The presence of mechanical or bioprosthetic valves has traditionally excluded patients from mechanical circulatory support. However, several centers have now developed algorithms for the surgical management of native or prosthetic valve disease in patients requiring left ventricular assist device insertion. We report adverse events associated with bioprosthetic valves in the mitral and tricuspid positions in 2 patients who received long-term mechanical support. We recommend anticoagulation for all patients with prosthetic valves in the mitral or tricuspid position to avoid thromboembolism, inflow conduit occlusion, or valvular incompetence.