Risk Factors for low Cardiac Output Syndrome in Children less than 6 years old Undergoing Ventricular Septal Defect Closure: a Retrospective Cohort Study.

Low cardiac output syndrome (LCOS) is a critical complication following ventricular septal defect (VSD) closure in children. Despite its clinical importance, the risk factors specific to LCOS in VSD cases are underexplored. This study investigated the risk factors and clinical outcomes associated with LCOS in children aged < 6 years who underwent VSD closure.We conducted a retrospective cohort study and analyzed 266 patients who underwent VSD closure between January 2014 and December 2023. Patients with other complex congenital heart anomalies requiring surgical repair, except for atrial septal defects, patent ductus arteriosus, mild valve stenosis, or regurgitation, were excluded. LCOS was diagnosed based on hemodynamic and metabolic criteria. The LCOS observation window included both the intraoperative and early postoperative phases. Univariate and multivariate logistic regression analyses were performed to identify risk factors for LCOS. Among the 266 patients, 46 (17.3%) developed LCOS. Independent risk factors for LCOS included age < 3 months (adjusted odds ratio [aOR]: 4.72, 95% confidence interval [CI]: 2.20-10.2, p < 0.001), preoperative pulmonary hypertension (defined using echocardiography as the qualitative presence of interventricular septal flattening) (aOR: 2.17, 95% CI: 1.03-4.58, p < 0.05), and cardiopulmonary bypass duration > 120 min (aOR, 2.92; 95% CI: 1.41-6.07, p < 0.01). LCOS was associated with prolonged mechanical ventilation, intensive care unit stay, and hospital stay but did not significantly affect mortality. This study identified risk factors for LCOS that contribute to safe intraoperative and postoperative management in pediatric patients undergoing VSD closure.