Pulmonary Embolism

Last Editorial Review: 4/15/2008

What Is pulmonary embolism?

A pulmonary embolism (PULL-mun-ary EM-bo-lizm), or pulmonary embolism, 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:

  • Permanent damage to part of your lung from lack of blood flow to lung tissue

  • Low oxygen levels in your blood

  • Damage to other organs in your body from not getting enough oxygen

If the blood clot is large, or if there are many clots, pulmonary embolism can cause death.

Overview of pulmonary embolism

In most cases, pulmonary embolism is a complication of a condition called deep vein thrombosis (DVT). In DVT, blood clots form in the deep veins of the body-most often in the legs. These clots can break free, travel through the bloodstream to the lungs, and block an artery.

This is unlike clots in the veins close the skin's surface, which remain in place and do not cause pulmonary embolism.


At least 100,000 cases of pulmonary embolism occur each year in the United States. Pulmonary embolism is the third most common cause of death in hospitalized patients. If left untreated, about 30 percent of patients with pulmonary embolism will die. Most of those who die do so within the first few hours of the event.

Pulmonary embolism disorder picture

Pulmonary Embolism Symptoms

What are the signs and symptoms of pulmonary embolism?

A pulmonary embolus may present with the sudden onset of chest pain and shortness of breath. The pain is classically sharp and worsens when taking a deep breath, often called pleuritic pain or pleurisy. There may be cough that produces bloody sputum.

The patient may have stable vital signs (blood pressure, heart rate, respiratory rate, and oxygen saturation) but frequently presents with an elevated heart rate. If the blood clot is large enough, it can block blood from leaving the right side of the heart thus preventing blood from entering the lungs. There is then no blood entering the left side of the heart to pump to the rest of the body. This can result in circulatory collapse (shock) and death.

What causes pulmonary embolism?

Major Causes

In 9 out of 10 cases, pulmonary embolism (PE) 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.

Clots in the leg can form when blood flow is restricted and slows down. This can happen when you don't move around for long periods of time, such as:

  • After some types of surgeries

  • During a long trip in a car or on an airplane

  • If you must stay in bed for an extended time

Veins damaged from surgery or injured in other ways are more prone to blood clots.

Other causes

Rarely, an air bubble, part of a tumor, or other tissue travels to the lungs and causes pulmonary embolism. 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 pulmonary embolism.

Who is at risk for pulmonary embolism?

Populations affected

Pulmonary embolism (PE) occurs equally in men and women. Risk increases with age: For each 10 years after age 60, the risk of pulmonary embolism doubles.

Certain inherited conditions, such as factor V Leiden, increase the risk of blood clotting, and, therefore, the risk of pulmonary embolism.

Major risk factors

People at high risk for a blood clot that travels to the lungs are those who:

Other risk factors

People who recently have been treated for cancer or who have a central venous catheter (a tube placed in a vein to allow easy access to the bloodstream for medical treatment) are more likely to develop DVT. The same is true for people who have been bedridden or have had surgery or suffered a broken bone in the past few weeks.

Other risk factors for DVT, which can lead to pulmonary embolism, include sitting for long periods of time (such as on long car or airplane rides), pregnancy and the 6-week period after pregnancy, and being overweight or obese. Women who take hormone therapy or birth control pills also are at increased risk for DVT.

People with more than one risk factor are at higher risk for blood clots.


Spider & Varicose Veins: Causes, Before and After Treatment Images See Slideshow

What are the signs and symptoms of pulmonary embolism?

Major signs and symptoms

Signs and symptoms of pulmonary embolism (PE) include unexplained shortness of breath, difficulty breathing, chest pain, coughing, or coughing up blood. An arrhythmia (a rapid or irregular heartbeat) also may indicate pulmonary embolism.

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 pulmonary embolism or DVT.

It's possible to have a pulmonary embolism and not have any signs or symptoms of pulmonary embolism or DVT.

