Objective: Acute coronary syndromes (ACS) such as unstable angina, myocardial infarction, or sudden ischemic death evolve from coronary thrombosis and as a consequence of atherosclerotic plaque disruption. “Aspirin resistance” is a poorly defined term to describe the inability of aspirin to protect individuals from thrombotic complications and there are conflicting reports on prevalence rates and clinical relevance of this phenomenon. The aim of this study is to determine the prevalence of aspirin resistance in the patients with acute coronary syndromes.

Materials and Methods: We determined the prevalence of aspirin resistance in ACS patients by prospectively studying 30 patients (Age: 62.5±8 years) (mean±SD) with acute coronary syndromes who were receiving aspirin (325 mg/ day for 7 days) but no other antiplatelet agents. Blood samples were analyzed for aspirin resistance by Chronolog 560 CA impedence aggregometry using collagen, thrombine and adenosine diphosphate (ADP) reagents.

Results: 8 of 30 patients were aspirin resistant (26.7%) and 22 of 30 were aspirin sensitive (73.3%). There were no differences in aspirin sensitivity by age, sex, diabetes mellitus, smoking, platelet count, haemoglobin concentration or antilipid drug usage. However, aspirin resistance was lower in patients who had hypertension and used antihypertensive drug.

Conclusion: In this study, the prevalence of aspirin resistance in the patients with acute coronary syndromes was found high.Because aspirin resistance may cause many serious problems in acute coronary syndromes, it will ultimatelly be important to prospectively diagnose this syndrome before initiating long-term antiplatelet therapy given the choise of aspirin or other antiplatelet agents.