Some coronary heart disease patients have asymptomatic myocardial ischemia, and many may not exhibit clear symptoms of angina. Some patients can show signs of angina, with typical symptoms being a pressing pain in the anterior chest area or feelings of suffocation and shortness of breath, primarily located behind the sternum, or radiating to the precordial area and left upper limb, as well as the left side of the back. These symptoms often occur under common triggers such as physical exertion, emotional stress, overeating, or exposure to cold. If it is angina, it generally lasts less than 30 minutes and can be alleviated by rest or taking sublingual nitroglycerin. Some patients who experience a heart attack may have pain in the same areas, but the nature and duration of the pain will be significantly increased, and nitroglycerin may be less effective.