Life-Saving Treatments to Prevent Stroke Underused

Press Release Date: September 7, 1995

The Agency for Health Care Policy and Research (AHCPR) is taking the unprecedented step of announcing findings of an important study prior to the full study's completion on the best methods of preventing stroke in people who are at high risk. The study found that two commonly known and effective interventions—warfarin to thin the blood and carotid endarterectomy to unclog the carotid arteries—are not being used appropriately to prevent strokes.

Researchers supported by AHCPR found that expanded use of the anticoagulant, warfarin, could cut in half the 80,000 strokes each year due to atrial fibrillation, a condition in which the heart beats rapidly and erratically. Atrial fibrillation makes people more prone to blood clots that can lodge in the arteries leading to the brain and cause a stroke. Warfarin thins the blood and keeps dangerous clots from forming. The investigators estimate that proper anticoagulation therapy could save approximately $600 million annually.

The study also found that use of the surgery to remove the fatty plaque from carotid arteries needs to be better targeted. While it is beneficial for people with stroke symptoms and a high degree of blockage, researchers found that screening large numbers of asymptomatic patients is not warranted.

"This research bridges the gap between biomedical science and practice," according to Clifton R. Gaus, Sc.D., administrator of AHCPR. "The National Institutes of Health and other biomedical researchers study causes and cures of diseases, but it is AHCPR's job to study whether advances in medical science are being translated into better patient care in the real world."

David B. Matchar, M.D., principal investigator of AHCPR's Secondary & Tertiary Prevention of Stroke Patient Outcomes Research Team (PORT) at Duke University, said warfarin therapy is widely underutilized in spite of clinical trials showing that it is the optimal treatment for the majority of persons age 60 and older who have atrial fibrillation.

Currently, just one-quarter of atrial fibrillation patients undergo warfarin therapy, and only half of these receive the optimal dosage. The researchers estimate that 50 to 75 percent of all patients over 60 years of age with atrial fibrillation should be given anticoagulation therapy. Anticoagulation therapy is unnecessary for most persons under age 60 with atrial fibrillation because they have a much lower risk of stroke.

"Stroke is now as preventable as heart attack. Primary prevention—reducing risk by giving up smoking, losing weight and lowering blood pressure, for example—is the first line of defense, but we also have medical and surgical technologies that can help prevent strokes. The problem is that some clinicians are not taking sufficient advantage of these technologies and many patients are not even aware that they exist. More professional and consumer education is needed and access to anticoagulation services must be improved," said Dr. Matchar.

Many primary care physicians underuse warfarin mostly because they are not aware of the techniques for administering the drug safely and fear it will cause bleeding. Warfarin does increase the risk of bleeding in some patients and requires careful monitoring with regular blood tests. But when properly administered, the drug prevents 20 strokes for every major bleeding complication it causes. Aspirin also is used to reduce the risk of stroke, but the most recent clinical studies have shown that warfarin is superior to aspirin in preventing stroke.

Doctors also may be reluctant to prescribe warfarin because of the demands that monitoring makes on their time. Monitoring can be made more efficient and affordable by assigning routine testing to nurse practitioners or physician's assistants under the doctor's supervision. State-of-the-art warfarin monitoring services, called anticoagulation services, also can be integrated into existing laboratories or other facilities with in-house labs. This approach is particularly appropriate for managed care organizations, which are enrolling increasing numbers of older people who are at highest risk of stroke.

In the upcoming fifth and final year of the PORT, the Duke University researchers plan a randomized trial in managed care settings to determine the most cost-effective ways of providing anticoagulation services. The results could help increase the proliferation of these services, which presently exist on a limited scale.

The stroke prevention PORT also looked at carotid endarterectomy, or CE—a surgical procedure which is used for people with carotid artery disease. CE removes fatty plaque from the arteries that carry blood from the heart to the brain. Unclogging these arteries increases blood flow, removes sources of clotting, and prevents strokes. Results of the study show that the procedure is both beneficial and cost effective for people with stroke-related symptoms and a high degree of blockage.

For persons without symptoms but known blockages, carotid endarterectomy can result in a modest reduction in stroke risk. However, identifying blockages in persons without symptoms can involve expensive and invasive diagnostic screening procedures, such as angiography, which carry a significant risk of stroke or other complications. For this reason, the human and economic cost of screening large numbers of asymptomatic people would outweigh the benefits to the small number of candidates the procedure will find.

According to the researchers, complication rates, an important factor in determining the value of carotid endarterectomy, vary greatly by hospital and surgeon. Hospitals are encouraged to monitor complication rates to promote informed decisionmaking by patients and referring physicians.

Funded in September 1991 to improve health outcomes for persons at risk for stroke by identifying the most appropriate and cost-effective clinical strategies for stroke prevention, the stroke prevention study is one of 17 AHCPR-funded Patient Outcomes Research Team (PORT) projects currently underway. The study is based at Duke University in Durham, NC and involves researchers from eight collaborating centers: Department of Veterans Affairs Medical Center in Durham, NC; the Mayo Clinic in Rochester, MN; The University of North Carolina in Chapel Hill, NC; the Academic Medical Center Consortium in Rochester, NY; the Center for Health Economics Research in Waltham, MA; the Research Triangle Institute in Research Triangle Park, NC; The Bowman Gray School of Medicine in Winston-Salem, NC; the United Health Care Corporation in Minneapolis, MN; and the Emory University Center for Clinical Evaluation Services in Decatur, GA.

For additional information, contact AHCPR Public Affairs: Karen Migdail, (301) 427-1855 ; or Salina Prasad, (301) 427-1864.