LONG-TERM RESULTS OF FAST PATHWAY ABLATION IN ATRIOVENTRICULAR NODAL REENTRY TACHYCARDIA USING A MODIFIED TECHNIQUE

Objective-To assess immediate and long term success of ''fast'' pathwa y catheter ablation with graded use of radiofrequency energy in patien ts with classic atrioventricular nodal reentrant tachycardia (AVNRT) a nd evaluate clinical, procedure related, and electrophysiological feat ures affecting long term results. Design-31 consecutive patients with classic AVNRT at electrophysiological study, who were candidates for r adiofrequency ablation. Patients were followed for an average of 24 mo nths after ablation. Setting-Ah studies and ablations were performed i n an electrophysiological laboratory under fluoroscopic guidance using standard electrophysiological techniques. Intervention-Radiofrequency application was performed at the site of proximal His bundle electrog ram with A:V ratio of > 1. It was started at 10 W with increment of 5 W to a maximum of 25 W at 60 s. With the onset of junctional rhythm, a trial pacing was begun in order to monitor the PR interval. Applicatio n was terminated prematurely with a nonconducted P wave, continued pro longation of the PR interval beyond 50% of the baseline, or a threefol d rise in impedance. Results-Successful ablation was possible in 30/31 patients (97%) with an average of seven applications (range 1-10). It was associated with significant prolongation of PR interval (P < 0.00 1) and AV Wenckebach cycle length (P 0.01). Ventriculo-atrial conducti on was abolished in 24/30 patients (82%) with successful ablation. Two patients developed transient complete heart block (3 and 12 min) and one persistent right branch block. Four patients had late recurrence. Presence of ventriculo-atrial block was the only electrophysiological index predictive of long term success (P = 0.01). Conclusions-Graded u se of radiofrequency energy and atrial pacing to monitor PR interval d ecreases the risk of atrioventricular block in patients undergoing fas t pathway ablation for AVNRT. Ventriculo-atrial block is predictive of long term success and should be a preferred end point for fast pathwa y ablation.