Stent Fracture Prediction in Percutaneous Pulmonary Valve Implantation: A Patient-Specific Finite Element Analysis

The major limitation of the current percutaneous pulmonary valve implantation (PPVI) device is stent fracture. In this study, patient-specific analyses were developed to reproduce the realistic loading conditions experienced by the device in-situ, in order to predict fractures. Biplane fluoroscopy images of 5 patients who underwent PPVI and experienced fracture were used to reconstruct the 3D in-situ device geometry at 3 different times of the procedure and cardiac cycle (end of balloon inflation, early systole and diastole). From the superimposition of these 3 stent configurations, the displacements of the strut junctions of the stent were measured. Asymmetries were calculated in all 3 orthogonal directions for every instant reproduced. A finite element (FE) model of the stent in the initial crimped configuration was created. The previously measured displacements were applied to 2 nodes of the FE stent model in the corresponding strut junction, and the stent deployment history was reproduced for each patient. A fatigue study was performed using the Goodman method and the Sines criterion. Both these methods were able to predict stent fracture in every analysed case. Furthermore, the zones with the highest risk of fracture predicted by the simulations included the areas where fractures were actually detected from X-rays images.