Atrial activation during atrioventricular nodal reentrant tachycardia: Studies on retrograde fast pathway conduction

Abstract

Detailed right and left septal mapping of retrograde atrial activation during typical atrioventricular nodal reentrant tachycardia (AVNRT) has not been undertaken and may provide insight into the complex physiology of AVNRT, especially the anatomic localization of the fast and slow pathways. The purpose of this study was to investigate the pattern of retrograde atrial activation during typical AVNRT by means of right-sided and left-sided septal mapping and implementation of pacing maneuvers for separating atrial and ventricular electrograms recorded during tachycardia. Twenty-two patients with slow-fast AVNRT were studied by means of simultaneous His-bundle recordings from the right and left sides of the septum. Patterns of retrograde atrial activation were recorded during tachycardia following specific pacing maneuvers and during right ventricular apical (RVA) pacing at the tachycardia cycle length. The pattern of retrograde atrial activation could be mapped in 17 of 22 patients during AVNRT. In 9 (53%) patients, the earliest retrograde atrial activation was recorded on the left side of the septum, in 3 (17%) patients on the right side, and in 5 (29%) patients both right and left atrial septal electrograms occurred simultaneously. Stimulus to atrial electrogram times recorded during RVA pacing in 14 patients were 138.5 ms from the right His bundle, 134.5 ms from the left His bundle, and 148.0 ms from the ostium of the coronary sinus (P <.001). The predominant site of earliest retrograde atrial activation during RVA pacing was the left side of the septum (10 patients [71%]). Only 8 (57%) of 14 patients demonstrated concordance in the pattern of retrograde atrial activation during AVNRT and RVA pacing. Earliest retrograde atrial activation during AVNRT is most often recorded on the left side of the septum. Breakthrough of atrial activation may be discordant from that observed during RVA pacing.