In my academic and scholarship endeavors, I continue to be guided by a commitment to patient care and a desire to teach, learn, and conduct research in a multifaceted and multidisciplinary field. Cardiac electrophysiology is a dynamic and innovative field, pushing at the boundaries of science and medicine; new research findings are quickly translated to the clinical setting. In this environment of active research endeavors and strong clinical growth, I have sought to bring innovative approaches, both clinical and translational, to the treatment of cardiac arrhythmias.

Clinical Interests
My clinical interests include management of complex arrhythmias through the use of medications and/or ablation technologies for all types of tachycardias, including atrial fibrillation and ventricular tachycardia; cardiac device placements such as biventricular pacemakers and defibrillators; and implantation of left atrial appendage closure devices for stroke prevention in patients with atrial fibrillation. I have a strong focus on complex ablations in patients with life-threatening arrhythmias such as ventricular tachycardia/fibrillation and in patients with complex congenital heart abnormalities.

Care Philosophy
Cardiology and electrophysiology are highly technical fields utilizing the latest and most advanced technology to deliver outstanding care. However, at the end of the day, I believe that the best care for my patients involves listening to them, informing them about their illness, involving them in their care, and always doing what is in their best interests.

Volunteer Activities
I came here as a refugee from war and have been fortunate to gain the experiences that I have had, so that I can give back to the community. I have worked in homeless shelters, taught GED and ESL, vaccinated at-risk youths from hepatitis B, and worked to treat and prevent HIV/AIDS in impoverished communities.

Clinical Focus

  • Clinical Cardiac Electrophysiology

Academic Appointments

Administrative Appointments

  • Director, Translational and Experimental EP Research Lab (2019 - Present)
  • Fellow, Stanford Faculty Biodesign (2019 - Present)

Honors & Awards

  • Advanced Industries Accelerator Grant, State of Colorado (2017-2019)
  • Platinum Reviewer Recognition Award, Circulation Arrhythmia Electrophysiology (2019)
  • Best Poster Award (senior author), American College Cardiology Scientific Sessions (2019)
  • Platinum Reviewer Recognition Award, Circulation Arrhythmia Electrophysiology (2018)
  • Bioscience Discovery Evaluation Grant, State of Colorado (2015-2017)
  • Faculty Citizenship Award, University of Colorado (2012)
  • Faculty Citizenship Award, University of Colorado (2011)
  • Outstanding Faculty Teaching Award, University of Colorado (2011)
  • F32- National Research Service Award, NHLBI, National Institutes of Health (2007-2010)
  • Laennec Young Clinician Award, Finalist, American Heart Association (2006)
  • Excellence in Teaching Award, Department of Medicine, Massachusetts General Hospital (2005)

Boards, Advisory Committees, Professional Organizations

  • Vice Chair, Heart Rhythm Society Research Committee (2016 - Present)
  • Editorial Board, Circulation: Arrhythmia and Electrophysiology (2017 - Present)
  • Fellow, American Heart Association (2019 - Present)
  • Fellow, American College of Cardiology (2010 - Present)
  • Fellow, Heart Rhythm Society (2012 - Present)
  • Member, Pediatric and Congenital Electrophysiology Society (PACES) Research Subcommittee (2018 - Present)
  • Heart Rhythm Advisory Panel, Heart Rhythm Society (2014 - 2016)

Professional Education

  • Board Certification: American Board of Internal Medicine, Adult Congenital Heart Disease (2019)
  • Board Certification, American Board of Internal Medicine, Cardiac Electrophysiology (2010)
  • Board Certification, American Board of Internal Medicine, Cardiovascular Medicine (2008)
  • Board Certification, American Board of Internal Medicine, Internal Medicine (2005)
  • Fellowship, University of California San Francisco, Cardiac Electrophysiology (2010)
  • Fellowship, Cardiovascular Research Institute and University of California San Francisco, Postdoctoral fellowship- Cardiovascular Research (2010)
  • Board Certification: American Board of Internal Medicine, Clinical Cardiac Electrophysiology (2010)
  • Fellowship, University of California San Francisco, Cardiovascular Medicine (2008)
  • Fellowship: UCSF Cardiology Fellowship (2010) CA
  • Residency, Massachusetts General Hospital and Harvard Medical School, Internal Medicine (2005)
  • Board Certification: American Board of Internal Medicine, Cardiovascular Disease (2008)
  • Internship, Massachusetts General Hospital and Harvard Medical School, Internal Medicine (2003)
  • Fellowship: UCSF Cardiology Fellowship (2008) CA
  • MD, Harvard Medical School (2002)
  • Residency: Massachusetts General Hospital Internal Medicine Residency (2005) MA
  • MA, Harvard Graduate School of Arts and Sciences, Biology (1997)
  • Medical Education: Harvard Medical School (2002) MA
  • BA, Harvard University, Biology (1997)


  • Duy Nguyen, William Sauer. "United States Patent Provisional Patent No. 16/099,108 Liposomal Magnetic Nanoparticles and Electromagnetic Ablation Catheter", University of Colorado, May 10, 2016
  • Duy Nguyen, William Sauer. "United States Patent Provisional patent No. 14/942,442 Partially Insulated Focused Radiofrequency Ablation Catheter", University of Colorado, Mar 3, 2015

Current Research and Scholarly Interests

The long-term goals of my translational research are to evaluate novel radiofrequency (RF) ablation strategies, catheter designs to improve procedural efficacy and safety outcomes, and molecular targets to enhance RF ablation of atrial fibrillation and ventricular tachycardia. We have translational and clinical studies on multiple ablation catheter designs as well as ablation strategies to improve safety and maximize RF delivery during ablation for atrial fibrillation and ventricular tachycardia. We have both in vivo and ex vivo animal models (small and large animal) of atrial and ventricular arrhythmias.

At the translational level, our ablation biophysics studies include utilizing various nanomaterials to help facilitate ablation as well as designing specialized catheters to improve safety and efficacy of ablation. We are studying specific variations in catheter design to improve ablation; testing delivery methods of facilitating agents; optimizing biophysical parameters; determining the precise RF electromagnetic field to minimize collateral damage; and studying magnetic driven facilitating agents.

At the clinical level, my research has focused on the application of biophysical principles to AF and VT ablation outcomes, in addition to research related to adult congenital heart disease. Projects include a multicenter consortium on the use of EP studies in risk stratification of sudden death for Tetralogy of Fallot (ToF) patients undergoing pulmonary valve replacement; perioperative EP studies and VT ablation in ToF patients; outcomes in multicenter cohorts of ACHD patients undergoing AF and VT ablations; and outcomes in ACHD subpopulations undergoing EP procedures, such as those with bicuspid aortic valves, right atrial myopathies, and others.

All Publications

  • Uncovering a unique path: Antidromic AVRT utilizing a Left Anteroseptal Mahaim-like accessory pathway. Pacing and clinical electrophysiology : PACE Sandhu, A., Tzou, W. S., Borne, R. T., Zipse, M. M., Nguyen, D. T., Sauer, W. H. 2020


    A 40-year old man presented to our emergency department 2 hours after onset of shortness of breath, palpitations and presyncope secondary to an adenosine-responsive wide complex tachycardia. Electrophysiology study was diagnostic for antidromic AV reentrant tachycardia (AVRT) utilizing a muscular connection from the anterior interventricular vein (AIV) to the left ventricle with Mahaim-like properties, successfully treated with ablation in the distal coronary sinus system. This case highlights accessory pathways (1) with unique features (ie. Mahaim-like characteristics) and (2) involving musculature from the distal coronary sinus system, thereby limiting the value of endocardial ablation for durable treatment. Importantly, the coronary venous system is an accessible vascular network for evaluation and catheter ablation of such arrhythmias. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/pace.14024

    View details for PubMedID 32794265

  • Patients with bicuspid aortic valves may be associated with infra-hisian conduction disease requiring pacemakers. Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing Biswas, M., Sandhu, A., Kay, J. D., Khanna, A. D., Collins, K. K., Sauer, W. H., Nguyen, D. T. 2020


    BACKGROUND: Bicuspid aortic valves (BAVs) are associated with accelerated valvular dysfunction. Increasing rates of conduction system disease are seen in patients with calcific tricuspid aortic valves (TAVs). However, little is known regarding the extent of conduction disorders in BAV patients. We sought to determine the extent of infra-hisian conduction pathology among patients with BAVs undergoing EP studies.METHODS: We prospectively analyzed patients presenting to the EP laboratory from 2006 to 2017 at our institution. Thirty-three BAV patients had measured HV intervals. Each individual was matched by age and gender to two control patients. Clinical characteristics were collected and compared, and patients followed for outcomes.RESULTS: The BAV cohort had a mean age of 47.8±17.2years (range 19-76years). Indications for referral to the EP lab in the BAV cohort included SVT ablation (n=16), VT ablation (n=10), and EP study for syncope, pre-syncope, or palpitations (n=29). Patients with BAVs had a mean HV interval of 58.7ms±18.6ms, compared to a mean of 47.2ms±9.6ms for controls (p value=0.0001). Over a 10-year follow-up period, 9 BAV patients (27%) went on to require permanent pacing compared to 6 patients (9%) in the control group (p value=0.03).CONCLUSION: Compared to patients with TAVs presenting for EP evaluation, individuals with BAVs have longer HV intervals and a significantly increased requirement for pacemaker therapy over long-term follow-up. Closer monitoring of progressive conduction system disease in BAV patients may be warranted.

    View details for DOI 10.1007/s10840-020-00785-z

    View details for PubMedID 32458178

  • Use of cell phone adapters is associated with reduction in disparities in remote monitoring of cardiac implantable electronic devices. Journal of interventional cardiac electrophysiology : an international journal of arrhythmias and pacing Mantini, N., Borne, R. T., Varosy, P. D., Rosenberg, M. A., Marzec, L. N., Sauer, W. H., Nguyen, D. T. 2020


    BACKGROUND: Remote monitoring (RM) of cardiac implantable electronic devices (CIEDs) is standard of care. However, it is underutilized. In July 2012, our institution began providing cell phone adapters (CPAs) to patients free of charge following CIED implantation to improve remote transmission (RT) adherence.METHODS: Patients in our institution's RM database from January 1, 2010, thru June 30, 2015, were retrospectively reviewed. There were 2157 eligible patients. Remote transmission proportion (RTP) and time to transmission (TT) were compared pre- and post-implementation of free CPA. Chi-squared analysis and Kruskal-Wallis tests were performed to compare RTP and TT.RESULTS: There was a significant increase in RTP (134 [18.4%] vs 99 [54.7%]; p<0.001) and decrease in median TT in days (189[110-279] vs 58 [10-149]; p<0.001) after CPAs were provided to patients. Caucasian patients were more likely than African Americans and Hispanics to use RM prior to CPAs (p=0.04). After the implementation of CPAs, there was a significant increase in RTP for all racial groups (<0.001) with no difference in RTP among racial groups (p=0.18). The RTP for urban residents was significantly greater than non-urban residents with CPAs (p=0.008). Patients greater than 70years of age were significantly less likely to participate in RT before and after CPAs were provided (p=0.03, p=0.01, respectively).CONCLUSIONS: CPAs significantly improve RTP and reduce median TT for all patients regardless of race, geographic residence, and age (>70years old to lesser extent). Broad institution of CPAs following ICD implantation could potentially reduce disparity in RTP and deserves more study.

    View details for DOI 10.1007/s10840-020-00743-9

    View details for PubMedID 32399863

  • Ablation of Supraventricular Tachycardias From Concealed Left-sided Nodoventricular And Nodofascicular Accessory Pathways. Circulation. Arrhythmia and electrophysiology Cardona-Guarache, R., Han, F. T., Nguyen, D. T., Chicos, A. B., Badhwar, N., Knight, B. P., Johnson, C. J., Heaven, D., Scheinman, M. M. 2020


    Background - Nodoventricular (NV) and nodofascicular (NF) accessory pathways (AP) are uncommon connections between the AV node and the fascicles or ventricles. Methods - Five patients with NF or NV tachycardia were studied. Results - We identified 5 patients with concealed, left-sided NV (n=4) and NF (n=1) AP. We proved the participation of AP in tachycardia by delivering His-synchronous PVCs that either delayed the subsequent atrial electrogram or terminated the tachycardia (n=3), and by observing an increase in VA interval coincident with left bundle branch block (LBBB) (n=2). The APs were not atrioventricular pathways because the septal VA interval during tachycardia was <70ms in 3, 1 had spontaneous AV dissociation, and in 1 the atria were dissociated from the circuit with atrial overdrive pacing. Entrainment from the right ventricle showed ventricular fusion in 4 out of 5 cases. A left-sided origin of the AP was suspected after failed ablation of the right inferior extension of AV node in 3 cases and by observing a VA increase with LBBB in 2 cases. The NF and 3 of the NV AP were successfully ablated from within the proximal coronary sinus (CS) guided by recorded potentials at the roof of the CS, and 1 NV AP was ablated via a transseptal approach near the CS os. Conclusions - Left-sided NF and NV AP appear to connect the ventricles with the CS musculature in the region of the CS os. Mapping and successful ablation sites can be guided by recording potentials within or near the CS os.

    View details for DOI 10.1161/CIRCEP.119.007853

    View details for PubMedID 32286853

  • Impact of Epicardial Adipose Tissue and Catheter Ablation Strategy on Biophysical Parameters and Ablation Lesion Characteristics. Journal of cardiovascular electrophysiology Zipse, M. M., Edward, J. A., Zheng, L. n., Tzou, W. S., Borne, R. T., Sauer, W. H., Nguyen, D. T. 2020


    Epicardial adipose (EA) tissue may limit effective radiofrequency ablation (RFA).We sought to evaluate lesion formation of different ablation strategies on ventricular myocardium with overlying EA.Bovine myocardium with EA was placed in a circulating saline bath in an ex vivo model. Open-irrigated (OI) RFA was performed, parallel to myocardium, over fat at 50W for variable RF durations, variable contact force, catheter configurations (unipolar RF vs. bipolar RF), and catheter irrigants (normal saline vs. half-normal saline). Ablation was also performed with a needle-tipped ablation catheter (NTAC), perpendicular to myocardium.Increasingly thick EA attenuated lesion size regardless of ablation strategy. RF applied with longer durations and increasing CF produced larger lesion volumes and deeper lesions with ablation over EA < 3 mm but was unable to produce measurable lesions when EA > 3mm. Similarly, ablation with half normal saline irrigant created slightly deeper lesions than bipolar RF and unipolar RF with normal saline as EA thickness increased, but was unable to produce measurable lesions when EA > 3mm. Of all ablation strategies, only NTAC produced effective lesion volumes when ablating over thick (>3 mm) EA.While EA attenuates lesion depth and size, relatively larger and deeper lesions can be achieved with longer RFA duration, higher CF, half normal saline irrigant, and, to a greater extent, by utilizing bipolar RF or NTAC, but only over thin adipose (<3mm). Of those catheters/strategies tested, only NTAC was able to effectively deliver RF over thick (>3mm) EA with this model. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/jce.14383

    View details for PubMedID 32031304

  • Letter in reply: Forging ahead: Update on radiofrequency ablation technology and techniques. Journal of cardiovascular electrophysiology Sandhu, A. n., Nguyen, D. T. 2020

    View details for DOI 10.1111/jce.14412

    View details for PubMedID 32141661

  • Continuous Ablation Improves Lesion Maturation Compared with Intermittent Ablation Strategies. Journal of cardiovascular electrophysiology Rogers, A. J., Borne, R. T., Ho, G. n., Sauer, W. H., Wang, P. J., Narayan, S. M., Zheng, L. n., Nguyen, D. T. 2020


    Interrupted ablation is increasingly proposed as part of high-power short duration radiofrequency ablation (RFA) strategies and may also result from loss of contact from respiratory patterns or cardiac motion.To study the extent that ablation interruption affects lesions.In ex vivo and in vivo experiments, lesion characteristics and tissue temperatures were compared between continuous (Group 1) and interrupted (Groups 2,3) RFA with equal total ablation duration and contact force. Extended duration ablation lesions were also characterized from 1 to 5 minutes.In the ex vivo study, continuous RFA (Group 1) produced larger total lesion volumes compared with each interrupted ablation lesion group (273.8±36.5 mm3 vs. 205.1±34.2 and vs. 174.3±32.3, all p<0.001). Peak temperatures for Group 1 were higher at 3mm and 5mm than Groups 2 and 3. In vivo, continuous ablation resulted in larger lesions, greater lesion depths, and higher tissue temperatures. Longer ablation durations created larger lesion volumes and increased lesion depths. However, after 3 min of ablation, the rate of lesion volume and depth formation decreased.Continuous RFA delivery resulted in larger and deeper lesions with higher tissue temperatures compared to interrupted ablation. This work may have implications for high-power short duration ablation strategies, motivates strategies to reduce variations in ablation delivery, and provides an upper limit for ablation duration beyond which power delivery has diminishing returns. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/jce.14510

    View details for PubMedID 32323395

  • Real-time Electrogram Analysis for Drivers of AtRial Fibrillation (RADAR): A Multi-Center FDA-IDE Clinical Trial of Persistent AF. Circulation. Arrhythmia and electrophysiology Choudry, S. n., Mansour, M. n., Sundaram, S. n., Nguyen, D. T., Dukkipati, S. R., Whang, W. n., Kessman, P. n., Reddy, V. Y. 2020


    Background - Pulmonary vein isolation (PVI) is insufficient to treat all patients with persistent atrial fibrillation (AF), and effective adjunctive ablation strategies are needed. Ablation of AF drivers holds promise, but current technologies to identify drivers are limited by spatial resolution. In a single-arm, first-in-human, investigator-initiated FDA IDE study, we employed a novel system for real-time, high-resolution identification of AF drivers in persistent AF. Methods - Persistent or longstanding persistent AF patients underwent ablation using the RADAR system in conjunction with a standard electroanatomical mapping system. After PVI, electrogram and spatial information was streamed and analyzed to identify driver domains to target for ablation. Results - Across 4 centers, 64 subjects were enrolled: 73% male, age 64.7±9.5 years, BMI 31.7±6.0 kg/m2, LA size 54±10 mm, with persistent/longstanding persistent AF in 53 (83%) / 11 (17%), prior AF ablation (re-do group) in 26 (41%). After 12.6 ±} 0.8 months follow-up, 68% remained AF-free off all antiarrhythmics; 74% remained AF-free and 66% remained AF/AT/AFL-free on or off antiarrhythmic drugs. AF terminated with ablation in 35 patients (55%) overall and in 23/38 (61%) of de novo ablation patients. For patients with AF termination during ablation, 82% remained AF-free and 74% AF/AT/AFL free during follow-up on or off antiarrhythmic drugs. Patients undergoing first-time ablation generally had higher rates of freedom from AF than the re-do group. Conclusions - This novel technology for panoramic mapping of AF drivers showed promising results in a persistent/long-standing persistent AF population. These data provide the scientific basis for a randomized trial. Clinical Trial Registration -; Unique Identifier: NCT03263702; IDE#G170049.

