Cor Triatriatum Sinister with Secundum Atrial Septal Defect

Graphical abstract

Highlights

• •Multimodality imaging identifies cor triatriatum sinister and its consequences.
• •Echocardiography is useful in defining a cor triatriatum sinister membrane.
• •Cor triatriatum sinister can have a variable clinical presentation.

Introduction

Cor triatriatum sinister is a relatively rare congenital condition in which the left atrium is bisected by a fibromuscular membrane into two distinct chambers. There are multiple hypotheses for the embryologic origin of this congenital defect. The presentation of patients can be during infancy, childhood, or adulthood, and this is due largely to variation in both the degree of obstruction to pulmonary venous return and the presence of associated lesions. We describe the case of a patient presenting in early adulthood with symptoms associated with cor triatriatum sinister and an atrial septal defect (ASD).

Case Presentation

A 21-year-old, previously very active man was admitted to our institution with peripheral edema, weight gain, and gradual onset of shortness of breath for 3 months. His symptoms had progressed to New York Heart Association functional class III with orthopnea and paroxysmal nocturnal dyspnea. Before admission he had noticed palpitations, substantial weight gain, and a cough. He was initially seen at a regional hospital several weeks prior and noted to be in atrial fibrillation. He was treated with a rate-control approach with metoprolol and anticoagulated with apixaban. He presented several more times to the emergency department over the course of the week with increasing dyspnea. He was ultimately electrically cardioverted and discharged.

Despite this management, the patient quickly noted a recurrence of his symptoms and presented to the emergency department at our institution. He had gained 9 kg from his usual weight. His blood pressure was 135/75 mm Hg and heart rate (HR) regular at 95 beats/min. His oxygen saturation was 96% on room air. His jugular venous pulse was increased about 10 cm above the sternal angle, and he had substantial peripheral (3+) pitting edema. On auscultation, he had bibasal fine inspiratory crackles. On cardiac auscultation, he had a fixed split second heart sound with no significant murmur. Electrocardiography revealed sinus rhythm with right atrial enlargement and right bundle branch block with right ventricular (RV) hypertrophy. Chest radiography showed an enlarged cardiac silhouette with a cardiothoracic ratio of 0.62 and perihilar venous congestion. The patient was admitted and improved rapidly with intravenous furosemide.

Transthoracic Echocardiography

Transthoracic echocardiography (Figure 1 and Video 1) revealed a left atrial membrane, with flow convergence at the membrane on color Doppler (Video 2) and a mean diastolic gradient of 5 mm Hg at a HR of 54 beats/min. A secundum ASD with continuous left-to-right shunting was also noted (Figure 2 and Video 3). Transthoracic echocardiography also revealed pulmonary hypertension with eccentric hypertrophy of the right ventricle, with severe dilation and moderate systolic dysfunction. It was originally unclear whether the left atrial membrane represented a supravalvular mitral membrane (SVMM) associated with Shone complex or a cor triatriatum sinister–type pathology. However, on further review, the mitral valve morphology was noted to be normal with two appropriately positioned papillary muscles, there was no evidence of a parachute mitral valve, and no sub- or supra-aortic stenosis was identified.

Figure 1.

(A) Modified apical four-chamber view in diastole with a membrane (blue arrows) bisecting the left atrial cavity immediately proximal to the open mitral valve (yellow arrows); severe right ventricular dilatation is also noted. (B) Apical three-chamber view with the same membrane (blue arrows) proximal to the mitral valve (yellow arrows). The fenestration in the membrane (red arrow) is seen anteriorly in the left atrium near where it subtends the aortic root. (C) The same apical three-chamber view with color Doppler paced across the membrane and mitral valve. Flow convergence (white arrow) can be seen arising proximal to the mitral valve at the level of the fenestration in the membrane. (D) Spectral Doppler tracing across the left atrial inflow with a mean diastolic gradient of 5 mm Hg at an HR of 54 beats/min. RA, Right atrium; RV, right ventricle.

Figure 2.

(A) Modified apical four-chamber view with color Doppler across the secundum ASD reveals prominent left-to-right interatrial shunting. (B) Two-dimensional zoomed view of the interatrial septum (IAS) from the apical four-chamber view, with the membrane (blue arrow) bisecting the left atrial cavity above the mitral valve (yellow arrow). (C) The same zoomed view, with color Doppler revealing shunting across the IAS to the right atrium (RA) from the pulmonary venous chamber above the membrane (white arrow). LA, Left atrium.

