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 cm3 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.