Abstract 17693: Fracture Potentials and Dynamic Flexibility of Peripheral Stents: Insights into Clinical Practice From Durability Tests Simulating Multi-loading Environments of Superficial Femoral and Popliteal Arteries
Introduction: Stent fracture is identified as one of the primal causes of restenosis in superficial femoral and popliteal artery. However, differences in fracture potentials due to stent platforms and other indicators for restenosis in the lesions without stent fracture have not been well understood yet. We aimed to assess fracture potentials and dynamic flexibility of peripheral stents using two types of multi-loading durability testers.
Methods: Based on the referenced data of SFA deformations in spine and fetal positions, we developed a multi-loading durability tester exerting cyclic torsion of 2.8 degrees/cm and shortening of 12.7% simultaneously to the elastic SFA models incorporating stents. Because arteries are stretched in the body, the SFA models were extended for 10% in the shortened phase. Mechanical stiffness of the SFA models was adjusted to that of human femoral artery. We defined dynamic longitudinal flexibility of stent as (differences in stent length between extended and shortened phases / length in extended phase) / vessel shortening percentage. PA dominantly receives bending load. Therefore, a cyclic bend-load tester was developed. Stents were deployed in the elastic PA models and cyclic bending from 150 degrees to 60 degrees was exerted. Five types of self-expanding nitinol stents (Misago, SMART, LIFE, Absolute, Zilver) were compared. Five samples with diameter and length of 6mm and 80mm for each stent were tested for 10 million cycles, respectively.
Results: In the durability test exerting cyclic torsion and shortening, stent fracture were observed for Misago, Zilver, and LIFE in 1/5, 1/5, and 5/5 cases. SMART and Absolute had no fracture. Stent edge of LIFE was separated and came off into lumen in 2/5 cases. Moreover, fractured edge of LIFE made a perforation in the SFA model in 1/5 cases. Dynamic longitudinal flexibility was highest in Misago and lowest in SMART. In the bend-load durability tests, Misago had no fracture. Stent fractures were observed for SMART, LIFE, Absolute, and Zilver in 4/5, 2/5, 3/5, and 2/5 cases.
Conclusions: Incidences of stent fracture were different among five stents in SFA and PA simulated multi-loading tests. To the best of our knowledge, this is the first report to present stent dynamic longitudinal flexibility.
- © 2013 by American Heart Association, Inc.