Study of Bending Stiffness of Transcatheter Aortic Valve Stents

Transcatheter aortic valve implantation (TAVI) is an innovative minimally invasive procedure designed to replace a damaged or narrowed aortic valve. One of important factor is a device selection, which means variety of stent frame types. Bending stiffness of TAVI stent frame provides an ability to withstand external deformation, when it is implanted in the aortic annulus. Patient-specific manufacturing can solve a problem of patient-device sizing and compatibility. For customized manufacturing it is necessary to find a relation between TAVI implant design and strength to avoid post-operative complications. Nevertheless, studies of relations between structure of TAVI stents and their mechanical performance are rare. Thus, eight stent geometries (a–h) including commercial ones (a, b) and own-developed (c–h) were manufactured by filament fused fabrication. Basing on mechanical tests, features of TAVI stent frames, numerical simulations of stent deployment and bending were carried out. Three-point bending was also performed on manufactured stents. The least average value of bending stiffness was shown by models a, e, f, g (0.92–1.09 kN⋅mm2), while the greatest average value was obtained for c model (5.05 kN⋅mm2). Additionally, correlation analysis was performed. To reach bending stiffness of 6 kN⸱mm2, waist position should be 22.4 mm, parameters vertical and horizontal should be 3.4 and 8.7, respectively. The proposed study can help to choose proper TAVI stent frame design basing on demanding stiffness of aorta to provide accurate short- and long-term performance of the prothesis.