What are the steps to diagnose pericarditis in a patient presenting to the Emergency Room (ER) with chest pain?

Diagnosing Pericarditis in the Emergency Room Setting

The diagnosis of pericarditis in a patient presenting to the Emergency Room with chest pain requires meeting at least 2 of 4 key diagnostic criteria: pericarditic chest pain, pericardial friction rub, widespread ST-elevation or PR depression on ECG, or new/worsening pericardial effusion. 1

Initial Assessment

• Obtain a focused history looking for characteristic pleuritic chest pain that may be sharp, increases with inspiration, and improves when sitting up or leaning forward 1
• Perform a physical examination focusing on the presence of fever and listening for a pericardial friction rub, which is highly specific but often transient, reported in 18-84% of cases 2
• Order an ECG within 10 minutes of arrival to evaluate for characteristic changes of pericarditis 1
• Measure inflammatory markers including C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count 1
• Check cardiac biomarkers (troponin, CK) to assess for myocardial involvement, which may indicate myopericarditis 1

Diagnostic Criteria for Pericarditis

To diagnose acute pericarditis, at least 2 of the following 4 criteria must be present 1, 2:

1. Pericarditic chest pain: Typically sharp, pleuritic, improves when sitting up/leaning forward 1
2. Pericardial friction rub: A scratching sound best heard at the left sternal border 1
3. ECG changes: New widespread ST-elevation (typically concave upward) or PR depression 1
4. Pericardial effusion: New or worsening effusion on imaging 1

Key Diagnostic Tests

1. Electrocardiography (ECG)

• Order immediately upon presentation with chest pain 1
• Look for characteristic changes 1, 3:
  • Widespread ST-segment elevation (concave upward) without reciprocal changes
  • PR-segment depression
  • Four stages may evolve over time, though not all patients progress through all stages 4

2. Echocardiography

• Transthoracic echocardiography (TTE) should be performed in all patients with suspected pericarditis 1, 2
• Evaluate for 1:
  • Presence and size of pericardial effusion
  • Ventricular wall motion abnormalities
  • Signs of tamponade (right ventricular diastolic collapse, right atrial collapse)
  • Restrictive physiology

3. Laboratory Tests

• Order inflammatory markers: CRP, ESR, white blood cell count 1
• Check cardiac biomarkers (troponin, CK) - elevated in approximately 27% of cases, indicating myocardial involvement 3
• Consider additional testing based on clinical suspicion of specific etiologies 1:
  • Autoimmune markers (ANA, ENA, ANCA) if autoimmune disease suspected
  • Tuberculosis testing (IGRA) if TB suspected
  • Viral PCR studies if viral etiology suspected

4. Additional Imaging

• Chest X-ray to evaluate for cardiomegaly (with large effusions) and to rule out other causes of chest pain 1
• Consider cardiac MRI or CT in cases where diagnosis remains uncertain 1:
  • CMR can detect pericardial inflammation, thickening, and late gadolinium enhancement
  • CT can identify pericardial thickening or calcification

Differential Diagnosis Considerations

• Acute coronary syndrome - differentiated by ECG pattern (ST elevations in pericarditis are typically diffuse and concave upward without reciprocal changes) 4, 5
• Myocarditis - may coexist as myopericarditis 4
• Pulmonary embolism - different pain characteristics and ECG findings 1
• Pneumothorax - different clinical presentation and findings on chest X-ray 1
• Aortic dissection - typically presents with severe, tearing pain 1

Common Pitfalls and Caveats

• Relying solely on ECG findings can be misleading as some patients with pericarditis may have atypical or normal ECGs 5
• Pericardial friction rubs are highly specific but often transient and may be missed 2
• Elevated troponin does not necessarily indicate worse prognosis but suggests myocardial involvement (myopericarditis) 3
• Clinical presentation has evolved over time - classic descriptions (fever, friction rub) are often absent in modern presentations 3
• Misdiagnosis as acute myocardial infarction is common due to similar ECG changes and chest pain 4, 3

Risk Stratification

Patients with any of these high-risk features should be considered for hospital admission 1:

• Fever >38°C
• Subacute onset (symptoms developing over several days/weeks)
• Large pericardial effusion (>20mm)
• Cardiac tamponade
• Failure to respond to NSAIDs
• Elevated troponin (indicating myocardial involvement)
• Immunosuppressed state

By following this systematic diagnostic approach, clinicians can accurately diagnose pericarditis in patients presenting to the ER with chest pain, while avoiding common diagnostic pitfalls.