title: Heart rate variability declines with increasing age and CTG repeat length in patients with myotonic dystrophy type 1.
abstract: 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 cytosine-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.
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001145:Arrhythmias, Cardiac / Q000453:epidemiology / Q000235:genetics / Q000503:physiopathology; D001341:Autonomic Nervous System / Q000502:physiology; D015716:Electrocardiography, Ambulatory; D005260:Female; D005500:Follow-Up Studies; D005819:Genetic Markers / Q000235:genetics; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006147:Guanine / Q000502:physiology*; D006329:Heart Conduction System / Q000473:pathology / Q000503:physiopathology; D006339:Heart Rate / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D009223:Myotonic Dystrophy / Q000453:epidemiology / Q000235:genetics* / Q000503:physiopathology; D015588:Observer Variation; D011740:Pyrimidine Dimers / Q000235:genetics*; D012042:Registries; D013223:Statistics as Topic; D019680:Trinucleotide Repeat Expansion / Q000235:genetics; D018911:Trinucleotide Repeats / Q000235:genetics*
chemical_list: D005819:Genetic Markers; D011740:Pyrimidine Dimers; D006147:Guanine