Different forms of atrioventricular canal defects

Anatomic and physiologic similarities between the different forms of AVSDs are illustrated. Complete AVSDs have 1 annulus with large interatrial and interventricular communications. Intermediate defects (1 annulus, 2 orifices) are a subtype of complete AVSD. Complete AVSDs have physiology of VSDs and ASDs. In contrast, partial AVSDs have physiology of ASDs. Transitional defects are a form of complete AVSD in which a small, insignificant inlet VSD is present and, as a result, the physiology is more similar to that of a partial defect. Partial defects and the intermediate form of complete AVSD share a similar anatomic feature: A tongue of tissue divides the common AV valve into distinct right and left orifices.