Background:Despite its limitations,unfractionated heparin (UFH) has been the standard anticoagulant used during percutaneous coronary intervention (PCI).This study compared the safety of low-dose UFH with sequential enoxaparin with that of UFH in patients with diabetes mellitus (DM) and complex coronary artery disease receiving elective PCI.Methods:In this retrospective study,514 consecutive patients with atherosclerotic cardiovascular diseases and type 2 DM were admitted to the hospital and received selective PCI,from January 2013 to December 2015.All patients with PCI received low-dose UFH with enoxaparin (intraductal 50 U/kg UFH and 0.75 mg/kg enoxaparin,n =254;UFH-Enox group) or UFH only (intraductal 100 U/kg UFH,n =260;UFH group).The study endpoints were major adverse cardiac events (MACEs),namely death,myocardial infarction (MI),stroke,target-vessel immediate revascularization (TVR),and thrombolysis in MI (TIMI) major bleeding,within 30 days and 1 year after PCI.Any catheter thrombosis during the procedure was recorded.Results:Only one patient had an intraductal thrombus in the UEH group.At the 30-day follow-up,no MACE occurred in any group;seven and five cases of recurrent angina and/or rehospitalization were reported in the UFH-Enox and UFH groups,respectively;there was no significant difference between the two groups (x2=0.11,P =0.77).There was no TIMI major bleeding in the groups.With respect to the l-year endpoint,two cases of recurrent MI and two of TVRs were reported in the UFH-Enox group,whereas in the UFH group,one case of recurrent MI and three of TVRs were reported;no significant difference existed between the two groups (x2=0,P =0.99).There were 30 and 25 recurrent angina and/or rehospitalizations in the UFH-Enox and UFH groups,respectively;there was no significant difference between the two groups (x2=0.37,P =0.57).Conclusion:In elective PCI,low-dose UFH with sequential enoxaparin has similar effects and safety to the UFH-only method.