Differential Diagnosis of Supraventricular Tachycardia with Ventriculoatrial Dissociation during Ventricular Overdrive Pacing

Abstract

Case PresentationA 72-year-old man with a history of multiple episodes of paroxysmal supraventricular tachycardia underwent electrophysiologic studies and a catheter ablation procedure. The 12-lead electrocardiogram during tachycardia showed long RP' tachycardia with negative P waves in leads II, III, and aVF. Ventriculoatrial (VA) conduction with a shortest 1:1 pacing cycle length of 780 ms and earliest atrial activation at the ostium of coronary sinus was observed during ventricular overdrive pacing. A narrow QRS tachycardia documented previously was reproducibly induced by programmed atrial, though not ventricular, stimulation. During tachycardia, the His-atrial (HA) and atrial-His (AH) intervals were 381 and 156 ms, respectively. The atrial activation sequence during tachycardia seemed identical to that during ventricular pacing. A 2-mg bolus injection of adenosine triphosphate reproducibly terminated the tachycardia after a last ventricular event, following progressive prolongation of the atrial cycle length. Overdrive ventricular pacing for >30 seconds during tachycardia, at a cycle length 10-30 ms shorter than the tachycardia cycle length, invariably caused VA dissociation without atrial capture or termination of the tachycardia (Fig. 1). What is the tachycardia mechanism? CommentSince (1) the earliest atrial activation was in the right posteroseptal atrium, and (2) the Disclosure: The authors have no conflict of interest to disclose.AH interval was shorter than the HA interval, the differential diagnosis includes (a) atrial tachycardia (AT) originating in the posterior septum, (b) atypical fast-slow atrioventricular nodal reentrant tachycardia (AVNRT), and (c) orthodromic atrioventricular reentrant tachycardia (AVRT) using a slowly conducting decremental posteroseptal accessory pathway. As shown in Figure 1, VA dissociation was observed during overdrive ventricular pacing, ruling out AVRT. Entrainment of the tachycardia by ventricular pacing at a slightly shorter cycle length usually provides key information to discriminate between AT and AVNRT. 1,2 This maneuver is useful when, before cessation of ventricular pacing, the atrial rate accelerates to the ventricular pacing rate. 1,2 In the present case, the tachycardia was not entrained, and burst pacing had no effect on the tachycardia. However, the reproducible termination of the tachycardia without atrial activation, with a single ventricular extrastimulus delivered during the tachycardia, was sufficient to confirm the diagnosis of AVNRT (Fig. 2). 3 Although failure of ventricular overdrive pacing to change the atrial rate and the atrial activation sequence during tachycardia is observed in the minority of AVNRT, it does not exclude this diagnosis. 2,4,5 This phenomenon suggests the existence of a lower common pathway, below the site of AV nodal reentry, where VA block occurs during overdrive pacing. 3 The diagnostic contribution of ventricular extrastimulation during tachycardia in such cases of AVNRT has not been previously discussed in the literature....

Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Incorporating a “Superior” Slow Pathway

“…Although it is not specific, this phenomenon is characteristic of the sup-F/S-AVNRT and may be attributable to a functional ventriculoatrial conduction block below the atrioventricular nodal reentrant circuit (the lower common pathway) during ongoing tachycardia. 8,9,23,24 The cause of a high rate of ventriculoatrial by guest on May 11, 2018 http://circ.ahajournals.org/ Downloaded from block during tachycardia at the level of the lower common pathway is uncertain, although its length, which varies among forms of AVNRT, may be related to its conduction properties.…”

“…8,9 Therefore, one might hypothesize that the reentrant circuit of an ATP-sensitive atrial tachycardia originating from the HB region is the same as that used in sup-F/S-AVNRT. However, this hypothesis may be difficult to verify because, if ventriculoatrial block is consistently observed during ongoing tachycardia, ventricular stimulation cannot entrain or terminate an ongoing tachycardia, neither confirming a diagnosis of AVNRT nor excluding a diagnosis of atrial tachycardia.…”

“…2,3 Briefly, the intracardiac electrograms during tachycardia were characterized by a longer HA than AH interval and an earliest site of atrial activation in the HB region during tachycardia identical to the retrograde conduction observed over the superior SP during RV pacing (Figure 1). Moreover, a diagnosis of orthodromic atrioventricular reentrant tachycardia incorporating a slowly conducting atrioventricular or nodoventricular accessory pathway 7 as the retrograde limb was excluded by 1 or all of the following observations: inability to modify or entrain the tachycardia by ventricular overdrive pacing, that is, the presence of ventriculoatrial dissociation during ventricular overdrive pacing of the tachycardia 8,9 (overdrive pacing criterion); development of second-degree atrioventricular block during ongoing tachycardia 10 ; or a shorter stimulus-to-atrial electrogram interval during entrainment pacing from the RV apex than from the RV base (differential entrainment pacing). 11 The diagnosis of atrial tachycardia was excluded by 1 or both of the following observations: termination of the tachycardia by ventricular pacing without atrial capture 12 or a V-A-V activation sequence after ventricular induction/reinitiation of the tachycardia resulting from retrograde conduction over the superior SP followed by anterograde conduction over the FP, 13 including dual atrial responses (DARs) from simultaneous retrograde conduction over the FP and superior SP after the last ventricular stimulus.…”

Successful Ablation of Atypical Atrioventricular Nodal Reentrant Tachycardia From a Noncoronary Sinus of Valsalva

“…In case of ventriculoatrial conduction block below the AV nodal reentrant circuit (the lower common pathway) during ongoing atypical AVNRT, also suggested by the presence of ventriculoatrial dissociation during ventricular pacing, the tachycardia would be misdiagnosed as atrial in origin. 22,23) This warrants further studies.…”

Atypical Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Using a Slow Pathway Extending to the Superoanterior Right Atrium

“…AV block development during the ongoing AVNRT could be explained by the anterograde block at the level of the lower common pathway (LCP) within the AV node. 1,6) The responses during the ventricular burst simulation of the tachycardia seemed to depend on the retrograde conductivities at the LCP: when the retrograde wavefront passed via the LCP and was blocked at the SP, a termination of the tachycardia without atrial capture could occur; however, VA dissociation could occur when the retrograde wavefront was blocked at the LCP. 2,5) Therefore, AV block during the tachycardia and VA block during the ventricular pacing of the tachycardia could coexist according to LCP conductivities.…”