Cardiopulmonary Exercise Testing in Children and Adolescents with Repaired Tetralogy of Fallot: Mechanisms of...

By comparison with adults, cardiopulmonary exercise testing in children with Tetralogy of Fallot is limited, and its clinical application less clarified. This study provides a comprehensive CPET profile in a child-adolescent population with repaired TOF, explores mechanisms underpinning exercise intolerance and associations with clinical outcome. Seventy-four CPETs were completed in 58 child-adolescents with rTOF (age 13.8 SD 2.4 years). CPET parameters were corrected for age, sex and body size. At follow-up (4.9 years, IQR 3.5-7.9) clinical status and re-intervention was evaluated and CPET indices predicting these outcomes determined. Cohort peak V̇O₂ was within low-normal limits (% pred: 74.1% SD 15.4) with 15 patients (26%) displaying moderately severe reduction in V̇O_2peak (< 65% pred). Oxygen uptake efficiency slope highly correlated with V̇O_2peak (r = 0.94, p < 0.001) and was insensitive to exercise intensity. No significant change in CPET occurred in patients who underwent interval testing at 24 SD 14.5 months, although there was a variable response in V̇O_2peak between individuals. Chronotropic response, lung vital capacity, heart rate-V̇O₂ slope (indicator of stroke volume) predicted oxygen consumption: V̇O_2peak (R² = 50.91%, p < 0.001) and workload (R² = 58.39%, p < 0.001). Adverse clinical status was associated with reduced workload (OR 0.97, p = 0.011). V̇_E/V̇_CO2 slope was steeper in those that died ((%pred:137.8 SD 60.5 vs. 108.4 SD 17.0, p < 0.019). RVOT reintervention post-CPET (24 patients, 43.8%) was associated with an increased gradient of HR-VO₂ slope (OR 1.042, p = 0.004). In child-adolescents with TOF important reductions in cardiopulmonary functioning were apparent in 25% of patients. Exercise intolerance was related to reduced vital capacity, impaired chronotropic response and deficient stroke volume increment.