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8/21/2000

Newer Heparin No Better Than Aspirin in Preventing Second Stroke in Certain Patients

Cheryl A. Thompson

Research findings suggest that low-molecular-weight (LMW) heparin does not work better than aspirin at preventing a second stroke in the initial 14 days after the first one in patients with atrial fibrillation.

Although LMW heparins have previously been tested for the secondary prevention of stroke, none of the patients evaluated had atrial fibrillation, a condition that increases the risk for ischemic stroke. Researchers in Norway decided, therefore, to put this type of anticoagulant to the test against aspirin, which has been found useful for the secondary prevention of stroke in patients with atrial fibrillation.

Within 30 hours of the onset of stroke caused by a decrease in blood supply, 449 adults with atrial fibrillation at 45 medical centers were randomly assigned to receive one of two treatments: 100 IU/kg of dalteparin by subcutaneous injection twice daily plus placebo tablets daily, or 160 mg of aspirin daily plus placebo injections twice daily.

During the first 14 days, a second stroke occurred at about the same rate in both treatment groups: 8.5 percent in the dalteparin group, and 7.5 percent in the aspirin group. Neurological and functional status of the patients in the two groups did not differ during this period.

All the patients were at least 44 years old, and half the patients in each group were at least 80 years old. Eighty percent of the patients continued their assigned treatment for 11 to 17 days.

Although this study, published in the April 8 issue of Lancet, sought to determine whether one agent outperformed the other at preventing a second stroke, the serious toll of the initial ischemic stroke on patients emphasizes the importance of primary prevention. About 65 percent of patients in both groups were dead or functionally dependent three months after the initial stroke. The American Society of Health-System Pharmacists recommends the routine use of an antithrombotic agent such as aspirin to prevent stroke in patients with chronic atrial fibrillation.

The researchers, whose study received financial support from the manufacturers of dalteparin and the aspirin product, advised that clinicians prescribe aspirin therapy for the first 14 days after a stroke and consider following up with a short-term regimen of low-dose LMW heparin to prevent venous thromboembolism. This latter recommendation comes not from observations in the present study but from the generally accepted value of heparins as protectants against venous thromboembolism in patients with acute stroke.