Focusing on Cor Triatriatum Dexter and Atrial Septal Defects

To the Editor:

We read with interest the article in the Texas Heart Institute Journal by Vukovic and colleagues,¹ and we have a few comments that we think are of note.

Cor triatriatum dexter (CTD) and prominent eustachian valve are thought to result from the incomplete and abnormal regression of the embryonic right valve of the sinus venosus, caused by abnormal fetal circulation. Whereas the left leaflet of the sinus venosus is incorporated into the interatrial septum and forms part of the septum secundum, the right leaflet is reabsorbed, forming the eustachian and thebesian valves.

A prominent Chiari network and eustachian or thebesian valve might simulate CTD and produce insignificant flow accelerations. However, in CTD (as in the case report¹), the valve is attached to the atrial septum. In the case of a prominent or giant eustachian valve, there are no attachments, irrespective of obstruction.² In addition, CTD is frequently associated with right-sided abnormalities such as atrial septal defect (ASD). For this reason, although successful percutaneous ASD closure has been reported in patients who have prominent eustachian valves,³ extra care should be exercised in patients with CTD: septal attachments on the atrial septum might lead to entanglement, misplacement, or leftward bowing because of a high right atrial pressure and embolization of the device. In addition, proper deployment and device stability might be prevented by inadequate definition of the ASD margins, overlap of the valve remnant, and under- or oversizing of the device.⁴

As stated by the authors,¹ the patient's symptoms depend primarily on the degree of right atrial septation and the size of the sinoatrial orifice. However, a large, prominent eustachian valve can sometimes obstruct the inferior vena cava and lead to trapped catheters, supraventricular arrhythmias, bacterial endocarditis, and thrombosis with subsequent pulmonary or systemic embolism. For this reason, if the patient will be undergoing heart surgery for other reasons, the membrane or fibrous band should be removed, even if it is not obstructive.

Finally, left-to-right shunting secondary to restrictive CTD and a patent foramen ovale or ASD might lead to central cyanosis and symptoms consistent with increased portal venous pressure, such as ascites, coagulopathy, hepatic dysfunction, and protein-losing enteropathy.⁵ In such cases, ASD closure should be undertaken after surgical or percutaneous balloon correction of CTD.⁶