Cardiopulmonary Exercise Testing in children and adolescents with repaired Tetralogy of Fallot

Introduction: By comparison with adults, cardiopulmonary exercise testing in children with Tetralogy of Fallot is limited, and its clinical application less validated. This study aimed to provide a comprehensive CPET profile in a child-adolescent population with repaired TOF, to explore cardiovascular mechanisms underpinning exercise intolerance and determine associations between CPET indices and clinical outcome. Methods: Seventy-four CPETs were completed in 58 child and adolescents with repaired TOF (age 13.8 ± 2.4 years). CPET parameters were corrected for age, sex and body size using Blanchard formulae. 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. Results: Cohort VO 2peak was within low-normal limits (% pred: 74.1% ± 15.4 ) with 15 patients (26%) displaying moderately-severe reduction (VO 2peak  < 65% pred). Oxygen uptake efficiency slope highly correlated with VO 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 ± 14.5 months, although there was a variable response in VO 2peak between individuals. Chronotropic response and heart rate-VO 2 slope (indicator of stroke volume) predicted oxygen consumption: VO 2peak ( p  < 0.001, R 2  = 65.78%) and workload ( p  < 0.001, R 2  = 52.32%). Adverse clinical status was associated with reduced workload (OR 0.97, p  = 0.011). V E /V CO2 slope was steeper in those that died (39.2 SD 16.7 vs. 31.45 SD 5.06, p  = 0.025). Twenty-four patients (43.8%) underwent RVOT intervention post-CPET which was associated with increased HR-VO 2 slope (OR 1.042, p  = 0.004). Conclusions: In children and adolescents with repaired TOF important reduction in cardiopulmonary functioning were apparent in 25% of patients. Exercise intolerance was related to reduced chronotropic response and deficient stroke volume increment.