The symptoms of myocardial ischemia are as follows: 1. Most patients with myocardial ischemia mainly present with chest pain. Typical chest pain is located in the precordial region or behind the sternum, with a fist-sized or palm-sized range, with burning and crushing pain, accompanied by a feeling of suffocation. Myocardial ischemia does not simply have the manifestation of angina pectoris, but some patients also have arrhythmia, such as premature beats, ventricular tachycardia and ventricular fibrillation; 2. Some patients with myocardial ischemia will have dyspnea, chest tightness and discomfort in the prone position, which can be gradually relieved after sitting or standing; 3. The manifestation of myocardial ischemia is highly variable, and some patients show epigastric discomfort, toothache or back pain. If the above discomfort occurs, which is aggravated by activity and alleviated by rest, myocardial ischemia should be considered.