    View details for DOI 10.1161/CIRCEP.119.007825

    View details for PubMedID 31944826

  • Letter in reply: Continuous radiofrequency ablation in scar-based arrhythmia substrate. Journal of cardiovascular electrophysiology Rogers, A. J., Nguyen, D. T. 2020

    View details for DOI 10.1111/jce.14534

    View details for PubMedID 32430949

  • Direct Thrombin Inhibitors as an Alternative to Heparin During Catheter Ablation: A Multicenter Experience. JACC. Clinical electrophysiology Voskoboinik, A. n., Butcher, E. n., Sandhu, A. n., Nguyen, D. T., Tzou, W. n., Della Rocca, D. G., Natale, A. n., Zado, E. S., Marchlinski, F. E., Aguilar, M. n., Sauer, W. n., Tedrow, U. B., Gerstenfeld, E. P. 2020


    The goal of this study was to report a multicenter series of left-sided catheter ablations performed by using intravenous direct thrombin inhibitors (DTIs) as an alternative to heparin.Amidst a looming worldwide shortage of heparin, there are insufficient data to guide nonheparin-based periprocedural anticoagulation in patients undergoing catheter ablation.This study reviewed all catheter ablations at 6 institutions between 2006 and 2019 to assess the safety and efficacy of DTIs for left-sided radiofrequency catheter ablation of atrial fibrillation and ventricular tachycardia.In total, 53 patients (age 63.0 ± 9.3 years, 68% male, CHA₂DS₂-VASc [congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke/transient ischemic attack, vascular disease, age 65 to 74 years, sex category] score 2.8 ± 1.6, left ventricular ejection fraction 46 ± 15%) underwent ablation with DTIs (75% bivalirudin, 25% argatroban) due to heparin contraindication(s) (72% heparin-induced thrombocytopenia, 21% heparin allergy, 4% protamine reaction, and 4% religious reasons). The patient's usual oral anticoagulant was continued without interruption in 69%. Procedures were performed for atrial fibrillation (64%) or ventricular tachycardia/premature ventricular contractions (36%). Transseptal puncture was undertaken in 81%, and a contact force-sensing catheter was used in 70%. Vascular ultrasound was used in 71%, and femoral arterial access was gained in 36%. A bolus followed by infusion was used in all but 4 cases, and activated clotting time was monitored periprocedurally in 72%, with 32% receiving additional boluses. Procedure duration was 216 ± 116 min, and ablation time was 51 ± 22 min. No major bleeding or embolic complications were observed. Four patients had minor self-limiting bleeding complications, including a small pericardial effusion (<1 cm), a small groin hematoma, and hematuria.In this multicenter series, intravenous DTIs were safely used as an alternative to heparin for left-sided catheter ablation.

    View details for DOI 10.1016/j.jacep.2019.12.003

    View details for PubMedID 32276868

  • Electrical Storm in COVID-19. JACC. Case reports O'Brien, C. n., Ning, N. n., McAvoy, J. n., Mitchell, J. E., Kalwani, N. n., Wang, P. n., Nguyen, D. n., Reejhsinghani, R. n., Rogers, A. n., Lorenzo, J. n. 2020; 2 (9): 1256–60


    COVID-19 is a global pandemic caused by SARS-CoV-2. Infection is associated with significant morbidity and mortality. Individuals with pre-existing cardiovascular disease or evidence of myocardial injury are at risk for severe disease and death. Little is understood about the mechanisms of myocardial injury or life-threatening cardiovascular sequelae. (Level of Difficulty: Intermediate.).

    View details for DOI 10.1016/j.jaccas.2020.05.032

    View details for PubMedID 32835266

    View details for PubMedCentralID PMC7259914

  • The New Normal. JACC. Clinical electrophysiology Nguyen, D. T., Baykaner, T. n. 2020; 6 (6): 693–95

    View details for DOI 10.1016/j.jacep.2020.03.009

    View details for PubMedID 32553220

  • Patient Selection for Epicardial Ablation-Part II: The Epicardial Approach and Current Challenges Associated with Epicardial Ablation. The Journal of innovations in cardiac rhythm management Edward, J. A., Nguyen, D. T. 2019; 10 (11): 3906–12


    Since their inception, percutaneous epicardial approaches have become increasingly common in clinical practice with the advent of new technology and the growth of catheter ablation for both ventricular and supraventricular arrhythmias. In addition to identifying the arrhythmogenic foci, there remain challenges to successful epicardial ablation such as the choice of energy source, optimizing irrigation during ablation, and anatomic barriers such as epicardial fat and coronary vessels. The performance of continued translational studies to understand how each of these factors contribute to lesion formation will be essential to guide future advances in the field of epicardial ablation.

    View details for DOI 10.19102/icrm.2019.101105

    View details for PubMedID 32477711

  • Patient Selection for Epicardial Ablation-Part I: The Role of Epicardial Ablation in Various Cardiac Disease States. The Journal of innovations in cardiac rhythm management Edward, J. A., Nguyen, D. T. 2019; 10 (11): 3897–3905


    Epicardial catheter ablation is most commonly performed following unsuccessful endocardial ablation. Given the frequency of epicardial substrates in certain cardiomyopathic disease states, however, a combined endocardial-epicardial approach should be considered as a primary treatment strategy. Although epicardial ablation is primarily deployed in patients with ventricular arrhythmias, the role of epicardial approaches in supraventricular tachycardias (eg, atrial fibrillation, inappropriate sinus tachycardia, and-rarely-accessory pathways) is growing, with continued advances being made.

    View details for DOI 10.19102/icrm.2019.101104

    View details for PubMedID 32477710

  • Bipolar Radiofrequency Ablation Creates Different Lesion Characteristics Compared to Simultaneous Unipolar Ablation. Journal of cardiovascular electrophysiology Nguyen, D. T., Zheng, L., Zipse, M. M., Borne, R. T., Tzou, W. S., Fleeman, B., Sauer, W. H. 2019


    INTRODUCTION: Both bipolar and simultaneous radiofrequency ablation (bRFA, simRFA) have been used to treat thick mid-myocardial substrate as well as during circular, multipolar ablation between shorter distances.OBJECTIVES: We sought to evaluate the biophysical parameters of simRFA, sequential unipolar RFA (seqRFA), and bRFA.METHODS: Bovine myocardium was placed in a circulating saline bath. To simulate thick substrate conditions, two open-irrigated ablation catheters were oriented across from each other, with myocardium in between. Thermocouples were placed in the center, +/-2 mm, of the myocardium. Unipolar ablations were performed sequentially or simultaneously at 50W for 60 seconds and compared to bRFA using the same settings. In addition, to simulate multipolar ablation, two open-irrigated ablation catheters were oriented on the same side and perpendicular to myocardium at 1, 2, and 4 mm spacing. SimRFA were performed at 15 and 25W for 60 seconds and compared to bRFA.RESULTS: For thicker tissue, simRFA produced similar lesion volume and depth compared to bRFA but with a lesion geometry similar to seqRFA. Unlike seqRFA and simRFA, bRFA had a necrotic core spanning the myocardium. Core depths, volumes, and temperatures were significantly greater for bRFA lesions compared to simRFA or seqRFA (Figure, p < 0.001). Similar results were consistent for bRFA and simRFA at shorter spacings.CONCLUSIONS: Bipolar RFA has greater core lesion temperatures, corresponding to a denser and larger necrotic core, than either simRFA or seqRFA. This may have implications for considering the optimal strategy for deep midmyocardial substrates or during multipolar ablation. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/jce.14213

    View details for PubMedID 31588608

  • Follow-Up After CatheterAblation of Papillary Muscles and Valve Cusps. JACC. Clinical electrophysiology Edward, J. A., Zipse, M. M., Tompkins, C., Varosy, P. D., Sandhu, A., Rosenberg, M., Aleong, R., Tzou, W. S., Borne, R. T., Sauer, W. H., Nguyen, D. T. 2019; 5 (10): 1185–96


    OBJECTIVES: The goal of this study was to determine the impact of catheter ablation in the region of papillary muscles (PMs) and valvular cusps (VC) on mitral, tricuspid, or aortic valve function.BACKGROUND: Ventricular arrhythmias arising from PMs and VCs often require extensive catheter ablation. Little is known regarding the risk of valve dysfunction after radiofrequency catheter ablation of such arrhythmias.METHODS: A retrospective analysis was completed for 149 PM and VC VT/premature ventricular contraction (PVC) ablations from 2008 to 2018 at our institution. Patient and procedural details were collected for VT and PVC ablation cases involving PMs and VCs with available echocardiographic data pre-ablation and post-ablation (within 6months). Degree of valvular regurgitation (VR) was graded from 0 (none) to 4 (severe), and significant valvular dysfunction was defined as a 2+ change in VR.RESULTS: Of 149 radiofrequency catheter ablation cases, there were 84 (56%) aortic valve cusp ablations, 60 (40%) left ventricular PM ablations, and 5 (3%) right ventricular PM ablations. There were no statistically significant differences between pre-ablation and post-ablation VR severity (p=0.33). No patients had a 2+ grade change in VR severity when pre-ablation and post-ablation echocardiograms were compared. There were no significant sequelae requiring intervention in the post-ablation period. On follow-up of 36 ± 9months, for those with a change in VR, the severity had improved to baseline or remained stable.CONCLUSIONS: Despite often-times extensive ablation on and around valvular networks, risk of longstanding or permanent valvular dysfunction after VT/PVC ablation is rare.

    View details for DOI 10.1016/j.jacep.2019.07.004

    View details for PubMedID 31648744

  • Ankyrin-B dysfunction predisposes to arrhythmogenic cardiomyopathy and is amenable to therapy. The Journal of clinical investigation Roberts, J. D., Murphy, N. P., Hamilton, R. M., Lubbers, E. R., James, C. A., Kline, C. F., Gollob, M. H., Krahn, A. D., Sturm, A. C., Musa, H., El-Refaey, M., Koenig, S., Aneq, M. A., Hoorntje, E. T., Graw, S. L., Davies, R. W., Rafiq, M. A., Koopmann, T. T., Aafaqi, S., Fatah, M., Chiasson, D. A., Taylor, M. R., Simmons, S. L., Han, M., van Opbergen, C. J., Wold, L. E., Sinagra, G., Mittal, K., Tichnell, C., Murray, B., Codima, A., Nazer, B., Nguyen, D. T., Marcus, F. I., Sobriera, N., Lodder, E. M., van den Berg, M. P., Spears, D. A., Robinson, J. F., Ursell, P. C., Green, A. K., Skanes, A. C., Tang, A. S., Gardner, M. J., Hegele, R. A., van Veen, T. A., Wilde, A. A., Healey, J. S., Janssen, P. M., Mestroni, L., van Tintelen, J. P., Calkins, H., Judge, D. P., Hund, T. J., Scheinman, M. M., Mohler, P. J. 2019; 130: 3171–84


    Arrhythmogenic cardiomyopathy (ACM) is an inherited arrhythmia syndrome characterized by severe structural and electrical cardiac phenotypes, including myocardial fibrofatty replacement and sudden cardiac death. Clinical management of ACM is largely palliative, owing to an absence of therapies that target its underlying pathophysiology, which stems partially from our limited insight into the condition. Following identification of deceased ACM probands possessing ANK2 rare variants and evidence of ankyrin-B loss of function on cardiac tissue analysis, an ANK2 mouse model was found to develop dramatic structural abnormalities reflective of human ACM, including biventricular dilation, reduced ejection fraction, cardiac fibrosis, and premature death. Desmosomal structure and function appeared preserved in diseased human and murine specimens in the presence of markedly abnormal beta-catenin expression and patterning, leading to identification of a previously unknown interaction between ankyrin-B and beta-catenin. A pharmacological activator of the WNT/beta-catenin pathway, SB-216763, successfully prevented and partially reversed the murine ACM phenotypes. Our findings introduce what we believe to be a new pathway for ACM, a role of ankyrin-B in cardiac structure and signaling, a molecular link between ankyrin-B and beta-catenin, and evidence for targeted activation of the WNT/beta-catenin pathway as a potential treatment for this disease.

    View details for DOI 10.1172/JCI125538

    View details for PubMedID 31264976

  • Electrophysiologic testing for diagnostic evaluation and risk stratification in patients with suspected cardiac sarcoidosis with preserved left and right ventricular systolic function. Journal of cardiovascular electrophysiology Zipse, M. M., Tzou, W. S., Schuller, J. L., Aleong, R. G., Varosy, P. D., Tompkins, C., Borne, R. T., Tumolo, A. Z., Sandhu, A., Kim, D., Freeman, A. M., Weinberger, H. D., Maier, L. A., Sung, R. K., Nguyen, D. T., Sauer, W. H. 2019


    INTRODUCTION: While cardiac sarcoidosis (CS) carries a risk of ventricular arrhythmias (VAs) and sudden cardiac death (SCD), risk stratification of patients with CS and preserved left ventricular/right ventricular (LV/RV) systolic function remains challenging. We sought to evaluate the role of electrophysiologic testing and programmed electrical stimulation of the ventricle (EPS) in patients with suspected CS with preserved ventricular function.METHODS: One hundred twenty consecutive patients with biopsy-proven extracardiac sarcoidosis and preserved LV/RV systolic function underwent EPS. All patients had either probable CS defined by an abnormal cardiac positron emission tomography or cardiac magnetic resonance imaging, or possible CS with normal advanced imaging but abnormal echocardiogram (ECG), SAECG, Holter, or clinical factors. Patients were followed for 4.5±2.6 years for SCD and VAs.RESULTS: Seven of 120 patients (6%) had inducible ventricular tachycardia (VT) with EPS and received an implantable cardioverter defibrillator (ICD). Three patients (43%) with positive EPS later had ICD therapies for VAs. Kaplan-Meier analysis stratified by EPS demonstrated a significant difference in freedom from VAs and SCD (P=0.009), though this finding was driven entirely by patients within the cohort with probable CS (P=0.018, n=69). One patient with possible CS and negative EPS had unrecognized progression of the disease and unexplained death with evidence of CS at autopsy.CONCLUSIONS: EPS is useful in the risk stratification of patients with probable CS with preserved LV and RV function. A positive EPS was associated with VAs. While a negative EPS appeared to confer low risk, close follow-up is needed as EPS cannot predict fatal VAs related to new cardiac involvement or disease progression.

