Monday, May 16, 2016

ST Elevation: Inferior MI or Early Repol? Ultrasound Speckle Tracking Can Help.

Rob Reardon, our ultrasound director, showed me this ECG of a 50 yo with chest pain he had seen a few days prior:
I said "Early Repolarization in Limb Leads".
He had thought there might be some reciprocal ST depression in aVL and was worried about inferior MI.
I can see what he means, but I don't think it qualifies.

 
But these ECGs can be difficult.

As our ultrasound fellowship director, his solution was to do bedside ultrasound with Speckle Tracking Strain Echocardiography on our sophisticated Toshiba ultrasound machine.


We reported on Speckle Tracking recently in the American Journal of Emergency Medicine, where you can read about it in detail:

Diagnosis of acute coronary occlusion in patients with non–ST-elevation myocardial infarction by point-of-care echocardiography with speckle tracking: a case report


With Speckle Tracking, you mark the endocardium visually on a still picture, and then the computer follows that endocardium through the cardiac cycle, both showing and plotting its wall motion.

It is the next best thing to a contrast echocardiogram.

Here is the video he obtained:

The three segments at lower left are the inferior wall (AI = inferior apical, MI = mid apical, BI = basal inferior)
Speckle Tracking makes it so you can see that all of them contract (shorten and thicken) very well.
The graph on the right shows that your visual diagnosis is correct: the deep waves to (-30) confirm perfect function of all segments of the inferior wall.



Here is a still image:
On the left, the 2 arrows point to the mid inferior and basal inferior segments.
On the left, the one arrow points to the Purple-blue line corresponding to the purple-blue basal inferior segment, confirming that it has full contractility.



This allayed his concerns of inferior MI, but only because he is a real expert at doing this.

The patient ruled out for MI by biomarkers and the ECG did not evolve.

Speckle Tracking can also be falsely re-assuring if not done right and improperly interpreted" see this very instructive example:
Low HEART score. Acute LAD occlusion. Detected only by analysis of subtle ECG.


Learning Points:

1. Speckle Tracking can be done by an experienced emergency physician.

2. Speckle Tracking can help you to recognize a STEMI mimic if there is perfect wall motion in the echocardiographic segment in question.

3.  However, you can have false negatives, especially if you are not expert in this.

4.  Fuly trust negative results only when your clinical and ECG suspicion are already low.

5.  Do not use it to definitively "rule out" coronary occlusion.  Rather, continue to evaluate with serial ECGs and possibly emergent formal contrast echo.









3 comments:

  1. In my hospital unfortunately we don't have Speckle Tracking and therefore we must rely on ECG (s) and transthoracic Echo; of course I admire this tecnique from the cultural point of view. Therefore what I would have studied are the reassuring ECG signs for ERP (concave ST elevation and so-called “fish-hook” sign in inferior leads); it's useful, to a certain degree, the normal QTc. BUT, as mentioned, there is AVL which is concerning and then serial ECGs are essential as you suggest.

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  2. Great post — insightful graphics — NO limit to what can be done at the bedside. THANKS for posting Steve!

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  3. The echo is a great adjunct so as long as there is no pre-existing wall motion abnormalities from a prior MI. Great if you have prior images or a read from prior echo. Speckle tracking takes out a lot of the guess work in wall motion abnormalities. I expect big things from it coming soon.

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