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!
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 STEMI2. “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