Risk of stroke during long‐term anticosgulant therapy in patients after myocardial infarction

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Abstract
Myocardial infarction survivors have an increased risk of stroke, which is reduced with long‐term anticoagulant therapy. However, an estimated 10‐times increase in risk of bleeding during such treatment has been reported. We evaluated the risk of stroke in patients after a myocardial infarction and examined the relationship of the risk of intracranial hemorrhage or cerebral infarction and the intensity of anticoagulant therapy. The study population consisted of 3,404 post‐myocardial infarction patients who took part in a randomized, double‐blind, placebo‐controlled trial. Patients were randomized to treatment with anticoagulants (international normalized ratio range, 2.8–4.8) or matching placebo. Mean follow‐up was more than 3 years. The incidence of stroke analyzed on “intention‐to‐treat” was 0.7 per 100 patient‐years in the anticoagulant patients against 1.2 in placebo, a hazard ratio of 0.60, with 95% confidence interval of 0.40 to 0.90. In the anticoagulation group, 15 patients had cerebral infarction and 17 an intracranial bleeding, 3 of which occurred after withdrawal of treatment. In the placebo group, the numbers were 43 and 2. Of the 14 intracranial bleeds during anticoagulation, 6 occurred at an international normalized ratio between 3.0 and 4.0 and 8 at greater than 4.0. These results confirm that long‐term anticoagulant therapy substantially reduces the risk of stroke in post‐myocardial infarction patients. The increased risk of bleeding complications associated with anticoagulant therapy is offset by a marked reduction in ischemic events. The risk of intracranial bleeding is directly related to the intensity of anticoagulant treatment.