**5.1 Left AV valve**

In normal hearts, mitral valve has two leaflets, anterior and posterior with a zone of opposition in one plane. In hearts with AV septal defects, the left AV valve closes in tri-foliate fashion with zones of opposition between posterior, superior and inferior bridging leaflets. This characteristic feature of the left AV valve in AV septal defects will never achieve a mitral valve as in normal hearts. Usually, jet of LAVV cleft is directed to the ventricular septum when compared to isolated mitral valve clefts which are directed anteriorly towards the aortic valve [11]. Rarely, a fusion of the leaflets within the left AV valve (bridging and posterior leaflet) would lead to a double orifice valve. The combined area of the double orifice valve is always less than the single left AV valve area.