    View details for DOI 10.1111/jce.14058

    View details for PubMedID 31257683

  • Safety and outcomes of catheter ablation for atrial fibrillation in adults with congenital heart disease: A multicenter registry study HEART RHYTHM Liang, J. J., Frankel, D. S., Parikh, V., Lakkireddy, D., Mohanty, S., Burkhardt, J., Natale, A., Szilagyi, J., Gerstenfeld, E. P., Moore, J. P., Collins, K. K., Kay, J. D., Santangeli, P., Marchlinski, F. E., Sauer, W. H., Nguyen, D. T. 2019; 16 (6): 846–52


    An increasing number of adults with congenital heart disease (CHD) are undergoing catheter ablation for atrial fibrillation (AF). Data on ablation strategy and outcomes in CHD are limited. Rhythm control is often believed to be of greater importance among patients with complex CHD.The purpose of this study was to examine the safety and efficacy of AF ablation in adult patients with CHD.A multicenter retrospective analysis was performed of CHD patients undergoing AF ablation. Clinical data were collected, including AF and CHD type, procedural data, and outcomes. Patients were divided into 3 groups (simple, moderate, and severe) based on CHD complexity, as defined by the 2014 PACES/HRS (Pediatric and Congenital Electrophysiology Society/Heart Rhythm Society) consensus statement. One-year procedural success was defined as freedom from recurrent AF, off antiarrhythmic drugs (complete) or off/on previously failed antiarrhythmic drugs (partial).Overall, 84 CHD patients (mean age 51.5 ± 12.1 years; 65.5% male; 45.2% with paroxysmal AF) undergoing AF ablation (51 simple, 22 moderate, 11 severe complexity) were included. Pulmonary vein isolation was performed in 80 (95.2%), of whom 30 (35.7%) underwent pulmonary vein isolation alone. Overall, complete and complete/partial freedom was achieved at 1 year in 53.1% and 71.6%, respectively, with no significant differences between those with simple, moderate, or severe complexity. There were no major complications and 7 minor complications, and 2 patients died during follow-up.There are dramatic differences in the degree of CHD complexity among patients referred for AF ablation. When performed at experienced centers, AF ablation is safe and effective even among patients with the most complex forms of CHD.

    View details for DOI 10.1016/j.hrthm.2018.12.024

    View details for Web of Science ID 000469315800012

    View details for PubMedID 30593868

  • Ambulatory Rhythm Monitoring to Detect Late High-Grade Atrioventricular Block Following Transcatheter Aortic Valve Replacement JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY Ream, K., Sandhu, A., Valle, J., Weber, R., Kaizer, A., Wiktor, D. M., Borne, R. T., Tumolo, A. Z., Kunkel, M., Zipse, M. M., Schuller, J., Tompkins, C., Rosenberg, M., Nguyen, D. T., Cleveland, J. C., Fullerton, D., Carroll, J. D., Messenger, J., Sauer, W. H., Aleong, R. G., Tzou, W. S. 2019; 73 (20): 2538–47


    High-grade atrioventricular block (H-AVB) is a well-described in-hospital complication of transcatheter aortic valve replacement (TAVR). Delayed high-grade atrioventricular block (DH-AVB) has not been systematically studied among outpatients post-TAVR, using latest-generation TAVR technology and in the early post-TAVR discharge era.The purpose of this study was to assess utility of ambulatory event monitoring (AEM) in identifying post-TAVR DH-AVB and associated risk factors.Patients without pre-existing pacing device undergoing TAVR at the University of Colorado Hospital from October 2016 to March 2018, and who did not require permanent pacemaker implantation pre-discharge, were discharged with 30-day AEM to assess for DH-AVB (≥2 days post-TAVR). Clinical and follow-up data were collected and compared among those without incident H-AVB.Among 150 consecutive TAVR patients without a prior pacing device, 18 (12%) developed H-AVB necessitating permanent pacemaker <2 days post-TAVR, 1 died pre-discharge, and 13 declined AEM; 118 had 30-day AEM data. DH-AVB occurred in 12 (10% of AEM patients, 8% of total cohort) a median of 6 days (range 3 to 24 days) post-TAVR. DH-AVB versus non-AVB patients were more likely to have hypertension and right bundle branch block (RBBB). Sensitivity and specificity of RBBB in predicting DH-AVB was 27% and 94%, respectively.DH-AVB is an underappreciated complication of TAVR among patients without pre-procedure pacing devices, occurring at rates similar to in-hospital, acute post-TAVR H-AVB. RBBB is a risk factor for DH-AVB but has poor sensitivity, and other predictors remain unclear. In this single-center analysis, AEM was helpful in expeditious identification and treatment of 10% of post-TAVR outpatients. Prospective study is needed to clarify incidence, risk factors, and patient selection for outpatient monitoring.

    View details for DOI 10.1016/j.jacc.2019.02.068

    View details for Web of Science ID 000468283300007

    View details for PubMedID 31118148

  • Esophageal position, measured luminal temperatures, and risk of atrioesophageal fistula with atrial fibrillation ablation PACE-PACING AND CLINICAL ELECTROPHYSIOLOGY Sandhu, A., Zipse, M. M., Borne, R. T., Aleong, R. G., Tompkins, C., Schuller, J., Rosenberg, M., Varosy, P. D., Tzou, W. S., Nguyen, D. T., Sauer, W. H. 2019; 42 (4): 458–63


    Despite improvement in catheter ablation for atrial fibrillation (AF), ability to recognize and prevent esophageal injury remains challenging. We hypothesized that esophageal course may impact esophageal heating, as measured through ablation, and thereby, risk of injury.We evaluated all patients undergoing first-time AF ablation with preprocedural computed tomography (CT) imaging from 2014 to 2016 at our institution, focusing on esophageal position at the left atrial (LA)/pulmonary vein junction. Esophageal luminal temperatures (ELTs) were analyzed by esophageal course. In exploratory work by investigation of published reports of atrioesophageal fistula (AEF), we evaluated for a relationship between esophageal course and risk of AEF.Of 68 patients, 48.5% had midline, 36.8% leftward, and 14.7% rightward esophageal positions. Of 20 patients (29% of cohort) with esophageal confinement-defined as a midline or leftward position relative to the LA, vertebrae, and aorta, with luminal distortion-14 had leftward position. No significant differences in patient or procedure characteristics were noted between confinement and nonconfinement cohorts. The average peak ELT was significantly higher in those with confinement (36.9°C vs 36.2°C, P < 0.05) and confinement with a left-sided esophagus (37.1°C vs 36.2°C, P < 0.05). There was a significant correlation between esophageal confinement and risk of AEF (odds ratio [OR]: 2.7, 95% confidence interval [CI]: 1.2-6.2, P < 0.01).Approximately one-third of patients undergoing AF ablation display leftward esophageal course along the ablation zone on preprocedure CT imaging, with a significant portion exhibiting esophageal confinement. In those with confinement, higher peak ELTs are noted with ablation. Esophageal confinement may be a risk factor for development of AEF.

    View details for DOI 10.1111/pace.13639

    View details for Web of Science ID 000462873900009

    View details for PubMedID 30779183

  • ABLATION FOR MANAGEMENT OF VENTRICULAR TACHYCARDIA IN PATIENTS WITH SEVERE HEART FAILURE IS ASSOCIATED WITH LOWER INCIDENCE OF HEART FAILURE READMISSIONS COMPARED TO MEDICAL THERAPY ALONE Beck, N., Sauer, P., Tumolo, A., Sandhu, A., Zipse, M., Borne, R., Nguyen, D., Schuller, J., Aleong, R., Tompkins, C., Varosy, P., Rosenberg, M., Khazanie, P., Altman, N., Brieke, A., Cornwell, W., Wolfel, E., Ambardekar, A., Allen, L., Tzou, W. S. ELSEVIER SCIENCE INC. 2019: 456
  • ABLATION OF VENTRICULAR TACHYCARDIA IN PATIENTS WITH SEVERE HEART FAILURE IS ASSOCIATED WITH LOWER VENTRICULAR TACHYCARDIA RECURRENCE, MORTALITY, OR HEART FAILURE READMISSION COMPARED TO MEDICAL THERAPY ALONE Beck, N., Sauer, P., Tumolo, A., Sandhu, A., Zipse, M., Borne, R., Nguyen, D., Schuller, J., Aleong, R., Tompkins, C., Varosy, P., Rosenberg, M., Khazanie, P., Altman, N., Brieke, A., Cornwell, W., Wolfel, E., Ambardekar, A., Allen, L., Tzou, W. S. ELSEVIER SCIENCE INC. 2019: 455
  • Use of half-normal saline irrigant with cooled radiofrequency ablation within the great cardiac vein to ablate premature ventricular contractions arising from the left ventricular summit PACE-PACING AND CLINICAL ELECTROPHYSIOLOGY Sandhu, A., Schuller, J. L., Tzou, W. S., Tumolo, A. Z., Sauer, W. H., Nguyen, D. T. 2019; 42 (3): 301–5


    A 62-year-old man was referred to our institution for high-density, symptomatic premature ventricular contractions (PVCs) with resultant decrease in left ventricular (LV) function having failed prior ablation attempts. Successful, durable ablation of the patient's mid-myocardial PVC arising from the LV summit region was achieved through the proximal great cardiac vein with ablation depth augmented by use of half-normal saline irrigant. Though standard ablation of ventricular arrhythmias using normal saline irrigation from the coronary venous system has been well-reported, this may be of limited value in addressing mid-myocardial sites of origin. This novel case describes the safe use of cooled radiofrequency ablation with use of half-normal saline irrigant from the distal coronary sinus as an option to address complex sites of PVC origin such as the LV summit.

    View details for DOI 10.1111/pace.13527

    View details for Web of Science ID 000460951100002

    View details for PubMedID 30341919

  • Successful ablation of ventricular tachycardia arising from a midmyocardial septal outflow tract site utilizing a simplified bipolar ablation setup. HeartRhythm case reports Sauer, P. J., Kunkel, M. J., Nguyen, D. T., Davies, A., Lane, C., Tzou, W. S. 2019; 5 (2): 105–8

    View details for DOI 10.1016/j.hrcr.2018.11.002

    View details for PubMedID 30820408

  • Long term follow-up after ventricular tachycardia ablation in patients with congenital heart disease. Journal of cardiovascular electrophysiology Yang, J. n., Brunnquell, M. n., Liang, J. J., Callans, D. J., Garcia, F. C., Lin, D. n., Frankel, D. S., Kay, J. n., Marchlinski, F. E., Tzou, W. n., Sauer, W. H., Liu, B. n., Ruckdeschel, E. S., Collins, K. n., Santangeli, P. n., Nguyen, D. T. 2019


    Ventricular tachycardia (VT) is frequently encountered in patients with repaired and unrepaired congenital heart disease (CHD), causing significant morbidity and sudden cardiac death. Data regarding underlying VT mechanisms and optimal ablation strategies in these patients remain limited.To describe the electrophysiologic mechanisms, ablation strategies, and long-term outcomes in patients with CHD undergoing VT ablation.Forty-eight patients (mean age 41.3 ± 13.3 years, 77.1% male) with CHD underwent a total of 57 VT ablation procedures at two centers from 2000 to 2017. Electrophysiologic and follow-up data were analyzed.Of the 77 different VTs induced at initial or repeat ablation, the underlying mechanism in 62 (81.0%) was due to scar-related re-entry; the remaining included four His-Purkinje system-related macrore-entry VTs and focal VTs mainly originating from the outflow tract region (8 of 11, 72.7%). VT-free survival after a single procedure was 72.9% (35 of 48) at a median follow-up of 53 months. VT-free survival after multiple procedures was 85.4% (41 of 48) at a median follow-up of 52 months. There were no major complications. Three patients died during the follow-up period from nonarrhythmic causes, including heart failure and cardiac surgery complication.While scar-related re-entry is the most common VT mechanism in patients with CHD, importantly, nonscar-related VT may also be present. In experienced tertiary care centers, ablation of both scar-related and nonscar-related VT in patients with CHD is safe, feasible, and effective over long-term follow-up.

    View details for DOI 10.1111/jce.13996

    View details for PubMedID 31111602

  • Forging Ahead: Update on Radiofrequency Ablation Technology and Techniques. Journal of cardiovascular electrophysiology Sandhu, A. n., Nguyen, D. T. 2019


    Innovations in radiofrequency ablation and non-ablative techniques have led to significant advances in addressing complex arrhythmogenic substrates for a variety of cardiac arrhythmias. Anatomical challenges, deep substrate and mid-myocardial locations may pose difficulties and decrease success rates using routine methods. In this review, we provide an update on novel radiofrequency technology and techniques including (1) high power, low duration ablation, (2) ablation facilitated by low-ionic irrigant and (3) bipolar ablation. In addition, we review emerging technologies including electroporation, needle catheter ablation and ablation with the lattice catheter. This article is protected by copyright. All rights reserved.

    View details for DOI 10.1111/jce.14317

    View details for PubMedID 31828880

  • Narrowing the Field: Closely Spaced Bipoles for Enhanced Detection of Low Voltage EGM. JACC. Clinical electrophysiology Nguyen, D. T., Tumolo, A. Z. 2019; 5 (1): 78–80

    View details for DOI 10.1016/j.jacep.2018.09.017

    View details for PubMedID 30678789

  • Moving the Needle: Tissue Characterization and Lesion Formation During Infusion-Needle Ablation. Heart rhythm Nguyen, D. T., Narayan, S. M. 2019

    View details for DOI 10.1016/j.hrthm.2019.10.018

    View details for PubMedID 31614225

  • VT arising from sub-aortic muscular outflow tract structures: In two patients with ventricular septal defects. Pacing and clinical electrophysiology : PACE Chang, S. n., Marzec, L. n., Kay, J. n., Khanna, A. n., Sauer, W. H., Nguyen, D. T. 2019; 42 (8): 1155–57


    Outflow tract ventricular tachycardias (OTVT) most commonly occur in the absence of structural abnormalities. We present two cases in which a structural variant in the outflow tract was critical to the OTVT.Subaortic muscular bands were identified using intracardiac echocardiography (ICE) in each of our cases with history of VSD and VT. Mapping demonstrating their critical involvement to the tachycardia and ablation along the muscular bands rendered the ventricular tachycardias non-inducible.In rare instances, a structural variant may be involved in OTVTs. The use of ICE along with electroanatomic mapping can assist in successful ablation of these ventricular tachycardias.

    View details for DOI 10.1111/pace.13688

    View details for PubMedID 30945754

  • Ablation of atrial arrhythmias in patients with cardiogenic shock on mechanical circulatory support. HeartRhythm case reports Mantini, N. n., Zipse, M. n., Tompkins, C. n., Varosy, P. D., Sauer, W. H., Nguyen, D. T. 2019; 5 (3): 115–19

    View details for DOI 10.1016/j.hrcr.2018.11.008

    View details for PubMedID 30891405

    View details for PubMedCentralID PMC6404096

  • Wearable Cardioverter-Defibrillator after Myocardial Infarction NEW ENGLAND JOURNAL OF MEDICINE Olgin, J. E., Pletcher, M. J., Vittinghoff, E., Wranicz, J., Malik, R., Morin, D. P., Zweibel, S., Buxton, A. E., Elayi, C. S., Chung, E. H., Rashba, E., Borggrefe, M., Hue, T. F., Maguire, C., Lin, F., Simon, J. A., Hulley, S., Lee, B. K., VEST Investigators 2018; 379 (13): 1205–15


    Despite the high rate of sudden death after myocardial infarction among patients with a low ejection fraction, implantable cardioverter-defibrillators are contraindicated until 40 to 90 days after myocardial infarction. Whether a wearable cardioverter-defibrillator would reduce the incidence of sudden death during this high-risk period is unclear.We randomly assigned (in a 2:1 ratio) patients with acute myocardial infarction and an ejection fraction of 35% or less to receive a wearable cardioverter-defibrillator plus guideline-directed therapy (the device group) or to receive only guideline-directed therapy (the control group). The primary outcome was the composite of sudden death or death from ventricular tachyarrhythmia at 90 days (arrhythmic death). Secondary outcomes included death from any cause and nonarrhythmic death.Of 2302 participants, 1524 were randomly assigned to the device group and 778 to the control group. Participants in the device group wore the device for a median of 18.0 hours per day (interquartile range, 3.8 to 22.7). Arrhythmic death occurred in 1.6% of the participants in the device group and in 2.4% of those in the control group (relative risk, 0.67; 95% confidence interval [CI], 0.37 to 1.21; P=0.18). Death from any cause occurred in 3.1% of the participants in the device group and in 4.9% of those in the control group (relative risk, 0.64; 95% CI, 0.43 to 0.98; uncorrected P=0.04), and nonarrhythmic death in 1.4% and 2.2%, respectively (relative risk, 0.63; 95% CI, 0.33 to 1.19; uncorrected P=0.15). Of the 48 participants in the device group who died, 12 were wearing the device at the time of death. A total of 20 participants in the device group (1.3%) received an appropriate shock, and 9 (0.6%) received an inappropriate shock.Among patients with a recent myocardial infarction and an ejection fraction of 35% or less, the wearable cardioverter-defibrillator did not lead to a significantly lower rate of the primary outcome of arrhythmic death than control. (Funded by the National Institutes of Health and Zoll Medical; VEST number, NCT01446965 .).

