[Cor triatriatum dextrum resulting from the persistence of embryonic remnants of the right valve of the sinus venosus: prevalence and echocardiographic aspects in a large consecutive non-selected patient population]. / Pseudocuore triatriato destro da persistenza di residui embrionari della primitiva valvola del seno venoso: prevalenza ed aspetti ecocardiografici in un'ampia popolazione consecutiva non selezionata.

ABSTRACT

BACKGROUND: Cor triatriatum destrum is a rare congenital malformation, usually associated with complex right heart abnormalities, characterized by a membrane that divides the right atrium into two chambers. It is considered the result of the incomplete and abnormal regression of the embryonic right valve of the sinus venosus. When the valve regresses the cephalic portion forms the crista terminalis and the caudal portion develops into the Eustachian and Thebesian valve. With an incomplete regression, a fenestrated or an unfenestrated membrane may persist in the right atrium. We describe the clinical and echocardiographic characteristics of this type of remnants in the right atrium. METHODS: In a 4-month period, 1728 transthoracic two-dimensional and Doppler echocardiographic studies were consecutively performed. RESULTS: Twenty-seven patients (16 males, 11 females, mean age 55 +/- 21 years, range 1-87 years) were occasionally recognized to be affected by a membrane inside the right atrial cavity. On the basis of its echocardiographic appearance (a membranous structure connecting the orifice of the inferior vena cava to the atrial septum with evident fenestration in 74% of cases), absence of associated congenital abnormalities (92.5% of cases), interatrial shunt or abnormal flow pattern of venous systemic return, a diagnosis of a normal benign anatomic variant of sinus venous remnants (similar to the so-called "Chiari's network") could be made in every case. CONCLUSIONS: The incomplete regression of the embryonic right valve of the sinus venosus may leave a fenestrated or an unfenestrated membrane in the right atrium that should be considered a normal benign variant of the so-called "Chiari's network".