Determination of Repetitive Slow Pathway Conduction for Evaluation of the Efficacy of Radiofrequency Ablation in AVNRT

LUKAC, P., et al.: Determination of Repetitive Slow Pathway Conduction for Evaluation of the Efficacy of Radiofrequency Ablation in AVNRT. Aims: To determine whether the loss of repetitive slow pathway conduction identifies a successful radiofrequency ablation of atrioventricular nodal reentry tachycardia (AVNRT). Methods and results: Thirty nine consecutive patients undergoing ablation of AVNRT using the slow pathway approach were included. At baseline and after each radiofrequency application with an episode of junctional rhythm, repetitive slow pathway conduction was assessed as follows: Effective refractory period of the fast pathway was determined. The coupling interval of the first atrial extrastimulus (A2) was set at 30 ms below the effective refractory period of the fast pathway to ensure its conduction via the slow pathway. The second atrial extrastimulus (A3) was introduced at progressively longer coupling intervals starting from 200 ms until: (1) it propagated to the His bundle or (2) an anterogradely blocked AV nodal echo of A2 appeared before a conducted A3 depolarized the atrium in the His bundle electrogram. The response was termed repetitive slow pathway conduction if A3 was conducted with an AH > 200 ms . Application was considered successful if no AVNRT could be induced. Repetitive slow pathway conduction was present after 1 of 39 successful and after 34 of 40 ineffective applications (P < 0.0001) . Repetitive slow pathway conduction identified a successful application with 97% sensitivity, 86% specificity, 86% positive predictive value, and 97% negative predictive value. Conclusion: The presence of repetitive slow pathway conduction identifies an unsuccessful application with a clinically meaningful negative predictive value. (PACE 2003; 26[Pt. I]:827–835)