Where’s the Q-Tip?: Lipomatous Hypertrophy Mimicking a Right Atrial Mass

Licheng Lee, MD, FACC¹, Pelbreton Balfour, Jr., MD, MS, FACC, FSCMR ¹, Brittany Scothorn, RT ², Chung Nguyễn, RT <sup>2

1</sup>Division of Cardiology, Baptist Heart and Vascular Institute, Pensacola, Florida, USA
²Division of Radiology, Baptist Hospital, Pensacola, Florida, USA

Clinical History:

A 71-year old woman with a history of hypertension, hyperlipidemia, carotid arterial disease, right breast ductal carcinoma in-situ, and deep vein thrombosis (DVT) presents with worsening dyspnea while playing pickleball. Her friends have commented that she breathes heavily during play, despite having played for nearly a decade. She also reports chest discomfort and fluttering sensations both with and without exertion.

She was normotensive with a body mass index of 31, with no pertinent findings on physical exam. Lipids have been well controlled over the past three years on statin therapy. Her electrocardiogram (EKG) showed sinus rhythm, with a significant Q wave in III and small, non-significant Q waves in II, aVF (Figure 1).

Figure 1. 12-lead electrocardiogram. This shows sinus rhythm with a significant Q wave in III and small, non-significant Q waves in II, aVF. T wave inversions are present in III, aVF.

 

Her transthoracic echocardiogram (TTE) showed a mass attached to the basal wall of the right atrium measuring 1.1 x 0.8 cm (Figure 2, Movie 1), that was not seen in prior TTE studies over the previous seven years. Left ventricular ejection fraction (LVEF) was 66% with no focal wall motion abnormalities, with a mild increase in LV wall thickness with concentric remodeling.

 

Figure 2. Transthoracic echocardiogram (TTE)- Apical four chamber view. There is a mass measuring 1.1 x 0.8 cm at the basal wall of the right atrium. There is extensive mitral annular calcification in the posterior mitral annulus.

Movie 1. TTE- Apical four chamber view. The mass appears attached to the basal wall of the right atrium and is slightly mobile in appearance. Left and right ventricular systolic function are normal, with normal right atrial size.

 

She had a treadmill stress TTE study a year before that showed no ischemia. A coronary CT angiogram (CCTA) was ordered but angiography was deferred following findings of extensive calcification of the coronary arteries (Figure 3 A-B) with a very high calcium score (CAC score=1377, 98th percentile based on age, gender, and ethnicity). Given continued symptoms, she was referred for cardiac catheterization. Left and right heart catheterization were considered given her symptoms of dyspnea and chest pain. Given the right atrial mass seen by TTE, cardiovascular magnetic resonance (CMR) was pursued prior to cardiac catheterization.

 

Figure 3. Cardiac computed tomography (CT)- axial slices. A. The Agatston coronary calcium score is very high at 1377 mm³. There is calcification of the left anterior descending and circumflex arteries, as well as aortic root and descending thoracic aorta. B. There is also calcification in the right coronary artery. C-E. Axial slices from inferior to superior demonstrate the course and extend of fat from the interatrial septum, sparing the fossa ovalis, toward the base of the right atrium (solid arrow). Mitral annular calcification is also noted (open arrow). F. A Hounsfield Unit (HU) of -79 near the base of the right atrium is consistent with fat.

 

CMR Findings:

CMR was performed on a Siemens Aera 1.5 T scanner. Cine imaging showed a LVEF of 71% with no focal wall motion abnormalities and normal wall thickness. Cine four-chamber (Movie 2) and aortic valve short axis (Figure 4) views demonstrated extensive lipomatous hypertrophy of the interatrial septum, sparing the fossa ovalis, with extensive epicardial fat extending into the middle base and around the free wall of the right atrium.

Movie 2. Cardiac magnetic resonance imaging (CMR)- 4 chamber cine. Lipomatous hypertrophy in the interatrial septum and epicardial fat around the base of the right atrium have similar appearance to epicardial, pericardial, and subcutaneous fat that is seen.

