MVA is a rare disease. The incidence of it is 0.2–0.3% on echocardiography.(3) It is more commonly occurred in anterior mitral valve leaflet than posterior leaflet.(1, 2, 4, 6) It usually occurs in association with infective endocarditis of the mitral and aortic valves. Perforation is the most threatened complication of MVA. Moreover, some aneurysms may lead to valve rupture. In a literature review, most patients reported before were with infective endocarditic and the MVA occurred in anterior leaflet. (1–5) Eight MVA cases were reported on posterior before (Table 1). (1, 2, 5–9)
The mechanism of MVA was still unclearly. Due to MVA usually was a complication of aortic valve infective endocarditis. Some experts think severe aortic regurgitation may associated with MVA’s formation. Aortic regurgitation, which was caused by destruction of the aortic valve leaflets, strikes the anterior of MV and may lead to secondary infection. The MV infection then causes the development of an aneurysm. But some diseases such as rheumatic disease, myxomatous degeneration, connective tissue degeneration, Marfan syndrome, osteogenesis imperfect and pseudoxanthoma elasticum, can lead to MVA in absence of endocarditis. (3, 6, 7) In our patient, there was no infective endocarditis of both aortic valve and MV. No regurgitation of aortic valve was found. The patient was absence of those diseases noted above. The causation of MVA of this patient was unknown. This case indicates some MVA may be spontaneous.
The characteristic of MVA in echocardiography was a saccular, bulging structure on the mitral leaflet. This saccular node opens to left ventricle. It expends on systole and collapses during diastole. (3–5) But this valuable feature was not detected in our patient. We did not see it collapsed on diastole (supplementary video 1). It indicates not all MVA can be seen this special characteristic. This increases the difficulty in diagnosis of this patient. So we are confused it is MV prolapse or a mass after TTE. We speculated its large size and complex hemodynamics lead to this nonspecial echo characteristic. As the size of the MVA was 18.2*14.2 mm. Most aneurysm protruded into left atrial and the neck of MVA was small. The neck was closed in diastole due to an instantaneous pressure change and complex hemodynamics. The blood in the MVA could not flow out. So we did not see it collapsed during diastole. This features were described in other patient before. (8, 9) We found all these aneurysms were with large size which usually more than 10mm. This increase the difficulty of diagnosis. Some patient was diagnosed with a mass instead of MVA. (8, 9)
RT-3D-TEE was more reliable to assess mitral leaflet perforation and visualize the detailed morphology of MVA than TTE. Moreover, RT-3D-TEE can show spatial configuration of MVA in real time. (1–3, 6) Color Doppler can show direct communication between the left ventricle and the aneurysm, which can distinguish MVA from other MV abnormalities. (4) In our patient, we suspected the lesion was a prolapse or a mass after TTE. But MVA was definitely diagnosed after observing a jet flowed from left ventricle into the cystic and whirled in it by TEE. This feature was another special characteristic of MVA in large MVAs. Our patient reveals some MVA may not collapse in diastole but can be detected this direct communication between the aneurysm and the left ventricle. This case indicates it would be a more sensitive feature of MVA with large size. But more cases should be studied to certify this assumption.
Surgery should be done in MVA patients with severe regurgitation of MV or aortic valve. (3–5) Prosthetic valve re placement was recommended for patients who were not suitable for valvuloplasty. Our patient was treat with valvuloplasty and was fine during 2 years.