Diagonal branch stenosis 80% is a severe narrowing of a branch of a coronary artery that may lead to angina and even myocardial infarction. Diagonal branches are the main branches of the left anterior descending branch of the coronary arteries that supply the anterior wall of the left ventricle. Hypoxic degenerative necrosis of the heart muscle occurs when the coronary arteries are narrowed and cannot supply blood to the heart muscle to meet its normal survival and metabolic needs. When the degree of coronary artery stenosis reaches more than 75%, it is a severe stenosis, and the patient is prone to angina attack or even myocardial infarction, which is mainly manifested by the pain in the anterior region of the heart with a sense of squeezing, or the pain radiates to the left forearm, the back of the shoulder, and the oral cavity, etc. Acute myocardial infarction carries the risk of sudden cardiac death, which requires urgent interventional therapy. If you have precordial pain and other uncomfortable symptoms, please consult a doctor in time, so as not to miss the best time for treatment.