Resistance to acetylsalicylic acid in patients after ischemic stroke

INTRODUCTION: Acetylsalicylic acid (ASA) due to its antiplatelet action is used in ischemic stroke therapy. The platelet response to ASA shows an interindividual variation. Decreased platelet sensitivity to ASA is termed as resistance to ASA. OBJECTIVES: The aim of the study was to assess the prevalence of resistance to ASA in stroke patients and discover dependence between resistance to ASA and stroke recurrence and certain genetic and environmental factors. PATIENTS AND METHODS: 59 patients aged 22-83 years (mean age: 53) who had ischemic stroke within the period of 1 month to 10 years prior to the study were analyzed. 51 patients received ASA in a daily dose of 75 mg, and 8 in a higher dose. ASA had been taken since the stroke episode. Resistance was analyzed using the PFA-100 and optical aggregometer, with adenosine diphosphate, collagen and arachidonic acid as platelet agonists. RESULTS: Resistance to ASA in patients after stroke is observed with frequency ranging from 9% in arachidonic acid-induced aggregometry to 65% in the PFA-100. There were correlations between platelet aggregation in response to various agonists (r = 0.37-0.77, p < or = 0.005), and between collagen-induced aggregation and the PFA-100 (r = -0.33, p = 0.016). Platelet aggregation induced by arachidonic acid (r = 0.39, p = 0.029) correlated with the stroke recurrence (n = 12). ASA resistance detected in aggregometry in response to collagen was more common in patients with 807CT genotype for Ia glycoprotein (p = 0.05), and in patients with diabetes (p = 0.039). CONCLUSIONS: In patients after ischemic stroke resistance to ASA is commonly observed. In patients with diabetes or C807Tglycoprotein Ia gene CT polymorphisms this phenomenon is more frequently detected.