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Pulmonary embolus

Definition

A pulmonary embolus is a blockage of an artery in the lungs by fat, air, a blood clot, or tumor cells.

Alternative Names

Venous thromboembolism; Lung blood clot; Blood clot - lung; Embolus; Tumor embolus; Embolism - pulmonary

Causes

A pulmonary embolus is most often caused by a blood clot in a vein, especially a vein in the leg or in the pelvis (hip area). The most common cause is a blood clot in one of the deep veins of the thighs. This type of clot is called a deep vein thrombosis (DVT).

Less common causes include air bubbles, fat droplets, amniotic fluid, or clumps of parasites or tumor cells, all of which may lead to a pulmonary embolus.

Risk factors for a pulmonary embolus include:

  • Burns
  • Cancer
  • Childbirth
  • Family history of blood clots
  • Fractures of the hips or femur
  • Heart attack
  • Heart surgery
  • Long-term bed rest or staying in one position for a long time, such as a long plane or car ride
  • Severe injury
  • Stroke
  • Surgery (especially orthopedic or neurological surgery)
  • Use of birth control pills or estrogen therapy

People with certain clotting disorders may also have a higher risk.

Symptoms

  • Chest pain
    • Under the breastbone or on one side
    • Especially sharp or stabbing
    • May also be described as a burning, aching, or dull, heavy sensation
    • May get worse with deep breathing, coughing, eating, bending, or stooping
    • You may bend over or hold his or her chest in response to the pain
  • Cough
  • Rapid breathing
  • Rapid heart rate
  • Shortness of breath
    • May occur at rest or during activity
    • Starts suddenly

Other symptoms that may occur:

Exams and Tests

The following lab tests may be done to see how well your lungs are working:

  • Arterial blood gases
  • Pulse oximetry

The following imaging tests can help determine where the blood clot is located:

Other tests that may be done include:

Treatment

Emergency treatment and a hospital stay are often necessary. The goal is to stabilize your cardiovascular system and to prevent new clots from forming. Oxygen therapy may be required to maintain normal oxygen levels.

In cases of severe, life-threatening pulmonary embolism, treatment may involve dissolving the clot and preventing new clots from forming.

Treatment to dissolve clots is called thrombolytic therapy. Clot-dissolving medications include:

  • Streptokinase
  • t-PA

Treatment to prevent clots is called anticoagulation therapy. Such drugs are commonly called blood thinners. The most commonly used clot-prevention medicines are heparin and warfarin (Coumadin). Fondaparinux (Arixtra) is a newer blood thinner used under special circumstances. Heparin or heparin-type drugs can be given intravenously (by IV, directly into a vein), or as injections under the skin. These are usually the first medications given, and are then transitioned over to warfarin given in pill form.

When you first start taking warfarin, you will need frequent lab tests to check the thickness of your blood. This will help your doctor properly adjust your dose.

Patients who have reactions to heparin or related medications may need other medications.

Patients who cannot tolerate blood thinners or for whom they may be too risky may need a device called an inferior vena cava filter (IVC filter). This device is placed in the main central vein in the belly area. It keeps large clots from traveling into the blood vessels of the lungs. Sometimes a temporary filter can be placed and removed later.

Outlook (Prognosis)

It is difficult to predict how well a patient will do. Often, the outlook is related to what put the person at risk for pulmonary embolism (for example, cancer, major surgery, or trauma).

In cases of severe pulmonary embolism, where shock and heart failure occur, the death rate may be greater than 50%.

Possible Complications

  • Heart failure or shock
  • Heart palpitations
  • Pulmonary hypertension
  • Severe breathing difficulty
  • Severe bleeding (usually a complication of treatment)
  • Sudden death

When to Contact a Medical Professional

Go to the emergency room or call the local emergency number (such as 911) if you have symptoms of pulmonary embolus.

Prevention

Preventing deep venous thrombosis (DVT) is very important, especially in people at high risk. To help prevent DVT, move your legs often or take a stroll during long plane trips, car trips, and other situations in which you are sitting or lying down for long periods of time. Walking and staying active as soon as possible after surgery or during a long-term medical illness can also reduce your risk.

Heparin therapy (low doses of heparin injected under the skin) may be prescribed for those on prolonged bedrest.

Sometimes patients in the hospital wear special soft boots that automatically (and gently) squeeze the calves periodically. This is called intermittent pneumatic compression. It helps keep blood moving and prevents blood clotting.

References

Anderson DR, Kahn SR, Rodger MA, et al. Computed tomographic pulmonary angiography vs ventilation-perfusion lung scanning in patients with suspected pulmonary embolism: a randomized controlled trial.JAMA. 2007;298(23):2743-2753.

Righini M, Le Gal G, Aujesky D, et al. Diagnosis of pulmonary embolism by multidetector CT alone or combined with venous ultrasonography of the leg: a randomised non-inferiority trial. Lancet. 2008;371(9621):1343-1352.

Snow V, Qaseem A, Barry P, et al. Management of venous thromboembolism: a clinical practice guideline from the American College of Physicians and the American Academy of Family Physicians. Ann Intern Med. 2007;146(3):204-210.

Tapson VF. Pulmonary embolism. In: Goldman L, Ausiello D, eds. Cecil Medicine. 23rd ed. Philadelphia, Pa: Saunders Elsevier; 2007:chap 99.


Review Date: 3/28/2010
Reviewed By: David C. Dugdale, III, MD, Professor of Medicine, Division of General Medicine, Department of Medicine, University of Washington School of Medicine; Yi-Bin Chen, MD, Leukemia/Bone Marrow Transplant Program, Massachusetts General Hospital. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.
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