Friday, July 8, 2016

A 65 Year Old Man with Chest pain and Precordial ST Elevation

This case was sent by Sam Ghali (@EM_RESUS)


A 65-year-old gentleman presented to the ED complaining of chest pain.  He asked my thoughts on his presenting ECG:
Computerized QTc is 409 ms
What do you think?














Here is my response:

Strongly suspect normal variant or chest leads placed too high.
Possibly STEMI, but I strongly doubt.
In my life, I have seen one saddleback (such as this) that was a STEMI.
Outcome?


Here is Sam's analysis and outcome:

The obvious question at hand here: Is this acute LAD occlusion? 

There is an rSR' in V1 and S-waves in the lateral leads, but QRS less than 120 ms, thus an incomplete RBBB. There is significant ST-elevation in V1-V3, which meets ACC/AHA STEMI Criteria in these leads (greater than or equal to 2.0 mm in an male greater than or equal 40 yo). Also concerning for coronary occlusion, the T-waves are upright, large, and broad in appearance (especially in proportion to the QRS). There is inferior ST-depression in II, III, and AVF which in LAD occlusion is reciprocal to anterior ST-elevation. What speaks against LAD occlusion is the very well-developed R-waves in V3-V4. (As the ECG evolves in LAD occlusion, there is a loss of R-wave height as R-waves transition to Q-waves; however you wouldn't necessarily see this early on). There is concave-up ST-elevation which makes occlusion less likely, but by no means rules it out. What is also unusual in this case is the “saddleback” morphology of the ST-segment elevation.

A prior ECG would be helpful here, but there was none. A bedside echo looking at LAD distribution wall motion might also be helpful but due to logistical reasons this too was not an option. The decision was made to activate the cath lab. 

Outcome

The cath revealed chronic total occlusion of the RCA, with good collateral flow. There were multiple 40-50% lesions throughout the LAD and it’s Diagonals, as well as in the Circ. There was no acute occlusion.   Serial troponins were negative.  Echo did not show LVH.

I shared the case with Steve Smith to gain his expert insight, but here are my comments:

1. STEMI Criteria are imperfect - not nearly sensitive nor specific enough for strict use

2. Even with other ECG features taken into account, diagnosing acute LAD occlusion can be very difficult. The Subtle Anterior STEMI formula which may provide diagnostic guidance here, technically should not be used in the presence of inferior ST-depression.

3. While “saddleback” ST-elevation is less likely to be coronary occlusion, it is still possible for STEMI to have this morphology.

4.  Ultimately, if after all measures there is still concern for acute LAD occlusion, the diagnosis may be best excluded in the cath lab.

Smith comments:

This is saddleback ST elevation, such as one commonly sees in LVH or in type 2 Brugada.  It can also happen if chest leads are placed too high.  It is rarely due to STEMI.  (I was a bit surprised to hear that the echocardiogram did not show any LVH).

The inferior ST depression is probably a false positive.  If you look at the PR segment, it is downsloping.  This is a frequently encountered atrial repolarization wave, and this wave is persistent after the end of the QRS, causing a mimic of ST depression.

Atrial Repolarization wave mimicking ST depression:
You can read about it at this post.
You can watch a K. Wang video about this at this post.

Thus, the formula can be used.  The R-wave amplitude in V4 is the single most powerful predictor of early repol vs. LAD occlusion: a high amplitude, which here is very high at 25 mm, goes strongly against LAD occlusion.  The formula value here, using STE60V3 of 2.5 mm, is very low at 18.97.

Even if the QTc were very long, at 460 ms, the formula value would still be very low at 21.98 (less than 22.0), which would all but rule out LAD occlusion.

That said, one cannot entirely rule out STEMI with the formula and such a case should always of course be approached carefully.

If available, I would do a stat formal echo rather than activate the cath lab.



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