We report herein the unusual case of a 74-year-old man with acute heart failure in whom mitral regurgitation occurring secondary to papillary muscle rupture was found by echocardiography. There was no electrocardiographic evidence of myocardial infarction and a mitral valve replacement was successfully performed. Histologically the posteromedial muscle showed perivascular fibrosis without necrosis. The patient had an uneventful recovery and postoperative coronary angiography showed normal vasculature. This is a rare case of spontaneous papillary muscle rupture occurring secondary to chronic ischemia.