Cor Triatriatum

Hemodynamic Effects

1. If non-obstructive (most common):

   • Often an incidental finding.

   • No significant pressure gradient across the membrane.

   • Patients are usually asymptomatic.

2. If obstructive (rare):

   • Impaired blood flow to the tricuspid valve and right ventricle.

   • Elevated right atrial pressure proximal to the membrane.

   • Systemic venous congestion (hepatomegaly, peripheral edema, ascites).

   • May mimic effect of tricuspid stenosis/atresia or Ebstein anomaly.

Asymptomatic in most cases. In symptomatic cases (usually infants or neonates), may present with: Cyanosis (if right-to-left shunting via a PFO or ASD); Right-sided heart failure signs; Decreased RV preload and output.

Summary of Cor-Triatriatum

Cor Triatriatum is a rare congenital heart defect, accounting for only 0.1% to 0.4% of all congenital abnormalities. It is characterized by the presence of a thin, fibromuscular membrane that abnormally divides one of the atria into two chambers. This results in a "three-chambered heart" appearance. The most common form is Cor Triatriatum Sinister (CTS), involving the left atrium. In CTS, a membrane divides the left atrium into a proximal chamber receiving blood from the pulmonary veins and a distal chamber communicating with the left ventricle through the mitral valve. The left atrial appendage is typically part of the distal compartment. Cor Triatriatum Dextrum, involving the right atrium, is much rarer. The embryological basis for CTS is thought to be the incomplete absorption of the common pulmonary vein during fetal development, which should normally fuse with the left atrium. This can lead to concurrent anomalies of the atrial septum and pulmonary venous connection. Cor Triatriatum may occur as an isolated lesion, but it is frequently associated with other congenital cardiac defects. These commonly include atrial septal defects (ASD), ventricular septal defects (VSD), and partial anomalous pulmonary venous connection (PAPVC). One study found pulmonary vein abnormalities in over half of their CTS patients. Other associated anomalies mentioned in the sources include pulmonary valve stenosis or atresia, tricuspid valve abnormalities, anomalous pulmonary venous return, and mitral valve stenosis or regurgitation.

The clinical presentation of Cor Triatriatum is variable and depends on the degree of obstruction caused by the membrane. Patients may range from asymptomatic (often with a large opening in the membrane) to severely symptomatic. Symptoms in infants with CTS are typically due to pulmonary hypertension and pulmonary venous obstruction, and can include cough, dyspnea, wheezing, pulmonary congestion, tachycardia, poor growth and weight gain, feeding difficulties, and respiratory distress. Severe cases can mimic mitral stenosis or pulmonary vein stenosis and may necessitate urgent neonatal repair for pulmonary congestion and low cardiac output. Physical examination findings may include an accentuated pulmonary component of S2, a soft midsystolic murmur at the upper left sternal border, right ventricular heave, basilar rales, diminished peripheral pulses, hepatomegaly, ascites, peripheral edema, distended peripheral veins, jugular venous distension, and pallor.

Echocardiography is generally the diagnostic modality of choice for Cor Triatriatum. It allows for direct visualization of the dividing membrane and flow patterns using color Doppler, which can demonstrate turbulent flow across the membrane. Echocardiography can also identify the location of the atrial appendage (part of the distal chamber in CTS), helping to distinguish it from supravalvular mitral stenosis. Associated defects like ASDs, VSDs, valve abnormalities, and pulmonary venous drainage patterns can also be assessed. Antenatal diagnosis is possible, though rare. Other diagnostic tools include Chest X-ray, which may show pulmonary congestion without significant left atrial enlargement (helpful in differentiating from mitral stenosis), ECG (may show atrial arrhythmias), and cross-sectional imaging like CT or MRI for detailed anatomy, particularly of pulmonary veins. Cardiac catheterization is rarely used for diagnosis currently.

Early surgical repair is the definitive treatment for Cor Triatriatum, especially in symptomatic or obstructive cases. Surgery typically involves a median sternotomy and cardiopulmonary bypass. The primary goal is complete resection of the obstructing membrane, taking care to protect surrounding structures like the mitral valve and conduction system. Associated ASDs are usually closed with a patch. In neonates, keeping a small foramen ovale open post-repair might be considered if there's concern for postoperative pulmonary hypertension. Medical management may be used for preoperative stabilization of heart failure symptoms and managing complications like atrial fibrillation and thromboembolism.

Outcomes after surgical repair are generally excellent, particularly when performed early and for isolated defects. Operative mortality is low (<5%), especially in patients who were not critically ill or who had less complex associated anomalies. Long-term outcomes are also reported as excellent, with most patients being asymptomatic and achieving near-normal cardiac dimensions. However, outcomes in complex cases are dependent on the associated defects. If left unrepaired, particularly with significant obstruction, a large Cor Triatriatum can lead to progressive pulmonary hypertension, heart failure, reduced cardiac output, arrhythmias, thromboembolism, and has a poor prognosis. The diagnosis and management of Cor Triatriatum require an interprofessional team approach, often involving pediatric cardiologists, cardiac surgeons, intensivists, and nurses.

