We aimed to compare the cardiopulmonary fitness of children with congenital heart diseases (CHD) to that of age- and gender-adjusted controls. We also intended to identify clinical characteristics associated with maximum oxygen uptake (VO2_max) in this population.

We included in a cross-sectional multicentre study a total of 798 children (496 CHD and 302 controls) who underwent a complete cardiopulmonary exercise test (CPET). The association of clinical characteristics with VO2_max was studied using a multivariate analysis. The study was approved by the South Mediterranean IV Ethics Committee (2009-A00423-54) and registered on ClinicalTrials.gov (NCT01202916). Informed consent was obtained from all parents.

Mean VO2_max in the CHD group and control represented 93±20% and 107±17% of predicted values, respectively. VO2_max was significantly lower in the CHD group, overall (37.8±0.3 vs. 42.6±0.4mL/kg/min, P<0.0001) and for each group (P<0.05) (Table 1). The mean VO2_max decline per year was significantly higher in CHD than in the controls overall (−0.84±0.10 vs −0.19±0.14mL/kg/min/year, P<0.01), for males (−0.72±0.14 vs. 0.11±0.19mL/kg/min/year, P<0.01), and for females (−1.00±0.13 vs. −0.55±0.21mL/kg/min/year, P=0.05) (Fig. 1). VO2_max was associated with body mass index, ventilatory anaerobic threshold, female gender, restrictive ventilatory disorder, right ventricle systolic hypertension, tricuspid regurgitation, the number of cardiac catheter or surgery procedures, and the presence of a genetic anomaly.

This comparative CPET study provided, for the first time, relevant values of VO2_max and their clinical determinants in the largest reported cohort of CHD children compared to a control group. Although the magnitude of the difference was not large, VO2_max among children with CHD was significantly lower than in normal children. We suggest performing CPET in routine follow-up of these patients.