Abstract: Objective： To study the changes of peripheral venous blood concentration of myeloperoxidase (MPO) in patients with acute myocardial infarction(AMI), unstable angina pectoris(UAP) and stable angina pectoris(SAP). Methods： 91 patients subjected to coronary angiography, including 19 patients in the AMI group, 30 in the UAP group, 22 in the SAP group and 20 in the control group, were determined the concentrations of MPO and high-sensitivity C-reactive protein (hsCRP) in the femoral vein. The ultra-structure of leukocytes was observed by an transmission electron mirror. Results： The in-gate percentage of MPO in the femoral vein was higher in the UAP group than in the AMI, the SAP and the control groups (P＜0.05, respectively), and there were no differences between the later three groups. The average fluoescent intensity of MPO in the femoral vein was obviously weakened in the AMI group than in the UAP, the SAP and the control groups (P＜0.05, respectively), and still there were no differences between the later three groups. Compared with the control group, concentrations of hsCRP in the UAP and the AMI groups were significantly increased, but no difference existed between the UAP and the AMI groups or between the SAP and the control groups. In the UAP group, patients with type II lesion showed a higher in-gate percentage of MPO (P＜0.05) and a high concentration of hsCRP (P＜0.05) than those with type I lesion. Through an electron mirror, few vacuoles were found in the cytoplasm of the neutrophil in the control group, less particles and more vacuoles in the AMI group, and abundant particles and very few vacuoles in the UAP group. Conclusion: Different changes of MPO between patients with AMI and UAP can not only predict ACS but also reflect the severity of inflammation.

Key words: Myeloperoxidase, Neutrophil, Acute coronary syndrome, High-sensitivity C-reactive protein