Cor triatriatum

Basics

Description

In this congenital anomaly, a fibromuscular membrane separates the left atrium into a posterior chamber (common pulmonary vein) communicating with the pulmonary veins, and an anterior chamber communicating with the mitral valve and the left atrial appendage.
The presence of the atrial appendage in the anterior chamber is the feature distinguishing cor triatriatum from the supramitral ring.
In the classic form, pulmonary venous chamber flow enters the mitral inflow chamber through one or several small communications. There is resultant restriction of the pulmonary venous return to the systemic circulation with secondary pulmonary HTN.

An atrial septal defect is seen in 70-80% of cases, and the communication is typically at the level of the anterior chamber, often at the foramen ovale.
A decompressing opening between the common pulmonary vein and the right atrium is extremely rare.
Other congenital lesions occur in 24-80% of reported cases. The "classical" form of cor triatriatum has no associated defects.

Epidemiology

Prevalence
Cor triatriatum is a rare cardiac anomaly. This diagnosis was made in 0.01-0.22% of patients in different surveys of children with congenital heart disease. The prospective Bohemian study reported a prevalence of 0.006/1,000 live births.

Risk Factors

No known risk factors
Genetics
No known genetic transmission

Pathophysiology

Failure of complete incorporation of the common pulmonary vein into the left atrium or stenosis of the common pulmonary vein is the most accepted embryological basis for cor triatriatum. Total lack of incorporation results in total anomalous pulmonary venous connections.

Etiology

No known etiology

Associated Conditions

Very rare reports of associated noncardiac lesions

Diagnosis

Signs and symptoms depend on the severity of functional pulmonary venous obstruction and secondary increased pulmonary pressures. Only signs and symptoms for classical cor triatriatum will be included here.

History

Patients with mild obstruction may be asymptomatic.
The great majority of patients present during childhood.
Presentations in infants and younger children:
- Frequent respiratory infections, wheezing.
- Feeding difficulties, failure to thrive
- CHF with dyspnea, tachypnea, diaphoresis, lethargy, hepatomegaly
- Low cardiac output with pallor, decreased peripheral pulses
Presentations in older children and adults, similar to mitral stenosis:
- Frequent respiratory infections
- Dyspnea, orthopnea, paroxysmal nocturnal dyspnea.
- Hemoptysis
- Hoarseness
Symptomatology associated with right heart failure secondary to pulmonary HTN: Edema, ascites, lethargy.
Symptomatology can be precipitated by requirement for increased flow through the membrane and/or decreased filling time, as in exercise, pregnancy, infection, emotional stress and atrial fibrillation.

Physical Exam

The membrane can cause a diastolic inflow murmur, a continuous murmur, a systolic murmur and sometimes no murmur at all. Murmurs are rarely prominent, and this is often a cause of delayed diagnosis.
Pulmonary rales
Evidence of pulmonary HTN:
- RV heave
- Loud pulmonary component of the 2nd heart sound.
Evidence of right heart failure:
- Increased jugular venous pressure
- Hepatomegaly
- Ascites and edema
Evidence of low cardiac output

Tests

Imaging

EKG:
- Findings indicative of pulmonary HTN:
  - RV hypertrophy
- Tall, peaked P waves for right atrial hypertrophy
- Broad, notched P waves are sometimes seen as a sign of dilation of the posterior chamber.
CXR:
- Evidence of pulmonary venous congestion with interstitial edema and possible Kerley B lines
- Possible indication of pulmonary HTN with an enlarged main pulmonary artery and RV hypertrophy
- Possible "left atrial" enlargement secondary to dilated posterior chamber
Echo:
- Major diagnostic modality for the diagnosis of cor triatriatum
- The membrane is seen as a linear echodensity in the left atrium. The severity of obstruction can be readily studied by Doppler evaluation. Secondary signs of pulmonary HTN, the presence of an atrial septal communication, and/or other anomalies may be diagnosed by 2D and Doppler imaging. Three-dimensional echo has also been used to delineate the anatomy of this malformation.
MRI:
- Can be used to complement the echo in cases where echo images are more limited. It can help delineate associated anomalies and help refine the ventricular functional assessment.
CT:
- Also been used to diagnose the intraatrial membrane of cor triatriatum

Surgery
Cardiac catheterization:

Diagnostic catheterization is no longer routinely performed.
Hemodynamic findings include pulmonary HTN with an increased pulmonary arterial wedge pressure and normal left atrial anterior chamber pressure. A left-to-right shunt can be ruled out by oximetry. The intraatrial membrane can be identified by angiography. Other associated defects can be delineated.

