ECG is a necessary, simple, rapid and non invasive tool for the diagnosis of myocardial infarction and evaluation of myocardial reperfusion that still to be investigated . QT dispersion is a crude and approximate measure of a general abnormality of repolarization; it reflects inhomogeneity of ventricular repolarization . This measurement is an attempt to distinguish between myocardium that is homogeneous from myocardium that displays inhomogeneity, which is accompanied by increased dispersion of the ventricular recovery times and prolongation of repolarization