Aspirin resistance measured by cationic propyl gallate platelet aggregometry and recurrent cardiovascular events during 4 years of follow-up

Background: Aspirin resistance appears to be an important prognostic factor in patients with coronary artery disease, yet there is no standardized method to measure it and limited data on its correlation to clinical outcomes. Methods: In a prospective study we followed 103 patients (mean age 64 years) with acute coronary syndrome (ACS) without ST segment elevation who were treated with 100 mg of aspirin (ASA) daily. Optical platelet aggregometry using cationic propyl gallate (CPG) as an inductor was measured at ACS onset and after 3, 12, 24, 36, and 48 months. ASA responsiveness was defined both by the slope of the aggregation curve (<53%/min) and by spontaneous aggregation (<5%). The primary outcomes were the recurrence of ACS or stroke. Results: Patients with ACS exhibited a greater prevalence of ASA resistance (55%) than healthy volunteers (4%; p<0.01). ASA resistance Occurred more often in patients with type 2 diabetes, hypertriacylglycerolemia, and decreased HDL levels, and in smokers (P<0.05). A single assessment of platelet aggregometry was sufficient to identify ASA-resistant patients. During the 4-year follow-up, the patients with ASA resistance had an 88% incidence of recurrent cardiovascular events versus 46% for the patients without ASA resistance (p<0.01). In the subgroup with recurrent cardiovascular (CV) events, significantly more patients were ASA-resistant than in the subgroup without recurrent CV events (72% vs. 8%, p <0.01). Conclusion: ASA resistance measured by CPG-induced platelet aggregometry is more common among patients with ACS and some metabolic risk factors, and ASA-resistant patients have a significantly higher recurrence of cardiovascular events. (C) 2006 European Federation of Internal Medicine. Published by Elsevier B.V All rights reserved.