The V̇e/V̇co 2 slope: a useful tool to evaluate the physiological status of children with congenital heart disease.

Cardiopulmonary exercise test (CPET) is becoming a key examination to assess physical capacity and disease severity in pediatric cardiology. The V̇e/V̇co2 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 congenital heart disease (CHD). Nevertheless, the use of the V̇e/V̇co2 slope in children remains limited in the absence of reference values and clearly identified clinical determinants. This study aimed to compare the V̇e/V̇co2 slope in a pediatric cohort with CHD to that of age- and gender-adjusted healthy controls. We also intended to identify the clinical and CPET variables associated with V̇e/V̇co2 slope in this population. This cross-sectional study was carried out between November 2010 and September 2015 in two tertiary care pediatric cardiology reference centers. A total of 700 children were enrolled (399 CHD and 301 healthy controls). The mean V̇e/V̇co2 slope was significantly higher in the CHD subjects than in healthy subjects (31.6 ± 4.8 vs. 29.3 ± 4.8; P < 0.001). The V̇e/V̇co2 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, V̇e/V̇co2 slope increase was associated with body mass index, the presence of a RVOT obstacle, the number of cardiac catheter procedures, as well as low age, forced vital capacity, tidal volume, and [Formula: see text]. Increased V̇e/V̇co2 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 V̇e/V̇co2 slope. NEW & NOTEWORTHY Using V̇e/V̇co2 slope is useful for children with congenital heart disease. V̇e/V̇co2 slope is sensitive to pulmonary blood flow maldistribution during exercise, this concerns congenital heart disease with pulmonary regurgitation, tricuspid regurgitation, right ventricular hypertension, and right ventricle outflow tract obstacle. V̇e/V̇co2 slope is a good parameter to follow single ventricles and right heart residual lesions (tetralogy of Fallot; pulmonary atresia; truncus arteriosus…).