Background:
Atrial tachycardia (AT) is one of the most frequent late complications in adult patients with congenital heart defects (ACHD). Mechanism of AT depends on age and complexity of the defect. Little is known about frequency of re-intervention after catheter ablation (CA) in ACHD patients and which patients benefit most from specialized care.

Methods and Results:
Retrospective analysis of non-selected patients from one of the largest German Health Insurance Companies (BARMER GEK, approx. 9.2 million members). We analysed the frequency of CA in ACHD patients between 2012 and 2018 and independent risk factors for a combined endpoint of redo study or cardioversion after 3 years of follow-up. In addition, the impact of gender and specialized care in high volume electrophysiological ACHD centres were assessed. Overall, 485 ACHD patients (49.5% female, median age 58.4 years) underwent CA  for treatment of AT.  Congenital heart disease complexity was classified as mild in 53.2%, moderate in 33.0% and severe in 13.8%. The most common indications for CA were atrial flutter (n=143; 27.7%) and atrial fibrillation (n=134; 23.7%) with increasing incidence throughout the analysed time-interval. Overall, repeated treatment by re-ablation and/or cardioversion was performed in 36.0% (40.6% for atrial flutter and 50.7% for atrial fibrillation). Univarable analysis revealed female gender (Odds ratio [OR] 1.76; p=0.09), moderate or severe complexity of congenital heart defects (OR 1.57; p=0.02), arterial hypertension (OR 1.91; p=0.01), chronic renal disease (OR 1.75; p=0.02) and use of antiarrhythmic drugs at time of CA (OR 1.57; p<0.001) as risk factors predicting recurrence of AT. On multivariable analysis, moderate or severe defect complexity (OR 1.76; p<0.05) and atrial fibrillation (OR 2.03; p<0.05) emerged as independent risk factors. Re-intervention was observed significantly more often if the primary procedure was performed in a non-specialized center in patients with moderate/severe complexity defects (p<0.05). Female patients treated at non-specialist ACHD centers had a 1.5-fold increased risk of recurrent arrhythmia (p=0.015) compared to those treated at a specialist center. For male patients, there was no significant benefit of specialized care (p=0.954).

Conclusion:
Catheter ablation is increasingly performed particularly for atrial flutter and atrial fibrillation in ACHD patients. Rates of recurrence of atrial tachycardia requiring re-do catheter ablation or cardioversion occurred in 1/3 of patients and significantly higher in female patients and patients with moderate or severe complexity of congenital heart disease. In particular, ACHD patients with moderate and severe defect complexity as well as female patients appear to benefit from upfront referral to specialist ACHD centers for interventional arrhythmia treatment.