Clopidogrel high-on-treatment platelet reactivity in acute ischemic stroke patients.

Background: During the first days following an acute ischemic stroke, a consistently good antiplatelet effect of clopidogrel is important due to the increased risk of recurrent ischemia. However, the platelet inhibitory effectiveness of clopidogrel is variable for multifactorial reasons. We investigated the prevalence and risk factors for clopidogrel high-on-treatment platelet reactivity (clopidogrel-HTPR) in acute ischemic stroke patients. Methods: Using multiple-electrode impedance aggregometry (MEA), the antiplatelet effectiveness of clopidogrel in patients with acute ischemic stroke was prospectively evaluated. Measurements were performed 48 h after therapy was either initiated or continued after hospital admission. Clopidogrel-HTPR was defined as ADP-induced values > 47 U. Results: A total of 159 patients (71.8 +/- 9.8 years, 69 female) were enrolled and 44% (n = 70) patients were clopidogrel-HTPR. 35 of the clopidogrel-HTPR were retested within one week and 57.1% (n = 20) showed a good clopidogrel response during subsequent testing. We identified diabetes mellitus (36.3% vs. 54.4%, p-value = 0.003) and higher HbA1c values (6.3% vs. 6.8%, p = 0.007) as risk factors for clopidogrel-HTPR. Multivariate regression analysis revealed that diabetes mellitus more than doubled the risk of clopidogrel-HTPR (OR 2.41; 95%-CI 1.19-4.88; p = 0.015). Conclusions: Clopidogrel-HTPR was found in 44% of the patients with acute ischemic stroke. Besides time-dependency of the clopidogrel effect, major risk factors for clopidogrel-HTPR were diabetes mellitus and higher HbA1c values. Further investigations are required to analyse if a function test guided strategy has the potential to optimize the antiplatelet therapy of acute stroke patients. (C) 2013 Elsevier Ltd. All rights reserved.