Authors : K. Kalaiselvam, K. Rajkumar, G. Joseph and M. Thanikachalam
Abstract: Aim of the project is to design a TAVR stent for percutaneous treatment of aortic stenosis, without the need for open heart surgery. Nitinol stent with two interlocked 26 mm diameter zigzag rings was modeled and analyzed in ANSYS 12.0. The various design parameters included the number (n = 10-18) and height (h = 3-6 mm) of struts and the thickness (t = 0.25-0.5 mm) and stiffness (e = 26364M-50000 MPa) of the ring. The FEA was done by altering design parameters to arrive at an optimal crimp profile and radial force for a stent deployed in a 21 mm annulus. Subsequently, buckling and fatigue analysis were performed. Finally, a nitinol stent was prototyped and compression tests were performed to assess the radial force. Among the various parameters, increasing the ring thickness (0.25-0.5 mm) resulted in maximum increase in hoop forces (3.84-10.56 N). At the same time, the minimum crimp profile increased marginally (5.74-6.66 mm). There were minimal changes to hoop forces with changes with number of struts (3.84-4.24 N) or the stiffness of the wire (3.84-4.16). The final optimized design had a crimp profile of 3 mm and a radial force of 16N which was confirmed to be 14 N by compression test. The buckling load was 2.7 N while the fatigue analysis showed durability at 400 million life cycles. Based on FEA, a TAVR stent of acceptable profile, radial force and durability was designed. Further bench testing will validate the design.
K. Kalaiselvam, K. Rajkumar, G. Joseph and M. Thanikachalam, 2018. Design and Development of Transcatheter Aortic Valve Repair (TAVR) Nitinol Stent. Journal of Engineering and Applied Sciences, 13: 5605-5611.