A transthoracic echocardiogram disclosed a linear structure in the left atrium of an adult presenting with atypical chest pain. Biplane transesophageal echocardiography revealed a cor triatriatum. The longitudinal plane was most useful for the assessment of the membrane orifice and the Doppler flow pattern.
Cor triatriatum is a rare cardiac malformation (0.1 percent of all congenital heart diseases). In the majority of the reported cases, this diagnosis was made in infants with signs of pulmonary venous obstruction. It may be associated with other cardiac malformations (atrial septal defect or anomaly of pulmonary venous drainage). Even in symptomatic patients, the presence of the left atrial membrane may be overlooked by transthoracic echocardiography and pulmonary angiography.
Transesophageal echocardiography allows a better approach to the diagnosis.[2-5] However, monoplane probes have limitations as they restrict the exploration to the transverse plane. The following case report illustrates the value of the longitudinal view in the correct evaulation of a cor triatriatum.
A 45-year-old man presented with atypical chest pain. He had normal results of physical examination, chest radiograph, electrocardiogram, and exercise stress testing. Transthoracic echocardiography revealed a very inconspicuous thin linear structure attached to the anterior wall of the left atrium (Fig 1, top). The pulsed-wave Doppler mitral flow was characterized by a middiastolic notch and an increased atrial contraction wave.
A transesophageal echochardiographic examination was performed using an ultrasound unit (Aloka SSD 870) and a 5-Mhz biplane probe. In the transverse plane, a membrane across the left atrium was visualized, separating a posterior chamber receiving the four pulmonary veins from an anterior chamber in connection with the left atrial appendage and with a normal mitral valve. No fenestration of the membrane was seen in this plane (Fig 1, center), and the color-coded Doppler did not reveal any abnormal jet in this plane. In the longitudinal plane, however, an orifice of 1.8 cm in diameter was identified in an eccentric position, near the posteroinferior wall (Fig 1, bottom). The pulsed-wave Doppler at the level of this orifice revealed a low systolic wave and a tall end-diastolic wave, with a maximal velocity of 1.2 m/s. There was no mosiac pattern of turbulent flow across the membrane by color Doppler. The mitral flow exhibited a low rapid filling wave, and a tall, notched atrial contraction wave.
Given the perfect clinical tolerance and the absence of gradient through the membrane, no treatment was advised.
A thorough anatomic assessment is mandatory in cor triatriatum. The opening of the diaphragm may have many configurations. It may be multiple or absent. Associated anomalies must be ruled out. The differential diagnosis has to be made with a supramitral membrane (a shelf-like membrane just above the annulus), a dilated coronary venous sinus (in cases of a persistent left superior vena cava), exuberant atrial septum aneurysms, or nonpathologic remnants of the common pulmonary vein. Transesophageal echography with color Doppler appears well suited to achieve these goals.
The patient had no venous congestion, as expected from the diameter of the visible orifice. However, the presence of this large orifice escaped the transverse plane, probably because of its inferior location, where the access is more difficult (the probe may lose contact with the esophageal wall at this level). This is not the case in the longitudinal plane, where the orifice was readily identifiable. The flow pattern through the orifice was similar to other cases with more severe obstruction. Most of the flow occurs during the ventricular diastole, because less blood is aspirated from the pulmonary veins by the abnormal left atrium during its relaxation. The left ventricular inflow pattern is also consistent with this phenomenon. It usually shows an additional middiastolic wave or, in case of slight tachycardia, as in our patient, an increased end-diastolic wave resulting from a delayed rapid filling wave superimposed on the atrial contraction wave.
This observation illustrates the concept of a continuum between incomplete incorporation of the main pulmonary vein and the syndrome of cor triatriatum. It demonstrates the impact of the longitudinal plane in a situation where the transthoracic and the transesophageal transverse plane approaches were unsatisfactory, even with the aid of the color-coded Doppler. Interestingly, the final result on the clinical decision in this patient was not significantly altered. In the absence of any clinical abnormalities, while the biplane transesophageal echocardiogram adds improved diagnostic capability, its additional clinical value is sometimes controversial. Given the rarity of cor triatriatum, this observation is limited to a single case report. However, it emphasizes the role of biplane transesophageal echocardiography as the appropriate diagnostic technique in patients suspected of having this particular congenital heart disease.
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