Design of new trileaflet heart valves: computational mechanics study

In this study differently shaped trileaflet valves have been designed and structurally examined by FEM-analysis. Aim of this preliminary work is to choose the valve geometry for the prototyping of a valve in a polyurethane polymer. Mechanical fatigue properties of polyurethane polymers do not provide a good valve durability. We developed new design features, a semi-open configuration at rest for the leaflets and a wireframe-like expansible stent, in order to improve valve durability by means of better stress distribution. For a comparative evaluation three different leaflet geometries and two stents have been modelled. The leaflet geometries at zero stress condition are: spherical surface (valve in semiopen configuration); spherical surface (valve in close position); interpolation surface between two arcs (valve in semiopen position). The stents are a classic rigid ring stent and an expansible one. Results indicate that the best valve performance is achieved when the expansible stent is coupled with the non-spherical surface leaflets.