A pulmonary embolism is a blockage of an artery in the lungs. It is caused by a clot that travels through the bloodstream to the lungs. Once the clot is stuck in a lung artery, it blocks the blood from nourishing that lung. The tissues on the other side of the blockage may die if it doesn't receive enough blood from other sources. The lung may become damaged and stop working properly. In severe cases this can lead to death.

Pathway of Pulmonary Embolism

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© 2009 Nucleus Medical Media, Inc.


An embolism occurs when a clot moves through the bloodstream from the location where it was formed and becomes stuck in a blood vessel. An embolus, can be a blood clot, air bubble, or piece of fat, bone marrow, or tumor tissue.

The embolus in a pulmonary embolism is usually a blood clot. A blood clot that forms and remains in a vein is called a thrombus. It most often starts in a vein in the legs or pelvis.


© 2009 Nucleus Medical Media, Inc.

Risk Factors

These factors increase your chance of developing pulmonary embolism. Tell your doctor if you have any of these risk factors:

  • Blood clot in a deep vein of a leg or pelvis
  • Increased levels of clotting factors in the blood. Usually caused by cancer (eg, pancreatic)
  • Prolonged bed rest, such as during a serious illness
  • Major surgery, especially after pelvic surgery, knee replacement, or heart surgery
  • Injury to a vein in a leg or pelvis
  • Fractures of the hip]]> or thigh bone (femur)
  • ]]>Heart attack]]> , ]]>stroke]]>
  • Certain blood disorders
  • Prolonged sitting, such as during a long trip
  • Pregnancy
  • Birth control pills
  • ]]>Smoking]]>
  • ]]>Obesity]]>



The symptoms of pulmonary embolism vary in type and severity depending on the size and location of the blockage, and the area affected by the lack of blood. Symptoms may include:

  • Shortness of breath that starts suddenly for no obvious reason
  • Chest pain, especially when breathing or coughing (it can mimic a heart attack]]> )
  • Feeling faint, lightheaded, dizzy
  • ]]>Cough]]> , sometimes with bloody phlegm
  • Rapid heartbeat
  • Rapid breathing
  • ]]>Anxiety]]>
  • Feeling of impending doom
  • Swollen, distended neck veins



The doctor will ask about your symptoms and medical history, and perform a physical exam. Tests may include:

  • Arterial blood gas study]]> —a blood test to identify oxygen levels and other gases that are indicators of lung function
  • ]]>Chest x-ray]]> —a test that uses radiation to take a picture of structures inside the chest. A pulmonary embolism cannot be seen on the chest x-ray. But, if a part of the lung tissue dies, this can be seen on the x-ray.
  • Lung perfusion scan—a test that uses radioactive isotopes to measure breathing and circulation in all areas of the lungs. The presence of an embolus will show as a mismatch between ventilation of the portion of the lung and its blood perfusion.
  • ]]>CT scan of the chest]]> —a type of x-ray that uses a computer to make pictures of the inside of the chest. A spiral CT is a special type of CT scan that is able to make tri-dimensional pictures. It is also a very fast scan that can be completed in a very short period of time. It has become popular in diagnosing pulmonary embolism.
  • Pulmonary ]]>angiogram]]> — x-rays taken after a dye is injected into the blood vessels in the lungs. The test shows areas of blockage in the lungs. It provides a clear picture of blood flow through the arteries. But, this test is associated with relatively high risks.
  • MR angiography (MRA)—Using this test to diagnose MRA is limited. But, it may be more useful in the future as the technology advances.
  • ]]>Electrocardiogram]]> (ECG, EKG)—a test that records the heart's activity by measuring electrical currents through the heart muscle. In case of pulmonary embolism, ]]>tachycardia]]> (rapid heart beat) is frequently seen, as well as several rhythm patterns. These results can help in the diagnosis.
  • ]]>Echocardiography]]> —a test that uses high-frequency sound waves (ultrasound) to examine the size, shape, and motion of the heart. This test may be helpful in a small percentage of patients.
  • D-Dimer (a clot dissolving substance) blood test—Increased levels in the blood may suggest the presence of a clot. This test is nonspecific, though. A lot of conditions may cause the level to be elevated.
    • If you have a family history of blood clots and had a few instances of blood clots for no apparent reason, your doctor may order additional blood tests. The tests will look for possible inherited defects in your clotting system. The two most frequent genetic abnormalities that increase your risk of forming blood clots are:
      • Factor V Leiden mutation (seen in up to 40% of cases)
      • Increased factor VIII
  • Additional tests—to check blood flow or look for clots in the veins, especially in the legs



Treatment depends on the size and severity of the clot. Emergency treatment and hospitalization may be needed.

Treatments include:


Options include:

  • Thrombolytic medicine to dissolve clots, for example:
    • Streptokinase (Kabikinase, Streptase)
    • Urokinase (Abbokinase)
    • Tissue plasminogen activator
  • Anticoagulant medicine, called blood thinners (eg, heparin]]> , ]]>warfarin]]> ), to prevent more clots from forming


In some cases when the blockage is very large, a type of surgery called embolectomy may be done to remove it.

Clot-Trapping Filter

If you have a repeated problem with blood clots, surgery may be done to place a filter in the main vein that leads from the legs to the heart and lungs. This filter traps clots before they can reach the lungs.

If you are diagnosed with pulmonary embolism, follow your doctor's instructions .



Prevention of pulmonary embolism means preventing clots from forming.

You can help prevent clots with a healthful lifestyle:

  • Eat a healthful diet]]> , one that is low in saturated fat and rich in whole grains, fruits, and vegetables.
  • Begin a safe ]]>exercise program]]> with the advice of your doctor.
  • Walk or move your legs to break up long periods of sitting. If your are traveling, get up and walk every 3 hours.
  • If you smoke, ]]>quit]]> .
  • Unless you are on a fluid-restricted diet, be sure to drink lots of water.

People at high risk of developing blood clots can do the following:

  • Take medicine, if your doctor recommends it. Anticoagulant drugs are most commonly used.
  • Wear elastic stockings (also called support hose) to improve circulation in your legs.