ST segment changes on the ECG are generally often indicative of myocardial ischemia and, depending on the variant, can help to diagnose coronary heart disease, angina pectoris, myocardial infarction, and other conditions of varying degrees of severity. The formation of ST segment on ECG actually refers to the slow and rapid repolarization process of the ventricle after the completion of myocardial depolarization, and this process forms the ST and T segments. In clinical myocardial ischemia, the electrocardiogram may show only ST-segment changes or T-wave changes, but of course, ST-T changes can also occur at the same time. ST segment abnormalities are usually seen in patients with coronary artery disease without angina, while in patients with coronary artery disease during angina attacks, the ECG may be normal or only have mild ST-T changes; in a typical angina attack, the ischemic area may show ST segment depression (horizontal or downward-sloping downward shift of ≥0.1mV) and/or T-wave inversion. In addition, certain episodes of angina pectoris present with worsening or spurious improvement in ST-T changes; in the myocardial infarction population, inverted, deep-pointed, bilaterally symmetrical T waves are often seen on the ECG. Therefore, when examination reveals ST-segment changes on the ECG, prompt compliance with further examination, and treatment and intervention as prescribed by the physician is required.