Anyone can have a stroke, but some of us are more at risk. New research from Ontario’s Institute for Clinical Evaluative Sciences (ICES) and the Canadian Stroke Network found only 40 percent of ischemic stroke patients who had atrial fibrillation*, a heart disorder putting them at high risk of clots, received the effective anti-clotting drug warfarin before their stroke.
The findings published in Stroke: Journal of the American Heart Association also found those who were taking warfarin, three fourths weren’t taking adequate doses of the drug to prevent a stroke. The remainder was taking other, less effective medication or no medication for preventing blood clots and stroke. Overall, 90% of ischemic stroke patients with atrial fibrillation who were at high risk for stroke were not taking sufficient anti-coagulatant therapy at the time of their stroke. “These are missed opportunities for stroke prevention,” notes lead ICES investigator Dr. David Gladstone. “Sadly, we frequently see patients admitted to hospital with a devastating stroke who are known to have atrial fibrillation, yet were either not taking warfarin or were taking a dose that is not therapeutic. We consider these to be potentially preventable strokes.”
Investigators analyzed data from the Registry of the Canadian Stroke Network on 2,135 stroke patients admitted to 12 Ontario stroke centers. Among the 597 patients meeting study criteria with a first ischemic (clot-caused) stroke who were known to have atrial fibrillation, the strokes were disabling in 60% and fatal in 20%. Researchers say their findings are “particularly troublesome” because the patients in the study were all considered to be at high risk for stroke based on published criteria, were living independently and considered to be ideal candidates for warfarin. Researchers did not include patients with atrial fibrillation who were considered to be at lower risk of stroke, for whom milder blood thinners like Aspirin are usually sufficient.
“It’s a tragedy. On one hand we have an extremely effective and cheap medication for stroke prevention – wafarin – and on the other hand it remains under-used in people who would benefit most from it,” says Gladstone who is also a neurologist and researcher for the Heart and Stroke Foundation of Ontario. “We must always weigh the pros and cons of any medication for patients, but for most high risk atrial fibrillation, the benefits of taking warfarin for stroke prevention greatly outweigh the potential side effects including serious bleeding complications.” Treatment guidelines for warfarin use are based on solid evidence from 29 major trials demonstrating the anti-clotting drug’s effectiveness for stroke prevention in high risk patients with this heart disorder.
Atrial fibrillation is a risk factor for stroke, because when the heart beats irregularly, or fibrillatres, blood clots can form in the upper chamber of the heart; the clots can travel to the brain and block an artery, causing ischemic stroke. The blood thinner warfarin has been available for many years and is the most effective stroke prevention medication worldwide for high-risk individuals with atrial fibrillation, reducing the risk of stroke by about 70% percent. Strokes caused by atrial fibrillation tend to be severe, and other studies have shown that warfarin is associated with a reduction in stroke severity.
ICES researchers say their findings have immediate implications for improving patient care. Providing patient education tools, reminders to physicians and system wide changes such as more widespread establishment of specialized anticoagulation management clinics may be some ways to help improve the situation. “This is a public health priority because atrial fibrillation is one of the most common causes of stroke. Many more strokes could be prevented if anticoagulation therapy were optimized in the population at risk”, says Gladstone.
*Atrial fibrillation is the most common type of irregular heartbeat that involves the two upper chambers of the heart. Affecting approximately 200,000 to 250,000 Canadians and about 6 percent of people 65 and older have atrial fibrillation. It is estimated that 1 in 6 all ischemic strokes (and 1 in 4 in the elderly) are caused by atrial fibrillation.
Dr. Gladstone’s research is supported by the Heart and Stroke Foundation of Ontario, the Heart and Stroke Foundation Centre for Stroke Recovery, and the Department of Medicine at Sunnybrook Health Sciences Centre and University of Toronto.
This study was funded by the Canadian Stroke Network.
Author affiliations: ICES (Drs. Gladstone, Kapral, Tu, Laupacis, Silver, Mr. Fang, Lindsay); Division of Neurology, University of Toronto (Drs. Gladstone, Bui, Silver); Department of Medicine, Sunnybrook Health Sciences Centre, University of Toronto (Dr. Lindsay); Department of Medicine, University of Toronto (Drs. Laupacis, Lindsay, Tu, Kapral); Division of General Internal Medicine and Clinical Epidemiology, University Health Network (Dr. Kapral); University Health Network Women’s Health Program (Dr. Silver, Kapral); Department of Health Policy, Management and Evaluation, University of Toronto (Drs. Tu, Kapral); Heart and Stroke Foundation Centre for Stroke Recovery (Dr. Gladstone); Keenan Research Centre at the Li Ka Shing Knowledge Institute of St. Michael’s Hospital (Dr. Laupacis)— Ontario.
ICES is an independent, non-profit organization that uses population-based health information to produce knowledge on a broad range of health care issues. Our unbiased evidence provides measures of health system performance, a clearer understanding of the shifting health care needs of Ontarians, and a stimulus for discussion of practical solutions to optimize scarce resources. ICES knowledge is highly regarded in Canada and abroad, and is widely used by government, hospitals, planners, and practitioners to make decisions about care delivery and to develop policy.
FOR FURTHER INFORMATION PLEASE CONTACT:
- Kristine Galka
- Media Advisor, ICES
- 416-480-4780 or 416-629-8493
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