Introduction

Cor Triatriatum Sinister (CTS) represents a rare congenital cardiac defect characterized by the presence of a fibro-muscular membrane separating completely or partially the left atrium into two cavities [1]. Usually, during adulthood this rare anomaly can be found incidentally, due to the incomplete separation of the LA and the absence of haemodynamic compromise, without the need of surgical treatment. The diagnostic assessment was based on bidimensional (2D) transthoracic echocardiography (TTE) as first line imaging tool. However, in selected cases, additional techniques are needed for a more detailed definition of morpho-functional status of CTS, such as transoesophageal echocardiography (TEE) or cardiac magnetic resonance (CMR). With this case report we sought to emphasize the role of three-dimensional (3D) TTE as an alternative method for a more detailed evaluation of CTS when other advanced imaging techniques are contraindicated or not available.

Case presentation

A 66-years old male patient, without history of cardiovascular disease, was admitted to our cardiologic ward due to acute coronary syndrome. An urgent coronary angiography was executed, which revealed a sub occlusive plaque of the left anterior descending artery (LAD) treated with percutaneous angioplasty and a drug eluting stent (DES). The 2D TTE, performed after the procedure, displayed a mildly hypertrophic left ventricle with akinetic apical septal segment and a mild reduction of left ventricular ejection fraction (LVEF 50%). An accurate assessment of the left atrium (LA) in apical 4 chamber view highlighted the presence of a hyperechoic band crossing transversally the chamber from the interatrial septum towards the lateral wall (Fig. 1a), and the presence of CTS was highly suspected. Other associated congenital structural anomalies were not observed. Using the color-Doppler technique, no relevant pathological flow disturbances were detected (Fig. 1b). The 3D TTE evaluation was performed to obtain a more detailed morphological visualization of the membrane. With the en face vision of the membrane from both atrial and ventricular view, it was recognized a wide breach near the posterior wall of the LA, confirming the diagnosis of CTS and the incomplete nature of the membrane [2] (Fig. 1c). No surgical treatment of CTS was recommended in this case.

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(a) Transthoracic echocardiography (TTE) in apical 4 chamber view showed the presence of a hyperechoic band crossing transversally the chamber from the interatrial septum towards the lateral wall (red arrow), arising the suspicion of Cor Triatriatum Sinister. (b) TTE zoom mode in apical 4 chamber view with color-Doppler technique represents a useful tool to evaluate the presence of flow disturbances caused by the membrane. In this case, the lack of flow accelerations in the LA, may suggest the presence of a fenestrated membrane. (c) Three-dimensional (3D) TTE provides adjunctive morphological information in the diagnostic workflow. The en face vision of the membrane, from both atrial and ventricular views, allowed the identification of a wide breach in the membrane near the posterior wall of the LA, confirming the incomplete nature of the defect. LV: left ventricle; RV: right ventricle; RA: right atrium; LA: left atrium

Citation: Imaging 15, 2; 10.1556/1647.2023.00165

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Discussion

CTS is an uncommon congenital anomaly found in 0.1%–0.4% of patients with congenital heart disease [1]. According to the most accepted theory, it derives from the incorrect incorporation of the common pulmonary vein into the left atrium during foetal heart development [3]. The separation between the two chambers of the LA created by the fibromuscular membrane may vary from an obstructive complete septation to an incomplete septum with a wide communication between the two parts of the LA. The entity of this separation has a pivotal role in the development of clinical manifestations, leading to a wide spectrum of symptoms. [4]. During adulthood, CTS is rare finding and the incidentally discovered during diagnostic imaging workflow. In about one fifth of cases reported in literature, patients were asymptomatic [4]. However, an obstructive physiology of the membrane is not infrequent, with the onset of symptoms of congestive heart failure and pulmonary hypertension. In these cases, patients are younger and often undergone an interventional correction of the defect. Associated cardiac anomalies are not rare, with a higher prevalence of atrial septal defect in case of complete septation [4]. TTE plays a key role in the identification of CTS, as a mainstay diagnostic imaging tool. The 2D evaluation from different views permits a morphological preliminary assessment of the defect, although it is a tomographic imaging technique not allowing a well-oriented examination of the defect and adjacent structures. The color-Doppler technique provides information on the presence of flow disturbances in the LA, suggesting the entity of obstruction. Moreover, TTE is necessary for the differential diagnosis between CTS and other cardiac anomalies such as mitral stenosis, supravalvular mitral ring, pulmonary vein stenosis and atrial septal aneurism [5]. In a non-negligible rate of cases CTS was associated with other cardiac anomalies such as atrial septal defect (ASD) or patent foramen ovale, tetralogy of Fallot, persistent left superior vena cava or partially anomalous pulmonary venous connection [4]. Bidimensional TTE may be helpful in the identification of these associated congenital cardiac structural alterations.

Sometimes, the morphology of this hyperechoic band may be difficult to define on 2D TTE images. In these conditions a multiparametric approach is required, using more advanced imaging techniques such as TEE or CMR [6, 7], above all when a surgical treatment was planned. In our case, the morphology of the membrane was not clear on 2D TTE, requiring additional imaging investigations. However, In the first instance CMR was not considered because it would not add any information capable to modify the therapeutic decision-making, due to the non-obstructive nature of the membrane requiring only a conservative management. The CMR seems safe after DES placement, although there is a lack of strong evidence on the effect of magnetic fields on stents recently implanted [8]. The TEE was the best option, providing a high quality visualization of LA structures and a thorough assessment of associated congenital abnormalities. In addition, it is the best imaging modality which enables the exclusion of a possible cardio-embolic origin in case of myocardial infarction with non-obstructive coronary artery disease, but it requires a dedicated probe with an adequately trained operator, which are not always available. Moreover, the administration of intravenous sedatives is often required to improve the patient's tolerance [9]. TEE is a semi-invasive procedure with low, but non-negligible, rate of complications when performed in intensive care unit (ICU) [10]. When these advanced imaging tools are contraindicated or not available, the 3D TTE may be a precious resource. In presence of good acoustic window, the three-dimensional assessment may provide additional information on CTS. In particular, using the en face vision of the membrane from the atrial and ventricular view a more detailed and intuitive definition of the morphology and size of the membrane may be possible [11]. Moreover, this non-invasive technique is safe and frequently available in the hospital echocardiography laboratories. The main limitations are that image acquisition and elaboration is time consuming, requiring an appropriate training of the operator.

Conclusion

In case of CTS suspicion, in presence of good acoustic window, 3D TTE may provide useful information in the morphological evaluation of this rare congenital defect, particularly when other more advanced imaging techniques are not available or contraindicated.

Informed consent statement

Informed consent to publish these data was obtained from the patient.

Authors’ contributions

All authors contributed to the study conception and design. Material preparation and data acquisition were performed by Daniela Santoro. The first draft of the manuscript was written by Paolo Basile under the supervision of Andrea Igoren Guaricci. All authors commented on previous versions of the manuscript. All authors read and approved the final manuscript.

Funding sources

No financial support was received for this study.

Conflict of interests

Paolo Basile, Daniela Santoro, Andrea Igoren Guaricci declare that they have no conflict of interest.

Ethical statement

The study was conducted in accordance with the Declaration of Helsinki.