Stanford Advisors


All Publications


  • Patient-Specific Multiscale Modeling of the Assisted Bidirectional Glenn. The Annals of thoracic surgery Shang, J. K., Esmaily, M., Verma, A., Reinhartz, O., Figliola, R. S., Hsia, T., Feinstein, J. A., Marsden, A. L. 2018

    Abstract

    BACKGROUND: First-stage palliation of neonates with single-ventricle physiology is associated with poor outcomes and challenging clinical management. Prior computational modeling and invitro experiments introduced the assisted bidirectional Glenn (ABG), which increased pulmonary flow and oxygenation over the bidirectional Glenn (BDG) and the systemic-to-pulmonary shunt in idealized models. In this study, we demonstrate that the ABG achieves similar performance in patient-specific models and assess the influence of varying shunt geometry.METHODS: In a small cohort of single-ventricle prestage 2 patients, we constructed three-dimensional in silico models and tuned lumped parameter networks to match clinical measurements. Each model was modified to produce virtual BDG and ABG surgeries. We simulated the hemodynamics of the stage 1 procedure, BDG, and ABG by using multiscale computational modeling, coupling a finite-element flow solver to the lumped parameter network. Two levels of pulmonary vascular resistances (PVRs) were investigated: baseline (low) PVR of the patients and doubled (high) PVR. The shunt nozzle diameter, anastomosis location, and shape were also manipulated.RESULTS: The ABG increased the pulmonary flow rate and pressure by 15% to 20%, which was accompanied by a rise in superior vena caval pressure (2 to 3 mm Hg) at both PVR values. Pulmonary flow rate and superior vena caval pressures were most sensitive to the shunt nozzle diameter.CONCLUSIONS: Patient-specific ABG performance was similar to prior idealized simulations and experiments, with good performance at lower PVR values in the range of measured clinical data. Larger shunt outlet diameters and lower PVR led to improved ABG performance.

    View details for DOI 10.1016/j.athoracsur.2018.10.024

    View details for PubMedID 30471273

  • Optimization of the Assisted Bidirectional Glenn Procedure for First Stage Single Ventricle Repair Optimization of the Assisted Bidirectional Glenn Procedure for First Stage Single Ventricle Repair Verma, A., Esmaily, M., Shang, J., Figliola, R., Feinstein, J., Hsia, T., Marsden, A. 2018; 9 (2): 157-170

    Abstract

    First-stage single-ventricle palliation is challenging to manage, and significant interstage morbidity and mortality remain. Prior computational and in vitro studies of the assisted bidirectional Glenn (ABG), a novel first-stage procedure that has shown potential for early conversion to a more stable augmented Glenn physiology, demonstrated increased pulmonary flow and oxygen delivery while decreasing cardiac work, as compared to conventional stage-1 alternatives. This study aims to identify optimal shunt designs for the ABG to improve pulmonary flow while maintaining or decreasing superior vena caval (SVC) pressure.A representative three-dimensional model of a neonatal bidirectional Glenn (BDG) was created, with a shunt connecting the innominate artery to the SVC. The shunt design was studied as a six-parameter constrained shape optimization problem. We simulated hemodynamics for each candidate designs using a multiscale finite element flow solver and compared performance against designs with taper-less shunts, the standalone BDG, and a simplified control volume model. Three values of pulmonary vascular resistance (PVR) of 2.3, 4.3, and 7.1 WUm2 were studied.Increases in pulmonary flow were generally accompanied by increases in SVC pressure, except at low PVR (2.3 WUm2), where the optimal shunt geometry achieved a 13% increase in pulmonary flow without incurring any increase in SVC pressure. Shunt outlet area was the most influential design parameter, while others had minimal effect.Assisted bidirectional Glenn performance is sensitive to PVR and shunt outlet diameter. An increase in pulmonary flow without a corresponding increase in SVC pressure is possible only when PVR is low.

    View details for DOI 10.1177/2150135117745026

  • Optimizing fluid-structure interaction systems with immersogeometric analysis and surrogate modeling: Application to a hydraulic arresting gear COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING Wu, M. C., Kamensky, D., Wang, C., Herrema, A. J., Xu, F., Pigazzini, M. S., Verma, A., Marsden, A. L., Bazilevs, Y., Hsu, M. 2017; 316: 668-693