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Carotid artery disease (ka-ROT-id) occurs when one of the major blood vessels, which supplies blood from the heart to the brain, becomes blocked or narrowed. Carotid artery disease is caused by atherosclerosis ("hardening of the arteries") which is a build-up of plaque (plak) similar to that which forms on the teeth. As we age, the normally smooth inner walls of the arteries develop a build up of plaque; and eventually, the blood flow through the artery is impaired.
There are two common carotid arteries, one on each side of the neck-that divide into internal and external carotid arteries. The internal carotid arteries supply oxygen-rich blood to the brain. The external carotid arteries supply oxygen-rich blood to the face, scalp, and neck.
Carotid artery disease can be very serious because it can cause a stroke, or "brain attack." A stroke occurs when blood flow to your brain is cut off. If blood flow is cut off for more than a few minutes, the cells in your brain start to die. This impairs the parts of the body that the brain cells control. A stroke can cause lasting brain damage, long-term disability, paralysis (an inability to move), or death.
If the plaque within the artery is soft, rather than hard, it may develop a crack or an irregular area. At the site of the damaged plaque, platelets will tend to stick in an effort to repair the area. Platelets are "sticky" cells which aid in the clotting of blood. As more and more platelets stick to the plaque and each other, a clot (thrombus) forms which slows or blocks the flow of blood to the brain and may cause a stroke. Alternatively, a piece of plaque or clot can dislodge from the carotid artery and travel in the blood stream. A problem does not occur until the piece of plaque or clot is no longer able to fit within the blood vessel as the vessels become smaller within the brain. The plaque or clot then becomes stuck or lodged within the blood vessel, limiting the amount of blood flow past this area, which then leads to a stroke from a lack of blood supply to the brain tissue.
Figure A shows the location of the right carotid artery in the head and neck. Figure B is a cross-section of a normal carotid artery that has normal blood flow. Figure C show a carotid artery that has plaque buildup and reduced blood flow.
Stroke is the 3rd leading cause of death in adults in the United States. Strokes can be categorized as three types: ischemic, embolic and hemorrhagic. Ischemic and embolic strokes comprise approximately 85% of all strokes, with two-thirds of those strokes being ischemic in nature and one-third are embolic.
An ischemic stroke refers to the process when atherosclerosis causes a clot (thrombus) to form, which eventually blocks blood flow to part of the brain.
An embolic stroke occurs when a clot breaks off and travels in the blood stream until it becomes lodged in a small vessel in the brain, thereby blocking blood flow.
A hemorrhagic stroke, which accounts for approximately 15% of
all strokes, is the least common type of stroke and occurs when
there is bleeding in the brain. A blood vessel on the brain's
surface may rupture or tear, allowing blood to escape into the
space between the brain and skull, which is known as the
subarachnoid space. This subtype of stroke (or bleed) is called a
Lastly, a blood vessel within the brain can burst if there is a weakening in the vessel wall, which then causes bleeding into the surrounding brain tissue. This subtype of hemorraghic stroke is known as a cerebral hemorrhage.
Carotid artery disease is often asymptomatic until the blockage(s) become significant and the patient is at considerable risk for a stroke or suffers an actual stroke. Risk factors for atherosclerosis and thus, carotid artery disease, include:
- Smoking cigarettes
- High cholesterol
- High blood pressure
Symptoms of both a stroke and transient ischemic attack (TIA) include:
- Weakness or paralysis of a limb or one side of the body
- Inability to speak or articulate clearly
- Blindness or other visual changes in one or both eyes
- Difficulty swallowing
Along with carotid artery disease, there are a number of less common conditions that also can affect the carotid arteries, including:
- Aneurysms, or swelling of the artery
- Carotid body tumors, which are tumors that arise from and involve the carotid arteries
- Recurrent blockages after prior carotid artery surgery
- Fibromuscular dysplasia, an inflammatory condition of the artery
- Inominate artery disease, or blockages in an artery below the carotid artery
- Carotid artery dissections, where the wall of the artery splits or tears
A careful history will be obtained by the vascular surgeon, which includes questions regarding one's medical history, prior surgeries, medications and risk factors for carotid artery disease. Additionally, questions will be asked related to any symptoms of a stroke or transient ischemic attack, when they occur and how often.
