Real-time 3-dimensional transesophageal echocardiography of the atrioventricular septal defect.

Being able to view the morphological details of the heart malformation in any patient with the diagnosis of atrioventricular septal defect (AVSD) is invaluable in surgical planning, especially in the current era of modified 1-patch versus 2-patch techniques. Real-time 3-dimensional transesophageal echocardiography (RT 3D TEE) is a recently developed technique that allows real-time high-quality images akin to viewing the heart specimen. We present the principal pathomorphological features of AVSD as visualized by RT 3D TEE. The hallmark of AVSD is a common atrioventricular junction guarded by a common atrioventricular valve.1 In the normal heart, when seen from atrial perspective, the aortic valve is wedged between the mitral and tricuspid valve. In AVSD, because of the common AV junction, the aortic valve is in an “unwedged” position (Figure 1). The valve consists of 5 leaflets: the superior and inferior bridging leaflets, each of which overrides the ventricular septum, a left mural leaflet, a right anterior, and a right inferior leaflet (Figure 2). Whether the bridging leaflets are joined together distinguishes the complete form from the partial form. In partial AVSD (also termed “ostium primum ASD”), a tongue of leaflet tissue connects the bridging leaflets and the undersides of these leaflets are adherent to the crest of ventricular septum, dividing the common valve functionally in 2 separate valvar orifices and allows shunting at the atrial level only (Figure 3). By comparison, in the heart with complete AVSD, the common AV valve has a common valvar orifice. Although the bridging leaflets are tethered to the ventricular septum to varying extents, the superior bridging leaflet is often free-floating. Shunting exists at both interatrial and interventricular levels owing to the gap between the inferior margin of true atrial septum and the crest of ventricular septum (Figure 4). RT 3D TEE well demonstrates the relative sizes of the valvar orifices, allowing designation of balanced or unbalanced forms. The morphology of the leaflets of the AV valve and the so-called mitral cleft (Figure 5) is also well visualized. Left ventricular outflow tract obstruction is an important concern after surgical repair since the outflow tract is elongated and inherently narrow in this malformation. The scoop of the ventricular septum and the relationship of the superior bridging leaflet to the septal crest contribute to the characteristic “goose-neck” deformity of the left ventricle seen on angiography (Figure 6). The depth of the scoop at the left ventricular outflow tract is readily visible on RT 3D TEE, allowing the surgeon to see around the corner before carrying out surgical repair (Figure 7). In summary, RT 3D TEE can allow demonstration of “living” anatomy of AVSD in detail, using novel perspectives that are invaluable for surgical planning.