The V̇e/V̇co2 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/V̇co 2 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/V̇co 2 slope in children remains limited in the absence of reference values and clearly identified clinical determinants. This study aimed to compare the V̇e/V̇co 2 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/V̇co 2 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/V̇co 2 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/V̇co 2 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/V̇co 2 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/V̇co 2 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/V̇co 2 slope. NEW & NOTEWORTHY Using V̇e/V̇co 2 slope is useful for children with congenital heart disease. V̇e/V̇co 2 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/V̇co 2 slope is a good parameter to follow single ventricles and right heart residual lesions (tetralogy of Fallot; pulmonary atresia; truncus arteriosus…).