Computational structural analysis as a tool to develop valved stent applications and technology

Percutaneous pulmonary valve implantation is an innovative technique for the treatment of right ventricular outflow tract dysfunction. This procedure is available for a limited group of patients with very specific anatomy. Finite element analyses, together with computer aided design technology and imaging processing software, were used in this study to broaden the range of patients who might benefit from this procedure. Three-dimensional reconstruction of patient right ventricular outflow tracts, derived from magnetic resonance data, was performed by image elaboration to assess the implantation site anatomy. A morphological classification was created to analyse the criteria for percutaneous pulmonary valve implantation subject selection. Physical models of the right ventricular outflow tracts from patients with borderline anatomy for percutaneous procedure were built using the rapid prototyping technique. These models provided a complete appreciation of the three-dimensional anatomy and aided patient selection for percutaneous pulmonary valve implantation more accurately than magnetic resonance images. Moreover, they enabled trial implantation of devices to test their deployment and anchoring force into the right ventricular outflow tract. Computer aided design models of different stents were created: the early generation device employed for percutaneous pulmonary valve implantation, the device currently in use and a new possible stent design made of nitinol. Virtual simulation of the inflation of these devices was performed using the finite element method to study the mechanical behaviour and risk of fracture in these devices. The stress and strain distributions were evaluated to numerically compare the performance of the first generation device, with the current stent. A finite element model of a selected patient right ventricular outflow tract was created to computationally investigate the stent/implantation site interaction. Finite element analyses aided the optimisation of a nitinol ring to be employed in the next generation stent