The difference between Left Main occlusion and Left Main insufficiency

There are many publications stating that ST elevation in lead aVR, with diffuse ST depression elsewhere, is due to "left main occlusion."  This is even stated in the lastest 2013 ACC/AHA STEMI guidelines, and they reference an article by Jong et al. (Int Ht J 2006; 47(1):13-20.) as evidence.  If you go read that article, "occlusion" was defined as any stenosis greater than 50%.  That is not occlusion, which is 100%.  There are many other articles that confuse Left Main occlusion with Left Main insufficiency, and these are the sources of the mistaken belief that this ECG pattern reflects LM occlusion:There is diffuse ST depression, with ST elevation in aVR.  This is diffuse subendocardial ischemia.  The ST elevation in aVR is reciprocal to the ST depression.  The ST depression vector is directed anterior, lateral, and inferior (towards leads II and V5), so the opposite of this is towards aVR.  Hence ST elevation in aVR.  The angiogram image is below.Here is the angiogram:There is a very tight stenosis that limits the blood flow, but there is clearly flow in all the arteries supplied by the left main. This limitation causes subendocardial ischemia with ST depression, but not transmural ischemia with ST elevationThe subendocardium is more susceptible to ischemia than the epicardium due to its proximity to the high pressure LV chamber and also because of its distance from the epicardial coronary arteries (the arteries th...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs