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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.
Classification of evidence: 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.
GLOSSARY
- BP=
- blood pressure;
- CI=
- confidence interval;
- CO=
- cardiac output;
- HFRRI=
- high-frequency R-R interval;
- HR=
- heat rate;
- LFRRI=
- low-frequency R-R interval;
- MAP=
- mean arterial pressure;
- POTS=
- postural tachycardia syndrome;
- SV=
- stroke volume;
- SVR=
- systemic vascular resistance;
- VO2max=
- peak oxygen consumption
Footnotes
Go to Neurology.org for full disclosures. Funding information and disclosures deemed relevant by the authors, if any, are provided at the end of the article.
- Received October 13, 2012.
- Accepted in final form January 29, 2013.
- © 2013 American Academy of Neurology
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