PECARN Head CT and Pericarditis vs. STEMI… in a Rush

5-Minute Journal Article (PECARN Head CT Rule)

Dr. Brian Yu did a great 5-minute summary on the PECARN head CT Rule that was published in 2009. It’s an ambitious study that involved 25 emergency departments and included 42,412 patients under the age of 18 years who presented with blunt head trauma. It further risk stratified these patients into 2 major cohorts of <2 years of age and 2-18 years of age. It excluded patients with trivial injury, penetrating trauma, neurologic history, and those with prior imaging. The outcomes this study aimed for were clinically important findings including death, need for neurosurgical intervention, intubation >24 hours, and admission >2 nights. 

Using these 42,412 patients, they were able to identify 7 predictors that could safely predict a patient not needing a Head CT, which can be seen below.

This study had a NPV 100% in <2 years of age and NPV 99.95% in 2-18 years of age. It’s also important to note on the <2 yoa flowsheet that infants <3 months are part of the “shared dicision-making” that may sway you to imaging. Also that the severe mechanism of injury in this cahort is a fall of 3 feet which could be from the height of a bed or from being held in arms. Lastly, it’s important to note that the risk of cancer from CT radiation in pediatrics is estimated at around 1 in 5,000. Therefore, we can use these risks when discussing our rationale for imaging with our patients.


5-Minute EKG (Pericarditis vs. STEMI)

Dr. Patwari did a great review on differentiating ST elevations associated with pericarditis vs. acute MI

From medical school, I think we can recall many of the classic EKG findings that support pericarditis

Diffuse ST elevations
Concave upwards STE
PR depressions in multiple leads (only reliable seen in viral pericarditis)
PR elevation in aVR

However, when ruling in pericarditis, one of the most important things we can do is to rule out STEMI. Some factors that support STEMI over pericarditis are:

STE III> STE II (very strongly favors STEMI)
STD in leads other than aVR or V1 (suggests reciprocal changes of acute MI)
Precence of new Q waves
STE convex upwards or horizontal favors STEMI

The below EKG has the classic findings of pericarditis:  diffuse ST elevations, PR elevation in aVR, STE in lead II>lead III. The ST elevation morphology is also concave.

Classic Pericarditis EKG

The below EKG shows many of the factors that support MI over pericaditis including:  ST elevations in specific coronary artery pattern (inferior leads), ST elevations in lead III>lead II, and reciprocal ST depressions in lateral leads.

Inferior STEMI

And as a reminder of ST elevation morphology… concave STE makes a happy face while convex STE makes a frowny face (or a tombstone). Again, note that STEMI can have all 3 morphologies, while pericarditis will typically only have concave ST elevations. LITFL has a good review of ST elevation morphologies with ST elevation differential (LITFL STE)


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