Embolism

Definition

An embolism is an obstruction in a blood vessel due to a blood clot or other foreign matter that gets stuck while traveling through the bloodstream. The plural of embolism is emboli.

Description

Emboli have moved from the place where they were formed through the bloodstream to another part of the body, where they obstruct an artery and block the flow of blood. The emboli are usually formed from blood clots but are occasionally comprised of air, fat, or tumor tissue. Embolic events can be multiple and small, or single and massive. They can be life-threatening and require immediate emergency medical care. There are three general categories of emboli: arterial, gas, and pulmonary. Pulmonary emboli are the most common.

Arterial embolism

In arterial emboli, blood flow is blocked at the junction of major arteries, most often at the groin, knee, or thigh. Arterial emboli are generally a complication of heart disease. An arterial embolism in the brain (cerebral embolism) causes stroke, which can be fatal. An estimated 5-14% of all strokes are caused by cerebral emboli. Arterial emboli to the extremities can lead to tissue death and amputation of the affected limb if not treated effectively within hours. Intestines and kidneys can also suffer damage from emboli.

Gas embolism

Gas emboli result from the compression of respiratory gases into the blood and other tissues due to rapid changes in environmental pressure, for example, while flying or scuba diving. As external pressure decreases, gases (like nitrogen) that are dissolved in the blood and other tissues become small bubbles that can block blood flow and cause organ damage.

Pulmonary embolism

In a pulmonary embolism, a common illness, blood flow is blocked at a pulmonary artery. When emboli block the main pulmonary artery, and in cases where there are no initial symptoms, a pulmonary embolism can quickly become fatal. According to the American Heart Association, an estimated 600,000 Americans develop pulmonary emboli annually and 60,000 die from it.

A pulmonary embolism is difficult to diagnose. Less than 10% of patients who die from a pulmonary embolism were diagnosed with the condition. More than 90% of cases of pulmonary emboli are complications of deep vein thrombosis, blood clots in the deep vein of the leg or pelvis.

Causes and symptoms

Arterial emboli are usually a complication of heart disease where blood clots form in the heart's chambers. Gas emboli are caused by rapid changes in environmental pressure that could happen when flying or scuba diving. A pulmonary embolism is caused by blood clots that travel through the blood stream to the lungs and block a pulmonary artery. More than 90% of the cases of pulmonary embolism are a complication of deep vein thrombosis, which typically occurs in patients who have had orthopedic surgery and patients with cancer or other chronic illnesses like congestive heart failure.

Risk factors for arterial and pulmonary emboli include: prolonged bed rest, surgery, childbirth, heart attack, stroke, congestive heart failure, cancer, obesity, a broken hip or leg, oral contraceptives, sickle cell anemia, chest trauma, certain congenital heart defects, and old age. Risk factors for gas emboli include: scuba diving, amateur plane flight, exercise, injury, obesity, dehydration, excessive alcohol, colds, and medications such as narcotics and antihistamines.

Symptoms of an arterial embolism include:

• severe pain in the area of the embolism
• pale, bluish cool skin
• numbness
• tingling
• muscular weakness or paralysis

Common symptoms of a pulmonary embolism include:

• labored breathing, sometimes accompanied by chest pain
• a rapid pulse
• a cough that may produce sputum
• a low-grade fever
• fluid build-up in the lungs

Less common symptoms include:

• coughing up blood
• pain caused by movement or breathing
• leg swelling
• bluish skin
• fainting
• swollen neck veins

Diagnosis

An embolism can be diagnosed through the patient's history, a physical exam, and diagnostic tests. The use of various tests may change, as physicians and clinical guidelines evaluate the most effective test in terms of accuracy and cost. For arterial emboli, cardiac ultrasound and/or arteriography are ordered. For a pulmonary embolism, a chest x ray, lung scan, pulmonary angiography, electrocardiography, arterial blood gas measurements, and venography or venous ultrasound could be ordered.

Diagnosing an arterial embolism

Ultrasound uses sound waves to create an image of the heart, organs, or arteries. The technologist applies gel to a hand-held transducer, then presses it against the patient's body. The sound waves are converted into an image that can be displayed on a monitor. Performed in an outpatient diagnostic laboratory, the test takes 30-60 minutes.

An arteriogram is an x ray in which a contrast medium is injected to make the arteries visible. It can be performed in a radiology unit, outpatient clinic, or diagnostic center of a hospital.