    View details for DOI 10.1056/NEJMoa1800781

    View details for Web of Science ID 000445835100005

    View details for PubMedID 30280654

    View details for PubMedCentralID PMC6276371

  • Heart Block After Discharge in Patients Undergoing TAVR With Latest-Generation Valves JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY Sandhu, A., Tzou, W., Ream, K., Valle, J., Tompkins, C., Nguyen, D. T., Sauer, W. H., Carroll, J. D., Messenger, J., Aleong, R. G. 2018; 71 (5): 577–78

    View details for DOI 10.1016/j.jacc.2017.11.057

    View details for Web of Science ID 000423996800014

    View details for PubMedID 29406864

  • Red Alert Infrared Thermography for Esophageal Monitoring CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY Borne, R. T., Nguyen, D. T. 2018; 11 (2): e006113

    View details for DOI 10.1161/CIRCEP.118.006113

    View details for Web of Science ID 000425356600013

    View details for PubMedID 29449355

  • Prospective Multicenter Experience With Cooled Radiofrequency Ablation Using High Impedance Irrigant to Target Deep Myocardial Substrate Refractory to Standard Ablation. JACC. Clinical electrophysiology Nguyen, D. T., Tzou, W. S., Sandhu, A. n., Gianni, C. n., Anter, E. n., Tung, R. n., Valderrábano, M. n., Hranitzky, P. n., Soeijma, K. n., Saenz, L. n., Garcia, F. C., Tedrow, U. B., Miller, J. M., Gerstenfeld, E. P., Burkhardt, J. D., Natale, A. n., Sauer, W. H. 2018; 4 (9): 1176–85


    This study sought to evaluate the efficacy and safety of using half-normal saline (HNS) as the cooling radiofrequency ablation (RFA) irrigant among patients who had failed prior, standard RFA.Effective control of ventricular arrhythmias that arise from mid-myocardium may be refractory to standard RFA. Recent data suggest that delivering fluid with decreased ionic concentration during open-irrigated RFA can produce deeper RFA lesions.A 12-center prospective analysis was performed of all ablations using HNS for the treatment of ventricular arrhythmias (premature ventricular complex [PVC]/ventricular tachycardia [VT]) refractory to standard ablation with normal saline irrigant.HNS RFA was used clinically to target 94 PVC/VTs refractory to standard ablation. Acute success was achieved in 78 of 94 (83%), with longer-term success occurring in 78 subjects after a mean follow-up of 6.1 ± 6.7 months (range, 3.0 to 25.2 months). Steam pops were observed among 12 (12.6%) patients. There were no significant changes in electrolytes measured before and after the use of HNS, and there were no complications related to HNS use.The use of HNS instead of normal saline irrigant during high-power delivery targeting deep myocardial substrate is safe and effective. PVC/VT sources previously unaffected by standard ablation may be successfully ablated with improved efficiency of radiofrequency delivery using HNS.

    View details for DOI 10.1016/j.jacep.2018.06.021

    View details for PubMedID 30236391

  • Perioperative electrophysiology study in patients with tetralogy of Fallot undergoing pulmonary valve replacement will identify those at high risk of subsequent ventricular tachycardia. Heart rhythm Sandhu, A. n., Ruckdeschel, E. n., Sauer, W. H., Collins, K. K., Kay, J. D., Khanna, A. n., Jaggers, J. n., Campbell, D. n., Mitchell, M. n., Nguyen, D. T. 2018; 15 (5): 679–85


    Ventricular tachyarrhythmias are the most common cause of death in patients with repaired tetralogy of Fallot (TOF), but predicting those at risk remains a challenge. An electrophysiology study (EPS) has been proposed to risk stratify patients with TOF.We sought to evaluate a perioperative EPS-guided approach to risk stratify patients with TOF undergoing pulmonary valve replacement (PVR) and guide concomitant cryoablation.A prospective cohort study of patients with TOF undergoing an EPS at the time of PVR from 2006 to 2017 was conducted at 2 centers. Patients inducible at the time of pre-PVR had undergone concomitant cryoablation in addition to PVR. A repeat post-PVR EPS was performed in those initially inducible to guide implantable cardioverter-defibrillator (ICD) implantation.Of 70 patients who underwent a pre-PVR EPS, 34 (49%) had inducible sustained ventricular tachycardia (VT): 25 monomorphic VT and 9 polymorphic VT. Among patients undergoing cryoablation, 14 (45%) had inducible VT and underwent ICD implantation. During a mean follow-up period of 6.1 ± 3.2 years, 3 patients (21%) had appropriate ICD shocks for symptomatic VT. There was an average of 2.3 shocks (range 1-4 shocks), and the mean time to first shock post-device implantation was 3.6 years (range 2.9-4.3 years). Among patients with negative pre- or post-PVR EPS results, 2 had VT requiring radiofrequency ablation and/or subsequent ICD implantation. There were no arrhythmic deaths.A pre-PVR EPS identified patients with higher-risk TOF undergoing PVR. Despite empirical VT cryoablation at the time of PVR, a high percentage of patients remained inducible for VT. In this high-risk cohort, post-PVR EPS evaluation is important to identify patients at risk of VT despite cryoablation.

    View details for DOI 10.1016/j.hrthm.2018.01.020

    View details for PubMedID 29330130

  • Successful atrial fibrillation ablation without pulmonary vein isolation utilizing focal impulse and rotor mapping in an atriopulmonary Fontan. HeartRhythm case reports Kollengode, M. n., Mathew, J. n., Yeung, E. n., Sauer, W. H., Nguyen, D. T. 2018; 4 (6): 241–46

    View details for DOI 10.1016/j.hrcr.2018.02.009

    View details for PubMedID 29922583

    View details for PubMedCentralID PMC6006488

  • Longer Duration Versus Increasing Power During Radiofrequency Ablation Yields Different Ablation Lesion Characteristics. JACC. Clinical electrophysiology Borne, R. T., Sauer, W. H., Zipse, M. M., Zheng, L. n., Tzou, W. n., Nguyen, D. T. 2018; 4 (7): 902–8


    The goal of this study was to characterize differences in ablation lesions with varying radiofrequency ablation (RFA) power and time.Increasing power delivery or prolonging duration can improve the efficacy of RFA. However, the extent to which ablation lesion characteristics change, based on varying degrees of power and duration, is unknown.An ex vivo model consisting of viable bovine myocardium in a circulating warmed saline bath was used. An open irrigated RFA catheter was positioned with 10 g of force in the perpendicular position, and RFA was delivered at powers of 20, 30, 40, and 50 W and for various time intervals, up to a total of 90 s, at each power. An in vivo porcine thigh preparation model was used to perform RFA at 50 W for 5 s and 20 W for 30 s. Lesion volumes were analyzed.Greater power delivery and longer radiofrequency time increased ablation lesion size. However, compared with a proportional change in radiofrequency duration, the same proportional increase in power produced a significantly larger lesion volume (p < 0.01). For in vivo models, 50 W/5 s ablation lesions yielded similar volumes but significantly less depth than 20 W/30 s ablation lesions. Peak temperatures were not significantly different at 2 and 4 mm with 50 W/5 s versus 20 W/30 s.Varying power and duration will confer different ablation lesion characteristics that can be tailored according to the substrate/anatomy that is being ablated. This phenomenon has important implications during catheter ablation.

    View details for DOI 10.1016/j.jacep.2018.03.020

    View details for PubMedID 30025690

  • Repeat ablation of refractory ventricular arrhythmias in patients with nonischemic cardiomyopathy: Impact of midmyocardial substrate and role of adjunctive ablation techniques. Journal of cardiovascular electrophysiology Tzou, W. S., Rothstein, P. A., Cowherd, M. n., Zipse, M. M., Tompkins, C. n., Marzec, L. n., Aleong, R. G., Schuller, J. L., Varosy, P. D., Borne, R. T., Mathew, J. n., Tumolo, A. n., Sandhu, A. n., Nguyen, D. T., Sauer, W. H. 2018; 29 (10): 1403–12


    Multiple ablations are often necessary to manage ventricular arrhythmias (VAs) in nonischemic cardiomyopathy (NICM) patients. We assessed characteristics and outcomes and role of adjunctive, nonstandard ablation in repeat VA ablation (RAbl) in NICM.Consecutive NICM patients undergoing RAbl were analyzed, with characteristics of the last VA ablations compared between those undergoing 1 versus multiple-repeat ablations (1-RAbl vs. >1RAbl), and between those with or without midmyocardial substrate (MMS). VA-free survival was compared. Eighty-eight patients underwent 124 RAbl, 26 with > 1RAbl, and 26 with MMS. 1-RAbl and > 1-RAbl groups were similar in age (57 ± 16 vs. 57 ± 17 years; P = 0.92), males (76% vs. 69%; P = 0.60), LVEF (40 ± 17% vs. 40 ± 18%; P = 0.96), and amiodarone use (31% vs. 46%, P = 0.22). One-year VA freedom between 1-RAbl vs. > 1RAbl was similar (82% vs. 80%; P = 0.81); adjunctive ablation was utilized more in >1RAbl (31% vs. 11%, P = 0.02), and complication rates were higher (27% vs. 7%, P = 0.01), most due to septal substrate and anticipated heart block. >1-RAbl patients had more MMS (62% vs. 16%, P < 0.01). Although MMS was associated with worse VA-free survival after 1-RAbl (43% vs. 69%, P = 0.01), when >1RAbl was performed, more often with nonstandard ablation, VA-free survival was comparable to non-MMS patients (85% vs. 81%; P = 0.69). More RAbls were required in MMS versus non-MMS patients (2.00 ± 0.98 vs. 1.16 ± 0.37; P < 0.001).For NICM patients with recurrent, refractory VAs despite previous ablation, effective arrhythmia control can safely be achieved with subsequent ablation, although >1 repeat procedure with adjunctive ablation is often required, especially with MMS.

    View details for DOI 10.1111/jce.13663

    View details for PubMedID 30033528

  • Use of Tissue Electric and Ultrasound Characteristics to Predict and Prevent Steam-Generated Cavitation During High-Power Radiofrequency Ablation. JACC. Clinical electrophysiology Nguyen, D. T., Zipse, M. n., Borne, R. T., Zheng, L. n., Tzou, W. S., Sauer, W. H. 2018; 4 (4): 491–500


    Given a paucity of data, the aim of this study was to define predictors of steam pops (SPs) during open-irrigated radiofrequency ablation (RFA).SPs during RFA can lead to dire consequences, including perforation and stroke.In an ex vivo bovine myocardium model, open-irrigated RFA was applied at 50 W for 60 s; intracardiac echocardiographic images for RFA with and without SPs was compared. Using an in vivo porcine model, open-irrigated RFA was applied at 50 W for 60 s, and RFA parameters of SPs were analyzed. A retrospective analysis was performed of recorded SPs during clinical ablation procedures over a 1-year period.For RFA SPs, there was 32% greater intracardiac echocardiographic tissue echogenicity than for RFA without SPs (p < 0.001). In addition, RFA SPs had more rapid increases of tissue echogenicity, particularly in the last 5 s before SPs. Compared with RFA without SPs, RFA SPs had larger impedance reductions (33.0 ± 16.0 Ω vs. 23.0 ± 10.8 Ω; p = 0.032). SPs were also associated with more rapid initial impedance reduction (1.40 Ω/s vs. 0.38 Ω/s for RFA without SPs; p = 0.001). Clinical SPs during ablation procedures had a significantly faster impedance reduction during the first 5 s of ablation compared with matched control ablations (15.7 ± 6.7 Ω vs. 8.1 ± 4.7 Ω; p < 0.0001).Certain echocardiographic and biophysical parameters during open-irrigated RFA are associated with increased SP risks. These include greater tissue echogenicity, larger total impedance reduction, rapid rate of initial impedance reduction, and rapid increase in tissue echogenicity.

    View details for DOI 10.1016/j.jacep.2017.10.003

    View details for PubMedID 30067489

  • Effect of Environmental Impedance Surrounding a Radiofrequency Ablation Catheter Electrode on Lesion Characteristics Journal of cardiovascular electrophysiology Nguyen, D. T., Lijun, Z. n., Joseph, S. n., Zipse, M. n., Tzou, W. S., Sauer, W. H. 2018; 28 (5)

    View details for DOI 10.1111/jce.13185

    View details for PubMedID 30525336

  • Near-Field Ultrasound Imaging of Ablation Lesion Formation More Than Meets the Eye? CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY Zipse, M. M., Nguyen, D. T. 2017; 10 (12)

    View details for DOI 10.1161/CIRCEP.117.006010

    View details for Web of Science ID 000418461100015

    View details for PubMedID 29242237

  • Circulation of Cooled Saline Protects Adjacent, Nontargeted Tissues During Radiofrequency Ablation Nguyen, D. T., Zheng, L., Tzou, W., Zipse, M., Sauer, W. WILEY. 2017: 577–78
  • SAFETY AND OUTCOMES OF CATHETER ABLATION FOR TREATMENT OF REFRACTORY VENTRICULAR ARRHYTHMIAS IN PATIENTS WITH ADVANCED HEART FAILURE Cowherd, M., Rothstein, P., Tumolo, A., Altman, N., Khazanie, P., Ambardekar, A., Brieke, A., Wolfel, E., Cornwell, W., Zipse, M., Nguyen, D., Marzec, L., Aleong, R., Tompkins, C., Allen, L., Sauer, W., Tzou, W. ELSEVIER SCIENCE INC. 2017: 535
  • Radiofrequency Ablation Using an Open Irrigated Electrode Cooled With Half-Normal Saline. JACC. Clinical electrophysiology Nguyen, D. T., Gerstenfeld, E. P., Tzou, W. S., Jurgens, P. T., Zheng, L. n., Schuller, J. n., Zipse, M. n., Sauer, W. H. 2017; 3 (10): 1103–10


    This study evaluated the use of half-normal saline (HNS) as the radiofrequency ablation (RFA) cooling irrigant.Some instances of ventricular arrhythmia may originate deep within myocardium and can be refractory to standard ablation using open irrigated RFA. Recent data suggest that deeper ablation lesions can be created by decreasing the irrigant ionic concentration delivered through open irrigated RFA than by using normal saline (NS).Bovine myocardium was placed in a circulating saline bath. Two RFA catheters were oriented across from each other, with myocardium in between. Sequential unipolar HNS-irrigated RFA was performed and compared to bipolar ablation by using NS or HNS. Unipolar HNS ablation of the ventricles in a porcine model was performed and compared to ablation using NS.Sequential ex vivo unipolar RFA with HNS produced larger lesions than sequential unipolar RFA with NS and produced lesions of similar size to those created with bipolar RFA using NS. Ex vivo bipolar RFA using HNS created the largest lesions. In vivo unipolar HNS ablation in porcine endocardium created larger lesion volumes, 152.9 ± 29.2 μl, compared to 94.7 ± 33.4 μl for unipolar ablation using NS.By decreasing ionic concentration and charge density in RFA using HNS instead of NS irrigant, larger ablation lesions can be created and are similar in size to lesions created using bipolar ablation. This may be a useful ablation strategy for deep myocardial circuits refractory to standard ablation. Further studies are needed to evaluate this novel RFA strategy.

    View details for DOI 10.1016/j.jacep.2017.03.006

    View details for PubMedID 29759492

  • Spectrum of Cardiac Arrhythmias in Isolated Ventricular Non-Compaction. The Journal of innovations in cardiac rhythm management Tumolo, A. Z., Nguyen, D. T. 2017; 8 (7): 2774–83


    A wide spectrum of cardiac arrhythmias has been observed in patients with isolated ventricular non-compaction, which is defined by hypertrabeculated ventricular myocardium with deep intertrabecular recesses, in the absence of concomitant congenital heart disease. In this genetically diverse phenotype, the development of fibrosis contributes to an arrhythmogenic substrate underlying atrioventricular conduction diseases, supraventricular tachycardias and ventricular tachycardias. Within this spectrum, monomorphic ventricular tachycardia is the most frequently observed arrhythmia, and this prevalence has important implications for sudden cardiac death risk.

