The VE/VCO2 slope: a useful tool to evaluate the physiological status of children with congenital heart disease.

Introduction Cardio-pulmonary exercise test (CPET) is becoming a key examination to assess physical capacity and disease severity in paediatric cardiology. The VE/VCO2 slope has been increasingly used as a surrogate marker for morbidity and mortality in adult heart failure, pulmonary arterial hypertension and for adult patients with CHD. Nevertheless, the use of the VE/VCO2 slope in children remains limited in the absence of reference values and clearly identified clinical determinants. This study aimed to compare the VE/VCO2 slope in a paediatric cohort with CHD to that of age- and gender-adjustedhealthy controls. We also intended to identify the clinical and CPET variables associated with VE/VCO2 slope in this population. Methods This cross-sectional study was carried out between November 2010 and September 2015 in two tertiary care paediatric cardiology reference centres. Results A total of 700 children were enrolled (399 CHD and 301 healthy controls). The mean VE/VCO2 slope was significantly higher in CHD than in healthy subjects (31.6±4.8 vs. 29.3±4.8; P<0.001). The VE/VCO2 slope was higher in children with significant pulmonary regurgitation, tricuspid regurgitation, right ventricular hypertension and right ventricle outflow tract (RVOT) obstacle. In the CHD group, VE/VCO2 slope increase was associated with BMI, the presence of a RVOT obstacle, the number of cardiac catheter procedures, as well as low age, FVC, tidal volume, and PetCO2. Conclusion Increased VE/VCO2 slope was predominantly in children with single ventricle and/or residual right heart abnormalities suggesting that maldistribution of pulmonary blood flow during exercise is an important CHD-unique determinant of VE/VCO2 slope.