The ECG generally shows P waves, PR intervals, QRS waves, ST segments, and T waves. 1. The P-wave represents the potential change of atrial depolarization. The time limit of the P-wave does not exceed 0.12 seconds, and the height of the P-wave generally does not exceed 0.25 millivolt. 2. The normal PR interval is generally around 0.12-0.20 seconds, and is slightly prolonged in the elderly, generally not exceeding 0.22 seconds. 3. The QRS wave group represents the potential change of ventricular muscle depolarization, which normally does not exceed 0.11 seconds in normal people. 4. Under normal circumstances, the ST segment should be on the isoelectric line, and the T wave should be in the same direction as the main wave of the QRS wave. Sometimes it can be slightly shifted, and the downward shift usually does not exceed 0.05 mV. 5. The normal QT interval is usually 0.32 seconds – 0.44 seconds. Each person’s ECG will generally show a different state. The specific situation, you need to go to the regular hospital to see the electrocardiogram specialist or cardiologist according to their own situation to understand