Objective: To evaluate the effects of anti-platelet drugs on myocardial no-reflow after acute myocardial infarction (AMI) and reperfusion.
Methods: Thirty-two mini-swine were randomized into 4 equal groups: Control Group, without any intervention; Group A approximately C, pretreated with aspirin-clopidogrel (A-C) combination (300 mg loading dose followed by 75 mg per day of clopidogrel and 10 mg x kg(-1) x d(-1) of aspirin for 3 days), Group Tirofiban, given an intravenous infusion of tirofiban (15 microg/kg in intravenous bolus followed by 0.5 microg x kg(-1) x min(-1) in continuous intravenous infusion from 30 min before occlusion to the end of protocol; and Sham Operation Group, undergoing sham operation. The former 3 groups underwent three-hour occlusion of the left anterior descending (LAD) coronary artery followed by one-hour reperfusion Before the adminisfration of drngs and hefore lipation of LAD flood sanpks were collocfed to detoif the platelet aggregation rate (PAR). Hemodynamic examination and myocardial contrast echocardiography (MCE) were performed before AMI, 3 h after AMI, and 1 h after reperfusion. The coronary ligation area (LA) and area of no-reflow (ANR) were determined with both MCE in vivo and pathological examination after the swine were killed.
Results: The platelet aggregation rates (MAR) after AMI were 46.8% and 45.7% respectively in tirofiban group and A-C Combination group, and significantly decreased to 12.9% and 14.3% respectively after the administration of drugs (both P < 0.01) with equivalent potency (P > 0.05). The left ventricular function was significantly improved in tirofiban group in comparison with control group (P < 0.05 - 0.01), the coronary blood flow volume (CBV) 1 h after reperfusion was 73.2% in tirofiban group, significantly higher than that of control group (45.8%, P < 0.01), and the ANR of tirofiban group was 22.8% and 23.2% judged by MCE and pathological examination respectively, both significantly smaller than those of control group (78.5% and 82.3%, both P < 0.01), and the NA of tirofiban group was 89.2%, significantly smaller than that of Control Group (98.5%, P < 0.05). However, there were not significant differences in left ventricular function, central blood volume, ANR and NA between A-C combination group and control group (all P > 0.05).
Conclusion: Tirofiban is markedly effective in attenuating myocardial no-reflow after reperfusion; in contrast, A-C combination is totally ineffective.