Encyclopedia / P / Pulmonary Embolism

Pulmonary Embolism

What Is Pulmonary Embolism/DVT?

A pulmonary embolism is a blood clot that travels through the veins to block a pulmonary artery, one of the vessels that carry blood to the lungs to be oxygenated. In most cases the blood clot (thrombus) originates in a leg vein, owing to a condition known as deep vein thrombosis; though rare, other sources are the right chambers of the heart, the upper extremities, or the pelvic and renal veins. Part or all of a loosened thrombus may be carried into the pulmonary arteries. (Clumps of cancerous cells, fat, or bubbles of air in the bloodstream may also form emboli, although this is rare.) An embolus may lodge in the main pulmonary artery or one of the smaller branches of the pulmonary artery, cutting off the blood flow through the affected portion of the lungs.

Symptoms occur suddenly; severity depends on the size and number of emboli.

The disorder may quickly turn fatal if a large enough portion of the lungs is affected by either one large embolus or many smaller ones. Approximately one case in 10 results in sudden death. The first hour of a pulmonary embolism is crucial, so emergency treatment should be sought immediately; patients who survive long enough to be hospitalized and diagnosed usually recover. In the United States over a half million cases of pulmonary embolism occur each year. Outlook is most favorable among younger patients. In younger patients (under 55 years old), pulmonary embolism affects significantly more women than men, but it affects men more commonly than women in those over age 55. Mortality due to pulmonary embolism also appears to be higher among men than women.

Who Gets Pulmonary Embolism/DVT?

Because DVT often resolves on its own without treatment, the exact incidence of the condition is unknown. DVT is more common in patients over the age of 40. Incidence of pulmonary embolism doubles every 10 years after the age of 60.

In the United States, approximately 20–70% of patients who are hospitalized develop DVT. DVT and pulmonary embolism are leading causes for preventable deaths in hospitalized patients. Pulmonary embolism causes about 60,000 to100,000 deaths in the United States each year.


Symptoms of DVT vary, depending on the location and severity of the blood clot. In as many as 50% of patients who have the condition, DVT does not cause symptoms. In some cases, patients are not aware that they have DVT until the blood clot travels to the lung and causes pulmonary embolism.

Signs of deep vein thrombosis include the following:

  • Swelling (edema)
  • Pain or tenderness
  • Redness or discoloration
  • Warmth

Symptoms of pulmonary embolism include the following:

  • Sudden shortness of breath.

  • Sudden onset of chest pain, which is usually sharp and made worse by taking a deep breath.

  • Cough, possibly with bloody sputum.

  • Profuse perspiration.

  • Anxiety.

  • Palpitations or rapid heartbeat.

  • Lightheadedness.

  • Emergency symptom: loss of consciousness.

Causes/Risk Factors

  • A blood clot dislodged from a leg vein is the most common cause of pulmonary embolism.

  • Rarely, an air bubble or a clump of cancerous cells, fat, bacteria, or other material may lodge in a pulmonary artery.

  • Risk factors include pregnancy; recent surgery; previous heart attack or stroke; prolonged bed rest (for example, while recovering from an illness); birth control hormone therapy; obesity; smoking; bone fractures, especially of the hip or leg bones; cancer, especially of the lungs, brain, breast, or liver; and family history of venous thrombosis, pulmonary embolism, or certain blood clotting disorders. People who travel on long trips without standing and walking around may have an increased risk of DVT.

  • People with heart disease, emphysema, or chronic bronchitis are at greater risk of severe consequences from pulmonary embolism.


Diagnosis of DVT and pulmonary embolism involves taking a medical history and performing a physical examination and diagnostic tests. Blood tests also can be used to help in the diagnosis.

