Does Acute Exercise Impact Central Hemodynamics In Adults With POTS?

Postural Orthostatic Tachycardia (POTS) is a heterogenous autonomic disorder marked by indicators of cardiovascular disease (CVD) risk, including sympathetic dysfunction, blood pressure abnormalities, and endothelial dysfunction. POTS is predominately studied in premenopausal females in which the long-term implications of POTS are unclear and CVD risk may be undetected. As acute aerobic exercise can positively affect central hemodynamic load by attenuating wave reflections and arterial stiffness, exercise may improve subclinical CVD risk in POTS patients. PURPOSE: To explore the effects of acute aerobic exercise on subclinical CVD risk in POTS by comparing wave reflections and aortic stiffness in POTS patients compared to healthy controls before and after semi-recumbent cycling. METHODS: Four POTS patients (25.0 ± 4.3 years; 3 females) and nine healthy controls (31.2 ± 12.4 years; 4 females) underwent subclinical vascular assessment before and fifteen minutes after a 30-minute bout of moderate-intensity recumbent cycling (40-60% heart rate reserve). Aortic pressure waveforms were determined using pulse wave analysis and a generalized transfer function from radial pressure waveforms. Augmentation index (AIx) was taken as a global measure of wave reflections. Central aortic stiffness was measured via carotid-femoral pulse wave velocity (cfPWV) using applanation tonometry. Two-way analysis of variance determined differences in measures of central hemodynamic load between groups (POTS, controls) and across time (pre-exercise, post-exercise). RESULTS: There were no significant group by time interactions for AIx (POTS: 9.3 ± 18.6 vs. 7.0 ± 14.2%, controls: 16.9 ± 12.7 vs. 10.9 ± 13.9%; p = 0.50), heart rate-corrected AIx (POTS: 3.9 ± 17.0 vs. 5.5 ± 11.2%, controls: 7.6 ± 11.1 vs. 4.4 ± 13.5%; p = 0.41), or cfPWV (POTS: 5.7 ± 0.7 vs. 5.9 ± 1.1 m/s, controls: 5.6 ± 1.1 vs. 5.7 ± 1.1 m/s; p = 0.50), such that POTS and healthy controls responded similarly before and after exercise in terms of central hemodynamic load. CONCLUSION: POTS patients have similar central hemodynamic load compared to healthy controls in response to an acute bout of exercise. We may see future significant effects of exercise on hemodynamics between groups with a larger sample size as this study is currently ongoing.