The ECG has 12 leads, including I, II, and III standard limb leads, as well as aVR, aVL, and aVF pressurized limb leads, and also includes V1-V6 chest leads. Normally, these leads of the ECG are used to check the human heart for abnormalities by means of 4 clips and 6 balls. In special cases, an 18-lead ECG is required. 4 clips reflect the limb leads, which usually have 4 colors: red, black, yellow and green. The red clip should be clamped at the patient’s right upper limb wrist, the black clip at the patient’s right lower limb ankle, the yellow is clamped at the left upper limb wrist, and the green is clamped at the left lower limb ankle. The thoracic leads are mainly used to collect ECG information from the patient by means of 6 different colored balls that can be attached to the human skin and fixed to the patient’s chest position. Usually lead V1 should be located at the 4th intercostal space on the right edge of the sternum, lead V2 at the 4th intercostal space on the left edge of the sternum, lead V4 at the junction of the left midclavicular line and the 5th intercostal space, lead V3 at the midpoint of the line connecting leads V2 and V4. lead V5 is in the left anterior axillary line and is at the same level as lead V4, and lead V6 is in the left midaxillary line and is at the same level as lead V4. Only by placing these markers of the patient’s limb leads and chest leads in the correct position can they reflect the patient’s true ECG performance and help determine whether the patient has cardiogenic disease. In addition, if the patient is suspected of having right ventricular and posterior wall myocardial infarction, an 18-lead ECG is required, which requires the addition of leads V7, V8, V9, V3R, V4R, and V5R to the original 12-lead ECG. The V7 leads are located in the posterior axillary line, at the same level as V4. The V8 leads are located in the posterior scapular line, at the same level as V7. The V9 leads are in the left parasternal spine, at the same level as V7. The V3R, V4R, and V5R leads are all in the right chest, in positions corresponding to V3, V4, and V5.