There are many common ECG changes, such as small P waves, ST-segment oblique elevation, and QRS wave cluster changes. In addition, rhythm abnormalities are also common ECG changes and can cause various types of arrhythmias. 1. Small P-wave: In children, the P-wave may be sharp due to the position of the body and the location of the point of agitation. When the P-wave is low or mildly inverted in leads III and AVF, it is not abnormal as long as the P-wave in lead I is upright and the P-wave in lead AVR is inverted. 2. Oblique elevation of ST segment: In some athletes, a marked elevation of ST segment or early repolarization syndrome can be found during ECG examination. 3. QRS wave group changes: P-wave amplitude increases on the ECG, and QRS wave group changes with increased wave group voltage, which can reach the standard of left or right ventricular hypertrophy. ECG abnormalities may also have other conditions, it is recommended to go to the hospital in a timely manner, improve the examination to determine the cause of the disease, under the guidance of the doctor to give targeted treatment or therapy.