Other signs and symptoms

Sometimes people who have pulmonary embolism experience feelings of anxiety or dread, lightheadedness or fainting, rapid breathing, sweating, or an increased heart rate.

How is pulmonary embolism diagnosed?

Specialists involved

Doctors who treat patients in the emergency room are often the ones to diagnose pulmonary embolism (PE) with the help of a radiologist (a doctor who deals with x rays and other similar tests).

Medical History and Physical Exam

To diagnose pulmonary embolism, the doctor will ask about your medical history and perform a physical exam to:

  • Identify your risk factors for deep vein thrombosis (DVT) and pulmonary embolism

  • See how likely it is that you could have pulmonary embolism

  • Rule out other possible causes for your symptoms

During the physical exam, the doctor will check your legs for signs of DVT. He or she also will check your blood pressure and your heart and lungs.

Diagnostic Tests

There are many different tests that help the doctor determine whether you have pulmonary embolism. The doctor's decision about which tests to use and in which order depends on how you feel when you get to the hospital, your risk factors for pulmonary embolism, available testing options, and other conditions you may have.

You may have one of the following imaging tests:

  • Ultrasound. Doctors use this test to look for blood clots in your legs. Ultrasound uses high-frequency sound waves to check the flow of blood in your veins. A 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 of the ultrasound waves into a picture on a computer screen, where your doctor can see the blood flow in your leg. If blood clots are found in the deep veins of your legs, you will begin treatment. DVT and pulmonary embolism are both treated with the same medicines.

  • Spiral CT scan or CT angiogram. Doctors use this test to look for blood clots in your lungs and in your legs. Dye is injected into a vein in your arm to make the blood vessels in your lungs and legs more visible on the 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 pulmonary embolism in most patients. The test only takes a few minutes. Results are available shortly after the scan is completed.

  • Ventilation-perfusion lung scan (VQ scan). Doctors use this test to detect pulmonary embolism. The VQ scan uses a radioactive material to show how well oxygen and blood are flowing to all areas of the lungs.

  • Pulmonary angiography is another test used to diagnose pulmonary embolism. It's not available at all hospitals, and a trained specialist must perform the 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 the blood flow through the blood vessels in the lungs. If a clot is discovered, the doctor may use the catheter to extract it or deliver medicine to dissolve it.

Certain blood tests may help the doctor find out whether you're likely to have pulmonary embolism.

  • A D-dimer test measures a substance in the blood that's released when a clot breaks up. High levels of the substance mean there may be a clot. If your test is normal and you have few risk factors, pulmonary embolism 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 (arterial blood gas). A clot in a blood vessel in your lung may lower the level of oxygen in your blood. To rule out other possible causes of your symptoms, the doctor may use one or more of the following tests.

  • Echocardiogram uses sound waves to check heart function and to detect blood clots inside the heart. EKG (electrocardiogram) measures the rate and regularity of your heartbeat.

  • Chest x ray provides a picture of the lungs, heart, large arteries, ribs, and diaphragm.

  • Magnetic resonance imaging (MRI) uses radio waves and magnetic fields to make pictures of organs and structures inside the body. In many cases, an MRI can provide information that can't be seen on an x ray.

How is pulmonary embolism treated?

Goals of treatment

The main goals of treating pulmonary embolism (PE) are to:

  • Stop the blood clot from getting bigger

  • Keep new clots from forming

Treatment may include medicines to thin the blood and slow its ability to clot. If your symptoms are life threatening, the doctor may give you medicine to dissolve the clot more quickly. Rarely, the doctor may use surgery or another procedure to remove the clot.

Specific types of treatment


Anticoagulants (AN-te-ko-AG-u-lants), which are blood-thinning medicines, decrease your blood's ability to clot. They're used to stop blood clots from getting bigger and to prevent clots from forming. They don't break up blood clots that have already formed. (The body dissolves most clots with time.)

