Ch15: Pericarditis

Preparatory Mindset

Pericarditis is a chest-pain differential staple — the classic triad is pleuritic chest pain relieved by leaning forward, a pericardial friction rub, and diffuse ST elevation with PR depression on ECG. The exam skills: (1) separate pericarditis from MI (diffuse concave ST elevation + PR depression vs localised STEMI changes; pain position change), (2) recognise pericardial effusion → tamponade (Beck's triad, pulsus paradoxus, electrical alternans) — a clinical emergency, and (3) know treatment: NSAIDs/aspirin + colchicine (reduces recurrence), corticosteroids as second-line (recurrence risk on abrupt withdrawal), and pericardial drainage for tamponade. The HKHA Cardiac Tamponade section is LMCHK-critical — including the "misdiagnosing tamponade as heart failure with diuretics/ACEi is lethal" warning.

Core Concepts

Definition & etiology

• Pericarditis = inflammation of the pericardium (visceral + parietal layers), often with effusion.
• Etiology (classic list): viral (most common — Coxsackie, EBV, CMV, influenza, COVID), idiopathic, bacterial (Staph/Strep/TB — purulent), tuberculous (important in HK/China — chronic, constrictive risk), uraemic, neoplastic (lung/breast, mesothelioma, lymphoma), autoimmune (SLE, RA, scleroderma), post-MI (Dressler syndrome), post-cardiac surgery (post-pericardiotomy), drugs (procainamide, hydralazine, INH), radiotherapy, trauma, hypothyroidism.
• Pathophysiology: pericardial inflammation → fibrin deposition → chest pain + rub; fluid accumulation → effusion; chronic inflammation → thickening, calcification (30–50%), constrictive pericarditis.

Clinical features

• Chest pain: sharp, pleuritic, positional — relieved by sitting up/leaning forward, worse lying flat; may radiate to trapezius ridge (phrenic nerve).
• Pericardial friction rub (scratchy, triphasic); dyspnoea; fever; tachycardia.
• ECG (acute pericarditis): diffuse concave-up ST elevation in most leads + PR-segment depression (pathognomonic combination); later T-wave inversion; low voltage with effusion.
• CXR: enlarged cardiac silhouette (>250 mL effusion), "water-bottle" heart; normal in early pericarditis.
• Echo: effusion, pericardial thickening (>4 mm), tamponade signs; constrictive physiology (septal bounce, respiratory variation).
• Labs: raised inflammatory markers (ESR/CRP), leukocytosis, troponin (may be mildly raised — myopericarditis); pericardial fluid analysis (exudate, cytology, AFB, cultures).

Pericardial effusion & cardiac tamponade

• Tamponade = effusion compressing one or more chambers → haemodynamic compromise; in acute tamponade a small effusion (~200 mL) can be fatal (pericardium cannot distend).
• Beck's triad: hypotension, muffled heart sounds, raised JVP.
• Pulsus paradoxus: exaggerated inspiratory drop in systolic BP >10 mmHg.
• Other signs: tachypnoea, tachycardia, small pulse volume, raised JVP with prominent x descent, Kussmaul's sign (JVP rises on inspiration), absent apex beat, faint heart sounds, clear lung fields.
• ECG: low voltage + electrical alternans; CXR: enlarged silhouette (>250 mL) with clear lung fields; echo: RA/RV/LA collapse, distended IVC, exaggerated tricuspid vs reduced mitral inflow during inspiration.
• Tamponade is a clinical diagnosis — effusion + haemodynamic compromise.

Diagnosis & differential

• Diagnosis: clinical (pain + rub + ECG) + echo.
• Differential: acute MI/ACS (localised ST elevation, troponin markedly raised, pain not positional), aortic dissection, pleurisy/PE, GERD, musculoskeletal, costochondritis, myocarditis (heart failure/arrhythmia prominence).

Treatment

• Acute pericarditis: NSAIDs (aspirin 750–1000 mg q8h, ibuprofen 300–800 mg q8h, or indomethacin 25–50 mg q8h) 1–2 weeks then taper; colchicine 0.5–0.6 mg BD (weight-adjusted) — reduces recurrence, now standard; corticosteroids (prednisone 0.2–0.5 mg/kg/day 2–4 weeks, slow taper) as second-line — ⚠️ high risk of recurrence with abrupt withdrawal; treat underlying cause (anti-TB for tuberculous, dialysis for uraemic, chemotherapy for malignant).
• Tamponade: urgent pericardiocentesis (echo-guided, apical or subcostal) — expand intravascular volume first (D5/NS/plasma, full rate if shock), avoid positive-pressure ventilation (impairs cardiac filling), open surgical drainage (pericardial window) if recurrent or for biopsy; oncology consult for malignant effusion (pericardiectomy consideration).
• Constrictive pericarditis: pericardial thickening >4 mm, calcification 30–50%, diastolic equalisation (LVEDP ≈ RVEDP); pericardiectomy — improves symptoms/hemodynamics in most, operative mortality 5–10%.

High-Yield Points

• Acute pericarditis: pleuritic positional chest pain + rub + diffuse concave ST elevation + PR depression.
• Treat: NSAIDs/aspirin 1–2 weeks + colchicine (↓ recurrence); steroids second-line (recurrence on abrupt withdrawal).
• Tamponade: Beck's triad, pulsus paradoxus >10 mmHg, Kussmaul's, electrical alternans; echo — chamber collapse + distended IVC.
• Tamponade = clinical diagnosis; treat with volume + urgent pericardiocentesis; avoid positive-pressure ventilation.
• Small acute effusion ~200 mL can tamponade; >250 mL enlarges CXR silhouette.
• Constrictive: thickening >4 mm, calcification 30–50%, pericardiectomy (mortality 5–10%).
• Never treat tamponade as CHF with diuretics/ACEi/vasodilators (lethal).

Topic Summary

Pericarditis presents with pleuritic, position-dependent chest pain, a friction rub, and the classic ECG pattern of diffuse ST elevation with PR depression; it is treated with NSAIDs/aspirin plus colchicine, with steroids reserved for refractory cases. Progression to effusion and cardiac tamponade is a life-threatening emergency diagnosed clinically (Beck's triad, pulsus paradoxus, Kussmaul's sign, electrical alternans) and treated with volume expansion and urgent echo-guided pericardiocentesis — never with diuretics/vasodilators. Chronic disease may evolve to constrictive pericarditis requiring pericardiectomy. The HKHA tamponade section, including its misdiagnosis warning, is an LMCHK priority.