    View details for DOI 10.19102/icrm.2017.080701

    View details for PubMedID 32494459

    View details for PubMedCentralID PMC7252917

  • Noninvasive Predictors of Ventricular Arrhythmias in Patients With Tetralogy of Fallot Undergoing Pulmonary Valve Replacement. JACC. Clinical electrophysiology Cortez, D. n., Barham, W. n., Ruckdeschel, E. n., Sharma, N. n., McCanta, A. C., von Alvensleben, J. n., Sauer, W. H., Collins, K. K., Kay, J. n., Patel, S. n., Nguyen, D. T. 2017; 3 (2): 162–70


    This study sought to test the hypothesis that a vectorcardiographic parameter, the QRS vector magnitude (QRSVm), can risk stratify those patients at risk for sustained spontaneous ventricular arrhythmias (VAs) or ventricular arrhythmia inducibility (VAI) in a large cohort of patients with tetralogy of Fallot (TOF).Patients with TOF have an increased risk of VAs, but predicting those at risk can often be challenging.Blinded retrospective analyses of 177 TOF patients undergoing pulmonary valve replacement (PVR) between 1997 and 2015 were performed. VAI was evaluated by programmed electrical stimulation in 48 patients. QRS intervals and QRSVm voltage measurements were assessed from resting 12-lead electrocardiograms, and risk of VA was determined. Clinical characteristics, including imaging and cardiac catheterizations, were used for other modality comparisons.Sustained spontaneous VA occurred in 12 patients and inducible VA in 18 patients. Age and QRSVm were significant univariate predictors of VA. QRSVm was the only independent predictor of VAI (p < 0.001). Using a root mean square QRS value of 1.24 mV, the positive and negative predictive values were 47.9% and 97.8%, respectively, for spontaneous sustained VA. For VAI, using a QRSVm cutoff of 1.31 mV, positive and negative predictive values were 63.0% and 95.3%, respectively.In TOF patients undergoing PVR, older age was associated with increased spontaneous VA risk. Lower QRSVm predicted spontaneous VA or VAI risk with high negative predictive values. QRSVm is the only independent predictor of VAI. These clinical features may help further risk stratify TOF patients requiring therapies to prevent sudden death.

    View details for DOI 10.1016/j.jacep.2016.08.007

    View details for PubMedID 29759389

  • Noninvasive predictors of perioperative atrial arrhythmias in patients with tetralogy of Fallot undergoing pulmonary valve replacement. Clinical cardiology Cortez, D. n., Barham, W. n., Ruckdeschel, E. n., Sharma, N. n., McCanta, A. C., von Alvensleben, J. n., Sauer, W. H., Collins, K. K., Kay, J. n., Patel, S. n., Nguyen, D. T. 2017; 40 (8): 591–96


    Patients with tetralogy of Fallot (TOF) have increased risk of atrial arrhythmias.A measure of atrial dispersion, the P-wave vector magnitude (Pvm), can identify patients at risk for perioperative atrial flutter (AFL) or intra-atrial re-entrant tachycardia (IART) in a large TOF cohort.We performed a blinded, retrospective analysis of 158 TOF patients undergoing pulmonary valve replacement between 1997 and 2015. History of AFL/IART was documented using electrocardiogram, Holter monitor, exercise stress test, implanted cardiac device, and electrophysiology study. P-R intervals, Pvm, QRS duration, and QRS vector magnitude were assessed from resting sinus-rhythm 12-lead electrocardiograms and identification of those with AFL/IART was determined.Fourteen patients (8.9%) were found to have AFL/IART. Pvm, QRS duration, and QRS vector magnitude significantly differentiated those with AFL/IART from those without on univariate analysis: 0.09 ± 0.04 vs 0.18 ± 0.07 mV, 161.3 ± 21.9 vs 137.7 ± 31.4 ms, and 1.2 (interquartile range, 1.0-1.2) vs 1.6 mV (1.0-2.3), respectively (P < 0.05 for each). The Pvm had the highest area under the ROC curve (0.88) and was the only significant predictor on multivariate analysis, with odds ratio of 0.02 (95% confidence interval: 0.01-0.53). P-R duration, MRI volumes, and right-heart hemodynamics did not significantly differentiate those with vs those without AFL/IART.In TOF patients undergoing pulmonary valve replacement, Pvm has significant value in predicting those with perioperative AFL/IART. These clinical features may help further evaluate TOF patients at risk for perioperative atrial arrhythmias. Prospective studies are warranted.

    View details for DOI 10.1002/clc.22707

    View details for PubMedID 28394443

  • Slow Pathway Modification in a Patient with D-Transposition of the Great Arteries and Atrial Switch Procedure. Cardiac electrophysiology clinics Ruckdeschel, E. S., Kay, J., Varosy, P., Nguyen, D. T. 2016; 8 (1): 191–96


    Patients with systemic right ventricles are often not able to tolerate frequent, rapid, or incessant atrial arrhythmias without developing significant symptoms and ventricular dysfunction. Atrial arrhythmias are associated with an increased risk of ventricular arrhythmias and sudden cardiac death. Rhythm disturbances must be aggressively addressed in this population with frequent screening, follow-up, and treatment.

    View details for DOI 10.1016/j.ccep.2015.10.027

    View details for PubMedID 26920193

  • Intra-atrial Reentrant Tachycardia in Complete Transposition of the Great Arteries Without Femoral Venous Access. Cardiac electrophysiology clinics Borne, R. T., Kay, J., Fagan, T., Nguyen, D. T. 2016; 8 (1): 197–200


    Catheter ablation for patients with transposition of the great arteries (d-TGA) requires multiple considerations and careful preprocedural planning. Knowledge of the patient's anatomy and surgical correction, in addition to electroanatomic mapping and entrainment maneuvers, are important to identify and successfully treat arrhythmias. This case was unique in that the lack of femoral venous access required transhepatic venous access and bidirectional block was attained with ablation lesions along the cavotricuspid isthmus on both sides of the baffle.

    View details for DOI 10.1016/j.ccep.2015.10.028

    View details for PubMedID 26920194

  • Ventricular Tachycardia in Congenital Pulmonary Stenosis. Cardiac electrophysiology clinics Ruckdeschel, E. S., Schuller, J., Nguyen, D. T. 2016; 8 (1): 205–9


    With modern surgical techniques, there is significantly increased life expectancy for those with congenital heart disease. Although congenital pulmonary valve stenosis is not as complex as tetralogy of Fallot, there are many similarities between the 2 lesions, such that patients with either of these conditions are at risk for ventricular arrhythmias and sudden cardiac death. Those patients who have undergone surgical palliation for congenital pulmonary stenosis are at an increased risk for development of ventricular arrhythmias and may benefit from a more aggressive evaluation for symptoms of palpitations or syncope.

    View details for DOI 10.1016/j.ccep.2015.10.030

    View details for PubMedID 26920196

  • Supraventricular Tachycardia in a Patient with an Interrupted Inferior Vena Cava. Cardiac electrophysiology clinics Gonzalez, J. E., Nguyen, D. T. 2016; 8 (1): 45–50


    The noncoronary cusp and aortomitral continuity should be evaluated for early atrial activation when atrial tachycardias are noted to arise near the His bundle region, especially when the activation is diffuse around the His and when the P-wave morphology predicts a left atrial focus. In patients with congenital anomalies, alternate routes for catheter position need to be explored, including retrograde access for left atrial tachycardias and positioning of intracardiac echocardiography in the azygous vein for visualization of intracardiac structures. Consideration of remote magnetic navigation, if available, is another approach.

    View details for DOI 10.1016/j.ccep.2015.10.002

    View details for PubMedID 26920168

  • A Case of Cough-induced Ventricular Tachycardia in a Patient with a Left Ventricular Assist Device. Cardiac electrophysiology clinics Ruckdeschel, E. S., Wolfel, E., Nguyen, D. T. 2016; 8 (1): 165–67


    In this case, the patient's ventricular tachycardia (VT) was specifically induced by coughing, which has not previously been described. Decreasing the rotational speed of the left ventricular assist device (LVAD) and increasing preload by stopping the patient's nitrates and reducing diuretic dose allowed improved filling of the left ventricle (LV) and increased LV volumes. When coughing recurred, the effects on the LV cavity were less pronounced and thus VT was reduced. Although ventricular arrhythmias are common after LVAD placement, this is a unique case in which VT was caused by coughing, which is ordinarily not considered arrhythmogenic.

    View details for DOI 10.1016/j.ccep.2015.10.019

    View details for PubMedID 26920187

  • An Approach to Endovascular Ventricular Pacing in a Patient with Ebstein Anomaly and a Mechanical Tricuspid Valve. Cardiac electrophysiology clinics Zipse, M. M., Groves, D. W., Khanna, A. D., Nguyen, D. T. 2016; 8 (1): 169–71


    In the presence of a mechanical tricuspid valve, endocardial right ventricular pacing is contraindicated, and permanent pacing is usually achieved via a surgically implanted epicardial lead. In a patient with Ebstein anomaly, a mechanical tricuspid valve, and complete heart block, transvenous pacing was achieved by implantation of a pace-sense lead in a coronary sinus ventricular branch. Noninvasive cardiac imaging can provide information regarding anatomic variation in patients with congenital heart disease or when there are challenges to lead placement. With careful planning and execution, endovascular pacing in patients with a mechanical tricuspid valve is feasible and can safely be performed.

    View details for DOI 10.1016/j.ccep.2015.10.020

    View details for PubMedID 26920188

  • Ablation of Atrial Fibrillation in a Patient with a Mechanical Mitral Valve. Cardiac electrophysiology clinics Zipse, M. M., Nguyen, D. T. 2016; 8 (1): 155–59


    Clinicians must be mindful of the left ventricular lead when cannulating the coronary sinus with a decapolar catheter or an ablation catheter. Left atrial catheter ablation for the treatment of atrial fibrillation in patients with a mechanical mitral valve, when approached carefully, can be performed safely and effectively. Block across linear lines should be confirmed using differential activation and/or differential pacing to decrease risks of proarrhythmias.

    View details for DOI 10.1016/j.ccep.2015.10.017

    View details for PubMedID 26920185

  • Antidromic Atrioventricular Reciprocating Tachycardia Using a Concealed Retrograde Conducting Left Lateral Accessory Pathway. Cardiac electrophysiology clinics Gonzalez, J. E., Zipse, M. M., Nguyen, D. T., Sauer, W. H. 2016; 8 (1): 37–43


    Atrioventricular reciprocating tachycardia is a common cause of undifferentiated supraventricular tachycardia. In patients with manifest or concealed accessory pathways, it is imperative to assess for the presence of other accessory pathways. Multiple accessory pathways are present in 4% to 10% of patients and are more common in patients with structural heart disease. In rare cases, multiple accessory pathways can act as the anterograde and retrograde limbs of the tachycardia.

    View details for DOI 10.1016/j.ccep.2015.10.001

    View details for PubMedID 26920167

  • Impact of Alcohol Consumption on Atrial Fibrillation Outcomes Following Pulmonary Vein Isolation. Journal of atrial fibrillation Barham, W. Y., Sauer, W. H., Fleeman, B. n., Brunnquell, M. n., Tzou, W. n., Aleong, R. n., Schuller, J. n., Zipse, M. n., Tompkins, C. n., Nguyen, D. T. 2016; 9 (4): 1505


    Moderate to heavy alcohol use has been shown to be associated with increased atrial fibrillation (AF) incidence. However, the relationship between alcohol use and AF recurrence after pulmonary vein isolation (PVI) is not well known.We sought to study the impact of different alcohol consumption levels on outcomes after AF ablation.A retrospective analysis was performed of 226 consecutive patients undergoing first time PVI for AF. Clinical data were collected including alcohol intake classified into 3 groups: none-rare (< 1 drink/ week), moderate (1-7 drinks/ week), and heavy (> 7 drinks/ week). Patients were followed for recurrences within the first 3 months (blanking period; early recurrence) and after 3 months up to 1 year (late recurrence) after the ablation.Paroxysmal and persistent AF had early recurrence rates of 29.1% and 32.2%, and late recurrence rates of 30.2% and 44.1%, respectively. The none-rare alcohol group had a higher frequency of diabetes mellitus (p=0.007). Neither moderate or heavy alcohol consumption, in reference to the none-rare group, was significantly predictive of early or late AF recurrence on adjusted multivariate logistic regression analysis (p>0.05).Despite known associations between alcohol and incidence of AF, alcohol consumption is not associated with early or late AF recurrence after PVI in this cohort.

    View details for DOI 10.4022/jafib.1505

    View details for PubMedID 29250261

    View details for PubMedCentralID PMC5673320

  • Clinical and biophysical evaluation of variable bipolar configurations during radiofrequency ablation for treatment of ventricular arrhythmias. Heart rhythm Nguyen, D. T., Tzou, W. S., Brunnquell, M. n., Zipse, M. n., Schuller, J. L., Zheng, L. n., Aleong, R. A., Sauer, W. H. 2016; 13 (11): 2161–71


    Bipolar radiofrequency ablation (bRFA) has been used to create larger ablation lesions and to treat refractory arrhythmias. However, little is known about optimal bRFA settings.The purpose of this study was to evaluate various bRFA settings, including active and ground catheter tip orientation and use of variable active and ground catheters during bRFA.Two ablation catheters, 1 active and 1 ground, were oriented across from each other, with viable bovine myocardium in between. The catheter tips were placed in various combinations perpendicular or parallel to the myocardium. The active catheter was either a 3.5-mm externally irrigated or 8-mm tip, and the ground catheter was either a 4-mm, 3.5-mm irrigated, or 8-mm tip. Retrospective analysis was undertaken for all bRFA performed at University of Colorado.The largest and deepest lesions were produced using irrigated active and ground tips, oriented perpendicularly. In 14 cases (10 patients) of bRFA for ventricular tachycardia and premature ventricular complexes, acute success was achieved in 13 of 14 procedures. Long-term success was achieved in 7 of 10 patients, but 3 patients required multiple bRFA ablations.Active and ground catheter tip orientation and type are important determinants of lesion sizes during bRFA. The largest and deepest lesions, without a higher incidence of steam pops, were achieved using 2 irrigated catheters. As the largest published series to date, bRFA ablation can be performed safely and effectively in humans. Larger studies are necessary to better evaluate bRFA efficacy and safety.

    View details for DOI 10.1016/j.hrthm.2016.07.011

    View details for PubMedID 27424078

  • Protection of Critical Structures During Radiofrequency Ablation of Adjacent Myocardial Tissue Using Catheter Tips Partially Insulated With Thermally Conductive Material. JACC. Clinical electrophysiology Nguyen, D. T., Tzou, W. S., Zipse, M. M., Moss, J. D., Zheng, L. n., Sauer, W. H. 2016; 2 (7): 838–46


    This study sought to determine whether partially insulated focused ablation (PIFA) catheters can minimize risk of injury to critical structures, such as the phrenic nerve and atrioventricular (AV) node, during ablation of adjacent myocardial tissue.PIFA catheters using thermally conductive materials may have differential radiofrequency (RF) heating properties allowing for tailored RF application with more precision.Open-irrigated, 4- and 8-mm RF ablation catheter tips were insulated partially by coating one-half of their surfaces with a layer of vinyl, silicone, vinyl-silicone, polyurethane, or a composite of aluminum oxide/boron nitride (AOBN). These coated catheters or corresponding noninsulated catheters were positioned with 10 g of force on viable bovine myocardial tissue during RF application in an ex vivo setup. Tip temperatures, power, and lesion volumes were compared. The most effective coating, AOBN, was modified further by adding fenestrations to aid in passive cooling. PIFA catheters with fenestrated AOBN coating were then tested in an in vivo porcine model to target myocardial tissue adjacent to the AV node and the phrenic nerve.PIFA catheters all demonstrated higher tip temperatures, although silicone- and AOBN-catheters demonstrated this to a lesser degree. Significant differences in lesion volumes and temperature-limited powers were noted between control, silicone, and AOBN tips. Steam pops were significantly higher for silicone but not AOBN. In contrast with non-PIFA catheters, injuries to the phrenic nerve and AV node during in vivo ablations with AOBN insulation positioned over these structures were reduced significantly.RF ablation using catheter tips partially coated with a thermally conductive insulation material such as AOBN results in larger ablation lesion volumes without temperature limitations. Partial insulation of the catheter tip will protect adjacent critical structures during RF ablation.

