Abstract Body (Do not enter title and authors here): Introduction: Postural orthostatic tachycardia syndrome (POTS) is a chronic syndrome with symptoms of orthostatic intolerance, tachycardia, and exercise intolerance. POTS predominately affects young females, with notable variations in incidence and manifestations between females and males. Limited data exist on sex differences in the response to cardiopulmonary exercise test (CPET) in patients diagnosed with POTS.
Methods: Retrospective analysis of 307 POTS patients who underwent CPET between 2000 and 2023 at Mayo Clinic. Diagnosis of POTS was confirmed by tilt-table testing with a sustained increase in heart rate (HR)≥ 30 bpm or HR>120 bpm 10-min post-tilt and without orthostatic hypotension. Patients were grouped by sex (male: n=48 and female: n=259). Predicted peak values were calculated and independent t-tests were used to compare between-group differences.
Results: There were no significant differences between males and females for age (28±8 vs 27±7, years) or body mass index (24±5 vs 24±5, kg/m²) (both p>0.05). The time between diagnosis and CPET was not significantly different between males and females (21±113 vs 44±280 days, p>0.05). Resting HR was lower in male patients (76±17 vs 85±18 bpm, p<0.05). At peak exercise, there was no difference in respiratory exchange ratio (1.18±.2 vs 1.17±0.1, p>0.05). Males had significantly lower peak HR (171±22 vs 176±19 bpm) and lower percent (%) predicted peak HR (88±12 vs 93±13 %) (both p<0.05) compared to females. Peak oxygen consumption (VO₂peak) was significantly higher in males (29.2±8 vs 24.9±7 mL/kg/min), however; % predicted VO₂peak was lower in males (65±17 vs 71±18 %) (both p<0.05). Peak oxygen (O₂) pulse was higher in males (14±4 vs 9±2 mL/beat, p<0.05) with no difference in % predicted peak O₂ pulse (73±17 vs 78±17 %, p>0.05).
Conclusion: These data suggest male patients achieved a lower peak HR, % predicted peak HR, and % predicted VO₂peak than female patients. Both male and female patients utilized a similar % predicted peak O₂ pulse. These findings suggest male POTS patients demonstrate more impaired exercise tolerance compared to female patients. Additional research is needed to fully elucidate the underpinning physiologic mechanisms responsible for impaired exercise tolerance in POTS and the apparent sex differences in exercise capacity.