In the event of myocardial infarction, the degree of stenosis of several branches of the left coronary artery, such as the anterior descending branch of the diagonal branch and the gyrus branch, should be clarified by coronary angiography. If the degree of stenosis is greater than 70%, coronary stent implantation or surgical open-heart bypass surgery should be given; if the degree of stenosis is less than 70%, drug conservative treatment can be given, through these treatment options can make evidence of myocardial infarction.