Seraina A. Dual is a postodoctoral fellow at the departments of Radiology at Stanford Medicine and Mechanical Engineering at Stanford University, mentored by Prof. Doff McElHinney, Prof. Daniel Ennis, and Prof. Alison Marsden. She graduated with a Bachelor's degree from the Federal Institute of Technology Zurich (ETH Zurich) in Mechanical Engineering, a master's degree at ETH Zurich in Mechanical Engineering with a specialization in robotics and biomedical application with Prof. Roger Gassert, and her Dr. of science at ETH Zurich in Mechanical Engineering with Prof. Mirko Meboldt. During this time, she spent some time with Prof. Ellen Kuhl at Stanford University (BSc), with Prof. Theo Chee Leong at National University of Singapore (MSc), and with Prof. Christopher Hayward at the St. Vincent's Hospital in Sydney (DSc). Her work focuses on developing dynamic systems, algorithms, and sensors inspired by her background in engineering and control methodology to either improve our pathophysiological understanding of disease or enable physiological interaction of patients with intelligent medical devices.
DSc., ETH Zurich, Mechanical Engineering (2019)
MSc., ETH Zurich, Mechanical Engineering - Robotics and Biomedical (2015)
BSc., ETH Zurich, Mechanical Engineering (2012)
Daniel Ennis, Postdoctoral Faculty Sponsor
Does Size Matter for Female Continuous-flow LVAD Recipients? A Translational Approach to a Decade Long Question.
ASAIO journal (American Society for Artificial Internal Organs : 1992)
Females have increased risk of right-ventricular failure (RVF) and 3 month mortality after left-ventricular assist device (LVAD) implantation. In this translational study, we tested the hypothesis that sex differences in outcomes are driven by pump-induced LV size-volume mismatch, due to a negative impact on interventricular septal (IVS) interdependence. Adult continuous-flow LVAD recipients from the International Society For Heart And Lung Transplantation Mechanically Assisted Circulatory Support registry (n = 15,498) were studied to determine association of female sex with outcomes of 3 month mortality and RVF. Female sex was associated with smaller preimplant left-ventricular end-diastolic diameter (6.5 vs. 6.9 cm, p < 0.001), increased 3 month mortality (odds ratio [OR]: 1.42, p < 0.001) and RVF (OR: 1.18, p = 0.005). Smaller left-ventricular end-diastolic diameter was associated with worse outcomes after LVAD implantation (OR for mortality: 1.20, p < 0.001; RVF: 1.09, p < 0.001), and attenuated the association of female sex with these outcomes. In test bench heart phantoms (n = 4), the IVSs of smaller hearts demonstrated abnormal leftward shift earlier than larger hearts (volume change at IVS shift: 40 [95% confidence interval: 30-52] vs. 50 [95% confidence interval: 48-69] ml). Smaller LV size partially mediates worse post-LVAD outcomes for female patients, due to lower volume thresholds for adverse IVS shifting.
View details for DOI 10.1097/MAT.0000000000001443
View details for PubMedID 34156789
Right Ventricular Function and T1-Mapping in Boys With Duchenne Muscular Dystrophy.
