Enhanced Physiology for Submaximal Exercise in Children after the Fontan Procedure

BANKS, L., B. W. MCCRINDLE, J. L. RUSSELL, and P. E. LONGMUIR. Enhanced Physiology for Submaximal Exercise in Children after the Fontan Procedure. Med. Sci. Sports Exerc., Vol. 45, No. 4, pp. 615-621, 2013. Purpose: After the Fontan procedure, children exhibit reduced peak exercise capacity, yet their submaximal exercise response remains unclear. This study sought to determine the relationship between submaximal and peak exercise capacity and physical activity in Fontan patients. Methods: This cross-sectional study recruited 50 Fontan patients (59% males) with a median age of 9 yr (range = 6-12 yr). The median age at Fontan procedure was 2.9 yr (range = 1.6-9.1 yr). Study assessments included medical history, exercise testing, and accelerometry. Results: Significantly lower submaximal oxygen consumption ((V)over dotO(2)) and HR in response to a standardized workload than published values for healthy children (mean +/-SD) of -1.72 +/-5.24 (P < 0.001) and -1.45 +/-1.98 (P < 0.001), respectively, suggest enhanced submaximal work efficiency in this group of patients after Fontan. Higher submaximal (V)over dotO(2) z-score was associated with higher submaximal HR z-score (P = 0.02) and lower body mass index z-score (P = 0.01). Higher (V)over dotO(2peak) was associated with higher submaximal (V)over dotO(2) z-score (P = 0.01), male sex (P = 0.03), higher RER (P = 0.02), lower submaximal HR z-score (P < 0.01), and higher chronotropic responsiveness (P < 0.0001). Exercise test duration z-score was associated with lower submaximal HR z-score (P = 0.02) and higher chronotropic responsiveness (P = 0.02). Conclusions: Fontan patients exhibited a lower submaximal (V)over dotO(2) and HR responsiveness at a given workload than healthy controls did during standardized exercise testing. Thus, they may be better adapted to perform submaximal exercise. Although peak exercise capacity is limited, Fontan patients are able to perform submaximal physical activities at the same level as their healthy peers.