Fenestrated cor triatriatum sinistrum: a case report.

We present a 20-year-old male patient with cor triatriatum sinistrum with fenestrations and long-standing dyspnea on exertion, fatigue, and palpitation. An apical early to mid-systolic murmur of grade I-II/VI was heard on cardiac auscultation. Electrocardiography showed sinus rhythm and an incomplete right bundle branch block. Transthoracic echocardiography showed a membrane dividing the left atrium into two compartments. Transesophageal echocardiography showed a membrane with fenestrations originating from the left upper pulmonary vein, extending to the interatrial septum, and dividing the left atrium into two compartments as proximal and distal. Cardiac MR imaging for further detailed anatomical assessment demonstrated similar findings without additional anomaly. Medical follow-up was conducted due to no pressure gradient across the membrane.