Adenosine-sensitive reentrant atrial tachycardia arising from atrioventricular annulus and atrial septum

Abstract

Background: Adenosine-sensitive reentrant atrial tachycardia (AT) originating from vicinity of the atrioventricular (AV) node and inside of the triangle of Koch was previously demonstrated. However, limited information is available on an AT with similar properties from the AV annulus. Objectives: The purpose of this study was to examine and compare ATs originating from the AV annulus and the atrial septum in electrophysiologic characteristics, pharmacological response and efficacy of radiofrequency ablation. Methods: In consecutive 21 patients with an AT that terminated with adenosine or verapamil intravenously given, the electrophysiological study and catheter ablation were performed. Results: In all patients, a targeted AT was inducible by atrial extrastimulation (AES) with an inverse relationship between the coupling and the post-pacing intervals. The mean tachycardia cycle length (TCL) was 396±49 ms. In 16 of 21 patients, the site of earliest activation was observed on the tricuspid annulus (annular AT). In the remaining 5 patients an AT occurred from the site in the triangle of Koch (septal AT). A single AES delivered from the site of earliest activation reset all ATs with an increasing or mixed pattern of response. Concealed entrainment was observed by rapid atrial pacing from the site of earliest activation for all ATs. These findings suggest that these ATs are due to reentry. Between the annular and septal AT, no significant difference was observed in the TCL, the percentage of the excitable gap to TCL, and other electrophysiologic characteristics. All ATs terminated by intravenous administration of verapamil (3.5±1.2 mg) and adenosine triphosphate (2.2±1.2 mg), indicating that a calcium channel–dependent substrate is involved in the AT circuit. ATs were successfully ablated at the atrial site of earliest activation in all patients. Conclusion: Adenosine-sensitive reentrant AT originates from either the AV annulus or the atrial septum. Both types of AT show similar electrophysiologic characteristics and response to catheter ablation.