Heart rate variability declines with increasing age and CTG repeat length in patients with myotonic dystrophy type 1

Bradley A. Hardin, Miriam R. Lowe, Deepak Bhakta, William J. Groh

Research output: Contribution to journalArticle

26 Scopus citations


Background: Cardiac myopathy manifesting as arrhythmias is common in the neurological disease, myotonic dystrophy type 1 (DM1). The purpose of the present study was to evaluate heart rate variability (HRV) in patients with DM1. Methods: In a multicenter study, history, ECG, and genetic testing were performed in DM1 patients. Results: In 289 patients in whom the diagnosis of DM1 was confirmed by a prolonged cvtosine-thymine-guanine (CTG) repeat length the most common ambulatory ECG abnormality was frequent ventricular ectopy (16.3%). The 24-hour time domain parameters of SDNN (SD of the NN interval) and SDANN (SD of the mean NN, 5-minute interval) declined as age and CTG repeat length increased (SDNN: -8.5 ms per decade, 95% confidence intervals [CI] -12.9, -4.2, -8.7 ms per 500 CTG repeats, CI -15.7, -1.8, r = 0.24, P < 0.001; SDANN: -8.1 ms per decade, CI -12.4, -3.8, -8.8 ms per 500 CTG repeats, CI -15.7, -1.9, r = 0.23, P < 0.001). Short-term frequency domain parameters declined with age only (total power: -658 ms2 per decade, CI: -984, -331, r = 0.23, P < 0.001; low frequency (LF) power -287 ms2 per decade, CI: -397, -178, r = 0.30, P < 0.001; high frequency (HF) power: -267 ms2 per decade, CI: -386, -144, r = 0.25, P < 0.001). The LF/HF ratio increased as the patient aged (0.5 per decade, CI: 0.1, 0.9, r = 0.13, P = 0.03). Conclusions: In DM1 patients a decline in HRV is observed as the patient ages and CTG repeat length increases.

Original languageEnglish (US)
Pages (from-to)227-232
Number of pages6
JournalAnnals of Noninvasive Electrocardiology
Issue number3
StatePublished - Jul 1 2003



  • Arrhythmias
  • Genetics
  • Heart rate variability
  • Myotonic dystrophy

ASJC Scopus subject areas

  • Cardiology and Cardiovascular Medicine

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