Acute ischemic stroke is a common emergency event often treated with early anticoagulation, especially when in the presence of progressive stroke, stuttering transient ischemic attacks, posterior circulation strokes, and concomitant use of aspirin. Although the prognosis of these specific categories of ischemic stroke is poorer, anticoagulation even in these circumstances has little support in medical trials.

Stead abstracted a systematic review from the Cochrane Database that assessed the effect of anticoagulant therapy in the early treatment of patients with acute ischemic stroke. The review included 22 randomized, blinded, controlled clinical trials reported through January 2004 in which patients received any anticoagulant or placebo within two weeks of an acute stroke. The stroke could have been ischemic or hemorrhagic. Most of the patients included in this review come from a single study that evaluated subcutaneous heparin as the anticoagulant agent.

The review demonstrated no evidence that anticoagulant treatment reduced all-cause mortality, although there were nine per 1,000 fewer recurrent ischemic strokes and four per 1,000 fewer pulmonary emboli. However, these benefits were overwhelmed by negative outcomes of increasing symptomatic intracranial hemorrhages (nine per 1,000 more) and nine per 1,000 more extracranial hemorrhages. No particular anticoagulant demonstrated a net benefit.

The Cochrane Review concludes that immediate anticoagulation following acute ischemic stroke has no benefit. The author notes that the American Heart Association agrees that early anticoagulation in patients with stroke does not decrease the risk of early recurrence or neurologic deterioration and therefore is not indicated to treat patients with moderate or severe stroke because of the risk of serious intracranial bleeding. Anticoagulation also is not recommended within 24 hours of intravenous thrombolytic therapy. More studies are needed to see if certain subsets of patients, such as those with large vessel atherothrombosis or other high-risk categories, might benefit from early anticoagulation. If anticoagulation is an option, physicians should confirm that patients are not candidates for intravenous thrombolytic therapy and rule out hemorrhage using computed tomography.