BACKGROUND AND OBJECTIVES: As lack of myocardial perfusion was demonstrated Microvascular function after reperfusion of infarct related artery (IRA) can be changed in convalescent stage for several possible mechanisms such as hyperemia and microvascular stunning. Therefore, myocardial contrast echocardiography (MCE) performed early stage after reperfusion of IRA may cause over or underestimation of the extent of myocardial necrosis. The aims of the study were to demonstrate the temporal changes of myocardial perfusion after revascularization of IRA and to explore the association of late changes of myocardial capillary flow with contractile recovery. METHODS: MCE was performed 5-7days after the attack of acute myocardial infarction (AMI) in 21 patients (M:F=17:4, age: 58+/-12yrs) who underwent successful reperfusion of IRA. MCE was graded by semiquantitative score (0: no opacification, 0.5: partial opacification, 1: homogenous opacification) by 16 segment model. Every patient underwent 1-2months follow up 2D echocardiography and MCE. Improvement of wall motion score more than 1 at follow up was considered to have contractile recovery. RESULTS: Thirty-one of 71 initially akinetic segments were scored as 1, 30 segments as 0.5 and 10 segments as 0 after attempted reperfusion. Twelve of 30 segments with score of 0.5 and 5 of 10 segments with score of 0 showed late improvement of MCE score to 1 and 0.5. Only 1 of 30 segments with score of 0.5 got worse to score of 0. Every segment with late improvement from 0.5 to 1 showed contractile recovery, whereas none of 5 segments with late improvement from 0 to 0.5 showed contractile recovery. There was no significant difference of predictive value between early and late MCE (p=ns). CONCLUSION: Temporal changes of myocardial perfusion from 1week to 2 months in AMI were mainly progressive improvement caused by recovery of microvascular function from stunning rather than progressive microvascular damage or reactive hyperemia. However, it may not significantly affect the validity of MCE in predicting contractile recovery.