Childhood polymyositis with cardiac conduction defects.

Pediatric polymyositis may be an entity distinct from dermatomyositis. Chronic polymyositis can occur in childhood and, as in adults, may be associated with arrhythmias. Microscopical involvement of the myocardium and pericardium in dermatomyositis is probably far more common than suspected on clinical grounds. Cardiac evaluation is suggested for all children with dermatomyositis or polymyositis, particularly prior to surgical procedures. Intracardiac electrographic recording techniques offer improved accuracy in determining the site of cardiac conduction defects, and may aid in planning for the use of antiarrhythmia medications or a pacemaker. In children with dermatomyositis or polymyositis known cardiac stimulants should be administered with care.