Finally the truth about PR segments and pericarditis…a source of myth and malpractice you can avoid in 20 minutes.

Pericarditis - typically has diffuse ST-segment elevation (STE) that are concave (upward) in appearance without reciprocal ST-segment depression (STD).

STEMI - typically presents with STE that is convex or horizontal but CAN also present with STE that is concave in morphology.

If the answer is not clear, use the following algorithm

Pericarditis vs. STEMI

• First make sure you are not missing an acute MI by looking for factors strongly associated with AMI. Ask yourself:

1. Is there reciprocal ST-segment depression in any leads (except for aVR and V1)? If there is, it’s a STEMI. If not,…

2. Is the ST-segment morphology convex or horizontal? If so, it’s a STEMI. If not,…

3. Is the STE in lead III> the STE in lead II? If that’s true, it’s a STEMI.​​​

• If the answer to all three questions is NO, then you should consider the possibility of it being pericarditis. Factors associated with pericarditis:

1. Is there pronounced PR-segment depression in all leads?​ If so, it’s possibly pericarditis. (But could also be due to cardiac ischemia, so make sure you are not missing an MI first by answering the first 3 questions!)

2. Is there a pericardial friction rub?

• ​If so, it’s possibly pericarditis

When in doubt, do serial ECG’s!