Pulmonary Embolus (PE)

What is a Pulmonary Embolus?

A pulmonary embolus (PE) occurs when a blood clot enters the blood vessels (arteries) of the lung. PE often occur when blood clot that starts in the veins of the legs travels to the blood vessels in the lungs. Sometimes PE can occur without any blood clot found in the leg.

What is the problem with PE?

PE can be life threatening. This is because the blood supply to the lungs is essential for oxygenation of the blood. Blood flow to the lung can stop if the blood clot is big enough to block one of the main arteries supplying the lung. This can lead to low blood flow around the rest of the body which can lead to collapse and even death. Smaller blood clots can lead to poor lung function and reduced oxygenation of the blood.

How is a pulmonary embolus diagnosed?

A PE is usually diagnosed by special x-rays (CT scan) that identify the blood clot blocking the blood vessel in the blood vessels of the lungs. Other techniques use special radioactive dye to look at the blood flow of the lungs.

Additional tests that may be helpful include blood tests and tracings of the rhythm of the heart.

Why did I develop a pulmonary embolus?

Usually people get PE for the same reason blood clots occur in other parts of the body. Some factors for getting a blood clot in the body include:

  • Hospitalisation for a medical illness
  • Recent major surgery or injury
  • Previous history of DVT / PE
  • Known personal history or a family history of a clotting disorder
  • History of active cancer and concurrent cancer therapy
  • Pregnancy and first 6 weeks after delivery
  • Smoking
  • Hormone replacement therapy or high dose combined oral contraceptive pill
  • Being overweight or obese
  • Prolonged sitting (greater than 6 to 8 hours)

How is a pulmonary embolus treated?

A PE is treated with blood thinning (anticoagulation). Anticoagulation is important to prevent any further blood clots from developing and may also help you reducing the size of blood clots that have already formed. If the blood clot is particularly large and blocking a lot of blood flow to the lung, a special medication given by the intravenous drip can be given to disolve the blood clot. This medication (called lytic therapy) needs to be given in hospital and is associated with a significant risk of bleeding.

Often blood thinning can be started and continued to be given as an outpatient with injections under the skin (low molecular weight heparin - Clexane). Patients will usually then need to start on tablets (Warfarin) and continue anticoagulation treatment.


How long will I need to be on blood thinning medication for?

This will depend on why you develop the blood clot in the first place. If the blood clot occurred in the setting of surgery or a known risk factor that is no longer present you may need six months blood thinning.

If a risk factor is not identified and your doctor thinks you may be at risk of developing further PE, a longer period of blood thinning may be needed.

Some people stay on blood thinning for a very long time because of they have a high risk of developing further PE. It is important for you to discuss this with your doctor.


For related information: Read the Fact Sheets:
Below Knee DVT - Calf vein thrombosis (Distal deep vein thrombosis (DVT)


Resources used to produce this information sheet

  1. Guyatt GH, Akl EA, Crowther M, Gutterman DD, Schuunemann HJ. Executive summary: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Chest. Feb 2012;141(2 Suppl):7S-47S.
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