The influence of leaflet flutter of the aortic valve bioprostheses on leaflet calcification and endothelial activation

Abstract

Biological heart valve (BHV) prostheses have a short lifespan, since they are also susceptible to processes that trigger calcification that are observed in native valves. Studies indicate that the development of leaflet flutter may be related to the acceleration of the calcification mechanisms of these prostheses, as well as to the increase in endothelial cell activation. This study aims to evaluate the impact of leaflet flutter on parameters based on wall shear stress, used to verify calcification progression and ”thrombogenic susceptibility”, by performing fluid-structural computational calculations. The Arbitrary Lagrangian–Eulerian method was used to perform the computational analysis in a simplified domain applying physiological boundary conditions. The blood was modeled as a Newtonian fluid and the valve as a hyperelastic and isotropic incompressible material. The time-averaged wall shear stress (TAWSS), the relative residence time (RRT), the oscillatory shear index (OSI), and the endothelial cell activation potential (ECAP) were calculated to verify the impact of flutter on calcification and thrombogenesis of the prostheses. The results indicate that the accentuated curvatures developed after the oscillations started in the belly regions and between the free edge and the commissure of the leaflets are connected to the increase in OSI, RRT, and ECAP. Therefore, leaflet flutter is responsible for increasing mineral accumulation and platelet adhesion. Furthermore, the distributions of these quantities were different for each of the leaflets. This work aims to improve the understanding of the mechanisms involved in BHV degradation and provides supports for the manufacture of more durable prostheses.