To determine the association of cardiopulmonary exercise testing (CPET) variables with transplant-free survival in children who have undergone a Fontan procedure.

A retrospective review of patients ≤ 18 years of age who had a lateral tunnel or extracardiac Fontan and underwent a CPET between 2004 and 2022. Serial analysis was performed for patients with CPETs ≥ 1 year apart. Cardiovascular adverse events (CAEs) were categorized as mortality or cardiac transplantation. Univariable regression analysis was performed to evaluate predictors of CAE.

A total of 118 patients were included. The mean age at the baseline CPET was 12.9 ± 2.7 years, age at Fontan operation was 3.2 ± 1.8 years, and 65.3% of the cohort were male. The baseline peak oxygen uptake (VO_2peak) was 32.3 ± 7.7 mL/kg/min (74.6 ± 17.8% of expected). A second CPET was performed in 63 of 118 (53.3%) patients with a mean duration between CPETs of 3.1 ± 2.4 years. The percent of expected peak oxygen uptake decreased by 1.36 ± 8.05% per year. A total of 14 (11.9%) patients had CAE over a mean follow up time of 7.8 ± 4.8 years. In univariable regression analysis using baseline CPETs, exercise duration (heart rate [HR] = 0.69, P = .05) and percent of age-predicted maximal HR achieved (HR 0.98, P = .02) were significantly associated with CAE.

Exercise capacity is mildly depressed in a contemporary cohort of Fontan patients in early adolescence and gradually declines into early adulthood. Exercise duration and percentage-predicted maximal HR achieved was significantly associated with CAE.