S100A9 and myocardial infarction: Increased platelet levels of S100A8/A9 heterodimer have previously been linked with incident MI in patients with systemic lupus erythematosus,30 and we have demonstrated its utility as a biomarker in prediction of future cardiovascular events.31 High levels of S100A8/A9 are measured in the circulation after MI, as well as other inflammatory illnesses.32 Alongside protein measurements, we found platelet mRNA levels for S100A8 and S100A9 were increased at the time of STEMI when compared with platelets 3 days later.