Acute pericarditis

Overview

Acute pericarditis is inflammation of the pericardium lasting <4-6 weeks, accounting for ~5% of ED non-ischaemic chest pain presentations. Mostly idiopathic/viral (~90%). Key clinical importance: mimics ACS on ECG but managed differently.

Aetiology

•Idiopathic/viral (~90%) - Coxsackievirus B, echovirus, CMV, EBV

•Post-cardiac injury - early post-MI fibrinous pericarditis (1-3 days); Dressler's syndrome (weeks-months post-MI/cardiac surgery)

•TB - predominant cause in developing countries

•Uraemic - indication for emergency dialysis

•Autoimmune - SLE, rheumatoid arthritis, sarcoidosis

•Malignancy - lung, breast, Hodgkin's lymphoma

Presentation

•Chest pain - sharp, pleuritic, retrosternal; relieved by sitting forward, worse lying supine

•Pericardial friction rub - scratching, high-pitched at left sternal edge; best heard leaning forward in held expiration; pathognomonic but evanescent

•Fever - low-grade (viral); high fever suggests bacterial

•Referred left shoulder tip pain - via phrenic nerve (C3-C5)

•Viral prodrome - preceding URTI, myalgia, malaise

⚠️
A disappearing friction rub in a deteriorating patient suggests a developing pericardial effusion - fluid separates the inflamed layers.

Investigations

•ECG - diffuse saddle-shaped (concave) ST elevation, PR depression (most leads), PR elevation in aVR

•CRP/ESR/FBC - confirms active inflammation; CRP used to guide colchicine duration

•Troponin - mild elevation acceptable; significant rise suggests myopericarditis

•Echocardiogram - assesses effusion, wall motion, ventricular function; recommended in all confirmed/suspected cases

•CXR - usually normal; 'flask-shaped' enlarged cardiac silhouette if effusion >250 mL

Acute pericarditis vs STEMI on ECG
FeaturePericarditisSTEMI
ST elevation shapeDiffuse, concave (saddle-shaped)Localised to territory, convex (dome-shaped)
PR depressionPresent (highly specific)Absent
Reciprocal ST depressionAbsent (except aVR)Present in opposite leads
Pathological Q wavesAbsentMay develop

Feature	Pericarditis	STEMI
ST elevation shape	Diffuse, concave (saddle-shaped)	Localised to territory, convex (dome-shaped)
PR depression	Present (highly specific)	Absent
Reciprocal ST depression	Absent (except aVR)	Present in opposite leads
Pathological Q waves	Absent	May develop

Management

•High-risk features requiring hospitalisation: fever >38°C, subacute onset, large effusion, cardiac tamponade, failure to respond to NSAIDs after 1 week, immunocompromise, oral anticoagulant use, trauma, suspected myopericarditis

🥇 First-line

•ibuprofen 600 mg three times daily (or aspirin 750-1000 mg three times daily if post-MI) - continue until CRP normalises, then taper

•Add: colchicine 0.5 mg twice daily (0.5 mg once daily if <70 kg or intolerant) for 3 months - reduces recurrence by ~50%

•Gastroprotection: omeprazole 20 mg once daily co-prescribed with NSAIDs

🥈 Second-line

•prednisolone (low-moderate dose) - only if NSAIDs contraindicated or steroid-responsive cause (SLE, uraemic pericarditis)

🥉 Third-line

•anakinra (IL-1 receptor antagonist) or azathioprine - refractory/recurrent disease, specialist input required

•Activity restriction - avoid strenuous activity until symptoms resolve and CRP normalises; competitive athletes restricted for at least 3 months

•Cause-specific: uraemic pericarditis - urgent dialysis; TB pericarditis - antituberculous therapy; bacterial - IV antibiotics ± surgical drainage

⚠️
Corticosteroids as first-line in idiopathic/viral pericarditis increase the risk of recurrence and should be avoided unless NSAIDs are contraindicated or a steroid-responsive cause is confirmed.

Complications

•Pericardial effusion - inflammatory exudate; large effusions cause haemodynamic compromise

•Cardiac tamponade - raised intrapericardial pressure → reduced cardiac output; Beck's triad: muffled heart sounds, hypotension, raised JVP; requires urgent pericardiocentesis

•Recurrent pericarditis - 15-30% after first episode; managed with NSAIDs, colchicine, ± immunosuppression

•Constrictive pericarditis - chronic fibrotic thickening → impaired diastolic filling; rare (<1%) with viral cause but more common with bacterial/TB; presents with right heart failure features

•Myopericarditis - extension into myocardium; more common in young men; disproportionate troponin elevation, risk of arrhythmias

💡
Prognosis is excellent in idiopathic/viral pericarditis - complete resolution in 1-2 weeks with treatment; <0.5% develop constrictive pericarditis. Bacterial and TB causes carry higher morbidity and greater risk of constriction.

Diagnostic criteria (ESC 2015)

At least 2 of the following 4 criteria required:

1.Pleuritic chest pain (positional, sharp)

2.Pericardial friction rub

3.ECG changes: new widespread saddle-shaped (concave) ST elevation or PR depression

4.Pericardial effusion (new or worsening) on echocardiogram