Journal of magnetic resonance imaging : JMRI
BACKGROUND: Clinical management of boys with Duchenne muscular dystrophy (DMD) relies on in-depth understanding of cardiac involvement, but right ventricular (RV) structural and functional remodeling remains understudied.PURPOSE: To evaluate several analysis methods and identify the most reliable one to measure RV pre- and postcontrast T1 (RV-T1) and to characterize myocardial remodeling in the RV of boys with DMD.STUDY TYPE: Prospective.POPULATION: Boys with DMD (N=27) and age-/sex-matched healthy controls (N=17) from two sites.FIELD STRENGTH/SEQUENCE: 3.0T using balanced steady state free precession, motion-corrected phase sensitive inversion recovery and modified Look-Locker inversion recovery sequences.ASSESSMENT: Biventricular mass (Mi), end-diastolic volume (EDVi) and ejection fraction (EF) assessment, tricuspid annular excursion (TAE), late gadolinium enhancement (LGE), pre- and postcontrast myocardial T1 maps. The RV-T1 reliability was assessed by three observers in four different RV regions of interest (ROI) using intraclass correlation (ICC).STATISTICAL TESTS: The Wilcoxon rank sum test was used to compare RV-T1 differences between DMD boys with negative LGE(-) or positive LGE(+) and healthy controls. Additionally, correlation of precontrast RV-T1 with functional measures was performed. A P-value <0.05 was considered statistically significant.RESULTS: A 1-pixel thick RV circumferential ROI proved most reliable (ICC>0.91) for assessing RV-T1. Precontrast RV-T1 was significantly higher in boys with DMD compared to controls. Both LGE(-) and LGE(+) boys had significantly elevated precontrast RV-T1 compared to controls (1543 [1489-1597] msec and 1550 [1402-1699] msec vs. 1436 [1399-1473] msec, respectively). Compared to healthy controls, boys with DMD had preserved RVEF (51.8 [9.9]% vs. 54.2 [7.2]%, P=0.31) and significantly reduced RVMi (29.8 [9.7]g vs. 48.0 [15.7]g), RVEDVi (69.8 [29.7]mL/m2 vs. 89.1 [21.9]mL/m2 ), and TAE (22.0 [3.2]cm vs. 26.0 [4.7]cm). Significant correlations were found between precontrast RV-T1 and RVEF (beta=-0.48%/msec) and between LV-T1 and LVEF (beta=-0.51%/msec).DATA CONCLUSION: Precontrast RV-T1 is elevated in boys with DMD compared to healthy controls and is negatively correlated with RVEF.LEVEL OF EVIDENCE: 1 TECHNICAL EFFICACY: Stage 2.
View details for DOI 10.1002/jmri.27729
View details for PubMedID 34037289
Real-Time Ventricular Volume Measured Using the Intracardiac Electromyogram.
ASAIO journal (American Society for Artificial Internal Organs : 1992)
Left ventricular end-diastolic volume (EDV) is an important parameter for monitoring patients with left ventricular assist devices (LVADs) and might be useful for automatic LVAD work adaptation. However, continuous information on the EDV is unavailable to date. The depolarization amplitude (DA) of the noncontact intracardiac electromyogram (iEMG) is physically related to the EDV. Here, we show how a left ventricular (LV) volume sensor based on the iEMG might provide beat-wise EDV estimates. The study was performed in six pigs while undergoing a series of controlled changes in hemodynamic states. The LV volume sensor consisted of four conventional pacemaker electrodes measuring the far-field iEMG inside the LV blood pool, using a novel unipolar amplifier. Simultaneously, noninvasive measurements of EDV and hematocrit were recorded. The proposed EDV predictor was tested for statistical significance using a mixed-effect model and associated confidence intervals. A statistically significant (p = 3e-07) negative correlation was confirmed between the DA of the iEMG and the EDV as measured by electric impedance at a slope of -0.069 (-0.089, -0.049) mV/mL. The DA was slightly decreased by increased hematocrit (p = 0.039) and moderately decreased with the opening of the thorax (p = 0.003). The DA of the iEMG proved to be a significant, independent predictor of EDV. The proposed LV volume sensor is simple to integrate into the inflow cannula of an LVAD and thus has the potential to inform the clinician about the state of LV volume in real time and to automatically control the LVAD.
View details for DOI 10.1097/MAT.0000000000001444
View details for PubMedID 33899813
On the impact of vessel wall stiffness on quantitative flow dynamics in a synthetic model of the thoracic aorta.
2021; 11 (1): 6703
Aortic wall stiffening is a predictive marker for morbidity in hypertensive patients. Arterial pulse wave velocity (PWV) correlates with the level of stiffness and can be derived using non-invasive 4D-flow magnetic resonance imaging (MRI). The objectives of this study were twofold: to develop subject-specific thoracic aorta models embedded into an MRI-compatible flow circuit operating under controlled physiological conditions; and to evaluate how a range of aortic wall stiffness impacts 4D-flow-based quantification of hemodynamics, particularly PWV. Three aorta models were 3D-printed using a novel photopolymer material at two compliant and one nearly rigid stiffnesses and characterized via tensile testing. Luminal pressure and 4D-flow MRI data were acquired for each model and cross-sectional net flow, peak velocities, and PWV were measured. In addition, the confounding effect of temporal resolution on all metrics was evaluated. Stiffer models resulted in increased systolic pressures (112, 116, and 133 mmHg), variations in velocity patterns, and increased peak velocities, peak flow rate, and PWV (5.8-7.3 m/s). Lower temporal resolution (20 ms down to 62.5 ms per image frame) impacted estimates of peak velocity and PWV (7.31 down to 4.77 m/s). Using compliant aorta models is essential to produce realistic flow dynamics and conditions that recapitulated in vivo hemodynamics.
