The typical ECG features during an angina pain episode are as follows: 1. A transient ischemic ST-segment parallel downward shift or low hanging downward shift occurs, the limb leads show a non-conforming ST-segment shift, STl shows an ischemic downward shift, STll shows an upward shift, and the ST-segment in the thoracic leads shows an ischemic downward shift more obviously. 2. A transient T-wave change occurs, often showing a low, inverted T-wave in the thoracic leads. 3. 3. transient myocardial infarction patterns appear, which can disappear after effective treatment. 4. transient U-wave inversion in the thoracic leads, accompanied by prolonged QT interval, sinus tachycardia or sinus bradycardia. 5. transient arrhythmias appear, manifested as atrial premature beats, ventricular premature, atrial fibrillation, atrioventricular block, bundle branch block, etc. 6. Sometimes a transient electrical axis or potential change occurs.