Type 1 fiber abnormalities in skeletal muscle of patients with hypertrophic and dilated cardiomyopathy: Evidence of subclinical myogenic myopathy

Alida L P Caforio, Bruno Rossi, Riccardo Risaliti, Gabriele Siciliano, Antonio Marchetti, Corrado Angelini, Filippo Crea, Mario Mariani, Alberto Muratorio

Research output: Contribution to journalArticlepeer-review

Abstract

Abnormalities of skeletal muscle have been described in patients with dilated and hypertrophic cardiomyopathy. Eleven patients with dilated and eight with hypertrophic cardiomyopathy without overt symptomatic skeletal myopathy underwent extensive neuromuscular studies. Quantitative electromyography showed abnormal reduction of motor unit potential duration, indicative of myogenic myopathy, in four patients (36%) with dilated and in three (37%) with hypertrophic cardiomyopathy. Values were 21% to 40% (mean 28%) lower than those in age-matched normal control subjects. The presence of normal nerve conduction velocities and of normal motor unit fiber density in all patients indicated lack of neurogenic abnormalities. Skeletal muscle biopsy was performed in five patients with dilated and in four with hypertrophic cardiomyopathy. In all nine patients light and electron microscopy showed central hyporeactive cores, selective atrophy and mitochondrial abnormalities of type 1 fibers but not of type 2 fibers. The degree of impairment of left ventricular function in patients with electromyographic abnormalities was similar to that of those without (percent fractional shortening at two-dimensional echocardiography 21 ± 9 versus 25 ± 10, ejection fraction at angiography 39 ± 13% versus 42 ± 13% and left ventricular end-diastolic pressure 21 ± 6 versus 21 ± 8 mm Hg) as well as symptom duration (9 ± 4 versus 12 ± 8 months). Thus, subclinical electromyographic alterations indicative of myogenic myopathy are frequent in patients with dilated and hypertrophic cardiomyopathy and are unrelated to the degree of impairment of left ventricular function. The concomitant histologic alterations, characterized by selective type 1 atrophy, are similar to those observed in congenital and idiopathic myopathies, but different from those described in secondary heart failure.

Original languageEnglish
Pages (from-to)1464-1473
Number of pages10
JournalJournal of the American College of Cardiology
Volume14
Issue number6
DOIs
Publication statusPublished - Nov 15 1989

ASJC Scopus subject areas

  • Nursing(all)

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