Immediate and long-term results of catheter ablation of atrioventricular accessory pathways (AP) are presented. Method: One hundred and seventy-one patients aged 41.8 ± 14.4 years underwent catheter ablation of 179 AP. Right and left AP occurred simultaneously in 3 patients; thus 65 ablation procedures for 57 rights AP in 57 patients were compared with 125 ablation procedures for 122 left AP in 117 patients. Results: Including repeated procedures ablation was successful in 116 (99 %) patients with left AP and in 57 (100 %) patients with right AP. First catheter ablation failed in 4 (7 %) patients with right AP and in 4 (3.4 %) patients with left AP (p = NS). Two of these patients with left AP and all 4 pts with right AP had successful reablation. AP conduction recurred after successful ablation in 7 (12.3 %) patients with right AP and in u 5 (4.1 %) patients with left AP (p = 0.1). Three patients with right AP did not undergo another ablation, other 9 patients with AP recurrence had successful reablation. Procedure time during left AP ablation was shorter (159.6 ± 70.7 vs. 183.4 ± 75.6 min.; p = 0.02) and number of RF current deliveries was lower during left AP ablation (9.3 ± 8.5 vs. 13.3 ± 11.8; p = 0.008) compared to right AP ablation. Fluoroscopy time during left AP ablation (22.4 ± 19.1 min.) did not significantly differ from that during right AP ablation (20.9 ± 17.1 min.). Concealed AP was present in 13 (22.8 %) patients with right AP and in 59 (48.4 %) patients with left AP (p = 0.002). Anatomico-functional variant of AP occurred in 5 (8.8 %) patients with right AP and in 4 (3.3 %) patients with left AP (p = NS). Atrial fibrillation complicated ablation procedure in 9 (15.8 %) patients with right AP and in 7 (5.7 %) patients with left AP (p = NS). During 30.3 ± 17 (2 - 60) months follow-up period tachyarrhythmia associated with the presence of an AP occurred in 3 patients with right AP and in 1 patient with unsuccessful ablation of left AP. None of these patients underwent repeated ablation. Conclusion: Successful ablation of AP can be achieved successfully in 100 %. Catheter ablation of right AP is generally more difficult and primary ablation failure and AP conduction recurrence is nonsignificantly more often. Irregularity of the tricuspid annulus, instability of the ablation catheter, presence of the conduction system, higher occurrence of anatomico-functional AP variants and sustained atrial fibrillation during the ablation procedure represent the main causes of this finding.

        Key words: Atrioventricular accessory pathways - Catheter ablation