Abstract 3934: Elevated Levels of Plasma Myeloperoxidase are Associated with Impaired Myocardial Microcirculation after Reperfusion in Patients with Acute Myocardial Infarction.
Previous studies have shown that oxidative stress and endothelial dysfunction are related to impaired myocardial microcirculation after reperfusion. Myeloperoxidase (MPO) is a leukocyte-derived enzyme that catalyzes the formation of reactive oxidant species. In addition, elevated MPO levels are associated with endothelial dysfunction. In this study, we investigated whether plasma MPO levels on admission are related to impaired myocardial microcirculation as indicated by ST-segment resolution, myocardial blush grade, and left ventricular ejection fraction (LVEF) at 6 months. Moreover, we investigated the presence of MPO-positive cells in infarcted myocardium in autopsied patients with acute myocardial infarction (AMI). Plasma MPO levels were measured in patients with ST-segment elevation AMI (n=162) who underwent primary angioplasty within 12 hours of symptom onset. Patients were divided into 2 groups according to the median MPO value for the entire cohort (low-MPO group≤50ng/ml, n=81; and high-MPO, group>50ng/ml, n=81). Frozen samples from 9 autopsied AMI patients were immunohistochemically stained with antibodies against macrophages, endothelial cells, neutrophils, and MPO. The magnitude of impaired myocardial microcirculation after reperfusion evaluated by ST-segment resolution and myocardial blush grade was significantly reduced in the low-MPO group compared with the high-MPO group (61±24 vs. 48±27%, P<0.005; 2.4±0.7 vs. 2.1±0.8, P<0.01; respectively), while the numbers of white blood cells, neutrophils and C-reactive protein levels were not significantly different between the two groups. LVEF at 6 months was significantly higher in the low-MPO group compared with the high-MPO group (54±9 vs. 46±9%, P<0.0001). Multiple regression analysis showed that elevated plasma MPO level on admission was an independent predictor of incomplete ST-segment resolution (OR, 5.17; 95%CI, 1.33 to 20.12; P=0.018). Immunohistochemical staining showed abundant MPO-positive neutrophils in infarcted myocardium. These findings suggest that elevated plasma MPO levels on admission are associated with impaired myocardial microcirculation following reperfusion in AMI patients.