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Left Posterior Fascicular Block

Instructors' Collection, ECG of the WEEK, May 13, 2013: Right Bundle Branch Block With Left Posterior Fascicular Block

Mon, 05/13/2013 - 10:09 -- Dawn

This is a good clear example of right bundle branch block with left posterior fascicular block.  The RBBB is diagnosed by the following criteria:  wide QRS (.12 sec), supraventricular rhythm (NSR), an rsR' pattern in V1, and wide little s waves in I and V6.  The LPFB is inferred by the right axis deviation (Lead III QRS is a bit taller than Lead II and Leads I and aVL are negative), and the fact that there is no other obvious cause for right axis shift noted in this patient.  This constitutes a BIFASCICULAR BLOCK.  The ventricles are being depolarized by way of the anterior fascicle.  In addition, there are slight ST elevations in many leads, with an upward coving in the anterior-septal leads (V1, V2, V3).  Depending upon the patient's history and presentation, this could represent a recent M.I. or pending issues. The borderline first-degree AV block may be of concern in this patient, since first-degree AVB is associated with progression of bifascicular block to complete heart block.  Reference:  Ann Card Anaest, 2010 Jan-Apr;13(1):7-15. doi: 10.4103/0971-9784.58828

 

Anterior Wall M.I. With Bifascicular Block

Fri, 10/19/2012 - 22:46 -- Dawn

This is a good example of acute anterior wall M.I., with ST elevation in V1 through V6, as well as in Leads I and aVL.  The extensive distribution of ST segment elevations across the anterior and high lateral walls indicates a proximal LAD artery occlusion.  In addition, this ECG shows right bundle branch block, with a QRS width of 144 ms (.14 sec.) and an rsR' pattern in V1. There is also a wide s wave in Lead I which is partly obscurred in V6 by the ST elevation.  The right axis deviation (98 degrees) suggests a left posterior fascicular block which, when coupled with the RBBB, is a bi-fascicular block.  P waves are difficult to see.  Do you think they are found at the end of the QRS complexes, representing a long first-degree AVB?  Look at leads V3 through V6 for clues.

Please feel free to add your comments below.  The more "gurus" the better.

A good ECG to teach your students that a patient facing a life-threatening emergency may have a "normal" rate and regular rhythm.  There is something in this ECG for beginners through advanced students.

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