EKG of the Week 2019 9-8

This EKG comes courtesy of Dr. Litvak.


An 83 year old female with a history of COPD and CAD presents to the ED with a brief episode of right sided chest pain associated with palpitations. Patient denies syncope. No nausea or vomiting. No SOB.

Vital signs: Pulse – 80, R – 18, BP - 144/92, O2 sat 98%.

Her EKG is attached.

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1.     What is the rhythm?

2.     How would you manage this patient?


Sinus rhythm with non-conducted PAC’s

 Non-conducted PAC’s are treated the same as patients with PAC’s – look for a cause, check electrolytes, usually no emergent intervention needed.


The EKG demonstrates a sinus rhythm at a rate of approximately 80. After beats #4, 7 and 11, there are P waves with no QRS complex following them.

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However this is NOT 2nd degree AV block. If you map out the P waves, the “dropped” P waves come earlier than expected. In fact, they come right after the preceding T wave. Since the P waves come so early, the ventricles are still refractory so they do not conduct.

The way we know this is not AV block is because the P waves come earlier than expected. This patient needs no emergent intervention and should not have a pacemaker placed.

Non-conducted PAC’s may appear like a 2nd degree AV block. You see P waves with no QRS complex following them and a pause on the rhythm strip. However, to call something 2nd degree AV block, the P waves must come on time (i.e. the P-P interval must be regular). So, whenever you diagnose AV block, measure the P-P intervals and make sure they are regular. If the “dropped” P wave comes early, it is likely a non-conducted PAC and not AV block.

Non-conducted PAC’s are a very common cause of pauses on EKG. Whenever you encounter a pause, look back at the preceding T wave before the pause to see if there is a P wave buried in there.

Pauses on EKG can be caused by 3 things: Non-conducted PAC’s, SA node disease (SA block and SA arrest), and AV block. The following algorithm may be useful to diagnose pauses:

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