Cor Triatriatum


First reported in 1868, [1cor triatriatum, that is, a heart with 3 atria (triatrial heart), is a congenital anomaly in which the left atrium (cor triatriatum sinistrum) or right atrium (cor triatriatum dextrum) is divided into 2 compartments by a fold of tissue, a membrane, or a fibromuscular band. [234567Classically, the proximal (upper or superior) portion of the corresponding atrium receives venous blood, whereas the distal (lower or inferior) portion is in contact with the atrioventricular valve and contains the atrial appendage and the true atrial septum that bears the fossa ovalis. The membrane that separates the atrium into 2 parts varies significantly in size and shape. It may appear similar to a diaphragm or be funnel-shaped, bandlike, entirely intact (imperforate) or contain 1 or more openings (fenestrations) ranging from small, restrictive-type to large and widely open. See the images below.

Cor triatriatum. Echocardiogram showing the proximCor triatriatum. Echocardiogram showing the proximal chamber (PC) and distal chamber (DC) of the left atrium; the right atrium (RA), left ventricle (LV), and right ventricle (RV) also are shown. Image courtesy of Guido Giordano, MD, Cardiovascular Department, Azienda Ospedaliera Cannizzaro, Catania, Italy.
Cor triatriatum. Image courtesy of Guido Giordano,Cor triatriatum. Image courtesy of Guido Giordano, MD, Cardiovascular Department, Azienda Ospedaliera Cannizzaro, Catania, Italy.
Cor triatriatum. Image courtesy of Guido Giordano,Cor triatriatum. Image courtesy of Guido Giordano, MD, Cardiovascular Department, Azienda Ospedaliera Cannizzaro, Catania, Italy.

In the pediatric population, this anomaly may be associated with major congenital cardiac lesions such as tetralogy of Fallot, double outlet right ventricle, coarctation of the aorta, partial anomalous pulmonary venous connection, persistent left superior vena cava with unroofed coronary sinus, ventricular septal defect, atrioventricular septal (endocardial cushion) defect, and common atrioventricular canal. [8910Rarely, asplenia or polysplenia has been reported in these patients. Although frequently an isolated finding, [1112131415161718cor triatriatum in the adult has been reported in association with ostium secundum atrial septal defect, dilated coronary sinus due to persistent left superior vena cava, and bicuspid aortic valve. [19]

Cor triatriatum dextrum is extremely rare and results from the complete persistence of the right sinus valve of the embryonic heart. The membrane divides the right atrium into a proximal (upper) and a distal (lower) chamber. The upper chamber receives the venous blood from both vena cavae and the lower chamber is in contact with the tricuspid valve and the right atrial appendage.


Cor triatriatum sinistrum

The most popular theory holds that cor triatriatum sinister occurs when the common pulmonary vein fails to incorporate the pulmonary circulation into the left atrium and the common pulmonary venous ostium remains narrow (malincorporation theory). The result is a septum-like structure that divides the left atrium into 2 compartments. However, this theory fails to explain the presence of fossa ovalis and atrial muscle fibers within the walls of the proximal chamber where only a venous wall is supposed to be present. [202122232425262728]

In addition, several cases have been reported in which 1 or 2 pulmonary veins drain into the proximal (accessory) chamber and the others drain directly into the true left atrium. Others believe that the membrane dividing the left atrium is an abnormal growth of the septum primum (malseptation theory) or that the right horn of the embryonic sinus venosus entraps the common pulmonary vein and thereby prevents its incorporation into the left atrium (entrapment theory). The significance of a prominent or persistent left superior vena cava in the pathogenesis of cor triatriatum is unclear.

Cor triatriatum dextrum

During embryogenesis, the right horn of the sinus venosus gradually incorporates into the right atrium to form the smooth posterior portion of the right atrium, whereas the original embryologic right atrium forms the trabeculated anterior portion. The right horn of the sinus venosus and the embryologic right atrium are then connected through the sinoatrial orifice, which has on either side the 2 valvular folds called the right and left venous valves. During this incorporation, the right valve of the right horn of the sinus venosus divides the right atrium in 2. 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 (Chiari network). [2930313233343536]

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.



