Slow-Pathway Ablation for Atrioventricular Nodal Re-Entrant Tachycardia with No Risk of Atrioventricular Block

Background: Slow-pathway ablation or modification eliminates typical atrioventricular nodal re-entrant tachycardia (AVNRT) but with a 1% risk of AV block. We report our experience from a series of consecutive patients with typical AVNRT who were ablated in our unit. Methods: Consecutive patients (n=227), aged 22 to 56 years, 172 women, with slow-fast AVNRT underwent slow-pathway ablation. Mapping was restricted to the inferior part of the triangle of Koch, at the right or left septum, below the ostium of the coronary sinus, and was aimed at recording multicomponent, lowamplitude potentials. The endpoints of ablation were induction of a retrogradely conducted junctional rhythm, and non-inducibility of AVNRT on isoprenaline. Results: All procedures were successful, with no change in the AH interval. Right-sided ablation was successful in 223 (98.2%) of cases. In four patients (1.8%) left-sided ablation was necessary. Procedure and fluoroscopy times were 70.1 ± 21.4 and 11.2 ± 5.8 min, respectively. In total, 4.5 ± 1.2 radiofrequency lesions per patient were given. During a follow-up period of one to three years, three patients (1.3%) had AVNRT recurrence. All of them had residual dual pathway physiology following ablation, while only 19.6% of patients without AVNRT had residual dual AV nodal conduction (p<0.001). No patient developed AV conduction disturbances. Conclusions: Ablation at the inferior part of the triangle of Koch with the protocol described offers a high success rate, with no risk of AV block, in patients with typical AVNRT. Residual dual AV nodal conduction carries an increased risk of AVNRT recurrence.