Finite element analysis of the mechanical performance of a two-layer polymer composite stent structure

Abstract

Bioresorbable stents (BRS) are an alternative to existing bare-metal stents (BMS) and drug-eluting stents (DES), aiming to reduce the short- and long-term complications in cardiovascular interventions. A combination of biodegradable polymers in a composite scaffold is a promising solution to improve BRS flexibility and strength, which is currently limited by the material properties of polymers. In this study, a mechanical performance of a composite BRS comprised of two layers with four different combinations of polylactic acid (PLA) and polycaprolactone (PCL) was examined with finite element analysis (FEA). Stent crimping and expansion with the balloon inside an atherosclerotic artery was simulated, and stent performance parameters were evaluated and compared between different composite layer configurations. The single-material PCL stent showed the highest recoil and failed to provide support to the artery, while the stiffer single-material PLA stent experienced significantly lower recoil, but also the highest dogboning during expansion, which could increase arterial wall damage. Nearly identical performance was observed for both mixed-material configurations, with recoil and foreshortening closer to single-material PLA stent and dogboning during expansion between both single-material stents. They showed the highest dogboning after balloon deflation due to a combination of permanent deformation at the ends of the stent and lower stiffness at the middle, which allowed for higher recoil at the middle but not at both ends of the stent. The combination of biodegradable polymers into composite BRS shows potential for targeted stent designs with performance tailored to specific needs.