A Rare ECG Event

Ventricular Standstill with Atrial Dissociation

Image Case

This strip is a rare ecg event. The initial strip shows sinus tachycardia with right bundle branch block (RBBB). A PVC initiates ventricular standstill and there is recovery of conduction several seconds after.  In the top strip, the P wave is marked with red arrow. As you go from left to right and the bottom, we can see a change in the morphology of the P wave.This is actually the separation of 2 p waves (black and red arrows at the bottom strip). The other P wave is smaller (black arrow) than the other (red arrow). This is from a post-cardiac transplant patient. So, what we have is ventricular standstill that unmasked the 2 p waves (atrial dissociation). One P wave is from the recipient and the other is from the donor.

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