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Electromyographic evidence of subclinical myopathy in hypertrophic cardiomyopathy

N Karandreas1, P Stathis, A Anastasakis

  • 1EMG Laboratory, Department of Neurology, Aeginition Hospital, University of Athens, Vas. Sofias 72-74, 11528 Athens, Greece. nekaran@hotmail.com

Muscle & Nerve
|December 5, 2000
PubMed

Insights

Electromyography (EMG) can detect skeletal muscle involvement in hypertrophic cardiomyopathy (HCM). Quantitative EMG (QEMG) shows myopathic findings in 15% of HCM patients, suggesting distinct genetic subtypes.

Area of Science:

  • Cardiology
  • Neurology
  • Genetics

Background:

  • Hypertrophic cardiomyopathy (HCM) is a genetic heart condition caused by mutations in contractile protein genes.
  • Some HCM-associated gene mutations, particularly in beta-myosin, involve skeletal muscle and may influence prognosis.
  • The potential for skeletal muscle involvement in HCM necessitates methods for its detection.

Purpose of the Study:

  • To evaluate the utility of electromyography (EMG) and quantitative electromyography (QEMG) in identifying skeletal muscle abnormalities in patients with HCM.
  • To determine the prevalence of myopathic findings in an HCM cohort using EMG techniques.
  • To explore whether EMG findings correlate with different genetic substrates in HCM.

Main Methods:

  • A cohort of 46 patients with HCM underwent conventional EMG and QEMG.
  • QEMG included motor unit potential (MUP) analysis, turns/amplitude (TAA) analysis, and power spectrum analysis.
  • Receiver operating characteristic (ROC) analysis was used to assess the diagnostic accuracy of QEMG parameters.

Main Results:

  • Conventional EMG revealed myopathic findings in 28% (13 out of 46) of HCM patients.
  • QEMG analysis, using a discriminant function, correctly identified normal controls and myopathic controls.
  • QEMG indicated a 15% prevalence of myopathy (7 patients) within the HCM group, with MUP duration being the most sensitive indicator.
  • These findings suggest that skeletal muscle involvement is present in a subset of HCM patients.

Conclusions:

  • Electromyography, particularly QEMG, is a valuable tool for detecting skeletal muscle involvement in hypertrophic cardiomyopathy.
  • The presence of myopathic findings in HCM patients may signify distinct subpopulations with different genetic underpinnings.
  • Further research into the genetic basis of these HCM subpopulations identified by EMG is warranted.

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