Pericarditis

Pericarditis commonly causes EKG changes (it is one of the 4 diagnostic criteria for pericarditis). Classically, one hears diffuse concave ST elevations with PR depressions with PR elevation and ST depression in aVR. Although this is true, pericarditis can be serial changes over a period of days to weeks that one should be aware of. Sinus tachycardia is also commonly seen. 

Stage 1 has the aforementioned changes. This is usually seen in the first couple of weeks, so is usually noted by the ED providers as this is what we most commonly will see. Stage 2 is typically with normalization of the ST segment, though the T waves can then become flattened. Stage 3 then develops after about 3 weeks with flattened T waves becoming inverted. Stage 4 then tends to occur after about 1 month and is resolution of the EKG abnormalities.

However, most patients do not follow through these stages and, as mentioned above, we most commonly see the first stage as patients tend to present within the first week or couple of weeks.

Pericarditis should be differentiated from OMI and early repolarization, though this is not always easy. 

"You diagnose pericarditis at your own peril" is a common (and smart) statement as patients can be incorrectly diagnosed and an OMI missed. I am personally comfortable diagnosing pericarditis independently in patients with a history of the same, typical presentation of priors, and EKG that is consistent with prior pericarditis. I will often speak to cardiology if this is not true, describing what I believe to be pericarditis but to have them weigh in to make sure they do not want an emergent catheterization before dispositioning the patient. The ST segment morphology should not be flat or convex in pericarditis. One can see PR depression in MI as this can be from atrial infarction. ST elevation in III>II is much more suggestive of an OMI vs pericarditis. Although pericarditis classically causes diffuse findings, it can cause more focal findings; however, pericarditis should not cause reciprocal changes. Patients with myopericarditis can have other nonspecific ST-T changes that cannot reliably be differentiated from ACS based on EKG findings alone. As mentioned above, patients with pericarditis commonly have tachycardia; patients with OMI rarely have tachycardia unless they have cardiogenic shock. 

It can be difficult to differentiate pericarditis from early repolarization in some cases, especially as they both cause concave ST elevation. Pericarditis does not commonly cause J point notching. The other main way to differentiate them is comparing the amplitudes of the ST segment to the T wave in V6. Pericarditis usually has a higher ST/T wave ratio with a cutoff of >0.25 suggestive of pericarditis.

Examples:

Further Reading:

https://litfl.com/pericarditis-ecg-library/

http://hqmeded-ecg.blogspot.com/search/label/pericarditis