creators_name: MacAlpin, Rex N. editors_name: Singh, Balbir editors_name: Lokhandwala, Yash editors_name: Francis, Johnson editors_name: Gupta, Anup type: journalp datestamp: 2005-04-24 lastmod: 2011-03-11 08:55:59 metadata_visibility: show title: Left Septal Fascicular Block: Myth Or Reality? ispublished: pub subjects: ipej full_text_status: public keywords: fascicular block; left septal fascicular block; intraventricular conduction defects; ventricular activation abstract: Anatomic studies have shown that the left bundle branch divides into three fascicles in most humans. Changes in the 12 lead ECG (electrocardiogram) due to conduction abnormalities of the left anterior fascicle and left posterior fascicle are now part of the standard repertoire of electrocardiographic interpretation. There are no standard criteria for detecting conduction defects involving the third left fascicle, the septal or median fascicle, and the very existence of such defects is still a matter of controversy. The purposes of this article are to review the available evidence on this subject, suggest electrocardiographic criteria for its recognition, and present examples which illustrate that left septal fascicular block does indeed exist as a specific entity. Left septal fascicular block is a polymorphic conduction defect which may explain some previously inadequately understood electrocardiographic abnormalities. date: 2003-07 date_type: published publication: Indian Pacing and Electrophysiology Journal volume: 3 number: 3 publisher: Indian Pacing and Electrophysiology Group pagerange: 157-177 refereed: TRUE referencetext: 1. Rosenbaum MB, Elizari M, Lazzari J. Los hemibloqueos. Buenos Aires: Editorial Paidos; 1968. 2. Rosenbaum MB, Elizari MV, Lazzari JO. The hemiblocks. 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