The Role of Aspirin Resistance in the Treatment of Acute Coronary Syndromes

Abstract

SummaryThe thrombosis in myocardial infarction (TIMI) Risk Score recognizes prior aspirin use as an independent risk factor for adverse outcomes in subjects presenting with an acute coronary syndrome. The etiology of this increased risk awaits clarification, but prior aspirin use may be associated with altered thrombus composition which is more resistant to current treatment modalities as compared with thrombus formation in subjects without prior aspirin use. Post hoc analysis of acute coronary syndrome trials has shown that prior aspirin users treated with unfractionated heparin are at particularly high risk. The addition of glycoprotein IIb/IIIa receptor inhibitor to unfractionated heparin or substitution of low-molecularweight heparin significantly improves outcomes in prior aspirin users. The prognostic significance of prior aspirin use in acute coronary syndromes has important implications not only in clinical practice, but also in the design and interpretation of clinical trials.

Previous Aspirin Use in Acute Coronary Syndromes

“…Although previous aspirin users in these 4 trials had more comorbidities than the group not previously using aspirin, these demographic differences were not present within the previous aspirin user group, and so risk factors alone cannot explain the heterogeneous response to antithrombin and antiplatelet therapies compared with UFH; nor can they explain why the differential response does not exist in the group not previously using aspirin (8).…”

Reply

“…Although previous aspirin users in these 4 trials had more comorbidities than the group not previously using aspirin, these demographic differences were not present within the previous aspirin user group, and so risk factors alone cannot explain the heterogeneous response to antithrombin and antiplatelet therapies compared with UFH; nor can they explain why the differ-ential response does not exist in the group not previously using aspirin (8).…”