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A pulmonary embolism (PE) is a sudden blockage in a lung artery, usually due to a blood clot that traveled to the lung from a vein in the leg. A clot that forms in one part of the body and travels in the bloodstream to another part of the body is called an embolus.
Pulmonary embolism is a serious condition that can cause:
If a clot is large, or if there are many clots, pulmonary embolism can cause death.
At least 100,000 cases of PE occur each year in the United States. PE is the third most common cause of death in hospitalized patients. If left untreated, about 30 percent of patients who have PE will die. Most of those who die do so within the first few hours of the event.
In 9 out of 10 cases, pulmonary embolism begins as a blood clot in the deep veins of the leg (a condition known as deep vein thrombosis). The clot breaks free from the vein and travels through the bloodstream to the lungs, where it can block an artery.
Rarely, an air bubble, part of a tumor, or other tissue travels to the lungs and causes PE. Also, when a large bone in the body (such as the thigh bone) breaks, fat from the marrow inside the bone can travel through the blood to the lungs and cause PE.
Major Signs and Symptoms
Signs and symptoms of pulmonary embolism include unexplained shortness of breath, problems breathing, chest pain, coughing, or coughing up blood. An arrhythmia (an irregular heartbeat) also may indicate PE.
In some cases, the only signs and symptoms are related to deep vein thrombosis (DVT). These include swelling of the leg or along the vein in the leg, pain or tenderness in the leg, a feeling of increased warmth in the area of the leg that's swollen or tender, and red or discolored skin on the affected leg. See your doctor at once if you have any symptoms of PE or DVT.
It's possible to have a PE and not have any signs or symptoms.
Other Signs and Symptoms
Sometimes people who have PE have feelings of anxiety or dread, lightheadedness or fainting, rapid breathing, sweating, or an increased heart rate.
A number of tests can help diagnose PE. Which tests you have will depend on how you feel when you get to the hospital, your risk factors for PE, available testing options, and other conditions you possibly have. You may have one or more of the following tests.
Doctors use ultrasound to look for blood clots in your legs. Ultrasound uses high-frequency sound waves to check the flow of blood in your veins.
Gel is put on the skin of your leg. A hand-held device called a transducer is placed on the leg and moved back and forth over the affected area. The transducer gives off ultrasound waves and detects their echoes after they bounce off the vein walls and blood cells.
A computer then turns the echoes into a picture on a computer screen, allowing your doctor to see the blood flow in your leg. If blood clots are found in the deep veins of your legs, your doctor will recommend treatment.
DVT and PE are both treated with the same medicines.
Computed Tomography Scans
Doctors use computed tomography, or CT, scans to look for blood clots in your lungs and in your legs.
Dye is injected into a vein in your arm. The dye makes the blood vessels in your lungs and legs show up on an x-ray image. While you lie on a table, an x-ray tube rotates around you, taking pictures from different angles.
This test allows doctors to detect most cases of PE. The test only takes a few minutes. Results are available shortly after the scan is completed.
Lung Ventilation/Perfusion Scan
A lung ventilation/perfusion scan, or VQ scan, uses a radioactive substance to show how well oxygen and blood are flowing to all areas of the lungs. This test can help detect PE.
Pulmonary angiography is another test used to diagnose PE. It's not available at all hospitals, and a trained specialist must perform the test.
For this test, a flexible tube called a catheter is threaded through the groin (upper thigh) or arm to the blood vessels in the lungs. Dye is injected into the blood vessels through the catheter.
X-ray pictures are taken to show blood flowing through the blood vessels in the lungs. If a blood clot is found, your doctor may use the catheter to extract it or deliver medicine to dissolve it.
Certain blood tests may help your doctor find out whether you're likely to have PE.
A D-dimer test measures a substance in the blood that's released when a clot breaks up. High levels of the substance may mean there's a clot. If your test is normal and you have few risk factors, PE isn't likely.
Other blood tests check for inherited disorders that cause clots and measure the amount of oxygen and carbon dioxide in your blood. A clot in a blood vessel in your lungs may lower the level of oxygen in your blood.
To rule out other possible causes of your symptoms, your doctor may use one or more of the following tests.