Normal ECG results show that: 1) heart rate fluctuates from 60-100 beats/min, below 60 beats/min is bradycardia, above 100 beats/min is tachycardia; 2) heart rhythm is uniform; 3) electrocardiographic axis is not biased or slightly left biased; 4) main wave direction is upward in leads V1-V6, I, aVR, aVL, and downward in lead aVF; 5) P waves exist and the direction is regular; 6) P waves are followed by QRS waves. QRS wave group followed by P wave, P-R interval is 0.12-0.20s, QRS interval is usually 0.06-0.08s; 7, T wave direction is consistent with the main wave direction; 8, R wave in V1-V6 leads gradually increases, that is, R wave in V1 leads