Impact of the local atrial electrogram in AV nodal reentrant tachycardia: ablation versus modification of the slow pathway.

INTRODUCTION: The purpose of this study was to determine the predictors of successful ablation versus modification sites of the slow pathway in patients with AV nodal reentrant tachycardia. Complete elimination of slow pathway conduction ("ablation") is considered to be an appropriate endpoint during radiofrequency (RF) current delivery, whereas the persistence of residual slow pathway conduction with or without single echo beats ("modification") may be indicative of tachycardia recurrence. METHODS AND
RESULTS: Of 131 patients, 71 consecutive patients were followed for 15.1 +/- 7.6 months. After elimination of inducible AV nodal reentrant tachycardia in all patients, residual slow pathway conduction (modification) persisted in 38 patients, whereas complete elimination of slow pathway conduction (ablation) was documented in 33 patients. Including electrophysiologic study after 5 to 7 days and after 3 to 6 months, 6 (8.4%) patients had recurrences: 5 with residual slow pathway conduction after the procedure and 1 with complete elimination of slow pathway conduction (P < 0.05). As compared with modulated sites, ablation sites of the slow pathway were characterized as follows: (1) duration of the local atrial electrogram (AEGM) (66.7 +/- 10.2 vs 54.1 +/- 12.6 msec, P < 0.01); (2) interval from the end of the AEGM to onset of His-bundle deflection (4.4 +/- 8.2 vs 16.1 +/- 9.3 msec, P < 0.01); and (3) number of peaks of the AEGM as an indicator of fractionation (4.1 +/- 0.7 vs 3.0 +/- 0.8, P < 0.01). The rate of junctional tachycardias (103.4 +/- 12.1 vs 102.1 +/- 16.9 per min), the AV ratio (0.4 +/- 0.5 vs 0.5 +/- 0.5), the number of RF current deliveries (4.1 +/- 4.4 vs 4.5 +/- 4.4), the duration of the procedure (124.1 +/- 45.3 vs 125.6 +/- 42.3 min), and the fluoroscopy time (15.5 +/- 10.8 vs 16.6 +/- 9.6 min) as well as power and total energy of RF current deliveries and the anatomically calculated catheter position at the successful site were not statistically different. A subset analysis in patients who received only a single RF application showed the same results for both groups. Patients without recurrence (n = 65) were found to have longer duration of the AEGM (61.9 +/- 14.6 msec) and a shorter interval from the end of AEGM to the onset of His-bundle deflection (10.1 +/- 12.2 msec) than patients with recurrence (n = 6) (47.5 +/- 7.5 msec and 20.8 +/- 12.8 msec, respectively).
CONCLUSION: Complete ablation of the slow pathway resulted in a lower recurrence rate. The complete ablation approach is feasible using precisely analyzed local AEGMs to guide RF current in AV nodal reentrant tachycardia in a short procedure time.