United States

US epidemiologic statistics regarding cor triatriatum include the following:

  • The incidence of cor triatriatum has been variously reported as 0.1-0.4%.

  • An incidence of 0.4% has been reported at autopsy of patients with congenital cardiac disease.

  • An incidence of 0.2% was reported among patients undergoing transesophageal echocardiography.

  • In high-volume echocardiographic laboratories, the incidence of cor triatriatum is less than 1 in 10,000. However, this is expected to rise with the increasing use of cardiac diagnostic studies. [37]

  • Cor triatriatum dextrum is extremely rare.

  • Cor triatriatum sinistrum can be misdiagnosed as other common cardiac or pulmonary conditions such as bronchial asthma or mitral stenosis.


The morbidity and mortality of cor triatriatum sinistrum is high in those who are symptomatic in infancy. This is due to the severely restrictive opening in the accessory membrane and the association with major cyanotic or acyanotic congenital heart lesions. Mortality may exceed 75% in untreated symptomatic infants.

Significant sequelae is unusual with cor triatriatum dextrum as it is not commonly associated with life-threatening symptoms or major congenital cardiac defects.


No clear difference has been noted in incidence or clinical presentation among men or women.


In symptomatic infants, cor triatriatum sinistrum is often associated with other major congenital cardiovascular defects.

In the adult, cor triatriatum sinistrum can be as follows:

  • Asymptomatic (found incidentally on cardiac imaging)

  • An isolated finding with a large nonrestrictive communication between the superior and inferior left atrial chambers

  • Associated with minor congenital defects such as patent foramen ovale, atrial septal defect, or persistent left superior vena cava

Cor triatriatum dextrum can be diagnosed at any age, especially if incidentally discovered. Other congenital cardiac defects, such as atrial septal defect, may be present and demand evaluation. Cor triatriatum can also be misdiagnosed as other common cardiac conditions such as constrictive pericarditis.

The cross-sectional area of the fenestration within the accessory membrane likely remains unchanged with aging. Late presentation of symptomatic disease is, thus, related to the additive effects of other cardiac conditions, such as mitral regurgitation or atrial fibrillation.

Clinical Presentation


Cor triatriatum sinistrum

This is classified based on the size and the number of the openings in the accessory membrane into the left atrium. The most commonly used classification is the one developed by Loeffler in 1949. According to that classification, cor triatriatum is divided into 3 distinct groups: type 1 has no opening in the accessory membrane, with the proximal left atrium draining into the right atrium; type 2 has one or more small restrictive openings (fenestrations), resulting in significant left ventricular inflow obstruction; and type 3 has a large (nonrestrictive) opening in the membrane. [24No opening or 1 or more restrictive opening is commonly seen in the newborn, infants, and children. In the adult, cor triatriatum often contains a relatively wide opening.

Clinical manifestations depend upon the size of the opening in the septum and the presence of associated congenital cardiac defects. In most patients, the opening is severely restrictive and produces symptoms similar to those of severe mitral stenosis. In the adult, clinical manifestations are often delayed due to the presence of a large opening.

In asymptomatic patients, a heart murmur may be detected. Cor triatriatum may be detected as an incidental finding on routine cardiac imaging.

In symptomatic patients, the transition from asymptomatic to symptomatic in the adult occurs mainly because of fibrosis and calcification of the orifice in the accessory membrane or development of mitral regurgitation and/or atrial fibrillation. Symptoms include the following:

  • Exertional dyspnea

  • Effort intolerance and easy fatigability

  • Hemoptysis

  • Orthopnea

  • Palpitation (atrial fibrillation)

  • Signs of systemic embolism

  • Systemic thromboembolism (especially in those with atrial fibrillation and/or restrictive orifice, as both conditions promote thrombus formation in the left atrium)

Cor triatriatum dextrum

Clinical presentation depends on the following:

  • The degree of septation of the right atrium

  • Size of the sinoatrial orifice

In asymptomatic patients, incidental findings occur during the following:

