Objectives: Coronary wedge pressure(Pcw) of infarct-related artery(IRA) assessed after successful percutaneous coronary intervention(PCI) of AMI might be related to the severity of microvascular damage of infarct related myocardium. However, it was not clearly defined. Methods: Study population was consisted of 20 patients with first AMI(age: 57짹14, male: 19 patients, IRA(LAD:11, LCx:3, RCA:6)). After successful PCI, TIMI flow grade and TIMI myocardial perfusion grade(TMP grade) were assessed. We measured coronary flow velocity by intracotonary(IC) Doppler wire for assessing coronary flow reserve(CFR) and deceleration time of diastolic flow velocity(DDT) and Pcw by IC pressure wire. We compared Pcw and Pcw/Pa(mean aortic pressure) with phasic coronary flow velocity indexes and patterns. Results: After PCI, 60.0% of patients achieved TMP 0 and TMP 1 grade and 40.0% of patients achieved TMP 2 grade and 0.0% achieved TMP 3 grade. Pcw and Pcw/Pa were significantly higher in TMP 0 or 1 compare to TMP 2 grade(26.8짹5.6 mmHg vs. 19.9짹2.8, p=0.004; 0.29짹0.06 vs. 0.22짹0.04, p=0.016, respectively). There was significant correlation between TMP grade and Pcw(r=-0.686, p=0.001) and Pcw/Pa(r=-0.522, p=0.012). Pcw and Pcw/Pa were significantly correlation with coronary flow velocity indexes and patterns(Table). The best cutoff values of Pcw and Pcw/Pa for bDDT 600msec were 24mmHg(sensitivity:81.8%, specificity:88.9%, AUC:0.939) and 0.2(sensitivity:100%, specificity:77.8%, AUC:0.934). Conclusion: Pcw of IRA was correlated with DDT and CFR measured after PCI and might be represent the severity of microvascular damage of infarct-related myocardium.