Pacing site‐ and rate‐dependent shortening of retrograde conduction time over the slow pathway after atrial entrainment of fast‐slow atrioventricular nodal reentrant tachycardia

Abstract

Introduction: We tested our hypothesis that atrial entrainment pacing (EP) of a) the common-type (com-) fast-slow (F/S-) atypical atrioventricular nodal reentrant tachycardia (AVNRT) using a typical slow pathway (SP), or b) the superior-type (sup-) F/S-AVNRT using a superior SP, both modify the retrograde conduction time across the SP immediately after termination of EP (retro-SP-time). Methods:We measured the difference in the His-atrial interval (HA difference) immediately after cessation of EP, performed at 2 ± 2 rates from the high right atrium (HA[1]-HRA) versus from the proximal coronary sinus (HA[1]-CS) in 17 patients with com-F/S-AVNRT and 11 patients with sup-F/S-AVNRT. We also measured the atrial-His and HA intervals of the first and second cycles immediately after cessation of EP and during stable tachycardia.Results: Unequal responses, defined as a ≥ 20-ms HA difference at ≥1 EP rates, were observed in 16 patients (57%), including 7 with com-and 9 with sup-F/S-AVNRT.Irrespective of the EP rate, all unequal responses of com-F/S-AVNRT were due to a shorter HA[1]-CS than HA[1]-HRA, with a mean 34 ± 11 ms HA difference, whereas all unequal responses of sup-F/S-AVNRT were due to a longer HA[1]-CS than HA[1]-HRA, with a mean 49 ± 25 ms HA difference. The unequal responses resolved within two cycles after the cessation of EP. Conclusions:We have identified a little-known pacing site-and pacing ratedependent shortening of the retro-SP-time.

Discrimination of atypical atrioventricular nodal reentrant tachycardia from atrial tachycardia by the V‐A‐A‐V response

“…The earliest site of the second atrial electrogram (A2) was identical to that of the atrial activation during the tachycardia, consistent with retrograde activation over the SP used during the tachycardia 3–5,14–17 …”

“…The main criteria, used in multiple previous observations, include a V‐A‐A‐V response upon ventricular induction or entrainment, 35–39,43,44,46–48,50,51 AV block during the ongoing tachycardia, 32,33,35,38–40,42–44,47,48,51 VA dissociation during ventricular overdrive stimulation of the tachycardia, 35,38,40,42,43,47,49–51 a variability of the atrial cycles preceding the ventricular cycles during tachycardia, 33,35,38,40,42,43,47,50,51 absence of VA linking during differential atrial entrainment stimulation 35,44,46,48,51 and a non‐reproducible atrial activation sequence with ventricular stimulation during tachycardia 32,33,35,37,38,43,50,51 . However, it has now been shown that these criteria can all be satisfied in patients presenting with sup‐F/S‐AVNRT 3–5,17,52 . Similar observations have been made in the discrimination between AT‐CS 5 and com‐F/S‐AVNRT.…”

“…We did not use premature ventricular extra stimulation during tachycardia to exclude orthodromic atrioventricular reentrant tachycardia because of the occasional false negative response associated with this technique 25 . Furthermore, we made no attempt to discriminate F/S‐AVNRT from AT with atrial pacing maneuvers, such as comparing the AH interval during tachycardia with that during atrial pacing at a cycle length (CL) identical to the tachycardia, 26 or using differential atrial entrainment pacing, 21 sample since (a) the former, which was not used in previous studies, may not discriminate F/S‐AVNRT without an upper common pathway from AT, 27 and (b) the latter sometimes represents the absence of ventriculoatrial (VA) linking, including in patients with F/S‐AVNRT 17 …”

“…Based on the diagnosis of F/S‐AVNRT, a DAR (Figures 3 and 4) was diagnosed when the V‐A‐A‐V activation sequence possessed the following characteristics: The earliest site of the first atrial electrogram (A1) was recorded in the HB region with an interval between the stimulus (S) and A1 consistent with retrograde conduction via a FP; The earliest site of the second atrial electrogram (A2) was identical to that of the atrial activation during the tachycardia, consistent with retrograde activation over the SP used during the tachycardia 3–5,14–17 …”

“…However, since a V‐A‐A‐V response caused by a dual atrial response (DAR) occurs often upon ventricular induction of F/S‐AVNRT, 3–5,14–17 a V‐A‐A‐V response alone is not diagnostic of AT. A DAR can be diagnosed by measuring the interval between the first (A1) and the second (A2) atrial electrogram (A1‐A2 interval) of the V‐A‐A‐V response, which may become shorter than the next cycle of the tachycardia, 3–5 and may be a more reliable diagnostic criterion of F/S‐AVNRT 3–5,17 . However, this proposed criterion is based on a theoretical difference in the mechanism of the V‐A‐A‐V response (A2 especially) in AT versus F/S‐AVNRT, and has not been verified by directly comparing the electrophysiological characteristics of the response between the two tachycardias.…”