Computational construction and simulation of novel heart valve and vein valve designs

Abstract

As a heart valve substitute with growth potential and improved durability, tissue-engineered heart valves can prevent reinterventions that are currently often needed in children with congenital heart defects. Our group successfully made a pediatric tri-tube/tri-leaflet valved conduit which has shown growth capability in growing lambs. However, the optimal design for valve performance is unknown. To obtain optimal values of valve geometry parameters which can provide efficient guidance for animal tests to save costs and time, we utilized computer-aided simulations to evaluate multiple valve designs. We performed both the valve construction process and this optimization in silico. This is a complex optimization problem due to multiple components of the objective function for valve performance. We thus applied a multi-objective genetic algorithm, which is an elitist strategy, a parameter-free, simple, yet efficient, constraint-handling method used in many applications. A robust finite element method (FEM)-based algorithm for in silico construction of the valve was developed to facilitate optimization for the case of valve closure, identifying the optimal leaflet height and tube diameter that minimizes peak diastolic stress and maximizes coaptation. A strain energy constitutive equation for our novel material, an aligned tissue grown in the lab, was developed based on biaxial testing and implemented in the FEM model. Fluid-structure interaction (FSI) simulation of the optimal design under steady flow was also conducted as a prelude to a next-stage optimization that includes valve dynamic performance metrics. The same methods for the heart valve were also applied to the computational construction and simulation of a stented bileaflet venous valve that includes a sinus design. Steady FSI simulations were used to investigate the effects of the sinus geometry and non-Newtonian blood rheology on the hemodynamics of the novel transcatheter venous valve.