This 51 yo male presented with Chest pain.
There is ST depression, greater than 3 mm in some leads, in I-III, aVF, and V3-V6. aVR also has ST elevation.
Deep and widespread ST depression is associated with very high mortality because it signifies severe ischemia usually of LAD or left main origin.
This patient was treated with nitroglycerine, ASA, and heparin. His pain diminished substantially but did not go away altogether. An ED ultrasound showed an anterior, apical, and septal wall motion abnormality. Repeat ECG showed most of the ST depression resolved (but not all).
There is no ST elevation, no evidence of occlusion that will cause imminent necrosis of a myocardial wall. But there is evidence of a very unstable atherosclerotic plaque that could completely thrombose at any moment. Also, his ongoing pain signified ongoing ischemia, which is an indication for immediate angiography and PCI. Therefore he was taken emergently (in the evening) to the cath lab. There was a severe ostial LAD thrombosis that was very close to the left main.
He went for emergent bypass that evening and had a good outcome.
ST elevation in aVR is often thought to represent left main occlusion. However, it really just signifies widespread and diffuse subendocardial ischemia which could be due to left main or 3-vessel disease, or severe proximal LAD disease. Left Main occlusion generally causes rapid death; most who survive left main ACS have some flow and thus often have widespread ST depression.
Think of aVR as (-)aVR. (-)aVR is 180 degrees opposite aVR and thus is between leads I and II. Thus, if I and II have ST depression, the (-) aVR must have ST depression, and (+) aVR must have ST elevation.