  • Patient medical history includes information about risk factors for DVT, including blood clotting disorders, use of hormones (birth control pills), obesity, and varicose veins.
  • During physical examination, the physician looks for signs such as tenderness, swelling, discoloration, and warmth on one side of the body (e.g., in one leg); checks blood pressure; and listens to the heart and lungs.
  • There are a number of diagnostic tests available to help diagnose DVT and pulmonary embolism. These tests include:
  • Chest x-rays. A chest x-ray may be performed to rule out other conditions
  • Ultrasound. Duplex ultrasound is the most common test used to diagnose DVT. In this test, sound waves are transmitted from a device called a transducer and are used to evaluate blood flow. The sound waves are then converted into an image on a computer screen that shows the flow of blood through the veins and can detect blood clots.
  • Venography. This test involves taking x-rays of the veins (called venograms) after a dye is injected to make them visible on x-ray. Venography can show reduced blood flow and detect blood clots. This test is rarely used now, however, as it has been replaced by CT scans, which can also offer venographic images.
  • Magnetic Resonance Imaging (MRI scan) uses electromagnetic radio waves to produce images of the veins and provides more information than x-rays.
  • Contrast CT (computed tomography) scans are used to look for large pulmonary emboli.
  • Electrocardiogram (ECG) is performed to rule out a heart attack and to detect evidence of increased pressure in the pulmonary arteries or of other serious cardiovascular conditions.
  • Radionuclide scanning, which involves inhaling a small amount of radioactive gas and injection of radioactive particles into the bloodstream, may highlight blocked portions of the blood vessels in the lungs on an x-ray scan.
  • Pulmonary arteriography (injection of a contrast dye into the pulmonary arteries prior to taking a series of x-rays) is the only certain way to identify pulmonary embolism, but is almost never required given the technological advancement in other non-invasive imaging techniques.


The goals of treatment in patients who have deep vein thrombosis (DVT) are to prevent the blood clot from getting larger, prevent the blood clot from moving to the lungs (pulmonary embolism), and reduce the risk for developing additional blood clots.

  • Analgesics are given to relieve pain.
  • Oxygen may be administered via an oxygen mask or, in severe cases, a respirator.
  • Anticoagulant drugs are administered to prevent further harmful blood clots. In addition to older medications such as heparin and warfarin (Coumadin), newer oral anticoagulants are now available that utilize different mechanisms to reduce clot formation. The newer drugs include apixaban (Eliquis), dabigatran (Pradaxa), and rivaroxaban (Xarelto). In most cases, patients with DVT are treated with anticoagulants for 3 to 6 months, unless the doctor feels that the patient is at an increased risk of recurrence.
  • Thrombolytic (clot dissolving) medications such as tPA (tissue plasminogen activator), streptokinase, or urokinase may be injected into the bloodstream to clear the blockage.
  • Anticoagulants and thrombolytics also may be used to treat patients with pulmonary embolism.
  • Patients who continue to develop blood clots in spite of treatment or have a medical contraindication to the use of a blood thinner (such as active bleeding) may benefit from a device called a vena cava filter, which can be inserted into the largest vein in the body (called the vena cava). This treatment can prevent pulmonary embolism, but it does not prevent DVT.
  • Emergency treatment is necessary for a suspected pulmonary embolism. Immediate surgical removal may be required when a large embolus is blocking a major pulmonary artery.


  • Prescription elastic support hose may be worn to prevent DVT in the legs among those at risk.

  • Regular doses of aspirin may be prescribed to prevent the development of blood clots for those at high risk, particularly after orthopedic surgery.

  • Heparin, an anticoagulant, may be administered in intermittent doses to decrease the possibility of blood clots in people at risk (for example, those with chronic venous insufficiency, congestive heart failure, or in those who have recently had a heart attack). or in people about to undergo surgery. After surgery, such patients are encouraged to get up and walk as soon as possible to improve circulation.

  • Another form of heparin, low-molecular weight heparin, may be an alternative to heparin. It can be taken intermittently.

  • Anticoagulant therapy may be prescribed on a long-term basis once the acute symptoms of the embolism have resolved. The newer anticoagulants, such as dabigatran, rivaroxaban, and apixaban, may be easier to take compared to warfarin because they do not require periodic checking of blood levels.

When To Call Your Doctor

  • EMERGENCY Call an ambulance immediately if you or someone in your presence develops sudden, severe chest pain and shortness of breath, along with feelings of great apprehension or dread. In addition to pulmonary embolism, such symptoms may also be indications of a heart attack or other serious cardiovascular crisis.

  • EMERGENCY Call an ambulance immediately any time someone unexpectedly loses consciousness.

Reviewed by Allen J. Blaivas, D.O., Division of Pulmonary, Critical Care, and Sleep Medicine, VA New Jersey Health Care System, Clinical Assistant Professor, Rutgers New Jersey Medical School, East Orange, NJ. Review provided by VeriMed Healthcare Network.