Assessment of atrioventricular septal defects by two dimensional echocardiography.

Ninety-six patients with an atrioventricular septal defect were assessed by two dimensional echocardiography. Forty-eight patients were judged as having two discrete valve orifices. In this group, 37 had an intact ventricular septum and 11 a ventricular septal defect. Two patterns of attachment of the valve leaflets to the interventricular septum were noted. Forty-eight patients had a common valve orifice. In 29 patients there was absence of tethering of the anterior bridging leaflet to the interventricular septum. A further 19 had varying degrees of tethering of the anterior bridging leaflet. A ventricular septal defect was identified under the anterior bridging leaflet in all cases. In 58 cases where the posterior bridging leaflet was identified, a ventricular septal defect was visualised in eight and missed in two. Seventy-eight patients had an ostium primum defect, 12 a common atrium, and a further six an intact interatrial septum. Two dimensional echocardiography provides in depth morphological information about the type of atrioventricular defect and can correctly identify the presence of a ventricular septal defect beneath the anterior or posterior bridging leaflet, unless it exists between short crowded chordae.