Under normal circumstances, if the patient has pain in the back of the left chest, the following points should be taken into consideration: First, consider high-risk chest pain, such as acute coronary syndrome, tension pneumothorax, aortic coarctation, pulmonary tethering, although the incidence rate of these cases is low, but the fatality rate is high, so it is necessary to pay attention to it, and once the symptoms mentioned above appear, it is necessary to go to the hospital quickly for hospitalization. Second, for moderate risk of chest pain, such as coronary atherosclerotic heart disease, unstable angina, severe acute myocarditis, acute pericarditis, or patients with severe heart failure, malignant arrhythmia will also be pain in the back of the left chest, and for large lung infection, pleurisy, pleural effusion will have the above symptoms. Third, for mildly dangerous chest pain, such as herpes zoster on the left side, intercostal neuralgia, or even when the patient has cardiac neurosis triggered by phytoneurologic dysfunction, the patient will also have this symptom.