Malfunction in a St. Jude medical mitral valve prosthesis: a clinical diagnostic dilemma.

Thrombosis of one leaflet of a St. Jude medical prosthetic mitral valve in a 49-year-old man resulted in prosthetic malfunction causing cardiac failure. Clinical and echocardiographic assessment did not adequately distinguish between abnormal valve function and left ventricular dysfunction as the responsible lesion. Hemodynamic study revealed a gradient across the mitral valve and poor left ventricular function. At operation it was found that thrombus had caused one of the leaflets to stick in an almost open position. This malfunction was attributed to lack of adequate anticoagulation and to the impingement of a piece of papillary muscle on the prosthesis. A definite echocardiographic pattern for malfunction of the St. Jude valve has not been established. However, it is clear that loudness of prosthetic valve sounds cannot be used as a guide to normal function in a bileaflet valve.