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Increased temporal dispersion of myocardial repolarization in myotonic dystrophy type 1: beyond the cardiac

Damiano Magrì1, Gianfranco Piccirillo, Elisabetta Bucci

  • 1Cardiology Department, S. Andrea Hospital, "Sapienza" University of Rome, Rome, Italy. damiano.magri@libero.it

International Journal of Cardiology
|November 30, 2010
PubMed

Insights

Myotonic dystrophy type 1 (DM1) patients show increased QT variability index (QTVI), indicating broader heart involvement beyond conduction issues. This QTVI marker may help predict DM1

Area of Science:

  • Cardiology
  • Genetics
  • Autonomic Nervous System Function

Background:

  • Sudden cardiac death in myotonic dystrophy type 1 (DM1) is primarily linked to bradyarrhythmias from cardiac conduction abnormalities.
  • Ventricular tachyarrhythmias are a significant clinical concern in DM1 management.
  • Autonomic nervous system (ANS) activity and myocardial repolarization lability require further investigation in DM1.

Purpose of the Study:

  • To assess ANS activity by comparing the QT variability index (QTVI) between DM1 patients and healthy controls.
  • To investigate differences in QTVI within DM1 patients based on the presence of first-degree atrioventricular block (1st AVB) and cytosine-thymine-guanine (CTG) repeat expansion size.

Main Methods:

  • Sixty-two DM1 patients and 20 healthy subjects underwent comprehensive neurological and cardiological evaluations.
  • Standard ECG, echocardiography, and 24-hour Holter monitoring were performed.
  • A 5-minute ECG recording was used to assess heart rate variability (HRV) power spectral components and QTVI.

Main Results:

  • DM1 patients exhibited significantly lower power spectral data (total, low frequency, high frequency) and higher QTVI compared to controls (p<.0001).
  • DM1 subgroups with 1st AVB (p=.009) and CTG repeat expansion >500 (p=.014) showed higher QTVI values.
  • Multivariable analysis revealed QTVI and age were independently associated with PR interval and CTG repeat length.

Conclusions:

  • Elevated QTVI in DM1 patients suggests significant cardiac involvement extending beyond known conduction system abnormalities.
  • QTVI may serve as a valuable marker for assessing cardiac repolarization lability in DM1.
  • Larger prospective studies are needed to determine if QTVI can predict the clinical course of DM1.
Abstract

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