Transesophageal Echocardiography

The patient underwent transesophageal echocardiography to confirm the diagnosis of cor triatriatum sinister (Figure 3A), with the key pathognomonic finding of the left atrial appendage arising from the left atrial chamber (Figure 3B), as opposed to the morphology of an SVMM. The cor triatriatum membrane was located immediately downstream to a secundum ASD. This ASD resulted in communication between the higher pressure pulmonary venous chamber and the right atrium (Figure 3D and Video 4). There was prominent left-to-right shunting. Four pulmonary veins were visualized connecting to the more superior pulmonary venous chamber of the left atrium. Transesophageal echocardiography also confirmed a bicuspid aortic valve with right and left coronary cusp fusion (Figure 3C), with no evidence of aortic coarctation.

Figure 3.

(A) Transesophageal echocardiography demonstrating the membrane in the left atrium (LA) (blue arrows) from the midesophageal view at 0°. The membrane bisects the left atrial cavity into a pulmonary venous chamber and a left atrial chamber (white star) contiguous with the mitral valve (yellow arrow, same in [B]). (B) Midesophageal view at 70° with counterclockwise rotation (from the view in A) to the lateral aspect of the LA. Focusing on the left atrial appendage (LAA) (red arrowhead), the membrane (blue arrow) is again visualized bisecting the left atrial cavity into a pulmonary venous chamber and a left atrial chamber (white star). The presence of the LAA arising from the left atrial chamber differentiates this membrane as a cor triatriatum sinister instead of an SVMM, which would be below the LAA. (C) Midesophageal short-axis view of the aortic valve, showing a congenitally bicuspid aortic valve with right coronary cusp and left coronary cusp fusion. (D) Midesophageal short-axis view of the interatrial septum with color Doppler. A secundum ASD is seen communicating between the right atrium (RA) and the pulmonary venous chamber. The left atrial chamber (white star) is visualized downstream of the cor triatriatum membrane (blue arrow). LV, Left ventricle; RV, right ventricle.

Multiple three-dimensional data sets were acquired at the time of transesophageal echocardiography and confirmed a cor triatriatum sinister membrane with a single fenestration between the pulmonary venous and left atrial chamber, anteromedially in the left atrium near the aortic knuckle (Figure 4A, blue arrow, and Video 5). The secundum ASD was visualized (Figure 4B and Video 6) and was measured using 3DQ (QLAB version 10.4; Philips Medical Imaging, Andover, MA) software and found to be 1.4 × 2.0 cm in dimension with an area of 2.2 cm²; the secundum ASD was measured at its largest extent during diastole (Figure 4C).

Figure 4.

(A) View of the left atrial septum reconstructed from three-dimensional zoomed data acquired during transesophageal echocardiography. The interatrial septum (IAS) is seen en face, oriented with anterior (ant.) and posterior (post.) positions labeled. The cor triatriatum membrane (blue arrow) in the left atrium (LA) is seen dividing the LA into the posteriorly located pulmonary venous chamber and the anteriorly located left atrial chamber contiguous with the mitral valve (MV) (black star). The fenestration in the membrane is seen anterosuperiorly (red arrow). Note the secundum ASD (black arrow, same in [B]) located above the defect in the superoposterior septum of the pulmonary venous chamber. (B) Standard right atrial en face view showing the IAS en face from the right atrium. (C) Measurement of the ASD made with 3DQ reconstruction shows a defect measuring 1.4 × 2.0 cm in diameter. Ao, Aorta; AV, aortic valve; IVC, inferior vena cava; SVC, superior vena cava; TV, tricuspid valve.

Cardiovascular Magnetic Resonance Imaging

Cardiac magnetic resonance imaging (MRI) was performed to confirm the pulmonary vein anatomy and to assess shunt ratio. MRI confirmed a cor triatriatum sinister with a single anteriorly positioned defect (Figure 5, Videos 7 and 8). The pulmonary venous connections returned normally to the superior pulmonary venous chamber (Figure 6). Shunt ratio (Qp/Qs) calculated by phase contrast imaging was 3.6:1. Volumetric assessment of the right ventricle revealed severe dilatation and moderate systolic dysfunction (end-diastolic volume 302 mL/m², RV ejection fraction 37%).

Figure 5.

