High on-treatment platelet reactivity: risk factors and 5-year outcomes in patients with acute myocardial infarction

OBJECTIVE: The aim of the present study was to assess long-term prognostic value of high on-treatment platelet reactivity (HTPR) in patients after acute myocardial infarction (MI) and its association with possible risk factors. METHODS: This prospective, case-control study was an observation of 198 patients who had acute MI. Response to aspirin and clopidogrel was assessed using impedance aggregometry. Patients were divided into groups of adequate response, dual poor responsiveness (DPR), poor responsiveness to aspirin (PRA), and poor responsiveness to clopidogrel (PRC). Simultaneously, potential risk factors of HTPR development were recorded. After 5 years, MI recurrence and overall mortality were assessed. RESULTS: HTPR was more frequent in New York Heart Association Class III and IV patients, and in patients with left ventricle systolic dysfunction. Five-year mortality rate was higher in all groups of patients with HTPR compared to patients with sufficient response to antiplatelet treatment: in PRA patients, 38.1% vs. 19.2%, p<0.01; in PRC patients, 45.2% vs. 17.3%, p<0.001; and in DPR patients, 50.0% vs. 19.9%, p<0.05. Risk of repeat MI also increased (hazard ratio [HR] 4.0, p<0.05 for DPR group; HR 4.37, p<0.01 for PRA group; and HR 3.25, p<0.05 for PRC group). CONCLUSION: PRA, PRC, and DPR are independent predictors of increased 5-year mortality and risk of repeat non-fatal MI. The study has demonstrated that HTPR is frequently observed in patients with severe heart failure and left ventricle systolic dysfunction.