Voluntary Muscle Involvement in Hypertrophic Cardiomyopathy

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Abstract
Hypertrophic cardiomyopathy was generally considered a primary disease of cardiac muscle, although several clinical observations suggest that the pathologic process might be more diffuse. Electromyography [EMG] and voluntary muscle biopsies were done on 11 patients with hypertrophic cardiomyopathy. In 10 of 10 patients EMG showed reductions in mean potential amplitude and duration, with an increased incidence of short-duration polyphasic deflections (findings traditionally accepted as indicative of a myopathic process). EM and light microscope studies of the biopsy material showed abnormalities in 8 of 11 patients: 4 had central core or target fibers, or both, and 2 of these, plus 4 others, had subsarcolemmal mitochondrial proliferation with or without abnormal ultrastructure. Hypertrophic cardiomyopathy was only 1 aspect of a larger disease spectrum, with abnormalities in both voluntary and cardiac muscle.