Background: To investigate the clinical features of cardiac involvement in polymyositis (PM) or dermatomyositis (DM). Hypothesis: More attention will be focused on the heart in PM/DM as we would have wished, which contribute to improve the prognosis. Methods: All articles published in English were retrieved by searching MEDLINE via PubMed (19752011). After selecting eligible articles according to the predefined inclusion and exclusion criteria, a systemic review was carried out. Results: A total of 26 articles were included in this study, which included 1530 patients. The incidence of cardiac involvement was 9% to 72%. Heart failure was the most frequent (32% to 77%) clinical symptom. Among the abnormal electrocardiogram and ultrasonic cardiogram, the incidence of conduction abnormalities, left ventricular diastolic dysfunction, and hyperkinetic left ventricular contraction were 25% to 38.5%, 42%, and 6% to 12%, respectively. The pathologic findings revealed myocardial inflammation, degenerative changes and necrosis similar to that in skeletal muscles. Cardiac manifestations of some patients improved after glucocorticoid and immunosuppressant treatment. Thirty-seven patients (46.3%) died as a direct result of heart disease. Conclusions: Heart abnormalities are frequent in patients with PM/DM, most of which were subclinical. The efficacy of glucocorticoids and immunosuppressants is uncertain. Cardiac involvement is a common cause of death.