Diagnosing a pulmonary embolism

A chest x ray can show fluid build-up and detect other respiratory diseases. The perfusion lung scan shows poor flow of blood in areas beyond blocked arteries. The patient inhales a small amount of radiopharmaceutical and pictures of airflow into the lungs are taken with a gamma camera. Then a different radiopharmaceutical is injected into an arm vein and lung blood flow is scanned. A normal result essentially rules out a pulmonary embolism. A lung scan can be performed in a hospital or an outpatient facility and takes about 45 minutes.

Pulmonary angiography is one of the most reliable tests for diagnosing a pulmonary embolism. Pulmonary angiography is a radiographic test that involves injection of a radio contrast agent to show the pulmonary arteries. A cinematic camera records the blood flow through the patient, who lies on a table. Pulmonary angiography is usually performed in a hospital's radiology department and takes 30-60 minutes.

An electrocardiograph shows the heart's electrical activity and helps distinguish a pulmonary embolism from a heart attack. Electrodes covered with conducting jelly are placed on the patient's chest, arms, and legs. Impulses of the heart's activity are traced on paper. The test takes about 10 minutes.

Arterial blood gas measurements are sometimes helpful but, alone, they are not diagnostic for pulmonary embolism. Blood is taken from an artery instead of a vein, usually in the wrist.

Venography is used to look for the most likely source of a pulmonary embolism, deep vein thrombosis. It is very accurate, but it is not used often, because it is painful, expensive, exposes the patient to a fairly high dose of radiation, and can cause complications. Venography identifies the location, extent, and degree of attachment of the blood clots and enables the condition of the deep leg veins to be assessed. A contrast solution is injected into a foot vein through a catheter. The physician observes the movement of the solution through the vein with a fluoroscope while a series of x rays are taken. Venography takes between 30-45 minutes and can be done in a physician's office, a laboratory, or a hospital. Radionuclide venography, in which a radioactive isotope is injected, is occasionally used, especially if a patient has had reactions to contrast solutions. Venous ultrasound is the preferred evaluation of leg veins.

As noninvasive methods such as high-speed computed tomography (CT) scanning improve, they may be used to diagnose emboli. For instance, spiral (also called helical) CT scans may be the preferred tool for diagnosing pulmonary embolism in pregnant women.

Treatment

Patients with emboli require immediate hospitalization. They are generally treated with clot-dissolving and/or clot-preventing drugs. Thrombolytic therapy to dissolve blood clots is the definitive treatment for a severe pulmonary embolism. Streptokinase, urokinase, and recombinant tissue plasminogen activator (TPA) are used. Heparin has been the anticoagulant drug of choice for preventing formation of blood clots. A new drug has been approved for treatment of acute pulmonary emboli. Called fondaparinux (Arixtra), it usually is administered with Warfarin, an oral anticoagulant. Warfarin is sometimes used with other drugs to treat acute embolism events and is usually continued after the hospitalization to help prevent future emboli. Arixtra also has been used on an ongoing basis to prevent pulmonary emboli.

In the case of an arterial embolism, the affected limb is placed in a dependent position and kept warm. Embolectomy is the treatment of choice in the majority of early cases of arterial emboli in the extremities. In this procedure, a balloon-tipped catheter is inserted into the artery to remove thromboembolic matter.

With a pulmonary embolism, oxygen therapy is often used to maintain normal oxygen concentrations. For people who can't take anticoagulants and in some other cases, surgery may be needed to insert a device that filters blood returning to the heart and lungs.

Prognosis

Of patients hospitalized with an arterial embolism, 25-30% die, and 5-25% require amputation of a limb. About 10% of patients with a pulmonary embolism die suddenly within the first hour of onset of the condition. The outcome for all other patients is generally good; only 3% of patients die who are properly diagnosed early and treated. In cases of an undiagnosed pulmonary embolism, about 30% of patients die.

Prevention

Embolism can be prevented in high risk patients through antithrombotic drugs such as heparin, venous interruption, gradient elastic stockings, and intermittent pneumatic compression of the legs. The combination of graduated compression stockings and low-dose heparin is significantly more effective than low-dose heparin alone.

Gradient elastic stockings, also called antiembolism stockings, decrease the risk of blood clots by compressing superficial leg veins and forcing blood into the deep veins. They can be knee-, thigh-, or waist-length. Many physicians order the use of stockings before surgery and until there is no longer an elevated risk of developing blood clots. The risk of deep vein thrombosis after surgery is reduced 50% with the use of these stockings. The American Heart Association recommends that the use of graduated compression stockings be considered for all high-risk surgical patients.

