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Background: Electrophysiologic characteristics, mapping strategies, and acute success rates of radiofrequency catheter ablation of atriofascicular accessory pathways are well described. However, data on long-term prognosis and predictors for freedom from arrhythmias are lacking.Objective: To report our 20-year single-center experience on ablation of atriofascicular fibers.Method: Between 1992 and 2010, 34 patients with atriofascicular accessory pathways underwent catheter ablation at our institution because of symptomatic antidromic atrioventricular reentrant tachycardias. Radiofrequency procedures were retrospectively analyzed, and patients were followed for recurrences of tachyarrhythmias. Electrocardiograms (before and after ablation and at follow-up) were analyzed for each patient.Results: Successful catheter ablation of the atriofascicular fiber was achieved in 23 (68%) patients. Mechanical block during mapping occurred in 3 (9%) patients, and in 2 of them ablation was performed at the site of mechanical block. Mere modification of conduction properties of the pathway without complete block was achieved in 5 patients (15%). Fast pathway ablation was performed in 2 (6%) of the patients ablated in the early 1990s. During follow-up of 9.3 ± 5.5 years, 24 patients (71%) remained free of tachyarrhythmias, 7 reported significant improvement, and 3 (9%) had no change in symptoms after ablation. Long-term success was identical between patients from the first (1992-1999) and second (2000-2010) decade (12 of 17 [71%] vs 12 of 17 [71%]). It was 87% in those with complete block of the atriofascicular fiber while all patients with mechanical block during mapping reported recurrences. Fast pathway ablation was complicated by complete atrioventricular block in 1 patient, who required pacemaker implantation 18 years after ablation owing to loss of conduction properties of the atriofascicular fiber over the years. On analyzing patients with preexcitation before ablation (n = 16; 47%), we found that the PR interval after ablation was significantly longer only in those without recurrence (162 ± 21 ms vs 134 ± 21 ms; P = .042). None of the other analyzed electrocardiographic parameters, including PR, QRS duration, and preexcitation, had prognostic impact.Conclusion: Acute success of complete ablation of atriofascicular pathways is associated with excellent long-term success (87%). Mere modification of conduction properties of atriofascicular fibers or ablation at the sites of mechanical block are less promising end points of ablation with high recurrence rates. Technical innovations during decades may not further improve long-term outcome in these patients. [ABSTRACT FROM AUTHOR]