Fontan Conduit Cross-sectional Area and Relationship to Exercise Performance.

BACKGROUND: The synthetic extracardiac (EC) Fontan conduit may become inadequate as patients grow, potentially limiting cardiovascular capacity. OBJECTIVE: To evaluate the relationship between EC-Fontan conduit cross-sectional area (CSA), indexed to body surface area (BSA), and exercise performance. METHODS: A cross-sectional analysis of data from the FORCE registry was performed. Patients with EC-Fontan anatomy who underwent cardiac magnetic resonance imaging (CMR) and cardiopulmonary exercise testing (CPET) within one year of each other were analyzed. Median length-averaged and minimum Fontan CSAs were measured using 3D segmentation and indexed to BSA. The primary outcome was percent predicted peak VO₂ (ppVO₂) on maximal effort CPET. Multivariable linear regression models assessed associations between Fontan CSA/BSA and ppVO₂, adjusting for known predictors of ppVO₂ in Fontan patients. RESULTS: increase length-averaged CSA/BSA was associated with a 0.07% increase in ppVO2 (p<0.001). Fontan CSA/BSA was not significantly associated with cardiac function measures at rest, including ejection fraction and cardiac output. CONCLUSIONS: Smaller EC-Fontan CSA/BSA is independently associated with reduced exercise capacity after controlling for other known predictors of exercise performance.