Intermittent pneumatic compression involves wrapping knee- or thigh-high cuffs around the legs to prevent blood clots. The cuffs are connected to a pump that inflates and deflates, mimicking the heart's normal pumping action and reducing the pooling of blood. Intermittent pneumatic compression can be used during surgery and recovery and continues until there is no longer an elevated risk of developing blood clots. The American Heart Association recommends the use of intermittent pneumatic compression for patients who cannot take anticoagulants, for example, spinal cord and brain trauma patients.

Resources

PERIODICALS

Doyle, Nora M., et al. "Diagnosis of Pulmonary Embolism: A Cost-effective Analysis." American Journal of Obstetrics and Gynecology September 2004: 1019-1024.

Truelove, Christiane. "First for Pulmonary Embolism." Med Ad News August 2004: 82.

ORGANIZATIONS

American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. 〈http://www.americanheart.org〉.

KEY TERMS

Anticoagulants— Drugs that suppress, delay, or prevent blood clots. Anticoagulants are used to treat embolisms.

Artery— A blood vessel that carries blood from the heart to other body tissues. Embolisms obstruct arteries.

Deep vein thrombosis— A blood clot in the calf's deep vein. This frequently leads to pulmonary embolism if untreated.

Emboli— Clots or other substances that travel through the blood stream and get stuck in an artery, blocking circulation.

Thrombolytics— Drugs that dissolve blood clots. Thrombolytics are used to treat embolisms.

Embolism

An embolism is the sudden blockage of a blood vessel by a blood clot that has been brought to that location by the bloodstream. The clot, called an embolus, from the Greek word meaning plug, is a blood clot that has formed inside the circulatory system and is floating in the bloodstream. It will remain on the move until it encounters a blood vessel too small for it to fit through, where it will plug the vessel and prevent any further circulation of blood through it. The plural of embolism is emboli.

A blood clot that forms in a given location and remains there is called a thrombus, from the Greek word for clot.

An embolism is named by the location in which the clot lodges. A pulmonary embolism is an embolus that has plugged a blood vessel, usually an artery, in one of the lungs. A coronary embolism is obscuring the channel in one of the coronary arteries, which feed the heart muscle. A cerebral embolism lodges in a blood vessel in the brain and perhaps precipitates a stroke.

Of the three general categories of emboli—coronary (arterial), cerebral (gas), and pulmonary—pulmonary emboli are the most common.

In coronary (arterial) emboli, blood flow is blocked at the junction of major arteries, most often at the groin, knee, or thigh. Arterial emboli are generally a complication of heart disease. An arterial embolism in the brain (cerebral embolism) causes stroke, which can be fatal. An estimated 5 to 14% of all strokes are caused by cerebral emboli. Arterial emboli to the extremities can lead to tissue death and amputation of the affected limb if not treated effectively within hours. Intestines and kidneys can also suffer damage from emboli.

Cerebral (gas) emboli result from the compression of respiratory gases into the blood and other tissues due to rapid changes in environmental pressure, for example, while flying or scuba diving. As external pressure decreases, gases (like nitrogen) which are dissolved in the blood and other tissues become small bubbles that can block blood flow and cause organ damage.

In a pulmonary embolism, a common illness, blood flow is blocked at a pulmonary artery. When emboli block the main pulmonary artery and in cases where there are no initial symptoms, a pulmonary embolism can quickly become fatal. According to the American Heart Association, an estimated 600, 000 people in the United States develop pulmonary emboli annually and 60, 000 people die from it each year.

Common symptoms of a pulmonary embolism include:

• Labored breathing, sometimes accompanied by chest pain,
• A rapid pulse,
• A cough that may produce sputum,
• A low-grade fever, and
• Fluid build-up in the lungs.

Less common symptoms include:

• Coughing up blood,
• Pain caused by movement or breathing,
• Leg swelling,
• Bluish skin,
• Fainting, and
• Swollen neck veins.

Symptoms of an coronary embolism include:

• Severe pain in the area of the embolism,
• Pale, bluish cool skin,
• Numbness,
• Tingling, and
• Muscular weakness or paralysis.

Risk factors for coronary and pulmonary emboli include: prolonged bed rest, surgery, childbirth, heart attack, stroke, congestive heart failure, cancer, obesity, a broken hip or leg, oral contraceptives, sickle cell anemia, chest trauma, certain congenital heart defects, and old age. Risk factors for cerebral emboli include: scuba diving, amateur airplane flight, exercise, injury, obesity, dehydration, excessive alcohol, colds, and medications such as narcotics and antihistamines.

