Discussion:
UCSS is a rare CHD representing less than 1% of all ASD types (1). Its clinical manifestation is atypical, and may be associated with varied CHDs (6). Preoperative diagnosis by TTE is very difficult when associated with PLSVC (2, 6). In our patient, the diagnosis of associated PLSVC was missed preoperatively, and was detected intraoperatively, and this had led to change in the surgical plan. Our surgical approach was to create an intra-atrial tunnel to divert the flow of PLSVC into RA with great attention to the pulmonary veins and the mitral valve, and repair the ASD with fresh autologous pericardial patch . Other operative options include: ligating PLSVC and repairing the ASD; constructing a baffle to guide PLSVC towards RA (6). We confirm the importance of precise preoperative diagnosis to avoid any complications from such an incidental intraoperative finding.