Suddenly unable to breathe at night, the patient is considered to have left heart failure. Due to lying down at night, the lower limbs increase the amount of blood returned to the heart, which increases the burden on the heart, thus leading to increased pulmonary stasis; at the same time, the diaphragm is elevated, limiting the expansion and retraction of the lungs; at night, due to the increased excitability of the vagus nerve, resulting in small bronchial constriction, etc. All of these can cause an increase in left heart failure, causing the symptom of sudden shortness of breath at night. For patients with this condition, they should go to the hospital as soon as possible and actively give drugs to reduce the heart load, cardiac drugs to enhance the contraction of the heart muscle if necessary, and drugs to inhibit the remodeling of the heart muscle and improve the prognosis. The cause of heart failure should also be actively searched for and treated to eliminate the triggers that cause heart failure to worsen.