Objective:To analyze the clinical manifestations,imaging characteristics,treatment measures,and efficacy of mitral valve aneurysm(MVA),and to enhance the clinicians'understandings of MVA.Methods:The clinical data of one patient with aortic valve bicuspid malformation leading to mitral valve anterior leaflet aneurysm were collected.The clinical diagnosis was confirmed based on the clinical characteristics and imaging features,the treatment methods were selected,and the efficacy was analyzed.The relevant literatures were reviewed.Results:The patient,a 68-year-old female,was admitted due to palpitations and shortness of breath for 13 years,and the symptoms worsened one month ago.Thirteen years ago,the patient experienced palpitations and shortness of breath without any inducement and was diagnosed with"heart valve disease"in the local hospital.The symptoms worsened one month ago,leading to hospitalization.The transthoracic two-dimensional echocardiography(TTE)results showed the left ventricular hypertrophy,bicuspid aortic valve with thickened and echogenic leaflets,the forward flow velocity was increased,and the aortic valve orifice area was 2.0 cm2;the mitral valve anterior leaflet margin was slightly thickened and echogenic,presenting a cystic"honeycomb-like"structure closely related to the aortic valve regurgitation jet,which appeared to enter the"sac".The preoperative transesophageal echocardiography(TEE)results showed the bicuspid aortic valve malformation with the anterior leaflet prolapsing into the left ventricular outflow tract during diastole;a"sac-like"structure was detected on the atrial surface of the mitral valve anterior leaflet,changing shape with the cardiac cycle and communicating with left ventricular blood flow.The ultrasound diagnosis was bicuspid aortic valve malformation with transverse fissure,severe regurgitation with mild stenosis,and mitral valve anterior leaflet aneurysm.Intraoperatively,the aortic valve annulus was enlarged with the significant leaflet regurgitation.The leaflets were excised,and a 23 mm bioprosthetic valve was implanted in the aortic position.Upon exploration through the aortic valve orifice,a"sac-like"structure was found on the mitral valve anterior leaflet,which was not specially treated.The postoperative TEE results showed good echo and activity of the aortic bioprosthetic valve,and the"sac-like"structure on the mitral valve remained unchanged.The follow-up results at 10 d and 4 months after operation showed good echo and activity of the aortic bioprosthetic valve,and compared with before operation,there was no significant change in the nature and size of the mitral valve cystic lesion.Conclusion:MVA is clinically rare.TTE is currently the most valuable imaging diagnostic method for MVA,especially when combined with TEE,which is the best diagnostic method and can assist in the treatment and efficacy evaluation.