Second-degree block depends on which type it is. Generally, second-degree type I AV block does not lead to sudden death, while second-degree type II AV block may lead to sudden death, but most of the time the patient is experiencing mild dizziness, fainting, and other symptoms. Second-degree AV block is a phenomenon in which the conduction system between the atria and the ventricles is blocked, resulting in delayed conduction of atrial impulses or the inability to transmit impulses to the ventricles. A high degree of AV block may lead to sudden death, and a patient with second-degree type II AV block is said to have a high degree of AV block if more than two consecutive P-waves fail to travel down the atrium. Second-degree type I AV block is a block in which the P-R interval is gradually prolonged until one P wave fails to go down, and the patient may experience symptoms such as palpitations and chest tightness, while second-degree type II AV block is a block in which the P-R interval is fixed and the P wave suddenly fails to go down, and the patient may experience symptoms such as mild dizziness and fainting. If examination reveals second-degree AV block, please follow the doctor’s instructions for treatment.