A pericardial effusion is fluid in the pericardial sac.
Almost any cause of acute pericarditis induces the formation of an exudate. A pericardial transudate may occur as a result of cardiac failure.
Fluid accumulating within the closed pericardium may reduce ventricular filling and hence cause compromise of the cardiac output (cardiac tamponade).
Heart sounds are soft and apex beat is difficult to palpate. If the effusion accumulates quickly, features of low cardiac output failure usually appear. Slow accumulation of fluid is often well tolerated until very large due to distension of the pericardial sac.
Chest X-ray often shows an enlarged globular heart, which may have very clear borders (because cardiac movements occur within the fluid and so do not blur the X-ray).
The ECG shows reduced voltages with varying voltages between successive beats.
Echocardiogram is diagnostic with the demonstration of the echo free zone around the heart, usually posteriorly.
This is determined by the size and haemodynamic effect of the effusion. Small effusions (i.e. less than 0.5 cm separation of pericardium) do not require specific treat ment, but followup observation is mandatory to identify developing tamponade. Pericardiocentesis (needle aspiration of the fluid) may be indicated to establish the cause and to relieve tamponade. In cases of recurrent effusion, surgical treatment with a pericardial window allows drainage to the pleural space.