BVS stent optimisation based on a parametric model with a multistage validation process

Developing new polymer-based bioresorbable vascular scaffolds (BVS) requires a new structural geometry, as these polymer materials are characterised by substantially lower stiffness than metallic alloys. Sufficient radial strength of the stent is essential, as insufficient vessel wall support can lead to a significant recoil (reduction of the vessel lumen) and can cause dangerous complications. To assess the stress development and deformation of the stent, finite element analysis (FEA) was used. First, a complex FEA of the inflation and crimping processes of a bioresorbable coronary stent was performed. An optimisation procedure based on the simplified parametric FE model was subsequently performed to obtain the optimal geometric parameters of the analysed structure. The objective of the optimisation was to maximise the vessel diameter after the BVS implantation. The optimisation procedure was based on automatic model-generating scripts, numerical analyses and implementation of genetic algorithms. Finally, a comparison of the parametric and complex models results was performed, as well as a final validation at several stages (structural studies, computational fluid dynamics (CFD) simulations and in vivo testing). The validation confirmed that the presented optimisation methodology represents a valid and useful tool for the stent design process.