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Interact CardioVasc Thorac Surg 2007;6:654-657. doi:10.1510/icvts.2007.157776 © 2007 European Association of Cardio-Thoracic Surgery
Resection of a lipomatous hypertrophic interatrial septum involving the right ventricle
a Department of Cardiothoracic Surgery, Catharina Hospital, Michelangelolaan 2, 5623 EJ Eindhoven, The Netherlands Received 12 April 2007; received in revised form 2 July 2007; accepted 3 July 2007
*Corresponding author. Alard du Hamelstraat 46, 5622 CD, Eindhoven, The Netherlands. Tel.: +31-618138251; fax: +31-402440268.
Lipomatous hypertrophy of the interatrial septum is a rare cardiac lesion that is usually limited to the interatrial septum. We report a case of an extensive lipomatous hypertrophy, which protruded into the right and the left atrium as well as the superior and the inferior vena cava and the right ventricle. A 71-year-old woman was referred to us because of a cardiac mass on a transthoracic echocardiogram, performed on a routine check-up because of a known membranous ventricular septum defect. She underwent surgical resection of the mass and closure of the ventricular septum defect. The postoperative period was complicated by superior vena cava syndrome for which she underwent re-operation. The post mortem histopathological diagnosis was a lipomatous hypertrophic interatrial septum.
Key Words: Tumour; Interatrial septum; Echocardiography; Complication
Lipomatous hypertrophy of the interatrial septum (LHIS) is a rare nonencapsulated hypertrophy of fat within the atrial septum, first described by Prior [1] in 1964 in five patients at post-mortem examination. It is defined as a fatty infiltration of more than 2 cm thick in the atrial septum [2]. In histologic studies affected patients typically show hyperplasia of mature multivacuolated fat cells. Foetal fat, hypertrophied myocytes, myocardial fibres, and fibrosis in various quantities may be found [3]. Although many theories have been suggested, etiology of LHIS is still unknown. In several clinical studies no typical symptoms of LHIS are described although the disease has been associated with supraventricular arrhythmias or sudden death [4, 5].
2.1. History A 71-year-old woman was referred to our department in December 2005 with suspicion of a myxoma in the right atrium. The referring cardiologist detected a large intracardiac tumour with transthoracic echocardiography on a routine examination of his patient. The cardiac case history of this woman dated back to 1993. It was then diagnosed that the patient suffered from an asymptomatic membranous ventricle septum defect and a well tolerated mitral regurgitation grade I. In 1999, she was referred to the hospital with decompensatio cordis, which could be treated with medication. In 2004 it was noted that she had a transient supraventricular tachycardia. The patient suffered from dyspnoea, NYHA Class II, without any other symptoms. She did not have any clinical features of cardiac failure. Physical examination revealed a normal radial pulse. With auscultation of the heart a holosystolic murmur, grade 4/6 with a puntum maximum in the full length of the left sternal notch was noted. The result of the calculated body mass index was 16.53 with a length of 165 cm and weight of 45 kg. On the electrocardiogram, normal sinus rhythm with a frequency of 100 beats per minute and normal interval ranges and a left axial deviation was shown. No ST-wave or T-wave changes were observed. With transthoracic (Figs. 1 and 2) and transoesophageal echocardiography (Fig. 3) a mildly concentric left ventricular hypertrophy with normal contraction patterns was demonstrated. Also the generally known membranous ventricular septum defect with a pressure deprevation of 86 mmHg and a mitral regurgitation with a small eccentric jet.
