Abstract
Ninety two patients with both atrioventricular valves attached to the atrial septum, roofing a perimembranous inlet ventricular septal defect, were assessed by cross-sectional echocardiography. In the group, 42 had an isolated perimembranous inlet ventricular septal defect, 31 had atrioventricular discordance, nine an atrioventricular septal defect with intact interatrial septum, and 10 a straddling atrioventricular valve. In all but those with an atrioventricular septal defect the left atrioventricular valve had the appearance of a morphologically mitral valve. In the former lesion the atrioventricular junction was "sprung" and a cleft between the anterior and posterior bridging leaflets was identified in all. A straddling valve was identified by tensor apparatus from one atrioventricular valve in both ventricular chambers. Atrioventricular discordance was diagnosed by identifying the systemic and pulmonary venous atria and then assessing the morphology of the draining atrioventricular valves. Thus, with cross-sectional echocardiography, the constellation of abnormalities that give rise to lack of offsetting of the atrioventricular valves can be reliably identified.