(A) Steady-state free precession (SSFP) gradient-echo cine MRI view in the vertical long axis showing the cor triatriatum membrane dividing the left atrial cavity into the pulmonary venous chamber and the left atrial chamber (black star) immediately proximal and contiguous with the mitral valve. The left atrial appendage (red arrowhead) again can be seen arising from the left atrial chamber, confirming that the membrane is a cor triatriatum membrane. This correlates with the anatomy described by the transesophageal echocardiographic view seen in Figure 3B. (B) SSFP cine image from the short-axis stack at the base of the heart showing both the left atrial (black star) and pulmonary venous chambers separated by the cor membrane and the communication across the secundum ASD (black arrow) between the right atrium and the pulmonary venous chamber. This image correlates with the transesophageal view seen in Figures 3C and 3D. (C) SSFP cine image in the three-chamber view showing the cor triatriatum membrane (blue arrow) and the mitral valve (yellow arrow). The fenestration across the membrane is seen anteriorly, where it subtends the aortic root, as was noted in the transthoracic echocardiographic apical three-chamber view in Figures 1B and 1C and in the reconstructed three-dimensional en face left atrial view seen in Figure 4A. Ao, Aorta; AV, aortic valve; LA, left atrium.

Figure 6.

(A,B) Bright-blood gradient-echo images from the axial stack showing entrance of the pulmonary veins to the pulmonary venous chamber of the left atrium located posterior and proximal to the cor triatriatum membrane (blue arrow). LIPV, Left inferior pulmonary vein; LSPV, left superior pulmonary vein; RIPV, right inferior pulmonary vein; RSPV, right superior pulmonary vein.

Cardiac Catheterization

Because of suspicion of the surprisingly high shunt fraction, coupled with the mismatch between the symptoms and the relatively moderate gradient across the membrane, the patient underwent left and right cardiac catheterization. This revealed pulmonary hypertension (55/19 mm Hg), with mean pulmonary artery pressure of 32 mm Hg and normal pulmonary vascular resistance (PVR) of 2 Wood units. The secundum ASD was easily traversed, revealing a mean pressure of 17 mm Hg (at an HR of 56 beats/min) in the pulmonary venous chamber of the left atrium, a mean pressure of 13 mm Hg (at an HR of 65 beats/min) in the left atrial chamber of the left atrium, and a mean gradient across the membrane of 4 mm Hg at an HR of 59 beats/min (Figure 7). The mean right atrial pressure was measured at 10 mm Hg. There was a substantial step up in oxygen saturation in the right atrium, with a shunt ratio calculated using Fick's method of 3:1. The large shunt ratio was consistent with that shown on cardiac MRI.

Figure 7.

(A) Pressure tracing obtained during cardiac catheterization from the left atrial chamber (mean, 13 mm Hg). (B) Pressure tracing from the pulmonary venous higher pressure chamber (mean, 17 mm Hg). Both chambers were accessed from across the secundum ASD, with the left atrial chamber accessed via deflection across the membrane fenestration. (C) The difference between the two left atrial chambers is reflected in the mean pressure difference of 4 mm Hg at an HR of 59 beats/min between the pulmonary venous chamber of the left atrium and the left ventricle (assuming a structurally normal, nonstenotic mitral valve between). (D) Tracing from the main pulmonary artery confirming the presence of moderate pulmonary hypertension (mean pulmonary artery pressure, 32 mm Hg). Note that the mean right atrial pressure (not shown) was measured at 10 mm Hg.

Clinical Course

Given the lack of evidence of pulmonary vascular disease (normal PVR despite increased pulmonary pressures), the patient was referred to our congenital heart surgery service. In January 2016, the patient underwent resection of cor triatriatum sinister membrane, patch closure of secundum ASD, and a biatrial maze procedure. The patient had an uncomplicated postoperative course and was discharged home 1 week later. His postprocedural progress has been good, with increasing exercise capacity. His RV systolic function remained mildly impaired on follow-up transthoracic echocardiography 3 months later. RV systolic pressure has normalized.

Discussion

We present the case of a 21-year-old male patient with a recent diagnosis of cor triatriatum sinister (type 3) with obstruction of left ventricular inflow. Cor triatriatum sinister is an interesting and relatively rare congenital cardiac condition present at autopsy in 0.4% of congenital heart patients.¹ In a single pediatric institution's experience, it can be associated with other congenital abnormalities in up to 80% of cases, the most common abnormality being secundum ASD and partial anomalous pulmonary venous return.²

The condition is characterized by a membrane that divides the left atrium into two chambers. In the upper chamber, the upper pulmonary venous chamber connects with the pulmonary veins and receives the pulmonary venous blood. The lower left atrial chamber is contiguous with the atrioventricular valve, and the left atrial appendage arises from it. The relationship with the left atrial appendage is the key anatomic feature differentiating this membrane from an SVMM, which might be seen in Shone syndrome and related pathologies. Our case study was ultimately differentiated using transesophageal echocardiography.

