An unusual tethering of the bridging leaflets in atrioventricular septal defect producing a communication from left atrium to right ventricle

We describe a 39-year-old woman who was diagnosed as having an unusual atri oventricular septal defect with a communication from left atrium to right v entricle. A common atrioventricular junction, with partially separated righ t and left atrioventricular orifices, was found at transoesophageal ultraso nic examination. Both bridging leaflets were attached to the underside of t he atrial septum, which was grossly malaligned relative to the ventricular septum. The shunt was exclusively from left atrium to right ventricle becau se of the overriding of the left atrioventricular valve, with the left comp onent of the inferior bridging leaflet firmly fused to the ventricular sept al crest.