Giant right atrial lipoma mimicking tamponade

Introduction

Primary tumors of the heart are rare. Nearly 75% of such tumors are benign, and the rest are malignant. Myxomas account for the majority of benign tumors, and the others are mostly lipomas, papillary fibroelastomas, and rhabdomyomas. ¹

Case report

A 56-year-old previously healthy man presented at our emergency room with worsening dyspnea and increasing fatigue for the past 2 months. Past medical history was positive for hypertension treated with losartan 25 mg twice daily, but the medication had been stopped due to hypotension in the past few weeks. The patient was an occasional smoker. He did not report any chest pain, weight loss, or cough. On physical examination, he had plethora and appeared to be in respiratory distress. His blood pressure was 90/60 mm Hg and his heart rate was 105 beats per minute. His neck veins and the superficial veins on the chest were distended. Heart auscultation revealed a II/VI systolic murmur in the left sternal border and decreased heart sounds. The lungs were clear on auscultation, with decreased breath sounds bilaterally. The oxygen saturation was 91% in room air. Routine laboratory tests were within normal limits. The erythrocyte sedimentation rate was 13 mm·h⁻¹ and C-reactive protein was negative. Electrocardiography showed atrial fibrillation with low voltage in the limb leads. Chest radiography showed global cardiomegaly with oligemic lung fields. Echocardiography was carried out with the clinical suspicion of pericardial effusion, which showed preserved function of the ventricles with biatrial enlargement and a very large immobile homogenous mass almost completely occupying the right atrium, restricting blood flow thorough the tricuspid valve (Figure 1). There was no pericardial effusion. Chest computed tomography with intravenous contrast showed a 110 × 75-mm homogeneous low-attenuation mass with thin septa, originating from the interatrial septum and filling the right atrium, suggesting a high likelihood of lipoma (Figure 2a and 2b). The patient underwent resection of the mass originating from interatrial septum, and the septum was repaired with a pericardial patch. On gross examination, the mass consisted of thinly encapsulated bright yellow fat, separated by fine fibrous trabeculae (Figure 3). Microscopic examination showed adipose tissue composed of mature fat cells (Figure 4). The postoperative course was uneventful and the patient was doing well at the 12-month follow-up visit.

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Figure 1.

Four-chamber echocardiography image showing a large mass in right atirum.

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Figure 2.

(a, b) Chest computed tomography images with contrast, showing a 95 × 75-mm homogeneous low-attenuation mass with thin septa, originating from the interatrial septum and filling the right atrium.

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Figure 3.

Gross pathologic specimen of the tumor showing a mass consisting of thinly encapsulated bright yellow fat.

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Figure 4.

Microscopic examination of the tumor showing adipose tissue composed of mature fat cells. The nuclei are fairly uniform without hyperchromasia. Cardiac muscle tissue is seen with marked hypertrophic changes.

Discussion

Cardiac lipomas account for 10% of all cardiac tumors. They occur in all ages with an equal frequency in both sexes. ² Cardiac lipomas are usually asymptomatic and may be discovered incidentally during computed tomography or magnetic resonance imaging. ³ They are well-encapsulated tumors, typically composed of mature fat cells. ¹ True cardiac lipomas are much less frequent than lipomatous hypertrophy of the interatrial septum, and occur in almost any location in the heart. ¹

The clinical manifestations of cardiac lipoma depend on the location of the tumor, and may vary from valvular dysfunction to obstruction of a cardiac chamber, impeding the filling and emptying processes. Those adjacent to valves present early with murmurs or valvular obstruction. Tumors of the right atrium, interatrial septum, and right ventricle can predispose to arrhythmias. ⁴ In our case, the tumor occupied most of the right atrium, hindering flow through the tricuspid valve, and even protruded into the right ventricle, which led to a clinical picture similar to cardiac tamponade. Approximately 50% of these tumors have a subendocardial origin, 25% have an intramyocardial origin (affecting most frequently the left ventricle, right atrium, and the interatrial septum), and the remaining 25% are of pericardial origin. ⁵ In our patient, increased right atrial pressure and distension of the right atrium or the probable intramyocardial origin of the tumor could account for the atrial fibrillation. Indications for surgery of cardiac fatty lesions are intractable arrhythmias, valvular dysfunction, inflow or outflow obstruction, a thromboembolic event, and inability to confidently exclude liposarcoma. ² This case is unique because of the large size of the lipoma, which caused underfilling of the right ventricle with rapid deterioration of symptoms at presentation, mimicking cardiac tamponade.