Pulmonary embolus

Alternative names
Venous thrombo-embolism; Lung blood clot; Fat embolus; Air embolus; Tumor embolus

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

Causes, incidence, and risk factors

Pulmonary emboli are blockages of the blood vessels of the lungs (pulmonary vessels). Most often they are caused by blood clots from the veins, especially veins in the legs or in the pelvis (hips). More rarely, air bubbles, fat droplets, amniotic fluid, or clumps of parasites or tumor cells may obstruct the pulmonary vessels.

The most common cause of a Pulmonary embolism is a blood clot in the veins of the legs, called a deep vein thrombosis (DVT). Many vlear up on their own, though some may cause severe illness or even death.

Risk factors include the following:

  • Prolonged bed rest or inactivity (including long trips in planes, cars, or trains),  
  • Oral contraceptive use  
  • Surgery (especially pelvic surgery)  
  • Childbirth  
  • Massive trauma  
  • Burns  
  • Cancer  
  • Stroke  
  • Heart attack  
  • Heart surgery  
  • Fractures of the hips or femur

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


It is important to note that the symptoms of Pulmonary embolism may be vague or may resemble symptoms associated with other diseases:

  • cough       o begins suddenly       o may produce bloody sputum (significant amounts of visible blood or lightly blood streaked sputum)  
  • sudden onset of shortness of breath at rest or with exertion  
  • splinting of ribs with breathing (e.g., bending over or holding the chest)  
  • chest pain       o under the breastbone or on one side       o especially sharp or stabbing; also may be burning, aching or dull, heavy sensation       o may be worsened by breathing deeply, coughing, eating, bending, or stooping  
  • breathing, rapid  
  • rapid heart rate (tachycardia)

Additional symptoms that may be associated with this disease:

  • wheezing  
  • skin, clammy  
  • skin discoloration, bluish  
  • nasal flaring  
  • pelvis pain  
  • leg pain in one or both legs  
  • swelling in the legs (lower extremities)  
  • lump associated with a vein near the surface of the body (superficial vein), may be painful  
  • blood pressure, low  
  • pulse, weak or absent  
  • lightheadedness  
  • fainting  
  • dizziness  
  • sweating  
  • anxiety

Signs and tests

Tests to evaluate the function of the lungs:

  • arterial blood gases  
  • pulse oximetry

Tests to detect the location and extent of embolism:

  • chest X-ray  
  • pulmonary ventilation/perfusion scan  
  • pulmonary angiogram

Tests to detect DVT (a common cause):

  • Doppler ultrasound exam of an extremityblood flow studies  
  • venography of the legs  
  • plethysmography of the legs

An ECG may show abnormalities caused by strain on the heart.

This disease may also alter the results of the following tests:

  • echocardiogram  
  • D-dimer level  
  • chest CT scan  
  • chest MRI scan


Emergency treatment and hospitalization are necessary. In cases of severe, life-threatening Pulmonary embolism, definitive treatment consists of dissolving the clot with thrombolytic therapy. Anticoagulant therapy prevents the formation of more clots and allows the body to re-absorb the existing clots faster.

Thrombolytic therapy (clot-dissolving medication) includes streptokinase, urokinase, or t-PA. Anticoagulation therapy (clot-preventing medication) consists of heparin by intravenous infusion initially, then oral warfarin (Coumadin). Subcutaneous low-molecular weight heparin is often substituted for intravenous heparin in many circumstances.

In patients who cannot tolerate anticoagulation therapy, an inferior vena cava filter (IVC filter) may be placed. This device, placed in the main central vein in the abdomen, is designed to block large clots from traveling into the pulmonary vessels. Oxygen therapy may be required to maintain normal oxygen concentrations.

Surgery in patients at great risk for recurrent embolism is sometimes indicated.

Expectations (prognosis)

It is difficult to assess the prognosis of Pulmonary embolism, because many cases are never diagnosed. Often, the prognosis is related to the disease that puts the person at risk for Pulmonary embolism (cancer, major surgery, trauma, etc.). In cases of severe Pulmonary embolism, where shock and heart failure occur, the death rate may be greater than 50%.


  • palpitations  
  • heart failure or shock  
  • respiratory distress (severe breathing difficulty)  
  • sudden death  
  • hemorrhage (usually a complication of thrombolytic or anticoagulation therapy)  
  • pulmonary hypertension with recurrent Pulmonary embolism

Calling your health care provider
Go to the emergency room or call the local emergency number (such as 911) if symptoms of pulmonary embolus occur.

Prevention of Deep venous thrombosis (DVT) among patients who are at risk is very important. Walking and activity as soon as possible after surgery or during a prolonged medical illness can reduce the risk for pulmonary embolus. Subcutaneous heparin therapy (low doses of heparin injected under the skin) may be used for those on prolonged bedrest. Other preventive measures include compression stockings (plastic sleeves that fit around the legs and help circulate the blood).

Johns Hopkins patient information

Last revised: December 3, 2012
by Martin A. Harms, M.D.

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