Pericardial Effusion

Pericardial effusion is where excess fluid collects within the pericardial sac. Pericardial effusion can be acute or chronic. They can fill the entire pericardial cavity or only a localised section. 

The effusion can be made of: 

  • Transudates (low protein content) 
  • Exudates (associated with inflammation)
  • Blood
  • Pus 
  • Gas (associated with bacterial infections)



There is a membrane that surrounds the heart called the pericardium or pericardial sac. This has two layers with a small amount of fluid in between (less than 50mls), providing lubrication. These layers separate the heart from the rest of the contents of the mediastinum. Lubrication between the two layers allows the heart to beat without generating too much friction.

Between the two layers, there is a potential space, called the pericardial cavity. The two layers are usually touching each other, which is why it is only a potential space. 

Pericardial effusion is when the potential space of the pericardial cavity fills with fluid. This creates an inward pressure on the heart, making it more difficult to expand during diastole (filling of the heart).

Pericardial tamponade (or cardiac tamponade) is where the pericardial effusion is large enough to raise the intra-pericardial pressure. This increased pressure squeezes the heart and affects its ability to function. It leads to reduced filling of the heart during diastole, resulting in decreased cardiac output during systole. This is an emergency requiring rapid drainage of the pericardial effusion to relieve the pressure.



Increased venous pressure can reduce drainage from the pericardial cavity, resulting in a transudative effusion. This may occur in:

  • Congestive heart failure
  • Pulmonary hypertension


Exudative effusions may occur in any inflammatory process affecting the pericardium (pericarditis), such as in:

  • Infection (e.g., tuberculosis, HIV, coxsackievirus, Epstein–Barr virus and other viruses)
  • Autoimmune and inflammatory conditions (e.g., systemic lupus erythematosus and rheumatoid arthritis)
  • Injury to the pericardium (e.g., after myocardial infarction, open heart surgery or trauma)
  • Uraemia (raised urea) secondary to renal impairment
  • Cancer
  • Medications (e.g., methotrexate)


Rupture of the heart or aorta can cause bleeding into the pericardial cavity, resulting in a rapid-onset cardiac tamponade. Rupture may be the result of:

  • Myocardial infarction
  • Trauma
  • Aortic dissection (type A)



The speed of onset of symptoms relates to how quickly the effusion develops. A rapidly collecting effusion with cardiac tamponade can quickly cause haemodynamic compromise and collapse. 

Slowly developing, chronic effusions, may initially be asymptomatic. As pressure rises, symptoms can develop, which may include: 

  • Chest pain
  • Shortness of breath
  • A feeling of fullness in the chest
  • Orthopnoea (shortness of breath on lying flat)


The effusion may compress surrounding structures, causing additional symptoms:

  • Phrenic nerve compression can cause hiccups
  • Oesophageal compression may cause dysphagia (difficulty swallowing)
  • Recurrent laryngeal nerve compression may cause a hoarse voice


Signs on examination include:

  • Quiet heart sounds
  • Pulsus paradoxus (an abnormally large fall in blood pressure during inspiration, notably when palpating the pulse)
  • Hypotension
  • Raised JVP
  • Fever (with pericarditis)
  • Pericardial rub (with pericarditis)



An echocardiogram is the investigation of choice. It can be used to:

  • Diagnose pericardial effusion
  • Assess the size of the effusion
  • Assess the effect on the heart function (haemodynamic effect)


Fluid analysis can be performed on the pericardial fluid to diagnose the underlying cause, including:

  • Protein content (to distinguish between transudative or exudative)
  • Bacterial culture
  • Viral PCR
  • Cytology and tumour markers (for cancer)



There are two components to treating a pericardial effusion:

  • Treatment of the underlying cause (e.g., infection)
  • Drainage of the effusion (where required)


Inflammatory causes (pericarditis) may be treated with:

  • Aspirin
  • NSAIDs
  • Colchicine
  • Steroids


There are two options for draining an effusion:

  • Needle pericardiocentesis (echocardiogram guided)
  • Surgical drainage


A pericardial window is a surgical procedure where a portion of the pericardium is removed, creating a “window” or fistula, that allows fluid to drain from the pericardial cavity into the pleural cavity or the peritoneal cavity.

Rarely, pericardiectomy (surgical removal of the pericardium) may be performed in recurrent cases.


Last updated May 2021