Spectral analysis of heart rate variability in patients with Machado-Joseph disease

Tachycardia is a clinical feature of Machado-Joseph disease (MJD), and it may be attributable to cardiac autonomic dysfunction. We investigated heart rate variability in MJD patients to reveal heart rate dysregulation in MJD.

Power spectral analysis of successive R-R intervals (300 beats) was performed in 10 genetically diagnosed MJD patients and 10 healthy control subjects to obtain frequency-domain measures, including high- (HF; 0.15-0.4 Hz) and low frequency power (LF; 0.04-0.15 Hz) and the ratio of LF to HF (LF/HF) of heart rate variability. In addition, the coefficient of R-R intervals (CV(R-R)) was calculated as a time-domain measure.

HF in the MJD patients (26.2+/-25.3 ms(2)) was lower than that in the controls (82.1+/-82.6 ms(2), p=0.004). LF was also lower in the MJD patients (70.6+/-69.4 ms(2)) than in the controls (106.9+/-81.3 ms(2); p=0.029). There was no significant difference in LF/HF or CV(R-R) between the groups.

HF, which is modulated by parasympathetic vagal activity, was low in our MJD patients. The reduced parasympathetic activity may be a cause of tachycardia in MJD patients.