Cardiac origins of the postural orthostatic tachycardia syndrome.
Level 3 - non-randomized controlled study
Non-randomized controlled comparison with a prospective pre-post exercise intervention cohort
PubMed 20579544 · doi:10.1016/j.jacc.2010.02.043
What was done
Twenty-seven patients with postural orthostatic tachycardia syndrome (POTS) and 16 healthy controls underwent autonomic function testing, cardiac magnetic resonance imaging, and blood volume measurements. Twenty-five POTS patients participated in a 3-month tailored exercise training program, with 19 completing the program and undergoing post-intervention reassessment.
What was found
Compared to healthy controls, POTS patients at baseline had higher upright heart rate and total peripheral resistance, lower stroke volume and cardiac output, smaller left ventricular mass (median 1.26 g/kg vs. 1.45 g/kg; p < 0.01), and lower blood volume (60 ml/kg vs. 71 ml/kg; p < 0.01). Baroreflex function was similar between groups. Following 3 months of exercise training in 19 completers, left ventricular mass increased by ~12%, blood volume increased by ~7%, and upright heart rate decreased by 9 beats/min (interval: 1 to 17 beats/min). Ten of 19 patients no longer met POTS diagnostic criteria, and 36-item Short-Form Health Survey quality-of-life scores improved across all patients.
Why it matters
These findings suggest that POTS pathophysiology in many patients involves cardiac remodeling and hypovolemia rather than autonomic neuropathy. It establishes physiological support for structured physical conditioning as a targeted therapy.
Limits
The sample size was small (27 patients, 16 controls). The exercise intervention lacked a randomized or sham control group, leaving open the influence of non-specific trial effects. Additionally, 6 of 25 patients (24%) did not complete the exercise program, introducing potential attrition bias.
Cited by
- supports Patients with postural orthostatic tachycardia syndrome (POTS) exhibit reduced cardiac muscle mass similar to the reduction seen in bed rest and spinal cord injury.