AV block is categorized into first-degree AV block, second-degree AV block and third-degree AV block, of which second-degree AV block can be further categorized into second-degree type I AV block and second-degree type II AV block. AV block is a kind of conduction block in which the conduction time between atria and ventricles is prolonged, and the P-Q interval is prolonged, which is greater than 0.20s, as seen on the electrocardiogram, and the patients usually do not have obvious symptoms. Second-degree type I atrioventricular block is a block in which the P-R interval is gradually prolonged until the P wave fails to travel downward and the QRS wave disappears, and the patient may also have no obvious symptoms. In degree II type II AV block, the P-R interval is fixed, but the P wave suddenly fails to transmit downward, and there may be more than one P wave in front of the QRS wave, and the patient may have symptoms such as palpitations. In degree III AV block, also called complete AV block, the P wave is not related to the QRS wave, and the agitation can not be transmitted from the atrium to the ventricle at all, and the patient may have symptoms such as dizziness and fatigue. If the examination finds AV block, please go to the hospital in time and follow the doctor’s instructions for treatment.