Diagrammatic representation of a complete atrioventricular septal defect on the left. Note that instead of a mitral and a tricuspid valve, there is only one large atrioventricular valve. There are cordal attachments to the crest of the ventricular septum. The ostium primum ASD and an inlet VSD are readily apparent. On the right is an echocardiographic four-chamber view of a complete atrioventricular canal defect. The arrows represent the annulus of the common AV valve. The “X” indicates an associated ostium secundum ASD and the “*” shows the location of the ostium primum ASD. The “o” shows the location of the VSD. Abbreviations: MV mitral valve remnant, TV tricuspid valve remnant, RA right atrium, RV right ventricle, L lateral valve leaflet, A anterior leaflet, P posterior leaflet, LV left ventricle (Adapted from Feldt et al. (1976) Atrioventricular Canal Defect, WB Saunders, Philadelphia and reproduced or adapted from Driscoll, David (2006) Fundamentals of Pediatric Cardiology. Lippincott Williams & Wilkins, Baltimore with permission of the author and publisher)