Diagnostic Criteria for Pericarditis
Acute pericarditis is diagnosed when at least 2 of the following 4 criteria are present: (1) pericarditic chest pain, (2) pericardial friction rub, (3) new widespread ST-elevation or PR depression on ECG, or (4) new or worsening pericardial effusion. 1
Core Diagnostic Criteria
The 2015 European Society of Cardiology (ESC) guidelines establish the definitive diagnostic framework, requiring at least 2 of 4 criteria for diagnosis: 1
Pericarditic chest pain: Sharp, pleuritic chest pain that worsens with inspiration and improves when sitting forward, often radiating to the neck, back, or left shoulder. Present in approximately 90% of cases. 2, 3
Pericardial friction rub: A scratchy, high-pitched sound heard best at the left lower sternal border, representing friction between inflamed pericardial layers. Highly specific but transient, reported in 18-84% of cases (commonly around 33%). 1, 3, 4
ECG changes: New widespread ST-segment elevation (with upward concavity) or PR-segment depression across multiple leads, not confined to a single coronary territory. Present in only 60% of cases, so absence does not exclude diagnosis. 1, 5
Pericardial effusion: New or worsening fluid collection detected on imaging (echocardiography is first-line). Present in approximately 60% of cases. 1, 2
Supporting Diagnostic Findings
While not required for diagnosis, these findings strengthen clinical suspicion and help monitor disease activity: 1
Elevated inflammatory markers: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count are commonly elevated and useful for monitoring treatment response. 1, 6
Advanced imaging: CT with IV contrast or cardiac MRI can demonstrate pericardial inflammation, though echocardiography remains first-line. Cardiac MRI has 94-100% sensitivity for detecting pericardial inflammation. 6, 5
Cardiac biomarkers: Troponin or creatine kinase (CK) elevation indicates concomitant myocarditis (termed "perimiocarditis"), found in up to 50% of acute pericarditis cases. 1, 2
Temporal Classification
Understanding the temporal patterns is essential for management: 1
- Acute pericarditis: New episode meeting diagnostic criteria
- Incessant pericarditis: Lasting >4-6 weeks but <3 months without remission
- Recurrent pericarditis: New episode after symptom-free interval of ≥4-6 weeks
- Chronic pericarditis: Lasting >3 months
Diagnostic Algorithm
Step 1: Obtain ECG immediately in all patients with suspected pericarditis, looking for widespread ST elevation and PR depression. 6, 5
Step 2: Perform transthoracic echocardiography in all patients to detect effusion, assess size, and evaluate for tamponade. This is the first-line imaging modality. 1, 6
Step 3: Check inflammatory markers (CRP, ESR, WBC) and cardiac troponins to assess for myocardial involvement. 6, 5
Step 4: Obtain chest X-ray, though it is typically normal unless effusion exceeds 300 mL. 1
Step 5: Consider cardiac MRI if diagnosis remains uncertain or myocardial involvement is suspected, as it has superior sensitivity (94-100%) for detecting inflammation. 6, 5
Critical Pitfalls and Caveats
ECG changes are absent in up to 40% of cases, so do not rely solely on ECG findings. The diagnosis can be made with other combinations of the 4 criteria. 1, 6
Distinguish from acute coronary syndrome: Pericarditis shows widespread (not localized) ST elevation with upward concavity, whereas MI shows convex ST elevation in specific coronary distributions with reciprocal changes. 1, 5
Normal inflammatory markers do not exclude pericarditis, especially if the patient is already on anti-inflammatory treatment. 6
Troponin elevation indicates myocardial involvement (perimiocarditis), not just pericardial disease, and should prompt consideration of cardiac MRI. 1, 5
Pericardial friction rubs are highly specific but transient, so their absence does not exclude the diagnosis. They may disappear within hours to days. 3, 4
Chest X-ray has limited sensitivity for pericarditis and only shows cardiomegaly when effusion exceeds 300 mL. 1