The symptoms of cardiac ischemia are mostly chest tightness and chest pain, which may be relieved by resting or taking nitroglycerin. Myocardial ischemia refers to the conflict between coronary blood supply and myocardial blood demand due to various reasons, so that the coronary blood flow cannot meet the needs of myocardial metabolism. Causes of decreased myocardial blood supply and oxygen supply or increased myocardial oxygen demand may lead to the occurrence of myocardial ischemia. The early symptoms of myocardial ischemia are mostly manifested as chest pain, which is typically located behind the sternum and can radiate to the left chest, the back of the left shoulder, the front inner side of the left upper arm; it can also radiate to the neck, pharynx, jaw and other parts; the nature of the pain is typically pressure-like, mostly accompanied by obvious chest tightness, and some patients have a sense of near death, which often forces patients to stop activities immediately. There are many triggers for the onset of symptoms, such as going upstairs, fast walking, exertion, full meal, cold, emotional excitement, etc. The symptoms may be relieved by quiet rest or taking nitroglycerin. Some patients have atypical symptoms, such as epigastric pain and subxiphoid discomfort. The main risk factors causing myocardial ischemia are hypertension, hyperlipidemia, diabetes, smoking, obesity, etc. If the above symptoms of chest tightness and chest pain occur in patients with a history of hypertension, hyperlipidemia, diabetes, etc., or if the patient usually smokes a lot and is obese, this situation should be highly suspected whether the chest tightness and chest pain are caused by myocardial ischemia. Patients should promptly go to a regular hospital for electrocardiogram or cardiac enzyme examination to exclude the possibility of myocardial ischemia.