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Pulmonary Embolism

What is a pulmonary embolism?

A pulmonary embolism (PE) is a blood clot that develops in a blood vessel in the body (often in the leg). It travels to a lung artery where it suddenly blocks blood flow.

A blood clot that forms in a blood vessel in one area of the body, breaks off, and travels to another area of the body in the blood is called an embolus. An embolus can lodge itself in a blood vessel. This can block the blood supply to a particular organ. This blockage of a blood vessel by an embolus is called an embolism.

The heart, arteries, capillaries, and veins make up the body's circulatory system. Blood is pumped with great force from the heart into the arteries. From there blood flows into the capillaries (tiny blood vessels in the tissues). Blood returns to the heart through the veins. As it moves through the veins back to the heart, blood flow slows. Sometimes this slower blood flow may lead to clot formation.

What causes a pulmonary embolism?

Blood clotting is a normal process to prevent bleeding. The body makes blood clots and then breaks them down. Under certain circumstances, the body may be unable to break down a clot. This may result in a serious health problem.

When blood clots in a vein, it may be due to the slowed blood flow, an abnormality in clot forming, or from an injury to the blood vessel wall.

Blood clots can form in arteries and veins. Clots formed in veins are called venous clots. Veins of the legs can be superficial veins (close to the surface of the skin) or deep veins (located near the bone and surrounded by muscle).

Venous clots most often occur in the deep veins of the legs. This is called deep vein thrombosis (DVT). Once a clot has formed in the deep veins of the leg, there is a potential for part of the clot to break off and travel through the blood to another area of the body, often the lung. DVT is the most common cause of a pulmonary embolism.

Other less frequent sources of pulmonary embolism are a fat embolus (often linked to the breaking of a large bone), amniotic fluid embolus, air bubbles, and a deep vein thrombosis in the upper body. Clots may also form on the end of an indwelling intravenous (IV) catheter, break off, and travel to the lungs.

Who is at risk for a pulmonary embolism?

Risk factors for pulmonary embolism include:

  • Genetic conditions that increase the risk of blood clot formation
  • Family history of blood clotting disorders
  • Surgery or injury (especially to the legs) or orthopedic surgery
  • Situations in which mobility is limited, such as extended bed rest, flying or riding long distances, or paralysis
  • Previous history of clots
  • Older age
  • Cancer and cancer therapy
  • Certain medical conditions, such as heart failure, chronic obstructive pulmonary disease (COPD), high blood pressure, stroke, and inflammatory bowel disease
  • Certain medications, such birth control pills and estrogen replacement therapy
  • During and after pregnancy, including after cesarean section
  • Obesity
  • Enlarged veins in the legs (varicose veins)
  • Cigarette smoking

What are the symptoms of a pulmonary embolism?

The following are the most common symptoms for pulmonary embolism (PE). However, each person may experience symptoms differently:

  • Sudden shortness of breath (most common)
  • Chest pain (usually worse with breathing)
  • A feeling of anxiety
  • A feeling of dizziness, lightheadedness, or fainting
  • Irregular heartbeat
  • Palpitations (heart racing)
  • Coughing and/or coughing up blood
  • Sweating
  • Low blood pressure

You may also have symptoms of deep vein thrombosis (DVT), such as:

  • Pain in the affected leg (may occur only when standing or walking)
  • Swelling in the leg
  • Soreness, tenderness, redness, and/or warmth in the leg(s)
  • Redness and/or discolored skin

If your doctor thinks you have a PE, he or she will check your legs for signs of deep vein thrombosis.

The type and extent of symptoms of a PE will depend on the size of the embolism and whether you have heart and/or lung problems.

The symptoms of a PE may look like other medical conditions or problems. Always consult a health care provider for a diagnosis.

How is pulmonary embolism diagnosed?

Pulmonary embolism (PE) is often difficult to diagnose because the symptoms of PE are a lot like those of many other conditions and diseases.

Along with a complete medical history and physical exam, tests used to look for a PE may include:

  • Chest X-ray. This imaging test is used to assess the lungs and heart. Chest X-rays show information about the size, shape, contour, and anatomic location of the heart, lungs, bronchi (large breathing tubes), aorta and pulmonary arteries, and mediastinum (area in the middle of the chest separating the lungs).
  • Ventilation-perfusion scan (V/Q scan). For this nuclear radiology test, a small amount of a radioactive substance is used to help examine the lungs. A ventilation scan evaluates ventilation, or the movement of air into and out of the bronchi and bronchioles. A perfusion scan evaluates blood flow within the lungs.
  • Pulmonary angiogram. This X-ray image of the blood vessels is used to evaluate various conditions, such as aneurysm (bulging of a blood vessel), stenosis (narrowing of a blood vessel), or blockages. A dye (contrast) is injected through a thin flexible tube placed in an artery. This dye makes the blood vessels show up on X-ray.
  • Computed tomography (CT or CAT scan). This imaging test uses a combination of X-rays and computer technology to produce horizontal, or axial, images (often called slices) of the body. CT with contrast enhances the image of the blood vessels in the lungs. Contrast is a dye-like substance injected into a vein that causes the organ or tissue under study to show up more clearly on the scan.
  • Magnetic resonance imaging (MRI). This imaging test uses a combination of a magnetic field, radiofrequencies, and a computer to make detailed images of organs and structures within the body.
  • Duplex ultrasound (US). This type of vascular ultrasound is done to assess blood flow and the structure of the blood vessels in the legs. (Blood clots from the legs often dislodge and travel into the lung.) US uses high-frequency sound waves and a computer to create images of blood vessels, tissues, and organs.
  • Lab tests. Blood tests are used to check the blood's clotting status, including a test called D-dimer level. Other blood work may include testing for genetic disorders that may contribute to abnormal clotting of the blood. Arterial blood gases may be checked to see how much oxygen is in the blood.
  • Electrocardiogram (EKG). This is one of the simplest and fastest tests used to evaluate the heart. Electrodes (small, sticky patches) are placed at certain spots on the chest, arms, and legs. The electrodes are connected to an EKG machine by lead wires. The electrical activity of the heart is measured, interpreted, and printed out.

