Abstract
Aims Overweight and obesity in children with congenital heart disease (CHD) represent an alarming cardiovascular risk. Promotion of physical activity and cardiac rehabilitation in this population requires assessing the level of aerobic fitness (VO2max) by a cardiopulmonary exercise test (CPET). Nevertheless, the interpretation of CPET in overweight/obese children with CHD remains challenging as VO2max is affected by both the cardiac condition and the body mass index (BMI). The new paediatric VO2max Z-score reference equations, based on a logarithmic function of VO2max, height and BMI, were applied to overweight/obese children with a CHD, and compared to overweight/obese children without any other chronic condition. Methods and Results In this cross-sectional controlled study, 344 children with a BMI>85th percentile underwent a CPET (54% boys; mean age 11.5±3.1 years; 100 CHD; 244 controls). Using the VO2max Z-score equations, aerobic fitness was significantly lower in obese/overweight CHD children than in matched obese/overweight control children (-0.43±1.27 vs. -0.01±1.09; p=0.02, respectively) and the proportion of children with impaired aerobic fitness was significantly more important in obese/overweight CHD children than in matched controls (17% vs.6%, p=0.02, respectively). The paediatric VO2max Z-score reference equations also identified specific complex CHD at risk of aerobic fitness impairment (univentricular heart, right outflow tract anomalies). Using Cooper’s weight and height-based linear equations, similar matched-comparisons analyses found no significant group differences. Conclusions As opposed to the existing linear models, the new paediatric VO2max Z-score equations can discriminate the aerobic fitness of obese/overweight children with CHD from that of obese/overweight children without any chronic disease.