Evaluation of Torsional Fatigue Behavior of Coronary Stents

Abstract

The coronary stent treatment, that is one kind of Percutaneous Coronary Intervention (PCI), is a general treatment to the angina pectoris. However, the stent has some problems such as a fracture after implantation and restenosis. One reason of the stent fracture is due to the cyclic load by the heart pulse after implantation. To avoid the stent fracture and restenosis, understanding the mechanical behavior of stents and an appropriate selection of stents are important. Since stent products have quite different design and material, standardizing the quantitative assessment of mechanical property of different stent products is required. In this study, fatigue tests were performed to compare mechanical properties (tensile fatigue and torsional fatigue properties) of four types of stent. Additionally, finite element analysis (FEA) was performed to analyze fatigue behavior of stent in tensile and torsional loading direction. Fatigue Safety Factor (FSF) was used to evaluate fatigue property in the analysis. The results had different tendency of fatigue life between tensile and torsional fatigue tests. The fracture part in fatigue test was consistent with the stress concentration zone analyzed by FEA. Fatigue strength of four types of stents could be estimated by FSF. It is concluded that the fatigue behavior can be evaluated using FEA.