Old Anteroseptal MI & BBBB
Report:
Atrial fibrillation with rapid response 160/mi9n
Right bundle branch block
Left anterior hemiblock
Standard masquerading bundle branch block
Old anteroseptal infarction
Comment:
In 1 and aVL the QRS resembles LBBB rather than RBBB, a situation where only lead V1 can provide the correct diagnosis of RBBB. The LAHB is of a very high grade and loses its characteristic qR shape in lead 1. This is known as the standard form of masquerading BBB; a precordial form would include LBBB morphology in V6 as well.
The patient had a known anterior infarction years previously; its signature are the Q waves in V1-4, variable as they may be through a respiratory cycle.
Below is a trace taken 2 days earlier, in sinus (or atrial) rhythm, with two atrial (or sinus) early beats. The QRS shows LBBB pattern throughout, retaining the marked frontal LAD from disproportionate damage to the anterior-superior division of the left bundle branch (a divisional LBBB). The anteroseptal Q waves are no longer present, but a âseptalâ looking q wave is now present in V6. This, in LBBB conduction, is a sign of septal infarction (while, in normal conduction, septal infarcts abolish this q wave in V6).
RBBB and LBBB at different times are a manifestation of bilateral bundle branch block (BBBB).
90a. The qRs complex in V6 is a sign of anteroseptal infarction in LBBB conduction. There is also concordant T wave inversion in V2-3.
91. Exercise test of a 53 year old lady with angina of recent onset.
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