Key Facts:

  • Pulmonary embolism can be life-threatening with 10-30% of individuals dying within one month of diagnosis.
  • Pulmonary embolism affects around 900,000 people in the U.S. every year.
  • In most cases, pulmonary embolism is caused by blood clots in the legs, called deep vein thrombosis, that travel to the lungs.

How Pulmonary Embolism (PE) Affects Your Body

A blood clot may start in another part of the body, usually the legs or veins in the pelvis, called deep vein thrombosis (DVT). At some point if untreated, this deep vein clot may break loose and travel 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. 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.

  • Prior History: Around 33% of people affected by a deep vein thrombosis or pulmonary embolism will experience another within 10 years.
  • Inactivity: Blood clots are more likely to form during prolonged periods of sitting such as bed rest or during air travel. Being immobile in the hospital, particularly after surgery or trauma is a significant risk.
  • Other Medical Conditions: Heart disease, interstitial lung disease, COVID-19, pancreatic, ovarian, lung, and many cancers with metastasis can make clotting more likely. Lupus and other rheumatologic diseases may be associated with increased clotting.
  • 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: January 20, 2023

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