Definition

A pulmonary embolism is a blockage of an artery in the lungs. The embolism prevents blood and nourishment from getting to a specific area of the lungs. This may lead to the death of lung tissue in this area. Damage to the lungs may make it difficult for the lungs to work properly. In severe cases, a pulmonary embolism can lead to death.

Pathway of Pulmonary Embolism

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Causes

An embolism is caused by a lump of material (an embolus) that is floating in the blood. An embolus can be a blood clot, air bubble, a piece of fat, bone marrow, or tumor tissue. The embolus travels from its original location and passes through larger blood vessels until it gets stuck in a smaller blood vessel. In this case, the embolus is trapped in an artery of the lungs.

The embolus in a pulmonary embolism is usually a blood clot. It most often starts in a vein in the legs or pelvis.

Risk Factors

Factors that increase your chance of developing a pulmonary embolism include:

• Blood clot in a deep vein of a leg or the pelvis
• Increased levels of clotting factors in the blood
• Prolonged bed rest
• Major surgery, especially after pelvic surgery, knee replacement, or heart surgery
• Injury to a vein in a leg or the pelvis
• Fractures of the hip or thigh bone (femur)
• Certain blood disorders
• Prolonged sitting, such as during a long trip
• Pregnancy or postpartum period
• Smoking
• Obesity
• Inflammatory bowel disease
• Autoimmune disorder (for example, immune thrombocytopenic purpura, polyarteritis nodosa, or polymyositis)
• Cancer
• Taking certain medicines, such as birth control pills or antipsychotics

Symptoms

The symptoms of a pulmonary embolism vary depending on the size and location of the blockage. The area affected by the lack of blood will also affect the symptoms. General 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, or dizzy
• Cough, sometimes with bloody phlegm
• Rapid heartbeat
• Rapid breathing
• Anxiety
• Feeling of impending doom

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done. Your doctor may order the following tests:

• Arterial blood gas study —a blood test to check oxygen levels and lung function
• Chest x-ray —a picture of the lungs to look for signs of dead tissue; the pulmonary embolism cannot be seen on the chest x-ray
• Lung perfusion scan—a test that measures breathing and circulation in all areas of the lungs (an embolus will cause a mismatch between the lungs)
• CT scan of the chest —detailed pictures of the inside of the chest
• Pulmonary angiogram —a special dye can highlight the areas of blockage in the lungs
• Magnetic resonance (MR) angiography
• EKG —a test to look for abnormal rhythms in the heart (such as rapid heartbeats)
• Echocardiography —a test to examine the size, shape, and motion of the heart
• D-Dimer (a clot-dissolving substance) blood test—increased levels in the blood may suggest the presence of a clot
• If you have a family history of blood clots, and had blood clots in the past for no apparent reason, your doctor may do additional blood tests. The tests will look for possible inherited defects in your clotting system, such as:
  • Factor V Leiden mutation (seen in up to 40% of cases)
  • Increased factor VIII
• Additional tests may be done to check blood flow or look for clots in your veins. These tests will most likely be done in your legs.

If you are diagnosed with a pulmonary embolism, follow your doctor's instructions.

Treatment

Treatment depends on the size and severity of the clot. Emergency treatment and hospitalization may be needed.

Treatments include:

Prevention

Prevention of pulmonary embolism means preventing clots from forming.

You can help prevent clots with a healthy lifestyle:

• Eat a healthful diet that is low in saturated fat and rich in whole grains, fruits, and vegetables.
• Begin a safe exercise program with the advice of your doctor.
• Walk or move your legs to break up long periods of sitting.
• If you smoke, quit.
• 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 are most commonly used.
• Wear elastic stockings (also called support hose) if suggested by your doctor. They can help improve circulation in your legs.
• Walk or move your legs to break up long periods of sitting. If you are traveling, get up and walk every few hours.