Wednesday, December 27, 2017

Ed Burns (from Life in the Fast Lane) sent me this one....

Ed Burns (who is the creator of the incredible, fantastic, Life in the Fast Lane ECG library) sent me this one....


This is a from a patient with chest pain:

What do you think?
There is very little ST elevation, only 1 mm at the J-point in V2 and V3









Ed's message was this:


Hi Steve,

A colleague sent me this ECG today.
I responded saying that it was a STEMI...
I thought the STs were a little too straight in V2-3 and the T waves a little tall, plus the reciprocal changes in lead III.

Can you improve on my assessment a little?
What is it that definitively makes the diagnosis of STEMI in this case?

Cheers!

Ed

Here was my response:

Ed,
Good call!


There are several features:
First, as you said, there is a nearly straight ST segment.  It is very rare to have non-concavity (convex or straight) in any one of leads V2-V6 in normal variant ST elevation
Second, the QT appears slightly long for early repol.  Remember early repol is called early repol because repolarization comes early (relatively short QT)
Third, there is not enough R-wave amplitude in V4 for the T-wave size
Fourth, there is not enough QRS amplitude in V2 for that T-wave size.




The 3- and 4-variable formulas take the second, third, and fourth issues into account (see below):

Leads III and aVL are indeed somewhat suspicious; however, there really is no ST depression in III and a negative T-wave is normal, especially in the presence of a negative QRS (QRST angle is very small, less than 30 degrees)


Thanks for sending!

Steve
_______________________

One more comment: I would not call it a STEMI, as this diagnosis is associated with ST Elevation "criteria" which this ECG does not meet.  One might call it:


1. Subtle STEMI

2. "Semi-STEMI"
3."Subtle occlusion" (in this case, subtle LAD occlusion)

Formulas use the following measurements
QTc =  (manually measured)                                                      = 400 ms  
ST Elevation at 60 ms after the J-point in lead V3 (STE60V3) = 2.5 mm
R-wave amplitude in V4 (RAV4)                                               = 9.5 mm
QRS amplitude in V2 (QRSV2)                                                 = 17 mm.

3-variable (STE60V3, RAV4 and QTc) = 23.48 (greater than 23.4 predicts LAD occlusion)
4-variable (adds QRSV2)                       =18.34 (greater than 18.2 predicts LAD occlusion)

These 2 cutoffs are the most accurate, not the most sensitive, nor the most specific.  

At 23.4, 3-variable formula had sens, spec, and acc of 86%, 91% and 88%

At 18.2, 4-variable formula had sens, spec, and acc of 89%, 95%, and 92%

The 4-variable is better for both but only in a derivation sample (needs validation!  Anyone??).

The patient did indeed have an LAD occlusion.

Final note on T-wave size: how do the formulas take T-wave size into account??   In our study, T-wave amplitude was not significantly greater for LAD occlusion vs. normal variant ST elevation (early repol also has large T-waves).  But large T-waves are only normal when there is high QRS voltage, as in normal variant.  ST elevation at 60 ms after the J-point is a measure of the slope of the ST segment; the higher the STE60V3, the steeper the slope. A steep slope correlates with a large T-wave and a flat slope with a smaller T-wave. 


Links to articles

3-variable formula: http://www.annemergmed.com/article/S0196-0644(12)00160-6/pdf


4-variable formula: http://www.jecgonline.com/article/S0022-0736(17)30107-3/pdf







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