Pathological Findings
The malformation consists of a fibromuscular membrane.

Differential Diagnosis

In children:
- Causes of pulmonary HTN with pulmonary venous congestion:
  - Stenosis of the pulmonary veins
  - Small left-sided structures, including congenital mitral stenosis, with a restrictive atrial septum.
- Other causes of pulmonary HTN:
  - Large left-to-right shunt from a VSD, ASD,
  - PDA
  - Complex congenital heart disease
  - Pulmonary disease
  - Primary pulmonary HTN
In adults:
- Mitral valve stenosis
- Left atrial thrombus
- Left atrial myxoma

Treatment

Medication

Medical treatment is aimed at relieving symptomatology before surgical correction and is only supportive in nature.
In patients with severe obstruction, surgery should not be delayed.

Additional Treatment

General Measures
Supportive measures are necessary in the gravely ill patient. These include oxygen and ventilatory support if needed.

Surgery

Treatment of cor triatriatum is surgical and includes complete resection of the membrane on cardiopulmonary bypass. It is a relatively simple intervention with low operative mortality.
Although balloon dilatation of the membrane has been reported, operative intervention remains the preferred treatment.

In-Patient Considerations

Admission Criteria

Evidence of complications
In the great majority, surgery is undertaken immediately after diagnosis.

Discharge Criteria

Recovery from surgery
Control of complications

Ongoing Care

Follow-Up Recommendations

Patient Monitoring

Rarely, asymptomatic patients with unrestrictive membranes have been followed closely without immediate intervention.
After surgery, monitoring is easily done with serial ECG.

Diet

No restriction on diet once the membrane has been resected

Patient Education

Activity:

No restriction of physical activities once the membrane has been resected

Prognosis

Untreated patients presenting in the 1st yr of life have a mortality rate of up to 75%.
Prognosis after surgical repair depends on patient status at the time of diagnosis and on the presence of associated malformations. Mortality risk is primarily in the perioperative period. For patients in good condition with the classical form, prognosis is excellent and late complications are rare.

Complications

Pulmonary infections
Pulmonary HTN
Hemoptysis
Right heart failure
Atrial arrhythmias
Systemic thromboembolic events
Low cardiac output

Additional Reading

1
Allen HDMoss and Adams' Heart Disease in Infants, Children, and Adolescents: Including the Fetus and Young Adult, 7th ed.Philadelphia: Lippincott Williams & Wilkins, 2008.
2
Alphonso N, Norgaard MA, Newcomb A Cor triatriatum: presentation, diagnosis and long-term surgical results. Ann Thorac Surg. 2005;80(5): 1666-1671.
3
Bonow RO, Carabello BA, Chatterjee K 2008 focused update incorporated into the ACC/AHA 2006 guidelines for the management of patients with valvular heart disease: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Writing Committee to revise the 1998 Guidelines for the Management of Patients with Valvular Heart Disease). Endorsed by the Society of Cardiovascular Anesthesiologists, Society for Cardiovascular Angiography and Interventions, and Society of Thoracic Surgeons. J Am Coll Cardiol. 2008;23;52(13):e1-142.
4
Freedom RMThe Natural and Modified History of Congenital Heart DiseaseElmsford, NY: Blackwell Pub./Futura, 2004.
5
Herlong JR, Jaggers JJ, Ungerleider RM. Congenital Heart Surgery Nomenclature and Database Project: Pulmonary venous anomalies. Ann Thorac Surg. 2000;69(4 Suppl):S56-69.

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