A 78 yo male had a syncopal event and complained of chest pain.

Here are 9 prehospital ECGs during transport:

0 minutes, nondiagnostic

4 minutes, inferior STEMI (subtle).

5 minutes, reperfused, barely shows on the ECG

7 minutes, almost normal again.

15 minutes, more obvious

16 minutes, more obvious, NTG given here

22 min, with V4R, STE gone after NTG and Aspirin

23 minutes, very subtle, resolving

29 minutes, almost entirely resolved

The cath lab was activated prehospital and the patient received an RCA stent and an LAD stent, had a minimal troponin rise, and did well.

This shows how acute coronary syndrome is very dynamic, with arteries opening and closing.  Studies using continuous 12-lead monitoring show that this happens even in the abscence of chest pain.