It helps to remember how the current is conducted. The posterior fascicle originates inferiorly and posteriorly on the endocardium. Thus the initial flow of current in LV will be rightward and down, as current moves to the epicardium. Additionally, depolarization of the right ventricle is progressing normally. As depolarization progresses, it moves from inferior, posterior to anterior, superior giving you the patter noted below. Check out LITFL's page on LAFB.
Dr. Burns also provides a beautiful pearl that in LAFB you might see LVH voltage criteria in aVL (R wave height > 11 mm), but there will be no LV strain pattern.
Our thanks to Dr. Tim Davie for assembling the Copa Cardiogram each week. Please follow this link to get to spreadsheet of all Copa Cardiograms.
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