title: Cardiovascular responses during cold pressor test are different in Parkinson disease and multiple system atrophy with parkinsonism.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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 1 min followed by a 10 °C cold exposure (1 min) of the contralateral hand (CPT). The vascular response was then evaluated by computing the pulse transit time (PTT).
  
  
  RESULTS
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Physiology, AIIMS, New Delhi, India. shanksroy2903@gmail.com.
authors.forename: Sankanika
authors.initials: S
authors.lastname: Roy
authors.affiliation: Department of Neurology, AIIMS, New Delhi, India.
authors.forename: Achal Kumar
authors.initials: AK
authors.lastname: Srivastava
authors.affiliation: Department of Physiology, AIIMS, New Delhi, India.
authors.forename: Ashok Kumar
authors.initials: AK
authors.lastname: Jaryal
authors.affiliation: Department of Physiology, AIIMS, New Delhi, India.
authors.forename: Kishore Kumar
authors.initials: KK
authors.lastname: Deepak
mesh_terms: D000328:Adult; D017704:Baroreflex / Q000502:physiology; D003080:Cold Temperature / Q000009:adverse effects; D006339:Heart Rate / Q000502:physiology; D006801:Humans; D007024:Hypotension, Orthostatic / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D019578:Multiple System Atrophy / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D010300:Parkinson Disease / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology*; D020734:Parkinsonian Disorders / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology
keywords: Autonomic dysfunction; Cold pressor test; Multiple system atrophy; Parkinson disease; Pulse transit time