Nevertheless, there have been no evidence in clinical setting of acute myocardial infarction (AMI). Since about 30-50% of patients with AMI possess multivessel disease, the ability to accurately assess the functional significance of non-IRA stenoses at the time of initial primary PCI would potentially facilitate revascularization decisions with potential for health and economic benefit. Moreover, avoiding unnecessary stent implantation for non-IRA stenoses in patients with AMI with multivessel disease would reduce the possibility of stent- or procedure related complications, and enhance long-term prognosis of patients.