Impairment of the myocardial microcirculation in the setting of AMI is multifactorial in etiology. This may be due to vasoactive factors including endothelin-1, which is a potent vasoconstricting peptide and increasingly expressed in the active plaque . Oxidative stress and ischaemia per se may also reduce the bioavailability of nitric oxide, further contributing to the dysfunction of the myocardial microcirculation.