Role of peripheral vascular resistance as an indicator of cardiovascular abnormalities in patients with Parkinson's disease.

The aim of this study was to evaluate cardiovascular autonomic modulation in response to an orthostatic stress in healthy subjects and Parkinson's disease (PD). The study included 47 controls and 56 PD patients divided into groups (vasoconstrictor PD, vasodilator PD, control) according to vasodilation/vasoconstriction response during 70° head up tilt test. Using impedance cardiography (ICG) and electrocardiography (ECG) we measured stroke volume, cardiac output, left ventricular work index, left ventricular ejection time, acceleration index, index of contractility, Heather index, thoracic fluid content, total peripheral resistance, total arterial compliance. We also analyzed heart rate variability (HRV), using spectral analysis and continuous blood pressure (contBP). At rest, the vasodilator PD group showed significantly higher values of total peripheral resistance and lower values of stroke volume and cardiac output, compared to the vasoconstrictor PD and the control groups. A post-tilt drop in ∆ (change rest - tilt) systolic blood pressure, ∆mean blood pressure, ∆total peripheral resistance and ∆Heather index, and a significantly lower increase in ∆diastolic blood pressure was observed in subjects from the vasodilator PD group compared to the vasoconstrictor PD and the control groups. No statistically significant differences were observed for HRV parameters between the vasoconstrictor and vasodilator PD groups, P > .05. Longer duration and higher disease stage of PD correlated with a reduction in post-tilt systolic blood pressure changes in vasodilator group. Positive inotropy of the cardiac muscle represents a significant factor preventing orthostatic hypotension in PD subjects with a concurrent drop in peripheral vascular resistance during orthostatic stress.