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

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

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 the veins of the legs, called a deep vein thrombosis (DVT).

More rarely, air bubbles, fat droplets, amniotic fluid, or clumps of parasites or tumor cells may lead to a pulmonary embolus.

Risk factors for a pulmonary embolus include:

• Long-term bed rest or staying in one position for a long time, such as a long plane or car ride
• Use of birth control bills
• Surgery (especially pelvic surgery)
• Childbirth
• Severe injury
• Burns
• Cancer
• Stroke
• Heart attack
• Heart surgery
• Fractures of the hips or femur

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

• Cough
  • Begins suddenly
  • May cough up blood or blood-streaked sputum
• Shortness of breath
  • Starts suddenly
  • May occur at rest or during activity
• Pain in ribs during breathing (person ususally bends over or holds their chest)
• Chest pain
  • Under the breastbone or on one side
  • Especially sharp or stabbing; also may be a burning, aching, or dull, heavy sensation
  • May get worse with deep breathing, coughing, eating, bending, or stooping
• Rapid breathing
• Rapid heart rate

• Wheezing
• Clammy skin
• Bluish skin discoloration
• Nasal flaring
• Pelvis pain
• Leg pain in one or both legs
• Swelling in the legs
• Lump associated with a vein near the surface of the body, may be painful
• Low blood pressure
• Weak or absent pulse
• Lightheadedness or fainting
• Dizziness
• Sweating
• Anxiety

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:

• Chest x-ray
• CT angiogram of the chest
• Pulmonary ventilation/perfusion scan
• Pulmonary angiogram

Other tests that may be done include:

• Doppler ultrasound exam of an extremity
• Venography of the legs
• Plethysmography of the legs
• ECG
• Echocardiogram
• D-dimer level
• Chest CT scan
• Chest MRI scan

Emergency treatment and a hospital stay may be necessary. In cases of severe, life-threatening pulmonary embolism, treatment may consist of dissolving the clot and preventing new clots from forming.

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

• Streptokinase
• t-PA
• Urokinase

Treatment to prevent clots is called anticoagulation therapy. Such drugs are commonly called blood thinners. Clot-prevention medicines include heparin and warfarin (Coumadin). 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 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 lung vessels. Sometimes a temporary filter can be placed and removed later. Oxygen therapy may be required to maintain normal oxygen levels.

You may need surgery if you have a great risk for recurrent embolism.

It is difficult to predict how well a patient will do. Often, the outlook is related to the disease that puts the person at risk for pulmonary embolism (for example, cancer, major surgery, trauma). In cases of severe pulmonary embolism, where shock and heart failure occur, the death rate may be greater than 50%.

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

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

Prevention of deep venous thrombosis (DVT) among at-risk patients is very important. 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 every now and then. This is called intermittent pneumatic compression. It helps keep blood moving and prevents blood clotting.

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 Feb 6;146(3):204-10. Epub 2007 Jan 29.

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 Dec 19;298(23):2743-53.

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 Apr 19;371(9621):1343-52.