The simplest classification scheme for cor triatriatum sinister was described by Loeffler³ in 1949. Loeffler described type 1 as characterized by no communication in the membrane itself, type 2 as having one or several small perforations in the membrane, and type 3 by one wide opening. Our patient had a type 3 morphology, which is the less hemodynamically significant morphology and is typical of nonpediatric presentations of this pathology.⁴

With our patient, the increased resistance across the cor triatriatum sinister membrane substantially increased the volume of left-to-right shunting across the secundum ASD. Interestingly, the increased volume resulted in pulmonary venous hypertension without an increase in PVR. The increased right-sided pressure was therefore largely flow related and did not reflect the establishment of pulmonary vascular remodeling, as documented by normal PVR.

Of note, the mild pressure gradient across the left atrial membrane fenestration likely did not reflect the high resistance across this circuit, as the nonrestrictive secundum ASD acted as a pop-off valve decompressing the higher pressure pulmonary venous chamber into the lower pressure right atrium. This gradient differential was noted invasively, with the gradient between the pulmonary venous chamber and the right atrium measuring 7 mm Hg compared with that between the pulmonary venous chamber and the left atrium, measuring 4 mm Hg, explaining the large degree of left-to-right shunting noted on both MRI and invasively.

The presentation of patients with cor triatriatum sinister is most common during infancy and childhood. Early-adulthood presentations are not unheard of, however, largely because of variation in both the degree of obstruction to pulmonary venous return and the presence of associated lesions. The reason for late presentation in our patient is difficult to determine, but we conjecture that this young man had excellent functional reserve, allowing him to remain asymptomatic for a long period, coupled with a “pop-off” valve effect through the ASD diminishing the degree of pulmonary venous obstructive symptoms. It is likely, then, that the subacute presentation was precipitated by the development of an atrial arrhythmia with rapid ventricular response.

Given the normal PVR, the pulmonary hypertension was felt to be reversible, and given the clinical and imaging evidence of RV impairment and the substantial shunt, it was felt that there was no contraindication to surgery and that the patient would benefit from surgery. Surgical outcomes are typically favorable at experienced centers, with almost all patients becoming asymptomatic and a 5-year survival rate of >90%.2, 5 Predictors of recovery of RV function are unknown. However, repeated cardiac MRI 1 to 2 years later may provide an assessment of reversibility. We are optimistic of RV recovery given the natural course of RV recovery following surgical repair in other pathologies associated with RV dilatation and impairment, such as ASD repair and lung transplantation.

Conclusion

Cor triatriatum sinister is a relatively rare yet important congenital heart disease. Its detection and differentiation from SVMM require careful echocardiographic assessment. Other concomitant congenital abnormalities along with the clinical consequence of right-sided volume overload from a coexisting ASD can be assessed using cardiac MRI and invasive cardiac catheterization. This additional information is valuable especially when surgical intervention is planned.

Supplementary Data

Video 1

Modified apical four-chamber view in diastole with a membrane bisecting the left atrial cavity immediately proximal to the open mitral valve. Severe RV dilatation is also noted.

Video 2

The same apical three-chamber view with color Doppler paced across the membrane and mitral valve. Flow convergence can be seen arising proximal to the mitral valve at the level of the fenestration in the membrane.

Video 3

The same zoomed view, with color Doppler revealing shunting across the interatrial septum to the right atrium from the pulmonary venous chamber above the membrane.

Video 4

The same view with color Doppler confirming left-to-right flow from the higher pressure pulmonary venous chamber to the right atrium.

Video 5

View of the left atrial septum reconstructed from three-dimensional zoom data acquired during transesophageal echocardiography. The interatrial septum is seen en face. The cor triatriatum membrane in the left atrium is seen dividing the left atrium into the posteriorly located pulmonary venous chamber and the anteriorly located left atrial chamber contiguous with the mitral valve. The fenestration in the membrane is seen anterosuperiorly. Note the secundum ASD located above the defect in the superoposterior septum of the pulmonary venous chamber.

Video 6

Standard right atrial en face view showing the interatrial septum en face from the right atrium.

Video 7

Steady-state free precession gradient-echo cine MRI view in the vertical long axis showing the cor triatriatum membrane dividing the left atrial cavity into the pulmonary venous chamber and the left atrial chamber immediately proximal and contiguous with the mitral valve. The left atrial appendage again can be seen arising from the left atrial chamber, confirming that the membrane is a cor triatriatum membrane. This correlates with the anatomy described by the transesophageal echocardiographic view seen in Figure 3B.

Video 8

Steady-state free precession cine image from the short-axis stack at the base of the heart showing both the left atrial and pulmonary venous chambers separated by the cor membrane and the communication across the secundum ASD between the right atrium and the pulmonary venous chamber. This images correlates with the transesophageal echocardiographic view seen in Figures 3C and 3D.