•Cor triatriatum dexter results from persistence of the right valve sinus venosus.•A 3D evaluation can help differentiate CTD other congenital abnormalities.•Treatment options for include surgery, first line, or percutaneous resection. Cor (triatrial heart) is a rare abnormality in which either left atrium (cor sinister) (RA; cor [CTD]) divided into 2 separate chambers. The was described 1860s ...