This 80 year old with a history of CABG had a cardiac arrest. He was resuscitated after fairly prolonged down time, but regained consciousness, though he was confused. He did not state he had chest pain, but, then again, he couldn't remember anything. Here is the prehospital ECG at 1935:
This is as clear a STEMI as you can get. Now, it is true that shortly after a non-ACS cardiac arrest, there can be transient diffuse ST depression, but not ST elevation in a coronary distribution, and there should not be a wall motion abnormality.
This was the initial ED ECG at 1951:
There was some delay in cath team arrival since it was the middle of the night, so this right sided ECG was recorded at 2010
As it turned out, the patient had an old inferoposterior MI that was scarred; this scar initiated primary V Fib arrest, which in turn resulted in temporary hypoperfusion of the inferior wall because of its very tenuous blood supply and resulting ST elevation on the ECG.
So this is classic inferoposterior STEMI on the ECG but is NOT acute coronary syndrome!
This could not have been known without the angiogram. The ECG and ultrasound could not have been differentiated from acute plaque rupture with occlusion of the RCA.