Carotid Artery Disease:Effective Treatment Can Reduce the Risk of Stroke

A stroke can be devastating. Strokes are often fatal, and over half of those who do survive will have some permanent disability that makes it impossible to continue to work or have a normal life. Stroke is the third leading cause of death in this country, and it is the leading cause of permanent disability among older Americans. Over 100,000 strokes occur each year in the United States and more than 50 billion dollars is spent annually on the care of stroke victims. Almost everyone knows someone—a friend, relative, or parent—who has had a stroke, but few people understand how strokes happen and how they can be prevented. Since 75% of people who suffer a stroke never have any warning signs, it is critical for the general public to know about stroke prevention.

Some strokes—called "hemorrhagic strokes"—are due to bleeding in the brain, but 80% of strokes are due instead to blockages in the blood vessels that supply circulation to the brain. When circulation is blocked, the brain cells do not get enough oxygen and they begin to die. Like the blockages in the blood vessels to the heart that cause a heart attack, those blockages in the blood vessels to the brain can cause a stroke, which is also called a "brain attack." This can leave people with paralysis of their arms or legs, an inability to speak clearly, or blindness.

These blockages in the circulation of blood to the brain may be caused by blood clots that flow out of the heart, but most blockages are caused by plaques due to atherosclerosis ("hardening of the arteries") that occur in the carotid arteries which supply the major circulation to the brain. This is called carotid artery disease. Over time, these build-ups of fat and cholesterol progressively block the carotid arteries in the neck, like rust in an old pipe. When the blockage becomes severe, people are at high risk for having a stroke. With blockages of more than 70%, there is a 5-10% risk of having a stroke every year! Fortunately, when these blockages are detected early, effective treatment can prevent a stroke.

A doctor may find signs of carotid artery disease on a routine physical examination, but most plaque build-up cannot be detected without further testing. Fortunately, a simple ultrasound examination can easily detect carotid artery disease in just a few minutes without any risk or discomfort. People at high risk for cardiovascular disease —older people who are smokers or have high blood pressure, diabetes, high blood cholesterol, or a family history—may benefit from a carotid artery ultrasound exam, even if they don't have any symptoms.

When carotid artery disease is detected, effective treatment can reduce the risk of stroke. When plaque build-up is mild (less than 50% blockage), then the best "cure" is an ounce of prevention—to reduce any risk factors that may make the plaque buildup worsen in the future. Smokers need to stop smoking. Blood pressure and diabetes can be controlled, and blood cholesterol can be lowered either by diet alone or with medications. Most doctors also recommend a mild blood thinner such as one aspirin a day. These medical treatments are good advice for all people with carotid artery disease, but those with more severe blockages may require more aggressive treatment.

Patients with severe blockages due to carotid artery disease—greater than 70%—are usually considered for surgery. This is particularly true in patients with symptoms called "TIAs," or so-called "mini-strokes." During surgery, the plaque is removed from the lining of the artery and the artery is restored to normal. This procedure is called a carotid endarterectomy, or "CEA". CEA is a major operation, one that carries some risks to the patient, but it is not as invasive as heart bypass surgery. In many cases, CEA can even be done with a local anesthetic. When everything goes as planned, most people can go home the morning after surgery. Recovery from surgery is usually rapid and most people can resume fairly normal levels of activity within several days.

Any major surgery like CEA can have complications such as bleeding or infection, but the real risks are heart attack and stroke. People with severe carotid artery disease who are being considered for surgery are three or four times more likely to have heart disease than other people, so the risk of heart problems after surgery is a real concern. For this reason, patients who need CEA must have a cardiac stress test before surgery to make sure that their risk of heart attack is low. An ironic and challenging problem for specialists who treat carotid artery disease is that the most dreaded complication of CEA is the exact problem they are seeking to prevent. A stroke can happen with surgery! Overall, careful studies of people having CEAs throughout the United States and the rest of the world have repeatedly shown that CEA is better at reducing the risk of stroke than any medical therapy. People with severe carotid artery disease who received only medical treatments have a 10-25% risk of stroke compared to those treated with CEA, who have a 1-3% risk. When CEA can be performed safely in people with severe carotid artery disease, it is currently the best method for stroke prevention.

Like the treatments for heart disease, modern, less invasive treatments for carotid artery disease have recently been developed. Carotid artery stenting (CAS) can open severe blockages in the carotid arteries without surgery. When CAS is performed, a small catheter is passed up from an artery in the groin, through the vessels into the blocked carotid artery. An expandable metal stent is placed in the blockage to open it up. Once it is expanded, the metal stent keeps the walls of the artery open, similar to the foundation walls of a tunnel. CAS is a relatively new procedure when compared to CEA, which has been performed for over 50 years. Initial studies have shown good results, but much more

experience will be required to determine whether CAS should replace surgery in most cases. Right now, CAS seems to be most beneficial in patients who are at very high risk for any surgery; this includes those with an occlusion of the opposite carotid artery and those who have developed recurrent blockages in the carotid artery even after successful CEA.

In our aging population, the devastating personal disabilities and the medical-care costs produced by stroke will continue to rise unless we can achieve improved methods for stroke prevention. Currently in the United States, carotid artery disease accounts for up to one-half of all strokes. When severe carotid artery disease is diagnosed before a stroke happens, that stroke can most often be prevented by the modern combination of medical, surgical, and minimally invasive treatments.

About the Author: William R. Flinn, MD is Professor of Surgery and Head of Vascular Surgery for the University of Maryland. He is a former member of VDF's Board of Directors.