title: Heart rate variability in complex regional pain syndrome during rest and mental and orthostatic stress.
abstract: BACKGROUND
  Complex regional pain syndrome (CRPS) is a pain condition with regional sensory and autonomic abnormalities in the affected limb. The authors studied systemic autonomic and hemodynamic function in CRPS patients during rest, and during orthostatic and mental arithmetic stress.
  
  
  METHODS
  Twenty patients with CRPS and 20 age-, sex-, and body mass index-matched control subjects participated. Mean values of heart rate variability, baroreceptor sensitivity, blood pressure, stroke volume, cardiac output, and total peripheral resistance were estimated during supine rest and 60° tilt-table testing. On a separate day, heart rate variability was also measured during mental arithmetic stress testing induced by a paced auditory serial addition task.
  
  
  RESULTS
  Heart rate was increased and heart rate variability reduced in patients with CRPS patients compared with control subjects during rest and mental and orthostatic stress, whereas baroreceptor sensitivity was unaffected. When tilted from supine to upright position, patients with CRPS were not able to preserve cardiac output in comparison with control subjects, and they exhibited an exaggerated increase in the total peripheral resistance. The hemodynamic changes correlated to pain duration but not to pain intensity.
  
  
  CONCLUSIONS
  The increased heart rate and decreased heart rate variability in CRPS suggest a general autonomic imbalance, which is an independent predictor for increased mortality and sudden death. The inability of the patients to protect their cardiac output during orthostatic stress was aggravated with the chronicity of the disease.
authors.affiliation: Danish Pain Research Center and Department of Neurology, Aarhus University Hospital, Aarhus, Denmark. a.terkelsen@dadlnet.dk
authors.forename: Astrid J
authors.initials: AJ
authors.lastname: Terkelsen
authors.forename: Henning
authors.initials: H
authors.lastname: Mølgaard
authors.forename: John
authors.initials: J
authors.lastname: Hansen
authors.forename: Nanna B
authors.initials: NB
authors.lastname: Finnerup
authors.forename: Karsten
authors.initials: K
authors.lastname: Krøner
authors.forename: Troels S
authors.initials: TS
authors.lastname: Jensen
mesh_terms: D000328:Adult; D001341:Autonomic Nervous System / Q000503:physiopathology; D015992:Body Mass Index; D020918:Complex Regional Pain Syndromes / Q000503:physiopathology*; D004562:Electrocardiography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D054971:Orthostatic Intolerance / Q000503:physiopathology*; D010147:Pain Measurement; D011311:Pressoreceptors / Q000502:physiology; D012146:Rest / Q000502:physiology*; D012907:Smoking / Q000503:physiopathology; D013315:Stress, Psychological / Q000503:physiopathology*; D016683:Supine Position / Q000502:physiology; D018667:Tilt-Table Test; D055815:Young Adult