Impact Of BMI On Cardiovascular Responses To Exercise Testing In Postural Orthostatic Tachycardia Syndrome

Postural orthostatic tachycardia syndrome (POTS) is characterized by profound exercise intolerance. Obesity associated with sedentary behavior and deconditioning is also closely linked to exercise intolerance. The relationship between obesity (i.e. body mass index, BMI) and the cardiovascular response to exercise in POTS has not been examined. PURPOSE: To examine the impact of BMI on exercise capacity and the cardiovascular response to exercise in POTS. METHODS: Retrospective study of 195 POTS patients (female: n = 168, male: n = 27) who completed a cardiopulmonary exercise test between 2019-2023 with measured peak oxygen consumption (VO2peak), O2 pulse, O2 uptake efficiency slope (OUES), heart rate (HR) and systolic blood pressure (SBP). Chronotropic index (CI) and % predicted values were calculated. Patients were grouped by BMI: underweight (UW: BMI <18.5 kg/m2), healthy weight (HW: BMI 18.5 to <25 kg/m2), overweight (OW: BMI 25 to <30 kg/m2), obese (OB: BMI ≥30 kg/m2). ANOVA (Tukey’s post hoc) was performed. RESULTS: There were no differences across groups for age (UW, n = 14: 24.6 ± 5.8; HW, n = 121: 27.2 ± 7.6; OW, n = 36: 27.7 ± 8.0; OB, n = 24: 30.0 ± 7.5 yrs) or height (UW: 167.1 ± 4.8; HW: 169.7 ± 7.6; OW: 168.8 ± 7.9; OB: 171.0 ± 8.9 cm) (p > 0.05). Compared to OB, UW and HW demonstrated lower VO2peak, % predicted VO2peak, O2 pulse, and OUES (Fig. 1). Similarly, SBP was lower in UW and HW compared to OB (UW: 137.3 ± 10.1 vs. HW: 146.1 ± 20.9 vs. OW: 147.6 ± 25.0 vs. OB: 159.5 ± 20.8 mmHg) respectively (both, p < 0.05). There were no differences across groups for HRpeak, % predicted HRpeak, or CI (p > 0.05). CONCLUSION: POTS patients demonstrate significant deconditioning with poor exercise capacity. Patients with the highest BMI demonstrate higher exercise capacity and overall better cardiovascular function. These data suggest a paradoxical relationship between BMI and exercise capacity in POTS patients. Additional research examining body composition in POTS is warranted.