Cor Triatriatum Sinister in Adulthood: A Rare Clinical Encounter

Cor triatriatum sinister (CTS) is a rare congenital anomaly characterized by a fibromuscular membrane that divides the left atrium into proximal and distal chambers. Typically, the pulmonary veins drain into the proximal chamber, while the distal chamber remains continuous with the left atrial appendage and the mitral valve. Communication between the two chambers occurs through one or more fenestrations of variable size. We report the case of a 61-year-old woman with a history of atrial flutter status post-ablation and atrial septal defect repair in infancy, who was incidentally found to have CTS on multimodal imaging. In the absence of hemodynamic compromise or CTS-related symptoms, conservative management was deemed appropriate. This case highlights the value of contemporary imaging modalities in the incidental detection of congenital anomalies in adults and emphasizes the need for individualized management strategies.