Abstract: AIM: To study the time-related changes of matrix metalloproteinases (MMPs) and the relationship between MMPs and left ventricular (LV) remodeling in patients with non-ST-elevation myocardial infarction (NSTEMI) treated with early percutaneous coronary intervention (PCI). METHODS: A 12-month follow-up was conducted in 126 NSTEMI patients treated with early PCI. Plasma MMP-2 and MMP-9 were assayed at intervals (2 days, 4 days, 2 weeks and 4 weeks) in NSTEMI patients. The serial changes of LVEDV and LVEF were measured by echocardiography at baseline and 12 months, and the relationship between MMP-2, -9 and LVEDV and LVEF after NSTEMI was analyzed. RESULTS: MMP-2 concentrations substantially increased throughout the post-MI 2 weeks and then began to drop. MMP-9 concentration increased at 2 and 4 days after MI and dropped subsequently. MMP-9 concentration at 2 days after MI was positively correlated with ΔLVEDV (r＝0.350, P=0.028) and MMP-9 concentration at 4 days after MI was positively correlated with ΔLVEDV (r＝0.402, P=0.000) and ΔLVEF (r＝0.333, P=0.040). MMP-2 concentrations at 2 weeks and 4 weeks after MI were positively correlated with ΔLVEDV (2 weeks, r＝0.378, P=0.010; 4 weeks, r＝0.331, P=0.041) and ΔLVEF (2 weeks, r＝0.501, P=0.000; 4 weeks, r＝0.367, P=0.014). CONCLUSIONS: Plasma MMP-9 concentrations at 4 days after NSTEMI and MMP-2 concentrations at 2 weeks and 4 weeks after NSTEMI are correlated with LV remodeling.