Background: Previous studies showed that incidence of antiplatelet therapy resistance is higher in elderly patients. There is a paucity of data about the response to antiplatelet therapy in patients with atrial fibrillation (AF). The purpose of this study is to analyze platelet reactivity during dual antiplatelet therapy (DAPT) in elderly patients (≥ 75 years) with acute coronary syndrome (ACS), stratifying them by the presence or absence of AF.
Methods: From the PRATO-ACS registry we selected 160 patients (81±5 years; 45% female) treated with DAPT (Aspirin 100 mg daily and Clopidogrel 75 mg daily). At discharge they were tested with the VerifyNow assay to measure platelet reactivity in aspirin (aspirin-reaction unit – ARU) and in clopidogrel (P2Y12-reaction unit – PRU). Low response to aspirin was defined as ARU ≥550; low response to clopidogrel was defined as PRU ≥ 208; high response was defined as PRU values ≤ 85.
Results: The ARU and PRU values for patients divided according to the presence of AF are shown in the Figure 1.
Conclusions: In this series of elderly ACS patients, AF was associated with higher residual platelet reactivity under both clopidogrel and aspirin. AF patients were significantly more clopidogrel low responders than non-AF, while non-AF patients were significantly more high responders. No difference was found for aspirin low responders between AF and no AF patients.