What is a pericardial effusion?

A large pericardial effusion. In this image, the structure bouncing from left to right is the heart, with the large black space surrounding it made up of excess fluid (the pericardial effusion). A comparison with a normal echocardiogram is below.

A pericardial effusion means you have an excess of fluid around the heart, which can push on the heart itself and cause problems.

Your heart beats thousands of times per day. To protect it from rubbing against other organs in the chest, the heart itself is kept inside a protective bag, called the pericardium. Within this bag there is a very small amount of fluid, less than 50mL, which lubricates the outside of the heart and prevents any two surfaces rubbing together.

If excess fluid accumulates within this space, it is called a pericardial effusion. The danger of this effusion depends on two things:

  1. The overall amount of fluid
  2. The speed at which the fluid collects

A large amount of fluid that collects over a long time may not cause a problem, while a small amount of fluid that collects quickly can.

The large effusion. Note the large amount of black space around the heart, and the relative instability of the heart moving from side to side (abnormal).
A normal echocardiogram. Note that the fluid around the heart is barely visible (normal).











The fluid doesn’t build up by itself without cause. Most commonly, a pericardial effusion is due to:

  • pericarditis, an inflammation of the lining of the heart – due to viruses, bacteria, or unknown causes
  • after a heart attack
  • autoimmune disease, where the body’s own immune system damages the lining
  • trauma to the heart, including surgery on the heart

This fluid can be dangerous if it pushes on the heart. Every beat, your heart squeezes out blood, and then it expands again to fill with blood. If it can’t expand because there is fluid around it, then it can’t fill properly – which means there won’t enough blood to pump out for the next beat. This dangerous situation is called cardiac tamponade.

To see if this fluid has built up to dangerous levels, there are two important tests:

  1. A history and examination, looking for specific features of tamponade
  2. A transthoracic echocardiogram, to see the amount of fluid and look to see if the heart is being compressed

Treatment includes the following:

  1. Anti-inflammatory medications to reduce the amount of inflammation of the lining of the heart (pericardium).
  2. Drainage via a needle
  3. Drainage via a small operation

Both of the latter options are only used if the fluid is significant and is likely to cause problems. Often a small tube is left in the chest for 24 hours to drain any remaining fluid, and then removed on the following day.



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