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Our understanding of the variants of slow pathway (SP) and associated atypical atrioventricular (AV) nodal reentrant tachycardia (NRT) is still growing. We have identified variants extending outside Koch's triangle along the tricuspid annulus, including superior, superoanterior and inferolateral right atrial SP and associated atypical, fast-slow AVNRT. We review the history of each variant, their electrophysiological characteristics and related atypical AVNRT, and their treatment by catheter ablation. We focused our efforts on organizing the published information, as well as some unpublished, reliable data, and show the pitfalls of electrophysiological observations, along with keys to the diagnosis of atypical AVNRT. The superior-type of fast-slow AVNRT mimics adenosine-sensitive atrial tachycardia originating near the AV node and can be successfully treated by ablation of a superior SP form the right side of the perihisian region or from the non-coronary sinus of Valsalva. Fast-slow AVNRT using a superoanterior or inferolateral right atrial SP also mimics atrial tachycardia originating from the tricuspid annulus. We summarize the similarities among these variants of SP, and the origin of the atrial tachycardias, including their anatomical distributions and electrophysiological and pharmacological characteristics. Moreover, based on recent basic research reporting the presence of node-like AV ring tissue encircling the annuli in adult hearts, we propose the term "AV ring tachycardia" to designate the tachycardias that share the AV ring tissue as a common arrhythmogenic substrate. This review should help the readers recognize rare types of SP variants and associated AVNRT, and diagnose and cure these complex tachycardias. We hope, with this proposal of a unified tachycardia designation, to open a new chapter in clinical electrophysiology. [ABSTRACT FROM AUTHOR]

Our understanding of the variants of slow pathway (SP) and associated atypical atrioventricular (AV) nodal reentrant tachycardia (NRT) is still growing. We have identified variants extending outside Koch's triangle along the tricuspid annulus, including superior, superoanterior and inferolateral right atrial SP and associated atypical, fast-slow AVNRT. We review the history of each variant, their electrophysiological characteristics and related atypical AVNRT, and their treatment by catheter ablation. We focused our efforts on organizing the published information, as well as some unpublished, reliable data, and show the pitfalls of electrophysiological observations, along with keys to the diagnosis of atypical AVNRT. The superior-type of fast-slow AVNRT mimics adenosine-sensitive atrial tachycardia originating near the AV node and can be successfully treated by ablation of a superior SP form the right side of the perihisian region or from the non-coronary sinus of Valsalva. Fast-slow AVNRT using a superoanterior or inferolateral right atrial SP also mimics atrial tachycardia originating from the tricuspid annulus. We summarize the similarities among these variants of SP, and the origin of the atrial tachycardias, including their anatomical distributions and electrophysiological and pharmacological characteristics. Moreover, based on recent basic research reporting the presence of node-like AV ring tissue encircling the annuli in adult hearts, we propose the term "AV ring tachycardia" to designate the tachycardias that share the AV ring tissue as a common arrhythmogenic substrate. This review should help the readers recognize rare types of SP variants and associated AVNRT, and diagnose and cure these complex tachycardias. We hope, with this proposal of a unified tachycardia designation, to open a new chapter in clinical electrophysiology., Competing Interests: The authors declare no conflict of interest. Yoshiaki Kaneko is serving as one of the Guest editors of this journal. We declare that Yoshiaki Kaneko had no involvement in the peer review of this article and has no access to information regarding its peer review. Full responsibility for the editorial process for this article was delegated to Giacomo Mugnai., (Copyright: © 2022 The Author(s). Published by IMR Press.)

Introduction: Atrial tachycardia shows wide variations in its electrophysiologic properties and sites of origin. We report an atrial tachycardia with ECG manifestations and electrophysiologic characteristics similar to an atypical form of AV nodal reentrant tachycardia (AVNRT). Methods and Results: This supraventricular tachycardia was observed in 11 patients. It was initiated by atrial extrastimulation with an inverse relationship between the coupling interval of an extrastimulus and the postextrastimulus interval. Its induction was not related to a jump in the AH interval, and its perpetuation was independent of conduction block in the AV node. Ventricular pacing during tachycardia demonstrated AV dissociation without affecting the atrial cycle length. A very small dose of adenosine triphosphate (mean 3.9 ± 1.2 mg) could terminate the tachycardia. The earliest atrial activation during tachycardia was recorded at the low anteroseptal right atrium with a different intra-atrial activation sequence from that recorded during ventricular pacing, where the tachycardia was successfully ablated in 9 of 10 attempted patients. Bidirectional AV nodal conduction remained unaffected after successful ablation. Conclusion: There may be an entity of adenosine-sensitive atrial tachycardia probably due to focal reentry within the AV node or its transitional tissues without involvement of the AV nodal pathways. This tachycardia can be ablated without disturbing AV nodal conduction from the right atrial septum. [ABSTRACT FROM AUTHOR]