Ann Thorac Surg 2009;87:1920-1923. doi:10.1016/j.athoracsur.2008.10.051
© 2009 The Society of Thoracic Surgeons
Case Reports
Bronchogenic Cyst of the Interatrial Septum Presenting as Atrioventricular Block
Adrian C. Borges, MDa,*,
Fabian Knebel, MDa,*,*,
Alexander Lembcke, MDb,
Alexander Panda, MD, PhDc,
Takeshi Komoda, MD, PhDd,
Nicola E. Hiemann, MDd,
Rudolf Meyer, MD, PhDd,
Gert Baumann, MDa,
Roland Hetzer, MD, PhDd
a Department of Cardiology and Angiology, Charité – Universitätsmedizin Berlin, Berlin, Germany
b Department of Radiology, Charité – Universitätsmedizin Berlin, Berlin, Germany
c Department of Internal Medicine, Yale University School of Medicine, New Haven, Connecticut
d Department of Cardiothoracic and Vascular Surgery, Deutsches Herzzentrum Berlin, Berlin, Germany
Accepted for publication October 12, 2008.
* Address correspondence to Dr Knebel, Charité - Universitätsmedizin Berlin, Charité Campus Mitte, Medical Clinic for Cardiology and Angiology, Charitéplatz 1, Berlin, 10098, Germany (Email: fabian.knebel{at}charite.de).
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Abstract
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Bronchogenic cysts are congenital lesions that are a remnant from abnormal budding of the embryonic foregut. These cysts are usually single; most cases are either asymptomatic or present with respiratory symptoms. A 43-year-old woman presented with intermittent type II atrioventricular block during cholecystectomy. The cardiac evaluation including transthoracic and transesophageal echocardiography and magnetic resonance imaging revealed a cystic homogeneous mass within the interatrial septum. The patient underwent surgical resection of the mass and closure of the septal defect. Histopathology identified ciliated columnar epithelium, consistent with the diagnosis of a bronchogenic cyst.
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Introduction
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There is a variety of rare lesions that can arise from the right and/or left atrium and the interatrial septum and may involve the conduction system. Bronchogenic cysts are congenital lesions that are remnant from the abnormal budding of the embryonic foregut [1, 2]. Multiple cysts are rare as is an intracardiac location. They may or may not be connected to bronchi or bronchioles. The clinical manifestation may range from respiratory distress or swallowing discomfort at the time of birth to those that are asymptomatic throughout life. Presenting symptoms are cough, esophageal compression, postobstructive pneumonia, dyspnea related to extrinsic compression of airway structures [3], pneumothorax, hemoptysis, and chest pain. Transformation to carcinoma is a very rare complication.
A 43-year-old woman underwent cholecystectomy. The physical examination was unremarkable; there were no signs of inflammation or infection. During the operation, she had intermittent type II atrioventricular block with the need of temporary percutaneous pacing line for one day. Five years ago, physical examination, electrocardiogram, and transthoracic echocardiography were performed because the palpitations were unremarkable.
The noninvasive imaging of the heart included transthoracic (Fig 1) and transesophageal echocardiography, and magnetic resonance imaging revealed a cystic homogeneous mass (4.4 x 3.4 cm) within the interatrial septum with an echo reflectance similar to blood. Lipomatous hypertrophy of the interatrial septum was ruled out by the lucency of the interatrial mass. Doppler color echocardiography could demonstrate the lack of blood flow within the cyst and showed no communication between the atria and the cystic mass. Sonicated intravenous echocardiographic contrast passing the lung perfusion bed (Sonovue; Bracco, Konstanz, Germany) demonstrated the lack of any perfusion of the mass. The cyst wall appeared thin. There was no evidence of pulmonary arterial hypertension.
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Fig 1. Apical transthoracic echocardiography showing a cystic tumor (*) between both the atria on the apical four-chamber view. (LA = left atrium; LV = left ventricle; RA = right atrium; RV = right ventricle.)