Several more detailed classifications exist, particularly for Cor Triatriatum Sinister, based on the anatomy of the dividing membrane and its communication with the distal left atrial chamber:

• Loeffler Classification: Provided the first classification of Cor Triatriatum. It is based on the amount of communication provided by the occluding diaphragm. There are three main groups:

  • Group 1: Non-communicating diaphragm.

  • Group 2: Septating membrane has one or more small openings.

  • Group 3: Diaphragm has a large opening within it.

• Niwayama Classification: Similar to Loeffler's, focusing on the opening in the dividing septum, classifying lesions based on whether there is no opening, a small opening, or a wide opening.

• Grondin Classification: Classified only those lesions with an opening in the dividing septum as Cor Triatriatum. Lesions without communication between the pulmonary venous chamber and either atrium were considered cases of anomalous pulmonary venous connection.

• Lucas Classification: Combines elements of previous systems. This classification categorizes based on whether the accessory atrial chamber receives all or part of the pulmonary veins and its communication with the left atrium, including other anomalous connections:

  • A. Accessory atrial chamber receives all pulmonary veins and communicates with the left atrium:

    1. No other connections (classic cor triatriatum).

    2. Other anomalous connections (e.g., to the right atrium directly or with totally anomalous pulmonary venous connection).

  • B. Accessory atrial chamber receives all pulmonary veins and does not communicate with the left atrium:

    1. Anomalous connection to the right atrium directly.

    2. With totally anomalous pulmonary venous connection.

  • C. Subtotal cor triatriatum:

    1. Accessory atrial chamber receives part of the pulmonary veins and connects to the left atrium (remaining pulmonary veins connect normally or anomalously).

    2. Accessory atrial chamber receives part of the pulmonary veins and connects to the right atrium (remaining pulmonary veins connect normally).

Variations include those with communication with an atrial septal defect (ASD), communication with a decompressing levocardinal vein, no direct communication but with an ASD (similar to cardiac-type TAPVC), no direct communication (similar to infracardiac TAPVC), and subtotal cor triatriatum (association with partial anomalous pulmonary venous connection - PAPVC). Other classification systems include the Lam classification and the newly proposed Mashadi-Narasimhan-Said classification.

References:

1. Abdulla, R., Al-kubaisi, M., Alsaleh, L., & Awad, S. (2016). Pediatric Electrocardiography. (Publisher information not available in provided excerpt).

2. Ather, B., Meredith, A., & Siddiqui, W. J. (2024). Cor Triatriatum. In: StatPearls [Internet]. StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK534243/.

3. Dipchand, A. I., et al. (eds.). (2024). Manual of Cardiac Care in Children. Springer Nature Switzerland AG. https://doi.org/10.1007/978-3-031-70973-9.

4. Hammoud, R., et al. (2024). Cor Triatriatum: an uncommon congenital anomaly - the experience of a tertiary care center in a developing country. Frontiers in Cardiovascular Medicine. https://www.frontiersin.org/journals/cardiovascular-medicine/articles/10.3389/fcvm.2024.1386660/full.

5. Park, I. S., & Kim, S.-J. (2019). [Book title likely related to Echocardiography in Congenital Heart Disease]. Springer Nature Singapore Pte Ltd. (Full title and specific URL for this publication not available in provided excerpts).

6. Rudolph, A. M. (2009). Congenital Diseases of the Heart: Clinical-Physiological Considerations (Third Edition). A John Wiley & Sons, Ltd., Publication. ISBN: 978-1-405-16245-6. https://onlinelibrary.wiley.com/doi/. (Note: The provided URL is for the publisher's online library requiring access, not a direct link to the PDF).

7. A Tale of Three Chambers: Cor Triatriatum Sinistrum. (2024). CASE (Phila). Elsevier Inc. on behalf of the American Society of Echocardiography. (Authors, volume, issue, pages, and specific article DOI/URL for this publication not available in provided excerpt).

8. Walsh MJ, Ungerleider RM, Aiello VD, Spicer D, Giroud JM. Anomalous pulmonary venous connections and related anomalies: nomenclature, embryology, anatomy, and morphology. World J Pediatr Congenit Heart Surg. 2013 Jan;4(1):30-43. doi: 10.1177/2150135112458439. PMID: 23799752.

Presentation by Dr Nina Nouraeyan (Neonatologist) and Ms Laila Wazneh (NNP) - June 2025

Case 1 - Cor Triatriatum sinister

Parasternal view demonstrating an underfilled left ventricle, which appears partially compressed ("pancaked") due to the pressure-overloaded right ventricle and the overall reduced left ventricular preload.

Case 2 - Cor Triatriatum dexter

Non-obstructive cor tiatriatum dexter with a bidirectional PFO. The right ventricle is small and non-apex forming. The patent ductus arteriosus is small and tortuous, left to right.