Most people know about coronary artery disease, in which plaque blood flow and increasing heart attack risk. But plaque can also build up in the carotid arteries—the large arteries on both sides of the neck that carry blood to the front and middle part of the brain. This carotid afiery disease significantly increases stroke risk if not treated.
Carotid artery disease has the same causes as coronary artery disease—blood cholesterol adheres to the walls of the artery over time, forming plaque deposits. These deposits can cause a stroke if a piece of plaque breaks off and gets lodged in a smaller brain artery, blocking blood flow...or the plaque cracks or becomes roughened, triggering a blood clot that blocks blood flow to the brain...or the carotid afiery becomes so narrowed by plaque that the blockage itself prevents sufficient blood from getting to the brain.
WHO IS AT RISK?
Risk factors for carotid artery disease include smoking, high cholesterol, high blood pressure, diabetes, obesity, physical inactivity, previously diagnosed coronary artery disease and a family history of coronary or carotid artery disease. Age is also a risk factor. Only one out of every 200 people between age 50 and 59 has significantly narrowed carotid arteries, but this rate climbs exponentially in each decade after 65. Of those aged 60 to 79, one out of 100 people has blockage. Among those aged 80 to 89, one out of 10 has significant carotid artery blockage of 50% or greater.
EARLY WARNING SIGN
Most people with early-stage carotid artery disease don't realize it.
Reason: Arteries with blockages of 60% or less usually produce no symptoms. For many, the first sign that they have carotid artery disease is a transient ischemic attack (TIA). TIAs may occur when a small piece of plaque breaks off or a small plaque-related blood clot forms, temporarily reducing blood flow to the brain. These attacks typically last only a few minutes and cause no permanent damage.
Symptoms include loss of sight in one or both eyes...weakness, numbness or tingling on one side of the body...loss of coordination...dizziness or confusion...slurred speech...difficulty swallowing.
If you experience any of these TIA symptoms, seek medical attention immediately. Someone who has had a TIA is 10 times more likely to have a stroke than someone who hasn't. Even if you haven't experienced symptoms, you should be examined for possible carotid artery blockage if you have any of the above risk factors—particularly if you're older than age 45.
- Stethoscope exam. The first step in this examination, which your internist can perform, is to listen with a stethoscope to the flow of blood through each carotid artery. If the doctor hears a bruit—a rushing sound that indicates turbulent blood flow through the artery—then it's possible that you have carotid artery blockage. The absence of bruit does not rule out carotid artery blockage, however.
- Carotid duplex ultrasound. If your doctor suspects carotid artery blockage because you have heart disease, high cholesterol, high blood pressure and/or diabetes, the next step is a carotid ultrasound exam. In this test, an ultrasound image of the blood flow through the carotid artery is examined to determine whether there are blockages or other structural abnormalities. The exam is noninvasive and painless.
- Catheter angiography and CT/MRI angiography. If an ultrasound indicates carotid artery blockage, one of several follow-up tests is typically done to get a still-better picture of the blockage . ln a catheter angiogram, a special dye is injected into the blood vessels of the head and neck through a catheter, and the carotid arteries are then X-rayed. ln a CT angiogram or an MRI angiogram, the carotid arteries are imaged using a CT or MRI scan. In all three tests, both carotid arteries are typically scanned, 294 along with the two vertebral arteries in the back of the head that supply the rear brain.
Reason: 20 percent of people with carotid artery disease also have blockages in the vertebral arteries. While these tests are more invasive than ultrasound and therefore carry some risk, they give a more in-depth picture of the blockage.
Note: Catheter angiogram is considered the gold standard for accuracy and gives the clearest picture—it also has the most risk.
If the carotid artery disease is asymptomatic—which is usually the case when the artery blockage is 60% or less—the first line of treatment involves controlling the underlying risk factors, including…
- Bringing LDL cholesterol down through a low-fat diet and cholesterol-lowering medications.
- Controlling high blood pressure with a low-sodium diet and antihypertensive medications.
- Keeping blood sugar under tight control, if you have diabetes.
- Quitting smoking.
- Losing weight, if you are overweight.
- Getting 30 minutes or more of daily physical activity such as walking, cycling and swimming.
Also, one or more antiplatelet medications may be prescribed to reduce the risk of dangerous blood clots—including aspirin, dipyridamole (Persantine), clopidogrel (Plavix) and ticlopidine.
Surgery to reduce asymptomatic carotid artery blockage is usually only recommended if the blockage exceeds 70%.
Reason: Studies have shown that for lesser blockages, risks of surgical complications (reaction to anesthesia or mid-operation stroke or heart attack) outweigh stroke prevention benefits. The main causes of mid-operation stroke or heart attack are emboli (air bubbles or particles of plaque or blood clot in the blood). The risk of serious complications is 2.3%.
The most common operation is a carotid endarterectomy, in which an incision is made in the neck at the point of the blockage—the plaque and, if necessary the diseased artery walls are surgically removed. A shunt (tube) is used to route blood around the area being worked on. If artery tissue is removed, a length of artery is taken from the leg and grafted onto the carotid artery (similar to what's done in coronary bypass surgery). It usually involves a hospital stay of two to four days. After carotid surgery for patients with asymptomatic blockage of greater than 70%, there is a 40% reduction in risk of stroke over five years. However, other risk factors must still be treated since atherosclerosis and narrowing can return.