The cardiac conduction system is composed of the sinoatrial node, atrioventricular node, atrioventricular tachycardia (His bundle), left and right bundle branches and their branches. It is responsible for the function of cardiac pacing and impulse conduction to ensure the coordinated contraction of the atria and ventricles. Impulse conduction can be blocked at any part of the cardiac conduction system. If it occurs between the sinoatrial node and the atrium, it is called sinoatrial block; if it occurs between the atrium and the ventricle, it is called atrioventricular conduction block; if it is located in the atrium, it is called intra-atrial block; if it is located in the ventricle, it is called intraventricular conduction block.