Tightness and pain in the left side of the chest, dyspnea can be caused by cardiovascular system diseases, respiratory system diseases and so on. 1. Cardiovascular system diseases: If the patient has chest tightness and pain, accompanied by symptoms such as panic, often caused by activities, exertion, emotional excitement and other triggers, angina pectoris or myocardial infarction and other diseases may be considered. 2. Respiratory diseases: if the patient has chest tightness and pain, dyspnea, accompanied by cough, sputum, fever and other symptoms, the pain is mainly related to respiration, considering that it may be caused by lung infection or pleurisy; such as the patient before the onset of the disease has a breath holding and other triggers, sudden chest pain on the left side, followed by chest tightness and dyspnea, considering that it may be related to the left side of the pneumothorax. Left-sided chest tightness and dyspnea can also be caused by other diseases, it is recommended to consult a doctor in time, improve the examination, clarify the cause of the disease, and follow the doctor’s instructions for treatment, so as not to delay the condition.