V-A-A-V activation sequence at the onset of a long RP tachycardia: what is the mechanism?

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

INTRODUCTION

The electrophysiological discrimination between fast-slow (F/S-) atrioventricular (AV) nodal reentrant tachycardia (NRT) and atrial tachycardia (AT) originating from the interatrial septum remains challenging. While a V-A-A-V response may occur immediately after ventricular induction or entrainment of either tachycardia, the electrophysiological dissimilarities in that response between the two tachycardias remain unclear. The purpose of this study was to identify a diagnostic indicator discriminating F/S-AVNRT from AT by examining the difference in the V-A-A-V response between the two tachycardias.

METHODS

This retrospective study included 17 patients with F/S-AVNRT [7 with common-form F/S-AVNRT using a typical slow pathway (SP) and 10 with superior type F/S-AVNRT using a superior SP] and 10 patients with reentrant AT. All 27 patients presented with long RP supraventricular tachycardia and an initial V-A-A-V response upon ventricular induction or entrainment. The V-A-A-V response in patients with F/S-AVNRT was due to dual atrial responses. We measured the interval between the first (A1) and second atrial electrogram (A2) of V-A-A-V and calculated ΔAA by subtracting A1-A2 from the tachycardia cycle length.

RESULTS

V-A-A-V responses were observed most often upon ventricular induction of F/S-AVNRT (6±5 times) as well as AT (6±6 times; P = 0.87). The V-A-A-V response upon ventricular entrainment was observed in a single patient with F/S-AVNRT versus 10 all patients with AT (P<0.001). ΔAA ranged between -80 and 228 ms in F/S-AVNRT and between -184 and 26 ms in AT. A ΔAA >26 ms predicted a diagnosis of F/S-AVNRT with a 76% sensitivity and 100% specificity, while a ΔAA ←80 ms predicted a diagnosis of AT with a 50% sensitivity and 100% specificity.

CONCLUSIONS

ΔAA is a useful, confirmatory, diagnostic indicator of F/S-AVNRT versus AT associated with the V-A-A-V response. This article is protected by copyright. All rights reserved.

Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a "Superior" Slow Pathway: A Distinct Supraventricular Tachyarrhythmia

BACKGROUND

The existence of an atypical fast-slow (F/S) atrioventricular nodal reentrant tachycardia (AVNRT) including a superior (sup) pathway with slow conductive properties and an atrial exit near the His bundle has not been confirmed.

METHODS AND RESULTS

We studied 6 women and 2 men (age, 74 ± 7 years) with sup-F/S-AVNRT who underwent successful radiofrequency ablation near the His bundle. Programmed ventricular stimulation induced retrograde conduction over a superior SP with an earliest atrial activation near the His bundle, a mean shortest spike-atrial interval of 378 ± 119 milliseconds, and decremental properties in all patients. sup-F/S-AVNRT was characterized by a long-RP interval; a retrograde atrial activation sequence during tachycardia identical to that over a sup-SP during ventricular pacing; ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia in 5 patients or atrioventricular block occurring during tachycardia in 3 patients, excluding atrioventricular reentrant tachycardia; termination of the tachycardia by ATP; and a V-A-V activation sequence immediately after ventricular induction or entrainment of the tachycardia, including dual atrial responses in 2 patients. Elimination or modification of retrograde conduction over the sup-SP by ablation near the right perinodal region or from the noncoronary cusp of Valsalva eliminated and confirmed the diagnosis of AVNRT in 4 patients each.

CONCLUSIONS

sup-F/S-AVNRT is a distinct supraventricular tachycardia, incorporating an SP located above the Koch triangle as the retrograde limb, that can be eliminated by radiofrequency ablation.