Mechanical properties of coronary stents determined by using finite element analysis

The mechanical function of a stent deployed in a damaged artery is to provi de a metallic tubular mesh structure. The purpose of this study was to dete rmine the exact mechanical characteristics of stents. In order to achieve t his, we have used finite-element analysis to model two different type of st ents: tubular stents (TS) and coil stents (CS). The two stents chosen for t his modeling present the most extreme mechanical characteristics of the res pective types. Seven mechanical properties were studied by mathematical mod eling with determination of: (1) stent deployment pressure, (2) the intrins ic elastic recoil of the material used, (3) the resistance of the stent to external compressive forces, (4) the stent foreshortening, (5) the stent co verage area, (6) the stent flexibility, and (7) the stress maps. The pressu re required for deployment of CS was significantly lower than that required for TS, over 2.8 times greater pressure was required for the tubular model . The elastic recoil of TS is higher than CS (5.4% and 2.6%, respectively). TS could be deformed by 10% at compressive pressures of between 0.7 and 1. 3 atm whereas CS was only deformed at 0.2 and 0.7 arm. The degree of shorte ning observed increases with deployment diameter for TS. CS lengthen during deployment. The metal coverage area is two times greater for TS than for C S. The ratio between the stiffness of TS and that of CS varies from 2060 to 2858 depending on the direction in which the force is applied. TS are very rigid and CS are significantly more flexible. Stress mapping shows stress to be localized at link nodes. This series of finite-element analyses illus trates and quantifies the main mechanical characteristics of two different commonly used stents. In interventional cardiology, we need to understand t heir mechanisms of implantation and action. (C) 2001 Elsevier Science Ltd. All rights reserved.