Small cardiac lesions. Fibrosis of papillary muscles and focal cardiac myocytolysis.

Three types of small cardiac lesions were described and illustrated: (1) focal type of papillary muscle fibrosis, evidently a healed infarct of the papillary muscle present in 13% of autopsies, is a histologically characteristic lesion associated with coronary artery disease and healed myocardial infarction, (2) diffuse type of papillary muscle fibrosis, probably an aging change present in almost half of the autopsies, is associated with sclerosis of the arteries in the papillary muscle, is identifiable histologically, and apparently is not associated with any cardiac abnormality, and (3) focal cardiac myocytolysis, a unique histologic lesion, usually multifocal without predilection for any area of the heart, is associated with ischemic heard disease, death due to cancer complicated by nonbacterial thrombotic endocarditis and microthrombi in small cardiac arteries as well as with other diseases. Differentiation of the 2 types of papillary muscle fibrosis is important in the study of papillary muscle and mitral valve dysfunction. Focal cardiac myocytolysis may contribute to the fatal extension of myocardial infarcts.