    View details for DOI 10.1016/j.jacep.2016.03.010

    View details for PubMedID 29759769

  • Ventricular Tachycardia in a Patient with Biventricular Noncompaction. Cardiac electrophysiology clinics Gonzalez, J. E., Tzou, W. n., Sauer, W. H., Nguyen, D. T. 2016; 8 (1): 139–44


    Patients with ventricular noncompaction are susceptible to developing ventricular tachycardia. Commonly, the origin of ventricular tachycardia is endocardial; however, epicardial origins and scar cannot be excluded and should be considered when poor endocardial mapping is present. Other cardiomyopathies, such as arrhythmogenic right ventricular cardiomyopathy, can coexist with ventricular noncompaction and should be excluded in these patients.

    View details for DOI 10.1016/j.ccep.2015.10.014

    View details for PubMedID 26920182

  • Atrial Fibrillation Ablation Without Pulmonary Vein Isolation in a Patient with Fontan Palliation. Cardiac electrophysiology clinics Ruckdeschel, E. S., Kay, J. n., Sauer, W. H., Nguyen, D. T. 2016; 8 (1): 161–64


    In a patient with Fontan palliation and persistent atrial fibrillation two triggers were identified that initiated atrial fibrillation (AF) from the superior vena cava (SVC) and the right atrium. SVC triggers are more common in patients with a normal-sized left atrium. Eliminating these triggers prevented AF from being sustained in this patient and thus pulmonary vein isolation was not pursued. The patient has remained AF free for 3 years without medications or repeat ablation. Targeting of potential right-sided triggers for AF ablation, before pulmonary vein isolation, should be considered; such an approach may reduce risks in these complex patients.

    View details for DOI 10.1016/j.ccep.2015.10.018

    View details for PubMedID 26920186

  • Enhanced Radiofrequency Ablation With Magnetically Directed Metallic Nanoparticles. Circulation. Arrhythmia and electrophysiology Nguyen, D. T., Tzou, W. S., Zheng, L. n., Barham, W. n., Schuller, J. L., Shillinglaw, B. n., Quaife, R. A., Sauer, W. H. 2016; 9 (5)


    Remote heating of metal located near a radiofrequency ablation source has been previously demonstrated. Therefore, ablation of cardiac tissue treated with metallic nanoparticles may improve local radiofrequency heating and lead to larger ablation lesions. We sought to evaluate the effect of magnetic nanoparticles on tissue sensitivity to radiofrequency energy.Ablation was performed using an ablation catheter positioned with 10 g of force over prepared ex vivo specimens. Tissue temperatures were measured and lesion volumes were acquired. An in vivo porcine thigh model was used to study systemically delivered magnetically guided iron oxide (FeO) nanoparticles during radiofrequency application. Magnetic resonance imaging and histological staining of ablated tissue were subsequently performed as a part of ablation lesion analysis. Ablation of ex vivo myocardial tissue treated with metallic nanoparticles resulted in significantly larger lesions with greater impedance changes and evidence of increased thermal conductivity within the tissue. Magnet-guided localization of FeO nanoparticles within porcine thigh preps was demonstrated by magnetic resonance imaging and iron staining. Irrigated ablation in the regions with greater FeO, after FeO infusion and magnetic guidance, created larger lesions without a greater incidence of steam pops.Metal nanoparticle infiltration resulted in significantly larger ablation lesions with altered electric and thermal conductivity. In vivo magnetic guidance of FeO nanoparticles allowed for facilitated radiofrequency ablation without direct infiltration into the targeted tissue. Further research is needed to assess the clinical applicability of this ablation strategy using metallic nanoparticles for the treatment of cardiac arrhythmias.

    View details for DOI 10.1161/CIRCEP.115.003820

    View details for PubMedID 27162034

  • Lower Left Atrial Strain Rates Are Observed in Patients Who Develop Atrial Fibrillation After Successful Atrial Flutter Ablation Gonzalez, J. E., Sauer, W. H., Nguyen, D. T. WILEY-BLACKWELL. 2015: 588–89
  • Measured Lead Parameters and Electrogram Sensing Over Time in PatientsWith Cardiac Sarcoidosis andanImplanted Cardiac-Defibrillator. JACC. Clinical electrophysiology Zipse, M. M., Schuller, J. L., Steckman, D. S., Katz, D. F., Tzou, W. S., Nguyen, D. T., Aleong, R. G., Sung, R. K., Tompkins, C., Varosy, P. D., Sauer, W. H. 2015; 1 (1-2): 94–102


    OBJECTIVES: The study sought to characterize the performance of implanted leads among a cohort of patients with cardiac sarcoidosis (CS) and implantable cardiac-defibrillators (ICDs).BACKGROUND: An ICD is indicated for some patients with CS for the prevention of sudden cardiac death. CS can lead to myocardial inflammation and scar that may interfere with lead performance.METHODS: We performed a case-control study within the cohort of patients at the University of Colorado Hospital withCS and an ICD (n= 48) compared with randomly selected controls (n= 117) who had other indications for an ICD. We compared the measured lead parameters at the time of routine interrogation to assess the differences between groups over time. The mean duration of follow-up was 51 months. Survival analysis was performed by the method of Kaplan and Meier and by Cox proportional hazards regression.RESULTS: There was no significant difference in measured lead impedance, capture thresholds, or sensed electrograms at implantation between the CS and control groups. There were no significant differences between the mean parameters between groups over the follow-up period. However, patients with CS have a high incidence of significant (>50%) drop in measured electrograms (16 of 46 [33%] CS patients vs. 4 of 117 [3.4%] controls; hazard ratio: 10.49, 95% confidence interval: 3.47 to 31.67). As a result of alterations in lead parameters, 2 patients (4.3%) required lead revision, and 6 patients (13%) required ICD testing to ensure adequate detection of induced ventricular fibrillation.CONCLUSIONS: Reductions over time in ICD sensing of P- and/or R-wave electrograms are common in patients with CS.Although further investigation is needed to determine the mechanism of these changes, these findings suggest that patients with CS who have an ICD should be closely monitored for clinically relevant changes in P- and R-wave amplitudes.

    View details for DOI 10.1016/j.jacep.2015.02.013

    View details for PubMedID 29759346

  • Effect of radiofrequency energy delivery in proximity to metallic medical device components. Heart rhythm Nguyen, D. T., Barham, W. n., Zheng, L. n., Dinegar, S. n., Tzou, W. S., Sauer, W. H. 2015; 12 (10): 2162–69


    Radiofrequency (RF) ablation of cardiac arrhythmias is often performed in the presence of metallic materials in the heart.We hypothesize that metal objects in proximity to an RF ablation source can lead to ohmic heating of surrounding tissue. Furthermore, we hypothesize that insulation of the metal can mitigate this RF effect.A model consisting of viable bovine myocardium or thermochromic liquid crystal medium, a circulating saline bath at 37°C, and a load cell was used. A 4-mm RF ablation catheter was positioned with 10 g of force over bovine myocardium and placed in proximity to a copper wire, a defibrillator lead, and a circular mapping catheter. RF was applied at 30 W, and tissue temperatures were measured. Ablation near insulated and noninsulated esophageal temperature probes was also performed.Ablation in proximity to metal resulted in higher temperatures. Average maximum distances for observed thermal changes to >45°C for the ± lead were 5.2 ± 0.3 mm and 5.7 ± 0.4 mm when metal was interposed between the catheter and the ground electrode. Presence of an esophageal temperature probe increased temperatures in tissues adjacent to the probe and caused lesions remote to the ablation site. Esophageal probe insulation prevented these tissue temperature increases and injury to nontargeted tissues.Effects of RF ablation are potentiated near metallic components of medical devices, leading to significant tissue heating. Further research is needed to assess the safety impact of RF in the myocardium near metallic objects, particularly esophageal temperature probes.

    View details for DOI 10.1016/j.hrthm.2015.05.011

    View details for PubMedID 26048195

  • Effects of radiofrequency energy delivered through partially insulated metallic catheter tips on myocardial tissue heating and ablation lesion characteristics. Heart rhythm Nguyen, D. T., Moss, J. D., Zheng, L. n., Huang, J. n., Barham, W. n., Sauer, W. H. 2015; 12 (3): 623–30


    Cardiac radiofrequency (RF) ablation is typically achieved using symmetric catheter tips, which may result in unintended heating adjacent to targeted tissue. Partial insulation may alter lesion geometry and prevent collateral heating.The purpose of this study was to assess partially insulated focused ablation (PIFA).Partial insulation using thermally conductive materials was applied to a 4-mm or 8-mm nonirrigated catheter and a 3.5-mm open-irrigated catheter. These PIFA tips, or their noninsulated counterparts, were applied to ex vivo viable bovine myocardium. Ablations were delivered at various powers and under temperature control. Potential clinical applicability was evaluated in vivo by targeting porcine epicardium with irrigated PIFA and assessing its protective effects on the pericardium.PIFA catheters exhibited different properties and produced asymmetric lesions compared with corresponding standard ablation catheters. Temperatures at 3- and 5-mm depths were higher for PIFA catheters, with a temperature increase measured at the catheter tip-tissue interface; however, in temperature control ablation, tip-tissue temperature increases did not limit power delivery. Furthermore, temperatures were lower on the insulated surface and were significantly higher on the noninsulated PIFA side. Impedance changes were significantly larger; more steam pops were observed with PIFA but were mitigated by external irrigation, a larger tip electrode, and use of more thermally conductive insulation. In contrast to standard ablation, open-irrigated PIFA created larger asymmetric lesions in vivo over porcine epicardium, without evidence of pericardial injury.PIFA ablation has different characteristics compared with symmetrically conductive ablation. Further research is needed to assess the clinical implications of insulated catheter ablation.

    View details for DOI 10.1016/j.hrthm.2014.11.022

    View details for PubMedID 25460861

  • Effect of Irrigant Characteristics on Lesion Formation After Radiofrequency Energy Delivery Using Ablation Catheters with Actively Cooled Tips. Journal of cardiovascular electrophysiology Nguyen, D. T., Olson, M. n., Zheng, L. n., Barham, W. n., Moss, J. D., Sauer, W. H. 2015; 26 (7): 792–98


    The delivery of radiofrequency (RF) energy through irrigated ablation catheters may be affected by irrigant osmolarity and by catheter position. We sought to characterize lesion formation characteristics using different irrigants in both open and closed irrigated catheter.An ex vivo model consisting of viable bovine myocardium and a submersible load cell was assembled in a circulating saline bath at 37°C. An externally irrigated ablation catheter and a closed irrigated catheter were positioned with 10 g of force in both perpendicular and parallel positions. A series of ablation lesions using different irrigants were delivered using a constant rate of irrigation (30 cc/min) at 50 W. Potential clinical applicability was evaluated in vivo by targeting porcine epicardium with different irrigants during open irrigation ablation and assessing lesion sizes.Ablation in the perpendicular position produced significantly larger lesions for all irrigants, compared to their respective parallel position ablation. For both open and closed irrigated ablation, half normal saline (HNS) ablation created larger lesions than normal saline (NS), and dextrose water (D5W) lesions were significantly larger than both HNS and NS lesions. Steam pops were mostly observed in the perpendicular position, and the rate of steam pops was statistically higher only for open irrigated D5W, but not for HNS, when compared to NS. Both open and closed irrigated ablation with D5W and HNS in the parallel position created larger lesions than parallel NS ablation without causing more steam pops. In an in vivo porcine model, open irrigated ablation with D5W created larger lesions compared to standard NS irrigation.In ex vivo and in vivo models, decreased osmolarity and charge density increased RF energy delivery to tissue, resulting in larger lesions for both open and closed irrigated ablations. A perpendicular catheter position created larger lesions across all irrigants for both open and closed irrigation ablation. The incidence of steam pops was observed more frequently with high power open irrigated using D5W, especially if the catheter was in a perpendicular position. Further research is required to evaluate any clinical role for using different irrigants with an externally irrigated catheter.

    View details for DOI 10.1111/jce.12682

    View details for PubMedID 25864402

  • Gadolinium Augmentation of Myocardial Tissue Heating During Radiofrequency Ablation. JACC. Clinical electrophysiology Nguyen, D. T., Barham, W. n., Moss, J. n., Zheng, L. n., Shillinglaw, B. n., Quaife, R. n., Tzou, W. S., Sauer, W. H. 2015; 1 (3): 177–84


    This study hypothesized that a metal already commonly used in medical procedures, gadolinium (Gd), will augment radiofrequency (RF) thermal injury and affect cardiac ablation lesions.Enhancement of RF ablation using metallic particles has been proposed for ablation of tumors.A series of ablation lesions were delivered at variable power using an ex vivo model. Tissue temperatures and lesion characteristics were analyzed. Ablation in a porcine in vivo model after direct needle injection of the myocardium with Gd or after systemic administration of Gd encased in heat sensitive liposomes was also performed and compared to control values.Ablation after Gd infiltration of myocardial tissue resulted in significantly larger lesions at both low- and high-power settings. Larger impedance changes were observed during ablation of Gd-treated myocardium. In vivo ablation using a force-sensing irrigated tip catheter resulted in enhanced lesion sizes after Gd injection without a higher incidence of steam pops or perforation. Systemic administration of liposomal Gd with local release by RF heating did not result in larger ablation sizes.Gd can be used to enhance RF ablation lesions. In both ex vivo studies with a 4-mm ablation catheter under power control and in vivo findings with an irrigated tip catheter, ablation of myocardium infiltrated with Gd resulted in larger lesions, with altered RF electrical and thermal characteristics. More research is needed to refine the potential for Gd facilitation of RF ablation. The use of systemic heat-sensitive liposomes containing Gd with targeted release by RF heating did not affect lesion size.

    View details for DOI 10.1016/j.jacep.2015.03.012

    View details for PubMedID 29759362

  • Carbon Nanotube Facilitation of Myocardial Ablation with Radiofrequency Energy JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY Nguyen, D. T., Barham, W., Zheng, L., Shillinglaw, B., Tzou, W. S., Neltner, B., Mestroni, L., Bosi, S., Ballerini, L., Prato, M., Sauer, W. H. 2014; 25 (12): 1385–90


    The use of carbon nanotubes (CNTs) in oncology has been proposed for the purpose of sensitizing tumors to radiofrequency (RF) ablation. We hypothesize that myocardial tissue infiltrated with CNTs will improve thermal conductivity of RF heating and lead to altered ablation lesion characteristics.An ex vivo model consisting of viable bovine myocardium, a circulating saline bath at 37 °C, a submersible load cell, and a deflectable sheath was assembled. A 4-mm nonirrigated ablation catheter was positioned with 10 gm of force over bovine myocardium infiltrated with CNTs, 0.9% saline, or sham injections. A series of ablation lesions were delivered at 20 and 50 W, and lesion volumes were acquired by analyzing tissue sections with a digital micrometer. Tissue temperature analyses at 3 and 5 mm depths were also performed.Myocardial tissue treated with CNTs resulted in significantly larger lesions at both low and high power settings. The electrical impedance was increased in CNT treated tissue with a greater impedance change observed in the CNT infiltrated myocardium. The thermal conductivity of heat generated by application of RF in the tissue was altered by the presence of CNTs, resulting in higher temperatures at 3 and 5 mm depths for both 20 and 50 W.Myocardial tissue treated with CNTs resulted in significantly larger lesions at both low and high power settings. The electrical and thermal conductivity of heat generated by application of RF in myocardial tissue was altered by the presence of CNTs. Further research is needed to assess the in vivo applicability for this concept of facilitated ablation with CNTs.

    View details for DOI 10.1111/jce.12509

    View details for Web of Science ID 000346020800018

    View details for PubMedID 25091811

  • Diagnostic Value of Adenosine Conversion of Wide Complex Tachycardia Reply JAMA INTERNAL MEDICINE Schuller, J. L., Varosy, P. D., Duy Thai Nguyen 2014; 174 (10): 1706
  • Inappropriate Shocks due to Subcutaneous Air in a Patient With a Subcutaneous Cardiac Defibrillator CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY Zipse, M. M., Sauer, W. H., Varosy, P. D., Aleong, R. G., Nguyen, D. T. 2014; 7 (4): 768–70

    View details for DOI 10.1161/CIRCEP.114.001614

    View details for Web of Science ID 000341201300036

    View details for PubMedID 25140025

  • In-Hospital Complications Associated With Reoperations of Implantable Cardioverter Defibrillators AMERICAN JOURNAL OF CARDIOLOGY Stedman, D. A., Varosy, P. D., Parzynski, C. S., Masoudi, F. A., Curtis, J. P., Sauer, W. H., Nguyen, D. T. 2014; 114 (3): 419–26


    Repeat implantable cardioverter defibrillator (ICD) procedures are increasing and may be associated with higher risks for complications. To provide more information for clinical decision making, especially in light of recent defibrillator advisories, we examined a large national cohort to characterize repeat ICD procedural outcomes. Using data from the National Cardiovascular Data Registry (ICD Registry), we compared patient characteristics, reasons for ICD implantation, and associated in-hospital adverse events among 92,751 patients receiving their first device and 81,748 patients who underwent repeat procedures with (n = 31,057) and without (n = 50,691) lead involvement. Hierarchical multivariable logistic regression was used to determine the predictors of in-hospital complications. Complication rates were higher in those who underwent repeat ICD procedures with lead involvement (lead implantation or revision), compared with patients who underwent initial implants (3.2% vs 2.6%, p <0.001) or versus those with pocket-only (e.g., generator change only) procedures (3.2% vs 0.6%, p <0.001). There were significantly more in-hospital deaths, lead dislodgements, and infections requiring antibiotics in the lead involvement cohort. Compared with those who had a pocket-only procedure, the multivariable adjusted odds ratio of any complication were increased at 4.20 (95% confidence interval: 3.66 to 4.82, p <0.001) in patients who underwent repeat procedures with lead involvement excluding lead extraction or 7.11 (95% confidence interval: 5.96 to 8.48, p <0.001) in procedures involving lead extractions. In conclusion, repeat ICD procedures, when involving the addition or revision of a lead with or without concurrent lead extraction, are associated with higher complication rates compared with initial implants and with those who underwent pocket-only procedures.

