Key Facts:

  • Pulmonary embolism can be life-threatening.
  • Pulmonary embolism affects around 1 in 1,000 people in the U.S. every year.
  • In most cases, pulmonary embolism is caused by blood clots in the legs or arms that travel to the lung, called deep vein thrombosis.
  • With timely treatment, most people can recover.
  • Pulmonary embolism can also lead to pulmonary hypertension, a condition in which the blood pressure in your lungs and the right side of the heart is too high.

How Pulmonary Embolism Affects Your Body

A blood clot may start in another part of the body, usually the arm or the leg. At some point, this deep vein clot breaks loose and travels through the circulatory system until it reaches the lungs. There, it lodges in the lung arteries and begins to block the normal flow of blood in the lungs. In rare cases, the artery can be blocked by something other than a blood clot, such as an air bubble or part of a tumor. Either way, the blockage causes damage to the lung and reduces the amount of oxygen in the blood that travels out to nourish the body. The longer the clot blocks oxygen, the more harm it can inflict on other organs. In certain situations when the obstruction causes the heart to work too hard and increases blood pressure in the lungs, pulmonary embolism can lead to pulmonary hypertension.

Who Is at Risk?

Many different factors can increase a person’s risk of developing deep vein thrombosis and pulmonary embolism.

  • Inactivity: Blood clots are more likely to form during prolonged periods of sitting such as bed rest or during air travel.
  • Other Medical Conditions: Heart disease, pancreatic, ovarian, lung, and many cancers with metastasis can make clotting more likely.
  • Smoking: Smoking narrows and damages the lining of blood vessels, making it more likely for blood clots to form.
  • Obesity: Being overweight increases the risk of blood clots especially in women who smoke or have high blood pressure.
  • Supplemental estrogen: High estrogen in birth control pills and hormone replacement therapies can increase blood clotting factors.
  • Pregnancy: Pregnant women can get clots because the fetus commonly presses on veins in the pelvis, slowing blood flow from the legs.
  • Family History: Although less common than other causes of excess blood clotting, some people have an inherited genetic condition that affects the normal clotting processes in the blood.

Reviewed and approved by the American Lung Association Scientific and Medical Editorial Review Panel.

Page last updated: October 23, 2020

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