Echocardiographic Features Defining Right Dominant Unbalanced Atrioventricular Septal Defect: A Multi-institutional Congenital Heart Surgeons’ Society Study

Background—Definition and management of right dominant unbalanced atrioventricular septal defect (AVSD) remains challenging because unbalance entails a spectrum of left heart hypoplasia. Previous work has highlighted atrioventricular valve (AVV) index as a reasonable defining echocardiographic measure. We sought to assess which additional echocardiographic features might provide further characterization. Methods and Results—From a multi-institutional cohort of complete AVSD, 52 preoperative echocardiograms of patients with presumed right dominant unbalanced AVSD (based on AVV index) and 60 randomly selected preoperative echocardiograms from patients with presumed balanced AVSD were reviewed. Cluster analysis of echocardiographic variables was used to group patients with similar features. Discriminant function analysis was used to explore which variables differentiated these groups. Three groups were identified from the cluster analysis. Echocardiographic variables that differentiated these groups were right ventricle:left ventricle inflow angle, LV width/LV length, left AVV color diameter at smallest inflow, left AVV color diameter at annulus, right AVV overriding left atrium, and LV width. Based on procedures and outcomes, 1 group likely represented balanced patients, whereas 2 groups with similar outcomes likely represented unbalanced patients. The dominant differentiating echocardiographic variable between the 3 cluster groups was the right ventricle:LV inflow angle (partial R2=0.86), defined as the angle between the base of the right ventricle and LV free wall, using the crest of the ventricular septum as apex of the angle. Conclusions—The angle of right ventricle/LV inflow and other surrogates of inflow may be important defining echocardiographic measures of right dominant unbalanced AVSD, although confirmation is needed.