In second-degree type I AV block, the progressive prolongation of the P-R interval is mainly manifested on the electrocardiogram, until a P wave cannot be transmitted, and there is no QRS wave behind the P wave, which is called second-degree type I AV block. Second degree type I AV block can be either physiological or pathological. If it is pathological, such as secondary to a disease, such as sudden myocardial infarction or myocardial ischemia, which causes second degree type I AV block, it is necessary to treat the underlying cause to prevent the progression of the disease. disease progression.