UNLABELLED: Several studies have reported a biochemical resistance to aspirin in 5 to 10% of coronary patients. However, the stability of the platelet anti-aggregation effect with aspirin over time remains poorly understood. OBJECTIVE: To study the intra-individual variability at 6 months of the anti-platelet action of aspirin in coronary patients. METHOD: Prospective study including 40 consecutive patients with acute coronary syndrome and taking regular aspirin (250 mg a day). The biochemical impact of aspirin was determined by measuring the time to occlusion (TO) on a collagen/epinephrine cartridge with PFA-100. The determination of the TO was performed 2 months (TO1) and then 8 months (TO2) after starting aspirin. In our population, a resistance to aspirin was defined as a TO < or =125 sec. RESULTS: The median value for TO was generally stable over the two periods, at 158 sec for TO1 and 179 sec for TO2 (p = 0.29). Among the 9 initially resistant patients (22.5%), 4 became sensitive to aspirin without changing the dosage, while only one of the 31 initially sensitive patients became biochemically resistant. CONCLUSION: the existence of a medium term intra-individual variability in the antiplatelet response to aspirin in coronary patients underlines the importance of biochemical surveillance in these high vascular risk patients.
UNLABELLED: Several studies have reported a biochemical resistance to aspirin in 5 to 10% of coronary patients. However, the stability of the platelet anti-aggregation effect with aspirin over time remains poorly understood. OBJECTIVE: To study the intra-individual variability at 6 months of the anti-platelet action of aspirin in coronary patients. METHOD: Prospective study including 40 consecutive patients with acute coronary syndrome and taking regular aspirin (250 mg a day). The biochemical impact of aspirin was determined by measuring the time to occlusion (TO) on a collagen/epinephrine cartridge with PFA-100. The determination of the TO was performed 2 months (TO1) and then 8 months (TO2) after starting aspirin. In our population, a resistance to aspirin was defined as a TO < or =125 sec. RESULTS: The median value for TO was generally stable over the two periods, at 158 sec for TO1 and 179 sec for TO2 (p = 0.29). Among the 9 initially resistant patients (22.5%), 4 became sensitive to aspirin without changing the dosage, while only one of the 31 initially sensitive patients became biochemically resistant. CONCLUSION: the existence of a medium term intra-individual variability in the antiplatelet response to aspirin in coronary patients underlines the importance of biochemical surveillance in these high vascular risk patients.