FATIGUE LIFE PREDICTION FOR A CORONARY STENT IN A REALISTIC STENOSIS MODEL
Xinyang Cui, Zhaoyong Gu, Aike Qiao
College of Life Science and Bioengineering, Beijing University of Technology, China
Background The fatigue life of stents is closely related to its biomechanical environment. In this paper, a realistic stenosis model was built from a biomechanics perspective with clinical data. Based on this model, the mechanical performance of coronary stent was analyzed after it was implanted and working in the vessels, and the fatigue life of stents was predicted.
Methods Coronary artery stenosis model was built by using Mimics based on CT angiography (CTA) data. Finite element method (FEM) was used to simulate the stent expansion process after it was implanted into the realistic coronary stenosis model. Based on the mechanical analysis, the influence of cyclic loading effect on the fatigue life of the stents was studied. Stents fatigue rupture was determined by Goodman diagram, and the fatigue performance was analyzed based on parameters including number of fatigue cycles, fatigue life, fatigue safety factor (FSF), and cumulative fatigue damage rate, etc.
Results The maximum stresses of the stent, plaque, and the vessel wall were 413.8 MPa, 6.06 MPa, and 3.39 MPa respectively, and the maximum stress was always located at the bending area of the stent crowns. In the fatigue performance analysis, the stent would not fail for fatigue rupture calculated by Goodman diagram. The predicted number of fatigue cycles was 5.32*108 which was equivalent to fatigue life of 14 years, FSF was 2.8, and the maximum cumulative fatigue damage rate was 71.5%.
Conclusion The mechanical parameters (stress/ strain) were associated with the realistic coronary stenosis model. It is feasible to use a realistic model to calculate the accurate stress/strain of a coronary stent, to predict the dangerous point and evaluate the accurate fatigue performance parameters. This study provided an approach to select and position a stent in order to minimize the risk of fatigue fracture.