This axis is your ally

Ever have a time in your life when you’re not quite sure what to do?  Where there’s good arguments to be made for 2 very different options?

Nah, me neither.

But we could on this EKG:

~60 y.o. woman with CP, normal Urine output and no LE edema

We start as always with the rate.  It’s clearly tachycardic, and the complexes are about 2 big boxes wide so this is right around 150.

What is the rhythm?  Well there aren’t P waves.  I think the couple people who suggested a sinus tach were looking at the lead II rhythm strip where the T waves are spaced close enough to the QRS that they could be taken for P waves at first glance.  The QRS is wide; this is a wide complex tachycardia.  Several people felt there was a Right Bundle Branch Block.  I agree there’s an RSR’ look to V1, but the QRS at 4 little boxes is too wide to be simply RBBB.  The problem is that the rate is slow for the average V tach; it’s most commonly in the 180’s.  The QRS is too wide to be a simple SVT; a person would have to invoke a co-existing LBBB.  This is the point where a person should question if this could be hyperkalemia.  In real life the providers did treat empirically for that; it had no effect, the potassium turned out to be normal, and I framed the vignette in a way to decrease the number of people who would choose hyperK.

So how to break the tie between a slow-ish V tach and a wide-ish SVT?  Well, let’s look at the axis.  There is a clearly downward deflection in I; normally this lead is upright.  If we look further at the EKG we see several leads that are the opposite of what we would expect.  12mm of R wave in aVL can be used as criteria for LVH; in this EKG aVL is downward deflected.  V1 normally is downward deflected, and then there’s R wave progression through the chest leads until it’s mainly upward in the lateral chest leads.  In this EKG the chest leads progress oppositely.  It’s that reversal of polarity in multiple leads that clinches this EKG as V Tach in my mind.

Don’t believe me?  Here’s her EKG after cardioversion:

20170918_post cardioversion

She was admitted and underwent successful AICD placement.

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