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Case #39

You are covering the telemetry floor of a hospital. The nurse tells you that one of your patients is having a lot of irregular rhythms on the monitor. You take a quick look but cant decipher what is going on because the baseline is very poor. You tell the nurse to take the EKG machine and instead of getting a twelve lead, get you a rhythm strip with three leads on the ekg machine. She does and this is the rhythm strip she hands you. What is going on?

Click Here for better quality image of EKG

 

Here is an interesting case of competing pacemakers. Because this is not a twelve lead, we will not discuss the QRS complex and other diagnosis.

Starting from the first two complexes, the p waves are upright in II and AVF, suggesting that these are both sinus node beats. Measuring the P to P between the first two beats gives us a rate somewhere in the low 50's, which is pretty slow. The third complex has a p wave that is opposite the vector of the first two and the P-R is also a little shorter. These two findings suggest that this is an ectopic atrial beat, probably from the low right or left atrium. In this case by itself it would be a Premature atrial contraction. However what happens in the next 3 beats leads us to think something else.

Beat number 4 seams to be another sinus beat, as the p wave is the same as the first two and the p-r is also the same. But the next two beats, (5 and 6) are both again opposite vector as the first two and the same shorter p-r. Measuring the ectopic p to ectopic p interval you can see that the rate is @ the 70's.

So what is actually happening here is that the sinus rate is slow enough to allow another ectopic focus with a higher intrinsic rate take over. So here is a sinus brady at 50's with a competing ectopic atrial pacemaker in the 70's.

The patient was actually on high doses of beta blocker for blood pressure control which caused her sinus rate to be so suppressed. The Beta blockers where lowered and her sinus rate increased, going fast enough to not allow anymore of the ectopic beats to occur.