Pericardial effusion and cardiac tamponade

Definition

A pericardial effusion is an accumulation of fluid in the pericardial sac. Cardiac tamponade is present when a moderate or large effusion impairs filling of the heart, leading to low cardiac output and sometimes shock and death. Tamponade is primarily a clinical diagnosis.

Classification

• By composition: serous (possibly with fibrin strands), serosanguineous, blood (hemopericardium), pus, chyle.
• By distribution: free or loculated; loculated effusions and localised hematomas can cause localised tamponade of individual chambers only.
• Small effusion: under 1 cm on echocardiography, or about 100 ml.

Aetiopathogenesis

• As in pericarditis: infections, autoimmune diseases, uremia, post-infarction and post-pericardiotomy syndromes, tumors, hypothyroidism (including cholesterol pericarditis), radiogenic.
• Large chronic effusion: most often due to metastases, especially from lung and breast cancer, sarcomas, melanoma, leukemia or lymphoma.
• Hemopericardium: chest trauma, iatrogenic injury (cardiac catheterisation, pacemaker insertion, central venous line), rupture of a thoracic aortic aneurysm, rupture of the heart wall after myocardial infarction (usually 1–10 days after the infarction).
• Pathophysiology: the pericardium can stretch only slowly. If fluid (usually blood) accumulates rapidly, as little as about 150 ml can cause tamponade; with slow accumulation, up to 1500 ml are tolerated without tamponade.

Clinical features

• Pericardial effusion: often painless and asymptomatic, even when large, if it develops over months; muffled heart sounds, enlarged area of cardiac dullness; with large effusions reduced breath sounds and crackles at the left base (below the left scapula). Pulse, neck veins and blood pressure remain normal unless tamponade develops.
• Tamponade: picture similar to cardiogenic shock with low cardiac output, hypotension, tachycardia and dyspnea, but markedly distended neck veins; muffled heart sounds unless the effusion is small.
• Pulsus paradoxus: in severe tamponade almost always an inspiratory fall in systolic blood pressure of more than 10 mmHg; in advanced cases the pulse disappears on inspiration.
• Kussmaul's sign is absent in tamponade.

Diagnosis

• Echocardiography: confirms the effusion and estimates its size; signs of tamponade are exaggerated respiratory variation of transvalvular and venous flows, compression or collapse of the right heart chambers and a plethoric inferior vena cava (decrease in diameter of less than 50 % on deep inspiration).
• ECG: often reduced QRS voltage with sinus rhythm usually maintained; with large chronic effusions electrical alternans due to the "swinging heart". Low voltage and alternans are neither sensitive nor specific for tamponade.
• Chest X-ray: enlarged cardiac silhouette.
• CT and cardiac MRI: effusion often an incidental CT finding (size tends to be overestimated); detection of metastases.
• Right heart catheterisation when tamponade is uncertain: diastolic pressures in all cardiac chambers and the pulmonary artery raised (about 10–30 mmHg) and equalised; in the atrial pressure curve the x descent is maintained but the y descent lost; no early diastolic dip.
• Fluid analysis: cytology and culture including acid-fast bacilli; other laboratory values of the fluid are usually non-specific.

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Further reading (open access)

1. MSD Manual Professional: Pericarditis
2. MSD Manual Professional: Cardiac Tamponade
3. StatPearls: Pericardial Effusion
4. StatPearls: Cardiac Tamponade

Cross-references