Cor triatriatum Cor triatriatum dexter 2012-04-08T08:02:56Z Cor triatriatum dextrum UMLS:C0344697 Fyler:2854 A congenital anomaly with partitioning of the right atrium to form a triatrial heart caused by persistence of the right valve of the sinus venosus. Typically, the right atrial partition is due to exaggerated fetal eustachian and thebesian valves, which together form an incomplete septum across the lower part of the atrium. This septum may range from a reticulum to a substantial sheet of tissue. SNOMEDCT_US:274947007 Cor triatriatum dexter is a Latin phrase meaning that the heart (cor) has three atria (triatriatum) whereby the 'third' atrium is on the right (dexter) side. HP:0011566