In the pediatric population, this anomaly may be associated with major congenital cardiac lesions such as tetralogy of Fallot, double outlet right ventricle, coarctation of the aorta, partial anomalous pulmonary venous connection, persistent left superior vena cava with unroofed coronary sinus, ventricular septal defect, atrioventricular septal (endocardial cushion) defect, and common atrioventricular canal.
Cor triatriatum dextrum is extremely rare and results from the complete persistence of the right sinus valve of the embryonic heart.
If the communicating orifice is small, the patient is critically ill and may succumb at a young age (usually during infancy) to congestive heart failure and pulmonary edema.
As the malformed membrane calcifies with age, thus further narrowing such opening, decreased cardiac output produces features of pulmonary venous hypertension and right heart failure—including symptoms of dyspnea and orthopnea, easy fatigability, palpitations and shortness of breath, among others.
The surgery, which usually occurs by first excising the diaphragm and then closing the atrial septum, has a reported survival of 90% at five years, with almost all patients becoming asymptomatic post-surgery.