- Etiology: spectrum of ostium primum atrial septal defect, cleft mitral leaflet, inlet ventricular septal defect, common AV valve, complete endocardial cushion defect
- CXR: Shunt vascularity, cardiomegaly, gooseneck deformity of elongation of left ventricular outflow tract on angiogram
- Clinical: 30% of AV canal seen in Down syndrome, 30% of Down syndrome have AV canal
