High frequency of aspirin resistance in patients with acute coronary syndrome.

Aspirin is widely used for secondary prevention of cardiovascular disease, but is not effective for all patients. This phenomenon is called as aspirin resistance. Although the prognosis is worse in patients who develop acute coronary syndrome (ACS) while using aspirin, the frequency of aspirin resistance in these patients has not been evaluated. We aimed to evaluate the frequency of aspirin resistance in patients with ACS and to determine its relationship with the angiographic severity and extent of the associated coronary artery disease. The present study included 104 patients with ACS (75 men, 60.4 +/- 10.8 years) who were hospitalized while using aspirin for at least last 7 days and 100 patients with stable coronary artery disease (73 men, 57.6 +/- 10.6 years), documented by coronary angiography, history of revascularization or myocardial infarction (MI), and the use of aspirin for last 7 days. The latter group had no MI or ACS for last 3 months. Platelet function was assessed with PFA-100, which simulates primary homeostasis at injured blood vessels. Coronary angiography was performed in 83 cases of the patients with ACS during hospital stay. Aspirin resistance is more prevalent in patients with ACS (40.3%) when compared with stable coronary artery disease patients (27%). The difference was statistically significant (p = 0.04). The ACS patients with aspirin resistance were older and had severe myocardial damage. However, there were no significant differences in angiographic severity and extent of coronary artery disease between aspirin-resistant and aspirin-sensitive patients. Frequency of aspirin resistance is higher in patients who develop ACS while using aspirin than that in patients with stable coronary artery disease.