Finite element analysis of stent deployment: understanding stent fracture in percutaneous pulmonary valve implantation.

OBJECTIVES To analyze factors responsible for stent fracture in percutaneous pulmonary valve implantation (PPVI) by finite element method. BACKGROUND PPVI is an interventional catheter-based technique for treating significant pulmonary valve disease. Stent fracture is a recognized complication. METHODS Three different stent models were created: (1) platinum-10% iridium alloy stent - resembles the first-generation PPVI device; (2) same geometry, but with the addition of gold over the strut intersections - models the current stent; (3) same design as 1, but made of thinner wire. For Model 3, a stent-in-stent solution was applied. Numerical analyses of the deployment of these devices were performed to understand the stress distribution and hence stent fracture potential. RESULTS Model 1: Highest stresses occurred at the strut intersections, suggesting that this location may be at highest risk of fracture. This concurs with the in vivo stent fracture data. Model 2: Numerical analyses indicate that the stresses are lower at the strut intersections, but redistributed to the end of the gold reinforcements. This suggests that fractures in this device may occur just distal to the gold. This is indeed the clinical experience. Model 3 was weakest at bolstering the implantation site; however, when two stents were coupled (stent-in-stent technique), better strength and lower stresses were seen compared with Model 1 alone. CONCLUSIONS Using finite element analysis of known stents, we were able to accurately predict stent fractures in the clinical situation. Furthermore, we have demonstrated that a stent-in-stent technique results in better device performance, which suggests a novel clinical strategy.