  • Cardiac imaging studies

  • Right heart catheterization

  • Surgery for other cardiac defects

  • Postmortem examination

  • Palpitation (recurrent supraventricular arrhythmias)

  • Increased abdominal girth (ascites)

  • Swelling of the lower extremities (edema)


Cor triatriatum sinistrum

Findings related directly to the presence of a restrictive accessory atrial membrane include the following:

  • Murmur

  • Pulmonary congestion

  • Tachypnea

  • Respiratory distress

  • Pulmonary rales

  • Pleural effusion

  • Hypoxemia

Pulmonary hypertension may be noted as a loud second component (P2) of the second heart sound.

Right ventricular failure may manifest with the following:

  • Elevated jugular venous pressure

  • Right ventricular heave

  • Tricuspid regurgitation (systolic murmur along sternal border with respiratory variations in intensity, prominent V wave in jugular venous pulsation)

  • Right upper quadrant abdominal tenderness due to liver congestion

  • Hepatomegaly

  • Jaundice

  • Ascites

  • Peripheral edema

Tachycardia may have the following presentation:

  • Sinus rhythm

  • Rapid irregular heart rate (frequent premature atrial complexes, atrial fibrillation with rapid ventricular response)

There may be findings related to associated cyanotic or acyanotic congenital cardiac defects.

Cor triatriatum dextrum

Signs include the following:

  • Heart murmur

  • Elevated jugular venous pressure

  • Abdominal tenderness (hepatic congestion)

  • Ascites

  • Peripheral edema

Diagnostic Considerations

Diagnosis of cor triatriatum is frequently made with considerable delay due to rarity of the condition and presenting signs and symptoms that mimic other more common cardiac or pulmonary disorders.

Cough and hemoptysis may be attributed to other potential causes such as bronchitis, pulmonary tuberculosis, or malignancy.

The rarity of cor triatriatum has lead to frequent misdiagnosis of the condition as bronchial asthma, primary or secondary pulmonary hypertension, or mitral stenosis. [727374]

A high index of suspicion can prevent delayed diagnosis and unfavorable outcomes. [72]

Cor triatriatum sinistrum

Consider the following conditions in patients with suspected cor triatriatum sinistrum:

  • Bronchial asthma

  • Pulmonary vein stenosis

  • Pulmonary veno-occlusive disease

  • Supravalvular mitral ring

  • Atrial tumors

Cor triatriatum dextrum

Consider the following conditions in patients with suspected cor triatriatum dextrum:

  • Prominent Chiari network

  • Right atrial tumor (particularly right atrial myxoma)

  • Inferior vena cava (obstruction) syndrome

  • Diagnostic Considerations

  • Diagnosis of cor triatriatum is frequently made with considerable delay due to rarity of the condition and presenting signs and symptoms that mimic other more common cardiac or pulmonary disorders

Differential Diagnoses

Laboratory Studies

Cor triatriatum sinistrum


Electrocardiographic (ECG) findings include the following:

  • Sinus rhythm

  • Frequent atrial premature complexes

  • Left and/or right atrial abnormality

  • Right axis deviation

  • Right ventricular hypertrophy and strain pattern

Right heart catheterization

Findings include elevated right atrial, right ventricular, pulmonary arterial, and pulmonary artery wedge pressure and the following:

  • Right atrial mean pressure greater than 5 mm Hg

  • Right ventricular pressure greater than 30/5 mm Hg

  • Pulmonary arterial pressure greater than 30/12 mm Hg at rest or worsening pulmonary arterial pressure during exercise [39]

  • Pulmonary artery wedge (left atrial) pressure greater than 12 mm Hg

  • Diastolic pressure gradient between pulmonary capillary wedge pressure and left ventricular end diastolic pressure [37]

  • Prominent V wave in right atrial pressure tracing (due to tricuspid regurgitation)

  • Delay in visualization of the distal left atrial chamber in the venous phase of right ventricular (pulmonary arterial) angiography [37]

Left heart catheterization

There is normal left ventricular and central aortic pressure. Systemic hypotension may be present if the left atrial membrane is restrictive and stroke volume is reduced as the result.

