The ECG is more valuable in detecting arrhythmias and heart attacks. The most common ECG is a twelve-lead, four-wave cluster, which needs to be used to diagnose the disease based on the different variations of each wave cluster and the leads to which it belongs. The ECG leads are divided into three limb leads I, II, and III, and three pressurized limb leads avR, avL, and avF, as well as six leads such as chest leads v1, v2, v3, v4, v5, and v6. Each lead can determine the injury in the corresponding orientation of the heart. The ECG is divided into four wave groups: p-wave, qrs wave group, t-wave and u-wave. p-wave reflects atrial depolarization, qrs wave group represents the process of ventricular depolarization, t-wave represents ventricular repolarization, and u-wave is commonly seen in patients with low potassium. The diagnosis of ECG is very complicated and must be made in conjunction with clinical symptoms. Please do not make diagnosis on your own, and seek medical advice immediately if you feel unwell.