Clinical outcomes of catheter ablation for atrial arrhythmias in adult congenital heart disease patients

Introduction Adult congenital heart disease (ACHD) patients frequently develop atrial tachyarrhythmias (AT) due to abnormal cardiac anatomy, surgical scarring and residual hemodynamic defects. Although radiofrequency catheter ablation (RFCA) is an effective treatment, yet recurrence rate remains significant. The study aimed to identify predictors of arrhythmic recurrence after RFCA in ACHD patients. Methods We retrospectively analyzed ACHD patients undergoing RFCA for AT between 2007 to 2025 at our Institution. Clinical, electrocardiographic, procedural, therapeutic and imaging (echocardiography and/or cardiac magnetic resonance-CMR) parameters were evaluated as potential predictors of AT recurrences. These were defined as any documented AT during follow-up after the first procedure. Follow up time was censored at the first post ablation AT, subsequent surgical/percutaneous intervention, last clinic visit or last available follow-up data. Results Eighty ACHD patients (mean age 45.6 ± 16.3, 50% female) underwent 105 RFCA procedure for AT. Congenital defects were of mild (21.3%), moderate (75.0%, mainly repaired tetralogy of Fallot), or severe (3.8%) complexity. Underlying defects included atrial septal defect/anomalous pulmonary vein return (21.3%), atrioventricular canal defect (8.8%), Fallot/ventricular septal defect/pulmonary stenosis (61.3%), Fontan palliation (2.5%), and others (6.3%). The first documented AT was macroreentrant atrial tachycardia (MRAT) observed in 56 patients (70%, 32 peritricuspidal, 17 scar-related, 7 both), followed by focal atrial tachycardia (FAT) in 10 (13%), atrio-ventricular reentrant tachycardia in 7 (9%), and atrial fibrillation in 6 (8%). During a median follow up time of 12.3 months (IQ 2.9-27.2), 23 (29%) patients presented a recurrence of AT. Twenty-one patients (26%) required at least one RFCA redo, in 16 cases (76%) for recurrence of the same AT. Patients with AT recurrence were older (52.5 ± 14.0 vs 42.5 ± 16.0 years, p=0,01), had lower ejection fraction (EF) at the CMR (52.0 ± 8.2% vs 58.7 ± 6.7%, p=0,002), and more frequently showed dilatation of the left atrium (draining pulmonary circulation) (85% vs 30%, p<0,001). The defect complexity or the arrhythmia mechanism did not influence the recurrence rate. Kaplan Meier analysis confirmed a significantly lower arrhythmia-free survival in patients with left atrial dilatation ( χ2 = 14.6, p<0.001). Conclusions RFCA is an effective strategy in ACHD patients, yet recurrence remains common. Despite most patients presenting with right-sided lesions, left atrial dilatation and systemic ventricular dysfunction emerged as independent predictors of recurrence, while neither defect complexity nor arrhythmia mechanism influenced outcomes. These findings highlight the importance of comprehensive pre-procedural morpho-functional assessment and support a personalized approach to optimize long-term results of RFCA in ACHD.