Left back pain may be a sign of acute myocardial infarction, aortic coarctation, frozen shoulder, muscle strain, and acute pancreatitis. 1. Myocardial infarction: Due to acute obstruction of coronary arteries, the heart becomes necrotic due to the obstruction of blood supply, which impairs the function of the heart. There may be chest pain, a feeling of suffocation, and the pain may radiate to the left shoulder and left back. 2. Aortic coarctation: Blood enters the middle layer of the aorta and extends along the arterial wall and peels off, forming a coarctation hematoma. Symptoms such as severe back pain, chest pain, abdominal pain, nausea and dyspnea may occur. 3. Frozen shoulder: aseptic self-limited inflammation of the soft tissues of the shoulder joint. Difficulty in shoulder joint movement as well as shoulder and back pain will occur. 4. Muscle strain: If you do too much labor or exercise for a long period of time or for a short period of time, it will cause muscle strain in the left back, which will lead to pain. 5. Acute pancreatitis: it can be caused by overeating, excessive drinking, etc. It can cause persistent and severe pain in the upper abdomen, which radiates to the lower back and causes pain in the lower back. If the above symptoms occur when you have left back pain and the pain is not relieved for a long time, you should pay attention to it and go to the hospital for examination and treatment in time.