[Preliminary practice in the postoperative cardiopulmonary exercise testing for children with congenital heart...

Objective: To investigate the postoperative cardiopulmonary fitness of children with congenital heart diseases (CHD). Methods: This is a retrospective study. A total of 136 children after cardiac correction undergoing cardiopulmonary exercise test (CPET) in Shanghai Children's Medical Center from March 1 to June 30, 2021 were selected. According to the surgical procedure, the children were divided into two groups: the biventricular correction group (BV group) (n=75) and single ventricular correction group (SV group) (n=61). The BV group was divided into two subgroups: simple congenital heart disease (S-CHD) group (n=35) and complex congenital heart disease (C-CHD) group (n=40). CPET parameters, including VO₂ max, VO₂/kg max, VO₂/kg@AT, O₂/HR max, HRR, PetCO₂ max, CI, HRR at 1 min, VE/VCO₂ slope, OUES/kg and EOV, were analyzed. CPET parameters of patients underwent different procedure were compared. In the subgroup analysis, CPET parameters of patients in S-CHD group and C-CHD group were compared. The parameters of the BV group were compared with the normal value. Linear correlation analysis was used to identify the correlation between the CPET parameters. Results: A total of 136 children with CHD after surgery were enrolled. The age was (9.4±3.1) (ranged 6.2-16.0) years, and there was 84 (61.8%) male. All the children completed CPET examination safely without experiencing serious circulation abnormalities. Compared with the SV group, the VO₂/kg max ((32.6±6.9) ml·kg^-1·min^-1 vs. (23.5±5.9) ml·kg^-1·min^-1, P<0.001), O₂/HR max ((7.24±2.93) ml/beat vs. (6.35±2.17)ml/beat, P=0.030), HRR at 1 min ((32.5±13.9) beat/min vs. (26.3±12.5) beat/min, P=0.036), OUES/kg (36.9±8.8 vs. 29.7±11.8, P=0.001) were significantly higher, VE/VCO₂ slope (29.1±5.20 vs. 35.1±8.0, P<0.001) and incidence of EOV (32.0%(24/75) vs. 57.4%(31/61), P=0.027) were significantly lower in BV group. Compared with the simple CHD subgroup, VE/VCO₂ slope and the incidence of EOV were higher, VO₂/kg max, O₂/HR max, HRR at 1 min and OUES/kg were lower in the complex CHD subgroup (all P<0.05). Cardiopulmonary function parameters of the BV group were lower than the normal value. Linear correlation analysis showed that VO₂/kg@AT was strongly correlated with VO₂/kg max (r=0.86, P<0.001), VO₂/kg max was strongly correlated with OUES/kg (r=0.63, P<0.001), HRR was strongly correlated with CI (r=0.91, P<0.001), and VO₂/kg max was strongly correlated with OUES/kg (r=0.63, P<0.001). VE/VCO₂ slope was strongly correlated with PetCO₂ max (r=1.00, P<0.001). Conclusions: The exercise cardiopulmonary function of children after single ventricular correction is weaker than that of biventricular correction, and the exercise tolerance of children after biventricular correction is lower than that of normal children. Among the children after biventricular correction, the exercise tolerance of children with complex CHD is lower than that of children with simple CHD. Postoperative CPET is of important realistic significance for CHD children.