Risk Factors of Exercise Intolerance in Children and Adolescents After Total Cavopulmonary Connection

(1) Background: Exercise intolerance is a nearly ubiquitous consequence among patients who have undergone the total cavopulmonary connection (TCPC) or modified Fontan procedure; however, the specific factors influencing this condition—especially the impact of surgical timing and perioperative management—remain inadequately understood. (2) Methods: From a retrospective cohort of 255 TCPC patients, 99 who had undergone cardiopulmonary exercise testing (CPET) were included. Patients were stratified into a normal exercise tolerance group (ET group, peak VO2 ≥ 80% predicted, n = 45) and an exercise intolerance group (EI group, peak VO2 < 80% predicted, n = 54). Univariate and multivariate logistic regression analyses were performed to identify risk factors for decreased exercise tolerance. (3) Results: Patients in EI group were older at TCPC surgery (4.67 vs. 3.60 years, p = 0.004) and CPET (10.11 vs. 8.65 years, p = 0.01). They had longer operation time (312.14 vs. 267.53 min, p = 0.01), bypass time (122.26 vs. 103.59 min, p = 0.045), and higher rate of prolonged ICU stay (>3 days, 68.9% vs. 31.1%, p = 0.01). ROC analysis determined optimal surgical age cut-off at 3.81 years (AUC = 0.692, p = 0.001). Univariate analysis identified age ≥ 3.8 years, ICU stay > 3 days, longer operation/bypass times, and postoperative atrioventricular valve regurgitation as significant risk factors. Multivariate analysis confirmed age at TCPC ≥3.8 years (OR = 2.54, 95% CI: 1.01–6.42, p = 0.049) and ICU stay >3 days (OR = 2.61, 95% CI: 1.07–6.39, p = 0.04) as independent predictors of exercise intolerance. (4) Conclusions: The delayed completion (beyond 3.8 years of age) of TCPC procedure and the occurrence of early postoperative complications are associated with reduced long-term exercise capacity.