Differential effect of previous antiplatelet use on stroke severity according to stroke mechanism.

BACKGROUND AND PURPOSE The effect of previous antiplatelet use on stroke severity is controversial. We assume that this controversy is attributable to its difference according to the stroke mechanism. METHODS Using a prospective stroke registry, patients who were hospitalized because of ischemic stroke and had relevant lesions on MRI were selected. Patients who were using anticoagulants or whose stroke subtype was categorized as stroke of other determined etiology or undetermined etiology were excluded. Baseline stroke severity was measured using the National Institutes of Health Stroke Scale scores at presentation and was compared between no previous antiplatelet users and previous antiplatelet users with stratification by stroke subtypes. RESULTS Among the 1622 patients, a total of 490 (30.2%) patients reported use of an antiplatelet within 1 week of stroke onset. The baseline National Institutes of Health Stroke Scale score showed no difference between the nonantiplatelet and antiplatelet groups by crude comparison. However, the interaction between previous antiplatelet use and stroke subtype was significant (P=0.023) in a multivariable analysis; when the study subjects were stratified by stroke subtype, the difference in baseline National Institutes of Health Stroke Scale between the nonantiplatelet and platelet groups was significant in the large artery atherothrombosis group but not in those with cardioembolism and small-vessel occlusion before and after adjustments. CONCLUSIONS Our study suggests that the reduction of initial stroke severity in the previous antiplatelet users may differ by stroke mechanism.