Introduction: Exercise capacity is known to decline during adolescence in Fontan patients. Vascular function, which correlates with exercise capacity, has not been studied longitudinally in Fontan circulation.
Methods: Prospective single-center longitudinal study of Fontan survivors. Aerobic capacity was determined using cardiopulmonary exercise testing, expressed as peak oxygen consumption (VO2). Assessment of endothelial function (flow mediated dilation [FMD] and reactive hyperemia index [RHI]) and arterial stiffness (augmentation index [AI]) was performed with brachial FMD and peripheral arterial tonometry. Paired testing was obtained at a mean interval of 2.0 ± 0.2 yrs. Rate of change was calculated by linear regression. Bivariate and multivariable analyses were used to identify factors associated with a greater rate of change.
Results: The cohort consisted of 50 patients (54% male). Mean age at enrollment was 13.7 ± 4.2 yrs and at Fontan completion was 3.9 ± 1.3 yrs. A single left ventricle was present in 65%; Fontan type was extracardiac in 84%. Peak VO2 declined by 0.44 ± 0.2 ml/kg/min/yr (p=0.03). Decreases in FMD (0.17 ± 0.13%/yr) and RHI (0.002 ± 0.01/yr) were not significant (Figure). AI improved by 0.74 ± 0.3/yr (p=0.02). Changes in FMD, RHI and AI did not correlate with change in peak VO2. In multivariable analysis, changes in height, weight, BP and age were predictors of the rate of decrease in FMD (R2 0.32, p=0.001), while change in BMI was a predictor for RHI (R2 0.17, p=0.007). Change in resting O2 saturation was the only predictor of the rate of change in AI (R2 0.09, p=0.04). Fontan type and ventricular morphology were not predictors of changes in vascular measures.
Conclusions: In contrast to the progressive decline in aerobic capacity, vascular function does not change uniformly in Fontan survivors. Changes in vascular function do not relate to changes in aerobic capacity but are associated with changes in anthropometric measures and O2 saturation.