A numerical study to investigate the impact of cell size of self-expanding aortic valve stents on paravalvular leakage

Abstract Transcatheter aortic valve replacement (TAVR) has become the standard treatment of multimorbid patients with severe aortic valve stenosis. One frequently observed complication after TAVR procedure is the occurence of paravalvular leakage (PVL). PVL is caused by a gap between the vessel wall and the TAVR stent, enabling blood to flow from the aorta back to the ventricle during diastolic phase. A high PVL rate leads to increased mortality of TAVR patients. To avoid this complication, pericardial skirts were developed by manufacturers to seal the leakage gap. Furthermore, the aim is to improve the conforming expansion of the TAVR stent to the vessel wall, especially for the self-expanding TAVR consisting of nitinol. One factor for the expansion is the size and shape of the TAVR stent cells, which vary between 9 and 15 cells in the circumferential direction for established TAVR devices. To quantify the impact of different cell sizes on the occurence of PVL, we performed numerical studies with different TAVR designs and investigated the PVL for each TAVR design. For this purpose, we developed three different TAVR designs with 9, 12 and 15 stent cells in the circumferential direction of the TAVR. These were deployed into a generic aortic root model with standardized calcification in the annulus region using finite element simulations. Afterwards, the PVL was calculated using numerical flow simulations. We found that the TAVR stent design with nine cells had the highest PVL rate (11.2mLs −1 ). In contrast, the TAVR stent design with 15 cells had the lowest PVL (4.8mLs −1 ). Our study thus showed a decisive impact of cell size on the sealing behavior of the TAVR stent and, accordingly, the PVL.