Massachusetts General Hospital

Carotid Artery Disease

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What is carotid artery disease?

Carotid artery disease, also called carotid artery stenosis, occurs when the carotid arteries, the main blood vessels that carry oxygenated blood to the brain, become narrowed. The narrowing of the carotid arteries is most commonly related to atherosclerosis (a build-up of plaque, which is a deposit of fatty substances, cholesterol, cellular waste products, calcium, and fibrin in the inner lining of an artery). Atherosclerosis, or "hardening of the arteries," is a vascular disease (disease of the arteries and veins). Carotid artery disease is similar to coronary artery disease, in which blockages occur in the arteries of the heart, and may cause a heart attack.

To better understand how carotid artery disease affects the brain, a basic review of the anatomy of the circulation system of the brain follows.

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What are the carotid arteries?

The main supply of blood to the brain is carried by the carotid arteries. The carotid arteries branch off from the aorta (the largest artery in the body) a short distance from the heart, and extend upward through the neck carrying oxygen-rich blood to the brain.

There are four carotid arteries: the right and left internal carotid arteries and the right and left external carotid arteries. One pair (external and internal) is located on each side of the neck. Just as a pulse can be felt in the wrists, a pulse can also be felt on either side of the neck over the carotid arteries.

Why are the carotid arteries important?

Because the carotid arteries deliver blood to the brain, carotid artery disease can have serious implications by reducing the flow of oxygen and nutrients to the brain. The brain needs a constant supply of oxygen and nutrients in order to function. Even a brief interruption in blood supply can cause problems. Brain cells begin to die after just a few minutes without blood or oxygen. If the narrowing of the carotid arteries becomes severe enough to block blood flow, or a piece of atherosclerotic plaque breaks off and obstructs blood flow to the brain, a stroke may occur.

What causes carotid artery disease?

Atherosclerosis is the most common cause of carotid artery disease. It is unknown exactly how atherosclerosis begins or what causes it. Atherosclerosis is a slow, progressive, vascular disease that may start as early as childhood. However, the disease has the potential to progress rapidly. It is generally characterized by the accumulation of fatty deposits along the innermost layer of the arteries. If the disease process progresses, plaque formation may take place. Plaque is made up of deposits of smooth muscle cells, fatty substances, cholesterol, calcium, and cellular waste products. This thickening narrows the arteries and can decrease blood flow or completely block the flow of blood to the brain.

What are the risk factors for carotid artery disease?

Atherosclerosis is thought to play an important role in the development of carotid artery disease. Risk factors associated with atherosclerosis include:

• older age

• male

• family history

• race or ethnicity

• genetic factors

• hyperlipidemia (elevated fats in the blood)

• hypertension (high blood pressure)

• smoking

• diabetes

• obesity

• diet high in saturated fat

• lack of exercise

A risk factor is anything that may increase a person's chance of developing a disease. It may be an activity, such as smoking, diet, family history, or many other things. Different diseases have different risk factors.

Although these risk factors increase a person's risk, they do not necessarily cause the disease. Some people with one or more risk factors never develop the disease, while others develop disease and have no known risk factors. Knowing your risk factors to any disease can help to guide you into the appropriate actions, including changing behaviors and being clinically monitored for the disease.

What are the symptoms of carotid artery disease?

Carotid artery disease may be asymptomatic (without symptoms) or symptomatic (with symptoms). Asymptomatic carotid disease is the presence of a significant amount of atherosclerotic build-up without obstructing enough blood flow to cause symptoms. Symptomatic carotid artery disease may result in either a transient ischemic attack (TIA) and/or a stroke (brain attack).

A transient ischemic attack (TIA) is a sudden or a temporary loss of blood flow to an area of the brain, usually lasting less than five minutes but not longer than 24 hours, with complete recovery. Symptoms of a TIA may include, but are not limited to, the following:

• sudden weakness or clumsiness of an arm and/or leg on one side of the body

• sudden paralysis (inability to move) of an arm and/or leg on one side of the body

• loss of coordination or movement

• confusion, dizziness, fainting, and/or headache

• numbness or loss of sensation (feeling) in the face

• numbness or loss of sensation in an arm and/or leg

• temporary loss of vision or blurred vision

• inability to speak clearly or slurred speech

TIA may be related to severe narrowing or blockage or from small pieces of an atherosclerotic plaque breaking off, traveling through the bloodstream, and lodging in small blood vessels in the brain. With TIA, there is rarely permanent brain damage.

Call for medical help immediately if you suspect a person is having a TIA, as it may be a warning sign that a stroke is about to occur. Not all strokes, however, are preceded by TIAs.

Stroke is another indicator of carotid artery disease. The symptoms of a stroke are the same as for a TIA. A stroke is loss of blood flow (ischemia) to the brain that continues long enough to cause permanent brain damage. Brain cells begin to die after just a few minutes without blood or oxygen. The area of dead cells in tissues is called an infarct.

