What is cor triatriatum?

Cor Triatriatum: Definition, Diagnosis, and Management

Cor triatriatum is a rare congenital cardiac anomaly in which a fibromuscular membrane divides either the left atrium (cor triatriatum sinister) or right atrium (cor triatriatum dexter) into two chambers, potentially causing obstruction to blood flow and leading to symptoms similar to mitral or tricuspid stenosis. 1

Anatomical Features

Cor Triatriatum Sinister (Left Atrial Form)

• A partition divides the left atrium into:
  • Posterior chamber: Receives some or all pulmonary veins
  • Anterior chamber: Communicates with the left atrial appendage and mitral valve 1
• The membrane contains a variable-sized opening that determines symptom severity
• The left atrial appendage is invariably in the same chamber as the mitral valve 1

Cor Triatriatum Dexter (Right Atrial Form)

• Less common variant
• Membrane divides the right atrium into two chambers
• Can cause obstruction to right atrial inflow

Associated Conditions

Cor triatriatum sinister is frequently associated with other congenital cardiac anomalies:

• Atrial septal defect (ASD)
• Ventricular septal defect (VSD)
• Anomalous pulmonary venous connections (partial or total) 1
• Pulmonary vein stenosis (may be present before or after surgical repair) 1

Clinical Presentation

The clinical presentation depends on:

1. Size of the opening in the membrane: Smaller openings cause more severe obstruction
2. Presence of associated anomalies
3. Patient age

Common Presentations:

• Infants/Children: Heart failure, pulmonary hypertension, failure to thrive
• Adults: Often asymptomatic until adulthood due to larger membrane openings 2
  • Symptoms mimicking mitral stenosis
  • Dyspnea
  • Atrial fibrillation (chronic or paroxysmal) 2
  • Systemic embolization (including cardioembolic stroke) 3, 4
  • Heart failure
  • Pulmonary hypertension
  • Syncope
  • Sudden cardiac arrest in severe cases 3

Diagnosis

Imaging Modalities:

1. Echocardiography: Primary diagnostic tool

   • Identifies the membrane dividing the atrium
   • Assesses the size of the opening
   • Evaluates for associated congenital anomalies
   • Measures gradient across the membrane

2. Multidetector CT/Cardiac MRI: May provide additional anatomical details 4

3. Cardiac Catheterization: May be used to:

   • Confirm diagnosis in complex cases
   • Measure pressure gradients across the membrane
   • Evaluate pulmonary vascular resistance

Management

Surgical Intervention

Surgical repair is indicated for adults with cor triatriatum sinister who have:

• Symptoms attributable to the obstruction OR
• A substantial gradient across the membrane (typically ≥8 mm Hg) 1

The surgical approach involves:

• Complete excision of the dividing membrane under cardiopulmonary bypass 5
• Repair of any associated congenital anomalies

Outcomes

• Surgical repair provides excellent early and long-term outcomes with low mortality 5
• Survival rate at 10 years is approximately 83% 5
• Most patients achieve NYHA class I or II functional status post-repair 5
• Poorer outcomes may occur in patients with complex associated congenital anomalies 5

Important Considerations

Pre-operative Evaluation

• Adults presenting with cor triatriatum sinister should be thoroughly evaluated for other congenital abnormalities, particularly ASD, VSD, and anomalous pulmonary venous connections 1

Post-operative Follow-up

• In adults with prior repair who develop recurrent symptoms, evaluation for pulmonary vein stenosis is reasonable 1
• Recurrence of membrane stenosis is not typically expected after repair 1

Special Populations

• Pregnant women with symptomatic cor triatriatum may require intervention
• Balloon dilatation may be considered as a bridge to definitive treatment in special circumstances (heart failure, pregnancy) 3

Pitfalls and Caveats

1. Delayed diagnosis: The condition may remain undetected until adulthood or even death in some cases 3
2. Misdiagnosis: Symptoms can mimic mitral stenosis or other more common conditions
3. Embolic risk: Patients may present with thromboembolic events, including stroke, requiring anticoagulation 4
4. Associated anomalies: Failure to identify and address associated congenital defects can lead to suboptimal outcomes

Cor triatriatum should be considered in the differential diagnosis of patients presenting with symptoms of mitral stenosis, particularly when no rheumatic history or typical mitral valve changes are present.