A novel heart valve stent design: mechanical interaction with the aortic root.

Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients with high risk for open chest surgery. Vascular stents clinically used today for non-invasive aortic valve replacement tend, however, to impede the dimension changes of the compliant aortic root over the cardiac cycle. The purpose of the present work is to assess the influence of a novel heart valve stent, designed specifically to limit the traumatism in tissue, on the compliance of the aortic root. A theoretical approach is adopted to model the mechanical behaviour of the different stent parts and assess the compliance modification induced by the stent. The validity of the model is then tested experimentally. Both approaches show that the specific geometry of the stent makes it possible to keep the compliance of the aortic root close to the native root values.

Heart valve stent for percutaneous implantation: design optimization.

Percutaneous aortic valve implantation has become an alternative technique to surgical valve replacement in patients with high risk for surgery. This technique is at its beginning and stents used for valve prostheses remain standard vascular stents. These stents are, however, not designed to undergo heart valve stress. They do not match the aortic environment geometry, and induce exaggerated tissue traumatism. Reduced implant lifetime may therefore be expected. The purpose of this work is to evaluate in vitro the technical feasibility of noninvasive aortic valve replacement with a novel more specific stent. This stent is especially adapted to its implantation environment, with a design that matches the shape of the aortic root while respecting the valve function. To optimize the device's geometry, the influence of the design parameters on static and dynamic performances is studied in detail. For that purpose, the interaction between the stent and the aortic root is first studied theoretically, to highlight which parameters are relevant for further in vitro experiments. Static and dynamic regurgitation measurements are then performed to set the design parameters so as to optimize the behavior of the device implanted in a mock aortic root.