Band-Like Remnant of the Embryonic Right Valve of the Sinus Venosus as an Incidental Finding in an Elderly Woman.

A short-statured 79-year-old woman with dyspnea on exertion (functional Class II according to the New York Heart Association calcification) referred to our echocardiography laboratory for further evaluation. She had a history of diabetes mellitus and hypertension, and her heart rhythm was atrial fibrillation. All these conditions were treated medically. A two-dimensional transthoracic echocardiographic examination demonstrated a ridge-like band originating from the crista terminalis and running parallel to the interatrial septum. The band crossed through the right atrial cavity and attached to the lateral wall of the right atrium. [Figure 1] The band was immobile, without fenestration. Color Doppler study showed that the band did not produce any obstruction. These findings were in favor of the remnant of the embryonic right valve of the sinus venosus, such that this embryonic valve in its complete shape could result in cor triatriatum dexter. A three-dimensional transthoracic echocardiographic examination confirmed these findings. [Video 1] The other echocardiographic findings were severe left ventricular enlargement with mild systolic dysfunction (ejection fraction ≈50%), mild right ventricular enlargement with mild systolic dysfunction, severe left and right atrial enlargement, moderate-to-severe aortic regurgitation, mild-to-moderate mitral regurgitation, and moderate-to-severe tricuspid regurgitation (tricuspid regurgitation gradient = 25 mm Hg and estimated systolic pulmonary artery pressure = 35 mm Hg). The interatrial septum was intact in color Doppler study.

Figure 1

(a) Modified 5-chamber view in two-dimensional echocardiography shows the presence of a band in the right atrium originating from the crista terminalis and dividing the right atrium. (b) Short-axis view at the level of aortic valve reveals the a ridge (c) In the subcostal bicaval view, the band runs parallel to the interatrial septum and the orifice of the inferior and superior venae cavae and opens to the posterior chamber. (d) In live three-dimensional transthoracic echocardiography, the presence of this band is illustrated. AO = Aorta, LA = Left atrium, LV = Left ventricle, RA = Right atrium

Cor triatriatum dexter is a very rare congenital anomaly caused by a dividing membrane in the right atrium. The membrane is a remnant of the embryonic right valve of the sinus venosus.[1] The presenting symptoms are associated with other structural defects and the presence or absence of obstruction.[2] In addition, supraventricular arrhythmias such as atrial fibrillation in this condition have been reported.[3] The most common condition in the differential diagnosis of cor triatriatum dexter is an elongated Eustachian valve. This right atrial structure originates from the anterior part of the orifice of the inferior vena cava and courses toward the interatrial septum; nonetheless, the membrane in cor triatriatum dexter originates from the crista terminalis.[124] In our case, there was a band-like (not membrane) remnant of the embryonic right valve of the sinus venosus, which may have been due to the incomplete resolution of the aforementioned valve, so that only 1 band of this membrane had remained. Although this anomaly is very rare in the daily practice, the presence of this anomaly should always be kept in mind.

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