View details for DOI 10.1038/s41598-021-86174-6
View details for PubMedID 33758315
Continuous Heart Volume Monitoring by Fully Implantable Soft Strain Sensor.
Advanced healthcare materials
Cardiothoracic open-heart surgery has revolutionized the treatment of cardiovascular disease, the leading cause of death worldwide. After the surgery, hemodynamic and volume management can be complicated, for example in case of vasoplegia after endocarditis. Timely treatment is crucial for outcomes. Currently, treatment decisions are made based on heart volume, which needs to be measured manually by the clinician each time using ultrasound. Alternatively, implantable sensors offer a real-time window into the dynamic function of our body. Here it is shown that a soft flexible sensor, made with biocompatible materials, implanted on the surface of the heart, can provide continuous information of the heart volume after surgery. The sensor works robustly for a period of two days on a tensile machine. The accuracy of measuring heart volume is improved compared to the clinical gold standard in vivo, with an error of 7.1mL for the strain sensor versus impedance and 14.0mL versus ultrasound. Implanting such a sensor would provide essential, continuous information on heart volume in the critical time following the surgery, allowing early identification of complications, facilitating treatment, and hence potentially improving patient outcome.
View details for DOI 10.1002/adhm.202000855
View details for PubMedID 32893478
Ultrasound-based prediction of interventricular septum positioning during left ventricular support-an experimental study.
Journal of cardiovascular translational research
The implantation of left ventricular assist devices (LVADs) is often complicated by arrhythmias and right ventricular failure (RVF). Today, the pump speed is titrated to optimize device support using single observations of interventricular septum (IVS) positioning with echocardiographic ultrasound (US). The study demonstrates the applicability of three integrated US transducers in the LVAD cannula to monitor IVS positioning continuously and robustly in real time. In vitro, the predictor of the IVS shift shows an overall prediction error for all volume states of less than 20% and provides a continuous assessment for 99% of cases in four differently sized heart phantoms. The prediction of IVS shift depending on the cannula position is robust for azimuthal and polar deviations of ± 20° and ± 8°, respectively. This intracardiac US concept results in a viable predictor for IVS positioning and represents a promising approach to continuously monitor the IVS and ventricular loading in LVAD patients. Graphical abstract.
View details for DOI 10.1007/s12265-020-10034-3
View details for PubMedID 32671647
Short-term physiological response to high-frequency-actuated pVAD support
2019; 43 (12): 1170–81
Ventricular assist devices (VADs) are an established treatment option for heart failure (HF). However, the devices are often plagued by material-related hemocompatibility issues. In contrast to continuous flow VADs with high shear stresses, pulsatile VADs (pVADs) offer the potential for an endothelial cell coating that promises to prevent many adverse events caused by an insufficient hemocompatibility. However, their size and weight often precludes their intracorporeal implantation. A reduction of the pump body size and weight of the pump could be achieved by an increase in the stroke frequency while maintaining a similar cardiac output. We present a new pVAD system consisting of a pump and an actuator specifically designed for actuation frequencies of up to 240 bpm. In vitro and in vivo results of the short-term reaction of the cardiovascular system show no significant changes in left ventricular and aortic pressure between actuation frequencies from 60 to 240 bpm. The aortic pulsatility increases when the actuation frequency is raised while the heart rate remains unaffected in vivo. These results lead us to the conclusion that the cardiovascular system tolerates short-term increases of the pVAD stroke frequencies.
