The posterior fascicle is much large and less susceptible to injury. As such it is not likely to occur in isolation, and more commonly seen with some AV node dysfunction as a Bifascicular block (LPFB + RBBB). Dr, Burns walks us through some of expected ECG findings and also reminds that you should not dx LPFB without first considering more worrisome causes of right axis deviation: PE, TCA overdose, lateral MI, or RVH. Check out his post on LITFL.
Conduction goes down functioning anterior fascicle, from endocardium to epicardium (initial small voltage) to remaining myocardium from the anterior/superior LV towards the inferior/posterior LV resulting in the following changes:
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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