I think there is a lot to be said for going back to the start of a knowledge base and reviewing the basics again.

(You might find this especially useful as a backgrounder if you were about to transition from 3-lead to interpreting 12-lead ECG)

Here’s an excellent presentation (especially the first 37 minutes !) from the Louisville Lectures which will take you through coronary perfusion, ECG interpretation and STEMI;

https://www.blubrry.com/louisvillelectures/11193829/acute-coronary-syndromes-101-with-dr-brown