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Differentiating STEMI from Pericarditis

May 22, 2020

Written by Aaron Lacy

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While some overlap exists, ST elevation in lead III>II and ST segment depressions in various leads suggests STEMI, while PR depression and Spodick’s signs (downsloping T-P segment) are most suggestive of pericarditis.

Why does this matter?
In patients with chest pain and ST elevation, it is critical to differentiate between STEMI and pericarditis quickly in order to facilitate appropriate activation of the cath lab.

Cath lab or no cath lab?
This case-control study evaluated specific EKG findings in 207 patients with ST elevation and chest pain to determine changes associated with either STEMI or pericarditis (STEMI: n = 165, pericarditis: n = 42). The addressed EKG changes and results are in the table below. 

OR favors STEMI over pericarditis. ECGs from cited article. Table adapted from cited article.

In this study, the presence of ST segment depressions (in various leads, excluding aVR and V1) and ST elevation in lead III > II were the best discriminators pointing toward a diagnosis of STEMI. Presence of PR depression was the best discriminator pointing toward a diagnosis of pericarditis. However, PR depression was present in 12% of STEMIs, and Spodick’s sign was present in 5% of STEMI patients. In fact, every ECG finding had overlap between the two diagnoses.

This was a small, single-center study, but is an excellent review of some of the unique ECG findings associated with both STEMI and pericarditis. The big takeaway here is that there is no pathognomonic finding for either STEMI or pericarditis, and one should use caution before using a single finding to anchor on a diagnosis.

In his weekly ECG teaching series, senior author – Amal Mattu, recommends searching for signs to rule in STEMI on ECGs with ST elevation in the following steps before looking for any ECG changes associated with pericarditis:

  1. Search for ST depression (aside from leads aVR and V1)

  2. Look for ST elevation in lead III > II

  3. Search for horizontal or convex upward ST elevation

Then, and only then, should you explore the other options for diagnosing pericarditis.

Evaluation of Spodick’s Sign and Other Electrocardiographic Findings as Indicators of STEMI and Pericarditis. J Emerg Med. 2020 Mar 25. pii: S0736-4679(20)30020-2. doi: 10.1016/j.jemermed.2020.01.017. [Epub ahead of print]

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