Coronary angiography

Coronary artery disease or coronary artery anomalies may be independently found but are not a part of the usual presentation of cor triatriatum.

Cor triatriatum dextrum

There are no pathognomonic ECG findings in isolated cor triatriatum dextrum. Right heart catheterization may reveal elevated pressure in the proximal right atrial chamber with a gradient across the accessory membrane.

Imaging Studies

Cor triatriatum sinistrum

Chest radiography, computed tomography scanning, and magnetic resonance imaging

Chest x-ray findings include the following:

  • Enlarged atrium

  • Cardiomegaly

  • Pulmonary congestion

  • Prominent pulmonary arteries

  • Pleural effusion

Cardiac CT scanning and cardiac MRI have been used for evaluating patients with suspected cor triatriatum. [53The results include multiple case reports of a successful diagnosis. [5455]


Angiographic diagnosis has been reported, with a successfully established diagnosis in about 50% of the cases. Angiography may help determine the severity of obstruction to left ventricular filling and assess magnitude of pulmonary hypertension


Echocardiography is the most commonly used imaging technique and the modality of choice for the diagnosis of cor triatriatum [2932404142434445464748495051Although the diagnosis is commonly suspected on transthoracic study, transesophageal echocardiography (TEE) is frequently needed to precisely define the anatomy of the membrane, its relation to other structures, and the pulmonary venous drainage pattern.

Echocardiography allows the following:

  • Assessment of atrial morphology

  • Evaluation of characteristic anatomic relations

  • Determination of resultant flow disturbances

  • Detection of associated anomalies

  • Assessment of hemodynamic significance of the lesion

The typical cor triatriatum sinistrum appears as a membrane attached laterally to the junction of the left upper pulmonic vein and left atrial appendage, dividing the left atrium into 2 chambers. The proximal chamber receives blood from the pulmonary veins and the distal chamber contains the left atrial appendage and mitral valve. One or more fenestrations of varying sizes connect the 2 chambers.

Unlike mitral stenosis where only a diastolic flow across the stenotic valve is present, flow across the (restrictive) accessory membrane in cor triatriatum occurs both in diastole and systole. [52]

Three-dimensional reconstruction of echocardiographic images has been used and appears to improve the definition of the accessory membrane, detection of fenestrations, and identification of the relationship of the membrane to surrounding structures. [19]

Intracardiac echocardiography has been shown to have demonstrated presence of cor triatriatum in 1 patient.

Frequently reported associated findings on cardiac imaging for cor triatriatum sinistrum include the following:

  • Patent foramen ovale

  • Atrial septal defect (secundum-type and primum-type) [56]

  • Partial anomalous pulmonary venous return (also called subtotal cor triatriatum sinister): Occurs in nearly one fourth of the cases; the pulmonary veins may drain into the coronary sinus, superior vena cava, left superior vena cava, directly into the right atrium, or into the innominate vein.

  • Left ventricular dilation (due to chronic mitral regurgitation of poorly defined cardiomyopathy)

  • Right ventricular dilation

  • Pulmonary hypertension

  • Tricuspid regurgitation

  • Persistent left superior vena cava with or without unroofed coronary sinus

  • Partial or complete atrioventricular canal defect

  • Mitral regurgitation

  • Ascending aortic aneurysm with or without dissection or aortic regurgitation

Cor triatriatum dextrum

In general, advanced cardiac imaging (transthoracic and transesophageal echocardiography, cardiac MRI, and right ventriculography) demonstrates the presence of a membrane within the right atrium and may also be diagnostic of other concomitant congenital or acquired cardiac abnormalities. [40414243444546474850535457585960]

See the videos below for imaging studies of cor triatriatum.

Cor triatriatum. This film shows the classic pattern of pulmonary edema associated with pulmonary overcirculation and pulmonary venous obstruction. Patient has an anomalous pulmonary venous connection that was only obvious after a pulmonary artery shunt. The particular radiograph is not a patient with cor triatriatum, but appearance of prominent pulmonary vascularity is the same. Movie courtesy of Guido Giordano, MD, Cardiovascular 

Department, Azienda Ospedaliera Cannizzaro, Catania, Italy.

