Cor Triatriatum: A Tale of Two Membranes
Highlights
- Cor triatriatum is a very rare congenital cardiac anomaly with a reported incidence of 0.1% of all congenital heart defects., There are two types of cor triatriatum; dexter involves right atrial division, and sinister involves left atrial division (View Highlight)
- In cor triatriatum dexter, the right atrium is divided into two chambers by exaggerated fetal Eustachian and Thebesian valves, as a remnant from poor regression of the right valve of the right horn of the embryologic sinus venosus, which come together to form an incomplete septum across the lower part of the atrium (View Highlight)
- In cor triatriatum sinister, the left atrium is divided into two chambers by a fibromuscular septum, with the pulmonary veins entering a posterior-superior chamber separated from the anterior-inferior distal chamber containing the mitral valve. The embryologic origin of this defect remains controversial, with two different theories, the malincorporation and entrapment theories. (View Highlight)
- It is important to differentiate the cor triatriatum sinister membrane from a supravalvar mitral ring, and the left atrial appendage is used as an anatomic landmark. The cor triatriatum sinister membrane is seen above the left atrial appendage, and almost always the pulmonary veins drain into the superior chamber. The supravalvar mitral ring is seen below the left atrial appendage and just above the mitral valve annulus (View Highlight)