Normal cardiac excitation originates in the sinoatrial node and travels down to the atria, atrioventricular node, atrioventricular bundles, bilateral bundle branches, and ventricles in a certain order and at a certain time, causing atrial and ventricular excitation. When there is an abnormality in the generation or conduction of excitation, or both, a heart rhythm disorder (arrhythmia) occurs. Arrhythmias can be seen in pediatric patients of all ages. 1, sinus arrhythmia: (1) sinus tachycardia; (2) sinus bradycardia; (3) sinus arrhythmia. 2, premature beat (premature beat); 3, paroxysmal supraventricular tachycardia.