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

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

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). There were 18 individuals with obesity (BMI 36.4 ± 3 kg/m²) and 59 with overweight/normal BMI (BMI 24.1 ± 3.6 kg/m²). Peak oxygen consumption (VO₂) on non-invasive 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 (Q_s) [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 with 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].

Adults post-Fontan with obesity have worse aerobic capacity, increased Q_s, higher filling pressures, and decreased arterial O₂ saturation compared with 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 haemodynamics and outcomes requires further study.