Rapid decline of cerebral microemboli of arterial origin after intravenousacetylsalicylic acid

Background and Purpose-The present study investigated the influence of the antiplatelet agent acetylsalicylic acid (ASA) on cerebral microembolism as detected by transcranial Doppler sonography (TCD). Methods-Nine patients with recent transient ischemic attack or minor stroke of arterial origin were investigated. Eight had not received an antiplatel et or anticoagulant medication before TCD, and in 1 patient a preexisting A SA medication (100 mg/d) had not been changed since the onset of stroke sym ptoms. An initial 1-hour TCD monitoring was extended for an additional 2.5 hours after an intravenous bolus injection of 500 mg ASA and was repeated f or 1 hour on the following day. Results-Microembolic signals (MES) were detected in all patients only an th e symptomatic side. After the ASA bolus injection, a significant drop of th e MES rate was found in 7 patients, all without previous medication, starti ng 30 minutes after the application (mean per hour = 25.1 [range, 6 to 66] versus mean per hour = 6.4 [range, 0 to 14]). In 3 of these patients, plate let aggregation tests were performed that demonstrated normal aggregation b efore bolus injection and inhibited aggregability as early as 30 minutes af ter bolus injection. The rate of MES remained unchanged in 1 patient withou t antiplatelet medication. The ninth patient, who had suffered an ischemic event on ASA, showed only a transient decrease of MES frequency. Conclusions-In patients with recent stroke of arterial origin, intravenous ASA can rapidly reduce cerebral microemboli as detected by TCD. Microemboli might be a useful parameter to monitor early effects of antiplatelet thera py.