Overweight/obesity is a major public health problem in the general paediatric population with a prevalence of 21% in Europe. This prevalence is more important in children with chronic diseases [including congenital heart disease (CHD)]. We know that children with CHD have lower aerobic fitness than “healthy” children. Overweight/obesity also has a negative impact on this aerobic fitness. Overweight/Obese children with CHD should have lower aerobic fitness than healthy obese children, but until now there have been no reference values to assess aerobic fitness in this overweight subpopulation. Our team recently provided paediatric reference values with adapted Z scores for extreme weights. The main objective of this study is to assess whether these new reference values discriminate healthy obese children from obese children with CHD compared to the usual reference values of Cooper et al.

This cross-sectional study was carried out between November 2010 and November 2020 in two tertiary care paediatric cardiology reference centres and included both “healthy” and CHD children with BMI>85th percentiles.

In total, 344 children were included (185 boys), 244 controls and 100 CHD. Using the usual standards (Cooper et al.), no significant difference in VO2_max between CHD and control groups was found (76±18% vs. 77±21%; P=0.7). According to our new reference values, a significant difference was found for the Z-score of VO2_max between the CHD and control groups (−0.46±1.31 vs. −0.10±1.03; P=0.006). The CHD subgroups in according with ACC-CHD classification found a lowest mean VO2_max Z-score in the single ventricle malformations, anomalies of the atrioventricular junctions and complex anomalies of the right ventricle outflow tract.

This study reveals the benefit of these new references values adapted to extreme weights by discriminating a pathological group (CHD) from a control group.