During the physical examination, the vascular surgeon will feel the carotid pulses in the neck, in addition to pulses throughout the body. A stethoscope will be used to listen over the carotid arteries for any turbulent blood flow, which is called a carotid bruit. Carotid bruits are indicative of carotid artery disease and warrant further investigation. Other indications of one's cardiovascular health and risk factors for carotid artery disease will be assessed during the physical examination, including the heart, lungs and neurologic status.
Fortunately, carotid artery blockages can be diagnosed easily with ultrasound imaging, a painless and safe procedure that is performed on an outpatient basis. A carotid duplex ultrasound involves the use of high-frequency sound waves to create images of the carotid arteries, as well as a doppler study to determine how fast the blood is flowing within the arteries.
A carotid artery blockage or narrowing is diagnosed by ultrasound when the speed (velocity) of blood flowing through the artery is in excess of the standard normal value. Similar to a "pinched" area in a garden hose which increases the water pressure passing through the hose, blood must travel much faster in the area of carotid artery that is narrowed due to plaque or a clot. The vascular surgeon is able to monitor the severity of the carotid artery disease over time by comparing the results of carotid duplex ultrasounds performed at intervals of 6 or 12 months usually.
Additionally, the vascular surgeon may order a CT or MR angiogram to enable better visualization of the carotid artery blockage. Both diagnostic tests require the intravenous injection of contrast; and therefore, these tests are not usually ordered unless the carotid artery disease has progressed to the point when surgery is being considered. A CT (computerized tomography) scan requires exposure to radiation similar to that which is given during an x-ray. Whereas, an MRI (magnetic resonance imaging) scan requires the use of a large magnet that moves the hydrogen ions within cells and creates an image of the body structure being scanned.
First and foremost, if someone is having symptoms of a stroke or a transient ischemic attack, they should contact their doctor or UCSF Medical Center immediately.
A number of large studies completed during the 1990s clearly demonstrated that surgery was the best treatment for reducing the risk of stroke in patients with severe blockages in the carotid arteries. At UCSF Medical Center, our vascular surgeons have over five decades of experience preventing strokes with carotid artery surgery.
Carotid artery surgery (carotid endarterectomy) involves:
- Opening the artery
- Removing the plaque that is causing the narrowing
- Closing the artery, usually with a synthetic patch
During the surgery, a temporary bypass is often used to allow blood to flow around the area of surgery as it travels to the brain.
Mild to moderate blockages are treated with antiplatelet agents, such as aspirin. In addition, treatment involves identifying and reducing risk factors, such as cigarette smoking and high blood pressure. Ultrasound studies are repeated over time to monitor the blockage and determine if it has progressed to a severe blockage that requires surgery.
Not all patients are able to undergo surgery because of their overall medical condition or other specific factors. There are a number of new non-surgical options available to treat blockages in the carotid arteries, including balloon angioplasty and stents. Both of these procedures use a catheter-guided balloon, inflated in the blocked area, to open up the carotid artery. A metal stent may be inserted to help keep the artery expanded.
At this time, the risks of stroke during these procedures and the long-term results of these procedures are still under investigation. Therefore, carotid artery angioplasty and stenting are currently recommended only for patients who are not candidates for conventional surgical treatment.
Vascular surgeons at UCSF have over five decades of proven experience in preventing strokes with carotid artery surgery. Recently, our vascular surgeons were given the highest designation for quality outcomes in carotid surgery by the Leapfrog Initiative that compared outcomes in carotid surgery throughout Northern California. In addition to stroke, our surgeons have extensive experience with other forms of vascular disease, including many rare and uncommon disorders, which involve the carotid arteries.