heart and lungs

What is a pulmonary embolism?

A pulmonary embolism is a blood clot in the lung that occurs when a clot in another part of the body (often the leg or arm) moves through the bloodstream and becomes lodged in the blood vessels of the lung. This restricts blood flow to the lungs, lowers oxygen levels in the lungs and increases blood pressure in the pulmonary arteries.

If a clot develops in a vein and it stays there, it’s called a thrombus. If the clot detaches from the wall of the vein and travels to another part of your body, it’s called an embolus.

What causes pulmonary embolism?

Pulmonary embolism may occur:

  • When blood collects (or “pools”) in a certain part of the body (usually an arm or leg). Pooling of blood usually occurs after long periods of inactivity, such as after surgery or bed rest.
  • When veins have been injured, such as from a fracture or surgery (especially in the pelvis, hip, knee or leg).
  • As a result of another medical condition, such as cardiovascular disease (including congestive heart failure, atrial fibrillation and heart attack) or stroke.
  • When clotting factors in the blood are increased, elevated, or in some cases, lowered. Elevated clotting factors can occur with some types of cancer or in some women taking hormone replacement therapy or birth control pills. Abnormal or low clotting factors may also occur as a result of hereditary conditions.

Who is at risk of developing a blood clot?

People at risk for developing a blood clot are those who:

  • Have been inactive or immobile for long periods of time due to bed rest or surgery.
  • Have a personal or family history of a blood clotting disorder, such as deep vein thrombosis (DVT) or pulmonary embolism (PE).
  • Have a history of cancer or are receiving chemotherapy.
  • Sit for prolonged periods.

People at risk for developing a pulmonary embolism include those who:

  • Are inactive for long periods of time while traveling via motor vehicle, train or plane
  • Have a history of heart failure or stroke
  • Are overweight or obese
  • Have recently had trauma or injury to a vein, possibly after a recent surgery, fracture or due to varicose veins
  • Are pregnant or have given birth in the previous 6 weeks
  • Are taking birth control pills (oral contraceptives) or hormone replacement therapy
  • Placement of central venous catheters through the arm or leg

If you have any of these risk factors and you have had a blood clot, please talk with your health care provider so steps can be taken to reduce your personal risk.

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