Figure 4. CMR- Short axis views. Epicardial fat extends into the basal right atrium (arrow) with extensive lipomatous hypertrophy in the interatrial septum, sparing the fossa ovalis.

 

Rest perfusion imaging demonstrated absence of enhancement in these regions (Movie 3, 4) with a T1 and T2 fat saturation sequences confirming the presence of fat (Figure 5). T1 mapping demonstrated T1 values consistent with fat in the interatrial septum, adjacent to the mid-basal right atrium, as well as in the epicardium, pericardium, and posterior mitral annulus (Figure 6).

Movie 3. CMR- Rest perfusion. 4 chamber view. Rest perfusion imaging demonstrates absence of enhancement in the interatrial septum, sparing the fossa ovalis, and at the base of the right atrium, in addition to the mitral annulus.

Movie 4. CMR- Rest perfusion. Short axis view at the level of the atria. Fat is seen in the interatrial septum, sparing the fossa ovalis, and surrounds the pulmonary artery.

Figure 5. CMR- Axial views. Fat saturations sequences showing nulling of fat within the interatrial septum, base of the right atrium, epicardium, and pericardium on T1 (A) and T2 (B) weighted images.

Figure 6. CMR- T1 map. Axial view. T1 mapping demonstrates low T1 values consistent with fat in the interatrial septum (sparing the fossa ovalis), base of the right atrium, pericardium, epicardium, and posterior mitral annulus.

 

Subsequent review of cardiac CT imaging showed Hounsfield Unit (HU) measurements in these regions consistent with fat, with similar findings to those seen by CMR (Figure 3 C-F). CMR also showed a hypointense structure on cine imaging (Figure 7 A) with low T1 values by T1 mapping (Figure 6) demonstrated to be mitral annular calcification on cardiac CT (Figure 7 B).

 

Figure 7. A. CMR- Four chamber view. There is a hypointense structure with cine imaging at the posterior mitral annulus (arrow). B. Cardiac CT- Four chamber view. The typical bright appearance of calcium by CT is seen at the posterior mital annulus confirming the presence of mitral annular calcification (arrow).

Conclusion:

CMR demonstrated that the Q-tipped shaped right atrial mass seen by TTE was not an intracardiac mass, but rather due to massive lipomatous hypertrophy extending toward the middle and around the free wall of the right atrium. Lipomatous hypertrophy of the interatrial septum was present with demonstration of an absence of encapsulation that is typically seen with lipoma, and with sparing of fossa ovalis which is typical for lipomatous hypertrophy. Furthermore, T1 and T2 fat saturation imaging and T1 mapping definitively confirmed the presence of fat in these regions. Low T1 values were also seen in the posterior mitral annulus by CMR, which may be secondary to fat or calcium. Multimodality imaging with TTE and CT demonstrates that this finding is due to mitral annular calcification. With concern of embolism from an intracardiac right atrial mass being excluded, she underwent left heart catheterization that demonstrated 70% stenosis of the mid right coronary artery (Movie 5) with abnormal instantaneous wave-free ratio (iFR) of 0.68 for which she underwent intravascular lithotripsy and stenting (Movie 6). She subsequently finished cardiac rehabilitation and now has resumed her pickleball.

Movie 5. Coronary angiogram. Right anterior oblique view. There is 70% stenosis in the mid right coronary artery.

Movie 6. Coronary angiogram. Right anterior oblique view. There is no residual stenosis in the mid right coronary artery status post percutaneous coronary intervention with stenting.

