What Is a Pulmonary Embolism?

Your blood goes from your heart to your lungs through your pulmonary artery. In the lungs the blood is supplied with oxygen, then it goes back to the heart, which pumps the oxygen-rich blood to the rest of your body.

When a blood clot gets caught in one of the arteries that go from the heart to the lungs, it’s called a pulmonary embolism (PE). The clot blocks the normal flow of blood.

This blockage can cause serious problems, like damage to your lungs and low oxygen levels in your blood. The lack of oxygen can harm other organs in your body, too. If the clot is big or the artery is clogged by many smaller clots, a pulmonary embolism can be fatal.

Pulmonary embolisms usually travel to the lungs from a deep vein in the legs. Doctors call this “deep vein thrombosis” (DVT). These clots develop when the blood can’t flow freely through the legs because your body is still for a long time, say during a long flight or drive. It might also happen if you’re on bed rest after surgery or illness.

What Else Could Raise My Chances of PE?

The risk factors are the same as those for DVT. Doctors refer to these as “Virchow’s triad.” They include:

  • Being immobile for a prolonged period of time or having alterations in normal blood flow. This often happens if you’ve been hospitalized or on bed rest for a long period of time. It could also happen during a long flight or vehicle ride.
  • Increased clotting potential of your blood. Doctors call this “hypercoagulability.” This could be caused by medications, like birth control pills. Smoking, cancer, recent surgery, or pregnancy can also put you at risk.
  • Damage to a blood vessel wall. Trauma to your lower leg can lead to this.

In rare cases, an artery in the lung can be blocked by something other than a clot, like an air bubble or part of a tumor. If you break a big bone, sometimes fat from the bone marrow can come through the blood and cause blockage.

In life-threatening cases of pulmonary embolism, your doctor may decide to give you drugs called thrombolytics to break up the clot. It may even need to be taken out or broken up with surgery, though this is rare.

WebMD Medical Reference Reviewed by Paul Boyce, MD on December 22, 2018



American Heart Association: “How the Healthy Heart Works.”

Mayo Clinic: “Pulmonary Embolism.”

National Heart, Lung, and Blood Institute: “What is Pulmonary Embolism?”

CDC: “Venous Thromboembolism (Blood Clots).”

Society for Vascular Surgery: “Pulmonary Embolism.”

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