Myeloperoxidase Is Not Useful for Detecting Stress Inducible Myocardial Ischemia but May Be Indicative of the Severity of Coronary Artery Disease

Background and Objectives: Elevated levels of myeloperoxidase (MPO) have been found in patients in different stages of coronary artery disease (CAD). The aim of this study was to assess whether the MPO liberation is increased by stress inducible myocardial ischemia and could be used to improve the diagnostic accuracy of non-invasive evaluation for myocardial ischemia. Subjects and Methods: Seventy-six patients with suspected myocardial ischemia who underwent stress myocardial perfusion scintigraphy (MPS) were enrolled. 59 patients with an acute coronary syndrome (ACS) who received a percutaneous coronary intervention along with 12 healthy volunteers were also included in the study. In every subject the MPO plasma levels were assessed by enzyme linked immunosorbent assay. In patients undergoing MPS, the MPO levels were measured serially before and after the stress testing. Results: Of the 76 patients undergoing MPS, 38 were diagnosed with a stress inducible myocardial ischemia. The patients with a stress induced ischemia had significantly higher basal MPO levels than those without it ($32{\pm}3ng/mL$ vs. $24{\pm}4ng/mL$, p=0.03). However, there was no relevant change in the MPO levels after the stress test compared to the baseline. The patients with ACS showed significantly higher MPO levels than the patients undergoing MPS ($131{\pm}14ng/mL$ vs. $28{\pm}2ng/mL$, p<0.01) and the healthy subjects ($131{\pm}14ng/mL$ vs. $26{\pm}2ng/mL$, p<0.01). Conclusion: Since the MPO plasma levels did not increase after the stress MPS, MPO appears not to be a useful biomarker for detecting a stress inducible myocardial ischemia. Yet, the MPO levels correlate with the different stages of CAD and may hold significance as an indicator for its clinical severity.