Abstract 2358: What is the Better Predictor of Long-Term Post-PCI Ischemic Events? Pre-Treatment vs. Post-Treatment Platelet Reactivity to ADP
Background: High post-treatment platelet reactivity to adenosine diphosphate (post-ADP) has been reported as a risk factor for post-PCI ischemic events. It is unknown whether platelet reactivity to ADP measured before clopidogrel therapy (Pre-ADP) can also risk-stratify patients. We compared the predictive ability of Pre-ADP vs. Post-ADP for ischemic event occurrence following PCI.
Methods: Pre-ADP and Post-ADP (18 –24 hours post-procedure) were measured by light transmittance aggregometry (LTA) in 155 patients who underwent successful and uncomplicated elective coronary stenting. Patients received either a 600mg (n=110) or a 300mg (n=45) clopidogrel loading dose followed by 75mg daily maintenance therapy. Patients were followed for up to 2 years for ischemic event occurrence. Pre-ADP and Post-ADP were stratified into quartiles.
Results: Thirty-eight patients (24%) had ischemic events. Pre-ADP and Post-ADP were 63±10% and 37±16%, respectively (p<0.01). Pre-ADP had no relation to ischemic event occurrence, however upper quartile Post-ADP was highly associated with ischemic events (p=0.02 vs. upper quartile Pre-ADP, Table⇓); whereas 5% of patients in the lowest Post-ADP quartile had events. Only twenty-two percent of patients in the upper quartile of Pre-ADP remained in the upper quartile of Post-ADP following clopidogrel administration.
Conclusions: Long-term ischemic event ocurrence is not well predicted by platletet function measurements made before clopidogrel administration. However, high platelet aggregation on clopidogrel therapy is a powerful predictor of long-term post-PCI ischemic event occurrence. Measurement of platelet function before hospital dischearge may be a useful practice for targeting novel antiplatelet therapy in selected patients with high residual platelet reactivity.