Time- and frequency-domain parameters of heart rate variability and sympathetic skin response in Parkinson's disease.

The autonomic nervous system (ANS) is regularly affected in Parkinson's disease (PD). Information on autonomic dysfunction can be derived from e.g. altered heart rate variability (HRV) and sympathetic skin response (SSR). Such parameters can be quantified easily and measured repeatedly which might be helpful for evaluating disease progression and therapeutic outcome. In this 2-center study, HRV and SSR of 45 PD patients and 26 controls were recorded. HRV was measured during supine metronomic breathing and analyzed in time- and frequency-domains. SSR was evoked by repetitive auditory stimulation. Various ANS parameters were compared (1) between patients and healthy controls, (2) to clinical scales (Unified Parkinson's disease rating scale, Mini-Mental State Examination, Becks Depression Inventory), and (3) to disease duration. Root mean square of successive differences (RMSSD) and low frequency/high frequency (LF/HF) ratio differed significantly between PD and controls. Both, HRV and SSR parameters showed low or no association with clinical scores. Time-domain parameters tended to be affected already at early PD stages but did not consistently change with longer disease duration. In contrast, frequency-domain parameters were not altered in early PD phases but tended to be lower (LF, LF/HF ratio), respectively higher (HF) with increasing disease duration. This report confirms previous results of altered ANS parameters in PD. In addition, it suggests that (1) these ANS parameters are not relevantly associated with motor, behavioral, and cognitive changes in PD, (2) time-domain parameters are useful for the assessment of early PD, and (3) frequency-domain parameters are more closely associated with disease duration.

Greater cardiovascular reactivity to a cold stimulus is due to higher cold pain perception in black Africans: the Sympathetic Activity and Ambulatory Blood Pressure in Africans (SABPA) study.

OBJECTIVE: To evaluate the role of pain perception and pain stimulus components for blood pressure responses to stress in the black and the white African population with hypertension. BASIC METHODS: Cardiovascular regulation in response to a cold pressor stimulus was studied in hypertensive black (n = 110) and white (n = 95) Africans. Perception of stressfulness of the task was assessed on a seven-point Likert scale. Chronic stress levels were evaluated by the General Health Questionnaire and the Coping Strategy Indicator was used to assess individual coping behavior. Autonomic and baroreflex function was evaluated by spectral analysis. MAIN RESULTS: The cold pressor test elicited significant blood pressure elevations with higher relative increases in the black Africans. The higher blood pressure reactivity in black Africans was accompanied by a substantially greater cardiac response and lower parasympathetic outflow as compared with white Africans. Black Africans also reported higher chronic stress levels and rated the stimulus as more painful than their white counterparts. A significant interaction was observed for cardiovascular responses with pain perception but not with chronic stress. Individuals with high pain perception exhibited less dampening of autonomic cardiac exertion than those with low or moderate pain perception. PRINCIPAL CONCLUSION: Black Africans display a more pronounced cold pressor test-induced rise in heart rate and blood pressure, which may be explained by greater pain-related increments in blood pressure. A higher cognitive appraisal of pain and a blunted baroreflex-mediated dampening of autonomic structures may contribute to the exaggerated blood pressure reactivity in black Africans.

Influence of ECG sampling frequency on spectral analysis of RR intervals and baroreflex sensitivity using the EUROBAVAR data set.

To evaluate the impact of different ECG sampling frequencies on parameters of spectral and baroreflex analysis. Spectral and baroreflex analyses were performed in the EUROBAVAR data set (46 recordings of 23 persons) using the original ECG sampling frequency of 500 Hz and - simulated - sampling frequencies of 200 and 100 Hz. For this analysis, the technique of trigonometric regressive spectral (TRS) analysis was used. In the standing position, there were no statistically significant differences in baroreflex sensitivity and frequency bands ranging from VLF to HF using 100 Hz instead of the original 500 Hz. Only the UHF band (>0.40 Hz) was significantly different. In the supine position, similar results could be described for 100 Hz, although there were slight, but significant (P < 0.05) changes in baroreflex sensitivity of around 1 ms/mmHg at the simulated 100 Hz. Using a simulated 200 Hz instead of a 500 Hz sampling frequency had no significant impact on the spectral and baroreflex parameters. The probability to demonstrate an impact of different ECG sampling frequencies was higher in people with pathologically decreased variability of RR intervals. In most of the cases, it is sufficient for spectral and baroreflex analysis by TRS to use data with an ECG sampling frequency of 100 Hz in comparison to 500 Hz. Only if there is a pathologically decreased variability of RR intervals in patients, spectral and baroreflex parameters could be significantly influenced by lower ECG sampling frequencies of up to 100 Hz, but only to a minor degree.