Session: 12-26-01: Data-Driven Modeling and Simulation for Computational Biomedicine

Paper Number: 69932

Start Time: Friday, 03:25 PM

69932 - Complementing Regulatory Evidence Through Numerical Simulation Tests: An Application Case for Fluid Stagnation After Lvad Implantation 

Purpose of Study:

The recently published ASME standard: Assessing Credibility of Computational Modeling Through Verification and Validation: Application to Medical Devices (V&V40) provides a risk-informed assessment framework to aid in regulatory evaluation of medical devices. The framework centers on determining model credibility from risk associated with decisions based on the computational model. This project aims to apply V&V40 to a numerical model of the left ventricle (LV) during support with a LV assist device (LVAD), a therapy for patients with advanced heart failure. Despite improved survival, complications like thrombosis exist in 20% of cases. Flow in the heart involves complex fluid transport as well as the dynamical interactions between the incoming and residual flows which are drastically altered with LVAD support. Evidence suggests that the LV is a relevant site of thrombus formation and is related to intra-LV stagnation, which can be quantified with surrogate biomarkers computed from flow fields such as velocity, vorticity and pulsatility. 

Methods:

A benchtop circulatory loop developed at San Diego State University that reproduces the dynamic flow patterns in the left ventricle (LV) of heart failure patients will be used in combination with a HeartMate II LVAD (Abbott, Inc). High-frequency pressure and flow signals are recorded while the time-varying flow field within a beating silicone LV is measured with particle image velocimetry (PIV). In these studies, a silicone LV supported by a HeartMate II LVAD was tested for an ejection fraction of 22% in combination with three LVAD speeds (0, 8k, and 11k rpm). A corresponding computational model was formulated with Alya software, a simulation code developed at Barcelona Supercomputing Center (BSC) designed to efficiently use large-scale computing facilities in multiscale multi-physics problems. Boundary conditions reflecting the measured pressure and LV geometry were used to solve the fluid dynamics problem. Heart valves are modeled through a pressure-driven porous medium and the LVAD through its H-Q performance curve.

Summary of Results:

The computational results closely reflect the major flow characteristics observed in the bench experiments. The pressure and flow predictions match the sensor measurements closely, with some oscillations in the response introduced by the valve models. The midplane velocity fields of the experimental and computational studies compared favorably, with a central LV vortex that grows during diastole and ejection through the apical LVAD cannula during systole. Quantitative comparison of vortex dynamics, residence time and shear activation potential will capture the uncertainty following V&V40, a computationally expensive task but currently underway. Upon completion, the computational model is intended to predict biomarker stagnation which, in turn, will help during the regulatory process to accelerate the time-to-market of novel devices.

Presenting Author: Alfonso Santiago Barcelona Supercomputing Center

Authors:

Alfonso Santiago Barcelona Supercomputing Center
Karen May-Newman San Diego State University
Richard A. Gray Food and Drug Administration
Timothy J. Baldwin Food and Drug Administration
Beatriz Eguzkitza Barcelona Supercomputing Center
Mariano Vazquez Barcelona Supercomputing Center