Background Sirolimus-eluting stents (SES) reduce restenosis and revascularization rates, compared with baremetal stents (BMS), in elective percutaneous coronary intervention (PCI). This study investigated the safety and efficacy of SES for emergency PCI in acute coronary syndrome (ACS) patients. Methods and ResultsThe 154 consecutive patients (SES: n=77, BMS: n=77) admitted to hospital with ACS were enrolled in this study. Procedural success (%DS <50%, Thrombolysis In Myocardial Infarction grade 3), major adverse cardiac events (MACE) at 30 days and 8 months, and the incidence of stent thrombosis were evaluated. There was no difference between the groups regarding procedural success. Patients treated with SES had smaller stent diameter (SES 3.04 mm vs BMS 3.24 mm; p=0.01) and longer stent length (25.7 mm vs 21.2 mm; p=0.01). At 30 days, there was no difference between the groups in the incidence of cardiovascular events. At 8 months, patients treated with the SES had a lower rate of repeat PCI (5.6% vs 18.6%; p=0.04) and MACE (9.7% vs 27.1%; p=0.01). Stent thrombosis was no different between groups (1.4% vs 2.9%). Conclusion In emergency PCI for ACS patients, SES implantation significantly reduced cardiovascular events, compared with BMS, by decreasing the incidence of repeat PCI. The safety profile of SES is equal to that of BMS. (Circ J 2008; 72: 1054 -1058