Left atrial thrombus despite anticoagulant therapy in a patient with a mitral valve prosthesis

Massive left atrial thrombus (MLAT) developed in a patient with porcine heterograft mitral valve, left atrial dilatation, and atrial fibrillation, despite anticoagulant therapy with warfarin sodium (Coumadin). The thrombus obstructed the mitral valve orifice, leading to acute myocardial infarction, pulmonary edema, and death due to cardiogenic shock.