Pericardial effusion

Overview

•Inflammatory/autoimmune - pericarditis (viral, bacterial, TB), Dressler's syndrome, SLE, rheumatoid arthritis

•Malignancy - metastatic (lung, breast, melanoma most common); often haemorrhagic and haemodynamically significant

•Iatrogenic - post-cardiac surgery, post-coronary angiogram/PCI, pacemaker lead perforation

•Trauma - haemopericardium can develop rapidly even with modest volumes

•Metabolic - hypothyroidism, uraemia, hypoalbuminaemia

Dressler's syndrome vs early post-MI pericarditis
FeatureEarly post-MI pericarditisDressler's syndrome
OnsetWithin 48 hours of MI2-6 weeks post-MI
MechanismDirect pericardial inflammationAutoimmune - antibodies against myocardial proteins released during infarct healing
Shared featuresPleuritic chest pain, fever, raised ESR/CRP/WBC, pericardial friction rubPleuritic chest pain, fever, raised ESR/CRP/WBC, pericardial friction rub

Feature	Early post-MI pericarditis	Dressler's syndrome
Onset	Within 48 hours of MI	2-6 weeks post-MI
Mechanism	Direct pericardial inflammation	Autoimmune - antibodies against myocardial proteins released during infarct healing
Shared features	Pleuritic chest pain, fever, raised ESR/CRP/WBC, pericardial friction rub	Pleuritic chest pain, fever, raised ESR/CRP/WBC, pericardial friction rub

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Timing is the key discriminator: Dressler's syndrome = 2-6 weeks post-MI; early pericarditis = within 48 hours. Both can cause a pericardial effusion with muffled heart sounds.

Presentation

•Dyspnoea - most common symptom; reduced cardiac output

•Pleuritic chest pain - sharp, worse on inspiration and lying flat; relieved by sitting forward (when pericarditis is the cause)

•Muffled heart sounds - fluid attenuates sound transmission

•Raised JVP - impaired right heart filling

•Pulsus paradoxus - fall in systolic BP >10 mmHg on inspiration; right ventricular expansion bows septum left, reducing LV filling

•Tachycardia - compensatory response to falling stroke volume

•Hypotension - late sign indicating haemodynamic decompensation

Cardiac tamponade vs constrictive pericarditis - key differentiators
FeatureCardiac tamponadeConstrictive pericarditis
Beck's triadPresent (hypotension, raised JVP, muffled heart sounds)Not a classic feature
Kussmaul's signAbsent - JVP does not change with inspirationPositive - JVP rises/fails to fall with inspiration
Pulsus paradoxusPresentUsually absent
Pericardial knockAbsentPresent
Lung fieldsUsually clearUsually clear

Feature	Cardiac tamponade	Constrictive pericarditis
Beck's triad	Present (hypotension, raised JVP, muffled heart sounds)	Not a classic feature
Kussmaul's sign	Absent - JVP does not change with inspiration	Positive - JVP rises/fails to fall with inspiration
Pulsus paradoxus	Present	Usually absent
Pericardial knock	Absent	Present
Lung fields	Usually clear	Usually clear

Investigations

•Gold standard/First-line: Transthoracic echocardiogram (TTE) - quantifies effusion size; right atrial systolic collapse and right ventricular diastolic collapse indicate tamponade; required in all suspected acute pericarditis (ESC guideline)

•ECG - saddle-shaped ST elevation in all leads (pericarditis); low QRS voltage (large effusion); PR depression; electrical alternans (beat-to-beat QRS variation - heart swings in fluid; highly specific for large effusion/tamponade)

•Chest X-ray - large effusions give globular 'flask-shaped' cardiac silhouette; may be normal with smaller effusions

•Bloods - FBC, CRP, ESR (inflammation); U&E (uraemia); TFTs (hypothyroidism); troponin; blood cultures if infective

•CT chest - loculated effusions, pericardial thickening, underlying malignancy

•Pericardial fluid analysis (from pericardiocentesis) - protein, LDH, cell count, culture, AFB smear, cytology

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Electrical alternans (beat-to-beat QRS axis/amplitude variation) is highly specific for large pericardial effusion - when seen with tachycardia and low voltage, tamponade is very likely.

Management

•Small asymptomatic effusion - treat underlying cause; monitor with serial echocardiography every 3-6 months

•Inflammatory cause (Dressler's/viral pericarditis) - NSAIDs + colchicine for 3 months; restrict strenuous activity

•Cardiac tamponade - urgent echo-guided pericardiocentesis; IV fluid bolus to maintain preload while arranging drainage

•Malignant effusion - percutaneous balloon pericardiotomy preferred due to high recurrence rate; ongoing oncological management

•Post-pericardiocentesis - repeat echo at 24-48 hours; drain left in situ until <25 mL/day output

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Aortic dissection is a contraindication to pericardiocentesis - the haemopericardium acts as protective tamponade limiting further haemorrhage. Draining it can cause exsanguination. Always consider dissection before draining a haemorrhagic effusion.

Complications

•Cardiac tamponade - rising intrapericardial pressure → equalisation of diastolic pressures across all chambers → impaired filling → falling cardiac output → cardiogenic shock

•Constrictive pericarditis - fibrotic pericardial thickening restricts diastolic filling; presents with raised JVP, Kussmaul's sign, pericardial knock, ascites; causes include prior cardiac surgery/catheterisation, TB, viral pericarditis

•Recurrence - particularly idiopathic, viral, or malignant effusions; up to one-third of large idiopathic effusions may develop tamponade unexpectedly