Abstract: AIM: To investigate the efficacy and safety of intracoronary( IC) bolus plus intravenous( IV) half-dose maintenance administration of tirofiban in aged patients undergoing primary percutaneous coronary intervention( PCI) for acute myocardial infarction( AMI). METHODS: One hundred and four patients aged 70 years and above undergoing primary PCI for AMI were divided into control group( n = 52)and study group( n = 52). Tirofiban was administered as an intracoronary bolus injection( 10 μg / kg) in all patients followed by maintenance IV infusion at 0. 15 μg /( kg·min) in control group and at 0. 075μg /( kg·min) in study group for 24 h. Complete ST-segment resolution( STR) in STEMI patients,peak concentration of serum high-sensitive cardiac troponin T( hs-c Tn T),scores of thrombus,TIMI flow grade in the infarct-related artery( IRA) and TMI myocardial perfusion grade( TMPG) were analyzed in the two groups. Platelet aggregation in response to adenosine diphosphate( ADP),arachidonic acid( AA) or collagen( COL) was measured with whole blood impedance aggregometry( WBIA) 4 h after tirofiban initiation. Left ventricular ejection fraction( LVEF) and major adverse cardiovascular events( MACEs)were assessed 90 days following PCI. The rates of bleeding and thrombocytopenia were assessed during tirofiban administration. RESULTS: The percentage of patients with complete STR( 84% vs. 86%),peak hs-c Tn T level ( 5. 1 ± 1. 9) μg / L vs.( 5. 8 ± 2. 6) μg / L,scores of thrombus in the IRA( 1. 0 ±0. 5 vs. 1. 1 ± 0. 6),the percentage of patients with TIMI flow score of III( 86% vs. 88%) and TMPG III( 78% vs. 80%) postintervention did not differ significantly between study group and control group.Study group was similar with control group in terms of platelet aggregation in response to ADP ADP( 0. 4 ± 0. 8) Ohms vs.( 0. 2 ± 0. 7) Ohms,AA ( 0. 10 ± 0. 36) Ohms vs.( 0. 06 ± 0. 24) Ohms,COL( 11 ± 5) Ohms vs.( 9 ± 5) Ohms. No significant differences were observed between groups in LVEF( 57 ± 6 vs. 58 ± 68) and composite MACE rate at 90 days after PCI. The total bleeding rate in the study group was lower than in control group( P < 0. 05). Rate of thrombocytopenia was similar between groups. CONCLUSION: Among aged AMI patients undergoing primary PCI,results are similar between half-dose and standard dose maintenance administration of tirofiban in terms of inhibition of platelet aggregation,coronary flow,myocardial perfusion,infarct size,left ventricular systolic function and short-term clinical outcomes,but IC bolus plus intravenous half-dose maintenance administration of tirofiban is superior to standard dose injection in lowering bleeding complications rates.