Carotid Artery Disease

Anatomy

The carotid arteries are 2 of the 4 major vessels that carry blood to the brain. In the upper neck the main trunk (common carotid) branches into the external and internal carotid vessels. The external carotid artery carries blood to the neck and face while the internal carotid continues to the brain where it usually supplies blood to the frontal and parietal lobes. These areas of the brain control motor function (movement) and sensory function of the body as well as more complex aspects of cognition and personality. 

Narrowing of the carotid artery is a relatively common condition in older patients. This narrowing occurs due to the build-up of deposits inside the vessel usually at the branch point in the neck described above. The process leading to the deposits is called atherosclerosis. 

Risk factors for Atherosclerosis

The build-up of deposits (called plaque) occurs over years. The plaque is composed of varying amounts of fibrous tissue (scar), cholesterol, and calcium. Plaques may be soft or hard. Hard plaques are mostly calcium and scar tissue, whereas soft plaques contain more of the cholesterol material which has a consistency of toothpaste. Soft plaques are thought to be more serious than hard ones for reasons described below. Usually the make up of the plaque can be determined to some degree with ultrasound.


The carotid plaque usually develops at the branch point of the carotid arteries


 

Why is Carotid Plaque Important?

More severe forms of blockage usually occur in patients with one or more of the risk factors noted above. Most patients who have a severe form of blockage do not have any symptoms. The problem can be detected by listening over the neck with a stethoscope, as the physician might hear a "whishing" noise that indicates turbulence as blood passes through a narrowed channel. Such noises can also be caused by heart murmers or valve abnormalities. All patients over the age of 50 should have their necks auscultated (listened to) for this problem. Should the noise be heard, it is then appropriate to refer the patient for an ultrasound test to determine the presence and severity of blockage. 

Other patients with carotid blockage can have problems. Such patients are referred to as "symptomatic" and may have had a stroke or "TIA" (for transient ischemic attack). A TIA is a temporary impairment of function that usually lasts only minutes whereas a stroke causes more permanent brain damage.

Symptoms of TIA or Stroke (relevant to carotid plaque)

Other symptoms patients complain of like dizzyness, "floaters" in the eyes, headache, limb pain, and blurred vision are not usually related to carotid disease.

Testing for Carotid Stenosis

Ultrasound is the best test for examining the carotid arteries in the neck. We can accurately determine the degree of blockage and can usually make some observations about plaque morphology (hard vs. soft). We usually classify the blockage into 5 categories: normal, mild (< 50% narrowing), moderate (50-79%), severe (80-99%), and occluded (100%). Rarely in my practice is an arteriogram necessary for further investigation. Situations warranting an arteriogram (an invasive test) include evidence that the blockage extends high up in the neck or if the artery is not well visualized with ultrasound. Magnetic resonance angiography (MRA) is another commonly performed test. Its advantages are noninvasive technique and excellent imaging capabilities of the brain and arteries around the brain. A CT scan (or better-MRA) may also be performed in patients who have had a stroke or TIA's in order to see the extent of damaged brain.

Risk of Stroke with Carotid Atherosclerosis

The presence of more severe blockage in the carotid artery carries an increased risk of stroke. This risk is different for patients who are symptomatic (i.e. TIA or stroke) compared to those who are not. Symptomatic patients with a carotid blockage greater than about 60% have a 15% risk per year of stroke. We consider this risk substantial and usually recommend surgery without much delay. For patients who are asymptomatic, surgery is discussed when they are in the 80-99% category. The yearly risk of stroke is about 4-5% in these patients. Also, patients with extensive, soft plaque (see above) are at higher risk for developing stroke or symptoms.

Surgery for Carotid Atherosclerosis

The operation for treating carotid blockage is called carotid endarterectomy. This is one of the most common procedures performed by vascular surgeons. The operation starts with an incision along the front side of the neck. The carotid artery is clamped above and below and is opened length-wise. The plaque is removed by separating it from the inner layer of the blood vessel wall. The surgeon takes extra time to be sure the resulting surface is smooth and free of loose debris. The artery is stitched back up using a strip of fabric as a "patch". This patch makes the operation easier and reduces the risk of narrowing in the future caused by scar tissue formation. Sometimes a "shunt" is used, which is a plastic tube that allows blood to flow through the vessel while we are operating on it. The operation can be done using general anesthesia (totally asleep- my preference) or using local anesthesia (Novacaine injected to numb up the neck).


The plaque is separated from the vessel wall. A shunt is in place allowing blood flow to continue up the carotid artery


Risks of Surgery

No surgery is without risk. As surgeons we decide whether an operation is appropriate if the risks are outweighed by the benefits. For carotid disease, the benefit of surgery is reducing the risk of stroke. This benefit is more for patients with symptomatic disease, though patients with asymptomatic disease also benefit. The major risks of carotid endarterectomy are listed below.

The operation can cause stroke. Assuming you are a well-trained, competent vascular surgeon this risk should be less than 3%. The risk is a little higher for patients with stroke or TIA than those who are asymptomatic. Certain cranial nerves are near the site of surgery and are susceptible to injury, though permanent disabling injury is rare. Occasionally (less than 10%) patients may experience a hoarse voice, weakness of the tongue, weakness of the lip, and rarely swallowing difficulties. Bleeding requiring reoperation occurs about 5% of the time. One of the other major complications is heart attack. There is an association between carotid artery disease and heart disease, since atherosclerosis can affect arteries in the heart as well. Frequently my patients are tested for heart disease prior to surgery and special treatment is provided to help minimize this risk.

At New England Medical Center, my partner and I perform nearly 100 carotid endarterectomies per year with a stroke rate of 1%. Many of these operations are performed on high risk patients with severe heart disease or history of stroke.

What to Ask Your Surgeon

If you have been told you need surgery for carotid blockage, your surgeon should communicate the following information to you.

I believe it is critical to have an anesthesiologist experienced in caring for patients with heart disease. This will help provide for the best surgical outcome.

Recovery After Surgery

Patients recover quickly after uncomplicated carotid endarterectomy. The hospital stay for my patients is 1 day for over 90%. All patients discharged are ready, and look forward to, returning home. They have minimal pain and usually don't need to take narcotic pain pills. Within 5 to 7 days most patients have resumed near-normal activities. The incision heals quickly and the scar is not prominent. Major complaints are scratchy throat, mild soft swelling, and numbness of the ear lobe. These are minor and fade quickly.

Summary

This synopsis of carotid disease should provide a basic understanding of the disease process and its treatment. It is not meant to be comprehensive. Remember, there is no substitute for open communication between the patient and surgeon so you must ask questions.

Copyright 2000. James M. Estes, MD. All rights reserved.