FIG 31.26 Two-dimensional (A) and color Doppler (B) echocardiographic images in the apical plane demonstrate a thickened left atrioventricular valve with two separate color inflow jets, suggesting a double orifice valve la, Left atrium; lv, left ventricle Common Valvar Orifice The typical echocardiographic features of an atrioventricular septal defect with a common valvar orifice are first identified in four-chamber sections There are usually both interatrial and interventricular communications, albeit the sizes of the components of the defect are variable The right ventricle is often dilated, as significant shunting at atrial level is the rule The attachments of the bridging leaflets to the crest of the ventricular septum are variable, as is the extent of their bridging The inferior bridging leaflet, often visualized in the apical and subcostal four-chamber sections as well as the en face modified subcostal view, is frequently attached by a midline raphe to the crest of the ventricular septum, precluding any interventricular shunting close to the crux (Fig 31.27A and C) It may, however, be free-floating, and the ventricular component will usually be evident throughout the length of the septum (Fig 31.27B and D; also see Fig 31.19C–D) Most variation in the size of the ventricular component, however, is seen beneath the superior bridging leaflet This is demonstrated in subcostal long-axis or apical sections when angled superiorly and anteriorly from the standard four-chamber view The superior bridging leaflet may sometimes be firmly bound down to the septal crest, with no potential for shunting beneath it This is rare More commonly, the superior bridging leaflet is attached to a normally positioned medial papillary muscle and is additionally attached by multiple cords to the crest of the septum viewed optimally in the modified subcostal en face view (Fig 31.28A; Video 31.11) In the four-chamber and subcostal long-axis sections, the interventricular communication appears to be shielded by a pouch of valvar tissue bulging toward the right ventricle during systole There are multiple interventricular communications through the interchordal spaces, the patterns of flow being recognized with color-flow Doppler This arrangement is often dubbed the Rastelli type A lesion Occasionally the pouch may contain accessory valvar tissue and, as in patients with isolated ventricular septal defects, such a pouch may eventually seal the defect The so-called Rastelli type B defect, in which the papillary muscle in the right ventricle supporting the zone of apposition between the superior bridging and anterosuperior leaflets is positioned in an anomalous position toward the free wall of the right ventricle, may be hard to recognize, particularly when it is associated with a very deep scoop of the muscular ventricular septum or with accessory valvar tissue (Video 31.12) The presence of the so-called Rastelli type C defect, in which the superior leaflet is free-floating, is readily appreciated on the modified subcostal plane viewing the valve en face (Fig 31.28B; Video 31.13) Almost always the interventricular communication is very extensive This pattern is always seen in association with either tetralogy of Fallot (Fig 31.29) or double-outlet right ventricle, and is also frequent in patients with Down syndrome FIG 31.27 Subcostal four-chamber and paracoronal sections showing the variation in size of the interventricular communication below the inferior bridging leaflet (IBL) (A and C) Patient with firm attachment of the IBL to the crest of the ventricular septum, allowing no interventricular shunting under this leaflet (B and D), Large ventricular-level shunting present beneath the IBL (asterisk) The arrow in (D) shows the crest of the muscular interventricular septum relative to the IBL, with chordal attachments from the leaflets rightward aspect la, Left atrium; lv, left ventricle; lvot, left ventricular outflow tract; ml, mural leaflet; ra, right atrium; rv, right ventricle; sbl, superior bridging leaflet FIG 31.28 Modified subcostal images demonstrating the so-called Rastelli A (A) and Rastelli C (B) complete atrioventricular septal defects with common junction The Rastelli A defect demonstrates attachments of the superior bridging leaflet (sbl) to the crest of the muscular interventricular septum (arrow), whereas the Rastelli C defect demonstrates a free-floating superior bridging leaflet with no such attachments lv, Left ventricle; rv, right ventricle