[Incidental diagnosis of cor triatriatum sinister in a young woman].

Cor triatriatum sinister (CTS) is a rare congenital heart defect, with an estimated incidence of 0.1-0.4% of all congenital heart defects, characterized by the presence of a fibromuscular septum that divides the left atrium into two chambers. We report the case of a 37-year-old woman with an incidental diagnosis of CTS during hospitalization for chest pain. Transthoracic echocardiography revealed a left intra-atrial membrane without hemodynamic significance, subsequently better characterized by transesophageal echocardiography, which ruled out the presence of a significant gradient and associated cardiac anomalies, including atrial septal defects. The patient was classified in Loeffler group III due to the presence of extensive patency of the membrane associated with a non-significant transmembrane gradient. In the absence of hemodynamically significant obstruction and associated congenital heart disease, the natural history is generally favorable. In asymptomatic patients, a conservative approach is adopted, involving clinical and instrumental follow-up and control of risk factors. However, in light of the risk of atrial fibrillation and cardioembolic events, long-term arrhythmia monitoring is indicated. This case highlights the role of echocardiographic imaging in the diagnosis and risk stratification of CTS in adults.