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 (VO2) 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 VO2 z-score was associated with higher submaximal HR z-score (P= 0.02) and lower body mass index z-score (P= 0.01). Higher VO2peak was associated with higher submaximal VO2 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 VO2 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.