Background : The prevalence of aspirin resistance was very variable according to methods to measure the degree of platelet inhibition in Caucasian. The objective of this prospective study was to determine the prevalence and predictors of aspirin resistance in patients undergoing percutaneous coronary intervention in Koreans using a point-of-care system. Methods and results : A total of 123 patients underwent percutaneous coronary intervention at our institution were consecutively enrolled. The VerifyNow Aspirin® (Ultegra RPFA-ASA, Accumetrics Inc, San Diego, Calif) was used to determine aspirin responsiveness. Aspirin reaction unit (ARU)≥550 was defined as the absence of aspirin-induced platelet dysfunction. Patients were divided into four groups according to maintenance period of aspirin; < 24 hrs (group 1, n=30), from 1 to 7 days (group 2, n=18), from 8 to 4 weeks (group 3, n=11), and ≥ 4weeks (group 4, n=64). Group 1 had been loaded with aspirin 300mg and those of other groups had been received aspirin 100mg qd as a maintenance dose. Mean age of patients enrolled this study was 61.9±9.7 years and most patients were men (72.4%). 29.3% of the patients had a history of diabetes mellitus and 61.8% had a history of hypertension. A total of 10 (8.1%) patients had aspirin-resistance. Mean ARU were 582.8±25.26 versus 435.91±64.02 (Aspirin resistance group vs. aspirin sensitive group). There were no significant differences of baseline characteristics in two groups. In subgroup analysis according to maintenance period of aspirin, there was no significant difference in the incidence of aspirin resistance (3.3% in group 1, 5.9% in group 2, 0% in group 3, and 2.7% in group 4, p=0.68) among four groups. Patients who had been loaded with aspirin 300mg one day before PCI showed no differences in ARU and prevalence of aspirin resistance compared to patients who maintained aspirin for more than 1month. Conclusions : In Koreans with coronary artery disease, the prevalence of aspirin resistance determined by VerifyNow Aspirin® was about 8%. Aspirin single loading was as effective as long-term maintenance in patients who underwent percutaneous coronary intervention
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