AJR 2001; 176:1066-1068
© American Roentgen Ray Society
Electron Beam CT in the Diagnosis of Recurrent Cardiac Lipoma
T. H. Wiese1,
C. N. H. Enzweiler1,
A. C. Borges2,
M. Beling2,
P. Rogalla1,
M. Taupitz1,
G. Baumann2 and
B. Hamm1
1
Department of Radiology, Charité, Campus
Berlin Mitte, Humboldt University Berlin, Schumannstr. 20/21, 10117 Berlin,
Germany.
2
Medical Department I, Charité, Campus Berlin
Mitte, Humboldt University Berlin, 10117 Berlin, Germany.
Received June 1, 2000;
accepted after revision August 2, 2000.
Address correspondence to T. H. Wiese.
Introduction
Primary tumors of the heart are rare, and among these rare tumors, primary
cardiac lipomas are an even rarer subgroup. We report the case of a recurrent
cardiac lipoma in a 34-year-old woman. The tumor was revealed on electron beam
CT and contrast-enhanced echocardiography.
Case Report
A 34-year-old woman had undergone resection of a tumor infiltrating her
left ventricle 13 years earlier. The tumor was histologically classified as a
lipoma. After the operation, the patient developed persistent ventricular
arrhythmia with recurrent ventricular flutter that necessitated the insertion
of an automatic implantable cardioverter—defibrillator. The chest
radiograph obtained at that time showed borderline enlargement of the heart
and a shoulderlike widening of the cardiac silhouette toward the left side
(Fig. 1A). Multiplanar
transesophageal echocardiography (SSA-270A; Toshiba, Tokyo, Japan) depicted an
anteroapical structure with an inhomogeneous echotexture. We performed
transthoracic contrast-enhanced echocardiography using 10 mL of galactose
palmitic acid—coated microbubbles (4 g, 400 mg/mL, SHU 508A, Levoist;
Schering, Berlin, Germany) with second harmonic imaging (HDI 3000cv; Advanced
Technology Laboratories, Bothell, WA). The resultant images showed a
hypoechoic nonenhancing epicardial tumor extending into the myocardium of both
ventricles (Fig. 1B). Because
we suspected that the patient had recurrent cardiac lipoma, we performed
electron beam CT (C150; Imatron, San Francisco, CA; ECG triggering,
single-slice mode, 3-mm slice thickness, 3-mm table feed, 100-msec exposure
time, IV bolus injection of contrast material) that revealed a tumor that had
the density of fat near the heart base at the left ventricle. The tumor had a
maximal extension of 5 x 3.5 cm and showed signs of infiltration into
the apex and lateral wall of the left ventricle, the septum, the right
ventricular myocardium, and the heart base (Figs.
1C,1D,1E,1F).
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Fig. 1B. —34-year-old woman with recurrent infiltrating cardiac lipoma.
Transthoracic contrast-enhanced echocardiogram with second harmonic imaging
shows hypoechoic nonenhancing epicardial tumor (arrow) extending into
myocardium (asterisks) of both ventricles.
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Fig. 1D. —34-year-old woman with recurrent infiltrating cardiac lipoma.
Axial electron beam CT scan shows tumor (asterisk) with density of
fat infiltrating lateral wall of left ventricle, right ventricle, and
septum.
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Discussion
Primary tumors originating in the heart are very rare, with an incidence of
0.0017-0.01% reported in the literature
[1]. The ratio of primary to
secondary cardiac tumors has been determined to range from 1:13 to 1:39
[2]. Researchers who conducted
an autopsy study over a 20-year period identified only seven primary heart
tumors in 12,485 autopsies, and among these tumors, only a single one was
cardiac lipoma [3].
Primary cardiac lipomas are thus extremely rare benign tumors of the heart
that originate in the epicardial or pericardial fatty tissue
[2]. The most common sites of
cardiac lipomas are the right atrium, left ventricle, and interatrial septum.
Approximately 25% of all cardiac lipomas are confined to the muscular layer
[4].
