This study builds, in part, upon preliminary results generated as part of the Pharmacogenomics Anti-Platelet Intervention (PAPI) Study (NCT00799396). The purpose of this investigation is to assess the impact of genetic variation in the carboxylesterase 1 (CES1) on response to clopidogrel as well as dual antiplatelet therapy (i.e. clopidogrel and aspirin), as assessed by ex vivo platelet aggregometry, in healthy Amish individuals. The investigators hypothesize that participants who carry alleles that modify the activity or expression of CES1 will have altered response to clopidogrel as well as dual antiplatelet therapy.