Lipomatous atrial septal hypertrophy with epicardial fat extension: Case report

Yogesh Shilimkar; K Jayaprakash; Cicy Bastian; V Sudhakumary; Suresh Madhavan; VL Jayaprakash

doi:10.4103/khj.khj_5_21

CASE REPORT

Year : 2021 | Volume : 10 | Issue : 2 | Page : 19-22

Lipomatous atrial septal hypertrophy with epicardial fat extension: Case report

Yogesh Shilimkar, K Jayaprakash, Cicy Bastian, V Sudhakumary, Suresh Madhavan, VL Jayaprakash
Department of Cardiology, Government Medical College, Kottayam, Kerala, India

Date of Web Publication

14-Feb-2022

Correspondence Address:
Dr. K Jayaprakash
Department of Cardiology, Government Medical College, Kottayam, Kerala.
India

Source of Support: None, Conflict of Interest: None

DOI: 10.4103/khj.khj_5_21

Abstract

Lipomatous atrial septal hypertrophy (LASH) is a benign lesion characterized by massive accumulation of fat in the interatrial septum. Multimodality imaging, with echocardiography being the first technique, complemented by multislice computed tomography or magnetic resonance imaging help to make accurate diagnosis. Here, we report a case with a LASH with epicardial fat extension causing aneurysmal dilatation of left superior pulmonary vein with thrombus formation and pericardial effusion.

Keywords: Epicardial, lipomatous, septal

How to cite this article:
Shilimkar Y, Jayaprakash K, Bastian C, Sudhakumary V, Madhavan S, Jayaprakash V L. Lipomatous atrial septal hypertrophy with epicardial fat extension: Case report. KERALA HEART J 2021;10:19-22

How to cite this URL:
Shilimkar Y, Jayaprakash K, Bastian C, Sudhakumary V, Madhavan S, Jayaprakash V L. Lipomatous atrial septal hypertrophy with epicardial fat extension: Case report. KERALA HEART J [serial online] 2021 [cited 2023 Mar 30];10:19-22. Available from: http://www.csikhj.com/text.asp?2021/10/2/19/337622

Introduction

Lipomatous atrial septal hypertrophy (LASH) is a benign lesion characterized by massive accumulation of fat in the interatrial septum that exceeds 2 cm in thickness.^[1] LASH is associated with advanced age, obesity, and may be associated with an increased risk for atrial arrhythmias. It is more common in women. Here, we report a case of LASH with extensive epicardial lipomatosis and briefly review the existing literature about the disease.

Case presentation

A 73-year-old woman presented with complaints of breathlessness on exertion and intermittent palpitations for 6 months. There was no history of chest pain, orthopnea, paroxysmal nocturnal dyspnea, or pedal edema. No previous history of diabetes mellitus, systemic hypertension, or coronary artery disease was found. On physical examination, pulse was 74/min, irregularly irregular, an blood pressure was 130/80 mm Hg. Cardiovascular (CVS) examination was normal, and other systems were normal. Her electrocardiogram (ECG) showed irregular rhythm with more than three different morphologies of P waves suggestive of wandering atrial pacemaker and poor progression of R waves in precordial leads. Chest X-ray showed cardiomegaly, contributed mainly by the enlarged right atrium [Figure 1]. Transthoracic echocardiography (TTE) showed moderate pericardial effusion and a massive hyperechogenic mass in the interatrial septum [Figure 2]. Transesophageal echocardiography (TEE) showed characteristic dumbbell-shaped mass sparing the fossa ovalis [Figure 3]. Computed tomography (CT) thorax [Figure 4] showed nonencapsulated fat density area in interatrial septum suggestive of LASH with extensive epicardial lipomatosis. Fat density areas on right lateral aspect of superior vena cava and in pericardial cavity with moderate pericardial effusion were noted. There was aneurysmal dilatation of left superior pulmonary vein and pulmonary vein varix with thrombus. After completing the investigation, we initiated a β-blocker, diuretics, and an anticoagulant (warfarin). The patient was reassured about the benign nature of the lipomatous lesion and discharged with a recommendation for regular follow-up.

Figure 1: Chest X-ray showing cardiomegaly

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Figure 2: Apical four-chamber view showing interatrial septal mass (LA = left atrium, RA = right atrium, LV = left ventricle, RV = right ventricle)

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Figure 3: Transesophageal echocardiographic image of the dumbbell-shaped mass sparing fossa ovalis (maximum thickness 40 mm) (RA = right atrium, LA = left atrium)

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Figure 4: CT thorax (with contrast) showing lipomatous atrial septal hypertrophy with epicardial fat extension and pericardial effusion (LA = left atrium, RA = right atrium, LV = left ventricle, RV = right ventricle, LASH = lipomatous atrial septal hypertrophy)

