Evaluation of aspirin resistance and the presence of unstable carotid plaque in patients undergoing carotid endarterectomy

Background: Antiplatelet therapy using low dose acetylsalicylic acid (ASA) is routinely recommended in patients undergoing surgical or endovascular treatment of carotid artery disease. Despite this treatment, a significant proportion of postoperative complications may result from inadequate response to antiplatelet therapy which may contribute to the development of unstable plaques. Aim: Assessment of correlation between ASA resistance and the presence of unstable carotid plaque in patients after carotid endarterectomy. Methods: We studied 66 patients (27 women and 39 men) aged 41–80 years who were operated for carotid stenosis. All patients received ASA (75 mg once daily) in the pre- and perioperative period. Measurements of platelet reactivity were performed using the PFA-100 platelet analyser at the second day after the operation. Plaque stability was evaluated using a computer analysis system based on the greyscale median method. The patients were divided into two groups, showing good response to ASA or ASA-resistant. Results: ASA resistance was identified in 19 (32%) patients. In multivariate logistic regression analysis, unstable plaque showed a borderline correlation with ASA resistance (p = 0.051). Conclusions: 1. Prevalence of increased platelet reactivity despite ASA treatment (ASA resistance) in patients treated surgically for carotid artery disease is high, suggesting a possibility of ineffective antiplatelet therapy. 2. A modest correlation between abnormal platelet response during treatment with ASA and the presence of unstable plaques suggests that these two phenomena may coexist but we were unable to show a clear association between them.