Low st-segment depression in leads II, III, and avF may be caused by myocardial ischemia in the lower wall of the heart, or it may be caused by abnormal myocardial repolarization. II, III, avF leads in the electrocardiogram represents the location of the lower wall of the heart, st-segment depression is generally a manifestation of myocardial ischemia, myocardial infarction in the lower wall of the heart often occurs in the three leads of the st-segment depression, usually caused by the right coronary artery of the heart lesions. Causes of right coronary artery lesions are: atherosclerosis; vascular infectious diseases; autoimmune or inflammatory response; hypertension, hyperlipidemia, etc. can cause right coronary artery blockage, resulting in myocardial ischemia. If it is myocardial repolarization abnormalities caused by the II, III, avF lead st segment depression need to be further examination to determine. When there is an abnormal ECG examination, it is recommended to go to the hospital to clarify the cause of the disease, so as to avoid adverse effects.