Steps to distinguish pericarditis from STEMI:   Is there ST depression in a lead other than AVR or V1?  This is a STEMI   Is there convex up or horizontal ST elevation?  This is a STEMI   Is there ST elevation greater in III than II?  This is a STEMI   Now look for PR depression in multiple leads… this suggests pericarditis (especially if there is a friction rub!)  From Life in the Fast Lane