Treatment & Management

Medical Care

Medial care for symptomatic patients with cor triatriatum includes the following:

  • Stabilize hemodynamics by control of hypoxemia, fluid overload, and pulmonary congestion

  • Control ventricular rate in patients with atrial fibrillation

  • Anticoagulation prophylaxis against deep vein thrombosis and pulmonary embolism in those with right-sided heart failure

  • Full anticoagulation in those with atrial fibrillation

Obtain a surgical consultation.

Cor triatriatum dextrum

For cor triatriatum dextrum, observation alone is appropriate in asymptomatic patients. In others, control of fluid retention and rate-control of atrial arrhythmias may be required. Percutaneous technique of balloon septostomy of the accessory membrane has been reported.

Surgical Care

Symptomatic patients with cor triatriatum who have significant gradient across the membrane benefit from surgical repair. [52Surgical resection of the accessory membrane has been successful. [616263646566676869]

Complete resection of the membrane and closure of the atrial septum with a pericardial patch is a common approach. Associated congenital defects need to be corrected at the same time.

A study by Saxena et al indicated that surgery for cor triatriatum results in satisfactory rates of early and long-term survival. The study involved 25 patients in whom the cor triatriatum membrane was excised using cardiopulmonary bypass, with 20 of these patients also undergoing concomitant surgical procedures. The 10-year survival rate, using the Kaplan-Meier estimate, was 83%; at a mean follow-up of 12.8 years, all patients had a New York Heart Association classification of I or II. The investigators found that patients in whom cor triatriatum coexists with complex congenital anomalies may be at greater risk for adverse outcomes. [70]


Obtain cardiology consultation for medical management and echocardiographic, hemodynamic, and angiographic evaluation.

Obtain a radiology consultation for advanced cardiac imaging with computerized tomography or cardiac magnetic resonance techniques.

Diet and Activity

A low-salt diet is appropriate in those with significant fluid retention.

Bed rest is appropriate in symptomatic patients with pulmonary congestion or significant right-sided heart failure and pulmonary hypertension

Medication Summary

The medical management of cor triatriatum is targeted towards the associated elevation in pulmonary vascular resistance and heart failure. It is continued in the postoperative period until resistance falls and right ventricular performance improves. The mainstays of treatment are inotropic agents and diuretics.

Inotropic agents

Class Summary

Provide myocardial support in the perioperative period for patients with right heart failure. The more restrictive the connection between the proximal and distal chambers, the more likely inotropic support will be required. A number of agents are available in this category. Adrenergic agonists increase myocardial contractility in patients with heart failure.

Digoxin (Lanoxin)

Exerts inotropic action by increasing amount of intracellular calcium available during excitation-contraction coupling. One of numerous inotropic agents used in infants with congenital cardiac defects. Other agents, such as dopamine, are more appropriate for the acute management of heart failure in the ICU setting.

Dopamine (Intropin)

Adrenergic agonists often are used in the critical care setting for rapid onset of action and rapid time to peak effect. Are much easier to titrate to effect in acute setting. Half-life is much shorter than digoxin, and effects are rapidly lost when drug is discontinued.

Loop diuretics

Class Summary

Management of right heart failure and pulmonary edema.

Furosemide (Lasix)

Highly effective first-line drug for diuresis in newborns and infants. Sulfonamide derivative that exerts effects on loop of Henle and distal renal tubule, inhibiting reabsorption of sodium and chloride.


Class Summary

These agents are used in the prophylaxis and treatment of thromboembolic disorders.


Augments activity of antithrombin III and prevents conversion of fibrinogen to fibrin. Does not actively lyse but is able to inhibit further thrombogenesis. Prevents reaccumulation of clot after spontaneous fibrinolysis.

Warfarin (Coumadin)

Most commonly used oral anticoagulant. Interferes with hepatic synthesis of vitamin K-dependent coagulation factors; used for prophylaxis and treatment of thromboembolic disorders


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