title: Aspirin resistance is associated with increased 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
  We studied a total of 310 patients who were admitted within 48 hours of acute ischemic stroke onset. All patients had been taking aspirin for at least 7 days before stroke onset. Aspirin resistance, defined as high residual platelet reactivity (HRPR) on aspirin treatment, was measured using the VerifyNow assay and defined as an aspirin reaction unit ≥550. Initial stroke severity was assessed using the NIH Stroke Scale (NIHSS) score. Infarct volume was measured using DWI.
  
  
  RESULTS
  HRPR occurred in 86 patients (27.7%). The initial NIHSS score (median [interquartile range]) was higher in patients with HRPR than in the non-HRPR group (6 [3-15] vs 3 [1-8], p < 0.001). DWI infarct volumes were also larger in the HRPR group compared to the non-HRPR group (5.4 [0.8-43.2] vs 1.7 [0.4-10.3], p = 0.002). A multivariable median regression analysis showed that HRPR was significantly associated with an increase of 2.1 points on the NIHSS (95% confidence interval 0.8-4.0, p < 0.001) and an increase of 2.3 cm(3) in DWI infarct volume (95% confidence interval 0.4-3.9, p < 0.001).
  
  
  CONCLUSIONS
  Aspirin resistance is associated with an increased risk of severe stroke and large infarct volume in patients taking aspirin before stroke onset.
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea. ssbrain@hallym.ac.kr iyyar@hallym.ac.kr.
authors.forename: Mi Sun
authors.initials: MS
authors.lastname: Oh
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea.
authors.forename: Kyung-Ho
authors.initials: KH
authors.lastname: Yu
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea.
authors.forename: Ju-Hun
authors.initials: JH
authors.lastname: Lee
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea.
authors.forename: San
authors.initials: S
authors.lastname: Jung
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea.
authors.forename: Chulho
authors.initials: C
authors.lastname: Kim
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea.
authors.forename: Min Uk
authors.initials: MU
authors.lastname: Jang
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea.
authors.forename: Juneyoung
authors.initials: J
authors.lastname: Lee
authors.affiliation: From the Department of Neurology (M.S.O., K.-H.Y., J.-H.L., S.J., C.K., M.U.J., B.-C.L.), Hallym University College of Medicine, Hallym Neurological Institute; and Department of Biostatistics (J.L.), Korea University College of Medicine, South Korea. ssbrain@hallym.ac.kr iyyar@hallym.ac.kr.
authors.forename: Byung-Chul
authors.initials: BC
authors.lastname: Lee
mesh_terms: D000368:Aged; D001241:Aspirin / Q000627:therapeutic use*; D001921:Brain / Q000187:drug effects*; D002545:Brain Ischemia / Q000097:blood / Q000000981:diagnostic imaging / Q000188:drug therapy; D038524:Diffusion Magnetic Resonance Imaging; D004351:Drug Resistance; D005260:Female; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D010975:Platelet Aggregation Inhibitors / Q000627:therapeutic use*; D011446:Prospective Studies; D012044:Regression Analysis; D012306:Risk; D012720:Severity of Illness Index; D020521:Stroke / Q000097:blood / Q000000981:diagnostic imaging* / Q000188:drug therapy*
chemical_list: D010975:Platelet Aggregation Inhibitors; D001241:Aspirin