The cardiovascular response to exercise in children with congenital heart diseases

Background: Patients with congenital heart disease (CHD), although most of heart defects can be successfully corrected, have reduced cardiovascular fitness and low quality of life. Thus, regular follow-up evaluations are needed, including cardiopulmonary exercise testing (CPET) and echocardiography. While the behaviour of cardiorespiratory and gas exchange indices is well studied during maximal exercise testing, much less is known regarding the recovery. We analysed the recovery phase after CPET, particularly regarding the respiratory exchange ratio (RER) overshoot phenomenon, in a population of patients with 4 different kinds of CHD. Material and methods: 103 patients with CHD and 28 healthy controls were enrolled in this cross-sectional retrospective trial. Patients were evaluated with CPET by assessing cardiorespiratory fitness and efficiency as well as the RER overshoot during recovery after an incremental maximal exercise test. Results: When compared to healthy subjects, patients with CHD showed a reduced cardiorespiratory fitness and efficiency. RER overshoot was also significantly attenuated in the CHD group, even though RER at peak exercise was comparable between the two groups. Correlations between the recovery parameters and other common CPET measures were performed. RER max and RER mag showed significant correlations with most of the indices of cardiorespiratory efficiency. In fact, both RER max and RER mag were correlated to VO₂ peak pro kg and OUES. A negative correlation between RER mag and HR/VO₂ slope, a parameter of cardiovascular efficiency, was also displayed. No correlations were found between the RER overshoot phenomenon and left ventricular function. Conclusion: This is the first study evaluating the RER overshoot in the recovery phase in a population of young patients with CHD. The attenuation of this phenomenon in this population, as well as its relationship with cardiorespiratory fitness, may open new approaches in the functional evaluation of patients with CHD. Future studies assessing prospectively the recovery phase from maximal exercise testing may further improve the diagnostic value of CPET in subjects with CHD.