Patients with chronic myocardial infarction will have different degrees of precursors, such as patients with different degrees of chest tightness, shortness of breath, palpitations, decreased activity tolerance, obvious symptoms of fatigue and exhaustion after activity, and clinical symptoms and reactions accompanied by dyspnea after exertion, or even wheezing. Some patients may also experience anterior cardiac pain, such as crushing and cramping pain behind the sternum, spreading and radiating to the left shoulder and posterior back. Some patients also have clinical symptoms and manifestations such as stomach pain, or toothache, facial neuralgia, etc. Some patients also have numbness around the left shoulder and arm. These are all precursors of chronic myocardial infarction. If these precursors occur in patients with previous coronary artery disease, it is recommended to go to the hospital for examination.