Abstract 2519: Variant Forms of Adenosine-sensitive Atrial Tachycardia Originating from Right and Left Atrioventricular Nodal Transitional Areas
Background: We previously reported a clinical entity of adenosine-sensitive atrial tachycardia (AT) originating from near the apex of triangle of Koch due to focal reentry within the atrioventricular (AV) nodal transitional tissues without involvement of the AV nodal pathways. However, its variant forms have not been well characterized.
Methods and Results: Twenty-nine patients (male/female: 14/15, age: 51+/-19 years) had a focal AT originating from the vicinity of the AV node (cycle length: 380+/−90 msec) during electrophysiological study. The AT was induced by atrial extrastimulation with an inverse relationship between the coupling interval of an extrastimulus and the post-extrastimulus interval. Its induction was not related to a jump-up in the AH interval, and its perpetuation was independent of conduction block in the AV node. Ventricular pacing during tachycardia demonstrated AV dissociation without affecting the atrial cycle length. A very small dose of adenosine triphosphate (mean of 3.7+/-2.5 mg) could terminate the tachycardia. The earliest atrial activation site during tachycardia was recorded from the right anteroseptum in 17 (59%), the right midseptum in 1 (3%), the right posteroseptum in 6 (21%), the roof of the coronary sinus ostium in 3 patients (10%) and the left anteroseptum in 2 patients (7%), and each atrial activation sequence during tachycardia was different from that during ventriculo-atrial conduction. Radiofrequency ablation targeted to the earliest activation site (A/V radio of the local electrogram: 1.5+/−1.2, the interval from the local electrogram to the P wave onset: 49+/−17msec) successfully eliminated tachycardia in 22 (92%) of 24 attempted patients without affecting the anterograde and retrograde AV nodal conductions.
Conclusion: Marked variation was observed in the origin of the AT, encompassing the right and left atrial perinodal regions. The mode of tachycardia induction and the high sensitivity to adenosine triphosphate suggest this AT would be due to the focal reentry involving the AV nodal transitional tissues on the right and left sides. Radiofrequency ablation was safe and effective in eliminating the AT irrespective of the site of the origin.