title: Low-dose propranolol and exercise capacity in postural tachycardia syndrome: a randomized study.
abstract: OBJECTIVE
  To determine the effect of low-dose propranolol on maximal exercise capacity in patients with postural tachycardia syndrome (POTS).
  
  
  METHODS
  We compared the effect of placebo vs a single low dose of propranolol (20 mg) on peak oxygen consumption (VO2max), an established measure of exercise capacity, in 11 patients with POTS and 7 healthy subjects in a randomized, double-blind study. Subjects exercised on a semirecumbent bicycle, with increasing intervals of resistance to maximal effort.
  
  
  RESULTS
  Maximal exercise capacity was similar between groups following placebo. Low-dose propranolol improved VO2max in patients with POTS (24.5 ± 0.7 placebo vs 27.6 ± 1.0 mL/min/kg propranolol; p = 0.024), but not healthy subjects. The increase in VO2max in POTS was associated with attenuated peak heart rate responses (142 ± 8 propranolol vs 165 ± 4 bpm placebo; p = 0.005) and improved stroke volume (81 ± 4 propranolol vs 67 ± 3 mL placebo; p = 0.013). In a separate cohort of POTS patients, neither high-dose propranolol (80 mg) nor metoprolol (100 mg) improved VO2max, despite similar lowering of heart rate.
  
  
  CONCLUSIONS
  These findings suggest that nonselective β-blockade with propranolol, when used at the low doses frequently used for treatment of POTS, may provide a modest beneficial effect to improve heart rate control and exercise capacity.
  
  
  METHODS
  This study provides Class II evidence that a single low dose of propranolol (20 mg) as compared with placebo is useful in increasing maximum exercise capacity measured 1 hour after medication.
authors.affiliation: Department of Medicine, Division of Clinical Pharmacology, Vanderbilt University, Nashville, TN, USA.
authors.forename: Amy C
authors.initials: AC
authors.lastname: Arnold
authors.forename: Luis E
authors.initials: LE
authors.lastname: Okamoto
authors.forename: André
authors.initials: A
authors.lastname: Diedrich
authors.forename: Sachin Y
authors.initials: SY
authors.lastname: Paranjape
authors.forename: Satish R
authors.initials: SR
authors.lastname: Raj
authors.forename: Italo
authors.initials: I
authors.lastname: Biaggioni
authors.forename: Alfredo
authors.initials: A
authors.lastname: Gamboa
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005080:Exercise Test / Q000379:methods*; D005260:Female; D006801:Humans; D010101:Oxygen Consumption / Q000187:drug effects* / Q000502:physiology*; D054972:Postural Orthostatic Tachycardia Syndrome / Q000175:diagnosis* / Q000188:drug therapy* / Q000503:physiopathology; D011433:Propranolol / Q000008:administration & dosage*; D055815:Young Adult
chemical_list: D011433:Propranolol