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 then travels to a lung artery, where it suddenly blocks blood flow.

A blood clot that forms in a blood vessel in an 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 an 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. The clot is called a thrombus.

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 happen 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 common causes include:

• A fat embolus (often due to the breaking of a large bone)

• Amniotic fluid embolus

• Air bubbles

• Deep vein thrombosis in the upper body

• Clots on an indwelling IV (intravenous) catheter that 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, atrial fibrillation or atrial flutter, chronic obstructive pulmonary disease (COPD), high blood pressure, stroke, and inflammatory bowel disease

• Certain medicines, such as 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

• Indwelling central venous catheters

What are the symptoms of a pulmonary embolism?

Each person may experience symptoms differently. The most common symptoms include:

• Sudden shortness of breath (most common)

• Chest pain (usually worse with breathing)

• A feeling of anxiety

• A feeling of dizziness, lightheadedness, or fainting

• Fast heart rate (tachycardia)

• Rapid breathing

• Palpitations (fast, strong, or irregular heartbeat)

• Coughing 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 happen only when standing or walking)

• Swelling in the leg

• Soreness, redness, or warmth in the leg(s)

• Redness or discolored skin

If your healthcare provider thinks you have a PE, they 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 or lung problems.

The symptoms of a PE may look like other medical conditions or problems. Always talk with a healthcare provider for a diagnosis.

How is pulmonary embolism diagnosed?

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

Along with a complete health 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.

• CT scan. This is an imaging test that uses X-rays and a computer to make detailed images of the body. A CT scan shows details of the bones, muscles, fat, and organs. 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.

• MRI. This imaging test uses a combination of a magnetic field, radio waves, and a computer to make detailed images of organs and structures within the body without the use of X-rays.

• 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.

• Blood tests. Blood tests are used to check the blood's clotting status, including a test called D-dimer level. Other blood tests 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 choices for pulmonary embolism (PE) include:

• Anticoagulants. Also described as blood thinners, these medicines 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 and heparin.

• Fibrinolytic therapy. Also called thrombolytic therapy or clot busters, these medicines are given intravenously (IV or into a vein), or a catheter is used to deliver the medicine directly to the clot to break down the clot. These medicines are generally used in more severe cases due to the risk of bleeding.

• 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), you develop more clots even with anticoagulation treatment, or when you have bleeding problems from anticoagulation medicines.

• 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 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 medicine.

An important aspect of treating a PE is treatment to prevent more embolisms.

What are possible 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, especially a large PE or many clots, can quickly cause serious, life-threatening problems and even death.

Treatment of a PE is often done with anti-coagulation medicines or blood thinners. These medicines can put you at 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 (sticky) stools

• Belly (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 symptoms, you need to get medical care right away.

What can I do to prevent a pulmonary embolism?

You can help prevent a PE by:

• Exercising regularly

• Keeping a healthy weight

• Eating a healthy diet

• Taking medicines as prescribed

• Not smoking

You can help prevent DVT with:

• Compression stockings. These are elastic stockings that squeeze or compress the veins and prevent blood from flowing backward.

• Pneumatic compression devices. These are 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. Do this as soon as possible after surgery or illness. Movement can help keep clots from forming by getting blood moving.

• Medicine. Anticoagulants and aspirin are often given to help prevent DVT.

Many people are still at risk for DVTs for a time after they go home from the hospital. It is important to continue treatment to prevent DVTs until this risk goes away. That usually takes 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, 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. Medicines, filters to keep clots from getting to the lungs, and surgery are used to treat PEs.

• A PE, especially 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 healthcare provider:

• Know the reason for your visit and what you want to happen.

• 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 name of a new diagnosis and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.

• Know why a new medicine or treatment is prescribed and how it will help you. Also know what the side effects are and when they should be reported.

• Ask if your condition can be treated in other ways.

• Know why a test or procedure is recommended and what the results could mean.

• Know what to expect if you do not take the medicine or have the test or procedure.

• 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, including after office hours, on weekends, and holidays.