The most commonly involved heart valve in rheumatic endocarditis is the mitral valve, which is most likely to cause mitral stenosis. The basic pathological changes of rheumatic mitral stenosis are fibrosis and contracture of the valve leaflets and tendons, and interfacial adhesions of the valve leaflets. These lesions cause the position of the valve to shift downward, in severe cases, such as funnel-shaped, with the bottom of the funnel facing the left heart ring and the tip facing the left ventricle, with restricted opening of the mitral valve, reduced orifice area, and obstructed blood flow, thus This leads to a series of pathological and physiological changes. About 25% of patients with rheumatic heart disease have simple mitral stenosis, 40% have mitral stenosis with mitral valve insufficiency, and the aortic valve is often involved at the same time.