A stenosis of 80% of the first diagonal branch is severe and may lead to severe myocardial ischemia and even the risk of myocardial infarction. The first diagonal branch originates from the anterior descending branch, mainly for the left heart to provide blood supply, the stenosis degree reaches 80% of the condition is more serious, will lead to a significant reduction in myocardial blood supply, the patient may have angina symptoms, such as plaque rupture can occur in acute myocardial infarction. The first diagonal branch stenosis 80% need to give antiplatelet therapy, commonly used drugs have aspirin or clopidogrel, at the same time to give atorvastatin and other drugs to stabilize plaque, angina attack patients need to add isosorbide nitrate. For patients with frequent angina attacks, stents can be implanted if necessary. Patients with coronary artery stenosis should use medication under the guidance of a physician to avoid serious complications.