Atrioventricular block is categorized into degree I, II and III, and degree III atrioventricular block is more serious. Atrioventricular block is an abnormality in the conduction of electrical excitation between the atria and the ventricles during the conduction of electrical excitation in the heart. Third-degree atrioventricular block, also known as complete atrioventricular block, refers to the fact that all atrial excitation is not transmitted to the ventricles, and is characterized by the activities of the atria and ventricles being independent of each other and the atrial rate being faster than the ventricular rate. The symptoms of third-degree AV block are related to the speed of the ventricular rate and concomitant diseases. Patients may feel tiredness, fatigue, dizziness, fainting, angina pectoris, etc. If heart failure occurs, there will be tightness in the chest, shortness of breath, and limitation of activities, and even sudden death may occur. A pacemaker is required. If the symptoms of third-degree atrioventricular block persist without relief, prompt medical treatment is needed.