Objective To investigate the effects of distal thrombolysis versus thrombus aspiration on myocardial perf usion and prognosis in patients with acute ST segment elevation myocardial infarction(AMI)during emergency percutaneous coronary intervention(PCI). Methods 96 patients with acute ST segment elevation myocardial infarction(onset<6 hours)were randomly divided into thrombolysis group and distal thrombus aspiration group. Patients in the distal thrombolysis group(n=46)received transcatheter urokinase injection to the occlusive segment followed by balloon dilatation or stenting. Patients in the thrombus aspiration group(n=50)were given thrombus aspiration after balloon angioplasty or stenting. Patients were followed up for 30 days after operation. The coronary blood flow and myocardial perfusion were compared between the 2 groups. The incidence of major adverse cardiac events(MACE)and left ventricular systolic function after 30 days were compared. Results There was 1 case in the distal thrombolysis group (0.2%)and 6 case in the thrombus aspiration group(12%)presented with TIMI fl ow≤grade Ⅱ(P=0.008). A 65.2% of patients in the distal thrombolysis and 42.0% of patients in the thrombus aspiration group achieved > 50% of ST segment resolution in 2 hours(P=0.019). At 30-day follow up,the LVEF was found higher in the thrombolysis group compared with the aspiration group(54.1±8.6)% vs.(50.8±7.3)%,P=0.047 but the LVEDD(44.3±7.2)mm vs.(46.5±6.8)mm,P=0.038 and NT-proBNP levels(117.8±71.8)μg/L vs.(161.2±72.3)μg/L,P=0.025 were found significantly lower in the thrombolysis group. Conclusions For the ST segment elevation myocardial infarction,distal thrombolysis,when compared with thrombus aspiration,may reduce the incidence of slow flow and no reflow,and may improve the left ventricular systolic function.