A 90% stenosis of the distal coronary artery gyratory branch is very dangerous. There are 2 main coronary arteries in the human heart, the left main artery and the right main artery, and the left main artery is further divided into the anterior descending branch and the circumflex branch. The circumflex branch mainly provides blood supply to the high lateral and lateral posterior walls of the heart. When the circumflex branch is 90% narrowed, the blood supply to these areas will be seriously affected, which may cause arrhythmia, angina pectoris or even myocardial infarction, and require immediate medical intervention. For the treatment of coronary artery disease, stent implantation is required for severe stenosis of the dominant vessel to restore the blood supply to the myocardium as soon as possible to minimize myocardial damage; at the same time, antiplatelet agents, such as aspirin and tegretol, and antimyocardial ischemic agents, such as nitrate drugs, β-blockers, and calcium channel blockers should also be applied for adjunctive treatment. If you feel unwell, you should go to the hospital in time, under the guidance of the physician, to identify the cause and then give targeted treatment.