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Discussion

LASH is a histologically benign lesion of the heart characterized by excessive fat deposition in the region of the interatrial septum. The magnitude of fat accumulation is defined as >2.0 cm in thickness.^[1] The reported prevalence ranges from 2.2% in patients undergoing multislice CT to approximately 8% in patients referred for TEE.^[1],[2] Although the majority of patients with LASH remain asymptomatic, it is infrequently accompanied by atrial arrhythmias and even more rarely by malignant arrhythmias and sudden cardiac death.^[1]

Although LASH is technically referred to as lipomatous hypertrophy of the interatrial septum, this is a misnomer.^[3] Anatomically, the true interatrial septum is confined to region of the fossa ovalis and the area just below the fossa near the orifice of the tricuspid valve (the septum primum). The muscular rim surrounding the fossa in the superior, anterior, and posterior margins (the embryologic septum secundum) is in fact an infolding of the atrial wall extending into the right atrial cavity with epicardial fat on the outside.^[4] These infoldings are sometimes referred to as Søndergaard’s groove or Waterson’s groove.^[3] During embryogenesis, the right and left atria are divided by progressive in-folding of the roof and upper anterior/posterior walls of the rudimentary common chamber along the midline. Mesodermal tissues are drawn into the wall of the primitive atrial septum during this process and pockets of entrapped adipose tissue remain after the heart is fully formed. The fat accumulation of so-called LASH does not actually occur within the true septal tissue but rather in infoldings of the atrial wall adjacent to the true interatrial septum.

Histologically, LASH is characterized by myocardial fibers, infiltrated with mature adipose cells, which are interspersed with fetal fat cells. The fat accumulation is cephalad and caudal to the fossa ovalis, accompanied by sparing of the fossa ovalis itself, which gives LASH its characteristic “dumbbell” shape. The cephalad thickening is usually more extensive than the caudad, and both masses project into the right atrial cavity. Furthermore, the cephalad component is contiguous with rest of the subepicardial fat, which is generally markedly increased in patients with LASH.^[5] In the present patient, the CT image of the chest accurately depicts the bilobed, massive collection of interatrial fat projecting toward the right atrium.

Some case reports have shown that LASH might lead to a variety of rhythm disturbances such as P-wave abnormalities, atrial fibrillation and even sudden death.^[6] Malignant cardiac arrhythmias may occur as a result of extensive bleeding into the lesion. The mechanism of how LASH causes cardiac rhythm abnormalities is still unknown. It is suspected that the involvement of the interatrial septum and the wall of the right atrium, especially in patients with large lesions, interferes with the architecture of atrial myocytes, which could affect conducting pathways.^[1]

The differential diagnosis of LASH includes benign and malignant cardiac tumors involving the interatrial septum, such as metastases, myxomas, and mesotheliomas. Myxomas arise from the interatrial septum near the fossa ovalis and typically have a stalk, whereas lipomas are encapsulated. Imaging techniques can thus differentiate these entities from LASH, which is noncapsulated and always spares the fossa ovalis.^[7] Cardiac liposarcoma, a rare entity that predominantly appears in the right atrium, is a rapidly growing tumor with early signs of local invasion and hemodynamic comprise. Intraseptal cardiac liposarcomas have never been described.

A number of imaging modalities, including echocardiography, CT, and cardiac magnetic resonance imaging, have been used for the diagnosis of LASH. Two-dimensional TTE and TEE are the diagnostic modalities of choice^[8] because these modalities are widely available. In our case, the patient was elderly, and TTE and TEE showed hypertrophy of the proximal and distal portions of the atrial septum with sparing of the fossa ovalis (dumbbell shape). The previously mentioned characteristic appearance and location of LASH help in echocardiographic differentiation from cardiac tumors.

CT can be helpful for the differential diagnosis of LASH from malignancies, because of their different relative densities. In particular, LASH has the pathognomonic attenuation coefficient of adipose tissue, which is absent in neoplasms.^[5] In our case, the density of the interatrial mass is identical to that of the excessive subepicardial tissue over the anterior right ventricle; the attenuation coefficient (–60 to –100 Hounsfield units) of the tissue at each of these sites confirms that each represents adipose tissue.

The role of cardiac magnetic resonance imaging is crucial in determining the borders of LASH and the extension into the interventricular septum and the ventricular free wall. Furthermore, it can provide valuable information regarding lesion composition (fat, solid, cystic, or fibrous tissue).^[9]

Our case shows the importance of a multimodality approach in patients with LASH. The optimal therapeutic management of patients with LASH consists of timely diagnosis, patient reassurance, and close follow-up. Nevertheless, surgical resection and septal reconstruction are possible therapeutic interventions in very rare cases of lesions that cause circulatory obstruction or malignant arrhythmias.^[10]

Conclusion

LASH is a benign lesion of the interatrial septum, often asymptomatic. There is a clear scope for combining imaging modalities, with echocardiography being the first technique to provide evidence of the disease and then multislice CT or magnetic resonance imaging (MRI) delineating further the preliminary findings, as was the case in our patient. Surgical intervention is usually avoided and the best management is early diagnosis, reassurance. However, in cases of severe superior vena cava obstruction or intractable rhythm disturbance, surgical excision is performed together with reconstruction of the interatrial septum.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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