The first step to understanding valve failure: an overview of pathology.

The most frequent valve-related complications are thromboembolic problems (including anticoagulant-related hemorrhage), infective endocarditis, paravalvular leak, intrinsic degradative dysfunction, and extrinsic interference with function, including tissue overgrowth. Tissue overgrowth, endocarditis, and paravalvular leak are largely prosthesis-independent. Thrombosis, the major cause of mechanical valve dysfunction, is infrequent with bioprostheses; in contrast, the overwhelming cause of bioprosthetic valve failure is primary tissue degeneration.