Introduction: Congenital malformations of the mitral valve are relatively rare and present with a wide spectrum of morphologic abnormalities. Descriptions of functionally uni-leaflet mitral valves are extremely rare and largely limited to few case reports. (1-3) We present two patients with almost complete absence of posterior mitral valve leaflet (PML) in which three-dimensional transthoracic echocardiography (3D TTE) was used as a valuable diagnostic tool.

Case A: 38-year-old woman was operated due to constrictive pericarditis. Real-time 3D TTE showed only a single, long, morphologically valid, properly movable leaflet in the place of the anterior mitral leaflet (AML) that leans itself on the PML rudiment. The subvalvular apparatus was anatomically normal, with appropriate chordal attachments and papillary muscles. Color Doppler showed a narrow jet of mitral regurgitation directed towards the lateral wall of the left atrium.

Case B: 24-year-old patient was admitted due to acute myocardial infarction with ST elevation of inferoposterolateral region and right ventricle. Real time 3D TTE showed a rudiment of the PML with a prolapse of enlarged AML and excentric moderate MR directed towards posterolateral wall of the LA, with no progression within a one year control period.

Conclusion: Until today there was no need for corrective surgery in these patients, but prognosis remains uncertain. The potential of worsening mitral regurgitation, primarily as a consequence of annular dilatation, has been postulated. Real-time 3D TTE is important in diagnosing heart valve diseases because it enhances the evaluation of morphologic abnormalities and improves understanding of complex relationships through more precise imaging and presentation of interrelations of different parts of the mitral apparatus.