Post-Treatment Platelet Reactivity Predicts Long-Term Adverse Events Better Than the Response to Clopidogrel in Patients With Non-ST-Segment Elevation Acute Coronary Syndrome

Received February 28, 2008. Accepted for publication October 2, 2008. See editorial on pages 113-6 Introduction and objectives: Poor response to antiplatelet therapy has been associated with adverse long-term outcomes. The objective of this study is to assess the relationship between response to clopidogrel and post-treatment platelet reactivity (PPR) and 1-year major adverse cardiovascular events (MACE) in patients with non-ST segment elevation acute coronary syndrome (NSTEACS). Methods: Patients with NSTEACS undergoing early coronary angiography were enrolled in this prospective, observational study. The VerifyNow® analyzer was used to measure clopidogrel response and PPR immediately before coronary angiography. Results: Of the 179 patients included (97 percutaneous coronary intervention, 21 coronary artery bypass graft), 161 (90%) completed 1-year follow-up and 18 (11%) incurred MACE: 10 deaths, 6 myocardial infarctions, 2 strokes, 5 revascularizations. Lower response to clopidogrel (31±21% vs. 43±21%; P=.049) and higher PPR (204±60 vs. 155±67 platelet reaction units [PRU]; p=.006) were significantly associated with MACE occurrence. Multivariate analysis confirmed PPR (OR per 10-unit increase, 1.12, 95% CI, 1.01-1.24; P=.020) as an independent predictor of MACE. A PPR cut-off value of 175 PRU was associated with an adjusted OR for 1-year MACE occurrence of 3.9 (95% CI, 1.2-15.4; P=.024). Conclusions: PPR predicts adverse long-term outcomes better than response to clopidogrel in patients with NSTEACS. Patients with PPR values above 175 PRU were identified as being at higher risk for adverse longterm events.