BACKGROUND:Most single ventricle patients undergo Fontan procedure in a staged manner. However, optimal timing of Fontan completion after an intermediate staging surgery is controversial. Therefore, we investigated the long-term impact of age at Fontan completion on the exercise performance in adolescents. METHODS:We analyzed National Institutes of Health/National Heart, Lung and Blood Institute Pediatric Heart Network Fontan Cross-Sectional Study dataset consisting of children and adolescents 6 to 18 years of age recruited in 2003 to 2004. Multivariate linear regression techniques were used to evaluate association of age at Fontan procedure with percent predicted VO2 maximum, percent predicted maximum O2 pulse, and heart rate reserve in patients who achieved ventilatory anaerobic threshold (VAT). RESULTS:Of the 405 patients who had undergone only one Fontan operation and ramp cycle ergometry, 72% had prior intermediate surgery. Mean age at Fontan completion and exercise testing was 3.4±2 and 12.4±3.2 years. Three hundred twelve patients reached VAT suggesting adequate cardiopulmonary effort. In patients who reached VAT, each year increase in age at Fontan completion was associated with a decline of 1.5 (95% CI -2.5 to -0.5) points in percent-predicted VO2 maximum and a decline of 4.1 (95% CI -6.0 to -2.1) beat/min in heart rate reserve after adjusting for all pertinent variables. CONCLUSIONS:Fontan completion at a younger age is associated with better exercise performance in adolescents.