Pharmacodynamic safety of clopidogrel monotherapy in patients under oral anticoagulation with a vitamin K antagonist undergoing coronary stent implantation.

Current guidelines recommend as treatment option in patients on oral anticoagulation (OAC) undergoing percutaneous coronary intervention (PCI) an antiplatelet monotherapy with clopidogrel if there is an increased risk for bleeding. However, retrospective data suggested a potential interaction of clopidogrel and the vitamin K antagonist (VKA) phenprocoumon leading to a diminished antiplatelet effect. This would increase the ischemic risk of patients treated with this combination. Thus, this prospective study sought to evaluate the pharmacodynamic effect of clopidogrel monotherapy in patients on phenprocoumon undergoing PCI and assessed clinical outcomes. This study enrolled 100 patients on aspirin plus clopidogrel (DAPT-cohort, without indication for VKA) and 100 patients on clopidogrel monotherapy plus phenprocoumon (OAC-cohort) undergoing elective PCI. Platelet reactivity was assessed by impedance aggregometry on day 1 following PCI. Ischemic (death, stroke, or myocardial infarction) and bleeding (BARC 2-5) events within 12 months were compared in a propensity score adjusted model. Platelet reactivity was not different in the OAC- and DAPT-cohort (187 [127-242] vs. 167 [126-218] AU×min;