Anticoagulants can be taken as either a pill, an injection, or through a needle or tube inserted into a vein (called intravenous, or IV, injection). Warfarin is given in a pill form. (Coumadin® is a common brand name for warfarin.) Heparin is given as an injection or through an IV tube.

Your doctor may treat you with both heparin and warfarin at the same time. Heparin acts quickly. Warfarin takes 2 to 3 days before it starts to work. Once warfarin starts to work, usually the heparin will be stopped.

Pregnant women usually are treated with heparin only, because warfarin is dangerous for the pregnancy.

If you have deep vein thrombosis, treatment with anticoagulants usually lasts for 3 to 6 months.

If you have had blood clots before, you may need a longer period of treatment. If you're being treated for another illness, such as cancer, you may need to take anticoagulants as long as risk factors for pulmonary embolism are present.

The most common side effect of anticoagulants is bleeding. This happens if the medicine thins your blood too much. This side effect can be life threatening. Sometimes, the bleeding can be internal. This is why people treated with anticoagulants usually receive regular blood tests. These tests are called PT and PTT tests, and they measure the blood's ability to clot. These tests also help the doctor make sure you're taking the right amount of medicine. Call your doctor right away if you have easy bruising or bleeding.

Thrombin inhibitors are a newer type of anticoagulant medicine. They're used to treat some types of blood clots for patients who can't take heparin.

Emergency treatment

When pulmonary embolism is life threatening, doctors may use treatments that remove or break up clots in the blood vessels of the lungs. These treatments are given in the emergency room or in the hospital.

Thrombolytics are medicines given to quickly dissolve a blood clot. They're used to treat large clots that cause severe symptoms. Because thrombolytics can cause sudden bleeding, they're used only in life-threatening situations.

In some cases, the doctor may use a catheter to reach the blood clot. A catheter is a flexible tube placed in a vein to allow easy access to the bloodstream for medical treatment. The catheter is inserted into the groin (upper thigh) or arm and threaded through a vein to the clot in the lung. The catheter may be used to extract the clot or deliver medicine to dissolve it.

Rarely, surgery may be needed to remove the blood clot.

Other types of treatment

When you can't take medicines to thin your blood, or when you're taking blood thinners but continue to develop clots anyway, the doctor may use a device called a vena cava filter to keep clots from traveling to your lungs. The filter is inserted inside a large vein called the inferior vena cava (the vein that carries blood from the body back to the heart). The filter catches clots before they travel to the lungs. This prevents pulmonary embolism, but it doesn't stop other blood clots from forming.

Graduated compression stockings can reduce the chronic (ongoing) swelling that may occur after a blood clot has developed in a leg. The leg swelling is due to damage to the valves in the leg veins. Graduated compression stockings are worn on the legs from the arch of the foot to just above or below the knee. These stockings are tight at the ankle and become looser as they go up the leg. This causes a gentle compression (or pressure) up the leg. The pressure keeps blood from pooling and clotting.

How can pulmonary embolism be prevented?

Preventing pulmonary embolism (PE) begins with preventing deep vein thrombosis (DVT). Knowing whether you're at risk for DVT and taking steps to lower your risk are important.

If you've never had a deep vein clot, but are at risk for it, these are steps you can take to decrease your risk.

  • Exercise your lower leg muscles during long car trips and airplane rides.

  • Get out of bed and move around as soon as you're able after having surgery or being ill. The sooner you move around, the lower your chance of developing a clot.

  • Take medicines to prevent clots after some types of surgery (as directed by your doctor).

  • Follow up with your doctor.

If you already have had DVT or pulmonary embolism, you can take additional steps to help keep new blood clots from forming:

  • Visit your doctor for regular checkups.

  • Use compression stockings to prevent chronic swelling in your legs after DVT (as directed by your doctor).

Contact your doctor at once if you have any signs or symptoms of DVT or pulmonary embolism.

SOURCE: National Heart Lung and Blood Institute, National Institutes of Health


Deep vein thrombosis (DVT) occurs in the _______________. See Answer

Health Solutions From Our Sponsors