Pericardial effusion

Pericardial effusion refers to accumulation of pathological amounts of fluid in the pericardial cavity. In physiological cases there is 15-50 mL of fluid in the cavity. It may cause cardiac tamponade, which is an emergency. If the fluid is blood it's called haemopericardium.

Cardiac tamponade is a condition where a pericardial effusion compresses the heart, leading to life-threatening acute heart failure. This occurs if the pericardial effusion develops rapidly or is large, causing the pressure in the pericardial space to exceed the pressure in the heart chambers. It’s an emergency which should be treated empirically even before a proper diagnosis is made.

Etiology

• Pericarditis
• Tuberculosis
• Following heart surgery
• Thoracic injury
• Metastasis
• Cardiac wall rupture (trauma, MI)

Pathomechanism

In cases where the fluid accumulates quickly, only small amounts of fluids (100-150 mL) are required to cause symptoms. Symptoms occur because the pressure in the pericardial cavity increases, preventing diastolic filling of the heart and causing cardiac tamponade.

In cases where it accumulates slowly, up to 2 litres may accumulate before symptoms occur. This is because the pericardial sac adjusts and expands to accomondate the increased fluid.

Clinical features

Pericardial effusion itself is usually not symptomatic until it reaches the point where cardiac tamponade develops. Cardiac tamponade has a distinct clinical presentation:

• Hypotension
• Tachycardia
• Jugular venous congestion
• Pulsus paradoxus

Pulsus paradoxus refers to when the systolic blood pressure decreases by more than 10 mmHg during inspirasjon compared to during expiration. This occus because the (physiological) increased filling of the right ventricle impairs the filling of the left ventricle, as the pericardium is non-compliant and therefore prevents the left ventricle from expanding. This can be measured directly with manual blood pressure measurement. The name "paradoxus" comes from the fact that during inspiration the pulse wave amplitude decreases, meansing that during inspiration some beats cannot be felt on the radial pulse.

Diagnosis and evaluation

A chest x-ray may not always show a pericardial effusion. The cardiac shadow may be enlarged. If the effusion is large enough, the heart may appear water bottle-shaped, called "water bottle sign". Echocardiography is the investigation best suited to evaluate pericardial effusion, as it will directly visualise the anechoic fluid around the heart. The effusion is mild when < 10 mm on echo, severe when > 20 mm, and moderate in between.

If cardiac tamponade is suspected based on the clinical features, one should not waste time with time-consuming investigations. A quick echocardiography to confirm pericardial fluid, together with typical clinical features, is usually sufficient to start treatment.

Should one make these investigations (for example if the diagnosis isn't immediately clear), they might show the following:

• ECG – low voltage, electrical alternans
  • Electrical alternans refers to alternating amplitude (height) of the QRS complex with each heartbeat
• Echocardiography – large effusion, collapse of chambers, swinging of the heart

Treatment

In case of small pericardial effusions, one can watchfully wait for it to either progress or regress. In case of larger effusions, pericardiocentesis is necessary, under ultrasound or fluoroscopic guidance.

Treatment for cardiac tamponade should not be delayed due to diagnostic evaluations. Treatment is by pericardiocentesis. If unsuccessful, surgery may be necessary. ‎