Cor Triatriatum

Cor Triatriatum is a rare congenital heart disease characterized by the presence of an abnormal membrane that divides the left atrium (Cor Triatriatum Sinistrum) or, less commonly, the right atrium (Cor Triatriatum Dextrum) into two separate chambers. This condition may cause varying degrees of blood flow obstruction, leading to hemodynamic consequences similar to mitral stenosis in severe cases.

Etiology and Pathogenesis

The exact etiology of Cor Triatriatum remains unclear, but it is hypothesized to result from an abnormal development of the left atrium during embryogenesis. Normally, the primitive septum is completely resorbed, allowing the formation of a single atrial chamber. In patients with Cor Triatriatum, a residual membrane persists, dividing the atrial cavity.
This defect can occur in isolation or be associated with other congenital heart diseases, such as atrial septal defect (ASD), transposition of the great arteries (TGA), or aortic coarctation.

Pathophysiological Mechanisms

The abnormal membrane obstructs blood flow from the left atrium to the lower chambers, increasing left atrial pressure and potentially leading to pulmonary hypertension. Depending on the size of the orifice in the membrane, symptoms can range from mild to severe, with signs of pulmonary congestion and heart failure.

Risk Factors and Prevention

No specific risk factors for Cor Triatriatum have been identified, as it is a congenital developmental defect. However, familial cases suggest a possible genetic predisposition. No preventive measures are available, although prenatal diagnosis can improve neonatal management.

Clinical Presentation

Symptoms vary depending on the severity of blood flow obstruction.
In neonates and infants with severe forms, the following may occur:

• Dyspnea at rest or with exertion
• Poor growth
• Cyanosis in severe cases
• Recurrent respiratory infections

In adults or mild cases, the condition may remain asymptomatic or present with symptoms similar to mitral stenosis, such as fatigue, palpitations, and atrial fibrillation episodes.

Diagnosis and Investigations

Cor Triatriatum diagnosis relies on:

• Transthoracic and transesophageal echocardiography: first-line imaging techniques to visualize the abnormal membrane and assess its effect on blood flow.
• Cardiac MRI or CT scan: useful in doubtful cases for more detailed anatomical definition.
• Cardiac catheterization: performed in selected cases to evaluate intracardiac pressures.

Treatment and Prognosis

Treatment depends on the severity of the condition. In mild cases, clinical follow-up may suffice without the need for intervention. In symptomatic patients or those with pulmonary hypertension, surgical correction through excision of the abnormal membrane is indicated.
Prognosis is excellent after surgical treatment, with normalization of hemodynamics and symptom resolution in most patients.

Complications

If left untreated, Cor Triatriatum may lead to:

• Pulmonary hypertension
• Congestive heart failure
• Arrhythmias, including atrial fibrillation
• Increased susceptibility to respiratory infections

References
1. Freedom RM, et al. Congenital Heart Disease: Textbook of Cardiovascular Medicine. Lippincott Williams & Wilkins, 2020; 425-430.
2. Moore P, et al. Cor Triatriatum: Diagnosis and Management. Circulation. 2018; 137(12): 1185-1193.
3. Stout KK, et al. Congenital Heart Disease in Adults. J Am Coll Cardiol. 2021; 77(18): 2348-2360.
4. Levin M, et al. Imaging in Congenital Heart Disease. Radiology. 2020; 295(2): 327-342.
5. Hoffman JI, et al. The Incidence of Congenital Heart Disease. J Am Coll Cardiol. 2019; 74(23): 2993-3001.
6. Grosse-Wortmann L, et al. Cardiac MRI in Congenital Heart Disease. Heart. 2022; 108(5): 381-392.
7. Selamet Tierney ES, et al. Pediatric Cardiology. Elsevier, 2019; 201-213.
8. Moss AJ, et al. Congenital Cardiac Defects and Their Management. NEJM. 2019; 380(18): 1761-1772.
9. Anderson RH, et al. Surgical Approaches to Congenital Heart Disease. J Thorac Cardiovasc Surg. 2020; 159(6): 2289-2301.
10. Kim YY, et al. Advances in Fetal Echocardiography. Pediatr Cardiol. 2021; 42(3): 499-512.