Cor triatriatum sinister (CTS) accounts for <0.1% of all congenital heart diseases. It is a condition in which the fibromuscular membrane divides the left atrium (LA) into 2 chambers.1 The superior and posterior chambers receive the pulmonary veins, and the inferior and anterior chambers are connected to the left atrial appendage and mitral orifice.2 Pathophysiologically, CTS is similar to mitral stenosis,3 and the symptoms are correlated with pulmonary venous congestion and pressure loading at the right side of the heart.
