High Rate of Non Responders to Aspirin and/or Clopidogrel Treatment in the First Days Following Percutaneous Coronary Interventions: An Ex Vivo Study

Abstract number: P0510

Paniccia R, Costanzo M, Valente S, Lombardi A, Giglioli C, Bernardo F, Lazzeri C, Prisco D, Gensini GF, Abbate R

Aspirin (ASA) therapy following both acute myocardial infarction (AMI) and acute coronary syndromes (ACS) has been shown to reduce the relative risk of recurrent vascular events and death. However, the inhibition of platelet function by ASA is not uniform among patients and this may be relevant for the occurrence of new ischemic events. Recently, PFA-100 (DADE Behring, USA) closure time (CT) has been suggested as a possible tool to identify ASA-resistant patients. Aim of this study was to investigate the response to ASA + clopidogrel treatment in 60 patients with AMI or ACS after PCI, by assessing PFA-100 CTs by collagen + epinephrine (CT/EPI) and collagen + ADP (CT/ADP) cartridges. All patients were treated with 325 mg ASA once a day and clopidogrel – 300 mg bolus immediately before the procedure followed by 75 mg/day. Citrated blood samples were obtained 5–36 hours after the procedure and (in 42/60 patients) also 4–5 days after the PCI. A control group of 67 subjects, who had not taken any antiplatelet agent for 15 days before blood sampling, was also studied. ASA and clopidogrel responders were defined respectively as patients with a CT/EPI and a CT/ADP over the 95th percentile value in the control group (CT/EPI > 203 s and CT/ADP > 139 s). Five to 36 hours after PCI, 14/60 patients (23%) had normal CT/EPI values and 42/60 patients (70%) had normal CT/ADP values. Eighteen out of 60 patients (31%) showed both CTs prolonged, whereas 13/60 patients (22%) had both CTs in the normal range. Four to 5 days after PCI, 16/42 patients (38%) had normal CT/EPI values. Ten of these 16 patients had had prolonged CT/EPI values 5–36 hours after the procedure. Thirty-five out of 42 patients (83%) had normal CT/ADP values. Eight of these 35 patients had had prolonged CT/ADP values 5–36 hours after the procedure. In conclusion, short-term antiplatelet treatment with combination of ASA and clopidogrel does not prolong PFA-100 CTs in a relevant proportion of AMI and ACS patients. If this lack of ex vivo responsiveness to ASA and/or clopidogrel is related to an increased risk of medium–term cardiovascular complications should be assessed by further studies.