ECG Changes in Pericarditis
Acute pericarditis presents with characteristic ECG changes in four sequential stages, most notably Stage I with widespread concave ST-segment elevation in anterior and inferior leads (I, II, aVL, aVF, V3-V6) and PR-segment depression opposite to P wave polarity, though these classic findings appear in only 25-60% of cases. 1, 2
Classic ECG Evolution Through Four Stages
The European Society of Cardiology defines the temporal progression of ECG changes in pericarditis 1:
- Stage I: Anterior and inferior concave ST-segment elevation with PR-segment deviations opposite to P polarity 1
- Early Stage II: ST junctions return to baseline while PR segments remain deviated 1
- Late Stage II: T waves progressively flatten and invert 1
- Stage III: Generalized T wave inversions develop 1
- Stage IV: ECG returns to pre-pericarditis state (though occasionally permanent T wave changes persist) 1
Specific Lead Patterns
The typical lead involvement includes I, II, aVL, aVF, and V3-V6, with ST depression consistently present in aVR and frequently in V1, occasionally in V2. 1
- ST-segment depression in lead aVR is reciprocal to the widespread ST elevation and serves as a diagnostic feature 2
- The ST elevation is characteristically concave upward (distinguishing it from myocardial infarction) 1
- PR depression occurs in multiple leads while PR elevation appears in aVR 1
Critical Diagnostic Limitations
ECG changes occur in only 25-60% of pericarditis cases, making their absence insufficient to rule out the diagnosis. 2, 3
- The ECG may be completely normal at presentation or for days after symptom onset 3
- Serial ECGs can reveal specific patterns during new episodes of chest pain 3
- ECG changes reflect epicardial inflammation rather than pericardial inflammation itself, since the parietal pericardium is electrically inert 2
Diagnostic Criteria
At least 2 of 4 criteria are required for diagnosis: (1) new widespread ST-elevation or PR depression on ECG, (2) characteristic pleuritic chest pain, (3) pericardial friction rub, or (4) new/worsening pericardial effusion. 2, 4
Key Differentiating Features from Myocardial Infarction
Critical pitfall: PR depression with multilead ST elevation and ST depression in aVR can occur with left circumflex artery occlusion, mimicking pericarditis. 5
- QRS widening and QT interval shortening in leads with ST elevation suggest STEMI rather than pericarditis 5
- Pericarditis shows concave ST elevation without reciprocal changes, while MI typically shows convex ST elevation with reciprocal depression 1
- Early repolarization (ERSTE) can also mimic pericarditis with diffuse ST elevation and PR depression, but lacks clinical symptoms 6
- In lead V6, pericarditis is likely if the J point is >25% of the T wave apex height 1
Special Population: Uremic Pericarditis
In uremic patients, traditional ECG findings are less reliable, and the ECG should be obtained primarily to exclude acute coronary syndrome rather than to confirm pericarditis. 7, 2
Treatment Approach
NSAIDs are the first-line treatment (Class I recommendation), with ibuprofen preferred at 300-800 mg every 6-8 hours due to rare side effects, favorable coronary flow impact, and large dose range. 1
- Indomethacin should be avoided in elderly patients due to coronary flow reduction 1
- Colchicine 0.5 mg twice daily added to NSAIDs or as monotherapy is effective for initial attack and preventing recurrences (Class IIa recommendation) 1
- Gastrointestinal protection must be provided with NSAID therapy 1
- Systemic corticosteroids should be restricted to connective tissue diseases, autoreactive, or uremic pericarditis 1
- Treatment should continue for days to weeks, ideally until effusion disappears 1
- Hospitalization is warranted to determine etiology, observe for tamponade, and monitor treatment response 1
Essential Ancillary Testing
Transthoracic echocardiography is mandatory (Class I recommendation) in all patients to detect effusion, assess for tamponade, and evaluate concomitant cardiac disease. 1, 4