June 2, 2000 An aspirin given to stroke patients immediately upon arrival at the hospital may help to prevent recurrent strokes in the high-risk time frame immediately following the first stroke, according to the results of a combined analysis of two large studies.
The study is in this month's Stroke: Journal of the American Heart Association.
While aspirin therapy has already been shown to reduce the long-term risk of a second stroke in survivors of ischemic strokes -- caused by clots blocking blood flow to the brain -- a combined analysis of 40,000 acute stroke patients finds that aspirin provides an immediate stroke-preventing benefit in the days and weeks following the stroke.
"Early aspirin therapy should be used much more widely," says the study's lead author ZhengMing Chen, M.D., D.Phil, Reader of Oxford University in England. "The message is: If someone comes to the hospital with acute ischemic stroke, start aspirin therapy as soon as possible and continue it long-term."
Chen headed a group of researchers who examined the data from two major stroke trials -- the Chinese Acute Stroke Trial (CAST) and the International Stroke Trial (IST) -- which studied 20,000 stroke patients each.
The analysis found that the risk of recurrent ischemic stroke is reduced by one third from just a few weeks of aspirin use, and the overall absolute benefit in preventing further stroke or death is about nine per 1,000 people within a month.
Aspirin works as a blood thinner, helping to prevent the further formation of stroke-causing clots. Early treatment is especially important because the likelihood of a recurrent stroke is highest immediately following an initial stroke.
"Preventing nine strokes or deaths out of 1,000 people may not sound like much," says Chen. "But if you consider there are several million strokes worldwide each year, by treating one million of those with one year of aspirin therapy, this will prevent about 20,000 strokes or deaths."
One of the main reasons why aspirin has not been given immediately to stroke patients is concern among doctors that it might cause bleeding in the brain. However, the study shows that aspirin is much safer than initially anticipated, and, according to Chen, benefits outweigh the risk for all types of patients studied.
In 773 patients studied who had a bleeding stroke and were inadvertently given aspirin, researchers found no great difference in the outcomes of patients who received aspirin and those who didn't.
"We can be confident that there is no great hazard in giving aspirin immediately to patients who have been diagnosed with ischemic stroke," says Chen. "Of course, there may be some groups who should not get aspirin, but even the results in those who had bleeding strokes are reassuring."
The American Heart Association's guidelines for treating acute ischemic stroke suggest that aspirin may be effective in patients with acute stroke, but that aspirin should not necessarily be used in conjunction with clot-busting thrombolytic therapy.
Imaging technology, such as a CT scan, will tell a neurologist if the stroke is the result of a clot or bleeding into the brain. Even if that is not available, researchers say there's no reason to withhold early aspirin treatment when ischemic stroke is suspected.
"Especially in developing countries where the CT scan is not widely available, this is important information," says Chen. "We must limit the number of hemorrhage patients who get aspirin, but it's also important to give the treatment to those who can immediately benefit."
Patients who arrived at the hospital within the first 48 hours of symptom onset were studied. In both trials, half of the patients were randomly allocated to receive medium-dose aspirin (160 milligrams per day for 4 weeks in CAST; 300 milligrams per day for 2 weeks in IST).
Researchers say overemphasizing the urgency of clot-busting treatment for stroke may lead to an underemphasis on prompt aspirin use. Even if people were to come to the hospital more than 48 hours after their stroke, researchers believe they would still benefit from receiving aspirin immediately.
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