• Shih-Lin Chang, Ching-Tai Tai, Yenn-Jiang Lin, Wanwarang Wongcharoen, Li-Wei Lo, Kun-Tai Lee, Sheng-Hsiung Chang, Ta-Chuan Tuan, Yi-Jen Chen, Ming-Hsiung Hsieh, Hsuan-Ming Tsao, Mei-Han Wu, Ming-Huei Sheu, Cheng-Yen Chang, and Shih-Ann Chen.
• Division of Cardiology and Cardiovascular Research Center, National Yang-Ming University, School of Medicine, Taipei, Taiwan.
• J. Am. Coll. Cardiol. 2007 Sep 4; 50 (10): 964-73.

ObjectivesWe sought to investigate the imaging of the left atrial (LA) muscular bundle and the relationship between the bundle and inducibility of tachyarrhythmia after pulmonary vein isolation (PVI).BackgroundNoninducibility is used as a clinical end point of atrial substrate ablation after PVI. However, little is known about the role of the LA muscular bundles in tachyarrhythmia after PVI.MethodsForty-three consecutive patients with paroxysmal atrial fibrillation who underwent catheter ablation were included. Bi-atrial isochronal mapping was performed with the NavX system (St. Jude Medical Inc., St. Paul, Minnesota) during sinus rhythm. After 4 PVI, inducible organized LA flutter with or without transforming to atrial fibrillation (AF) (LA flutter/AF) was ablated with additional lines at the roof and/or mitral isthmus.ResultsThe existence of bilateral muscular bundles was an independent predictor of LA flutter/AF after PVI (p = 0.02). Patients with LA flutter/AF after PVI had a greater index of the double potentials (5.4 +/- 3.4% vs. 2.8 +/- 1.8%, p = 0.006) and interpotential interval (33 +/- 5 ms vs. 29 +/- 4 ms, p = 0.02) than without LA flutter/AF. The muscular bundles were identified in 28% patients using 16-slice multidetector computed tomography, which were identical to the isochrone map. Patients with noninducible LA flutter/AF after PVI plus the additional linear ablation had a lower recurrence rate as compared with the patients without it (19% vs. 75%, p = 0.02).ConclusionsLeft atrial muscular bundles may provide a conduction block line and barrier, which is important for the formation of LA flutter/AF after PVI. The noninducibility of LA flutter/AF achieved after additional linear ablation may contribute to a better outcome in RF ablation of paroxysmal atrial fibrillation.

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