As we introduced earlier, the normal heartbeat is initiated by the sinus node, which is the “board of directors”, and then it is transmitted down the hierarchy to make the whole heart beat in an orderly manner. Among them, the atrioventricular node, as the “middle leader”, is an important conduction channel connecting the atria and the ventricles, so that the orders from the sinus node can be passed from the atria to the ventricles in an orderly manner, and the atria and ventricles are like a harmonious “couple”, stable and harmonious. However, if the atrioventricular node becomes “lazy” or “on strike”, so that “superior orders” are delayed or even not transmitted, it will affect their harmony and cause The ventricular beat cannot keep up with the rhythm of the atria, causing the ventricular rate to slow down, a condition we generally call “atrioventricular block. Atrioventricular block can be divided into three degrees: degree I atrioventricular block: the “command” of the sinus node is delayed from the atria to the ventricles. This makes the ventricle often lag behind the atrium for a long time before it starts beating, which is equivalent to the ventricle being “late”. Atrioventricular block of degree II: It is divided into degree II type 1 and degree II type 2, which means that the “command” from the sinoatrial node is occasionally not transmitted from the atria to the ventricles. This is equivalent to the ventricle occasionally “missing” an appointment. Atrioventricular block of degree III: This means that the “command” from the sinus node cannot be transmitted from the atria to the ventricles at all, which is equivalent to the atria and ventricles “breaking up” and going their separate ways. This results in severe bradycardia, or even prolonged arrest, because of the very slow voluntary beating of the ventricles. Generally speaking, degree I AV block and degree II type 1 AV block have less impact on patients’ life and are less dangerous, so medication can be chosen temporarily. However, patients with II degree 2 and III degree AV block are prone to dizziness, chest tightness and other symptoms, and in severe cases, black haze, syncope, and even sudden death. However, AV block is not a difficult disease and can be diagnosed clearly with the most common ECG. Moreover, there are very mature emergency protocols and treatments for AV block, namely temporary pacemaker placement and permanent pacemaker implantation. Therefore, as long as early detection, early diagnosis and early treatment are achieved, there is no need to feel anxious about this disorder.