Relation of Elevated Levels of Plasma Myeloperoxidase to 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. Moreover, elevated myeloperoxidase (MPO) levels are associated with endothelial dysfunction. Plasma MPO levels were measured in patients with ST-segment elevation acute myocardial infarction (n = 160) who had undergone percutaneous coronary stenting within 12 hours of symptom onset. We investigated whether the plasma MPO level at admission was associated with impaired myocardial microcirculation, as indicated by ST-segment resolution and myocardial blush grade after reperfusion, and left ventricular ejection fraction and remodeling at 6 months. The patients were divided into 2 groups according to the median MPO value for the entire cohort (low-MPO group ≤50 ng/ml, n = 80; high-MPO group >50 ng/ml, n = 80). ST-segment resolution and the myocardial blush grade were significantly lower in the high-MPO than in the low-MPO group (48 ± 27% vs 61 ± 24%, p <0.005; and 2.1 ± 0.8 vs 2.4 ± 0.7, p <0.01; respectively). Moreover, the percentage of increase in the left ventricular end-diastolic volume index was significantly greater and the left ventricular ejection fraction at 6 months was significantly lower in the high-MPO group than in the low-MPO group (8.2 ± 24.7% vs −1.9 ± 23.5%, p <0.05; and 46 ± 9% vs 54 ± 9%, p <0.0001, respectively). Multiple regression analysis showed that the plasma MPO level was an independent predictor of incomplete ST-segment resolution (odds ratio 6.94, 95% confidence interval 2.10 to 22.9, p = 0.0015). In conclusion, elevated plasma MPO levels at admission were associated with impaired myocardial microcirculation after reperfusion in patients with acute myocardial infarction.