Diabetes and Lipid Clinic of Alaska

 

 


About Carotid Artery Disease

Carotid artery disease is a type of peripheral arterial disease in which there is “hardening of the arteries” (atherosclerosis) in the main arteries carrying oxygen–rich blood to the brain (the carotid arteries). During atherosclerosis, the inside of the artery is gradually narrowed with a build–up of fatty plaque. As this plaque becomes more severe, there is a chance pieces may break off and travel further downstream in the artery.

If the pieces of plaque become stuck in an artery and obstruct the flow of oxygen–rich blood, the person can suffer a stroke (an ischemic stroke). This is caused by a severe lack of oxygen–rich blood reaching the brain (cerebral ischemia). Ischemic strokes are the most common form of stroke in the United States.

Risk factors and causes

The risk factors for carotid artery disease are similar to those for coronary artery disease, or atherosclerosis of the main arteries carrying oxygen–rich blood to the heart (the coronary arteries). Therefore, people with one condition often have the other. Risk factors for both (as shown by a coronary risk profile) that can be modified include the following:

  • Smoking
  • Lack of regular exercise
  • Eating a high–fat, high–cholesterol diet
  • Obesity
  • Uncontrolled diabetes and high blood pressure (hypertension)
  • Uncontrolled stress and anger
  • High LDL (“bad”) cholesterol levels and low HDL (“good”) cholesterol levels.
  • Currently undergoing hormone replacement therapy (HRT) 

Risk factors that cannot be modified include the following:

  • Gender. Men and women face different risks. For example, men are more likely to have a stroke and survive the attack, whereas women are more likely to die from one.
  • Advanced age. Cardiovascular diseases, as well as peripheral arterial disease, tend to affect older people more than younger people.
  • Ethnicity. Members of certain groups, such as African–Americans, have a higher statistical risk for high blood pressure (hypertension), which, in turn, is a risk factor for both stroke and heart attack (see High Blood Pressure & African Americans).
  • A family history of carotid artery disease or coronary artery disease

Signs and symptoms of carotid artery disease

Carotid artery disease often has no symptoms, making it difficult to diagnose. However, people who have experienced a transient ischemic attack (TIA) frequently suffer from carotid artery disease. Often called “mini strokes,” TIAs are considered warning signs of a future stroke. They can occur when small pieces of plaque temporarily interrupt the flow of oxygen–rich blood to the brain. Symptoms of a TIA include:

  • Weakness, numbness or tingling on one side of the body
  • Confusion
  • Trouble speaking (e.g., slurred speech)
  • Difficulty understanding speech
  • Loss of balance or coordination
  • Severe headache

TIAs may also cause a variety of visual symptoms that include:

  • Partial loss of vision or complete blindness
  • Double vision
  • Abnormal eye movements
  • Blurred vision
  • A gray shading or fogging within the field of vision

Anyone who has experienced these symptoms is urged to see their physician immediately to determine whether they had a TIA and whether they have carotid artery disease. An estimated 20 to 25 percent of TIA patients will develop a stroke within the next two years, and research has shown that 11 percent of patients who have a TIA diagnosed in the emergency room will suffer a stroke in the next 90 days.

Diagnosis Methods for Carotid Artery Disease

Because carotid artery disease often has no symptoms, it can be a difficult disease to diagnose. Often, physicians may suspect carotid artery disease based on a constellation of risk factors that cause them to pursue a diagnosis. One leading risk factor is a family history of coronary artery disease or peripheral arterial disease. Thus, most physicians will begin the diagnosis by taking a complete medical history.

The physician will also ask questions about the patient’s smoking history and level of exercise, as well as other risk factors associated with carotid artery disease. Finally, the physician will ask if the patient has had any recent symptoms of a transient ischemic attack (TIA) or a full stroke.

Following the medical history, the physician will give the patient a complete physical examination. As part of this exam, the physician will listen to the patient’s carotid arteries through a stethoscope placed on the patient’s neck. Carotid artery disease will sometimes produce sounds called “bruits” (broo–EEZ), which is the French word for “noises.” However, different physicians interpret these sounds differently, and the sounds are not always present in patients with carotid artery disease. Therefore, a number of tests may be needed in order to make a diagnosis.

These tests include the following:

  • Carotid duplex imaging. Also known as a Doppler ultrasound of the carotid arteries, this noninvasive test uses high–frequency sound waves to create a moving image of the carotid arteries and to measure the speed at which blood is flowing through them. This test is highly accurate and should be the first diagnostic test for patients in whom the suspicion of carotid artery disease is high.

  • Magnetic resonance angiogram (MRA). A minimally invasive test for creating three–dimensional images of the carotid arteries, revealing blood flow and detecting damage in the vessel walls. The test takes less time, requires a shorter recovery period and poses fewer risks than a cerebral angiogram. Currently, the image provided by an MRA is not as clear as the image produced by the more invasive DSA. However, the clarity is improving through technological advances and the use of contrast agents delivered through a small intravenous catheter in the arm.

  • Computed tomography arteriography (CT-A). This is a relatively new technique that uses a CT scanner to generate pictures of the carotid arteries. This is nearly identical to a carotid angiogram except that the contrast medium is put into the veins instead of the arteries and therefore has a lower risk of complications. This has become the primary test in some locations and is very likely to have a much more prominent role in the future as a result of the high reliability and availability of CT scanners in the United States. For more information, see CAT scan.

  • Cerebral angiogram or digital subtraction angiogram (DSA). A catheter–based test in which a catheter is inserted through a blood vessel (usually the femoral artery in the groin) and up to the carotid arteries. There, a special dye (contrast medium) is inserted through the catheter and into the carotid arteries. Following the injection of this dye, very clear x-rays can be taken of the carotid arteries.

