How do you differentiate between pericarditis and invasive cardiac disease in a patient presenting with cardiac symptoms?

Differentiating Pericarditis from Invasive Cardiac Disease

Start with echocardiography as your first-line imaging test, then measure cardiac enzymes (troponin) to assess for myocardial involvement, and reserve cardiac MRI for cases requiring definitive characterization of pericardial inflammation or when myocardial involvement needs to be distinguished from ischemic disease. 1

Initial Diagnostic Approach

Echocardiography (First-Line)

• Transthoracic echocardiography is the recommended first-line imaging modality for all patients with suspected pericarditis 1
• Echocardiography accurately detects pericardial effusion (as small as 45 ml), cardiac tamponade, and ventricular dysfunction that would suggest myocardial involvement 1
• Critically, echocardiography helps differentiate pericarditis from myocardial ischemia by excluding wall motion abnormalities consistent with coronary distribution 1
• However, recognize that 5% of patients with acute pericarditis and myocardial involvement may demonstrate wall motion abnormalities, and a normal echocardiogram does not exclude pericarditis 1, 2
• Echocardiography provides semiquantitative assessment of effusion size: small (<10 mm), moderate (10-20 mm), large (>20 mm) 1

Cardiac Enzymes (Essential for Risk Stratification)

• Measure troponin levels in all patients with suspected pericarditis, as elevation occurs in up to 50% of cases and indicates myocardial involvement (myopericarditis) 1, 2
• Elevated troponin distinguishes pure pericarditis from myopericarditis, which has important prognostic and management implications 1, 2
• Troponin elevation is a high-risk feature requiring hospital admission 2
• Also measure C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), and white blood cell count as markers of inflammation to support the diagnosis and monitor disease activity 1

Cardiac MRI (Advanced Characterization)

• Cardiac MRI is the most sensitive study for confirming myocardial and pericardial inflammation, with sensitivity of 94-100% for detecting pericardial inflammation 2
• MRI with gadolinium contrast demonstrates late gadolinium enhancement (LGE) in areas of pericardial inflammation and can distinguish myopericarditis from other causes including myocardial infarction with nonobstructive coronary arteries 1, 2
• Reserve cardiac MRI for complicated cases, atypical presentations, or when you need to definitively characterize the extent of myocardial involvement 1, 3
• MRI is particularly useful for monitoring disease activity in chronic or remitting pericarditis, as quantitative pericardial delayed hyperenhancement independently predicts clinical remission 1

Algorithmic Decision-Making

Step 1: Clinical Presentation

• Look for characteristic pericarditic chest pain (sharp, pleuritic, improves with sitting forward, radiates to trapezius ridge) 1, 2
• Auscultate for pericardial friction rub with patient sitting upright, leaning forward, briefly holding breath 2
• Obtain ECG looking for widespread concave ST elevation and PR depression (present in <60% of cases) 1, 2, 3

Step 2: Immediate Testing

• Perform transthoracic echocardiography immediately to detect effusion, assess for tamponade, and exclude regional wall motion abnormalities suggesting ischemic disease 1
• Simultaneously measure troponin, CRP, and ESR 1, 2

Step 3: Interpretation and Next Steps

• If echocardiography shows pericardial effusion without wall motion abnormalities AND troponin is normal: Diagnosis is likely pure pericarditis 1
• If echocardiography shows effusion AND troponin is elevated: Diagnosis is myopericarditis; consider cardiac MRI for definitive characterization 1, 2
• If echocardiography shows regional wall motion abnormalities consistent with coronary distribution: Consider acute coronary syndrome; coronary angiography is recommended to rule out ischemic disease 2
• If clinical suspicion remains high but echocardiography is normal: Perform cardiac MRI, as purely fibrinous pericarditis may have normal echocardiogram 1, 3

Critical Pitfalls to Avoid

• Do not assume a normal echocardiogram excludes pericarditis—pericardial effusion is only present in approximately 60% of cases 1, 2
• Do not dismiss elevated troponin as ruling out pericarditis—up to 50% of pericarditis cases have troponin elevation indicating myopericarditis, not necessarily ischemic disease 1, 2
• Do not rely solely on ECG changes—classic widespread ST elevation or PR depression occurs in less than 60% of patients, and ECG may be normal at presentation 1, 3
• Do not confuse left arm pain with typical pericarditis—this suggests possible myopericarditis or acute coronary syndrome and warrants coronary angiography 2
• Recognize that pericardial friction rubs are highly specific but only audible in approximately one-third of patients and can be transient 1, 2

High-Risk Features Requiring Admission

Admit patients with any of the following 1, 2:

• Elevated troponin
• Large pericardial effusion (>20 mm)
• Cardiac tamponade
• Fever >38°C (100.4°F)
• Subacute course
• Hemodynamic instability
• Failure to respond to anti-inflammatory therapy after 1 week