Background/Objectives: In the present study, we hypothesized that cardiac surgery in pediatric patients with congenital heart disease (CHD) leads to profound endothelial glycocalyx degradation, measured as the increase in plasma syndecan-1 concentration, and that this endothelial damage is more pronounced in patients with cyanotic CHD. 

Methods: A total of 40 infants (24 with acyanotic and 16 with cyanotic CHD) were enrolled in this prospective study. A total of 39 cardiac surgeries were performed with cardiopulmonary bypass (CPB), 38 with CPB and aortic clamping, and 3 with CPB, aortic clamping, and deep hypothermic circulatory arrest. 

Results: Syndecan-1 concentrations increased significantly post-surgery compared to the baseline in both groups (cyanotic: 24.4 to 48.0 ng/mL, p < 0.0001; acyanotic: 28.8 to 59.8 ng/mL, p < 0.0001). However, there was no significant difference in syndecan-1 concentrations at any timepoint between children with cyanotic and those with acyanotic CHD. Baseline syndecan-1 showed no correlation with preoperative arterial oxygen saturation (r = 0.26, p = 0.102), hemoglobin (r = −0.3, p = 0.06), age (r = 0.15, p = 0.36), and weight (r = 0.13, p = 0.42). Of note, CPB time (r = 0.08, p = 0.63) and AC time (r = 0.03, p = 0.86) were not related to syndecan-1 concentrations at the end of surgery. 

Conclusions: Cardiac surgery leads to profound glycocalyx degradation in children with CHD detected by increased plasma syndecan-1 concentrations. Regardless of major pathophysiological differences, children with cyanotic and acyanotic CHD presented similar plasma syndecan-1 values throughout the study.