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An embolus is a blood clot, bit of tissue or tumor, gas bubble, or other foreign body that circulates in the blood stream until it becomes stuck in a blood vessel.
When a blood clot develops in an artery and remains in place, it is called a thrombosis. If all or part of the blockage breaks away and lodges in another part of the artery, it is called an embolism. Blockage of an artery in this manner can be the result of a blood clot, fat cells, or an air bubble.
When an embolus blocks the flow of blood in an artery, the tissues beyond the plug are deprived of normal blood flow and oxygen. This can cause severe damage and even death of the tissues involved.
Emboli can affect any part of the body. The most common sites are the legs and feet. When the brain is affected, it is called a stroke. When the heart is involved, it is called a heart attack or myocardial infarction (MI).
Causes and symptoms
A common cause of embolus is when an artery whose lining has become thickened or damaged, usually with age, allows cholesterol to build up more easily than normal on the artery wall. If some of the cholesterol breaks off, it forms an embolus. Emboli also commonly form from blood clots in a heart that has been damaged from heart attack or when the heart contracts abnormally from atrial fibrillation.
Other known causes are fat cells that enter the blood after a major bone fracture, infected blood cells, cancer cells that enter the blood stream, and small gas bubbles.
Symptoms of an embolus can begin suddenly or build slowly over time, depending on the amount of blocked blood flow.
If the embolus is in an arm or leg, there will be muscle pain, numbness or tingling, pale skin color, lower temperature in the limb, and weakness or loss of muscle function. If it occurs in an internal organ, there is usually pain and/or loss of the organ's function.
The following tests can be used to confirm the presence of an arterial embolism:
- Electrocardiogram, also known as an EKG or ECG. For this test, patches that detect electrical impulses from the heart are attached to the chest and extremities. The information is displayed on a monitor screen or a paper tape in the form of waves. Reduced blood and oxygen supply to the heart shows as a change in the shape of the waves.
- Noninvasive vascular tests. These involve measuring blood pressure in various parts of the body and comparing the results from each location. When there is a decrease in blood pressure beyond what is normal between two points, a blockage is presumed to be present.
- Angiography. In this procedure, a colored liquid material (a dye, or contrast material) that can be seen with x rays is injected into the blood stream through a small tube called a catheter. As the dye fills the arteries, they are easily seen on x ray motion pictures. If there is a blockage in the artery, it shows up as a sudden cut off in the movement of contrast material. Angiography is an expensive procedure and does carry some risk. The catheter may cause a blood clot to form, blocking blood flow. There is also the risk of poking the catheter through the artery or heart muscle. Some people may be allergic to the dye. The risk of any of these injuries occurring is small.
Arterial embolism can be treated with medication or surgery, depending on the extent and location of the blockage.
Atrial fibrillation — An arrhythmia; chaotic quivering of the arteries.
Thrombosis — A blockage in a blood vessel that builds and remains in one place.
Medication to dissolve the clot is usually given through a catheter directly into the affected artery. If the embolus was caused by a blood clot, medications that thin the blood will help reduce the risk of another embolism.
A surgeon can remove an embolus by making an incision in the artery above the blockage and, using a catheter inserted past the embolus, drag it out through the incision.
If the condition is severe, a surgeon may elect to bypass the blocked vessel by grafting a new vessel in its place.
An arterial embolism is serious and should be treated promptly to avoid permanent damage to the affected area. The outcome of any treatment depends on the location and seriousness of the embolism. New arterial emboli can form even after successful treatment of the first event.
Prevention may include diet changes to reduce cholesterol levels, medications to thin the blood, and practicing an active, healthy lifestyle.
American Heart Association. 7320 Greenville Ave. Dallas, TX 75231. (214) 373-6300. http://www.americanheart.org.
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