Currently, mechanical bileaflet valves have the best hemodynamic characteristics and clot resistance. Bioprosthetic valves include porcine and bovine xenografts. Advantages of bioprosthetic valves include their durability and low incidence of thromboembolism. Complications associated with bioprosthetic heart valves include hemorrhage and stiffening of the leaflets. Although bioprosthetic heart valves have proven to be the most successful however, their is still concern about their long term performance in vivo.
Most valves fail due to calcification of the moving components.
Medical researchers in academia and industry are currently working to understand the failure mechanisms of prosthetic heart valves so they can develop optimal designs. This is an excellent site pertaining to mechanical, bioprosthetic, and pericardial heart valves. In the section on prosthetic heart valves, there is a description of valves made from human tissue and animal tissue. The site gives some general information about heart valves and how they are damaged. The application of mechanical and tissue valves is discussed as well as the steps involved in a double valve replacement surgery.