Advanced imaging techniques are also allowing physicians to better describe the characteristics of carotid plaque. For example, many researchers classify plaque as homogeneous or heterogeneous. Homogeneous plaque has a smooth surface and is basically the same texture throughout. Heterogeneous plaque has an irregular surface with areas of hemorrhage. Studies have found that heterogeneous plaque is the likely culprit among individuals who have had a stroke or TIA.

It is felt that therapy for carotid artery disease will eventually be influenced by such characteristics of carotid plaque, in addition to the degree of narrowing (stenosis) of the carotid artery.

Treatment and Prevention

Treatment for carotid artery disease depends on the severity of the blockage in the blood vessel. Over time, physicians have developed standards to help them choose between treatment with medication, surgery or a less–invasive procedure. In general, patients may be treated with medication and no surgical intervention if:

  • They are experiencing symptoms and have less than a 50 percent stenosis
  • They have no symptoms and have less than an 80 stenosis of the vessel
  • They are in a high–risk group for surgery or less–invasive therapies

For people in these categories, the first step in their treatment will likely begin with controlling risk factors. The controllable risk factors for carotid artery disease are similar to those for coronary artery disease, and the lifestyle changes are the same for both conditions. These include:

  • Quitting smoking. Smoking is a major cause of coronary artery disease and cardiac arrest. Heart disease is the leading smoking–related cause of death in the United States among men and women, according to the U.S. Centers for Disease Control and Prevention (CDC). The CDC also suggests that the average smoker dies nearly seven years before a nonsmoker.

  • Maintaining a regular program of exercise. The increased risk from not exercising has been compared to the risk from smoking a pack of cigarettes per day.

  • Reducing cholesterol levels. A key strategy for reducing cholesterol levels is to eat a heart-healthy diet that includes very few fats and oils. Saturated fats increase cholesterol levels. In addition to making diet changes, people are encouraged to exercise regularly. If these strategies do not reduce cholesterol levels, a physician may prescribe cholesterol-reducing drugs.

  • Controlling diabetes. Persons with diabetes may be more likely to develop heart–related diseases. Preventive care is crucial to the overall health and heart function of diabetic patients.

  • Controlling high blood pressure (hypertension). Individuals with high blood pressure are at greater risk of cardiovascular problems resulting from coronary artery disease. High blood pressure is also the most common risk factor for stroke. This is because a buildup of plaque in the arteries can lead to an even greater increase in blood pressure in the damaged areas of those arteries. Hypertension can be controlled through taking blood pressure medications antihypertensives, self–monitoring, eating a heart–healthy, low–salt diet and engaging in regular exercise. People are also encouraged to have regular check–ups with their physician.

  • Learning and practicing stress management techniques. Stress can lead to high–risk situations such as overeating, smoking, high blood pressure (hypertension) and a lack of exercise. In addition, chronic stress may be a direct contributor to poor heart health because it produces increases in blood pressure that could become permanent.

In addition to making lifestyle changes, medications may be prescribed to reduce the risk of stroke. These medications include a daily dose (usually 81 to 325 milligrams) of aspirin or other antiplatelet or anticoagulant drugs to help prevent the formation of blood clots.

Research has also shown that statins, which are used to lower cholesterol levels, can help prevent stroke. Although their mechanism of action is not completely understood, researchers believe that statins offer some protection through their ability to stabilize plaque deposits, reduce inflammation and slow the progression of carotid arterial disease. Individuals should always consult with their physician before taking any medication or supplement, even those available over–the–counter. Another class of drugs called ACE inhibitors has also been shown to reduce the risk of stroke and heart attack in high–risk patients.

If lifestyle changes and/or medication is not enough, the physician may recommend either surgery (carotid endarterectomy) or a less–invasive procedure such as angioplasty and stenting. The decision of which one to recommend depends on a variety of factors. During a carotid endarterectomy, the patient is usually put under general anesthesia while the neck is operated on. Blood flow is temporarily re–routed through a tube and around the blockage in the carotid artery. Obstructing plaque along the wall of the artery is then removed by removing the entire inner lining of the artery. The tube is removed, and the surgery is complete.

Although research consistently supports the surgery’s ability to reduce the risk of having a stroke, the surgery itself carries a risk of stroke and other possible complications. Patients are encouraged to learn everything they can about the surgery before proceeding with it.

Some patients may also be candidates for a less–invasive procedure known as carotid artery stenting. The U.S. Food and Drug Administration approved this procedure for use among certain patients in 2004. During this procedure, a catheter is inserted into a blood vessel (usually the femoral artery in the groin) and fed all the way up to the blocked carotid artery. A balloon at the tip of the catheter is then briefly inflated, which presses plaque back against the wall of the artery and makes more room for the blood to flow. Immediately after the balloon angioplasty, a wire mesh metal tube stent is inserted through the catheter and into the artery, where it expands to hold open the artery. A stent becomes a permanent part of the artery’s tissue in a matter of months.

Like endarterectomy, there is a risk that pieces of plaque will break off during the procedure itself and possibly cause a stroke. To prevent this, carotid artery stent systems are designed with special baskets that are temporarily deployed in the blood vessel during the procedure. These baskets are designed to catch any tiny particles of plaque that may break off during the procedure. Research has shown that carotid artery stenting has roughly the same rate of complications as endarterectomy, and may be safer than surgery in high risk patients.

The strategies for preventing carotid artery disease include the same lifestyle changes recommended in the treatment of the disease. For patients at high risk of developing the disease, physicians may perform carotid duplex imaging (Doppler ultrasound of the carotid arteries) as part of the patients’ regular examinations to screen for the disease.

For more information, please consult with the medical professionals at Diabetes and Lipid Clinic of Alaska.

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