Although most adults after ASO are well, and few have residual defects, there are subgroups, particularly those who needed further cardiac intervention in childhood, who are at higher risk for ventricular and valve dysfunction and arrhythmias.

Background-Although identification of unbalanced atrioventricular septal defect (AVSD) is obvious when extreme, exact criteria to define the limits of unbalanced are not available. We sought to validate an atrioventricular valve index (AVVI) (left atrioventricular valve area/total atrioventricular valve area, centimeters squared) as a discriminator of balanced and unbalanced forms of complete AVSD and to characterize the association of AVVI with surgical strategies and outcomes. Methods and Results-Diagnostic