View details for DOI 10.1111/aor.13521
View details for Web of Science ID 000479706100001
View details for PubMedID 31211873
- Acute changes in preload and the QRS amplitude in advanced heart failure patients BIOMEDICAL PHYSICS & ENGINEERING EXPRESS 2019; 5 (4)
Ultrasonic sensor concept to fit a ventricular assist device cannula evaluated using geometrically accurate heart phantoms
2019; 43 (5): 467–77
Future left ventricular assist devices (LVADs) are expected to respond to the physiologic need of patients; however, they still lack reliable pressure or volume sensors for feedback control. In the clinic, echocardiography systems are routinely used to measure left ventricular (LV) volume. Until now, echocardiography in this form was never integrated in LVADs due to its computational complexity. The aim of this study was to demonstrate the applicability of a simplified ultrasonic sensor to fit an LVAD cannula and to show the achievable accuracy in vitro. Our approach requires only two ultrasonic transducers because we estimated the LV volume with the LV end-diastolic diameter commonly used in clinical assessments. In order to optimize the accuracy, we assessed the optimal design parameters considering over 50 orientations of the two ultrasonic transducers. A test bench was equipped with five talcum-infused silicone heart phantoms, in which the intra-ventricular surface replicated papillary muscles and trabeculae carnae. The end-diastolic LV filling volumes of the five heart phantoms ranged from 180 to 480 mL. This reference volume was altered by ±40 mL with a syringe pump. Based on the calibrated measurements acquired by the two ultrasonic transducers, the LV volume was estimated well. However, the accuracies obtained are strongly dependent on the choice of the design parameters. Orientations toward the septum perform better, as they interfere less with the papillary muscles. The optimized design is valid for all hearts. Considering this, the Bland-Altman analysis reports the LV volume accuracy as a bias of ±10% and limits of agreement of 0%-40% in all but the smallest heart. The simplicity of traditional echocardiography systems was reduced by two orders of magnitude in technical complexity, while achieving a comparable accuracy to 2D echocardiography requiring a calibration of absolute volume only. Hence, our approach exploits the established benefits of echocardiography and makes them applicable as an LV volume sensor for LVADs.
View details for DOI 10.1111/aor.13379
View details for Web of Science ID 000467448200006
View details for PubMedID 30357874
ConVes: The Sutureless Aortic Graft Anastomotic Device
ANNALS OF THORACIC SURGERY
2018; 105 (5): 1558–62
Less invasive left ventricular assist device implantation became feasible with the development of smaller devices. This study evaluated a sutureless aortic anastomosis device to facilitate the implant procedure.The novel anastomotic device deploys and anchors an acute-angled stent in the aortic wall to create a sutureless outflow graft anastomosis in the ascending aorta. Four aortic anastomoses were performed on the beating hearts of two pigs without cross-clamping or cardiopulmonary bypass.The procedure was fast and simple. The time of anastomosis averaged 8.1 minutes, with merely oral instructions to the operating surgeon. The design of the stent allowed the outflow graft to be implanted with the intended angulation of 45 degrees.This proof-of-concept study demonstrates the feasibility and short-term success of the proposed sutureless anastomotic device. Further preclinical studies are necessary to evaluate long-term durability of the anastomosis.
View details for DOI 10.1016/j.athoracsur.2017.11.010
View details for Web of Science ID 000430515700055
View details for PubMedID 29530280
Standardized Comparison of Selected Physiological Controllers for Rotary Blood Pumps: In Vitro Study
2018; 42 (3): E29–E42
Various physiological controllers for left ventricular assist devices (LVADs) have been developed to prevent flow conditions that may lead to left ventricular (LV) suction and overload. In the current study, we selected and implemented six of the most promising physiological controllers presented in literature. We tuned the controllers for the same objectives by using the loop-shaping method from control theory. The in vitro experiments were derived from literature and included different preload, afterload, and contractility variations. All experiments were repeated with an increased or decreased contractility from the baseline pathological circulation and with simulated sensor drift. The controller performances were compared with an LVAD operated at constant speed (CS) and a physiological circulation. During preload variations, all controllers resulted in a pump flow change that resembled the cardiac output response of the physiological circulation. For afterload variations, the response varied among the controllers, whereas some of them presented a high sensitivity to contractility or sensor drift, leading to LV suction and overload. In such cases, the need for recalibration of the controllers or the sensor is indicated. Preload-based physiological controllers showed their clinical significance by outperforming the CS operation and promise many benefits for the LVAD therapy. However, their clinical implementation in the near future for long-term use is highly dependent on the sensor technology and its reliability.
View details for DOI 10.1111/aor.12999
View details for Web of Science ID 000426840000001
View details for PubMedID 29094351