Heart rate variability declines with increasing age and CTG repeat length in patients with myotonic dystrophy type 1.
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.
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*
D005819:Genetic Markers; D011740:Pyrimidine Dimers; D006147:Guanine