Abstract 15728: Platelet Count Predicts Cardiovascular Mortality in Very Elderly Patients with Acute Myocardial Infarction

Abstract

Background. Demographic changes led to an increase of elderly patients in the general population. Elderly patients (≥75 years) account for 60% of MI deaths and display higher rates of MI-related complications. However, these high-risk patients have been underrepresented in previously published cardiovascular clinical trials relative to their younger counter-parts or have been even excluded in interventional trials. Therefore, identification of specific risk factors to improve cardiovascular risk prediction in elderly patients is crucial. Objective. To assess the influence of platelet count on cardiovascular mortality in very elderly patients with acute myocardial infarction (≥85 years of age). Methods. We retrospectively performed a matched and nested case-control study to assess the differences between 208 very elderly (≥ 85 years) and 208 young MI patients (≤ 65years) at admission and a cohort design to assess the impact of risk factors on the outcome with a median follow-up of 3.4 years. Results. The effect of platelet count on cardiovascular mortality in very elderly and young AMI patients was significantly different (p for interaction=0.009). An increased platelet count was a significant and independent risk factor for cardiovascular mortality in very elderly AMI patients (adjusted hazard ratio (HR) per 1-SD increase 1.30; 95%CI 1.06-1.60; p=0.013) while there was an inverse association between platelet count and cardiovascular mortality in young patients (adjusted HR 0.20; 95%CI 0.00-0.60; p=0.004). Conclusion. Identification of specific risk factors in very elderly patients constitutes an important field of future medical research. Our study demonstrates a strong and independent association between elevated platelet count and long-term cardiovascular mortality in this vulnerable patient group. Nevertheless, the pathophysiologic mechanisms underlying this age-dependent effect have to be further clarified.