Myocardial involvement in polymyositis.

Polymyositis (PM) is a myopathic syndrome that results in pathology believed to be primarily confined to skeletal muscle. Several recent reports, based on quantitative determinations of total serum creatine kinase (CK) and MB isoenzyme activity, accepted serologic correlates of active myocardial injury, suggest that cardiac involvement in PM may occur more frequently than has been clinically appreciated. We retrospectively studied 12 patients with PM; 83% (10) were found to have substantial elevations in CK-MB activity, often to levels exceeding those seen with myocardial infarctions, thus confirming a high probability of myocardial involvement in PM. Failure to detect this clinically may be indicative of the insensitivity of current technology. A review of the literature substantiates the importance of appreciating the spectrum, frequency and functional consequences (i.e., conduction disturbances, cardiomyopathy) of myocardial involvement in PM.