Background: Preserved microvascular integrity would favorably influent to left ventricular (LV) functional improvement in ST-segment elevation myocardial infarction (STEMI). We evaluated the usefulness of integrated approach of microvascular integrity indexes in the prediction of LV functional changes in STEMI by using coronary flow velocities and intracoronary (IC) pressures measured after primary percutaneous coronary intervention. Methods: Using an IC Doppler and pressure wire, coronary flow reserve (CFR), hyperemic microvascular resistance index (MVRI) and coronary wedge pressure (Pcw)/mean aortic pressure (Pa) were evaluated in 76 patients with first STEMI received primary PCI within 24 hours after onset of symptoms. Follow-up echocardiography was performed at 6 짹 2 months. Results: CFR, MVRI and Pcw/Pa had significant correlations with LV wall motion score index (WMSI) at follow-up echocardiography (r = -0.420, p<0.001; r = 0.486, p<0.001; r = -0.454, p<0.001, respectively). Using receiver-operating characteristics analysis, CFR���1.5 (sensitivity: 71%, specificity: 67%, area under the curve (AUC): 0.687), MVRI���2.55 (sensitivity: 68%, specificity: 67%, AUC: 0.721) and Pcw/Pa��� 0.28 (sensitivity: 79%, specificity: 58%, AUC 0.695) were the best cutoff values in prediction of aggravated WMSI. In patients with CFR���1.5, MVRI���2.55, and Pcw/Pa>0.28 aggravated follow-up WMSI were occurred in 10 patients (62.5%) of 16 patients, whereas aggravated follow-up WMSI were occurred only in 4 patients (17.4%) of 23 patients with CFR > 1.6, MVRI < 2.55, and Pcw/Pa < 0.28 (p=0.030)(Table). Conclusion: Integrated approach of microvascular integrity indexes by using CFR, MVRI and Pcw/Pa was useful in the prediction of long-term LV functional changes in STEMI patients.