As a common heart valve lesion, mitral stenosis can cause dyspnea, hemoptysis and, as the disease progresses, heart failure, atrial fibrillation and other dangerous conditions. Timely surgery can help patients treat the disease and improve their quality of life. So, when should mitral stenosis be operated? 1. Mitral stenosis. Patients, who are slightly loaded, i.e., have worsening symptoms, which means that cardiac function compensation is in a critical state and should be operated to stop the progression of the disease. 2, atrial fibrillation. The incidence of atrial fibrillation is higher in patients with mixed mitral valve lesions (stenosis combined with insufficiency), followed by patients with mitral stenosis and lower in patients with mitral valve insufficiency. Atrial fibrillation poses several serious problems for patients: (1) loss of left atrial systolic function due to atrial fibrillation results in a decrease in cardiac output of about 20%-25%; (2) the presence of atrial fibrillation worsens clinical symptoms, especially in the early stages of atrial fibrillation, and the rapid heart rate can lead to pulmonary edema; (3) atrial fibrillation increases the chance of left atrial thrombosis and embolism, which increases approximately 7-fold compared with sinus rate. (3) Atrial fibrillation increases the chance of left atrial thrombosis and embolism, which is about 7 times higher than the sinus rate. 3. Embolic comorbidities. The incidence is higher in patients with mitral stenosis and is 4 times higher than in patients with mitral valve insufficiency. Therefore, patients with mitral stenosis who have left atrial thrombosis or a history of embolism should be operated on, even if asymptomatic. 4, pulmonary hypertension. Most patients with pulmonary hypertension, although not immediately returning to normal after surgery, can gradually decline, the degree of which depends on the pulmonary vascular pathology. Surgery must be performed before severe pulmonary vascular disease. There are still some patients with mitral stenosis with severe pulmonary hypertension who have never experienced symptoms of pulmonary venous hypertension, but have signs of pulmonary hypertension and right ventricular hypertrophy, and low cardiac output at rest; such patients should be operated even if they are asymptomatic.