How is a pulmonary embolism treated?

Treatment options for pulmonary embolism (PE) include:

  • Anticoagulants. Also described as blood thinners, these medications decrease the ability of the blood to clot. This helps stop a clot from getting bigger and keep new clots from forming. Examples include warfarin (Coumadin) and heparin.
  • Fibrinolytic therapy. Also called clot busters, these medications are given intravenously (IV or into a vein) to break down the clot. These drugs are only used in life-threatening situations.
  • Vena cava filter. A small metal device placed in the vena cava (the large blood vessel that returns blood from the body to the heart) may be used to keep clots from traveling to the lungs. These filters are generally used when you can't get anticoagulation treatment (for medical reasons), develop more clots even with anticoagulation treatment, or when you have bleeding problems from anticoagulation medications.
  • Pulmonary embolectomy. Rarely used, this is surgery done to remove a PE. It is generally done only in severe cases when your PE is very large, you can't get anticoagulation and/or thrombolytic therapy due to other medical problems or you haven't responded well to those treatments, or your condition is unstable.
  • Percutaneous thrombectomy. A long, thin, hollow tube (catheter) can be threaded through the blood vessel to the site of the embolism guided by X-ray. Once the catheter is in place, it's used to break up the embolism, pull it out, or dissolve it using thrombolytic medication.

An important aspect of treating a PE is preventive treatment to prevent formation of additional embolisms.

What are the complications of a pulmonary embolism?

A pulmonary embolism (PE) can cause a lack of blood flow that leads to lung tissue damage. It can cause low blood oxygen levels that can damage other organs in the body, too.

A PE, particularly a large PE or many clots, can quickly cause serious life-threatening problems and, even death.

Treatment of a PE often involves anti-coagulation medications or blood thinners. These drugs can put you at a risk for excessive bleeding if they thin your blood too much. Excessive bleeding is bleeding that won't stop after you apply pressure for 10 minutes. Other symptoms of bleeding to watch for include:

Signs of bleeding in the digestive system:

  • Bright red vomit or vomit that looks like coffee grounds
  • Bright red blood in your stool or black, tarry stools
  • Abdominal pain

Signs of bleeding in the brain:

  • Severe headache
  • Sudden vision changes
  • Sudden loss of movement or feeling in your legs or arms
  • Memory loss or confusion

If you have any of these, you need to get treatment right away.

Can a pulmonary embolism be prevented?

Because pulmonary embolism (PE) is often caused by a blood clot that originally formed in the legs, and because it is often difficult to detect a DVT before problems start, the prevention of DVTs is key in the prevention of PE.

Treatment to prevent DVTs includes:

Non-invasive mechanical measures

Non-drug ways to prevent DVT include:

  • Compression stockings (elastic stockings that squeeze or compress the veins and prevent blood from flowing backward)
  • Pneumatic compression devices (sleeves on the legs that are connected to a machine that provides alternating pressure on the legs to keep blood moving)
  • Getting up and moving as soon as possible after surgery or illness (movement can help keep clots from forming by stimulating blood circulation)


Anticoagulants and aspirin are often given to help prevent DVT.

Many people remain at risk for developing DVTs for a period after they are either discharged from the hospital. It is important that treatment to prevent DVTs continue until the risk has been resolved, usually about 3 to 6 months.

Key points about pulmonary embolisms

  • A pulmonary embolism (PE) is a blood clot that develops in a blood vessel elsewhere in the body (often the leg), travels to an artery in the lung, and suddenly forms a blockage of the artery.
  • Abnormal blood clots can form due to problems such as "sluggish" blood flow through the veins, an abnormality in clot forming factors, and/or an injury to the blood vessel wall.
  • A wide variety of conditions and risk factors have been linked to PEs.
  • Sudden shortness of breath is the most common symptom of a PE.
  • PE is often difficult to diagnose because the signs and symptoms of PE are a lot like those of many other conditions and diseases. Imaging tests and blood tests are used to look for a PE.
  • An important aspect of treating a PE is preventing additional clots. Medications, filters to keep clots from getting to the lungs, and surgery are used to treat PEs.
  • A PE, particularly a large PE or many clots, can quickly cause serious life-threatening consequences and death.

Next steps

Tips to help you get the most from a visit to your health care provider:

  • Before your visit, write down questions you want answered.
  • Bring someone with you to help you ask questions and remember what your provider tells you.
  • At the visit, write down the names of new medicines, treatments, or tests, and any new instructions your provider gives you.
  • If you have a follow-up appointment, write down the date, time, and purpose for that visit.
  • Know how you can contact your provider if you have questions.
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