Early post-operative arrhythmia is a frequent complication after paediatric cardiac surgery. Although usually transient, it contributes to considerable morbidity and may increase mortality. This study aimed to determine the incidence, predictors, and outcomes of early post-operative arrhythmia following paediatric open-heart surgery.

A single-centre retrospective cohort study was conducted on paediatric patients who underwent open-heart surgery for congenital or acquired heart diseases between January 2022 and December 2024. Pre-operative, intraoperative, and post-operative parameters were analysed to identify independent predictors using multivariate logistic regression.

Of 2,096 patients analysed, 220 (10.5%) developed early post-operative arrhythmias, mainly tachyarrhythmias. The most common were complete heart block (3.2%), accelerated junctional rhythm (2.8%), and junctional ectopic tachycardia (1.9%). Tetralogy of Fallot repair had the highest incidence (20.2%). Independent predictors included prolonged cardiopulmonary bypass (OR 1.005, 95% CI 1.002–1.009, p = 0.002), extended aortic cross-clamp time (OR 1.006, 95% CI 1.001–1.011, p = 0.011), and prolonged inotropic support (OR 1.035, 95% CI 1.009–1.063, p = 0.009). Serum magnesium ≥ 1.0 mmol/L was identified as a protective factor. Arrhythmia was associated with longer mechanical ventilation (median 4 vs. 2 days), ICU stay (8 vs. 4 days), and hospitalisation (20 vs. 12 days; all p < 0.001). Mortality was higher but not statistically significant (5.9% vs. 3.6%, p = 0.087).

Post-operative arrhythmia occurred in 10.5% of paediatric cardiac surgeries, most frequently after Tetralogy of Fallot repair. Prolonged bypass, aortic cross-clamp times, hypomagnesemia, and high inotropic support were independent risk factors associated with increased morbidity.