• Kiyoshi Otomo, Hideo Okamura, Takashi Noda, Kazuhiro Satomi, Wataru Shimizu, Kazuhiro Suyama, Takashi Kurita, Naohiko Aihara, and Shiro Kamakura.
• Department of Cardiovascular Medicine, Cardiovascular Center, Tsuchiura Kyodo Hospital, 11-7 Manabe-shin-machi, Tsuchiura, Ibaraki prefecture, 300-0053, Japan. k-otomo@fj8.so-net.ne.jp
• J. Cardiovasc. Electrophysiol. 2006 Nov 1; 17 (11): 1177-83.

IntroductionRecent anatomical and electrophysiological studies have demonstrated the presence of leftward posterior nodal extension (LPNE); however, its role in the genesis of atrioventricular nodal reentrant tachycardia (AVNRT) is poorly understood. This study was performed to characterize successful slow pathway (SP) ablation site and to elucidate the role of LPNE in genesis of atypical AVNRT with eccentric activation patterns within the coronary sinus (CS).Methods And ResultsAmong 45 patients with atypical AVNRT (slow-slow/fast-slow/both = 20/22/3 patients) with concentric (n = 37, 82%) or eccentric CS activation (n = 8, 18%), successful ablation site was evaluated. Among 35/37 patients (95%) with concentric CS activation, ablation at the conventional SP region outside CS eliminated both retrograde SP conduction and AVNRT inducibility. Among eight patients with eccentric CS activation, the earliest retrograde atrial activation was found at proximal CS 16 +/- 4 mm distal to the ostium during AVNRT. The earliest retrograde activation site was located at inferior to inferoseptal mitral annulus, consistent with the presumed location of LPNE. Ablation at the conventional SP region with electroanatomical approach only rendered AVNRT nonsustained without elimination of retrograde SP conduction in seven of eight patients (88%). Ablation targeted to the earliest retrograde atrial activation site within proximal CS (15 +/- 4 mm distal to the ostium); however, eliminated retrograde SP conduction and rendered AVNRT noninducible in six of eight patients (75%).ConclusionIn 75% of "left-variant" atypical AVNRT, ablation within proximal CS was required to eliminate eccentric retrograde SP conduction and render AVNRT noninducible, suggesting LPNE formed retrograde limb of reentrant circuit.

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