Balloon folding affects the symmetry of stent deployment: experimental and computational evidence

The level of restenosis following coronary artery stenting may be related to the deployed stent geometry. This study investigated the influence of two balloon folding patterns ('C' and 'S' shaped) on stent deployment. In vitro stent expansion showed 'S' shape folding produced more uniform expansion than 'C' shape folding. A numerical contact model (NCM) was developed to study the detail of load transfer between balloon and stent. Finite element analysis of the Palmaz-Schatz 204C stent provided a composite non-linear material model for the NCM. Agreement between the predicted final stent geometry and experimental results was strongly dependent on the frictional coefficient between the stent and balloon. We conclude that non-uniform contact may contribute to the asymmetry of deployed stents reported clinically.