A 52 y/o male with a history of HTN presents to the ED complaining of palpitations on and off x 2 days. He reports he has been drinking a lot of caffeinated beverages. He now feels palpitations which begin abruptly, last 1-2 hours, then resolve. They have been recurring over the last couple of days. His EKG is below.
1. What is the rhythm?
2. How would you manage this patient?
The rhythm is sinus rhythm with non-conducted PAC’s
Non-conducted PAC’s are benign and usually require no treatment. The main point is to recognize this is NOT 2nd degree AV block and the patient does not need a pacemaker.
The EKG demonstrates P waves followed by QRS complexes. However, the rhythm is not completely regular. Beats 3 and 10 come early. These are premature atrial contractions (AKA PAC’s). We also see pauses on the EKG (after beats 5 and 7). At the beginning of those pauses, we see P waves buried in the preceding T waves. (Look at the notching in those T waves and compare them to the other T waves in the rhythm strip.) These P waves come earlier than expected and therefore also represent PAC’s. However, note that there is no QRS complex following these P waves. This happens because the P wave comes so early, at a time when the ventricles are still refractory. So, they do not conduct. These are called non-conducted PAC’s.
Non-conducted PAC’s may appear like a 2o AV block. You see P waves with no QRS complex following them and a pause on the rhythm strip. This is usually typical of 2nd degree AV block. However, to call something 2nd degree AV block, the P waves must come on time (i.e. the P-P interval must be regular). On our EKG, the P waves come early (i.e. the P-P interval is irregular). So, the reason the ventricles do not conduct is NOT because there is a block in the AV node. It is because the P wave came too early and the ventricles are not ready to contract yet. So, this patient does not have AV node disease and does not need a pacemaker.
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: