Aspirin resistance in acute ischemic stroke: association with stroke severity and infarct volume

Abstract

Objective To investigate whether aspirin resistance is associated with initial stroke severity and infarct volume using diffusion-weighted imaging (DWI) in patients with acute ischemic stroke that occurred while taking aspirin. Methods 350 patients admitted within 48 hours of acute ischemic stroke onset were selected as study objects. All patients had been taking aspirin for at least 7 days before stroke onset. Aspirin resistance, defined as high residual platelet reactivity (HPR) on aspirin treatment, was measured using PL assay and defined as MAR-AA more than 35%. Initial stroke severity was assessed using NIH Stroke Scale (NIHSS). Infarct volume was measured by DWI. Results HPR occurred in 93 patients (26.6%). The initial NIHSS score (median [interquartile range]) was higher in the aspirin resistant group than in the aspirin sensitive group (10 [4-15] vs. 4 [2-6], P<0.001). DWI infarct volumes were also larger in the aspirin resistant group than in the aspirin sensitive group (5.3 [1.2-9.6] vs. 1.8 [0.8-8.8], P<0.01). A multivariable median regression analysis showed that HPR was significantly associated with an increase of 6.0 points on NIHSS (95% CI 3.68-8.31, P<0.001) and an increase of 2.8 cm3 in DWI infarct volume (95% CI 0.6-6.2, P<0.01). Conclusions Aspirin resistance is associated with an increased risk of severe stroke and large infarct volume in patients taking aspirin before stroke onset. Key words: Acute ischemic stroke; Aspirin resistance; High residual platelet reactivity; PL-11