The causes of chest tightness at night in coronary artery disease include: increase in the volume of returned blood, elevation of the diaphragm, excitation of the vagus nerve, redistribution of blood, decrease in blood pressure, and spasm of the coronary artery. 1. Increase in the volume of returned blood: when lying down at night, the volume of returned blood will increase, which will lead to an increase in the load on the heart, and at the same time, due to the decrease in the volume of peripheral circulating blood, the diaphragm will be elevated, and it will be difficult to breathe, so it will lead to chest tightness. 2. Vagus nerve excitation: vagus nerve tone increases at night, leading to small bronchial contraction, diaphragm elevation, lung capacity reduction, etc., thus contributing to hypoxic dyspnea, leading to chest tightness. 3. Blood redistribution: after dinner, gastrointestinal functional activity increases, blood distribution in the gastrointestinal tract increases, and insufficient blood supply to the heart and brain leads to angina pectoris and chest tightness manifestations. 4. Blood pressure decreases at night, and at the same time, if the coronary artery spasm, can lead to ischemia of the heart, it will lead to angina pectoris, which will produce the manifestation of chest tightness. If you suffer from coronary heart disease and symptoms of chest tightness at night, you need to go to the hospital in a timely manner and according to the doctor’s instructions for treatment, to avoid delaying the condition.