For release: Tuesday, February 26, 1991
Overwhelming evidence from an ongoing clinical trial shows that the surgical removal of fatty deposits from the the main artery in the neck supplying blood to the brain is highly effective in reducing strokes for patients who have a severely narrowed carotid artery and have previously had a stroke or symptoms of a stroke.
Confirmation of the effectiveness of the surgery to remove the deposits was reached after analyzing data collected on the first 595 patients with severe carotid narrowing and a previous mild stroke or warning signs of a stroke. About 50 percent of the patients in the study were randomly chosen to undergo surgery. The procedure, called a carotid endarterectomy, was performed at 50 medical centers in the United States and Canada by vascular surgeons or neurosurgeons who had previously demonstrated expertise in the procedure. The randomized clinical trial, called the North American Symptomatic Carotid Endarterectomy Trial, was coordinated by Dr. Henry J. M. Barnett of the University of Western Ontario and sponsored by the National Institute of Neurological Disorders and Stroke (NINDS). In 1987, surgeons performed about 81,000 carotid endarterectomy operations just in the United States; and the operation is performed frequently in Canada and throughout Europe. There are wide variations, however, in the frequency of its use both from country to country and from region to region within countries.
The interim data analysis clearly revealed that, for patients in the study with 70 to 99 percent narrowing of the neck's carotid artery, surgery reduced the chances of having a stroke from greater than 1 in 4 to less than 1 in 10. These results prompted the study investigators to halt the portion of the trial that included medical treatment alone, without surgery, for patients with severe narrowing. The trial will continue in order to determine possible benefits for patients who have symptoms and moderate narrowing of 30 percent to 70 percent. The NINDS is sponsoring a separate trial for patients who have fatty deposits in the carotid but are without symptoms.
Stroke occurs when brain cells die because of decreased blood flow to the brain. A blockage of a blood vessel in the brain or neck is the most frequent cause of stroke and is responsible for about 75 percent of the approximately 145,000 U.S. stroke deaths in the last year.
To be eligible for the trial, patients had to be under 80 years old and had to have experienced a mild stroke or stroke's warning signs within the previous 120 days. Warning signs for stroke include tingling or weakness in a limb or on one side of the face, loss of strength in a limb, difficulty with speech, or temporary blindness in one or both eyes. When these signs or symptoms resolve within 24 hours or less, they are called a transient ischemic attack (TIA). Patients in the study also underwent a diagnostic X-ray procedure called angiography in which a fluid is injected into the artery to provide an accurate measurement of the degree of carotid artery narrowing.
Because those who received the operation had a 78 percent relative reduction in their risk of suffering a major or fatal stroke on the side of the operation, the patients who had been receiving medical treatment alone were rapidly offered the opportunity for carotid endarterectomy.
All patients in the study received optimal medical care that included treatment to thin the blood, usually aspirin, and, when indicated, treatment for high blood pressure, high cholesterol, and diabetes. About two-thirds of the patients had a history of smoking. Smoking cessation advice was provided for the approximately one-third who were current smokers. Patients were counseled about diet as well. The median age of the patients was 66, and one-third were women.
Although the 5-year trial which began in 1987 will continue, investigators believe it is in the best interests of the patients with severe narrowing to halt the non-surgical portion of the study. By 18 months over 24 percent of the medical patients, but only 7 percent of the surgical patients, had experienced a fatal or non-fatal stroke on the same side as the narrowed artery. A stringent analysis of the data revealed that greater than 12 percent of the medical patients, but only 5 percent of the surgical patients, had experienced a major or fatal stroke or died from any cause within 18 months of the surgery.
This study does not resolve uncertainty about the efficacy of the operation for those with 30 to 69 percent narrowing. However, it confirms that carotid endarterectomy is highly beneficial for patients with recent TIAs or a mild stroke who have severe narrowing of the carotid artery.
Stroke is the Nation's third leading killer and the major cause of disability among adults. It affects about 500,000 Americans each year. More than 2 million stroke survivors endure crippling disabilities, including paralysis, loss of speech, and lapses of memory. Stroke costs the Nation more than $25 billion a year.
Note: Results of the study have been published in the journal Stroke, Vol. 22, No. 6, (June 1991), pp. 711-720, and in the New England Journal of Medicine, Vol. 325, No. 7, (Aug. 15, 1991), pp. 445-453.
Last Modified August 7, 2009