    View details for DOI 10.1016/j.amjcard.2014.05.010

    View details for Web of Science ID 000339641700015

    View details for PubMedID 24927972

  • Change in QRS Duration Over Time Predicts Ventricular Tachycardia after Cardiac Resynchronization Therapy Steckman, D. A., Frasier, R., Zipse, M., Gonzalez, J., Katz, D., Aleong, R., Schuller, J., Tzou, W., Tompkins, C., Nguyen, D. T., Varosy, P., Sauer, W., Sung, R. CHURCHILL LIVINGSTONE INC MEDICAL PUBLISHERS. 2014: S36
  • Atrial flutter ablation in a patient with Marfanoid syndrome and anomalous cavotricuspid isthmus EUROPACE Heath, R., Kay, J., Duy Thai Nguyen 2014; 16 (7): 1006

    View details for DOI 10.1093/europace/eut431

    View details for Web of Science ID 000339667400010

    View details for PubMedID 24473500

  • Catheter ablation of atrial fibrillation and left atrial flutter in a patient with a left atrial appendage occlusion device EUROPACE Steckman, D. A., Duy Thai Nguyen, Sauer, W. H. 2014; 16 (5): 651

    View details for DOI 10.1093/europace/euu039

    View details for Web of Science ID 000336080400010

    View details for PubMedID 24591678

  • Preprocedural Imaging in Patients with Transposition of the Great Arteries Facilitates Placement of Cardiac Resynchronization Therapy Leads PACE-PACING AND CLINICAL ELECTROPHYSIOLOGY Ruckdeschel, E., Quaife, R., Lewkowiez, L., Kay, J., Sauer, W. H., Collins, K. K., Duy Thai Nguyen 2014; 37 (5): 546–53


    The purpose of this study is to review a series of patients with complex congenital heart disease in whom preprocedural imaging was used to assist placement of cardiac resynchronization therapy (CRT) leads.CRT may be beneficial in patients with a failing systemic ventricle and transposition of the great arteries (TGA). However, complex coronary venous anatomy can be challenging for placement of CRT leads.Between October 2006 and June 2012, seven patients with either dextro-TGA (d-TGA) or levo-TGA (l-TGA) underwent preprocedural imaging prior to placement of CRT leads (three, d-TGA and four, l-TGA). Three patients underwent cardiac computed tomography (CT) and four underwent coronary angiography, which included levophase imaging of the coronary sinus (CS) or direct contrast injection of the CS. Where CS anatomy was appropriate with drainage into the systemic venous circulation, a transvenous approach was planned. In all other cases, the patient was referred for surgical placement of epicardial leads.Seven patients were identified with either d-TGA or l-TGA who had undergone preprocedural imaging prior to placement of CRT leads (three, d-TGA and four, l-TGA). Three patients underwent cardiac CT and four underwent coronary angiography, which included levophase imaging of the CS or direct contrast injection of the CS. All seven patients had successful CRT lead placement guided by preprocedure imaging. Three patients required surgical placement whereas four were able to undergo transvenous placement. There were no complications. The majority of patients (four of seven) had improvement in New York Heart Association class as well as subjective improvement in exercise tolerance and energy. The majority of patients also had subjective improvement in systemic right ventricular function by echocardiogram and objective improvement in fractional area change of the right ventricle. The follow-up period ranged from 13 months to 55 months with a mean follow-up of 39 months.Placement of biventricular leads for CRT in patients with l-TGA or d-TGA is feasible. Preprocedural imaging of the CS allows for better assessment of its anatomy and helps determine procedural approach for CRT placement, thereby limiting unnecessary procedures. In the majority of patients, there was subjective improvement in functional status and right ventricular function; in addition, there was objective improvement in echocardiographic parameters of right ventricular function after CRT placement.

    View details for DOI 10.1111/pace.12308

    View details for Web of Science ID 000334863000003

    View details for PubMedID 24313876

  • Inhibition of Proto-Oncogene c-Src Tyrosine Kinase JOURNAL OF THE AMERICAN COLLEGE OF CARDIOLOGY Mestroni, L., Duy Thai Nguyen 2014; 63 (9): 935–37

    View details for DOI 10.1016/j.jacc.2013.10.082

    View details for Web of Science ID 000332399700013

    View details for PubMedID 24412447

    View details for PubMedCentralID PMC4469261

  • Vectorcardiographic predictors of ventricular arrhythmia inducibility in patients with tetralogy of Fallot. Journal of electrocardiology Cortez, D. n., Ruckdeschel, E. n., McCanta, A. C., Collins, K. n., Sauer, W. n., Kay, J. n., Nguyen, D. n. 2014; 48 (2): 141–44


    Vectorcardiography (VCG) may have predictive value in Tetralogy of Fallot (TOF) patients undergoing ventricular arrhythmia inducibility (VAI) electrophysiology studies (EPs).Blinded, retrospective analyses of 37 adult TOF patients undergoing EPs prior to pulmonary valve replacements were performed (21 female, median age 37years). VAI was evaluated from EPs and resting 12-lead electrocardiograms, respectively using QRS and heart rate adjusted Q-T intervals, spatial QRS-T angles (peaks), T-wave and QRS-wave (QRSwave vc) component vector root mean squares. Differences were assessed (Student t-tests, Mann Whitney U-tests, Analysis of Variance). Relative risks were calculated.16 patients had VAI (6 monomorphic, 10 polymorphic). Only the QRSwave vc showed significant differences between those with and without VAI, 10.5±2.4 dmV vs. 13.9±4.5dmV, respectively (p=0.002), area under the ROC curve of 0.78 and relative risk of 2.52.VCG evidence of depolarization differences was significant between TOF patients with and without inducible VA.

    View details for DOI 10.1016/j.jelectrocard.2014.11.009

    View details for PubMedID 25483288

  • Predictors of Adverse Events in 24,890 Patients Undergoing Lead Extraction Kao, D., Varosy, P., Nguyen, D. T., Tzou, W., Katz, D., Schuller, J., Sung, R., Steckman, D., Sauer, W. H., Aleong, R. LIPPINCOTT WILLIAMS & WILKINS. 2013
  • Temporal Trends in Mortality and Adverse Events in 24,890 Patients Undergoing Lead Extraction Over a Decade Kao, D., Varosy, P., Nguyen, D. T., Tzou, W., Katz, D., Schuller, J., Sung, R., Steckman, D., Sauer, W. H., Aleong, R. LIPPINCOTT WILLIAMS & WILKINS. 2013
  • Effect of catheter movement and contact during application of radiofrequency energy on ablation lesion characteristics JOURNAL OF INTERVENTIONAL CARDIAC ELECTROPHYSIOLOGY Olson, M. D., Phreaner, N., Schuller, J. L., Nguyen, D. T., Katz, D. F., Aleong, R. G., Tzou, W. S., Sung, R., Varosy, P. D., Sauer, W. H. 2013; 38 (2): 123–29


    The efficient delivery of radiofrequency (RF) energy through an endocardial ablation catheter is affected by variable tissue contact due to cardiac motion with myocardial contraction and respiration. In addition, many operators intentionally move an ablation catheter during the delivery of radiofrequency energy when targeting specific arrhythmias that require lines of conduction block such as atrial flutter and atrial fibrillation. We sought to characterize and quantify any effects of catheter movement and intermittent ablation catheter contact on lesion characteristics.An ex vivo model consisting of recently excised viable bovine myocardium, a circulating saline bath at 37 °C, a submersible load cell, and a deflectable sheath with an ablation catheter was assembled. A stepper motor attached to an ablation catheter apparatus was programmed to simulate linear drag lesions and series of point lesions with variable contact using constant force. Lesion volumes were analyzed using a digital micrometer by measuring depth, max width, depth at max width, and surface width and compared.The drag lesion was significantly larger than a pointby-point linear lesion using a constant force of 15 g (2,088± 122 mm3 vs. 1,595±121.6; p =0.01) when controlling for RF time and power. For single point lesion assessment, constant contact lesions were significantly larger than lesions created with intermittent contact using the same duration of RF (194± 68 mm3 vs. 112.5±53; p =0.03). There was no significant difference in lesion size between the constant contact at 60 s and 90-s intermittent contact lesions (194±68 mm3 vs.186±69).In our ex vivo model, externally irrigated radiofrequency catheters produced drag lesion volumes equal to or larger than those created by a point-by-point method.We also found decreased lesion size due to intermittent contact can be overcome by increasing duration of ablation time.

    View details for DOI 10.1007/s10840-013-9824-4

    View details for Web of Science ID 000325710100007

    View details for PubMedID 24022756

  • Durable Pulmonary Vein Isolation: The Holy Grail of Atrial Fibrillation Ablation. Journal of atrial fibrillation Nguyen, D. T., Sauer, W. H. 2013; 6 (3): 927


    The inability to achieve durable pulmonary vein isolation remains a major limitation to catheter ablation for the treatment of atrial fibrillation (AF). In this review, we discuss the research performed over the past decade investigating methods to improve lesion permanence for the goal of durable pulmonary vein isolation (PVI). Investigations evaluating procedural techniques, adjunctive pharmacologic therapy, and newer energy sources designed to improve ablation lesion permanence are discussed.

    View details for DOI 10.4022/jafib.927

    View details for PubMedID 28496898

  • Wide Complex Tachycardia and Adenosine JAMA INTERNAL MEDICINE Schuller, J. L., Varosy, P. D., Duy Thai Nguyen 2013; 173 (17): 1644–46
  • Emergent Catheter Ablation of VT/VF Storm Can Be Safely Performed in Patients with Severe Heart Failure Peters, L. A., Gonzalez, J. E., Aleong, R. G., Katz, D., Nguyen, D. T., Schuller, J. L., Sung, R. K., Varosy, P. D., Brieke, A., Sauer, W. H., Tzou, W. S. CHURCHILL LIVINGSTONE INC MEDICAL PUBLISHERS. 2013: S23
  • Endocardial Electrogram Characteristics of Epicardial Ventricular Arrhythmias JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY Tzou, W. S., Nguyen, D. T., Aleong, R. G., Varosy, P. D., Katz, D. F., Heath, R. R., Schuller, J. L., Lowery, C. M., Lewkowiez, L., Sauer, W. H. 2013; 24 (6): 649–54


    While most ventricular arrhythmias (VA) can be ablated successfully using an endocardial (endo) approach, epicardial (epi) mapping and ablation is sometimes required. There may be suggestive clues on the surface electrocardiogram; however, identification of an epi origin of VA with certainty remains problematic.All patients referred for ablation of ventricular tachycardia or frequent ventricular ectopy from June 2007 to July 2011 were evaluated. Patients with completed endo and epi electroanatomical activation maps of an epi VA were included (n = 10). Bipolar electrograms (EGMs) in the area of earliest endo activation were analyzed and compared to the area of early epi activation. An EGM component was characterized as far field if it was monophasic and there was inability to capture. We identified 3 characteristics from endo mapping that consistently indicated need for epi ablation: (1) Diffusely early activation (>2 cm(2) region of sites with equally earliest activation within 10 milliseconds). (2) Sequence of a far-field EGM followed by a near-field EGM in the region of earliest endo activation. (3) Inability to capture the far-field component of the earliest EGM (stim-QRS < egm-QRS time) or reproduce morphological features of the VA complex with stimulation at the earliest endo site of activation.The presence of a diffusely early area of activation and inability to capture a far-field endo EGM indicates that epi ablation may be needed to eliminate a VA.

    View details for DOI 10.1111/jce.12096

    View details for Web of Science ID 000319898500007

    View details for PubMedID 23397974

  • Percutaneous transhepatic access for catheter ablation of cardiac arrhythmias EUROPACE Duy Thai Nguyen, Gupta, R., Kay, J., Fagan, T., Lowery, C., Collins, K. K., Sauer, W. H. 2013; 15 (4): 494–500


    Femoral venous access may be limited in certain patients undergoing electrophysiology (EP) study and ablation. The purpose of this study is to review a series of patients undergoing percutaneous transhepatic access to allow for ablation of cardiac arrhythmias.Six patients with a variety of cardiac arrhythmias and venous abnormalities underwent percutaneous transhepatic access. Under fluoroscopic and ultrasound guidance, a percutaneous needle was advanced into a hepatic vein and exchanged for a vascular sheath over a wire. Electrophysiology study and radiofrequency ablation was then performed. All tachycardias, including atrial tachycardia, atrial flutter, atrioventricular nodal tachycardia, and atrial fibrillation, were ablated. Procedural times ranged from 227 to 418 min. Fluoroscopy times ranged from 32 to 95 min. There were no complications. All six patients have been arrhythmia-free in follow-up (5-49 months, mean 23.1 months).Percutaneous transhepatic access is safe and feasible in patients with limited venous access who are undergoing EP study and ablation for a range of cardiac arrhythmias.

    View details for DOI 10.1093/europace/eus315

    View details for Web of Science ID 000316964300010

    View details for PubMedID 23385049

  • A Dire Reaction: Rash after Amiodarone Administration AMERICAN JOURNAL OF MEDICINE Chen, A., Sauer, W., Duy Thai Nguyen 2013; 126 (4): 301–3

    View details for DOI 10.1016/j.amjmed.2012.12.002

    View details for Web of Science ID 000316806300021

    View details for PubMedID 23507205

  • Use of Stored Implanted Cardiac Defibrillator Electrograms in Catheter Ablation of Ventricular Fibrillation PACE-PACING AND CLINICAL ELECTROPHYSIOLOGY Lowery, C. M., Tzou, W. S., Aleong, R. G., Nguyen, D. T., Varosy, P. D., Katz, D. F., Heath, R. R., Schuller, J. L., Lewkowiez, L., Sauer, W. H. 2013; 36 (1): 76–85


    Ventricular fibrillation (VF) can be abolished by targeting triggering ventricular ectopy, most often originating in the Purkinje network or right ventricular outflow tract (RVOT). This strategy relies upon the induction of premature ventricular complex (PVC) and/or VF. We sought to evaluate a VF ablation strategy that utilizes analysis of stored implantable cardioverter defibrillator (ICD) electrograms.Eleven consecutive patients experiencing frequent VF episodes (≥three episodes in prior month) underwent electrophysiology study and ablation of VF triggers. PVC and VF induction was intentionally avoided or not possible in all of these patients. Pacemapping at likely sites for PVC triggers of VF using an analysis of the morphology and relative timing of the stored far- and near-field ICD electrograms of VF triggers was used to identify potential culprit locations. Radiofrequency energy was applied to these sites for ablation of the identified VF trigger.Areas targeted for ablation included the left posterior fascicle (six), left anterior fascicle (three), RVOT (three) and left ventricular outflow tract (one); two patients had two separate triggers. Ablation was completed successfully without any complications. With a mean follow-up of 288 days (range 45-649), 10 patients are free of VF.Ablation of VF triggers can be performed successfully with good short-term outcomes in patients with and without underlying heart disease. Use of stored ICD electrograms with a focus on likely target areas permit ablation without the need for PVC or VF induction. This can be useful when ectopy is not present for mapping and to avoid potentially dangerous initiation of multiple episodes of VF.

