Residual platelet reactivity after aspirin and clopidogrel treatment predicts 2-year major cardiovascular events in patients undergoing percutaneous coronary intervention.

BACKGROUND: Studies on the prognostic significance of residual platelet reactivity despite the use of dual anti-platelet agents are limited and seldom extend beyond 1year.

METHODS: This study enrolled 144 patients treated with standard-dose aspirin and clopidogrel and undergoing percutaneous coronary intervention (PCI). Platelet reactivity was measured by the Platelet Function Analyzer-100 (PFA-100) just before PCI and presented as collagen/epinephrine closure time (CEPI-CT) and collagen/adenosine diphosphate closure time (CADP-CT). Primary endpoint included cardiovascular death, myocardial infarction, and stroke. Secondary endpoint was the primary endpoint plus hospitalization due to unstable angina or urgent target vessel revascularization.

RESULTS: During the 24-month follow-up, 14 patients (9.7%) developed the primary endpoint events and 33 had the secondary endpoints. After controlling possible confounding factors, both CEPI-CT <193s and CADP-CT <95s were independently predictive of the primary endpoint (hazard ratio=3.5; 95% confidence interval: 1.04-11.7; p=0.044 and 5.3; 1.4-20.1; p=0.015, respectively). Only CADP-CT <95s remained significantly predictive of secondary endpoints in the follow-up periods of 0-9 and 9-24months, during which clopidogrel was mostly discontinued.

CONCLUSION: This study demonstrates that increased residual platelet reactivity measured by PFA-100 CADP-CT consistently predicts the occurrence of cardiovascular events following PCI throughout the 24-month follow-up period, irrespective of the changes in anti-platelet use.