title: Postural orthostatic tachycardia syndrome: the Mayo clinic experience.
abstract: OBJECTIVE
  To evaluate the prevalence and pathogenetic mechanisms of postural orthostatic tachycardia syndrome (POTS).
  
  
  METHODS
  We reviewed the medical records of patients with POTS seen at the Mayo Clinic in Rochester, Minn, from January 1, 1993, through December 31, 2003. All patients were required to have had a full autonomic reflex screen. The results of the following additional tests were evaluated: thermoregulatory sweat test, plasma catecholamine measurement, serum ganglionic (a3) acetylcholine receptor antibody detection, and 24-hour urinary sodium measurement.
  
  
  RESULTS
  We identified 152 patients (86.8% female; mean +/- SD age, 30.2+/-10.3 years) with a mean duration of symptoms of 4.1 years. The mean orthostatic heart rate increment was 44 beats/min. Half the patients had sudomotor abnormalities (apparent on both the quantitative sudomotor axon reflex test and thermoregulatory sweat test), and 34.9% had significant adrenergic impairment, indicating that at least half of the patients had a neuropathic pattern of POTS. In 13.8% of patients, onset was subacute, and ganglionic acetylcholine receptor antibody was detected in 14.6%, suggesting an autoimmune origin in at least 1 in 7 patients. Hyperadrenergic status was documented in 29.0% of patients (standing plasma norepinephrine level 2600 pg/mL), and at least 28.9% were presumably hypovolemic (24-hour urinary sodium level <100 mEq/24h). The lack of correlation between urinary sodium and standing norepinephrine levels suggests that mechanisms other than hypovolemia accounted for the hyperadrenergic state.
  
  
  CONCLUSIONS
  Our findings suggest a neuropathic basis for at least half the cases of POTS and that a substantial percentage of cases may be autoimmune. Hyperadrenergic and hypovolemic correlates are likely compensatory or exacerbating.
authors.affiliation: Autonomic Disorders Center, Department of Neurology, Mayo Clinic College of Medicine, Rochester, Minn 55905, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Thieben
authors.forename: Paola
authors.initials: P
authors.lastname: Sandroni
authors.forename: David M
authors.initials: DM
authors.lastname: Sletten
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Benrud-Larson
authors.forename: Robert D
authors.initials: RD
authors.lastname: Fealey
authors.forename: Steven
authors.initials: S
authors.lastname: Vernino
authors.forename: Vanda A
authors.initials: VA
authors.lastname: Lennon
authors.forename: Win-Kuang
authors.initials: WK
authors.lastname: Shen
authors.forename: Phillip A
authors.initials: PA
authors.lastname: Low
mesh_terms: D000328:Adult; D001342:Autonomic Nervous System Diseases / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology; D016009:Chi-Square Distribution; D005260:Female; D006801:Humans; D007024:Hypotension, Orthostatic / Q000175:diagnosis* / Q000453:epidemiology / Q000276:immunology* / Q000503:physiopathology; D008297:Male; D008910:Minnesota / Q000453:epidemiology; D012189:Retrospective Studies; D013577:Syndrome