Pathology of Mechanical Prosthetic Cardiac Valves

Abstract

Mechanical prosthetic valves were first implanted to replace diseased mitral and aortic valves in 1960. The initial models were developed according to the caged-ball design, with a moving poppet contained into a metallic frame. Subsequent models included caged disc, tilting disc, and bileaflet designs. These devices have represented a breakthrough for the treatment of patients with valvular heart disease, who previously were only amenable to closed chest palliative procedures. The outlook for such patients was dramatically improved, although some evident disadvantages of such devices became soon recognized. Recipients of mechanical prostheses were treated with chronic administration of anticoagulants to possibly avoid or reduce the major problems observed, like valve thrombosis, thromboembolic events, and hemorrhages. Such complications were mostly related to incorrect anticoagulant treatment, often complex to manage especially in old and poorly compliant patients. Some of the models also exhibited high transprosthetic gradients, especially in the small sizes. Continuous research was undertaken modifying the prosthetic design and materials to obtain devices with increased biocompatibility, higher resistance to wear and tear, superior hemodynamics, and lower thrombogenicity.

The current models of mechanical prostheses, predominantly used clinically, include the bileaflet design, with improved hemodynamic performance and a reported record of durability of over 20 years.