Ono M, et al. - This study aimed at assessing the mechanisms of atrioventricular valve (AVV) regurgitation in single ventricle and their influence on outcomes after total cavopulmonary connection (TCPC). There appeared a frequent association of AVV regurgitation in univentricular heart with a tricuspid or a common AVV, and structural anomalies were the primary cause. Significant AVV regurgitation requiring surgery influenced survival following TCPC, especially when AVV replacement was required. As per the mechanisms of regurgitation, surgical management seemed mandatory.