Background: Little information exists regarding the precise distribution of verapamil-sensitive atrial tachycardia originating from the vicinity of the atrioventricular node (V-AT).
Methods: In 12 patients with V-AT, we examined the spatial and topologic distribution of tachycardia origin relative to the His bundle (HB) site. The V-AT origin was divided into six areas: anterior (A-HB), posterior (P-HB), superior (S-HB), inferior (I-HB), lateral (L-HB), and septal (SP-HB) portion of HB catheter. Three dimensional distance between the distal pair of the electrodes of HB catheter and that of V-AT origin (DIS) was obtained by calculating the distances on the right and left anterior fluoroscopic images. Topologic distribution was expressed as the interval between the onset of the atrial electrogram of V-AT origin and that of HB catheter (INT).
Results: The tachycardia origin was observed at the P-HB in four, S-HB in two, I-HB in two, SP-HB in three, and L-HB in one patient. The tachycardia cycle length, DIS, and INT were 369 +/- 67 ms, 12 +/- 3 mm, and -12 +/- 8 ms, respectively. After successful ablation of initial V-AT (1st V-AT), V-AT with a different origin (2nd V-AT) was induced in five patients. The tachycardia origin, tachycardia cycle length, DIS, and INT of the 2nd V-AT (P-HB in three, S-HB in one, and SP-HB in one patient; 333 +/- 66 ms, 8 +/- 3 mm, and -11 +/- 4 ms, respectively) were not different from those of 1st V-AT.
Conclusions: V-AT often shows a shift in tachycardia origin to another site where the spatial and topologic distributions are similar to those of 1st V-AT.