How do you diagnose pericarditis in an inpatient?

Diagnosis of Pericarditis in an Inpatient Setting

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

First-Level Diagnostic Evaluation

Clinical Assessment

• Chest Pain Characteristics:

  • Sharp, pleuritic pain that may radiate to the left shoulder
  • Pain typically worsens when lying flat and improves when leaning forward
  • May be accompanied by dyspnea

• Physical Examination:

  • Auscultate for pericardial friction rub (high-pitched, scratching, or grating sound)
  • Perform auscultation during end expiration with patient sitting up and leaning forward to increase detection probability
  • Note that friction rub may be absent or transient despite active pericarditis

Essential Diagnostic Tests

1. Electrocardiogram (ECG):

   • Look for widespread ST-segment elevation (typically concave upward)
   • PR-segment depression
   • Absence of reciprocal ST-segment depression (helps differentiate from myocardial infarction)
   • Typical ECG changes occur in approximately 60% of cases 1

2. Transthoracic Echocardiography:

   • Assess for pericardial effusion
   • Evaluate for signs of tamponade (right atrial/ventricular diastolic collapse, respiratory variation in mitral/tricuspid flow)
   • Assess ventricular function and valvular abnormalities

3. Laboratory Tests:

   • Inflammatory markers: C-reactive protein (CRP), erythrocyte sedimentation rate (ESR)
   • Complete blood count with differential
   • Cardiac injury markers: troponin, creatine kinase (CK)
   • Renal function and liver tests
   • Thyroid function tests

4. Chest X-ray:

   • Evaluate cardiac silhouette (enlarged with effusions >300 ml)
   • Assess for pulmonary pathology

Second-Level Diagnostic Evaluation

When first-level testing is insufficient or specific etiologies are suspected:

1. Advanced Imaging:

   • Cardiac MRI (CMR): Provides detailed assessment of pericardial inflammation and myocardial involvement
   • Chest CT: Evaluates pericardial thickness and calcification

2. Pericardiocentesis (indicated for):

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

3. Pericardial Fluid Analysis:

   • Cytology (centrifugation improves diagnostic yield)
   • PCR for tuberculosis
   • Microbiology (cultures for bacteria including Mycobacterium)
   • Biochemical tests (protein, glucose, LDH)

Risk Stratification

Identify high-risk features requiring more extensive evaluation:

• Fever >38°C
• Subacute course (symptoms developing over several days/weeks)
• Large pericardial effusion or tamponade
• Failure to respond to NSAIDs
• Immunocompromised state 1, 2

Diagnostic Algorithm for Specific Etiologies

Based on clinical presentation, consider targeted testing:

1. Suspected Autoimmune Disease:

   • ANA, ENA, ANCA
   • Ferritin (if Still's disease suspected)
   • ACE and 24h urinary calcium (if sarcoidosis suspected)

2. Suspected Tuberculosis:

   • IGRA test (Quantiferon, ELISpot)
   • Chest CT scan

3. Suspected Neoplasm:

   • Chest and abdomen CT scan
   • Consider PET scan

4. Suspected Viral Infection:

   • PCR for viral genomes (preferred over serology)
   • Consider HIV and HCV serology

5. Suspected Bacterial Infection:

   • Blood cultures (before antibiotics)
   • Specific serology based on clinical suspicion (e.g., Q fever, Lyme disease)

Common Pitfalls and Caveats

1. Misdiagnosis: Pericarditis can mimic acute coronary syndrome. Key differentiating features include:

   • Widespread (not localized) ST elevation in pericarditis
   • Absence of reciprocal ST depression in pericarditis
   • PR depression in pericarditis (not typically seen in ACS)

2. Missed Complications:

   • Always assess for tamponade, which requires immediate intervention
   • Consider effusive-constrictive pericarditis if symptoms persist after drainage

3. Incomplete Evaluation:

   • Up to 80-90% of cases in developed countries are idiopathic or presumed viral 3
   • However, failure to identify specific treatable causes (especially in high-risk patients) can lead to poor outcomes

4. Overlooking Myopericarditis:

   • Elevated cardiac biomarkers may indicate myocardial involvement
   • Requires different management approach and prognostic implications

By following this systematic diagnostic approach, clinicians can effectively diagnose pericarditis in the inpatient setting, identify potential complications, and guide appropriate treatment decisions to improve patient outcomes.