Carotid artery stenosis occurs when the carotid arteries become narrower, reducing blood flow to the brain and increasing the risk of stroke. It can be caused by cholesterol and fat plaque buildup or high levels of platelets in the blood. Early diagnosis and treatment can prevent strokes, and treatment options include reducing risk factors, taking blood thinners, and surgery. Prevention through exercise, diet, and not smoking is also important.
The carotid arteries, located in the neck, are the main source of oxygen-rich blood flow to the brain. Carotid artery stenosis (CAS) occurs when these arteries become thicker and narrower, thereby cutting off some of this necessary blood supply. While mild carotid artery stenosis occurs in most people as they age, the greater the blockage, the higher the chance those affected have a stroke or transient ischemic attack (mini-stroke).
Carotid artery stenosis can be the result of one or more factors. Cholesterol and fat plaque can build up in the artery, creating a narrower path for blood flow. High levels of platelets in the blood can also form clots in the arteries, blocking the path.
When a stroke is caused by artery stenosis, usually the artery has narrowed and platelets have built up in the narrow spot to form a clot. When blood pools behind the clot, the clot may eventually have passed into the brain. In addition, the clot prevents blood from reaching the brain and the interruption of flow, even if temporary, kills brain cells and can impair brain function.
Of the 600,000 strokes that occur each year in the United States alone, one-quarter to one-half are estimated to be caused by carotid artery stenosis. Thus, early diagnosis and treatment could help prevent 150,000-300,000 strokes each year in the United States. Detection and treatment of CAS depend on the symptoms and the degree of narrowing of the carotid arteries.
In some cases, during your annual medical exam, your doctor will hear a sound called a murmur when using a stethoscope. If a murmur is noted, the patient will likely undergo a Doppler ultrasound of the carotid artery to confirm the stenosis. When carotid artery stenosis is found, further tests are done to assess the degree of stenosis.
Angiograms or catheterizations use contrast medium to outline and measure the stricture. Magnetic resonance imaging (MRI) and computed tomography (CT) may also be used. For pacemaker patients, MRI is contraindicated because it can disrupt pacemaker signals, and angiograms carry some risk of stroke. A noninvasive test, oculoplethysmography, evaluates blood pressure in each eye and can show whether significant blood flow to the eye is affected by carotid artery stenosis.
Unfortunately, the first symptom of carotid artery stenosis can be impaired brain function, a mini-stroke, or a complete stroke. Yearly physical exams can help with early diagnosis and are therefore recommended. Patients with a significant family history of CAS or stroke should inform their doctors. Smokers and the obese have a higher risk of CAS and should be monitored. Those with high cholesterol are also at risk.
If CAS is present but blocks less than 50% of the artery, treatment includes reducing risk factors for further strictures, such as smoking cessation, low-fat diets, and prescribed exercise. These are usually combined with taking a blood thinner such as aspirin. The dose is very low, essentially one “baby” aspirin (81 mg) per day.
Other blood thinners, such as warfarin, may also be prescribed. Risk factors with warfarin can include excessive bleeding and bruising. Those taking warfarin are monitored closely through blood tests and have some dietary restrictions.
When carotid artery stenosis is greater than 50%, several strategies can be employed to treat it. Carotid endarterectomy is a surgical procedure in which the surgeon opens up the artery and removes plaque buildup and blockages. Without complications, most people who undergo this surgery will be discharged from the hospital within a few days. The effects of endarterectomy last up to 20 years and significantly reduce risk factors for stroke.
In some cases, when the risk of a general anesthesia is too high, cardiologists perform a carotid angioplasty. This involves inserting a catheter, usually through an artery in the thigh, and threading it into the narrowed section of the carotid artery. Once there, a balloon attached to the catheter is inflated to open up the artery.
After the balloon is inflated, a hollow metal tube called a stent is placed to keep the artery open. The advantage of this method is that it is not performed under general anesthesia; patients are usually conscious during the procedure and go home a few hours later. However, this is a relatively new procedure and no long-term results are available.
Because carotid artery stenosis can cause serious health risks, it’s wise to have a plan to prevent it rather than cure it. Exercise, sensible diet, and not smoking are all ways to reduce plaque buildup in your arteries. Yearly checkups can also help catch stricture in its early stages, so attention can be focused on simple enough changes in behavior to avoid progression.
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