Impaired cardiac autonomic control in response to active standing in parkinson’s disease with orthostatic hypotension

Orthostatic hypotension (OH) is a non-motor common feature of Parkinson’s disease that can have a significant impact on quality of life, particularly during various daily activities. Unfortunately the underlying mechanisms that are potentially contributing to OH in Parkinson’s patients (PD) are not fully understood, but previous studies have indicated that cardiovascular autonomic dysfunction is an important player. Herein, the present study was undertaken to test the hypothesis that PD with OH have impaired cardiac autonomic control in response to active standing when compared to their counterparts without OH. Six Parkinson’s patients with OH (69 ± 3 yrs; 1 female) and six without OH (67 ± 3 yrs; 3 females) were enrolled. Oscillometric blood pressure (Microlife 3BTO-A) and beat-to-beat variations of heart rate (Polar RS800) were measured at supine rest (5-min) and during active standing (5-min). Power spectral analysis was employed and the ratio between low and high frequency components (LF/HF ratio) of heart rate variability was used as a surrogate of sympatho-vagal balance. At supine rest, there were no significant differences in blood pressure, heart rate or LF/HF ratio between groups. On standing, systolic blood pressure fell only in PD + OH group (-20 ± 2 mmHg, P < 0.05), while the increase in heart rate was not different between groups. In patients without OH, standing was accompanied by a significant increase in LF/HF ratio (+5.3 ± 2; P < 0.05), while PD + OH group exhibited a blunted LF/HF ratio in response to standing (-1.1 ± 3; P > 0.05). In conclusion, patients with PD + OH have impaired sympatho-vagal balance in response to active standing.