• spinocerebellar ataxias;
  • spectrum analysis;
  • trinucleotide repeats

Objective –  To detect cardiac autonomic dysfunction, using analysis of heart rate variability in genetically defined spinocerebellar ataxias (SCA).

Materials and methods –  Consecutive RR intervals were analyzed for time- and frequency- domain parameters in 22 genotypically proven SCA patients (SCA1 = 11, SCA2 = 6 and SCA3 = 5) and compared with that of age- and gender- matched controls.

Results –  Reduction in the standard deviation of RR interval (RR_SD) was seen in 72.7% of SCA patients. There was a reduction in both the parasympathetic and sympathetic parameters in SCA without any change in the ratio of low- to high- frequency power. In SCA1, there was a significant negative correlation between RR_SD and duration of illness but not with the CAG repeat lengths of the abnormal allele. Small sample size of SCA2 and SCA3 precluded similar comparison.

Conclusions –  Cardiac autonomic dysfunction, predominantly parasympathetic, was seen in SCA, and the severity correlated with the duration of illness in SCA1.