Third-degree atrioventricular block, also clinically called complete manner conduction block, is a serious cardiac arrhythmia that is a severe form of slow heartbeat and requires aggressive treatment. It can usually be categorized as transient or permanent depending on the cause. If the cause is transient, such as myocarditis, drugs, electrolyte disorders, myocardial ischemia, etc., the cause can be removed actively, and temporary pacing can be implanted in the early stage, which can be recovered after the cause is removed. If it is permanent, a permanent pacemaker needs to be implanted to ensure the patient’s life safety.