There is very minimal ST elevation in aVL (less than 1 mm). Now look at V2 where there is less than 1 mm of ST elevation. This cannot be normal (early repol) because there is a Q-wave. Also, the QTc is 483 ms. This is very suspicious for an LAD occlusion or subtotal occlusion.
The cath lab was activated and there was an 80% occlusive thrombus in the proximal LAD with TIMI II flow. A post cath ECG (below) shows even more ST elevation, with loss of R-wave in V2, and a much deeper Q-wave.
This was a very large territory at risk. The post-PCI ejection fraction was 40%, where it was normal before. The convalescent EF was 53%.
Even with a very subtle ECG, without the "required" 1 mm of ST elevation, there may be a subtotal coronary occlusion with very much myocardium at risk of permanent infarction.
In my study of 355 consecutive proven LAD occlusions, of which 212 were excluded because they were electrocardiographically obvious, there were 143 remaining consecutive electrocardiographically subtle proven total LAD occlusions. Of these 143, 17 (12%) had a mean (V2-v4) ST elevation at the J point of less than 1 mm and 14 (10%) had a mean equal to 1 mm. Thus, 22% of these subtle LAD occlusions, or at least 9% of all LAD occlusions, had a mean STE less than or equal to 1 mm. 19 had no lead with more than 1 mm and 8 had less than or equal to 1 mm in only one lead.
Low R-wave amplitude was a better predictor of LAD occlusion than was ST elevation. QTc was very helpful as well. I have published several abstracts on this and am in the process of analyzing the data for a full manuscript.
In subtotal occlusions such as this one, the proportion with such subtle ST elevation is much higher.