Posterior (“atypical”) atrioventricular junctional reentrant tachycardia

Abstract

The aim of this study was to characterize a relatively rare type of atrioventricular (AV) junctional reentrant tachycardia (AVJRT). Posterior AVJRT is a type of AV nodal tachycardia in which the site of earliest atrial activation is posterior to the AV node near the coronary sinus orifice. The mechanism of this tachycardia is not well understood. The characteristics of posterior AVJRT (n = 15) were compared with those of anterior (“common”) AVJRT (n =146) and supraventricular tachycardia using single posterior septal accessory pathways (n = 13). During posterior AVJRT, the AH interval was longer than the, retrograde conduction time (His to earliest atrial activity) in 11 cases (73%), indicating that these tachycardias were not fast-slow types of AVJRT. The mean ventriculoatrial (VA) interval in posterior AVJRT (93 ± 41 ms) was longer than in anterior AVJRT (11 ± 20 ms; p <0.005), but was similar to that in tachycardias using accessory pathways (106 ± 16 ms; p = NS). The site of earliest atrial activation during posterior AVJRT was similar to that in tachycardias using accessory pathways. In all cases of accessory pathway-friediated tachycardia, atrial activation could be advanced by ventricular extrastimuli delivered coincident with the His deflection, but atrial activation was not advanced in any case of posterior AVJRT unless the extrastimulus was delivered >80 ms before the His deflection. Anterograde conduction was similar in the posted or and anterior AVJRT groups. During ventricular pacing, the VA interval was longer in patients with posterior AVJRT (287 ± 113 ms) than in those with anterior AVJRT (199 ± 48 ms; p <0.005) or accessory pathways (133 ± 43 ms; p <0.005), and closely coupled ventricular extrastimuli caused greater increases in the VA interval (172 ± 114 vs 102 ± 31 and 60 ± 60 ms, respectively; both p <0.01). In 73% of cases, posterior AVJRT used a slow pathway for anterograde conduction and a different “slow” pathway for retrograde conduction, and thus was not an antidromic form of “common” AV nodal reentry. The retrograde limb of the circuit did not have the characteristics of an accessory pathway.