A Direct Midseptal Approach to Slow Atrioventricular Nodal Pathway Ablation

OBJECTIVES: The purpose of this study was to describe a midseptal approach to selective slow pathway ablation for the treatment of AV nodal reentrant tachycardia (AVNRT). In addition, predictors of success and recurrence were evaluated. METHODS: Selective ablation of the slow AV nodal pathway utilizing radiofrequency (RF) energy and a midseptal approach was attempted in 60 consecutive patients with inducible AVNRT. RESULTS: Successful slow pathway ablation or modification was achieved in 59 of 60 patients (98%) during a single procedure. One patient developed inadvertent complete AV block (1.6%). A mean of 2.7 +/- 1.4 RF applications were required with mean total procedure, ablation, and fluoroscopic times of 191 +/- 6.3, 22.8 +/- 2.3, and 28.2 +/- 1.8 minutes, respectively. The PR and AH intervals, as well as the antegrade and retrograde AV node block cycle length, were unchanged. However, the fast pathway effective refractory period was significantly shortened following ablation (354 +/- 13 msec vs 298 +/- 12 msec; P = 0.008). The A/V ratio at successful ablation sites were no different than those at unsuccessful sites (0.22 +/- 0.04 vs 0.23 +/- 0.03). Junctional tachycardia was observed during all successful and 60 of 122 (49%) unsuccessful RF applications (P < or = 0.0001). A residual AV nodal reentrant echo was present in 15 of 59 (25%) patients. During a mean follow-up of 20.1 +/- 0.6 months (11.5-28 months) there were four recurrences (5%), 4 of 15 (27%) in patients with and none of 44 patients without residual slow pathway conduction (P = 0.002). CONCLUSIONS: A direct midseptal approach to selective ablation of the slow pathway is a safe, efficacious, and efficient technique. Junctional tachycardia during RF energy application was a highly sensitive but not specific predictor of success and residual slow pathway conduction was associated with a high rate of recurrence.