Superior-Type Fast-Slow Atrioventricular Nodal Reentrant Tachycardia Phenotype Mimicking the Slow-Fast Type

Abstract

Background - Superior-type fast-slow (sup-F/S-) atrioventricular nodal reentrant tachycardia (AVNRT) is a rare AVNRT variant using a superior (sup-) slow pathway (SP) as the retrograde limb. Its intracardiac appearance, characterized by a short atrio-His (AH) interval and the earliest site of atrial activation in the His-bundle (HB; EAA-HB), is an initial indicator for making a diagnosis. Methods - Among 22 consecutive patients with sup-F/S-AVNRT, three (age, 68-81 years) patients had an apparent but not typical slow-fast (S/F) AVNRT characterized by a long AH interval and EAA-HB (tachy-long-AH). Results - The diagnosis of sup-F/S-AVNRT was based on the standard criteria in two patients and on the occurrence of Wenckebach-type AV block during tachycardia, which was attributable to a block at the lower common pathway (LCP) below the circuit of the AVNRT, detected owing to the LCP potentials, in one patient. As with the typical S/F-AVNRT, tachy-long-AH was induced after a jump in the AH interval. In contrast to typical S/F-AVNRT, fluctuation in the ventriculoatrial interval was observed during the tachy-long-AH. Ventricular overdrive pacing was unable to entrain or terminate the tachy-long-AH. Moreover, the tachy-long-AH reciprocally transited to/from sup-F/S-AVNRT spontaneously or was triggered by ventricular contractions while the atrial cycle length and EAA remained unchanged. Both tachycardias were cured by ablation at a single site in the right-side parahisian region of two patients and the non-coronary aortic cusp of one patient. Collectively, the essential circuit of both tachycardias was identical, and the tachy-long-AH was diagnosed as another phenotype of sup-F/S-AVNRT accompanied by sustained antegrade conduction via another bystander SP breaking through the HB owing to the repetitive antegrade block at the LCP, thus representing a long AH interval during the ongoing sup-F/S-AVNRT. Conclusions - An unknown sup-F/S-AVNRT phenotype exists that apparently mimics the typical S/F-AVNRT and is also an unknown subtype of apparent S/F-AVNRT.

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

“…The HA difference measured after each EP attempt was classified as an unequal response when ≥20 ms, versus equal response when <20 ms. Moreover, to examine the dynamics of the Criteria of exclusion of atrial tachycardia 1) A V-A-V activation sequence after right ventricular induction/entrainment 6 2) Dual atrial response 4,5 3) Termination of tachycardia by ventricular stimulation without atrial capture 4) Presence of ventriculoatrial linking 7 5) Demonstration of lower common pathway as the site of atrioventricular block during tachycardia 8 16 (57) 5 ( 18 Values are numbers (%) of observations. *VA dissociation during the initial phase (QRS transition zone) of tachycardia overdrive ventricular pacing.…”

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 electrophysiologic studies were performed as described previously 3–5 . In this study, premature ventricular stimulation or ventricular burst stimulation inducing the long RP supraventricular tachycardia is referred to as ventricular induction, while ventricular burst stimulation during ongoing tachycardia, followed by its reinitiation, is referred to as ventricular entrainment.…”

“…Instead, we diagnosed AT when ≥1 of the following original three criteria were fulfilled (Table S2): The first observation was an earliest site of atrial activation during tachycardia in the right atrial (RA) free wall, away from the tricuspid annulus, including the interatrial septum and near the sinus node, 12 or in the RA free wall adjacent to the tricuspid annulus, between 8 and 11 o'clock in the left anterior oblique fluoroscopic view (site of origin criterion). This criterion excluded, in particular, the misdiagnosis as AT, of atypical F/S‐AVNRT with earliest sites of atrial activation in the superior, 3–5 superoanterior 22 or inferolateral RA 23 Second was the observation of intra‐atrial fusion during ventricular entrainment of the tachycardia 24 (intra‐atrial fusion criterion; Figure 1).…”

“…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 …”