Ambulatory ECG and analysis of heart rate variability in Parkinson's disease

Objectives-Cardiovascular reflex tests have shown both sympathetic and para sympathetic failure in Parkinson's disease. These tests, however, describe the autonomic responses during a restricted time period and have great indi vidual variability, providing a limited view of the autonomic cardiac contr ol mechanisms. Thus, they do not reflect tonic autonomic regulation. The ai m was to examine tonic autonomic cardiovascular regulation in untreated pat ients with Parkinson's disease. Methods-24 Hour ambulatory ECG was recorded in 54 untreated patients with P arkinson's disease and 47 age matched healthy subjects. In addition to the traditional spectral (very low frequency, VLF; low frequency, LF; high freq uency, HF) and non-spectral components of heart rate variability, instantan eous beat to beat variability (SD1) and long term continuous variability (S D2) derived from Poincare plots, and the slope of the power law relation we re analysed. Results-All spectral components (p<0.01) and the slope of the power-law rel ation (p<0.01) were lower in the patients with Parkinson's disease than in the control subjects. The Unified Parkinson's disease rating scale total an d motor scores had a negative correlation with VLF and LF power spectrum va lues and the power law relation slopes. Patients with mild hypokinesia had higher HF values than patients with more severe hypokinesia. Tremor and rig idity were not associated with the HR variability parameters. Conclusions-Parkinson's disease causes dysfunction of the diurnal autonomic cardiovascular regulation as demonstrated by the spectral measures of hear t rate variability and the slope of the power law relation. This dysfunctio n seems to be more profound in patients with more severe Parkinson's diseas e.