A 41 years old woman with polymyositis-dermatomyositis with cardiac involvement is presented. The patient evolved with congestive heart failure, the electrocardiogram showed a left anterior hemiblock, lack of progression of R waves from V1 to V4 and unspecific ST and T alterations. Echocardiogram and cardiac catheterization showed global ventricular disfunction and pulmonary hypertension. An endomyocardial biopsy performed at the apex of the right ventricle showed mononuclear inflammatory infiltration, myocardial fiber degeneration and fibrosis. Initially, the patient responded well to diuretic, vasodilator and steroid therapy. Posteriorly she developed an atrial flutter that required electrical cardioversion and later died suddenly during the course of an acute pneumonia.