Carotid Artery Disease

Normal blood flow to the brain is supplied by the carotid arteries. Like other arteries in the vascular system, the carotid arteries can become diseased with cholesterol plaque, a process called atherosclerosis. Cholesterol deposits accumulate in the inner lining of the carotid artery and cause gradual narrowing of the artery channel. This process is progressive and occurs over a period of years.

As the carotid plaque becomes more severe, a clot may form at its surface, then break off and travel to the small arterioles of the brain, plugging them and blocking blood flow to a portion of the brain. This causes oxygen deprivation (also known as ischemia) to the brain cells, and may cause the sudden onset of neurological symptoms. Some of these symptoms include weakness or loss of strength of the arm or leg, or of the facial muscles, numbness, difficulty speaking, or loss of vision in a portion of the visual field. If the clot is rapidly dissolved by the body’s built-in clot removal system, the oxygen deficiency is transient, the symptoms remit, and no permanent damage occurs to the brain (thus, a CT scan or MRI will not show any abnormality). This is called transient ischemic attack (TIA). If the occlusion lasts more than a few hours, however, permanent damage occurs to a portion of the brain. This is a stroke, or cerebrovascular accident (CVA). A CVA causes changes in the brain tissue that can be detected by a CT scan or MRI.

Diagnosing Carotid Artery Disease

Carotid artery disease can be suspected during a physical exam, when a physician listens with a stethoscope over your carotid artery, on each side of the neck. When a blockage is present in the carotid artery, the turbulence caused by interference to the blood flow causes a sound (“bruit”) that can be heard with a stethoscope.

Carotid artery disease can be diagnosed by several kinds of tests. The principal test used for this purpose is the carotid artery ultrasound. This test is performed in a vascular ultrasound lab, is painless, and takes about 30 min. In this test, the carotid artery, and blood flow through the carotid, are examined with ultrasound imaging. A carotid ultrasound can provide a very precise assessment of the health of the carotid artery.

An imaging test that is sometimes valuable as a screening tool is an examination of the Intima-Media Thickness (IMT) of the carotid artery. When atherosclerosis develops, the earliest events are the appearance of microscopic deposits of cholesterol plaque in the inner lining of the carotid. This causes the inner lining (the intima) to begin to thicken. In this test, the carotid artery is examined with ultrasound, and the thickness of the intima layer is carefully measured. Thus, this test detects the atherosclerosis process in its early stages, before it is fully manifest as a significant blockage. This data can be helpful information to you, as you can detect atherosclerosis early and make changes to modify your future risk. The test costs about $250. Unfortunately, this test is not covered by Medicare and many insurance companies.

Another imaging modality is CT angiography or MR angiography, where the carotid artery is examined by CT or MRI scanning. This test uses IV iodine contrast (CT) or gadolinium contrast (MRI) to image the carotid artery. The test requires an IV line. Some patients with kidney problems may not be able to tolerate iodine or gadolinium contrast.

Lastly, direct imaging of the carotid arteries can be done with formal angiography. During an angiogram, a catheter is inserted in the groin and advanced into the carotid artery. IV iodine contrast is then injected under x-ray visualization, and the artery is imaged.

Treating Carotid Artery Disease

The treatment strategy for carotid artery disease is based on the severity of the blockage, and whether or not you have ever had any symptoms, such as TIA or stroke:

The more severe the blockage, the more likely you will need to have some kind of invasive therapy.

A blockage that has already caused some clinical event, such as a TIA or stroke, will need more aggressive treatment than one that has not caused symptoms.

Mild blockages <60% can be treated with medications. These include antiplatelet agents (such as aspirin, clopidogrel, prasugrel, dipyridamole) and cholesterol-lowering drugs (mainly in the statin family — lovastatin, simvastatin, pravastatin, atorvostatin, etc.).

More severe blockages >60% generally are treated with invasive therapy: carotid endarterectomy or carotid stenting. In carotid endarterectomy (CEA), typically done under general anesthesia, a vascular surgeon makes an incision in the neck, then opens the carotid artery and removes the plaque from the carotid artery, then closes the artery with suture. Typically, this requires a 2 or 3 day hospitalization.

A carotid stent procedure, though considered invasive, is less invasive than CEA. This procedure, similar to a carotid angiogram, is performed through a needle hole in the femoral artery at the groin. Typically, the carotid stent procedure is performed immediately following a carotid angiogram; i.e., in the same setting. A catheter is inserted through the groin and its tip is positioned at the origin of the carotid artery. A small filter basket is then inserted into the distal portion of the carotid artery, beyond the blockage, to “catch” any debris that may be generated during the procedure. A balloon is then positioned at the site of the blockage and briefly inflated to stretch open the blockage. A stent, made of nickel-titanium, is then placed at the blockage to keep the artery open. The procedure takes about 1-2 hours. A carotid stent procedure typically requires an overnight hospitalization.

The decision on medical therapy versus invasive therapy, and which specific type of invasive therapy, depends on unique characteristics. These include carotid anatomy, presence or absence of other conditions, such as cardiac, pulmonary, or renal disease. Every patient is different, and the best therapy for you is something that you and your doctor should tailor to your particular situation and needs. A detailed discussion with your doctor is central to this decision making process.