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Incidental Finding of a Lipomatous Lesion Involving the Myocardium of the Left Ventricular Wall

Brooke Army Medical Center Fort Sam Houston, TX 78234
Wilford Hall Medical Center Lackland AFB, TX 78236

An 85-year-old woman underwent CT of the abdomen for evaluation of abdominal pain. Her medical history was notable for coronary artery bypass graft, hypertension, and hyperlipidemia. On CT, a homogeneous nonenhancing hypoattenuating lesion involving the myocardium of the left lateral ventricular wall was noted (Fig. 1A) with an attenuation level of –123 H, comparable to that of fat. Additional adipose tissue was noted in the interatrial septum. Review of a CT scan of the abdomen from 4 years earlier showed the same findings with no intervening changes. The remainder of the CT examination was unremarkable. The patient denied any history of arrhythmias or conduction abnormalities. Family history was noncontributory.

View larger version (162K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1A. —85-year-old-woman with incidental finding on CT. Axial contrast-enhanced CT scan shows homogeneous hypodense lesion of left lateral ventricular wall with attenuation level of –123 H. Lesion shows irregular borders. Note concurrent lipomatous hypertrophy of intraatrial septum with no lymphadenopathy.

The patient returned for cardiac MRI, which showed normal ejection fraction and no significant wall motion abnormalities. T1-weighted and out-of-phase gradient-echo sequences verified the fatty nature of the lesion (Figs. 1B and 1C). The fatty tissue in the septum was consistent with lipomatous hypertrophy, but the lesion of the left lateral ventricular wall was less diagnostically clear. Lipoma and atypical lipomatous infiltration were both considered possibilities.

View larger version (119K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1B. —85-year-old-woman with incidental finding on CT. Cardiac MRIs show irregular thin fatty lesion involving myocardium of left lateral ventricular wall. Bright signal intensity with cardiac-gated T1-weighted sequence (TR/TE, 1,153/14) is seen in B. Signal dropout from phase cancellation consistent with fat is seen in C on bright blood gradient-echo sequence (6/2) with out-of-phase timing.

View larger version (121K): [in this window] [in a new window] [as a PowerPoint slide]   Fig. 1C. —85-year-old-woman with incidental finding on CT. Cardiac MRIs show irregular thin fatty lesion involving myocardium of left lateral ventricular wall. Bright signal intensity with cardiac-gated T1-weighted sequence (TR/TE, 1,153/14) is seen in B. Signal dropout from phase cancellation consistent with fat is seen in C on bright blood gradient-echo sequence (6/2) with out-of-phase timing.

Fatty accumulations in the heart are rare in clinical medicine. They are more commonly discovered incidentally during autopsy, where they are seen in 3% of individuals [1]. These unusual lesions can be classified in three categories: lipoma, lipomatous infiltration, and lipomatous hypertrophy [2]. When they are encountered clinically, most of these lesions arise in the interatrial septum and represent lipomatous hypertrophy, a collection of nonencapsulated fetal fat cells [1]. Lipomatous infiltration is an unencapsulated mass of fatty tissue in the myocardium. The term "fat infiltration" is a misnomer, implying invasion of the myocardium by epicardial adipose tissue, whereas the fat probably arises from metaplasia of connective tissue [1]. Myocardial lipomas are true neoplasms, composed of an encapsulated mass of mature adipose tissue.

In vivo differentiation of lipomatous infiltration and lipoma can be diagnostically challenging, if not impossible. Cardiac lipoma typically appears as a polyploid or sessile lesion arising in the subpericardium or subendocardium [3]. It is commonly associated with the left ventricle, right atrium, or interatrial septum [2]. In the unusual case of a lipoma arising in the myocardium, its appearance is atypical, being small and irregular in contour and possessing a barely definable capsule [4]. Thus, its imaging characteristics other than the capsule are identical to those of myocardial fat infiltration, which is more common, although older.

The clinical context in which these lesions are found may assist in the diagnosis. Lipomas are generally seen in younger individuals. Thirteen cadavers autopsied by the Armed Forces Institute of Pathology [4] had an average age of 44 years. In contrast, fatty infiltration occurs with greatest frequency among women in their seventh decade; our patient was fairly typical [1].

Differentiating lipomas and fatty infiltration may be more an academic exercise than a clinically valuable activity. Interatrial hypertrophy has been associated with sudden death and arrhythmia, but most cardiac lipomatous lesions are asymptomatic and are discovered incidentally during non–cardiac-related imaging or at autopsy [3]. In rare instances, large epicardial or endocardial-based lipomas have been considered as causing restrictive or obstructive symptoms for which surgical resection might be warranted. Treatment of myocardial lipomatous lesions is generally conservative, particularly if they have infiltrated the conduction system, making resection impossible [2].

References

1. Carpenter HM. Myocardial fat infiltration. Am Heart J 1962;63:491 –496[Medline]
2. Crocker DW. Lipomatous infiltrates of the heart. Arch Pathol Lab Med 1978;102:69 –72[Medline]
3. Reyes CV, Jablokow VR. Lipomatous hypertrophy of the cardiac interatrial septum. Am J Clin Pathol1979; 72:785 –788[Medline]
4. McAllister HA, Fenoglio JJ. Tumors of the cardiovascular system. In: Atlas of tumor pathology, series 2, fasc. 15. Washington, DC: Armed Forces Institute of Pathology, 1978:44 –46

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This Article Figures Only Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Banks, K. P. Articles by Lisanti, C. J. Search for Related Content PubMed PubMed Citation Articles by Banks, K. P. Articles by Lisanti, C. J. Social Bookmarking                      What's this?