Cor triatriatum sinister with an intact interatrial septum and a decompressing vein in a toddler.

Cor triatriatum sinister is a very rare cardiac anomaly that may lead to pulmonary hypertension, right ventricular dilation, and eventually right heart failure. We report a case of a toddler who presented with respiratory distress and cardiomegaly and was found to have cor triatriatum sinister with a restrictive communication, decompressing vertical vein, pulmonary hypertension, severe tricuspid regurgitation, and severe right ventricular dysfunction. She underwent a successful surgical repair, with normalisation of right ventricular function and pulmonary artery pressure.