Improvement in the 3rd degree

And so we present the exciting conclusion to Why You Shouldn’t Skip Your Dialysis.  Let’s do a quick case review.  The patient presented with a very wide complex heart rate in the 120’s.  She was treated empirically for hyperkalemia and her QRS narrowed but rate increased to the 180’s.  About 2 minutes after receiving adenosine she converted to this EKG:

20170619_3rd degree

Hallelujah, she’s fixed!  Right?  If you have a system you’ll find the abnormality.  If you don’t you’ll just gestault this as a junctional brady.  Let’s look more carefully.

As always, start with the rate, in this case a little over 50.  What is the rhythm?  Well, it’s narrow complex.  Are there P waves?  In the central part of the EKG there aren’t.  However, you have to look everywhere.  Let’s look more closely inferiorly:


Clearly there are P waves initially, but then they disappear.  What happened?  The answer is in the PR interval.  You can see that the PR interval progressively shortens.  Who can name the condition with a progressively shortening PR interval??? You can’t.  There isn’t one.  This patient now has a 3rd degree heart block and it just so happens that the P-P interval is very close to the R-R interval, close enough that a person could assume a normal relationship between the P and the QRS where the P isn’t buried in the QRS.

Notice how the P waves re-appear as extra inflection points (the purple dots) in the repolarization cycle in V6:

20170619_3rd degree purple zoom

Here’s the entire EKG again with the P waves flagged:

20170619_3rd degree purple

So, this patient is in 3rd Degree Heart Block with a junctional escape rhythm.  Looking at the rest of the EKG, the QRS has narrowed nicely, but there remains fairly significant T wave peaking, still indicative that the patient remains hyperkalemic.

There’s two take-homes from this EKG.  First, beware shortening PR intervals; it generally indicates 3rd degree heart block.  Second, IN ANY WEIRD BRADYCARDIA, CONSIDER HYPERKALEMIA.  I’ve seen people float pacers in hyperkalemic patients.  They would have saved themselves a lot of time and effort by just fixing the potassium.

For this case dialysis was now ready for the patient and the rhythm was providing enough blood pressure to tolerate dialysis so we sent her there expecting that the block would resolve with fixing the potassium.  It did.

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