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Cor Triatriatum

Cor triatriatum is a rare congenital heart malformation where the left atrium (cor triatriatum sinistrum) or right atrium (cor triatriatum dextrum) is divided by a fibromuscular membrane into two chambers, obstructing blood flow and potentially causing pulmonary venous congestion, heart failure, or arrhythmias.

Anatomical Classification

• Cor triatriatum sinistrum (left-sided) is the most common form, accounting for approximately 0.1-0.4% of all congenital heart defects, where a fibromuscular membrane divides the left atrium into a superior chamber receiving pulmonary veins and an inferior chamber containing the mitral valve and left atrial appendage
• Cor triatriatum dextrum (right-sided) is extremely rare, involving a membrane dividing the right atrium, typically separating the superior vena cava from the remainder of the right atrium

Clinical Presentation

• Symptomatic patients present with signs of pulmonary venous obstruction including dyspnea, orthopnea, pulmonary edema, hemoptysis, and right heart failure, with severity depending on the size of the opening in the obstructing membrane
• Asymptomatic patients with large membrane openings may remain undiagnosed until adulthood or be discovered incidentally on echocardiography
• Pediatric presentation often mimics mitral stenosis with failure to thrive, recurrent respiratory infections, and pulmonary hypertension in severe cases

Diagnostic Approach

• Transthoracic echocardiography is the primary diagnostic modality, demonstrating the membrane dividing the atrium with color Doppler showing turbulent flow through the membrane opening
• Transesophageal echocardiography provides superior visualization of the membrane anatomy, fenestrations, and associated cardiac anomalies
• Cardiac MRI or CT offers detailed anatomical assessment when echocardiography is inconclusive, particularly for surgical planning

Associated Cardiac Anomalies

• Atrial septal defects occur in 50-80% of cases, typically located in the membrane itself or in the interatrial septum
• Partial anomalous pulmonary venous return, persistent left superior vena cava, and other congenital heart defects frequently coexist
• Mitral valve abnormalities may be present and must be evaluated preoperatively

Treatment Strategy

• Surgical resection of the obstructing membrane is the definitive treatment for symptomatic patients or those with significant obstruction (mean gradient >5 mmHg across the membrane)
• Timing of surgery should be performed promptly in symptomatic infants and children to prevent irreversible pulmonary vascular disease
• Asymptomatic adults with minimal obstruction may be managed conservatively with serial echocardiographic surveillance every 1-2 years
• Surgical outcomes are excellent with complete membrane resection, with mortality rates <2% in experienced centers and resolution of symptoms in the vast majority of patients

Postoperative Considerations

• Residual obstruction is rare after complete membrane excision but requires surveillance echocardiography at 3-6 months postoperatively
• Atrial arrhythmias may persist or develop postoperatively, particularly in adults with long-standing disease
• Long-term prognosis is excellent after successful surgical repair with normal life expectancy and functional capacity