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Several differential diagnoses were discussed (Table 1). Cardiac magnetic resonance imaging showed a round contoured interatrial mass (4.5 cm in diameter) with a uniformly low signal on T1-weighted image and a high signal on T2-weighted image without contrast enhancement (Fig 2). Coronary angiography showed no stenosis and a small feeding artery originated from the right coronary artery.
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Fig 2. Cardiovascular magnetic resonance imaging shows a round, interatrial cyst within the interatrial wall (arrow).
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The patient underwent surgical resection (Fig 3) and the defect of the atrial septum after resection of the cyst was closed using an untreated autologous pericardial patch. The patient's postoperative course was uneventful and remained asymptomatic in stable sinus rhythm. Six months after surgery, there was no evidence of recurrence.
The tumor was located as part and parcel of the muscular antero-inferior buttress of the atrial septum. Histopathologic examination (Fig 4) showed cuboidal-columnar epithelium on one side of the cyst wall with periodic acid-Schiff positive granules, collagen matrix with heart muscle cells, blood vessels, round cell infiltrates, and neural tissue. The immunohistology revealed pancytoceratine positive (MNF-positive), muscle-actin positive, synaptophysin-negative, chromogranins-negative, S100-positive, and Ki-67 negative tissue. In conclusion, all criteria of a bronchogenic cyst were fulfilled.
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Fig 4. Photomicrograph of the cyst wall showing the large cyst lining of simple columnar epithelium (arrow). (Hematoxylin and eosin; x50.)
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Comment
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This is a very rare case of a bronchogenic cyst of the interatrial septum and the first reported case with atrioventricular block as the initial manifestation. It is likely that the electrophysiology of the atrium was changed by the cyst. The combination of an intracardiac tumor within the atrioventricular septum and conduction abnormalities is formerly described in patients with mesothelioma of the atrioventricular node [4].
The tumor is located within the muscular antero-inferior buttress of the atrial septum, which derived from muscularization of the vestibular spine (historically referred to as the mesenchyme). In the valvuloseptal morphogenesis, the mesenchymalization of the endocardial cushions is an early event. These endocardial cushions are populated by endocardium-derived mesenchyme through an epithelial-to-mesenchymal transformation [5], as well as by cells derived from nonendocardial sources, including neural crest-derived and epicardial-derived cells. The dorsal mesenchymal protrusion constitutes a prominent component in the atrioventricular mesenchymal complex. The malfunction of this complex might be the underlying mechanism for the development of the described tumor.
Regarding the development of the atrial septum, a bronchogenic cyst is not a mass within the interatrial septum, but a cyst of the interatrial groove [6]. Bronchogenic cysts arise from anomalous budding of the foregut and represent part of the spectrum of bronchopulmonary foregut malformations and contain cells from only two germ layers: mesoderm and endoderm. They can occur at any point of the tracheobronchial tree and can be located in the mediastinum, neck, lung, and rarely in the heart. Cardiac bronchogenic cysts are usually at the pericardium. Bronchogenic cysts are frequently accompanied by vascular malformations involving the pulmonary and systemic circulation [7].
If not connected to a bronchiole, they are filled with mucinous material, but may become infected, leading to suppuration [8]. Biopsy of the cyst is therefore a very dangerous procedure because of the risk of embolization of the mucinous creamy liquid [9]. An increase in size may occur due to infection or bleeding [10] inside the cyst. Most cases are either asymptomatic or present with respiratory symptoms such as dyspnea, cough, esophageal compression, compression of the left atrium or left upper pulmonary vein, or pneumothorax [3, 11].
Bronchogenic cysts are benign, and the appropriate therapy has to be individualized, given the generally mild clinical course. In this case, the therapy of choice was surgical treatment, given the association of the lesion with potentially dangerous rhythm disturbances. Only surgical excision can provide the definitive histologic diagnosis.
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Footnotes
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* These authors contributed equally to this article. 
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References
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Abstract
Introduction
