Friday, June 17, 2016

Anterior STEMI? Or Benign Early Repolarization?

This was sent to me by Jason Winter, of Facebook Clinical Electrocardiology Page https://www.facebook.com/EKG.ECG/

This is a 36 yo m with h/o TBI and epilepsy.  He had a seizure this morning and rolled out of bed unable to get up.   There were no injuries and no chest pain and he appeared well.  He complained of 3 days of diarrhea and abdominal pain.  The medics recorded a prehospital ECG: 
The computerized QTc is 397 ms
Jason writes: "
What's your thoughts Steve?"
Jason was very skeptical of STEMI.
What do you think?




















Jason,
I agree.
V4 especially looks like early repolarization.  There is high R-wave voltage.
The formula for differentiating LAD occlusion from early repolarization requires ST elevation at 60 ms after the J-point (here 5 mm), computerized QTc, and R-wave amplitude.  Unfortunately, the R-wave is cut off on this ECG but it appears as if it would be at least 20 mm.  This results in a value of 22.883.  While one should be suspicious of any value greater than 22.0, this does not indicate LAD occlusion.

Note: In our study, we excluded from analysis cases with 5 mm of ST elevation because they would be "obvious," not subtle, anterior MI.  But this measurement was at the J-point, which on this ECG is 4 mm.  STE at 60 ms after the J-point is substantially higher than at the J-point. 

Pretest probability: Especially when there is no Chest pain, or there are very atypical symptoms, one should be very suspicious of the diagnosis of coronary occlusion unless the ECG is crystal clear.

More analysis: V4 has a high J-point, after which the ST segment is comparatively flat, without a correspondingly massive T-wave.  The T-wave is, in fact, small compared to the large R-wave.  This also argues against STEMI.

What was the outcome?

Outcome

"I later found out that this is a patient who regularly calls paramedics to c/o chest pains and he had fooled many of them. And the cath lab is alerted most of the time."

So this was the patient's baseline ECG.

Learning point

This is not to suggest that such an ECG should summarily be dismissed, but that in a patient with a low pretest probability and such an ECG may indeed have early repolarization, and further investigation might be undertaken before any cath lab activation.

Look for old ECGs
Do serial ECGs
Do echocardiography




  

13 comments:

  1. Concave vs Convex, this case is Convex, not concaved i.e., Notch, J hook, Smiley face, etc..

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    Replies
    1. All precordial leads V2-V4 do have a trace of upward concavity, to my eye. There is a bit of inferior ST depression in aVF and, I agree, this is highly suspicious for LAD occlusion. But it goes to show that the two entities can be very difficult to differentiate.

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  2. Difficult one

    V3 is especially indicating STEMI

    What about the ST depression and TWI on inferior leads

    Thanks for the case ..

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    Replies
    1. Bashar,
      There is a bit of inferior ST depression in aVF (in addition to inferior T-wave inversion) and, I agree, this is highly suspicious for LAD occlusion. But it goes to show that the two entities can be very difficult to differentiate.
      Steve

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  3. Insightful case! I am curious Steve — How would you have interpreted this tracing if the patient was new to the Emergency Department and presented with new-onset chest pain but no prior tracing was available? This is admittedly a rhetorical question, which I suspect the 3 last lines under your “Learning Point” answers. THANK YOU for presenting this case!

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    Replies
    1. Ken,
      I probably would have activated the cath lab.
      Just goes to show that pretest probability is critical in making decisions based on the ECG!
      Steve

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    2. Thanks Steve — I feel MUCH better hearing your answer — :)

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  4. The inferior T-wave inversions are troubling without having a prior ECG for comparison.

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    Replies
    1. Paul,
      Indeed they are. I forgot to point that out and am glad to get comments on that.
      Steve

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  5. Very tough case, Steve. I noticed the P waves in the inferior leads were rather large and gothic-appearing, though the P waves in V1 were unremarkable. It would be interesting to know if there were any history of tricuspid stenosis or anything congenital. Also, the precordial T waves are really very impressive - if not for their height then for their width. Any idea why so wide? It makes me wonder if any of his seizure meds (assuming he is taking some) might have potassium-channel blocking capability, or even if he might be taking a potassium-channel blocker (which could widen the T wave without widening the QRS). I'm not sure how many people who are post-ictal and then have a coronary occlusion or acute spasm react to the pain. If I had never seen this patient before, knew nothing of his history other than he was post-ictal and had no access to a previous ECG, I would activate the cath lab.

    Thanks for a great website!

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    Replies
    1. Great comments as usual, Jerry.
      Thanks,
      Steve

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  6. The exlusion criteria is applied , and the patient is investigated for the need for timely reperfusion. As Jerry highlights findings of prominent P wave got me thinking. With the prodrome days of diarrhoea it had me looking for the potential for hypokaleamia on the ECG. When ischaemia is excluded could the P waves , T wave flattening and inversion , ST depression and U waves indicate this as a co differential ?

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    Replies
    1. I don't think this looks much like hypokalemia. These are typical U-waves for early repolarization, and T-waves are not flattened (some are inverted).

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