**7. Pathophysiology**

In patients with complete AVSD, there is one common AV valve with large atrial and inlet VSD (**Figure 8**). In intermediate form, there are two AV valve orifices, which are formed by a tongue of tissue between superior and inferior bridging leaflets. It has similar physiology as the complete form with large ASD and VSD. In partial AV septal defects, where there are two AV valve orifices with the bridging leaflet attached to ventricular septal crest, giving rise to only interatrial communication (**Figure 9A**). In some instances, there could be communication at the ventricular level from the chordal attachments which is described as a transitional type (**Figure 9B**). In all forms of AV septal defects, the left AV valve invariably has a cleft. Rarely there will be no septal communications seen with other common features of AVSD [8].
