Based on the experience of the Pathology and Surgery Branches, NHLBI, a description is presented of the morphology of unimplanted cardiac valvular bioprostheses and of the changes that develop in these devices after implantation as substitute cardiac valves. Emphasis is placed on the problems of valvular tars and calcific deposits, the two most important complications the develop in implanted cardiac valvular bioprostheses.
