What is the diagnostic approach for pericarditis?

Diagnostic Approach for Pericarditis

Diagnose acute pericarditis when at least 2 of 4 clinical criteria are present: pericarditic chest pain, pericardial friction rub, new widespread ST-elevation or PR depression on ECG, or new/worsening pericardial effusion. 1

Core Diagnostic Criteria (Need ≥2 of 4)

1. Pericarditic Chest Pain (~90% of cases)

• Sharp, pleuritic, retrosternal pain that worsens with inspiration and when lying supine 2, 3
• Characteristically improves when sitting forward 2
• Present in approximately 90% of acute pericarditis cases 3

2. Pericardial Friction Rub (<30% of cases)

• Highly specific auscultatory finding representing friction between inflamed pericardial layers 2, 4
• Listen at the left lower sternal border 5
• Critical caveat: This finding is transient and reported in only 18-84% of cases, so its absence does not exclude pericarditis 4

3. ECG Changes (25-60% of cases)

• New widespread ST-segment elevation with upward concavity (without reciprocal changes) 1, 2
• PR-segment depression in multiple leads 1, 4
• Important limitation: ECG changes occur in only 60% of cases, and up to 40% may have normal ECGs 1, 2
• Must differentiate from acute coronary syndrome (which shows reciprocal changes and localized ST elevation) and early repolarization 1

4. Pericardial Effusion (~60% of cases)

• New or worsening fluid collection detected by imaging 1, 2
• Most effusions are small 3

Mandatory Initial Workup

All patients with suspected pericarditis require: 1, 2

• ECG (Class I recommendation) - to identify characteristic changes and exclude acute coronary syndrome 1, 6
• Transthoracic echocardiography (Class I recommendation) - to detect effusion, assess size, and evaluate for tamponade 1, 2
• Chest X-ray (Class I recommendation) - though typically normal unless effusion exceeds 300 mL 1

Supporting Laboratory Tests

• Inflammatory markers: CRP, ESR, and white blood cell count are commonly elevated and useful for monitoring disease activity and treatment response 1, 2
• Cardiac biomarkers: Troponin and creatine kinase (CK) should be assessed to detect concomitant myocarditis 1, 2
• Critical caveat: Normal inflammatory markers do not exclude pericarditis, especially if the patient is already on anti-inflammatory treatment 2

Advanced Imaging (When Indicated)

• CT or cardiac MRI provide additional supporting evidence when diagnosis remains uncertain 1, 2
• Consider for complicated cases or when evaluating for specific etiologies 1

Common Diagnostic Pitfalls

• ECG may be normal in 40% of cases - do not rely solely on ECG findings 2
• Pericardial rub is transient - absence does not exclude diagnosis 4
• Troponin elevation indicates myopericarditis, not just pericarditis alone 1, 2
• Chest X-ray is insensitive - cardiothoracic ratio increases only with effusions >300 mL 1

Temporal Classification After Diagnosis

Once diagnosed, classify by duration: 1

• Acute: Initial presentation
• Incessant: >4-6 weeks but <3 months without remission
• Recurrent: New episode after symptom-free interval of ≥4-6 weeks
• Chronic: >3 months duration