Objective To observe the effect of direct myocardial injection of platelet rich plasma (PRP) on cardiac function,ventricular remodeling and myocardial perfusion.Methods Myocardial infarction was induced in 30 Fisher rats by left anterior descending coronary artery (LAD) ligation.One week after LAD ligation,rats in control group (n =15) received 0.5 ml saline myocardial injection and rats in PRP group (n =11 ) received 0.5 ml PRP myocardial injection.99Tcm-methoxyisobutylisonitrile (MIBI)gated single photon-emission computed tomography (SPECT) imaging was applied at 1 week post LAD ligation and prior myocardial saline/PRP injection and repeated at 4 week post LAD ligation to assess myocardial perfusion and ejection fraction (EF),left ventricular end-diastolic volume ( LVEDV ),left ventricular end-systolic volume ( LVESV ),and the number of infarct segments.Results EF remained unchanged between 1 and 4 weeks post LAD ligation in control group and was significantly higher at 4 weeks post LAD ligation than at 1 week post LAD ligation in PRP group ( P ＜ 0.05 ).LVESV was significantly increased in the control group ( P ＜ 0.05 ) while remained unchanged in the PAP group ( P ＜ 0.05 ) at 4 weeks post LAD ligation compared that at 1 week post LAD ligation.LVEDV remained unchanged in the control group (P＞0.05) and significantly increased in the PRP group (P＜0.05) from 1 week to 4 weeks post LAD ligation.Myocardial perfusion remained unchanged in the control group and significantly improved in the PRP group at 4 week post LAD ligations.Histological examination also confirmed that PRP treatment can decrease infarct size [from (47 ± 19)％ to (36 ± 11 )％ ],increase ventricular wall thickness [ from (3.1 ± 0.9 )mm to ( 4.6 ± 1.8 ) mm ] ( P ＜ 0.05 ).Conclusion Myocardial PRP injection could improve cardiac function and reperfusion in this rat model of acute myocardial infarction.