Cardiopulmonary Exercise Testing Responses in Pediatric Postural Orthostatic Tachycardia Syndrome and Orthostatic Intolerance

To compare exercise testing results of pediatric patients with postural orthostatic tachycardia syndrome (POTS) and orthostatic intolerance (OI) with those of healthy peers and investigate differences in heart rate (HR) kinetics during and after exercise testing. Analysis of maximal exercise data using the Bruce protocol. HR kinetics were analyzed during exercise by comparing the percentage of test completion with percentage of maximal HR and in recovery by calculating HR recovery postcardiopulmonary exercise testing.  A total of 222 patients aged 15.9 (1.7) years participated in this study. POTS and OI patients had worse HR metrics, exercise duration, peak aerobic capacity, and percentage predicted peak aerobic capacity compared with peers. POTS and OI patients had elevated HR responses at 10%, 25%, and 50% of cardiopulmonary exercise testing duration compared with healthy peers. Furthermore, POTS and OI patients had reduced HR recovery at 3, 4, 5, 9, and 10 minutes postcardiopulmonary exercise testing compared with peers. Pediatric POTS and OI patients have decreased exercise capacity, exaggerated submaximal HR responses, and blunted HR recovery compared with healthy peers. Exercise capacity and HR kinetics did not differ between POTS and OI patients. Decreased time to peak HR may explain some of the exercise intolerance observed in pediatric patients with POTS and OI and may be a helpful metric for exercise prescription and outcome tracking.