Cardiorespiratory Fitness in Children with Surgically Corrected Congenital Heart Disease: Exercise Testing Profiles...

Children with surgically corrected congenital heart disease (CHD) often exhibit reduced cardiorespiratory fitness, reflected by impaired maximal oxygen uptake (V̇O₂max). Although exercise limitation is multifactorial, the relative contributions of cardiovascular, ventilatory, and gas exchange abnormalities remain unclear. This study aims to characterize exercise impairments in children with CHD using cardiopulmonary exercise testing (CPET) and cardiac imaging.

Children with surgically corrected biventricular CHD were prospectively recruited. CPET parameters were expressed as percentages of predicted (%pred) for age and sex, and biventricular function was evaluated by echocardiography and cardiac magnetic resonance imaging. Regression analyses examined associations between V̇O₂max, exercise parameters, and imaging-derived cardiac function.

In total, 100 consecutive children with CHD were included. V̇O₂max (73.9±14.2%pred) and anaerobic threshold (V̇O₂AT; 74.7±16.6%pred) showed the greatest deviation from normal. CPET demonstrated cardiovascular (oxygen pulse [O₂pulse], maximal heart rate [HRmax]), ventilatory (maximal ventilation), and gas exchange impairments (ventilatory inefficiency). Imaging showed reduced systolic function, particularly left ventricular global longitudinal strain (GLS; -17.5±2.5%) and tricuspid annular plane systolic excursion (TAPSE; 13.1mm, IQR 11.0-15.4). V̇O₂AT, HRmax, GLS, and TAPSE independently predicted V̇O₂max (R²=68.1%; p<0.001), with V̇O₂AT strongest predictor.

Reduced cardiorespiratory fitness in children with surgically corrected CHD encompasses impaired cardiovascular, ventilatory, and gas exchange responses to exercise. Early anaerobic threshold, chronotropic incompetence, and subclinical systolic dysfunction on imaging are associated with reduced maximal exercise capacity, indicating contributions from both cardiac dysfunction and deconditioning. Integrating imaging with CPET may improve differentiation between cardiac and non-cardiac contributors to exercise limitation.