title: Deconditioning in patients with orthostatic intolerance.
abstract: OBJECTIVE
  To study the frequency and degree of deconditioning, clinical features, and relationship between deconditioning and autonomic parameters in patients with orthostatic intolerance.
  
  
  METHODS
  We retrospectively studied all patients seen for orthostatic intolerance at Mayo Clinic between January 2006 and June 2011, who underwent both standardized autonomic and exercise testing.
  
  
  RESULTS
  A total of 184 patients (84 with postural orthostatic tachycardia syndrome [POTS] and 100 without orthostatic tachycardia) fulfilled the inclusion criteria. Of these, 89% were women, and median age was 27.5 years (interquartile range [IQR] 22-37 years). Symptom duration was 4 years (IQR 2-7.8). Of the patients, 90% had deconditioning (reduced maximum oxygen uptake [VO(2max)%] <85%) during exercise. This finding was unrelated to age, gender, or duration of illness. The prevalence of deconditioning was similar between those with POTS (95%) and those with orthostatic intolerance (91%). VO(2max)% had a weak correlation with a few autonomic and laboratory parameters but adequate predictors of VO(2max)% could not be identified.
  
  
  CONCLUSIONS
  Reduced VO(2max)% consistent with deconditioning is present in almost all patients with orthostatic intolerance and may play a central role in pathophysiology. This finding provides a strong rationale for retraining in the treatment of orthostatic intolerance. None of the autonomic indices are reliable predictors of deconditioning.
authors.affiliation: Department of Neurology, Mayo Clinic, Rochester, MN, USA.
authors.forename: Ajay
authors.initials: A
authors.lastname: Parsaik
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Allison
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Singer
authors.forename: David M
authors.initials: DM
authors.lastname: Sletten
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Joyner
authors.forename: Eduardo E
authors.initials: EE
authors.lastname: Benarroch
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Low
authors.forename: Paola
authors.initials: P
authors.lastname: Sandroni
mesh_terms: D000328:Adult; D001794:Blood Pressure; D018493:Cardiovascular Deconditioning / Q000502:physiology*; D005080:Exercise Test; D005260:Female; D006339:Heart Rate; D006801:Humans; D008297:Male; D054971:Orthostatic Intolerance / Q000150:complications*; D054972:Postural Orthostatic Tachycardia Syndrome / Q000150:complications*; D012018:Reflex; D012189:Retrospective Studies; D018709:Statistics, Nonparametric; D014636:Valsalva Maneuver / Q000502:physiology; D055815:Young Adult