Hidden pain inside the left upper chest may be caused by coronary heart disease, pleurisy, costochondritis and other diseases. 1. Coronary heart disease: coronary heart attack will cause angina pectoris, myocardial ischemia, resulting in local ischemia and hypoxia, myocardial accumulation of a large number of metabolites, resulting in hidden pain inside the left upper chest. 2. Pleurisy: generally due to inflammation caused by the lowering of the body’s immunity or chest infection. Inflammatory factors will be released to the surface of the pleura, resulting in an increase in the volume of pleural water between the dirty pleura and the wall pleura, chest pain, chest tightness, can also show a hidden pain inside the left upper chest. 3. Costochondritis: aseptic inflammation of the 2nd-4th rib cartilage in the anterior chest, which can be manifested as localized swelling and vague pain in the left upper chest, especially aggravated when taking a deep breath or exerting chest. When vague pain in the upper left chest occurs, please do not self-medication, it is recommended to go to the hospital in time to find out the causes of vague pain in the upper left chest, and treat the symptoms under the guidance of the doctor.