Pulmonary Embolism
all information

Pulmonary Embolism

En Español (Spanish Version)


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

factsheet image

© 2008 Nucleus Medical Art, 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.

Risk Factors

A risk factor is something that increases your chance of getting a disease or condition.

Risk factors for pulmonary embolism include:

  • 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. Sometimes however it is associated with the lung infarct that can be visualized.
  • 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 a 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 highly 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 for a patient.
  • 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 for a patient.
  • 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 for a patient.
  • MR angiography— The use of magnetic resonance angiography (MRA) for the diagnosis of PE is rather limited, however it may be more usueful in the future as the technologic advances continue.
  • 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 that can help in making the diagnosis.
  • Echocardiography—is useful in about 1/3 of patients with PE.

Additional tests may be done to check blood flow or look for clots in the veins, especially in the legs.

Also, there are a few blood tests available that can help in making the diagnosis:

  • D-Dimer—a clot dissolving substance. Increased levels in the blood may suggest the presence of the clot. It is unfortunately a nonspecific test and a lot of different conditions may cause (eg, recent surgery) it 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 percent of cases) and increased factor VIII.


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
    • Urokinase
    • Tissue plasminogen activator (TPA)
  • Anticoagulant medicine, called blood thinners, such as heparin or 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 performed 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.


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 total fat as well as saturated fat, and rich in whole grains, legumes, fruits, and vegetables.
  • Exercise regularly.
  • Walk or move your legs to break up long periods of sitting. If your are traveling, get up and walk around every 3 hours.
  • Don't smoke.
  • 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 such as warfarin or heparin are most commonly used.
  • Wear elastic stockings (also called support hose) to improve circulation in your legs.


American Lung Association

American College of Surgeons


Canadian Lung Association

Health Canada


Canadian Lung Association website. Available at: http://www.lung.ca .

Gibson, NS, Sohne, M, Buller, HR. Prognostic value of echocardiography and spiral computed tomography in patients with pulmonary embolism. Curr Opin Pulm Med 2005; 11:380.

The Merck Manual of Diagnosis and Therapy. Simon and Schuster, Inc.; 1999.

Ohno, Y, Higashino, T, Takenaka, D, et al. MR Angiography with sensitivity encoding (SENSE) for suspected pulmonary embolism: comparison with mdct and ventilation-perfusion scintigraphy. AJR Am J Roentgenol 2004; 183:91.

Philbrick JT, Shumate R, Siadaty MS, Becker DM. Air travel and venous thromboembolism: a systematic review. J Gen Intern Med . 2007 Jan;22(1):107-14.

Pulmonary embolism. JAMA . 2001 Feb 14.

Qaseem A, Snow V, Barry P, Hornbake ER, Rodnick JE, Tobolic T, et al; Joint American Academy of Family Physicians/American College of Physicians Panel on Deep Venous Thrombosis/Pulmonary Embolism. Current diagnosis of venous thromboembolism in primary care: a clinical practice guideline from the American Academy of Family Physicians and the American College of Physicians. Ann Intern Med . 2007 Mar 20;146(6):454-8.

Rosendaal, FR. Venous thrombosis: A multicausal disease. Lancet 1999; 353:1167.

Rubini G, Niccoli Asabella A, Stabile Ianora AA, Rubini D, Gaudiano A, Angelelli G, et al.Acute pulmonary embolism: comparison and integration of perfusion lung scintigraphy with multislice spiral CT. Radiol Med (Torino) . 2007 Mar;112(2):174-184. Epub 2007 Mar 19.

Last reviewed March 2008 by Marcin Chwistek, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

Your Health and Happiness