Optimal slow pathway ablation site for slow-fast atrioventricular nodal reentrant tachycardia with 2:1 atrioventricular conduction

The exact circuit responsible for the atrioventricular (AV) nodal reentrant tachycardia (AVNRT) is still unknown. We evaluated the optimal slow pathway ablation area in patients with and without 2:1 AV conduction during the slow-fast AVNRT.

Among 207 consecutive patients with slow-fast AVNRT who underwent slow pathway ablation, 12 (5.8 %) patients who had 2:1 AV conduction during tachycardia (group A) were included. Fifty-nine patients without 2:1 AV conduction during tachycardia or a lower common pathway (group B) were included as a control group. We measured the fluoroscopic vertical distance on the 45° left anterior oblique view between the optimal slow pathway ablation area and His bundle electrogram (HBE) recording site (height AH) and between the coronary sinus ostium and HBE site (height CH). The horizontal distances (width AH, width CH) on the 30° right anterior view were also measured.

The tachycardia cycle length (300 ± 39 vs. 371 ± 71 ms, p = 0.001) and AH interval during tachycardia (259 ± 33 vs. 324 ± 69 ms, p = 0.001) were significantly shorter in group A than in group B. The height AH/height CH was significantly smaller in group A than in group B (0.62 ± 0.15 vs. 0.76 ± 0.27, p = 0.034) whereas height CH was similar between the two groups (22.8 ± 6.4 vs. 23.4 ± 7.5 mm, p = 0.84). The width CA and width CH were similar between the two groups. Slow pathway ablation was successfully achieved in all 71 patients without any complications. The number of applications tended to be greater in group A than in group b; however, the difference did not reach statistical significance (8.8 ± 8.0 vs. 5.2 ± 5.2, p = 0.147).

The optimal slow pathway ablation area was located at a more superior position in group A than in group b.