How do ST elevations differ between STEMI due to myocardial infarction and diffuse ST elevations due to pericarditis?

• A. STEMI shows diffuse, convex ST elevations; pericarditis shows focal ST elevations with reciprocal changes
• B. STEMI shows focal ST elevations with reciprocal changes; pericarditis shows diffuse concave ST elevations with PR depression
• C. STEMI shows diffuse ST elevations with PR depression; pericarditis shows focal ST elevations with reciprocal changes
• D. STEMI shows focal ST elevations with PR depression; pericarditis shows diffuse ST elevations with PR depression

Answer: (B)

The main idea is recognizing how the ST elevations differ in location and shape between a true transmural infarction and pericarditis. In a STEMI, the injury affects a specific coronary territory, so the ST elevations are focal to that region and you often see reciprocal ST depressions in leads opposite the involved area. In pericarditis, the inflammatory process involves the whole pericardium, leading to diffuse ST elevations across many leads, and these elevations tend to be concave upward with accompanying PR-segment depression (often with PR elevation in aVR).

So, the best description is that STEMI shows focal ST elevations with reciprocal changes, while pericarditis shows diffuse, concave ST elevations with PR depression.