STEMI and ST Depressions in Trans-Endocardial Ischemia

In a STEMI, there's no normal non-eschemic tissue between the ischemic biocardium and the electrodes on the skin. With sub-endocardial ischemia, which is non-transmural, there is by definition some non- eschemic tissue around the EKG electrode. So you actually end up with the opposite result of what happens in a STEMI. And that leads to a lowering of the baseline EKG and the appearance of ST elevation, which is really kind of an illusion.