Diagnostic Criteria for Pericarditis
Acute pericarditis is diagnosed when at least 2 of the following 4 criteria are present: pericarditic chest pain, pericardial friction rub, new widespread ST-elevation or PR depression on ECG, or new/worsening pericardial effusion. 1, 2
Core Diagnostic Criteria (≥2 Required)
1. Pericarditic Chest Pain (~90% of cases)
- Sharp, pleuritic chest pain that is retrosternal and worsens with inspiration 2, 3
- Characteristically improves when sitting forward and worsens when lying supine 3
- Must be distinguished from acute coronary syndrome 1
2. Pericardial Friction Rub (<30-84% of cases)
- Highly specific auscultatory finding representing friction between inflamed pericardial layers 2, 4
- Best heard at the left lower sternal border 5
- Important caveat: This finding is transient and may be absent in many cases 4
3. ECG Changes (25-60% of cases)
- New widespread ST-segment elevation with upward concavity in multiple leads 1, 2
- PR-segment depression in multiple leads 1, 4
- Critical pitfall: ECG changes may be absent in up to 40% of cases, so their absence does not exclude pericarditis 2
- Must differentiate from acute coronary syndromes with ST-elevation and early repolarization patterns 1
4. Pericardial Effusion (~60% of cases)
- New or worsening fluid collection detected on imaging 1, 2
- Most effusions are small 3
- Chest X-ray typically normal unless effusion exceeds 300 mL 1, 2
Additional Supporting Findings
Inflammatory Markers
- Elevated C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count are common 1, 6, 2
- These markers are helpful for monitoring disease activity and treatment response 1
- Important caveat: Normal inflammatory markers do not exclude pericarditis, especially if the patient is already on anti-inflammatory treatment 2, 7
Cardiac Biomarkers
- Troponin and creatine kinase (CK) should be assessed 1, 6, 2
- Critical distinction: Elevation indicates concomitant myocarditis (myopericarditis) rather than primary pericardial disease 1, 2
Recommended Diagnostic Workup
Mandatory Initial Tests (All Patients)
- ECG 1
- Transthoracic echocardiography 1, 4
- Chest X-ray 1
- CRP and ESR 6, 2
- Complete blood count with differential 6, 7
- Cardiac biomarkers (troponin, CK) 1, 6
- Renal and liver function tests 6, 7
Advanced Imaging (When Indicated)
- CT or cardiac MRI for additional pericardial characterization 1
Temporal Classifications
Acute Pericarditis
- Meets ≥2 of the 4 core criteria 1
Incessant Pericarditis
- Duration >4-6 weeks but <3 months without remission 1
Recurrent Pericarditis
- New episode after documented symptom-free interval of 4-6 weeks or longer 1
Chronic Pericarditis
- Duration >3 months 1
Common Diagnostic Pitfalls
- ECG changes reflect epicardial inflammation, not pericardial inflammation directly, since the parietal pericardium is electrically inert 1
- The temporal evolution of ECG changes is highly variable and affected by therapy 1
- Pericardial friction rub is highly specific but may be missed due to its transient nature 4
- Do not require all 4 criteria—only 2 are needed for diagnosis 1, 2