Myocardial ischemia is a manifestation of coronary artery disease and can be diagnosed by electrocardiogram, looking at the ST segment and T wave of the electrocardiogram. There are two types of myocardial ischemia, endocardial ischemia as well as epicardial ischemia. In case of epicardial ischemia, it is manifested by ST-segment elevation and T-wave inversion. T-wave inversion is called coronal T-wave, which means that the descending and ascending limbs of T-wave inversion are symmetrical changes in both limbs. For endocardial ischemia, ST-segment depression and low T-wave values are demonstrated. The most common forms of ST-segment depression are horizontal, downward-sloping and downward-sloping. Acute ischemia manifests as horizontal type prolongation of the ST segment. Myocardial ischemia affects ventricular repolarization and manifests ventricular repolarization waves, i.e., prolonged or shortened QT intervals. The treatment is carried out in conjunction with the severity of the patient’s condition and the degree of ST-segment depression and elevation. If the depression is severe or the symptoms do not resolve, urgent management treatment is required according to the procedure for patients with chest pain.