Saturday, October 10, 2015

This ECG was texted to me last night with the question: Occlusion or Not?

This ECG was sent along with this text:



"Thoughts? Occlusion or not? - context : cardiac arrest:"
Here is my answer: 
"Yes, but probably > 6 hours old, or an acute superimposed on an old MI, but there is acute STEMI here."

Question:

"You think the ST elevation is diagnostic according to criteria?"

Answer (Quoted):

"Not according to criteria.  
But you cannot call it normal variant ST elevation when there are Q-waves like that." 

So the differential is:
"Old MI with persistent ST elevation (LV aneurysm)" 
vs. 
"Subacute MI" 
vs. 
"Old MI with superimposed STEMI."  

"I have derived and validated a formula to differentiate LV aneurysm from acute MI: if there is one lead of V1-V4 with a T/QRS ratio > 0.36, then it is 90% specific for acute.  In this case, V3 has a 5 mm T-wave and the QRS amplitude is 8.5 mm.  5/8.5 = about 0.6 which is far higher than 0.36."   Also V4.

Question:

How about ultrasound?

Answer:

"There will be an anterior wall motion abnormality (WMA) for sure, but you won’t be able to tell whether it is old or old with superimposed acute.  Either one could have WMA with thinned out wall.  Only acute has a T-wave like that."


Outcome:

"I pushed for the activation - proximal LAD 100% - I'm glad I pushed for it.  First troponin I returned at 11."

My answer:

"Just as I said: Subacute STEMI"

Aside: Ryan Tee also noted correctly that there is also a PVC in aVL with concordant ST elevation. This is a very good sign for STEMI, but it could possibly also be seen in LV aneurysm. 


Comment

One might say that any shockable cardiac arrest should go to the cath lab emergently, and there are many good arguments for that.  Most of these arguments are based on "if there is no alternative explanation."

Old MI is such an alternative explanation, as it supplies the underlying substrate (scarred myocardium) that leads to ventricular fibrillation.

Furthermore, not all hospitals actually take all shockable cardiac arrests for angiogram, but rather do so selectively for those with ECG evidence of ischemia (especially, of course, STEMI).

In this case there is a clear alternative diagnosis: old MI, and no obvious ischemia on the ECG.  

But that is only true if you do not understand the T-wave in old MI: it is not large, but rather small or slightly inverted.  

The T-waves were too large and upright in V3 and V4 to be due to old MI.  They had to be acute (or, I should say, subacute).  This is confirmed by the initial troponin of 11, which is only present in MI that has been going on for "a while" (at least 6 hours).

11 comments:

  1. You could distinguish new vs old regional wall abnormality by wall thickness? Is initial troponin. However a result of CPR followed by electrical cardioversion?

    ReplyDelete
    Replies
    1. Dave,
      Yes, You could distinguish old vs. new.
      But you could not distinguish old vs. old with superimposed new. Only the T-wave does that.
      A troponin of 11 is too high for CPR/cardioversion. Those are < 3
      Steve

      Delete
  2. What about fragmented QRS in leads (V1, V3 ,V4) which represent scarred myocardium due to previous MI that cause fatal arrhythmia ?

    ReplyDelete
    Replies
    1. Mostafa,
      I did not mention that, but good point. It could also be due to subacute MI, not necessarily old MI.
      Steve

      Delete
  3. Great post, Steve! And the link to the other Walsh article is excellent as well. There are a few other interesting findings on the ECG (though certainly none would not have usurped the urgency of determining the need to go to the cath lab immediately).

    Did you notice the width of some of the P waves? Very wide. There is also an atrial bigeminy throughout the tracing. The P waves in V1 are not easily seen (except for one) but the negative component in V2 appears to show some prominence. I think this most likely represents a left atrial abnormality due to atrial enlargement or an interatrial block (there's also a 1st degree AV block). Do you know if anything was ever revealed about the patient indicating why there would be an LA abnormality or if there was any other evidence of LVH?

    ReplyDelete
    Replies
    1. Jerry,
      Good observations, but I know nothing else about the patient.
      Thanks!
      Steve

      Delete
  4. An impressive case. This patient may had old MI with LV aneurysm and the typical V5-6 T wave should be discordant to QRS? But this EKG is concordant. Did this also be a hint of subacute STEMI?

    ReplyDelete
    Replies
    1. Discordance and concordance do not apply to LV aneurysm. As stated in the post, from the ECG alone it could be aneurysm + superimposed acute STEMI, or subacute STEMI.

      Delete
  5. can you talk a little bit more about the concordant ST elevation in the PVC's. how much can you read into the morphology of the PVC? Thanks!

    ReplyDelete
    Replies
    1. There are no formal studies of this, but in my experience, you can treat PVCs ALMOST like bundle branch blocks. concordant ST elevation or depression, or excessively discordant (by proportion > 25%) ST elevation or depression is all but diagnostic of transmural ischemia.
      Steve Smith

      Delete

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