To check the ECG, the patient sits still for fifteen minutes, then lies flat on the bed, exposing the anterior chest and wrists and ankles, and the doctor connects the corresponding leads to the patient. The order of the leads is usually the left upper limb connected to the yellow lead, the right upper limb connected to the red limb lead, the right lower limb connected to the black limb lead, and the left lower limb connected to the green limb lead. The order of thoracic lead connection is: the right edge of the sternum in the 4th rib gap is connected to V1 thoracic lead, the left edge of the sternum in the 4th rib gap is connected to V2 thoracic lead, V3 thoracic lead is located between V2 lead and V4 lead, the left midclavicular line in the 5th rib gap is connected to thoracic lead V4, the left anterior axillary line in the 5th rib gap is connected to thoracic lead V5, the left midaxillary line in the 5th rib gap is connected to thoracic lead V6, the connection is completed. The patient relaxes his mind to make the ECG.