Patients with chest tightness will feel better with chest tightness and shortness of breath when they lie down because the amount of blood returned to the heart increases and the heart gets more blood and oxygen per unit time, which is a common symptom of patients with coronary heart disease. Due to the narrowing of one or more of the three coronary arteries on the surface of the heart, patients with coronary artery disease will suffer from hypoxia and ischemia when they do not receive enough oxygen, and then they will experience chest tightness, panic and shortness of breath. When the patient lies down, the problem of myocardial ischemia is temporarily improved because the amount of blood returned to the heart increases, and more blood is taken in per unit time, and more oxygen is obtained through the exchange of the lungs. Therefore, for patients with coronary artery disease, if they lie down when they have chest tightness, they will feel less chest tightness and shortness of breath after the increase in the amount of returning blood. Instead, this situation is more considered to be coronary heart disease and requires further examination at the hospital.