Association of Aspirin Resistance With Increased Stroke Severity and Infarct Size

Objective: To investigate the relationship between aspirin resistance and clinical and neuroimaging measures of stroke severity in acute stroke patients. Design: Prospective single-center survey of acute ischemic stroke patients receiving aspirin therapy. Setting: The Royal Melbourne Hospital, Parkville, Victoria, Australia. Patients: Ninety acute stroke patients who previously received aspirin therapy were enrolled. Main Outcome Measures: Clinical stroke severity was measured using the National Institutes of Health Stroke Scale (NIHSS) and stroke infarct size was measured using the Alberta Stroke Program Early CT Score (ASPECTS). Aspirin resistance was measured using the VerifyNow system. Results: The mean (SD) age was 75 (9.9) years and 64.4% were male. The median NIHSS score and ASPECTS were 4 (interquartile range [IQR], 3-10) and 9 (IQR, 6-10), respectively. Aspirin resistance was detected in 28.9% (95% CI, 0.19 to 0.38) of all patients. The median aspirin reaction unit (ARU) was 486.0 (IQR, 432.3-557.0). Every 1-point increase in ARU was associated with a 0.03-point increase in NIHSS score (95% CI, 0.01 to 0.04; P < .001) and a 0.02-point decrease in ASPECTS (95% CI, -0.03 to -0.01; P < .001). This corresponded to an approximate median increase of 1 point in NIHSS score for every 33-point increase in ARU or a decrease of 1 point in ASPECTS for every 50-point increase in ARU. Conclusions: Aspirin resistance is associated with increased clinical severity and stroke infarct volume in acute stroke patients. Our results support the need for a randomized controlled study to investigate alternative antiplatelet therapy in patients with aspirin resistance. JAMA Neurol. 2013;70(2):208-213. Published online November 19, 2012. doi:10.1001/jamaneurol.2013.601