Exercise Training for POTS
Abstract & Commentary
By Michael H. Crawford, MD
Source: Fu Q, et al. Cardiac origins of the postural orthostatic tachycardia syndrome. J Am Coll Cardiol. 2010;55:2858-2868.
Postural orthostatic tachycardia syndrome (POTS) is a disabling orthostatic intolerance that mainly occurs in pre-menopausal women. Since the tachycardia has been shown to be due to low stroke volume, left ventricular (LV) volumes and mass, these investigators tested the hypothesis that exercise training would improve, or even eliminate, this syndrome. They approached 54 consecutive POTS patients in their autonomic dysfunction clinic and were able to enroll 27 patients (26 women) in the study. All enrolled patients met criteria for POTS: heart rate rise of >30 beats/min. or >120 within 10 minutes of standing, without orthostatic hypotension. Any drug therapy was withdrawn for two weeks. The study participants were compared to 16 matched healthy controls (15 women). None of the participants smoked or were trained athletes. A three-month exercise training program was completed by 19 of the POTS patients and all 16 controls. Pre- and post-exercise training evaluations were compared between the two groups. Upright heart rate and total peripheral resistance were higher in the patients, but LV mass, blood volume, stroke volume, and cardiac output were lower. Baroreflex function was not different between the two groups. Exercise training increased LV mass by 12% and blood volume by 7%; and decreased upright heart rate by 9 bpm. In 10 of the 19 patients, POTS criteria were no longer met after exercise training, and quality of life improved in all patients who completed the exercise program. The authors concluded that in POTS autonomic function is normal, and orthostatic tachycardia is due to reduced LV size and stroke volume. Exercise training improved or cured this syndrome in many patients.
Commentary
POTS can be defined as orthostatic tachycardia without significant hypotension and is a difficult disease to manage because drug therapy is often inadequate. Beta-blockers may slow the heart rate, but may cause hypotension. Alpha agonists can reduce heart rate, but may cause hypertension. Volume expansion can reduce symptoms, but may cause edema. Other therapies have been even less effective. POTS mimics the physiologic findings of prolonged bed rest and space flight, both of which are characterized by deconditioning. Thus, the increase in heart rate is a physiologic response to reduced upright stroke volume rather than an abnormality of autonomic function. This may explain why it is more common in women, because they have smaller hearts and lower stroke volumes normally. Since exercise can increase cardiac chamber volume, mass, stroke volume, and cardiac output, it made sense to try it as a therapy. This study which demonstrates that exercise training may help these patients is encouraging.
This was a small, but very carefully done study of well-characterized POTS patients. They had extensive autonomic nervous system testing, cardiac MRI, elegant cardiac output and blood volume measurements. During upright tilt testing many patients and controls developed pre-syncopal symptoms, but there was no syncope observed. Exercise began with semi-recumbent bicycle, rowing or swimming and progressed to more upright exercise. Weight lifting also was done. Overall maximum oxygen uptake increased 11% after three months. The positive changes in this study cannot be attributed to exercise training alone since the patients were encouraged to ingest more salt and water, and to elevate the head of their bed. Also, for many people this intensity of exercise training is not feasible. Even in this study only three quarters of a select group of patients finished the three months of training. However, given the alternatives, this appears to be a reasonable recommendation, which may help the more motivated individuals with POTS.
Postural orthostatic tachycardia syndrome (POTS) is a disabling orthostatic intolerance that mainly occurs in pre-menopausal women.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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