Demonstration of anatomical reentrant tachycardia circuit in verapamil-sensitive atrial tachycardia originating from the vicinity of the atrioventricular node

Background The anatomical location of the reentry circuit in verapamil-sensitive atrial tachycardia originating from the vicinity of atrioventricular node (V-AT) is not well clarified. Objective To define the reentry circuit of V-AT. Methods In 17 patients with V-AT, rapid atrial pacing at a rate 5 beats/min faster than the tachycardia rate was delivered from multiple sites of the right atrium (RA) during tachycardia to define the direction of the proximity of the slow conduction area of the reentry circuit. After identification of manifest entrainment and orthodromic capture of the earliest atrial activation site (EAAS), radiofrequency energy was delivered starting at a site 2 cm away from the EAAS in the direction of the pacing site. Radiofrequency energy application site was then gradually advanced toward EAAS until the termination of tachycardia to define the entrance of the slow conduction area. Results The EAAS was orthodromically captured by pacing delivered from one of the high anterolateral RA (n = 6), high posteroseptal RA (n = 9), and RA appendage (n = 2). Radiofrequency energy delivery to the site, 10.1 ± 2.8 mm away from the EAAS, terminated V-AT immediately after the onset of delivery (2.9 ± 1.0 seconds). The successful ablation site located outside the Koch's triangle, being more distant from the His bundle site than the EAAS (12.4 ± 2.9 vs 6.4 ± 1.9 mm; P Conclusion The reentry circuit of V-AT located outside the Koch's triangle. V-AT was eliminated by the radiofrequency energy delivered to the entrance of the reentry circuit, which was more distant from the His bundle site than the EAAS, under the navigation of entrainment.