Cor Triatriatum

Cor triatriatum is a rare congenital heart condition where a child is born with a thin, fibromuscular, often fenestrated membrane subdividing the left or right atrium into 3 chambers (see Image. Cor Triatriatum Sinistrum). This condition was classified by Praagh et al into 3 types:

1. Cor triatriatum sinister: The left cor triatriatum is the most common form, albeit very rare. The left atrium is divided by a fibromuscular band into an upper (pulmonary venous) and a lower (vestibular) compartment. The upper compartment receives blood from the pulmonary veins, and the atrial appendage is typically part of the lower compartment. This arrangement of cor triatriatum sinister is crucial in the differential diagnosis, particularly from conditions such as supravalvular mitral valve stenosis. According to the degree of blood flow impedance, the fibromuscular membrane can create significant left ventricular inflow obstruction and substantial pulmonary hypertension.

1. Cor triatriatum dextrum: The right valve of the sinus venosus persists, dividing the right atrium into 2 chambers. Cor triatriatum dextrum presents similarly to the Ebstein anomaly and is challenging to differentiate from it based on clinical features only.

1. Cor triatriatum intermedium: A largely theoretical entity that may occur due to a persistent interseptovalvular space. Thilenius et al first described this anomaly in 1976 as type C. Nevertheless, no real-life cases of a third intermediary atrial chamber have been reported in the surgical literature.