Pseudo Cor Triatriatum Sinistrum due to Dilated Coronary Sinus in Association with Supramitral Ring

We herein describe a 34-year-old woman with a persistent left superior vena cava (PLSVC) impinging on the posterior wall of the left atrium, subdivided by a membrane at the distal part of the impingement. In this patient, a much dilated coronary sinus due to the PLSVC resulted in a membrane-like structure in the posterior wall of the left atrium with the appearance of the cor triatriatum in transthoracic echocardiography (ie, a pseudo cor triatriatum). Although the PLSVC is a common malformation of the superior systemic vein, its aforementioned presentation is rare.