Fontan hemodynamics in adults with obesity compared to overweight and normal body mass index: a retrospective invasive exercise study.

Aims: The effects of obesity on Fontan hemodynamics are poorly understood. Accordingly, we assessed its impact on exercise invasive hemodynamics and exercise capacity.

Methods: Seventy-seven adults post-Fontan undergoing exercise cardiac catheterization (supine cycle protocol) were retrospectively identified using an institutional database and categorized according to the presence of obesity (body mass index [BMI] >30 kg/m2) and overweight/normal BMI (BMI≤30 kg/m2).

Results: There were 18 individuals with obesity (BMI 36.4±3 kg/m2) and 59 (BMI 24.1±3.6 kg/m2) with overweight/normal BMI. Peak oxygen consumption (VO2) on noninvasive cardiopulmonary exercise testing was lower in patients with obesity (15.6±3.5 vs 19.6±5.8 ml/kg/min, p=0.04). At rest, systemic flow (Qs) (7.0 [4.8; 8.3] vs 4.8 [3.9; 5.8] l/min, p=0.001), pulmonary artery (PA) pressure (16.3±3.5 vs 13.1±3.5 mmHg, p=0.002), and PA wedge pressure (PAWP) (11.7±4.4 vs 8.9±3.1 mmHg, p=0.01) were higher, while arterial O2 saturation was lower (89.5% [86.5; 92.3] vs 93% [90; 95]) in obesity compared to overweight/normal BMI. Similarly, patients with obesity had higher exercise PA pressure (29.7±6.5 vs 24.7±6.8 mmHg, p=0.01) and PAWP (23.0±6.5 vs 19.8±7.3 mmHg, p=0.047), but lower arterial O2 saturation (82.4±7.0% vs 89% [85; 92], p=0.003).

Conclusion: Adults post-Fontan with obesity have worse aerobic capacity, increased Qs, higher filling pressures, and decreased arterial O2 saturation compared to those with overweight/normal BMI, both at rest and during exercise, mirroring the findings observed in the obesity phenotype of heart failure with preserved ejection fraction. Whether treating obesity and its cardiometabolic sequelae in Fontan patients will improve hemodynamics and outcomes requires further study.