A pulmonary embolism is difficult to diagnose, with less than 10% of patients who die from a pulmonary embolism being diagnosed with the condition. More than 90% of cases of pulmonary emboli are complications of deep vein thrombosis, blood clots in the deep vein of the leg or pelvis.

Arterial emboli are usually a complication of heart disease where blood clots form in the heart’s chambers. Gas emboli are caused by rapid changes in environmental pressure that could happen when flying or scuba diving. A pulmonary embolism is caused by blood clots that travel through the blood stream to the lungs and block a pulmonary artery. More than 90% of the cases of pulmonary embolism are a complication of deep vein thrombosis, which typically occurs in patients who have had orthopedic surgery and in patients with cancer and other chronic illnesses like congestive heart failure.

When an embolus plugs a blood vessel, the tissues that are bathed by the blood in the vessel will die when the blood supply is cut off. Death of tissue resulting from the lack of blood is called an infarct. If the embolism is in a coronary artery and the infarct is in the heart muscle it is a heart attack. The seriousness of the attack is determined by which vessel the clot blocks and how much of the heart muscle is infracted (that is, the deadening of the muscle as a result of loss of blood).

The same situation applies to other organs. A cerebral embolism can cause brain damage and bring about a stroke. A pulmonary embolism causes damage to the lung tissue that can be serious. Any of these embolisms can be fatal and must be treated quickly.

An embolism can be diagnosed through the patient’s history, a physical examination, and diagnostic tests. For coronary emboli, cardiac ultrasound and/or arteriography are ordered. For a pulmonary embolism, a chest x ray, lung scan, pulmonary angiography, electrocardiography, arterial blood gas measurements, and venography or venous ultrasound could be ordered.

Patients with emboli require immediate hospitalization. They are generally treated with clot-dissolving and/or clot-preventing drugs. Thrombolytic therapy to dissolve blood clots is the definitive treatment for a very severe pulmonary embolism. Streptokinase, urokinase, and recombinant tissue plasminogen activator (TPA) are used. Heparin is the anticoagulant drug of choice for preventing formation of blood clots. Warfarin (Coumadin^®), an oral anticoagulant, is sometimes used concurrently and is usually continued after the hospitalization.

What causes most emboli to form is not known. Some may form after surgery if air gets into the bloodstream.

Embolism

What Is an Embolism?

How Do Emboli Happen?

What Are the Signs and Symptoms of Embolism?

How Do Doctors Diagnose and Treat Embolism?

Resource

An embolism (EM-bo-liz-um) is a blockage in the bloodstream, caused by a blood clot, air bubble, fatty tissue, or other substance that plugs a blood vessel.

KEYWORDS

for searching the Internet and other reference sources

Circulatory system

Coagulation

The body’s circulatory system is like a huge network of small roads and large interstate highways. It is important that blood continuously flow through the body to carry nutrients, oxygen, and other substances to cells and organs. But like a road, sometimes a part of the circulatory system can become blocked by an accident.

What Is an Embolism?

An embolism is a blockage that plugs up an artery in the body and slows or even stops blood flow to the area of the body supplied by the artery. Many substances can cause blockages. Usually, the embolus (EM-bo-lus) is something small that has broken free from another part of the body and has traveled through the bloodstream until it gets jammed in a blood vessel that is too narrow for it to pass freely.

Emboli (EM-bo-ly; plural of embolus) are dangerous. They may cause death if they block a major artery, such as the large pulmonary artery that runs through the lungs. They also may cause tissue to die if they prevent blood flow to the area. Emboli are sometimes called “accidents waiting to happen.”

How Do Emboli Happen?

The most common type of embolism results from the clotting* of blood. When blood clots form inside veins, which is a process called thrombosis*, they may break free and travel to the pulmonary artery. The pulmonary artery carries blood from the right side of the heart into the lungs. In the lungs, blood disposes of carbon dioxide and picks up more oxygen. When blood clots get stuck in the pulmonary artery, they prevent blood from picking up oxygen. This is a medical emergency that causes symptoms similar to a heart attack.

* clotting

is a process in which blood changes into a Jellylike mass that stops the flow of blood.

* thrombosis

is the formation or development of a blood clot or thrombus.

Other substances may cause embolism, for example:

• Bubbles. This sometimes occurs in underwater divers as they ascend, and as the compressed nitrogen bubbles out of solution. This is called “the bends.” It also can happen during injections of fluids or medications into veins or arteries, which is one reason why doctors and nurses squeeze the air out of needles before injecting patients.
• Tumors*. These may grow and block blood flow, or a piece of a tumor may break off into the bloodstream and get caught in another part of the body.
• Fat. This occurs when fat breaks off in an area of the body. For example, after a serious injury occurs to a body part like the liver, fat may break off and travel through the bloodstream.
• Bone fragments. A bone chip from a broken arm or leg may become lodged in an artery.