Histologically, tumors may consist exclusively of mature fatty tissue cells
(lipoma), or they may also contain connective-tissue cells (fibrolipoma) or
muscle cells (myolipoma) [2].
Intratumoral calcifications may be seen as a result of fatty tissue necrosis
[2,
4].
Cardiac lipomas are typically surrounded by a capsule that makes them easy
to delineate, as we observed in parts of the tumor in our patient. However,
diffuse infiltrating growth has also been reported in the literature
[1].
Cardiac tumors are often difficult to diagnose clinically because most
patients remain asymptomatic for a long time or present with nonspecific signs
such as unclear enlargement of the heart, symptoms of cardiac compression,
cardiac insufficiency, and arrhythmia
[2]. These symptoms were
present in our patient.
Tumors extending into the left ventricular outlet may cause symptoms of
subvalvular aortic stenosis
[2]. Direct involvement of the
heart valves, which has been reported for the tricuspid and mitral valves
[5], leads to valve
insufficiency [2].
The standard imaging modalities for the diagnostic assessment of lipomas
and of all other cardiac tumors are two-dimensional transthoracic and
transesophageal echocardiography, which are sensitive methods for determining
both the extent of a tumor and its effect on cardiac function. Transesophageal
echocardiography can also be used for echocardiographic monitoring of
transvenous biopsies of tumors in the right heart cavities and in the left
ventricle for histologic assessment
[5].
Recent reports suggest that the new techniques of three-dimensional
echocardiography yield important additional diagnostic information, especially
when they are used in combination with multiplanar two-dimensional
echocardiography.
Besides echocardiography, angiocardiography can be used to assess cardiac
tumors [1], by identifying
tumors on the basis of gaps in contrast enhancement
[6]. However, these gaps may be
difficult to differentiate from gaps caused by intracavitary thrombi. Other
signs of cardiac tumors are thickening of the cardiac wall as well as
accompanying vessel occlusions or compressions
[6].
CT and MR imaging provide important additional information, for instance,
on the exact extension of the tumor and possible infiltration of adjacent
organs or of the myocardium
[7]. In addition, CT and MR
imaging yield initial information for tissue characterization by depicting the
typical densities or signal intensities of the corresponding tissue types.
MR imaging is superior to CT and echocardiography in assessing the extent
of the tumor in a patient's myocardium and pericardium. Unlike CT, MR imaging
does not require the use of contrast material or ionizing radiation. Another
advantage of MR imaging is that it provides direct visualization of the tumor
in different planes [7]. On
standard T1-weighted spin-echo images, fatty tissue tumors appear hyperintense
and thus contrast with the rather hypointense myocardium
[7].
Disadvantages of MR imaging in the diagnostic assessment of cardiac tumors
include the fact that ECG triggering relies on a rather stable cardiac rhythm.
In our patient, MR imaging was not possible because of the implanted
defibrillator. Therefore, we had to rely on CT. On CT scans, cardiac lipomas
show densities that resemble the density of fatty tissue and are thus clearly
demarcated from the myocardium
[7].
In contrast to helical CT, electron beam CT does not use a rotating X-ray
tube and thus has ultrashort exposure times—as short as 50 msec per
image acquisition—resulting in a high temporal resolution while at the
same time reducing motion artifacts
[8].
A three-dimensional reconstruction of the tumor is achieved by
ECG-triggered data acquisition in the single-slice mode with subsequent image
postprocessing using shaded-surface display, maximum intensity projection, and
multiplanar reconstruction. Data acquisition in the cine mode permits
assessment of tumor mobility and its possible displacement beyond the
atrioventricular valves.
Conclusion
We described the rare case of a patient with an infiltrating cardiac
lipoma. To our knowledge, this is the first patient in whom the cardiac lipoma
was assessed by electron beam CT.
Fast, ECG-triggered image acquisition; reduced motion artifacts; and the
natural difference between the densities of fatty tissue and myocardium make
electron beam CT a modality well suited for assessing the extent of cardiac
lipomas.
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Introduction
Case Report
