STEMI vs Pericarditis

STEMI vs Pericarditis

Resident Clinical Pearl – September 2016

Jacqueline Mackay, PGY3 iFMEM, Dalhousie University, Saint John, New Brunswick

Reviewed by Dr. David Lewis

It’s 11 pm on a busy ED shift. You have just seen a 58 year old male with chest pain. It’s been coming and going for a few days, sometimes at rest. He’s also complaining of shortness of breath and diaphoresis.

This is the ECG:



STEMI? or Pericarditis?

Pericarditis is inflammation of the pericardium (often following viral infection but there are many other causes) that can cause the following symptoms: chest pain (pleuritic, positional, radiating to left shoulder), tachycardia, and dyspnea. There may be an an associated pericardial friction rub or evidence of pericardial effusion (muffled heart sounds or visible on PoCUS). Widespread ST segment changes are seen on ECG due to involvement of epicardial tissue.


The diagnosis of acute pericarditis requires at least two of:

1.    Chest pain consistent with pericarditis

2.    Pericardial friction rub

3.    Typical ECG changes

4.    Pericardial effusion (larger than trivial)


There are no studies that have determined clear diagnostic criteria. One of the biggest pitfalls in the diagnosis and treatment of pericarditis is misinterpretation of the ECG. The ECG is not always a classic presentation, and it is important to look for any ECG changes that RULE-IN STEMI.


How to distinguish Pericarditis from STEMI on ECG:

Three questions:

1.    Is there ST depression in a lead other than aVR or V1? If YES, it’s a STEMI

2.    Is there convex up or horizontal ST elevation? If YES, it’s a STEMI

3.    Is the ST elevation in lead III greater than the ST elevation in lead II? If YES, it’s a STEMI



If you are able to answer NO to ALL of the above: THEN look for PR depression in MULTIPLE leads and a (usually transient) friction rub. PR depression is NOT specific for pericarditis.




Bottom Line:

ECGs can be tricky Look for ECG changes that rule-in STEMI. Think pericarditis when there is diffuse ST elevation. And if you are unsure, perform serial ECGs on any patient with chest pain!



  1. Pericarditis vs STEMI by Amal Mattu


  3.  LeWinter MM, et al. Clinical practice. Acute pericarditis. N Engl J Med. 2014 Dec 18;371(25):2410-6. PMID: 25517707


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