Objective: The aim of this study was to investigate the changes in early and late washout rates of 99mTc-methoxyisobutylisonitrile (MIBI) in ischemic myocardium and its clinical value in evaluating dysfunction of ischemia heart disease (IHD).Methods: Sixteen patients (ten males, six females; mean age, 62.50±6.95 years) who were clinically diagnosed as IHD with three-vessel stenosis (> 50%) according to coronary angiography (CAG) results, among whom myocardial infarction patients were excluded,underwent 99mTc-MIBI static planar and gated single-photon emission computed tomography (SPECT) imaging.In the planar imaging the left ventricular myocardium contour was considered to be the region of interest (ROI).The ROIs with the same area were drawn on the 10 min later,90 min later, and 4 h later anterior static planar images of each participant.The same imaging was performed on control participants (five males, five females; mean age, 55.70±10.42 years).The early and late washout rates of 99mTc-MIBI were calculated by equations and left ventricular ejection fraction (LVEF) were measured by gated SPECT imaging, which were compared between IHD group and normal control group.Linear correlation analysis was made between early and late washout rates and LVEF.Results: Statistically lower early washout rate of 99mTc-MIBI was observed in the IHD group than the control group [(13.44±2.87) % vs (17.32±4.92) %, p<0.05], but statistically higher late washout rate of 99mTc-MIBI was observed in the IHD group than the control group [(19.24±4.71)% vs (15.23±3.81)%, p<0.05].Moreover, LVEF in the IHD group was significantly lower than the control group [(55.71±7.97) % vs (67.75±5.43) %, p<0.01]; There are no correlations between the early and late washout rates and LVEF(r=-0.212, p>0.05; r=0.352, p>0.05, respectively).Conclusion: 99mTc-MIBI late washout rate may reflect myocardium impairment due to ischemia;it may be helpful to discriminate three-vessel stenosis from IHD patients whose myocardial perfusion imaging show normal.