Aspirin resistance and adverse clinical events in patients with coronary artery disease

PURPOSE: We sought to determine the clinical significance of aspirin resistance measured by a point-of-care assay in stable patients with coronary artery disease (CAD). METHODS: We used the VerifyNow Aspirin (Accumetrics Inc, San Diego, Calif) to determine aspirin responsiveness of 468 stable CAD patients on aspirin 80 to 325 mg daily for >= 4 weeks. Aspirin resistance was defined as an Aspirin Reaction Unit >= 550. The primary outcome was the composite of cardiovascular death, myocardial infarction (MI), unstable angina requiring hospitalization, stroke, and transient ischemic attack. RESULTS: Aspirin resistance was noted in 128 (27.4%) patients. After a mean follow- up of 379 +/- 200 days, patients with aspirin resistance were at increased risk of the composite outcome compared to patients who were aspirin-sensitive (15.6% vs 5.3%, hazard ratio [HR] 3.12, 95% confidence intervals [CI], 1.65-5.91, P < .001). Cox proportional hazard regression modeling identified aspirin resistance, diabetes, prior MI, and a low hemoglobin to be independently associated with major adverse long-term outcomes (HR for aspirin resistance 2.46, 95% CI, 1.27-4.76, P = .007). CONCLUSIONS: Aspirin resistance, defined by an aggregation-based rapid platelet function assay, is associated with an increased risk of adverse clinical outcomes in stable patients with CAD. (c) 2007 Elsevier Inc. All rights reserved.