Beat-to-beat variability of blood pressure in patients with Parkinson's disease
Autonomic nervous system, peripheral vascular resistance, cardiac output.
Parkinson's disease (PD) is a progressive neurodegenerative disease characterized by motor and non-motor symptoms, including autonomic dysfunction (AD), which can appear up to 10 years before the motor symptoms. In the cardiovascular system, AD can result in blood pressure (BP) abnormalities, such as changes in its variability. Considering that beat-to-beat resting BP variability (ABPV) is an important predictor of cardiovascular risk and target-organ damage, the aim of the study was to evaluate the ABPV of patients with PD. For this, beat-to-beat heart rate (electrocardiogram) and BP (digital photoplethysmography) were continuously measured in 18 PD volunteers, 16 age-matched controls and 18 youths. The systolic volume was estimated from the BP waveform (ModelFlow) allowing the calculation of cardiac output (CO) and total peripheral resistance (PTR). The PD group had lower VPA across standard deviation in systolic BP (5.6 ± 1.8 vs. 7.5 ± 2.5 mmHg, P = 0.017), diastolic BP (2.5 ± 0.7 vs. 3.7 ± 0.9 mmHg, P = 0.000) and mean BP ( 3.3 ± 0.8 vs. 4.6 ± 1.3 mmHg, P = 0.001), as well as in TPR (1.2 ± 0.9 vs. 2.5 ± 1.6 mmHg/L/min, P = 0.001), but not in DC (0.4 ± 0.1 vs. 0.3 ± 0.1 L/mmHg, P = 0.409), when compared to the Elderly group. Similar results were found using CV%. Taken together, the findings suggest that PD causes a decrease in VPA through mechanisms associated with TPR, but not with CD.