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Objectives The long-term benefit of late reperfusion of infarct-related artery (IRA) after acute myocardial infarction (AMI) is controversial, and the benefit mechanisms remain uncertain. Low dose dobutamine stress echocardiography (LDSE) can identify viable myocardium and predict improvement of wall motion after revascularization. Methods Sixtynine patients with first AMI who did not received early reperfusion therapy were studied by LDSE at 5 to 10 days after AMI. Wall motion abnormality and left ventricular size were measured at the same time.Successful PCI were done in all patients at 10 to 21 days after AMI onset. Patients were divided in two groups based on the presence or absence of viable myocardium. Echocardiography was repeated six months later. Results There were 157 motion abnormality segments. 89 segments (57%) were viable during LDSE. 26 patients (38%) with viability and 43(62%) without. In viable group, left ventricular ejection fraction (LVEF) was increased (P＜0.05),and left ventricular end systolic volume index (LVESVI) and wall motion score (WMS) were decreased (P＜0.05 and P＜0.01) significantly at 6 months compared with baseline. But in patients without viability, LVEF was decreased (P＜0.01), and LVESVI and left ventricular end diastolic volume index (LVEDVI) were increased (P＜0.05) significantly after 6 months, and the WMS did not changed (P＞0.05). LVEF increased (P＜0.05) and WMS decreased (P＜0.05) on LDSE during acute phase in patients with viability, but they were not changed in the nonviable group. Conclusions Late revascularization of IRA in patients with presence of viable myocardium after AMI is associated with long-term preservation left ventricular function and less ventricular remodeling.Improvement of left ventricular systolic function on LDSE indicates late phase recovery of left ventricular function after late revascularization.