Moderate stenosis is defined as a stenosis of 50% to 70%. Usually there are three degrees of stenosis, less than 50% is mild stenosis, 50% to 70% is moderate stenosis and 70% to 90% is severe stenosis. Generally stenosis of the vessel wall is mainly caused by atherosclerosis, which leads to intima-media thickening and plaque formation, and the degree of stenosis may become more severe with time and age. If the patient has moderate stenosis, the distal blood supply function is generally normal and there are no signs of unstable angina. Generally, the stent can be left in place for the time being. If the patient has significant angina symptoms, a stent needs to be placed so that the likelihood of a new infarction can be reduced. Patients with moderate stenosis should seek medical attention to avoid delays.