High On-Treatment Platelet Reactivity Predicts Cardiac Events in Patients with Drug-Eluting Stents

BACKGROUND: The role of platelet reactivity (PR) tests in the prediction of long-term events in Latin-American patients treated with drug-eluting stents (DES) has not been established. OBJECTIVES: To assess the role of PR tests in the prediction of events after DES implantation. METHODS: From May 2006 through January 2008, 209 Brazilian patients who underwent elective treatment with DES were included. PR was assessed 12 to 18h after the procedure by light transmittance aggregometry with 5µM of ADP. Patients were prospectively followed for up to 4.8 years. Seventeen (8%) individuals were lost to follow-up and the final cohort comprised 192 patients. Receiver operating curve (ROC) was used to determine the best 5µM of ADP cutoff to predict events. The primary endpoint was a combination of cardiovascular death, acute myocardial infarction, definite stent thrombosis, and target-artery revascularization. Cox proportional hazard models were used to determine the variables independently associated with the time to the first event. RESULTS: The best ADP 5µM cutoff was 33%. One hundred and seven (55.7%) patients had ADP 5µM >33%. Event-free survival rate at 1,800 days was 55% vs. 70% for individuals with ADP5 above and below such cutoff, respectively (p=0.001). Independent predictors of time to first event were current smoking (HR 3.49; 95% CI 1.76-6.9; p=0.0003), ADP 5µM >33% (HR 1.95; 95% CI 1.09-3.51; p=0.025) and age (HR 1.03; 95% CI 1.0-1.06; p=0.041). CONCLUSIONS: In this study, 55.7% of the patients had high on-treatment platelet reactivity. ADP 5µM >33% was an independent predictor of long-term events.