Prosthetic heart valves.

The first prosthetic valve was implanted by Hufnagel in 1952 in a patient with aortic insufficiency. Since then, prosthetic valves have evolved into various mechanical and bioprosthetic shapes and sizes. Despite the excitement surrounding the current development of prosthetic heart valves, surgically implanted valves remain the mainstay of current practice, and this article discusses the hemodynamic issues associated with the more commonly placed valves.