The area of the brain that suffered the loss of blood flow will determine what the physical or mental disability may be. This may include impaired ability with movement, speech, thinking and memory, bowel and bladder function, eating, emotional control, and other vital body functions. Recovery from the specific ability affected depends on the size and location of the stroke. A minor stroke may result in only minor problems such as weakness in an arm or leg. More severe strokes may cause paralysis, loss of speech, or even death.

The symptoms of carotid artery disease may resemble other medical conditions or problems. Always consult your physician for a diagnosis.

How is carotid artery disease diagnosed?

In addition to a complete medical history and physical examination, diagnostic procedures for carotid artery disease may include any, or a combination, of the following:

• auscultation (listening to) of carotid arteries - placement of a stethoscope over the carotid artery to listen for a particular sound called a bruit (pronounced brew-ee). A bruit is an abnormal sound that is produced by blood passing through a narrowed artery. A bruit is generally considered a sign of an atherosclerotic artery; however, an artery may be diseased without producing this sound.

• carotid artery duplex scan - a type of vascular ultrasound study performed to assess the blood flow of the carotid arteries. A carotid artery duplex scan is a noninvasive (the skin is not pierced) procedure. A transducer sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer (like a microphone) is placed on the carotid arteries at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the blood vessels, where the waves echo off of the blood cells. The transducer picks up the reflected waves and sends them to an amplifier, which makes the ultrasonic sound waves audible. Absence or faintness of these sounds may indicate an obstruction to the blood flow.

• magnetic resonance imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies, and a computer to produce detailed images of organs and structures within the body.

• magnetic resonance angiography (MRA) - a noninvasive diagnostic procedure that uses a combination of magnetic resonance technology (MRI) and intravenous (IV) contrast dye to visualize blood vessels. Contrast dye causes blood vessels to appear opaque on the MRI image, allowing the physician to visualize the blood vessels being evaluated.

• computed tomography scan (Also called a CT or CAT scan.) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices), both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat, and organs. CT scans are more detailed than general x-rays.

• angiography - an invasive procedure used to assess the degree of blockage or narrowing of the carotid arteries by taking x-ray images while a contrast dye in injected. The contrast dye helps to visualize the shape and flow of blood through the arteries as x-ray images are made.

Treatment for carotid artery disease:

Specific treatment for carotid artery disease will be determined by your physician based on:

• your age, overall health, and medical history

• extent of the disease

• your signs and symptoms

• your tolerance of specific medications, procedures, or therapies

• expectations for the course of the disease

• your opinion or preference

Carotid artery disease (asymptomatic or symptomatic) in which the narrowing of the carotid artery is less than 50 percent is most often treated medically. Asymptomatic disease with less than 70 percent narrowing may also be treated medically, depending on the individual situation.

Medical treatment for carotid artery disease may include:

• modification of risk factors
  Risk factors that may be modified include smoking, elevated cholesterol levels, elevated blood glucose levels, lack of exercise, poor dietary habits, and elevated blood pressure.

• medications
  Medications that may be used to treat carotid artery disease include:

  • antiplatelet medications - medications used to decrease the ability of platelets in the blood to stick together and cause clots. Aspirin, clopidogrel (Plavix®), and dipyridamole (Persantine®) are examples of antiplatelet medications.

  • anticoagulants - also described as "blood thinners," these medications work differently than antiplatelet medications to decrease the ability of the blood to clot. An example of an anticoagulant is warfarin (Coumadin®).

    

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  • antihyperlipidemics - medications used to lower lipids (fats) in the blood, particularly cholesterol. Statins are a group of antihyperlipidemic medications, and include simvastatin (Zocor®), atorvastatin (Lipitor®), and pravastatin (Pravachol®), among others. Studies have shown that certain statins can decrease the thickness of the carotid artery wall and increase the size of the lumen (opening) of the artery.

  • antihypertensives - medications used to lower blood pressure. There are several different groups of medications which act in different ways to lower blood pressure.

In persons with narrowing of the carotid artery greater than 50 percent to 69 percent, a more aggressive treatment may be recommended, particularly in persons with symptoms. Surgical treatment decreases the risk for stroke after symptoms such as TIA or minor stroke, especially in persons with an occlusion (blockage) of more than 70 percent who are good candidates for surgery.

Surgical treatment of carotid artery disease includes:

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• carotid endarterectomy (CEA)
  Carotid endarterectomy is a procedure used to remove plaque and clots from the carotid arteries, located in the neck. Endarterectomy may help prevent a stroke from occurring, particularly in persons with a carotid artery narrowing of 80 percent or more.

• carotid artery angioplasty with stenting (CAS)
  Carotid angioplasty with stenting is a minimally invasive procedure in which a very small hollow tube, or catheter, is advanced from a blood vessel in the groin to the carotid arteries. Once the catheter is in place, a balloon may be inflated to open the artery and a stent is placed. A stent is a cylinder-like tube made of thin metal-mesh framework used to hold the artery open. Because there is a risk of stroke from bits of plaque breaking off during the procedure, an apparatus, called an embolic protection device, may be used. An embolic protection device is a filter (like a small basket) that is attached on a guidewire to catch any debris that may break off during the procedure. While this procedure is performed widely, the long-term effects are still being studied.