Unrecognized Atrial Septal Defect Presenting with Postoperative Occipital Infarction.

A 49-year-old woman developed acute homonymous hemianopia three days after elective surgery. Neuroimaging confirmed an embolic right occipital infarction. Transthoracic echocardiography demonstrated early bubble passage, and transesophageal imaging identified a 4.6 mm ostium secundum atrial septal defect. The defect was successfully closed percutaneously with complete shunt resolution. This case emphasizes the value of targeted multimodality imaging in uncovering occult interatrial shunts and highlights presumed paradoxical embolism as a potential mechanism of postoperative or cryptogenic stroke.