Most Common Imaging Findings in Pericarditis
EKG Findings
The most common EKG finding in acute pericarditis is widespread concave ST-segment elevation with PR-segment depression, though these classic changes appear in only 25-60% of cases. 1, 2
Classic Four-Stage ECG Evolution
The European Society of Cardiology describes the temporal progression through four distinct stages, though this evolution is highly variable between patients and affected by treatment 1:
Stage I (Acute): Anterior and inferior concave ST-segment elevation with PR-segment deviations opposite to P polarity 1, 2
Early Stage II: ST junctions return to baseline while PR segments remain deviated 1, 2
Late Stage II: T waves progressively flatten and invert 1, 2
Stage IV: ECG returns to pre-pericarditis state, though permanent T wave changes occasionally persist 1, 2
Critical Diagnostic Nuances
ECG changes reflect epicardial inflammation, not pericardial inflammation itself, since the parietal pericardium is electrically inert 1, 2
The absence of ECG changes does NOT rule out pericarditis—up to 40-75% of patients may have normal or atypical ECGs 1, 2, 3
Serial ECGs are essential as changes evolve rapidly and may be normal at initial presentation 3
Key Differentiating Features from STEMI
The concave upward ST elevation without reciprocal changes distinguishes pericarditis from myocardial infarction, which typically shows convex ST elevation with reciprocal depression 2, 4:
In lead V6, pericarditis is likely if the J point is >25% of the T wave apex height (using PR segment as baseline) 1, 2
The ratio of ST-segment elevation to T wave >0.24 in lead V6 suggests pericarditis 4
Pericarditis shows diffuse ST elevation across multiple territories without respecting coronary distributions 4
Common Pitfalls
PR depression with multilead ST elevation can occur in left circumflex artery occlusion, mimicking pericarditis 5
Early repolarization (ERSTE) commonly presents with diffuse ST elevation and ST depression in aVR, even with PR depression, but without clinical symptoms of pericarditis 6
QRS widening and QT interval shortening in leads with ST elevation suggest STEMI rather than pericarditis 5
Chest X-Ray Findings
Chest X-ray is generally normal in acute pericarditis and should not be relied upon for diagnosis. 1
Specific Findings
The cardiothoracic ratio remains normal unless pericardial effusion exceeds 300 mL 1
When large effusions are present, the classic "water bottle" heart shadow may appear 1
Chest X-ray is primarily useful for detecting pleuro-pulmonary diseases with signs of pleuropericardial involvement 1
Additional pulmonary or mediastinal pathology may be revealed that suggests underlying etiology 1
Essential Complementary Testing
Since imaging findings are often absent or non-specific, diagnosis requires integration with clinical criteria 1:
Transthoracic echocardiography is mandatory to detect effusion, assess for tamponade, and evaluate concomitant cardiac disease 1, 2
Blood analyses should include inflammatory markers (CRP, ESR, WBC) and myocardial injury markers (troponin I is detectable in 49% of acute pericarditis patients with ST elevation) 1, 2
Cardiac CT or MRI may be necessary in complicated cases to identify pericardial inflammation, particularly in atypical presentations 3, 7