Cardiovascular responses during cold pressor test are different in Parkinson disease and multiple system atrophy with parkinsonism.

Abstract

Orthostatic hypotension (OH) is common in Parkinson disease (PD) and multiple system atrophy of parkinsonian type (MSA-P), but the pathophysiology of OH is different in the two. We hypothesised that the baroreflex-independent sympathetic reactivity may also be different in them. To evaluate this we assessed the sympathetic vascular reactivity and the heart rate response to the standard cold pressor test (CPT) in these patients. The study was conducted in ten patients with PD with OH, 5 PD without OH, 13 MSA-P with OH, and 7 MSA-P without OH. Lead II ECG and finger PPG (photoplethysmography) were simultaneously acquired during a baseline period of 1min followed by a 10°C cold exposure (1min) of the contralateral hand (CPT). The vascular response was then evaluated by computing the pulse transit time (PTT). The percentage decrease in PTT during the CPT was significantly higher in patients with PD as compared to MSA-P, irrespective of the presence or absence of OH (-2.74±0.96 vs -0.05±0.75%, p=0.03; PD vs MSA-P with OH and -3.04±0.85 vs 0.48±1.13%, p=0.04; PD vs MSA-P without OH). The rise in heart rate during CPT was similar in patients with PD and MSA-P with or without OH (4.95±1.6 vs 5.99±1.04, p=0.28; PD vs MSA-P with OH and 5.62±1.31 vs 13.15±2.89, p=0.06; PD vs MSA-P without OH). Vasoconstrictor response to CPT is compromised in MSA-P as compared to PD, but the baroreflex-independent heart rate response is similar in the two.