[Atrioventricular septal defect in an adult patient: There are 'clefts' and clefts].

In this report, we present the case of an adult male with severe mitral regurgitation due to an atrioventricular septal defect. Anatomical assessment by two- and three-dimensional transesophageal echocardiography was essential for detailed morphological characterization and surgical planning. The different features of a 'cleft' in an atrioventricular septal defect compared to an anterior leaflet cleft in an otherwise normal mitral valve are here discussed.