Computational approaches for the analysis of biological prosthetic heart valve

Computational approaches for prosthetic heart valves can yield detailed insights of functional and structural effects of implants, especially when structural and fluid-dynamic analyses are combined to carry out fluidstructure interaction (FSI) studies. In order to take full advantage of this emerging computational approach and gain confidence on its results when applied to the design of complex devices, like biological prosthetic heart valves, modeling strategies must consider different aspects, including accurate description of valve geometry, mechanical behavior of leaflets biological tissue and validation of model results with experimental data. In the present work a design methodology is presented in which a combined experimental and numerical approach is applied to the analysis of a commercial prosthetic aortic valve, consisting of a polymeric stent which supports leaflets made with bovine pericardium. The first stage of the work consisted in the generation of an accurate geometric model of the valve. The complex shape of the leaflets was reconstructed by means of high precision 3D laser scanning system. The point cloud representing external surface obtained from scanning was then imported in CAD software to generate a virtual and accurate model of actual valve dimensions and geometry. In the second stage CAD model was imported into FEM code to perform computational simulations, which consisted of structural and combined fluid-structural analyses. Structural analyses were carried out to study the stress distribution and leaflet deformation in response to applied pressure both in opening and closing phase of the cardiac cycle. Models included contact interactions between the leaflets and hyperelastic constitutive laws to represent leaflets complex mechanical behavior. Fluid-structure interaction analyses, in which also the fluid domain is modeled, were carried out to simulate valve opening. Finally FSI model results were compared with those obtained experimentally on the same valve mounted on a valve test bench, with a good agreement of results in terms of pressure drop across the valve and shape of the orifice in the deformed configuration.