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
- 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
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 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?
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
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?
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:
- Have deep vein thrombosis (DVT, a blood clot in the leg) or a history of
- Have had pulmonary embolism before
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
Women who take hormone therapy or
birth control pills also are at increased risk
People with more than one risk factor are at higher risk for blood clots.
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
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
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?
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
- 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.
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.
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
- 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
SOURCE: National Heart Lung and Blood Institute, National Institutes of
Last Editorial Review: 4/15/2008