Slow/fast atrioventricular nodal reentrant tachycardia catheter ablation guided by atrial resetting: The new insight.

Background: Atrial resetting can be used to discern the anterograde pathway in slow/fast atrioventricular nodal reentrant tachycardia (AVNRT).

Objective: We aimed to assess the prevalence of right inferior extension (RIE) and left extension (LE) and the potential impact on the ablation approach.

Methods: During the electrophysiologic study of patients with slow/fast AVNRT, a decremental supraventricular extrastimulus was delivered within the vulnerability window of the tachycardia cycle at 2 distinct sites: the inferoparaseptal area of the Koch triangle (near the RIE) and the proximal few centimeters of the coronary sinus (near the LE). The site with the latest extrastimulus (longest H-Stim) that could reset the tachycardia was defined as the site of the anterograde slow pathway.

Results: Thirty-six patients were enrolled during a 1-year period. Resetting could not be performed in 10 patients (28%) because of nonsustained tachycardia and in 1 patient because of failed atrial capture. Of the remaining 25 patients (69%), 18 (72%) had the best resetting from the RIE, 5 (20%) had the best resetting from the LE, and 2 (8%) had 2 alternating AVNRTs. The mean H-Stim value in the RIE position was longer when resetting favored RIE compared with LE (46 ± 13 ms vs 16 ± 21 ms; P < .001); a similar pattern was observed in the LE position (59 ± 20 ms vs 15 ± 18 ms; P < .001). Ablation of the left inferior extension could be performed from the right side but significantly closer to the His bundle compared with the RIE (9.6 ± 3 mm vs 18.5 ± 4 mm; P < .001).

Conclusion: LE AVNRT is a common finding and can be ablated by a right-sided approach in most cases.