Chest pain and Diffuse ST depression, with STE in aVR. You probably think it is left main…..

A 75 year old woman complained of very atypical chest pain, lasting days, worse with movement and palpation.

Here is her ECG (ECG-1):

There is diffuse ST depression, very worrisome for ischemia.

The patient had a negative initial troponin, which was puzzling to the providers.

The patient was admitted and serial troponins were all below the level of detection.

She underwent a stress sestamibi that was completely normal.

She had another ECG the next day (ECG-2):

Slightly slower sinus rhythm.
Now there is now only minimal, nonspecific, ST depression.

What do you think happened?

I was consulted on this ECG and I asked: “What is the K?”
The answer was 3.2 mEq/L, and I said “Well, that probably does not explain it.”

But the 2nd ECG normalized after K replacement to 3.9 mEq/L.  And there is no other explanation.

A potassium of 3.2 mEq/L is usually not low enough to cause ECG abnormalities. 

When there is a normal QRS (that is, no LBBB, LVH, WPW, RVH, LBBB, RBBB, pathologic Q-waves of old MI), then there are only 4 etiologies of ST depression that I know of:

1. Ischemia
2. Digoxin
3. Hypokalemia
4. Baseline, pre-existing (but it does not look like ECG-1 when it is benign, pre-existing STD)

The STD on ECG-1 almost certainly due to hypokalemia, and resolved with treatment of low K.

When do you need to admit a patient for hypokalemia?

That is really unknown.  My rule of thumb is:
1.  any K less than 2.8 (even though you are replacing it, because total body stores are very low) OR
2.  any ECG abnormalities that are due to hypoK.

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