Study to Evaluate the Safety of Reducing Dual Antiplatelet Therapy (DAPT) Duration to 1 Month for Patients With Acute Coronary Syndrome (ACS) After Implantation of Everolimus-eluting Cobalt-chromium Stent

The drug-eluting stents (DESs) are currently used in the majority of percutaneous coronary intervention (PCI) procedures. On the other hand, the problems of the first-generation DES (late adverse events, such as very late stent thrombosis) have been pointed out. Dual antiplatelet therapy (DAPT) has become a standard regimen after DES implantation and for fear of very late stent thrombosis, DAPT is frequently performed for 1 year or longer in clinical practice. Especially guidelines recommend 1-year DAPT for patients with acute coronary syndrome (ACS), though its rational is based on the study more than 15 years old. However, serious hemorrhagic complications associated with prolonged DAPT duration can bring disadvantages to patients, and it is extremely important to clarify an optimal DAPT duration after DES procedure. Currently, 1-month DAPT regimen after bare metal stent (BMS) implantation is commonly used in clinical practice, producing no major problems. Based on a meta-analysis of recent clinical studies, it has also been reported that the use of Cobalt-Chromium Everolimus-Eluting Stent (CoCr-EES) reduces the risk of early stent thrombosis by half compared to the use of BMS. There is no necessity to extend antiplatelet therapy after CoCr-EES implantation longer than after BMS implantation, and it is considered possible to use the same 1-month DAPT duration as after BMS implantation. The investigators already planned and started a multicenter, randomized, open-label, controlled study, in which the subjects who have undergone CoCr-EES procedure will be divided into the 1-month DAPT and clopidogrel monotherapy group and the 12-month DAPT and aspirin monotherapy group (STOPDAPT-2; NCT02619760), where primary endpoint is the incidence of composite events including cardiovascular death, myocardial infarction, stent thrombosis, stroke, and bleeding defined by TIMI major or minor bleeding. In STOPDAPT-2, the non-inferiority about primary endpoint of 1-month DAPT group will be evaluated at 12 months after index procedure and secondarily, the superiority about primary endpoint of 1-month DAPT group will be evaluated at 5 years after index procedure. The proportion of patients with ACS is about 30-40% in STOPDAPT-2 and the power is insufficient to evaluate the safety and efficacy of 1-month DAPT regimen specifically for patients with ACS. Therefore the investigators planned the current study to enroll patients of ACS with the same protocol as STOPDAPT-2.