What are the diagnostic criteria and management options for pericarditis, including laboratory tests and treatment protocols?

Diagnostic Criteria and Management of Pericarditis

The diagnosis of pericarditis requires at least 2 of the 4 following criteria: pericarditic chest pain, pericardial rubs, new widespread ST-elevation or PR depression on ECG, and pericardial effusion (new or worsening). 1

Diagnostic Criteria

Primary Diagnostic Criteria

• Pericarditic chest pain: Typically sharp, retrosternal, pleuritic chest pain that may worsen with inspiration and improve with sitting forward 1, 2
• Pericardial rub: Auscultatory finding representing friction between inflamed pericardial layers 1
• ECG changes: New widespread ST-segment elevation or PR depression in multiple leads 1
• Pericardial effusion: New or worsening fluid collection around the heart detected by imaging 1

Supporting Diagnostic Findings

• Elevated inflammatory markers: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count 1, 3
• Evidence from advanced cardiac imaging techniques (CT, CMR) showing pericardial inflammation 1

Laboratory Tests

First-line Laboratory Tests

• Inflammatory markers: CRP, ESR, and complete blood count with differential 1, 3
• Cardiac biomarkers: Troponin and creatine kinase (CK) to assess for myocardial involvement 1
• Renal function tests: BUN, creatinine 1, 3
• Liver function tests: AST, ALT, bilirubin 1, 3
• Thyroid function tests: TSH 1, 3

Additional Laboratory Tests Based on Clinical Suspicion

• Autoimmune workup: ANA, ENA, ANCA, ferritin (if Still's disease suspected) 1, 3
• Tuberculosis testing: IGRA test (Quantiferon, ELISpot) 1, 3
• Viral studies: PCR for viral genomes, serology for HCV and HIV 1, 3
• Bacterial infection: Blood cultures (before antibiotic administration) 1, 4

Imaging Studies

First-line Imaging

• Transthoracic echocardiography: Recommended in all patients with suspected pericarditis 1
• Chest X-ray: Recommended in all patients, though often normal unless pericardial effusion exceeds 300 ml 1

Second-line Imaging

• CT and/or Cardiac MRI: Recommended when first-line testing is insufficient for diagnosis 1

Management Protocol

Risk Stratification

• Low-risk patients (no risk factors): Outpatient management with empiric anti-inflammatories 1
• High-risk patients (presence of major risk factors): Hospital admission and etiology search 1

Major Risk Factors

• Fever >38°C (>100.4°F) 1
• Subacute course (symptoms developing over several days or weeks) 1
• Large pericardial effusion (diastolic echo-free space >20 mm) 1
• Cardiac tamponade 1
• Failure to respond to NSAIDs within 7 days 1

Treatment Approach

First-line Treatment

• NSAIDs: Mainstay of therapy for idiopathic and viral pericarditis 1, 5
• Colchicine: Added to NSAIDs to improve response and reduce recurrence rates by approximately 50% 5

Second-line Treatment

• Corticosteroids: For patients who don't respond to, are intolerant of, or have contraindications to NSAIDs and colchicine 5

Special Situations

• Purulent pericarditis: Requires urgent pericardial drainage and intravenous antibiotics (e.g., vancomycin, ceftriaxone, ciprofloxacin) 4
• Tuberculous pericarditis: Treatment with isoniazid, rifampin, pyrazinamide, and ethambutol, plus prednisone 4

Follow-up

• Evaluation of response to anti-inflammatory therapy recommended after 1 week 1
• Monitor for recurrence, which may occur in up to 30% of patients without preventive therapy 5

Special Considerations

Pericardiocentesis Indications

• Cardiac tamponade 1
• Suspected bacterial or neoplastic pericarditis 1
• Symptomatic moderate to large effusions not responding to medical therapy 1

Pericardial Fluid Analysis

• Cytology: Cell count and differential 1
• PCR: Particularly for tuberculosis 1
• Microbiology: Cultures for bacteria (including Mycobacterium) 1

Common Pitfalls and Caveats

• ECG changes may be absent in up to 40% of cases 1
• Cardiac biomarker elevation may indicate concomitant myocarditis rather than primary pericardial disease 3
• Normal inflammatory markers do not exclude pericarditis, especially if the patient is already on anti-inflammatory treatment 3
• Failure to identify and treat purulent pericarditis is associated with nearly 100% mortality if untreated 6, 4
• Recurrence rates are high (approximately 30%) without appropriate preventive therapy 5