* tumors

usually refers to an abnormal growth of body tissue that has no physiologic purpose and is not an inflammation. Tumors may or may not be cancerous.

The embolism may occur in any artery, but often occurs in the pulmonary arteries. This is because all the blood returning to the heart from the body is pumped through the pulmonary arterial system first.

What Are the Signs and Symptoms of Embolism?

Symptoms of a pulmonary embolism include chest pain that can feel worse when breathing deeply; shortness of breath; coughing, which sometimes results in blood coming up from the lungs; dizziness; anxiety*; sweating; and rapid breathing and heartbeat.

These symptoms are similar to those of a heart attack, and some symptoms even resemble those of an anxiety attack. But sometimes embolism does not cause any symptoms at all.

* anxiety

may be experienced as a troubled feeling, a sense of dread, fear of the future, or distress over a possible threat to a person’s physical or mental well-being.

How Do Doctors Diagnose and Treat Embolism?

Embolism is often difficult for doctors to diagnose. Doctors may use an x-ray, a CT scan*, or a lung scan to check for the embolism. Sometimes dye is injected into the person to make it easier to see the embolism on the x-ray or scan.

* CT scans

or CAT scans are the short form for computerized axial tomography, which uses computers to view structures inside the body.

Pulmonary emboli develop in as many as 500,000 Americans each year, and up to 10 percent die within the first hour. With treatment, many are saved and lead normal lives. Doctors may use drugs that dissolve the embolism and prevent others from forming. Exercise, weight loss if needed, and a proper diet can help prevent emboli from forming.

See also

Bends

Clotting

Phlebitis

Thrombosis

Resource

The U.S. National Heart, Lung, and Blood Institute posts a fact sheet about pulmonary embolism at its website. http://www.nhlbi.nih.gov/nhlbi/infcntr/topics/pulemb.htm

Embolism

An embolism is the sudden blockage of a blood vessel by a blood clot that has been brought to that location by the bloodstream. The clot, called an embolus, from the Greek word meaning plug, is a blood clot that has formed inside the circulatory system and is floating in the bloodstream. It will remain on the move until it encounters a blood vessel too small for it to fit through, where it will plug the vessel and prevent any further circulation of blood through it.

A blood clot that forms in a given location and remains there is called a thrombus, from the Greek word for clot.

An embolism is named by the location in which the clot lodges. A pulmonary embolism is an embolus that has plugged a blood vessel, usually an artery, in one of the lungs. A coronary embolism is obscuring the channel in one of the coronary arteries , which feed the heart muscle. A cerebral embolism lodges in a blood vessel in the brain and perhaps precipitates a stroke .

When an embolus plugs a blood vessel, the tissues that are bathed by the blood in the vessel will die when the blood supply is cut off. Death of tissue resulting from the lack of blood is called an infarct. If the embolism is in a coronary artery and the infarct is in the heart muscle it is a heart attack. The seriousness of the attack is determined by which vessel the clot blocks and how much of the heart muscle is infarcted.

The same situation applies to other organs. A cerebral embolism can cause brain damage and bring about a stroke. A pulmonary embolism causes damage to the lung tissue that can be serious. Any of these embolisms can be fatal and must be treated quickly.

Drugs can be given to dissolve the clot and other drugs can be taken to prevent the formation of any more clots.

What causes most emboli to form is not known. Some may form after surgery if air gets into the bloodstream.

embolism When fragments, usually of blood clot, are let loose in the bloodstream, they lodge in and obstruct the first vessels they encounter which are too narrow for them to pass. Such a fragment is known as an embolus (plural emboli) and the event as embolism. Pieces may break off from a clot (thrombus) which has formed, usually during prolonged immobility, in the deep veins of the legs or pelvis (deep vein thrombosis — DVT). The clots travel to the heart through progressively larger veins, thence from the right side of the heart to the lungs; there they obstruct branches of the pulmonary artery, where the severity of their effects depends on their size and number. Large pulmonary emboli can be fatal; very small ones lodge in microscopic vessels causing some impairment of oxygen intake. Thrombi which form on damaged lining of the left heart valves or of major arteries can release fragments which reach the brain (cerebral embolism) causing a type of stroke. There can also be fat embolism, when particles enter veins from the marrow of fractured bones, or air embolism if air is injected or sucked into an open vein.

Sheila Jennett