Skeletal muscle in idiopathic cardiomyopathy

Six patients in whom a diagnosis of idiopathic cardiomyopathy was made and who showed no evidence of complicating diseases known to affect skeletal muscle were selected for this report. The skeletal muscle was evaluated clinically, by electromyography (EMG) and by biopsy. Four patients showed selective atrophy of type II fibres and in 1 there was also evidence of neurogenic involvement. One patient had pronounced non-selective myopathy with internalization of capillaries in the muscle fibres. One other had hypotrophy of type I fibres and also clinical evidence of muscle disease. No such abnormalities were found in patients with other forms of heart disease. It is suggested that idiopathic cardiomyopathy is sometimes a more generalized disorder and that the genetic or environmental etiological factors responsible for some cardiomyopathies may also involve skeletal muscle.