Valve morphology in complete atrioventricular septal defect: variability relevant to operation

The remodeling of the atrioventricular valves in patients with complete atrioventricular septal defects is the crucial part of surgical repair. Variability in valve morphology is an important factor. This study evaluates the variability in morphology of the anterior and posterior leaflets in 30 heart specimens. All hearts had an anterior bridging leaflet: Rastelli type A in 12, type B in 2, and type C in 16. The posterior leaflet revealed four morphologic patterns: a right- and left-sided posterior leaflet, both inserting directly onto the crest of the ventricular septum (5 hearts); a common posterior leaflet attached to the septal crest by a membrane (2 hearts); a common posterior leaflet attached to the septal crest by multiple chordae (13 hearts); and a virtually free-floating posterior leaflet (11 hearts). The categorization is surgically relevant in making a distinction between hearts with and without an interventricular communication underneath the posterior leaflet. Surgically relevant variations occurred also in arrangement and positioning of chordae originating from the right septal side. There was no relationship between the Rastelli classification of the anterior leaflet and that of the posterior leaflet. The variability in morphology of the posterior leaflet and its attachments to the ventricular septum appear equally crucial for successful repair as that of the anterior leaflet.