No leaflet defects were noticed. An echodense cardiac mass, measuring 40x35 mm in size, was located in the right atrium (Figs. 2 and 3). The conspicuous mass was located in the right atrial septum and did extend into the posterior and lateral parts of the right atrium. With additional coronary angiography normal coronary arteries were shown. A normal left ventricular function was found. Chest roentgenography demonstrated an enlarged heart and elongated aorta and emphysematous lungs and non-genetic degenerative conditions of the skeleton. A myxoma cordis or thrombus was suspected and she underwent operation. Following median sternotomy, ascending aortic cannulation with bicaval venous return was applied. The heart was arrested by antegrade crystalloid cardioplegia. First, the perimembranous defect was closed via a trans-aortic approach with 4-0 prolene sutures. Right atriotomy revealed a subendocardial lipomatous mass inside the atrial septum, the left atrium and the posterior wall of the right ventricle.With initial freeze-coupe analysis no histological signs of a malignant cardiac tumour or myxoma were seen. However, the pathologist emphasised that specific determination was needed. Due to ingrowth of the tumour into structures mentioned above, it was not possible to excise the tumour in toto, especially not inside the vena cava superior. Nevertheless the patient was successfully weaned from cardiopulmonary bypass. One hour postoperatively our patient developed congestion and cyanosis of the head and the upper extremities with increasing central venous pressure. We diagnosed an acute superior vena cava syndrome and confirmed this diagnosis with transoesophageal echocardiography, which showed and upper right atrial inflow obstruction. The patient underwent re-sternotomy with a reconstructive enlargement of the vena cava superior. The reconstruction was accomplished with a bovine pericardial patch. Inotropics were needed to wean the patient from cardiopulmonary bypass. On the 1st postoperative day she developed right ventricular failure with unknown etiology. Transoesophageal echocardiography did not contribute to a decisive answer on the diagnosis. On the 3rd postoperative day the patient developed atrium fibrillation with a right bundle branch block. Despite our interventions the situation worsened and the patient died on the 7th postoperative day. Pathohistologic examination of the resected tissue (3x3x1.5 cm) showed a typical pattern of lipomatous hypertrophy. A pattern with hypertrophic cardiac myocytes with enlarged centrally placed nuclei and partially vacuolated cytoplasm interspersed with vacuolated brown ‘foetal’ fat tissue. Moreover, post-mortem examination demonstrated a 2-cm thick transmural lipofibromatous tissue in the posterior wall of the right ventricle. Most likely, this contributed largely to the fatal right ventricular failure (Figs. 4 and 5).
Lipomatous hypertrophy of the interatrial septum (LHIS) is a rare cardiac lesion. It consists of an exaggerated growth of fat tissue existing within the atrial septum. This abnormality is more common than cardiac lipoma and is usually encountered in elderly, obese or female patients as an incidental finding during a variety of cardiac imaging procedures [4]. Since the first description by Prior in 1964, approximately 200 cases with cardiac lipomatous hypertrophy have been reported [5]. To our knowledge only one case reports a lipomatous hypertrophy of the interatrial septum involving the right ventricle [6]. It reports of an antemortem detection by transthoracic echocardiography of a lipomatous hypertrophy involving the right ventricle. Our case unfortunately describes a post-mortem diagnosed LHIS. Although LHIS is being increasingly diagnosed with the advent of newer imaging modalities, in our case we were not able to diagnose LHIS with echocardiography. On this echo the lipomatous hypertrophy of the interatrial septum presented itself as an interatrial mass with myxomatous characteristics. However, accurate tissue characterisation may not be possible using echocardiography. Computed tomography and magnetic resonance imaging are superior in tissue characterisation [3]. The most recent developments in tissue characterisation are made by Kuester et al. [7]. They describe a specific metabolic pattern on 18F fluorodeoxyglucose-positron emission tomography (FDG-PET) correlated with LHIS. It is important to recognize false-positive FDG-PET interpretations and to enable differentiation of malign cardiac fat deposits caused by malignant mediastinal tumours from benign cardiac fat deposits such as in LHIS. Although LHIS has been associated with supraventricular arrhythmias and sudden death, there are no typical symptoms and it is often asymptomatic [5]. There are only a few cases known in which surgical excision was effective. Surgical therapy appears to be reserved to patients having superior vena cava obstruction or any rhythm disturbances. We misdiagnosed a lipomatous hypertrophic interatrial septum and operated on our patient because of the assumed diagnosis of myxoma and a medical history with an episode of decompensatio cordis, supraventricular arrhythmias and her known perimembranous septum defect. In retrospect, supraventricular arrhythmia could fit the diagnosed LHIS but through autopsy we found transmural lipofibromatous tissue on the posterior wall of the right ventricle. On the other hand, histopathological findings on the right ventricle in our patient could fit with arrhytmogenic right ventricular dysplasia. But in our case the disease did not involve the left ventricular wall and with histologic evaluation of autopsy cases it has become evident that arrhytmogenic right ventricular dysplasia is a biventricular disease [8]. The main problem is differentiating LHIS from a cardiac neoplasm when the lesion is discovered with echocardiography. In conclusion, we will suggest considering LHIS as a part of the differential diagnosis for any atrial cardiac tumour. With improvements in imaging, LHIS should possibly be recognised more frequently. However, surgical resection should only be performed in symptomatic patients and in retrospect our patient should not have undergone surgery.
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Abstract
1. Introduction
