What is cor triatriatum dexter?

Cor Triatriatum Dexter

Cor triatriatum dexter is a rare congenital cardiac malformation in which a membranous partition divides the right atrium into two separate chambers, resulting from persistence of the embryonic right valve of the sinus venosus that normally regresses during fetal development. 1, 2

Anatomic Features

• The membrane creates a proximal chamber (receiving venous inflow from the superior and inferior vena cavae) and a distal chamber (communicating with the tricuspid valve and right atrial appendage) 2
• The degree of septation varies based on the number and size of fenestrations in the membrane, which determines clinical severity 3
• This represents the right-sided counterpart to cor triatriatum sinister (divided left atrium), though cor triatriatum dexter is considerably rarer 4

Clinical Presentation

Clinical manifestations range from completely asymptomatic incidental findings to severe neonatal cyanosis requiring urgent surgical intervention, depending on the degree of right atrial obstruction and associated cardiac anomalies. 1, 2

Symptomatic Presentations

• Severe hypoxia and cyanosis unresponsive to oxygen therapy, caused by massive right-to-left shunting through an associated atrial septal defect when the membrane creates significant obstruction 1
• Persistent mild cyanosis can occur even with insignificant obstruction and normal pulmonary artery pressures 5
• Symptoms attributable to right atrial inflow obstruction warrant surgical consideration 6

Associated Cardiac Abnormalities

• High incidence of right-sided congenital heart defects, particularly secundum atrial septal defects 2, 5
• Complete atrioventricular block has been reported in association with cor triatriatum dexter 3
• Other right-sided cardiac abnormalities frequently coexist 3

Diagnostic Approach

Two-dimensional transthoracic echocardiography is the primary diagnostic modality recommended by the American College of Cardiology for identifying and characterizing cor triatriatum dexter. 6

Key Diagnostic Techniques

• Standard transthoracic echocardiography can identify the membranous partition and define its anatomy 2
• Contrast echocardiography significantly improves diagnostic performance and is essential for demonstrating right-to-left shunting when clinical cyanosis is present 1, 7
• Transesophageal echocardiography provides superior visualization of membrane anatomy and associated defects 5
• Additional imaging modalities may be needed to fully define membrane anatomy and quantify the degree of obstruction 6

Diagnostic Pitfalls

• The condition can be initially misdiagnosed as postnatal maladjustment with pulmonary hypertension when severe cyanosis is present 1
• Failure to respond to oxygen and pulmonary vasodilators should prompt reconsideration of structural causes like cor triatriatum dexter 1

Treatment Indications

Surgical membrane excision is indicated when symptoms are attributable to right atrial obstruction or when there is a gradient ≥8 mm Hg across the membrane. 6

Surgical Criteria (per American College of Cardiology)

• Symptomatic patients with evidence of right atrial obstruction require surgical intervention 6
• Gradient threshold of ≥8 mm Hg indicates hemodynamically significant obstruction 6
• Asymptomatic patients without significant obstruction can be managed conservatively with surveillance 6

Clinical Context

• The American Heart Association and American College of Cardiology do not establish specific treatment criteria for cor triatriatum dexter, reflecting its rarity and generally more benign clinical course compared to cor triatriatum sinister 6
• Urgent surgical correction is required for neonates with severe hypoxia and massive right-to-left shunting 1