption. In contrast, dopamine at both doses decreased aortic oxygen saturation in experimental lambs (rest, 71 +/- 2% versus dopamine, 59 +/- 2%; p less than 0.05). With dopamine, the increase in systemic oxygen transport was equalled by an increase in oxygen consumption. Thus, circulatory responses to isoproterenol are similar in lambs with experimental cyanotic heart disease and controls, although higher resting heart rate in the experimental lambs reduces chronotropic reserve.(ABSTRACT TRUNCATED AT 250 WORDS)
View details for Web of Science ID A1991FE03600001
View details for PubMedID 1852523
DIFFERENTIAL REGULATION OF RIGHT AND LEFT-VENTRICULAR BETA-ADRENERGIC RECEPTORS IN NEWBORN LAMBS WITH EXPERIMENTAL CYANOTIC HEART-DISEASE
JOURNAL OF CLINICAL INVESTIGATION
1990; 85 (1): 68-74
To determine whether chronic hypoxemia secondary to an intracardiac right-to-left shunt alters regulation of the myocardial beta-adrenergic receptor/adenylate cyclase system, we produced chronic hypoxemia in nine newborn lambs by creating right ventricular outflow obstruction and an atrial septal defect. Oxygen saturation was reduced to 65-74% for 2 wk. Eight lambs served as normoxemic controls. beta-receptor density (Bmax) and ligand affinity (KD) were determined with the radio-ligand [125I]iodocyanopindolol and adenylate cyclase activity determined during stimulation with isoproterenol, sodium fluoride (NaF), and forskolin. During chronic hypoxemia, Bmax decreased 45% (hypoxemic, 180.6 +/- 31.5 vs. control, 330.5 +/- 60.1 fmol/mg) in the left ventricle (exposed to hypoxemia alone) but was unchanged in the right ventricle (exposed to hypoxemia and pressure overload). KD was not different from control in either ventricle. Left ventricular isoproterenol-stimulated adenylate cyclase activity was decreased by 39% (30.0 +/- 4.3% increase vs. 44.1 +/- 9.5% increase) whereas right ventricular adenylate cyclase activity was unchanged. Stimulation of adenylate cyclase with NaF or forskolin was not different from control in either ventricle. Circulating epinephrine was increased fourfold whereas circulating and myocardial norepinephrine were unchanged. These data demonstrate a down-regulation of the left ventricular beta-adrenergic receptor/adenylate cyclase system during chronic hypoxemia secondary to an intracardiac right-to-left shunt.
View details for Web of Science ID A1990CH52200011
View details for PubMedID 2153153
Pediatric heart transplantation.
Advances in pediatrics
1990; 37: 413-439
Heart transplantation has been performed successfully in the pediatric age group for just over 10 years, yet early results are encouraging, and this procedure has moved from the realm of experimental therapy to that of accepted medical practice for certain specific conditions. In infants and children with cardiomyopathies or with congenital heart disease for which no reasonable standard surgical alternative exists, heart transplantation offers the best hope for long-term survival. Most important, in those patients surviving heart transplantation, rehabilitation has been almost universally complete. Although the long-term prospects for pediatric heart transplant patients are still unknown, we have now accumulated sufficient experience in adults suggesting the potential for decades-long survival. Future improvements in diagnosis and treatment of rejection and prevention of the complications of immunosuppressive therapy will continue to improve the prospects for lifelong survival in these patients.
View details for PubMedID 2264535
HEART-TRANSPLANTATION IN CHILDREN
JOURNAL OF HEART TRANSPLANTATION
1989; 8 (1): 20-26
Heart transplantation in children is being performed with increasing frequency. As experience has accrued, problems of rejection, graft atherosclerosis, and growth have been noted. Seventeen children (seven boys and 10 girls) between the ages of 5 months and 14 years have undergone heart transplantation since 1981. The preoperative diagnosis was cardiomyopathy in 13 children, congenital heart disease in two, and endocardial fibroelastosis in two. Immunosuppressive therapy has included a tapering schedule of cyclosporine, azathioprine, and prednisone. There are 13 children alive, with four hospital deaths (two of infection, one of rejection, and one of graft failure). Rejection occurs as frequently in children as in adults. Two children have undergone retransplantation for rejection. Long-term hemodynamics are normal. Growth has been delayed in two of five children who are younger than age 10 years. Kidney function remains stable. Rehabilitation is 100% among the discharged patients. Heart transplantation in children represents an effective therapeutic modality. Heart transplantation in the young has emphasized morbidity caused by current immunosuppressive agents.
View details for Web of Science ID A1989T169600004
View details for PubMedID 2647927
Developmental and afterload stress regulation of heat shock proteins in the ovine myocardium
INT PEDIATRIC RESEARCH FOUNDATION, INC. 1997: 51-56
Heat shock proteins (hsps) are produced in the myocardium in response to stresses such as ischemia, hyperthermia, and increased afterload. The role of these stress proteins in the developing myocardium is unknown. Expression of the inducible (hsp 72) and cognate (hsc 73) hsps was determined in the immature ovine myocardium during the perinatal transition, and their role in subsequent myocardial growth was examined. hsp synthesis was also studied during acute afterload stress in newborns by aortic banding to a gradient of 50 torr for 4 h. Expression of the inducible (hsp 72) isoform is developmentally regulated in both right and left ventricles: low levels in the fetus, increasing throughout development, and peaking in the 14-25-d newborn and adult. The cognate (hsc 73) isoform remains unchanged during development in the left ventricle but decreases with age in the right ventricle. The inducible (hsp 72) isoform is also developmentally regulated in the lung, increasing postnatally to a peak in the 14-25-d-old and adult sheep. Finally, newborn myocardium demonstrated a rapid increase in hsp expression in response to afterload stress, similar to that seen in the adult.
View details for Web of Science ID A1997VY68500008
View details for PubMedID 8979289