Objective: To determine and compare the incidence of in-hospital and 30-day hemorrhagic complications and major adverse cardiac events (MACEs) as evidence of safety and efficacy using Bivalirudin versus Heparin in diabetic acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI) in a tertiary care cardiac hospital. Background: Prevention of hemorrhagic complications has emerged as a priority in patients undergoing PCI in addition to suppressing thrombotic complications. This goal is challenging to achieve in diabetic ACS patients as DM itself is a prothrombotic state with more pronounced vascular injury response and have a worse outcome after PCI compared with non-diabetic patients. In patients with ACS, Bivalirudin has been shown to result in similar rates of composite ischemia as Heparin plus GPI (GP IIb /IIIa inhibitor), while significantly reducing major bleeding and has received class I recommendation for PCI. Whether Bivalirudin is safe and effective in diabetic ACS patients undergoing PCI, as compared with Heparin (UFH) monotherapy, is unknown. Methods: 218 diabetic ACS patients (age>18 years and ≤ 75 years) who underwent PCI from May 2018 to April 2019 at UCC, BSMMU, Dhaka, Bangladesh were randomly assigned to have UFH or Bivalirudin. Before the guide wire crossed the lesion, 111 patients in the UFH group received a bolus of 70-100 U/kg (targeted activated clotting time, ACT: 200-250 s). 107 patients in the Bivalirudin group received a loading dose of 0.75 mg/kg, followed by an infusion of 1.75 mg/kg/h for up to 4 hours. Dual antiplatelet (DAPT) loading as Aspirin 300 mg plus P2Y12 inhibitors (Clopidogrel 600 mg or Prasugrel 60 mg or Ticagrelor 180 mg) was given in all patients before the procedure. The maintenance dose of DAPT was continued for at least one month and patients were followed telephonically up to 30 days. The outcome measures were in-hospital and 30-day hemorrhagic complications and MACEs [death, MI, target vessel revascularization (TVR) and stroke]. Results: Patients treated with Bivalirudin compared with Heparin had a significantly lower in-hospital incidence of QMI (0% vs. 6%; p=0.03) and major bleeding (0% vs. 7%; p=0.02). However, the incidence of cardiac death, stent thrombosis, TVR were no differences between the groups (p>0.05). There was only one NQMI in the Bivalirudin group as opposed to 8% in the Heparin group in 30 days following stenting (p=0.04). No other adverse effects were found significantly different between groups in 30 days of PCI. Conclusion: In this small scale, prospective, randomized controlled study of diabetic ACS patients undergoing PCI in a single center showed that Bivalirudin is safe and effective as it reduces immediate and short-term hemorrhagic complications as well as MACEs as compared with Heparin.