Background: Bachmann's bundle (BB) may potentially play a role in the earlier onset and faster progression of atrial fibrillation in adult patients with congenital heart disease (CHD). It is unknown whether electrophysiological alterations already exist at BB in pediatric patients with CHD and whether they are related to aging. Objective: This study aimed to investigate BB electrophysiology in pediatric patients with CHD and assess the impact of age on BB electrophysiology. Methods: BB mapping was conducted in 55 patients (0.2–17.5 years). Activation patterns, potential voltages, low-voltage areas (LVAs), potential morphology, and conduction disorders of BB were analyzed and correlated with age. Results: Right-to-left activation across BB occurred in 96.4% of patients. Potential voltage was on average 7.2 ± 3.0 mV, and LVAs occurred in 85.4% of patients. Median local conduction velocity was 96.6 (72.9–121.0) cm/s, and conduction block occurred in 56.4% of patients. Most potentials were single and short-double potentials; long-double and fractionated potentials were recorded in 49.1% and 72.7% of patients, respectively. Age was weakly correlated with potential voltages (r = 0.312, P = .020) and moderately with local conduction velocity (r = 0.439, P < .001), but not with potential morphology or conduction block. Conclusion: In pediatric patients with CHD, BB already contains a considerable amount of conduction disorders, LVAs, and potentials with complex morphology. The prevalence of these early electrophysiological alterations is not age related and does not differ among the right, left, and middle parts of BB.

Arrhythmias significantly contribute to morbidity and mortality in patients with congenital heart disease (CHD). While postoperative factors predisposing to arrhythmias are well-established, early electrophysiological alterations in pediatric CHD remain poorly understood. This review summarizes current knowledge on postnatal cardiac maturation, conduction-system development, and electrophysiological abnormalities in pediatric patients with and without CHD. Importantly, arrhythmia prevalence, mechanisms, and clinical relevance are systematically discussed across three pediatric groups, including healthy children and patients with unrepaired and repaired CHD. Understanding developmental arrhythmogenic mechanisms may facilitate early risk stratification, guide clinical management decisions, and improve long-term outcomes for pediatric patients with CHD. This review discusses the complex interplay between cardiac maturation, congenital defects, and arrhythmogenesis. It also outlines future directions that include noninvasive monitoring, selective intraoperative mapping, animal model studies, and standardized data collection to improve early risk stratification and long-term outcomes in children with CHD.