Measuring Stress on a Third-Generation Balloon-Expandable Aortic Valve During Expansion.

Abstract

This study aimed to determine the mechanical stresses experienced by third-generation, balloon-expandable transcatheter aortic valves in the presence of aortic calcification, defined by an elevated Agatston score index for calcium. The device under investigation was the Edwards SAPIEN 3 valve (referred to as S3-TAV henceforth), a 26-mm commercial device. Five steps were undertaken. The first was the reconstruction of the three-dimensional (3D) computer-aided design (CAD) model of the device. The second was a simulation of the crimping and reopening process. The third was evaluating the crimping effect on leaflet stress and a comparison to an ideal condition. The fourth was a simulation of real clinical cases. Finally, the subsequent phase of the study entails the post-processing of the simulation results and a comparison with the follow-up data. A high-resolution micro-computed tomography scan was used to develop an accurate 3D geometric mesh of the stent and the valve. The material properties of the leaflets were derived from surgical bioprostheses; the material properties of the stents were based on those of cobalt-chromium. A series of simulations were conducted to assess the impact of systemic pressure loading on the structure. Stress was quantified through the application of finite element analyses. A stress analysis of the valve, conducted using exact geometry derived from high-resolution scans, revealed that peak stresses during the crimping phase were concentrated at the commissural tips, where the leaflets were attached. These regions were identified as the most likely sites for thrombosis and degeneration. The persistence of bulky calcifications following the device expansion results in the formation of paravalvular leakages (PVLs), which act as precursors to thrombosis and structural valve degeneration.