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A pulmonary embolism is a sudden blockage in a
lung artery, usually due to a blood clot that traveled to the lung from 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 a clot is large, or if there are many clots, pulmonary embolism can
cause death.
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 to the lung,
and block an artery.
More than 600,000 people in the United States have a pulmonary embolism
each year, and more than 60,000 of them die. Most of those who die do so
within 30 to 60 minutes after symptoms start. Pulmonary embolism is one of the
most common causes of death in hospitalized people who must remain in bed for
a long time.
Symptoms
Signs and symptoms of pulmonary embolism vary depending on the amount of
blood flow blocked in the lung by clots. Large clots or many clots are life
threatening and cause more severe symptoms. Smaller clots cause fewer symptoms
or no symptoms at all. It is important that you see your doctor immediately if
you have any symptoms of pulmonary embolism or deep
vein thrombosis (DVT).
Common Signs and Symptoms of Pulmonary Embolism
Pulmonary embolism usually occurs suddenly, causing the onset of new
symptoms. The most common signs and symptoms of pulmonary embolism are:
- Unexplained shortness of breath
- Chest pain that gets worse with a deep breath, coughing, or chest
movement
- Coughing up blood
Sometimes, small pulmonary emboli can occur over time. These emboli may
cause a more gradual onset of symptoms.
Other Signs and Symptoms
General, less-specific signs and symptoms may occur, including:
- Anxiety or feelings of dread
- Lightheadedness
- Fainting
- Rapid breathing
- Increased heart rate
- Sweating
Diagnosis
Your doctor will take a health history and perform a physical exam in order
to:
- Identify your risk factors for deep
vein thrombosis (DVT) and pulmonary embolism
- See how likely it is that you could have a pulmonary embolism
- Eliminate other possible causes for your symptoms
To help determine whether you have a pulmonary embolism or related disease
or condition, initial testing includes:
- EKG
or ECG (electrocardiogram) to measure the rate and regularity of your
heartbeat.
- Chest
x ray, which takes a picture of the lungs, heart, large arteries,
ribs, and the diaphragm.
- Duplex ultrasound, the most common test used to diagnose deep vein
clots. It uses sound waves to evaluate the flow of blood in your veins. A
gel is put on the skin of the leg. A hand-held device is placed on the leg
and passed back and forth over the affected area. This device sends sound
waves from the leg to an ultrasound machine. A computer then turns the
sounds into a picture. The picture is displayed on the computer screen,
where your doctor can see the blood flow in your leg. This is an indirect
way to diagnose a source of pulmonary embolism.
- Blood work:
- To check for inherited disorders that cause clots.
- To measure the amount of oxygen and carbon dioxide in the blood
(arterial blood gas). A pulmonary embolism may change the levels of
oxygen and carbon dioxide in the blood.
Your doctor will order additional tests based on how likely it is that you
have a pulmonary embolism and which tests are available. Tests could include:
- Ventilation-perfusion
lung scan (VQ scan), a test that uses a radioactive material to see
how well air and blood are flowing to all areas of the lung.
- Pulmonary
angiography, an accurate, invasive test used to diagnose pulmonary
embolism. A flexible tube called a catheter is threaded through the upper
thigh (groin) or arm to the blood vessels in the lung. Dye is injected
through the catheter and then an x-ray picture is taken to show the blood
flow through the blood vessels in the lungs. This test is not available at
all hospitals, and a trained specialist is required to perform the test.
- Spiral
computed tomography (CT) scan, a special type of x ray that takes
pictures of structures inside the body. Dye is injected into a vein,
allowing the doctors to see the blood vessels in the lungs on the x-ray
picture. This is a very quick test and results are available shortly after
the scan is completed.
- Magnetic
resonance imaging (MRI), a test that takes pictures of organs and
structures inside the body. MRI uses radio waves to make the image. In
many cases, an MRI can provide information that would not show on an x
ray.
- Echocardiogram,
a test that uses sound waves to check for blood clots inside the heart and
to check heart function. It can also determine other possible causes for
your symptoms.
- D-dimer, a blood test that measures a substance in the blood that is
released when a clot breaks up. High levels may indicate a clot. If your
test is normal, a pulmonary embolism is not likely.
Causes
Nine out of 10 cases of pulmonary embolism are caused by blood clots that
form in the legs (deep
vein thrombosis) and then travel to the lungs.
Leg clots can form when blood flow is restricted and slows down. This
happens when you do not 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.
Rarely, an air bubble, part of a tumor, or other tissue travels to the lung
and causes pulmonary embolism.
Reference:
National Heart, Lung, and Blood Institute, USA.
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