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Pulmonary Embolism


By Victor F. Tapson, MD

Pulmonary embolism is the blocking of an artery of the lung (pulmonary artery) by a collection of solid material brought through the bloodstream (embolus)—usually a blood clot (thrombus) or rarely other material.

  • Pulmonary embolism is usually caused by a blood clot, although other substances can also form emboli and block an artery.

  • Symptoms of pulmonary embolism vary but usually include shortness of breath.

  • Doctors often diagnose pulmonary embolism by looking for blockage of a pulmonary artery using computed tomography (CT) angiography or lung scanning.

  • Blood thinners (anticoagulant drugs) can be given to people at high risk to prevent pulmonary embolism.

  • Anticoagulant drugs are used to keep emboli from enlarging while the body dissolves the clots; other measures (such as drugs to break up blood clots or surgery) may be needed for people who appear to be at risk of dying.

The pulmonary arteries carry blood from the heart to the lungs. The blood picks up oxygen from the lungs and travels back to the heart. From the heart, the blood is pumped to the rest of the body to provide oxygen to the tissues. When a pulmonary artery is blocked by an embolus, people may not be able to get sufficient oxygen into the blood. Large emboli may cause so much blockage that the heart has to strain to pump blood through the pulmonary arteries that remain open (massive pulmonary embolism). If too little blood is pumped or the heart is strained excessively, the person can go into shock and die. Sometimes, the blockage of blood flow causes lung tissue to die (a condition called pulmonary infarction ).

The body usually breaks up small clots more quickly than larger clots, keeping damage to a minimum. Large clots take much longer to disintegrate, so more damage may be done.

Pulmonary embolism affects about 350,000 people per year and causes 85,000 deaths per year in the United States. It affects mainly adults.

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