Objectives-Cardiovascular reflex tests have shown both sympathetic and parasympathetic failure in Parkinson's disease. These tests, however, describe the autonomic responses during a restricted time period and have great individual variability, providing a limited view of the autonomic cardiac control mechanisms. Thus, they do not reflect tonic autonomic regulation. The aim was to examine tonic autonomic cardiovascular regulation in untreated patients with Parkinson's disease. Methods-24 Hour ambulatory ECG was recorded in 54 untreated patients with Parkinson's disease and 47 age matched healthy subjects. In addition to the traditional spectral (very low frequency, VLF; low frequency, LF; high frequency, HF) and non-spectral components of heart rate variability, instantaneous beat to beat variability (SD1) and long term continuous variability (SD2) derived from Poincaré plots, and the slope of the power law relation were analysed. Results-All spectral components (p<0.01) and the slope of the power-law relation (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 and motor scores had a negative correlation with VLF and LF power spectrum values and the power law relation slopes. Patients with mild hypokinesia had higher HF values than patients with more severe hypokinesia. Tremor and rigidity 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 heart rate variability and the slope of the power law relation. This dysfunction seems to be more profound in patients with more severe Parkinson's disease. (J Neurol Neurosurg Psychiatry 2001;70:305-310)

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The aim of this study was to evaluate cardiovascular responses as a marker of autonomic nervous system (ANS) disturbances in patients with untreated Parkinson's disease (PD) and to assess the relationship between them and the clinical characteristics of PD. The ANS functions were investigated in 50 patients with PD and 55 healthy subjects by measuring standard cardiovascular autonomic reflexes and heart rate variability (HRV) at rest using spectral analysis (the autoregressive model and the fast Fourier transformation), the percentage of the counts of beat-to-beat variation greater than 50 ms and the fractal dimension. Significantly attenuated HRV and deficient blood pressure reaction to tilting were found in the PD patient group. The patients with hypokinesia/rigidity as the initial symptom of PD had a more pronounced HRV deficit than those with tremor onset. Untreated PD patients suffer significant failure in cardiovascular nervous system regulation, and in patients with hypokinesia/rigidity as their initial disease manifestation the risk of this ANS dysfunction is high. However, in the early stages of PD these changes did not reach significance at individual level.

Parkinson's disease is known to affect the reflex cardiovascular control systems, resulting in a suppressed heart rate variability, but present knowledge concerning the long-term characteristics of heart rate and heart rate variability, e. g. circadian regulation, is limited. We investigated the circadian fluctuation of the time domain, frequency domain and some non-linear measures of heart rate variability in 44 untreated patients with Parkinson's disease and 43 age- and sex-matched control subjects.In the parkinsonian patients, the measured power spectral components of heart rate variability (low-frequency power and high-frequency power) and the SD(1) value of the Poincaré two dimensional vector analysis, that quantifies the short term beat-to-beat variability, were suppressed at night. During the daytime only the SD1 of the Poincaré was suppressed. The night-to-day-ratios of the heart rate variability measures did not differ significantly between the patients and the controls. The results indicate that the long-term parasympathetic cardiovascular regulation is impaired in untreated patients with Parkinson's disease. The dysfunction is more pronounced at night.

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