Cor triatriatum

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]

Cor triatriatum is a rare congenital heart defect where a fibromuscular septum subdivides the left atrium into two chambers. Associated cardiovascular malformations are common and include atrial septal defect,patent ductus arteriosus and common atrioventricular canal. The proximal or accessory chamber lies posteriorly, and usually receives blood from each of the pulmonary veins. The distal or true left atrial chamber lies anterior, connects to the left atrial appendage,empties into the left ventricle through the mitral valve, and lodges true atrial septum containing fossa ovalis . The two atrial chambers communicate through an opening in the membrane which divides the two chambers. This opening may be single and stenotic, fenestrated, and either small or large. ^[1]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]

During fetal development, a cor triatriatum defect results in a deviation in the formation of the left atrial chamber. This section serves to explain the anatomy of a cor triatriatum defect.

The pulmonary veins enter the proximal left atrial chamber and are separated from distal left atrial chamber by a diaphragm. A small hole in this diaphragm allows some communication to the distal chamber. The right ventricle is enlarged. The fossa ovalis is patent, which allows left-to-right shunting. This interatrial connection usually communicates with the proximal chamber of the right atrium and occasionally the distal chamber communicates with the right atrium. The distal chamber contains the mitral valve and the left atrial appendage.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]

Cor triatriatum is a very rare congenital heart disease. The sex ratio is nearly equal in occurrence. The overall incidence and prevalence is low.

The incidence ranges from approximately 0.1% to 0.4% of all infants with congenital heart disease. The male to female ratio is 1.4:1. Echocardiography laboratory reports show that the incidence is less than in 1 in 10,000 cases.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]

Cor triatriatum is a rare and often devastating condition to untreated infants. However, patient as much as 72 years old have been found to have the condition in routine pre-procedural transesophageal echocardiography^[1]. Prognosis is largely dependent on the administration of effective surgical intervention in a timely manner, the nature of the obstruction between the atrial chambers, and the presence or absence of associated defects/anomalies.

• Low Cardiac Output
• Hypoxemia
• Atrial Fibrillation
• Pulmonary Venous Hypertension
• Right Ventricular Failure

Cor triatriatum is usually fatal within the first two years of life. The prognosis is related to timely surgical intervention, the degree of obstruction between the two left atria, and the presence or absence of associated anomalies. The majority of postoperative deaths occur in the first 30 days.

Long-term results are excellent, with survival of more than 80% in patients surviving surgery.

Survivors have excellent functional results without residual sequelae and a life expectancy that approaches the general population.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]

As with many congenital heart diseases, the causation of cor triatriatum has not been definitively proven. A number of theories exist to explain how this defect occurs including: Malincorporation theory, Malseptation theory, and the Entrapment theory. During pregnancy, both genetic disease and environmental factors such as viral infection and poor nutrition may play role to develop Cor triatriatum in fetus.

It has been hypothesized that cor triatriatum sinister occurs when the common pulmonary vein fails to incorporate the pulmonary circulation into the left atrium. As a result, the common pulmonary venous ostium remains narrow. The anatomic result is a septumlike structure that divides the left atrium into two compartments. However, this theory fails to explain the following:

1. The presence of the fossa ovalis and atrial muscle fibers within the walls of the proximal chamber where only a venous wall should be present.
2. Furthermore, several cases have been reported in which 1 or 2 pulmonary veins drain into the proximal (or accessory) chamber and the others drain directly into the true left atrium.

A second alternate hypothesis is that the membrane dividing the left atrium is an abnormal growth of the septum primum.

A third hypothesis asserts that the right horn of the embryonic sinus venosus entraps the common pulmonary vein and thereby prevents its incorporation into the left atrium.

The significance of a prominent or persistent left superior vena cava in the pathogenesis of cor triatriatum is unclear.

In normal development, the right horn of the sinus venosus is gradually incorporated into the right atrium. This forms the smooth posterior portion of the right atrium. The original embryologic right atrium ultimately becomes the trabeculated anterior portion of the right atrium.

The embryologic right atrium and the right horn of the sinus venosus are then connected through the sinoatrial orifice. The sinoatrial orifice is surrounded on either side by the two valvular folds (the right and left venous valves). The right atrium is divided in two by the right horn of the sinus venosus. This right valve forms a sheet that serves to direct the oxygenated venous return from the inferior vena cava across the foramen ovale to the left side of the heart during fetal life as the Chiari network.

Normally, this network regresses and leaves behind the crista terminalis superiorly and the eustachian valve of the inferior vena cava and the thebesian valve of the coronary sinus inferiorly.

Complete persistence of the right sinus valve of embryonic life results in separation of the smooth and trabeculated portions of the right atrium and constitutes cor triatriatum dextrum. If this membrane is extensively fenestrated and weblike in appearance, then it is referred to as the Chiari network.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editors-In-Chief: Priyamvada Singh, M.B.B.S. [2]; Cafer Zorkun, M.D., Ph.D. [3]; Keri Shafer, M.D. [4]; Assistant Editor(s)-In-Chief: Kristin Feeney, B.S. [5]

During diagnosis, it is crucial to identify and rule out similar conditions to cor triatriatum. This page serves as a reference for the basis of a cor triatriatum differential diagnosis from other cardiac conditions.

• Mitral Stenosis (Supravalvular Ring)
• Partial Anomaly of Pulmonary Venous Connection
• Idiopathic Pulmonary Hypertension
• Persistent Pulmonary Hypertension in newborn
• Pulmonary Hypoplasia
• Total Anomalous Pulmonary Venous Connection

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