    View details for DOI 10.1111/pace.12019

    View details for Web of Science ID 000314658600021

    View details for PubMedID 23078144

  • Tachycardia-Induced Tachycardia JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY Heath, R., Sauer, W. H., Aleong, R., Duy Thai Nguyen 2012; 23 (12): 1390–92
  • Implantable Cardioverter Defibrillator Therapy in Patients with Cardiac Sarcoidosis JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY Schuller, J. L., Zipse, M., Crawford, T., Bogun, F., Beshai, J., Patel, A. R., Sweiss, N. J., Nguyen, D. T., Aleong, R. G., Varosy, P. D., Weinberger, H. D., Sauer, W. H. 2012; 23 (9): 925–29


    ICD Shocks in Cardiac Sarcoidosis.An implantable cardioverter defibrillator (ICD) is indicated for some patients with cardiac sarcoidosis (CS) for prevention of sudden death. However, there are little data regarding the event rates of ICD therapies in these patients. We sought to identify the incidence and characteristics of ICD therapies in this patient population.We performed a cohort study of patients with ICDs at 3 institutions. Cases were those patients with CS and an ICD implanted for primary or secondary prevention of sudden death. Additionally, we included a comparison with historical controls of ICD therapy rates reported in clinical trials evaluating the ICD for primary and secondary prevention of sudden death.Of the 112 CS subjects identified, 36 (32.1%) received appropriate therapies for ventricular tachyarrhythmias (VT) over a mean follow-up period of 29.2 months. VT storm (>3 episodes in 24 hours) occurred in 16 (14.2%) CS subjects. Inappropriate therapies occurred in 13 CS subjects (11.6%). Covariates associated with appropriate ICD therapies included left ventricular ejection fraction (LVEF) <55% (OR 6.52 [95% CI 2.43-17.5]), right ventricular dysfunction (OR 6.73 [95% CI 2.69-16.8]), and symptomatic heart failure (OR 4.33 [95% CI 1.86-10.1]).In our cohort of patients with CS and ICDs, almost one-third receive appropriate therapies. This may be due to a myocardial inflammatory process leading to increased triggered activity and subsequent scarring leading to reentrant tachyarrhythmias. Adjusted predictors of ICD therapies in this population include left or right ventricular dysfunction. (J Cardiovasc Electrophysiol, Vol. 23, pp. 925-929, September 2012).

    View details for DOI 10.1111/j.1540-8167.2012.02350.x

    View details for Web of Science ID 000308927900001

    View details for PubMedID 22812589

  • Utility of Cardiac Magnetic Resonance Imaging to Differentiate Cardiac Sarcoidosis from Arrhythmogenic Right Ventricular Cardiomyopathy AMERICAN JOURNAL OF CARDIOLOGY Steckman, D. A., Schneider, P. M., Schuller, J. L., Aleong, R. G., Nguyen, D. T., Sinagra, G., Vitrella, G., Brun, F., Cova, M. A., Pagnan, L., Mestroni, L., Varosy, P. D., Sauer, W. H. 2012; 110 (4): 575–79


    Some patients diagnosed with arrhythmogenic right ventricular cardiomyopathy (ARVC) are eventually found to have cardiac sarcoidosis (CS). Accurate differentiation between these 2 conditions has implications for immunosuppressive therapy and familial screening. We sought to determine whether cardiac magnetic resonance imaging (MRI) could be used to identify the characteristic findings to accurately differentiate between CS and ARVC. Consecutive patients with a diagnostic MRI scan indicating CS and/or ARVC constituted the cohort. All patients diagnosed with CS had histologic confirmation of sarcoidosis, and all patients with ARVC met the diagnostic task force criteria. The cardiac MRI data were retrospectively analyzed to identify possible differentiating characteristics. Of the patients, 40 had CS and 21 had ARVC. Those with CS were older and had more left ventricular scar. The presence of mediastinal lymphadenopathy or left ventricular septal involvement was seen exclusively in the patients with CS (p <0.001). A family history of sudden cardiac death was seen only in the ARVC group (p = 0.012). The right ventricular ejection fraction and ventricular volumes were also significantly different between the 2 groups. In conclusion, patients with CS have significantly different cardiac MRI characteristics than patients with ARVC. The cardiac volume, in addition to the degree and location of cardiac involvement, can be used to distinguish between these 2 disease entities. The presence of mediastinal lymphadenopathy and left ventricular septal scar favors a diagnosis of CS and not ARVC. Consideration of CS should be given if these MRI findings are observed during the evaluation for possible ARVC.

    View details for DOI 10.1016/j.amjcard.2012.04.029

    View details for Web of Science ID 000307861000019

    View details for PubMedID 22595349

  • Acquired premature ventricular ectopy after cardiac transplantation JOURNAL OF HEART AND LUNG TRANSPLANTATION Duy Thai Nguyen, Heath, R., Ambardekar, A., Sauer, W. 2012; 31 (7): 787–88

    View details for Web of Science ID 000305544700020

    View details for PubMedID 22503376

  • The Irregular Tachycardia That Was Not Atrial Fibrillation ARCHIVES OF INTERNAL MEDICINE Katz, D. F., Varosy, P. D., Nguyen, D. T., Schuller, J. L., Aleong, R. G., Heath, R. R., Sauer, W. H. 2011; 171 (22): 1985–88
  • Seizure-induced asystole HEART Steckman, D., Katz, D., Sauer, W., Nguyen, D. 2011; 97 (17): 1457

    View details for DOI 10.1136/heartjnl-2011-300277

    View details for Web of Science ID 000293575600017

    View details for PubMedID 21708820

  • Characteristics of Implantable Cardioverter-defibrillator Recipients for the Primary and Secondary Prevention of Sudden Cardiac Death in the Outcomes Among Veterans With Implantable Defibrillators (OVID) Registry Katz, D. F., Aleong, R. G., Pointer, L., Pelligrini, C. N., Sauer, W. H., Heath, R. R., Schuller, J., Nguyen, D. T., Heidenreich, P. A., Massie, B. M., Varosy, P. D. CHURCHILL LIVINGSTONE INC MEDICAL PUBLISHERS. 2011: S52–S53
  • Unusual Fibrillation in the Emergency Department After Fall CIRCULATION Zalkind, D., Aleong, R., Sauer, W., Duy Thai Nguyen 2011; 123 (25): E641–E642
  • A Mobile Tubular Mass Visualized by Transesophageal Echocardiography After Successful Lead Extraction CIRCULATION Heath, R. R., Schuller, J. L., Sauer, W. H., Varosy, P. D., Nguyen, D. T., Aleong, R. G. 2011; 123 (19): E590–E591
  • Life-Threatening ST-Segment Elevation Without Coronary Artery Disease ARCHIVES OF INTERNAL MEDICINE Heath, R. R., Varosy, P. D., Katz, D. F., Schuller, J. L., Aleong, R. G., Sauer, W. H., Nguyen, D. T. 2011; 171 (9): 801–3
  • Odynophagia After Atrial Fibrillation Ablation CIRCULATION Duy Thai Nguyen, Wang, Z., Vedantham, V., Badhwar, N. 2011; 123 (8): E253–E254
  • Supraventricular tachycardia with alternating cycle lengths: What is the mechanism? HEART RHYTHM Duy Thai Nguyen, Scheinman, M., Badhwar, N. 2011; 8 (3): 478–79

    View details for DOI 10.1016/j.hrthm.2010.04.037

    View details for Web of Science ID 000287736200031

    View details for PubMedID 20434588

  • Images in cardiovascular medicine. Odynophagia after atrial fibrillation ablation. Circulation Nguyen, D. T., Wang, Z. J., Vedantham, V. n., Badhwar, N. n. 2011; 123 (8): e253–4

    View details for DOI 10.1161/CIRCULATIONAHA.110.983924

    View details for PubMedID 21357841

  • Wenckebach During Supraventricular Tachycardia CIRCULATION-ARRHYTHMIA AND ELECTROPHYSIOLOGY Nguyen, D., Scheinman, M., Olgin, J., Badhwar, N. 2010; 3 (6): 671–73

    View details for DOI 10.1161/CIRCEP.110.959361

    View details for Web of Science ID 000285295500018

    View details for PubMedID 21156779

  • Supraventricular Tachycardia With No Ventriculoatrial Conduction: What Is the Mechanism? JOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY Nguyen, D., Scheinman, M., Badhwar, N. 2010; 21 (12): 1419–20
  • Pirfenidone mitigates left ventricular fibrosis and dysfunction after myocardial infarction and reduces arrhythmias HEART RHYTHM Nguyen, D. T., Ding, C., Wilson, E., Marcus, G. M., Olgin, J. E. 2010; 7 (10): 1438–45


    Post-myocardial infarction (MI) complications include ventricular tachycardia (VT). Excessive non-MI fibrosis, involving the infarct border zone (IBZ) and beyond, is an important substrate for VT vulnerability.This study assessed whether the antifibrotic agent pirfenidone can mitigate fibrosis in remodeling and determined its effects on myocardial function and VT susceptibility in a rodent MI model.We studied 2 groups of rats undergoing MI 1 week prior to treatment: a control group (n = 15) treated with placebo and a pirfenidone group (n = 15). We performed serial echocardiograms, and after 4 weeks of treatment, we conducted electrophysiological and optical mapping studies as well as histology.There was less decline in left ventricular (LV) ejection fraction for pirfenidone-treated rats, 8.6% versus 24.3% in controls (P <0.01). Pirfenidone rats also had lower rates of VT inducibility, 28.6% versus 73.3% in control rats (P <0.05). Furthermore, pirfenidone-treated rats had faster conduction velocities in their IBZs compared with controls, at all pacing cycle lengths (P <0.05). Rats treated with pirfenidone also had smaller infarct dense scar (8.9% of LV myocardium vs. 15.7% in controls, P <0.014), less total LV fibrosis (15% vs. 30% in controls, P <0.003), and less nonscar fibrosis (6.6% vs. 12.6% in controls, P <0.006).Pirfenidone decreased total and nonscar fibrosis in a rat MI model, which correlated with decreased infarct scar, improved LV function, and decreased VT susceptibility. Directly targeting post-MI fibrotic substrates may have a role in limiting infarct-dense scar, improving LV function, and reducing VT vulnerability.

    View details for DOI 10.1016/j.hrthm.2010.04.030

    View details for Web of Science ID 000282187300017

    View details for PubMedID 20433946

  • Supraventricular Tachycardia in Pulmonary Hypertension. Cardiac electrophysiology clinics Nguyen, D. T., Scheinman, M. 2010; 2 (2): 317–19


    Pulmonary hypertension is a disease with significant morbidity and mortality. It is characterized by right-sided volume and pressure overload, which leads to structural changes and fibrosis in the right atrium, thus predisposing to supraventricular arrhythmias. This article presents a case discussion of supraventricular tachycardia in pulmonary hypertension. A 48-year-old woman, with a history of primary pulmonary hypertension and right heart failure, was admitted with a supraventricular tachycardia, hypotension, and congestive heart failure.

    View details for DOI 10.1016/j.ccep.2010.01.025

    View details for PubMedID 28770773

  • High-Resolution Optical Mapping of Ventricular Tachycardia in Rats with Chronic Myocardial Infarction PACE-PACING AND CLINICAL ELECTROPHYSIOLOGY Ding, C., Gepstein, L., Duy Thai Nguyen, Wilson, E., Hulley, G., Beaser, A., Lee, R. J., Olgin, J. 2010; 33 (6): 687–95


    Ventricular tachycardia (VT) is a common cause of mortality in post-myocardial infarction (MI) patients, even in the current era of coronary revascularization treatment. We report a reproducible VT model in rats with chronic MI induced by ischemia-reperfusion and describe its electrophysiological characteristics using high-resolution optical mapping.An MI was generated by left anterior descending coronary ligation (25 minutes) followed by reperfusion in 20 rats. Electrophysiology study and optical mapping were performed 5 weeks later using a Langendorff-perfused preparation and compared to normal rats.The conduction velocity of the MI border zone was decreased to 53% of the normal areas remote from the infarct (0.37 +/- 0.16 m/sec vs 0.70 +/- 0.09 m/sec, P < 0.0001). The rate of VT inducibility in MI rats was significantly greater than in normal control rats (70% vs 0%, P = 0.00002). VT circuits involving the infarct area were identified with optical mapping in 83% MI rats. In addition, fixed and functional conduction block were observed in the infarct border zone.This ischemia-reperfusion MI rat model is a reliable VT model, which simulates clinical revascularization treatment. High-resolution optical mapping in this model is useful to study the mechanism of VT and evaluate the effects of therapies.

    View details for DOI 10.1111/j.1540-8159.2010.02704.x

    View details for Web of Science ID 000278818200007

    View details for PubMedID 20180914

  • Supraventricular Tachycardia After Atrial Fibrillation Ablation. Cardiac electrophysiology clinics Nguyen, D. T., Lee, R., Tseng, Z. H. 2010; 2 (2): 313–16


    Atrial arrhythmias occur commonly after atrial fibrillation (AF) ablation. Initial conservative management with medical therapy and cardioversion is reasonable, particularly in the early period (first 3 months) after ablation, because many of these arrhythmias remit over time. However, definitive therapy with ablation may be required, depending on the clinical circumstances, and should focus on the putative mechanism of tachycardia and its likely location, both of which can be suggested by the initial AF ablation strategy. Response to pacing, entrainment, and electroanatomic activation mapping are useful to confirm the mechanism, define complex circuits, and guide ablation targets.

    View details for DOI 10.1016/j.ccep.2010.01.024

    View details for PubMedID 28770772

  • Ventricular Tachycardia After Implantable Cardioverter-Defibrillator Placement. Cardiac electrophysiology clinics Nguyen, D. T., Tseng, Z. H., Lee, B. K., Badhwar, N. 2010; 2 (2): 277–80


    Although implantation of an endocardial implantable cardioverter defibrillator (ICD) is meant to protect against ventricular arrhythmias, in some cases it can be paradoxically pro-arrhythmic. Recognition of this device complication, while rare, is important because it is potentially reversible and can be treated by managing the device, in lieu of, or in addition to, antiarrhythmics and catheter ablation of ventricular tachycardia (VT). This case describes VT caused by right ventricular pacing after ICD implantation.

    View details for DOI 10.1016/j.ccep.2010.01.013

    View details for PubMedID 28770763

  • Supraventricular Tachycardia and Atrioventricular Block. Cardiac electrophysiology clinics Nguyen, D. T., Badhwar, N. 2010; 2 (2): 235–38


    The differential diagnosis for a mid- to long-RP supraventricular tachycardia include atrial tachycardia, atypical atrioventricular nodal reentrant tachycardia (AVNRT), and atrioventricular reentrant tachycardia (AVRT) utilizing a slowly conducting concealed accessory pathway. The presence of spontaneous atrioventricular block excludes AVRT. This case reviews pacing maneuvers to distinguish atrial tachycardia from AVNRT. Atypical AVNRT generally demonstrates the presence of a lower common pathway and has its site of earliest retrograde atrial activation near the coronary sinus ostium, which would be the target for ablation.

    View details for DOI 10.1016/j.ccep.2010.01.010

    View details for PubMedID 28770757

  • A Case of Atrial Arrhythmia After Lung Transplant. Cardiac electrophysiology clinics Nguyen, D. T., Marcus, G. M. 2010; 2 (2): 295–98


    A case of atrial arrhythmia after lung transplant is presented. The key features of this case are relevant to most atypical flutters. A combination of entrainment and electroanatomic mapping can help to efficiently identify the culprit area. The target is typically a long mid-diastolic fractionated potential shown to be integral to the circuit by entrainment mapping. A micro-reentrant circuit may appear to be focal by the electroanatomic map, but entrainment techniques can still be used to localize the tachycardia.

    View details for DOI 10.1016/j.ccep.2010.01.017

    View details for PubMedID 28770768

  • Regulation of the Werner helicase through a direct interaction with a subunit of protein kinase A FEBS LETTERS Nguyen, D. T., Rovira, Finkel, T. 2002; 521 (1-3): 170–74


    Werner syndrome is a hereditary disease characterized by cancer predisposition, genetic instability, and the premature appearance of features associated with normal aging. At the molecular level this syndrome has been related to mutations in the Werner helicase, a member of the RecQ family of DNA helicases which are required to maintain genomic stability in cells. Here we show by a yeast two-hybrid screen that the Werner helicase can directly interact with the regulatory subunit (RIbeta) of cAMP protein kinase A (PKA). We confirm that this interaction occurs in vivo. Interestingly, serum withdrawal causes a redistribution of the Werner helicase within the nucleus of mammalian cells. Raising intracellular cAMP levels or increased expression of the regulatory but not the catalytic subunit of PKA inhibits this nuclear redistribution stimulated by serum deprivation. These results suggest that similar to lower organisms, gene products linked to genomic instability and aging may be directly regulated by growth factor-sensitive, PKA-dependent pathways.

    View details for DOI 10.1016/S0014-5793(02)02868-5

    View details for Web of Science ID 000176443600034

    View details for PubMedID 12067711