The reason why pulmonary stasis is the main cause of left heart failure is that the venous blood injected into the lungs by the pulmonary artery becomes arterial blood with high oxygen saturation after gas exchange in the lungs, which flows back into the left atrium through the “pulmonary vein” and then to the left ventricle for discharge by the aorta to supply the organs, tissues and cells of the whole body to maintain their functions. In left heart failure, the left ventricular blood cannot be pumped out completely, which leads to increased left ventricular pressure, left atrial stasis, pulmonary vein stasis, and the blood exchanged in the lung cannot flow back into the left atrium through the pulmonary vein, which causes pulmonary stasis, and further development, pulmonary edema is formed. Preventive measures for pulmonary stasis in left heart failure 1. Timely control or get rid of infectious foci inside and outside the heart, control infectious foci such as tonsillitis caused by hemolytic streptococci; prevent and control rheumatic activities; actively prevent and control infective endocarditis, respiratory tract infections and infections in other areas. 2.Rapid correction of arrhythmias When arrhythmias occur in heart disease patients, they should be quickly corrected, and the ectopic rhythm should be restored to normal sinus rhythm, or the bradycardia and tachycardia should be controlled in a safe range to prevent the occurrence of heart failure. 3.Correct water-electrolyte disorder and acid-base balance disorder. 4.Treat anemia and eliminate the cause of bleeding. 5.Avoid excessive and rapid infusion of fluids. 6.Discontinue or cautiously use certain drugs that inhibit myocardial contractility. 7.Avoid overexertion and emotional excitement. Excessively obese people should control their diet.