The Role of Left Atrial Muscular Bundles in Catheter Ablation of Atrial Fibrillation
Shih-Lin Chang, MD*, ,
Ching-Tai Tai, MD*,
Yenn-Jiang Lin, MD*,
Wanwarang Wongcharoen, MD*,
Li-Wei Lo, MD*,
Kun-Tai Lee, MD*,
Sheng-Hsiung Chang, MD*,
Ta-Chuan Tuan, MD*,
Yi-Jen Chen, MD ,
Ming-Hsiung Hsieh, MD,
Hsuan-Ming Tsao, MD¶,
Mei-Han Wu, MD ,
Ming-Huei Sheu, MD,
Cheng-Yen Chang, MD and
Shih-Ann Chen, MD*,*
* Division of Cardiology and Cardiovascular Research Center, National Yang-Ming University, School of Medicine, Taipei, Taiwan
Radiology, National Yang-Ming University, School of Medicine, Taipei, Taiwan
Taipei Veterans General Hospital, Division of Cardiovascular Medicine, Division of Cardiovascular Medicine, Suao Veterans Hospital, Taipei Medical University, Taipei, Taiwan
Wan-Fang Hospital, Taipei, Taiwan
¶ Division of Cardiovascular Medicine, I-Lan Hospital, Taipei, Taiwan.
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Figure 2 Isochrone Map and Local Electrograms During Sinus Rhythm and LA Flutter
(A and B) The typical activation pattern in the left atrium (LA). The wavefronts propagating around the gray zone, where isochrone lines crowded together and double potentials were recorded during sinus rhythm in the anteroposterior and left posteromedial view, respectively. (C and D) Activation of a figure-of-eight LA flutter with a cycle length of 199 ms. Arrows indicate circuit loop(s). The brown lesion indicates the pulse of circumferential ablation. One loop rotates around the mitral annulus and the other rotates around the left PVs with a common channel conducted through the mitral isthmus. The re-entrant circuits of atrial flutter were bordered anteriorly and posteriorly by lines of conduction block (gray zone), which were in similar locations during sinus rhythm (A and B). (D) Illustrates the local bipolar electrograms along the circuit of double-loop re-entry. Recording positions are shown in the isochrone map. During LA flutter, clockwise atrial activation around the mitral annulus was manifested by atrial electrograms in the middle posterior wall (site 1), lower posterior wall (site 8), medial mitral isthmus (site 9), and lower anterior wall (site 10), followed by activation in the lateral mitral isthmus (sites 5, 11, and 7). A slow conduction zone with fractionated electrograms was recorded at site 5. Another counterclockwise atrial activation around the left pulmonary vein was manifested by atrial electrograms in the middle posterior wall (site 1), upper posterior wall (site 2), roof (site 3), and upper anterior wall (site 4) followed by activation in the lateral mitral isthmus (sites 5, 6, and 7). Labeled anatomical locations include the mitral valve (MV), right superior pulmonary vein (RSPV), right inferior pulmonary vein (RIPV), left superior pulmonary vein (LSPV), left inferior pulmonary vein (LIPV), and left atrial appendage (LAA).
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Figure 3 Atypical Activation Pattern in Left Atrium During Sinus Rhythm in Anteroposterior and Left Posteromedial Views, Respectively
(A) Anteroposterior view; (B) left posteromedial view. The earliest activation site occurred at the high posteroseptum with the wavefront extending to the roof, descending to the posterior wall near the left pulmonary vein, crossing over the lateral mitral isthmus, and ending at the left atrial appendage. Arrows indicate the activation wavefront.
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Figure 4 Endoscopic View of MDCT and Isochrone Map During Sinus Rhythm
(A and B) Location of a line of conduction block with double potentials (gray zone) marked on a 3-dimensional isochrone map during sinus rhythm in anteroposterior and posteroanterior view, respectively. (C) A 3-dimensional volume rendering technique of left atrial (LA) image, based on multidetector computed tomography (MDCT) in anteroposterior projection, that corresponds to (A). The orientation of the muscular bundles (yellow arrows) corresponds to the line of conduction block (gray zone) in (A). (D and E) Muscular bundles by the endoscopic view of MDCT. (D) The muscular bundles (red arrows) originate in the septum, extend near the fossa ovalis (white arrow), insert upward into the anterior roof, and spread down the posterior wall. In (E), the muscular bundle (red arrows) courses along the septal border of the right superior pulmonary vein (RSPV) ostium to the anterior roof. This location corresponds to the line of conduction block identified during sinus rhythm (A and B). LAA = left atrial appendage; other abbreviations as in Figure 2.
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Figure 5 Endoscopic View of MDCT and Isochrone Map During Left Atrial Flutter
(A) Muscular bundles (yellow arrows) by multidetector computed tomography (MDCT) in the endoscopic view. (B) Endoscopic view of a line of conduction block (gray zone), guided by NavX contact mapping, in the same projection as (A). The white arrow indicates the conduction circuit. Double potentials were recorded within the gray zone. The flutter circuit (cycle length, 219 ms) revolves around the muscular bundle, with an anteroseptal central obstacle. The orientation of this muscular bundle, as shown by MDCT endoscopic view, corresponds to the gray zone in the isochrone map. (C) The termination of LA flutter after delivering a line of ablation from the right superior pulmonary vein (RSPV) to the superior aspect of the septal muscular bundle. A circular catheter was placed in the posteroseptal wall. ABL d = distal ablation catheter Cir = circular catheter; CS-d = distal coronary sinus; CS-p = proximal coronary; LAA = left atrial appendage; other abbreviations as in Figure 2.
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