Introduction

Atrioventricular (AV) septal defects are described as a deficiency of the atrioventricular septum, varying from a simple ostium primum atrial septum defect (ASD I) to a complete AV septum/canal defect with a shared valve.[1],[2] Within the family of AV canal defects, also known as endocardial cushion defects, lies a subset of defects – termed unbalanced AV canal defects, which make up to 7–15% of all AV canal defects. The term “unbalanced” describes the abnormal location of the atrioventricular valve predominantly overlying one ventricle, with hypoplasia of the non-dominant ventricle.[3],[4][5] Surgical correction of unbalanced defects remain challenging and ranges from biventricular repair to univentricular palliation.[6]