The Influence of Leaflet Hemodynamics and Stress on Calcification in Modern Biological Aortic Valves: A Fluid-Structural Interaction Simulation Study

Abstract

A surgical bioprosthetic heart valve is crafted from biological tissue, commonly sourced from animals such as bovine or porcine. Despite the advantages offered by bioprostheses, their notable drawback is a shorter lifespan compared to mechanical valves. This reduced longevity primarily stems from structural valve deterioration, predominantly caused by issues such as calcification, wear and tear of the leaflets, and other related factors. These a forementioned challenges contribute to valve malfunction, necessitating patients to undergo subsequent surgeries for valve replacement. Factors influencing valve degeneration, including calcification, leaflet wear and tear, may originate from heightened stress on the leaflets, coupled with valve hemodynamics. A comprehensive understanding of the valve’s functioning and crucial parameters like stress distribution on the leaflets can be achieved through a two-way Fluid-Structure Interaction analysis. To conduct this simulation, the robust software package ANSYS was utilized. ANSYS employs sophisticated numerical techniques and algorithms to tackle a wide spectrum of engineering predicaments. In this research, a μCT scan of a surgically implanted aortic bioprosthetic valve was employed to generate accurate representations of the valve’s leaflets and stent. To enhance precision, a modified aortic root and ascending aorta were designed to account for the impact of the arc-shaped geometry of the ascending aorta. The study aimed to evaluate key parameters, including blood streamline patterns across the sinuses and wall shear stress over the leaflets and ascending aorta. Mechanicalattributes of the leaflets were investigated through an analysis of principal stress and strain distribution.Of critical significance to medical practitioners, the effective orifice area was calculated, offering insights into valve performance.The simulation results indicate increased mechanical stress in regions near the stent and the leaflet’s central area. Additionally, there were relatively higher wall shear stress values observed over the left and right coronary cusps compared to the non-coronary cusp, although the latter was nearly negligible. Notably, the streamline patterns of blood flow displayed some asymmetry due to the aorta’sarc-shaped geometry, although these differences were not significant. This curvature of the aorta has a notable influence on the downstream blood flow from the valve, although it only marginally affects valve hemodynamics. It’s worth noting that most of previous studies addressing valve hemodynamicsoften omitted the ascending aorta from their models or assumed it to be a simple cylindrical shape. Furthermore, it’s worth acknowledging that coronary arteries were not accounted for in this study, even though they can potentially impact the outcomes. Therefore, we also recommend including coronary arteries in future research efforts.