How to distinguish pericarditis from STEMI

Diffuse, convex (up) ST segment elevations with or without PR-segment depressions can be seen in both pericarditis or ST-segment Elevation Myocardial Infarction (STEMI), particularly if the patient has a wraparound LAD which supplies the inferior wall. So how can one reliably distinguish pericarditis from STEMI?

The Solution

If any of the following are present, a STEMI is more likely:

• reciprocal ST depressions in any leads other than V1 or aVR. Pay particular attention to aVL which, in patients with inferior wall STEMI, may show T-wave inversion or  extremely subtle reciprocal ST depression.
• straight or concave (“tombstone”) ST segments
• QR-T complexes (“checkmark sign”)

• ST segment more elevated in Lead III than in Lead II
• fragmented QRS (fQRS) complexes
• worsening or new Q-waves
• Prolonged QTc is often seen with STEMI.

Only if none of the above are present, then the following increases the likelihood of pericarditis:

• Downsloping of TP-segment, or of entire QRSTP segment, particularly in Lead II (Spodick’s sign)
• PR-segment depressions in multiple leads (seen in viral pericarditis).
  

Myths and Realities

Myth: only pericarditis causes convex (up) ST segments
Reality: Convex ST segments can be seen in STEMI as well

Myth: pericarditis causes only defuse ST elevations
Reality: Pericarditis causes localized ST elevations as well

Myth: only pericarditis causes defuse ST elevations
Reality: diffuse ST elevations can be see in STEMI as well

Myth: only pericarditis causes PR depressions
Reality: PR depressions are common in STEMI as well

Myth: only pericarditis causes PR segment elevation in aVR.
Reality: PR segment elevation in aVR can be seen in STEMIs as well

Myth: pericarditis can be almost always be distinguished from STEMI on EKG
Reality: a single EKG is often insufficient. Tough cases may require serial, history and physical examinations, electrocardiograms, troponins, an echocardiograms and sometimes cardiac catheterization.

References

• The checkmark sign is a screenshot from a video by Dr. Mattu.
• Dr. Smith’s ECG Blog here, here, here, and here.