Effects of l-NAME on coronary blood flow, infarct size and the extent of the no-reflow phenomenon

Abstract Background NOS inhibitors are a potential treatment for patients with cardiogenic shock during acute myocardial infarction. Despite hemodynamic efficacy, their effects on the extent of myocardial infarction (MI) and the no-reflow phenomenon (NRP) have not been clarified. Methods Sixteen pigs underwent occlusion of the mid left anterior descending coronary artery for 1h followed by reperfusion for 2h. Coronary blood flow (CBF), distal to the occlusion site, was measured. In eight experiments, l-NAME (non selective NO synthetase inhibitor) administration began 10min before the onset of reperfusion and continued for 2h (loading dose 1mg/kg, perfusion rate: 1mg/kg/h) (l-NAME group). Eight pigs received similarly normal saline (controls). At the end of each experiment, the myocardial area at risk (MAR) and extent of MI and NRP were measured. Results Hemodynamics at baseline and during ischemia were similar in both groups. During reperfusion, the mean aortic blood pressure was significantly higher in the l-NAME group. In both groups, CBF reached a peak at 5min of reperfusion, (no difference between groups). CBF gradually returned to baseline levels within 60min of reperfusion in both groups. No statistically significant differences in the extent of the NRP (51.8±19.7 vs 60.9±11.4 p=0.35) and MI (77.9±13.9 vs 77.1±8.8 p=0.92), both expressed as a percentage of MAR, were observed between the l-NAME group and the control group. Conclusions l-NAME administration started immediately before and maintained throughout reperfusion has no effect on NRP and MI size. l-NAME might stabilize patients with post-MI cardiogenic shock without adverse effects on infarct size.