Atrial and ventricular activation sequence after ventricular induction/entrainment pacing during fast-slow atrioventricular nodal reentrant tachycardia: New insight into the use of V-A-A-V for the differential diagnosis of supraventricular tachycardia.

Background: The atrial and ventricular response observed immediately after cessation of ventricular induction/entrainment pacing is commonly analyzed to discriminate atrial tachycardia from other supraventricular tachycardias during electrophysiologic studies. However, the response in fast-slow atrioventricular nodal reentrant tachycardia (F/S-AVNRT) remains poorly investigated.
Objective: The purpose of this study was to analyze the atrial and ventricular activation patterns after ventricular pacing in F/S-AVNRT.
Methods: We enrolled 28 patients with F/S-AVNRT incorporating a typical slow pathway (typ-F/S-AVNRT) and 9 patients with F/S-AVNRT incorporating a superior slow pathway (sup-F/S-AVNRT).
Results: The V-A-A-V response was observed in 14 patients (38%) with F/S-AVNRT, more commonly in patients with sup-F/S-AVNRT than in those with typ-F/S-AVNRT (89% vs 21%, P = .0003). The underlying mechanisms included (1) a double atrial response (DAR) in 13 patients; (2) an anterograde block at the lower common pathway once after ventricular pacing in 2 patients; and (3) a pseudo-A-A-V response in 2 patients. The DAR was characterized by a V-A-A-V interatrial interval that was 55 ± 60 ms shorter than the tachycardia cycle length, whereas the block at the lower common pathway or infrahisian block had a V-A-A-V interatrial interval that was almost equal to or longer than the tachycardia cycle length.
Conclusion: The V-A-A-V activation sequence immediately after ventricular induction/entrainment pacing is observed in patients with F/S-AVNRT, particularly in patients with sup-F/S-AVNRT, and is caused by multiple mechanisms, including a DAR, which is the major etiology.
(Copyright © 2017 Heart Rhythm Society. Published by Elsevier Inc. All rights reserved.)