Third-degree (complete) Heart Block – Example 2

Table of Contents

Table of Contents

Brandon Fainstad, MD


  1. Determine key features of a A-V dissociation to identify complete heart block

Teaching Instructions

Plan to spend 5 minutes familiarizing yourself ECG.  Have the image pulled up on the presenting screen or monitor.  Ask for a full read of the ECG.  If the learner has not done so already, ask them to commit to a rhythm

Teaching point: Sinus rhythm is defined by  “a p before every qrs and a qrs after every p”.  If you have a qrs without a p there are premature ventricular contractions (PVCs) or ventricular escape.  If you have a p without a qrs there is a second or third degree AV block.  This is a third degree because there is complete dissociation.  None of the p waves are conducted as evidence of a regular ventricular rate with the same morphology. 


Complete (third degree) AV block with an atrial rate around 65 and a ventricular rate around 40.   Left axis deviation with a right bundle branch block and possible prior inferior infarct.

Take Home Points


Brandon Fainstad


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