The purpose of this study is to explore the benefit of the prasugrel monotherapy without aspirin as compared with the 1-month dual therapy with aspirin and prasugrel in terms of reducing bleeding events after percutaneous coronary intervention (PCI) using cobalt-chromium everolimus-eluting stents (CoCr-EES, XienceTM) in patients with high bleeding risk or under the acute coronary syndrome patients.
Inclusion Criteria: * Patients who are planned to have percutaneous coronary intervention with exclusive use of everolimus-eluting stent (XienceTM series). * Patients with high bleeding risk defined by Academic Research Consortium or acute coronary syndrome * Patients who could take dual antiplatelet therapy with aspirin and P2Y12 inhibitors for 1-month Exclusion Criteria: * Patients who are judged to be unsuitable for participation by the principal investigator and co-investigator * Patients with a known allergy to the study drugs * Patients enrolled in the ongoing prospective interventional studies