ABSTRACT
At present, no ideal artificial heart valve is available.1-3 In the aortic position, bioprostheses are the valve of choice in patients older than 70 years. They are advantageous in terms of haemodynamics, thrombogenicity, risk of bleeding and need for anticoagulation.4-6 However, limited durability is the greatest problem of bioprostheses.79 Valve failure is mainly due to structural degeneration from tissue and cell calcification, caused by multiple factors.10-13
Bioprostheses are xenografts from porcine valves or from bovine pericardium. To avoid any immunological reaction and to achieve an optimally stable material, the xenograft tissue has to be denaturated by cross-linking before implantation.9,13 Glutaraldehyde is the standard fixative, with no other process in view.9,14 Nevertheless, it became apparent that glutaraldehyde itself is in part responsible for calcification of the xenograft tissue and that the residual cells are the main target for calcification.15-17
Current research to improve valve performance and durability has developed in two directions: change of the valve design from conventional to stentless bioprostheses, and the development of additional anticalcificant treatments.12,18 The stentless design leads to a more flexible device that is much closer than the conventional stented bioprostheses to the native aortic valve. The stentless aortic bioprostheses consist of valve leaflets and aortic root tissue.
