Two rare cases of congenital aortic stenosis showing a discrepancy between preoperative imaging diagnosis, intraoperative findings, and histopathological diagnosis.

Unicuspid aortic valve (UAV) is an extremely rare congenital heart valve abnormality while bicuspid valve (BAV) has been reported as one of the most common cardiac anomalies. With a UAV usually showing similar presentations to a BAV, such as aortic regurgitation or aortic stenosis (AS), it is challenging to differentiate them from each other in clinical settings. Despite some features shared between both valve disorders, there can be a clinical significance in distinguishing UAV from BAV for the management of patients with these heart anomalies. Herein, we describe two cases where patients with hemodynamically severe AS were diagnosed with BAV and UAV, respectively based on preoperative examinations and intraoperative findings, but subsequent pathological examinations confirmed the opposite diagnosis in both cases. <Learning objective: Preoperative diagnosis of congenital aortic valve diseases can often be challenging. There remains a remarkable number of misleading cases. Thus, it is strongly recommended that an accurate diagnosis should be attempted at the earliest stages of congenital aortic valve disease. Additionally, both careful follow-ups using multiple imaging modalities and confirmations via pathological diagnosis for patients undergoing surgery, if they are first found to be at an advanced stage or remain undiagnosed preoperatively are important.>.