Straight to the Cath lab and we found a pinhole distal left main, as well as a severe focal proximal/mid stenosis in a large type IV LAD which subtended the mid and distal half of the inferior wall! With this anatomy I wouldn’t have expected survival if the LMCA had completely occluded.

As you suggest it is possible that there could be focal anteroseptal transmural ischemia concurrent with global subendocardial ischemia.

Survival of complete LMCA occlusion is quite unlikely unless there is a very large super-dominant RCA subtending the inferior and lateral walls, in which case I’d also expect similar ECG findings to an ostial-prox LAD.

What is super interesting is the presence of STE in aVL, V1 and V2, as well as aVR. If it were a prox occlusion of a large LAD as the conduction disturbance suggests, I would have expected extensive anterolateral STE perhaps out to V5-6, with reciprocal inferior STD.

Sinus tachy with RBBB, and a diffuse subendocardial ischemia pattern is suggestive of a critical left main, or any other situation associated with gross coronary hypoperfusion, such as catastrophic blood loss for example.

Thank you Dr Jones for your incredibly thoughtful reply! I agree, it is a cracker! In the absence of any clinical information, my first reaction is that this patient is extremely unwell.