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

Abstract

Cardio-pulmonary exercise test (CPET) is becoming a key examination to assess physical capacity and disease severity in paediatric cardiology. The VE/VCO 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 CHD. Nevertheless, the use of the VE/VCO 2 slope in children remains limited in the absence of reference values and clearly identified clinical determinants. This study aimed to compare the VE/VCO 2 slope in a paediatric cohort with CHD to that of age- and gender-adjusted healthy controls. We also intended to identify the clinical and CPET variables associated with VE/VCO 2 slope in this population. This cross-sectional study was carried out between November 2010 and September 2015 in two tertiary care paediatric cardiology reference centres. A total of 700 children were enrolled (399 CHD and 301 healthy controls). The mean VE/VCO 2 slope was significantly higher in CHD than in controls (31.6 ± 4.8 vs. 29.3 ± 4.8; P < 0.001). When considering CHD sub-groups, the VE/VCO 2 slope was impaired in single ventricle, complex anomalies of ventriculo-arterial connections, anomalies of the atrioventricular junctions and valves. The VE/VCO 2 slope according to the CHD physiological status was illustrated in the Fig. 1 , it 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/VCO 2 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 ( Fig. 1 ). Increased VE/VCO 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 VE/VCO 2 slope.