 

Perspective:

This case of extensive lipomatous hypertrophy mimicking a right atrial mass illustrates the utility of CMR in distinguishing masses from pseudo-masses given its superior spatial resolution and tissue characterization. Lipomatous hypertrophy may be seen in 2-8% of cases, [1] and may surround and extend into adjacent structures. Compression of the right atrium [2] and surrounding structures such as the superior vena cava (SVC) [3-4] and right ventricular inflow [5] or outflow [6] tracts have also been described, as well as extension into the interventricular septum. [7-8] A key differential diagnosis to lipomatous hypertrophy is a lipoma, a benign, encapsulated tumor that can also compress adjacent structures such as the SVC [9] but does not spare the interatrial septum as seen with lipomatous hypertrophy. While computed tomography (CT) may demonstrate a Hounsfield Unit (HU) consistent with fat of -90 to -120 (HU) and hypodense appearance, CMR demonstrates this more definitively with complete suppression of hyperintense signal on T1 and T2 weighted images with T2 fat saturation or short tau inversion recovery (STIR) sequences. [7]

There are several diagnostic considerations for a right atrial mass seen by echocardiography. In our patient, the appearance of the right atrial mass was not in a typical location for a Eustachian valve, a vestigial structure between the inferior vena cava (IVC) and right atrium [10] or a myxoma which is typically attached to the interatrial septum. [11] Right atrial thrombus was also a consideration, given her prior history of breast cancer, but is typically catheter-associated occurring in 5.2% of patients with central venous catheters, [12] for which there was no recent history of in our patient. The right atrial mass was relatively small, suggesting a recent occurrence of extension of fat into the right atrium, given its absence on prior TTE studies. However, we cannot fully exclude that it was not present in these prior studies, given its small size and the limitations of TTE given this.

We have counseled her that progression of her lipomatous hypertrophy may result in compression of adjacent structures and symptoms, and we are aggressively managing her risk factors with lifestyle modifications and medical therapy. In this case, CMR, with its superior spatial resolution and tissue characterization, definitively demonstrated that the Q-tipped shaped mass was not an intracardiac tumor or thrombus but rather caused by extension into the right atrium from massive lipomatous hypertrophy.

 

Click here to view the entire CMR on CloudCMR.

 

References:

1. Licordari R, Manganaro R, Pistelli L, Cusmà-Piccione M, Trio O, Micari A, Di Bella G, Zito C. Lipomatous Hypertrophy of the Interatrial Septum: A Case Report and Insights from the Literature. J Cardiovasc Echogr. 2022 Apr-Jun;32(2):123-125.
2. Kotaru VPK, Martin D, Tokala H, Kalavakunta JK. Right atrial mass-multimodality imaging-Massive lipomatous hypertrophy of the atrial septum. Clin Case Rep. 2020 Oct 22;8(12):3632-3633.
3. López-Candales A. Massive lipomatous hypertrophy of the right atria. Heart Views. 2013 Apr;14(2):85-7.
4. Breuer M, Wippermann J, Franke U, Wahlers T. Lipomatous hypertrophy of the interatrial septum and upper right atrial inflow obstruction. Eur J Cardiothorac Surg. 2002 Dec;22(6):1023-5.
5. Bokhari SSI, Willens HJ, Lowery MH, Wanner A, deMarchena E. Orthodeoxia platypnea syndrome in a patient with lipomatous hypertrophy of the interatrial septum due to long-term steroid use. Chest. 2011 Feb;139(2):443-445.
6. Kato S, Kawata T, Kuwata H, Ueda T, Sakaguchi H, Taniguchi S. Cardiac liposarcoma at the right ventricular outflow tract (RVOT) following lipomatous hypertrophy of the interatrial septum (LHIS); report of a case. Kyobu Geka. 2004 Feb;57(2):143-6.
7. Subbaraman S, Rajan SC, Veeraiyan S, Natarajan P. Imaging Findings of Lipomatous Hypertrophy of the Interventricular Septum: A Case Report. Clin Med Insights Case Rep. 2021 Jun 12;14:11795476211024848.
8. Vaidya YP, Green GR. Lipomatous hypertrophy of the interventricular septum. J Card Surg. 2020 Jul;35(7):1740-1742.
9. Grech R, Mizzi A, Grech S. Compression of the superior vena cava by an interatrial septal lipoma: a case report. Case Rep Pulmonol. 2013;2013:945726. doi: 10.1155/2013/945726. Epub 2013 Aug 1.
10. Fichadiya H, Shah KK, Noori MAM, Khandait H, Rath P, Latif A, Patel R, Pullatt R. A Rare Case of Eustachian Valve Endocarditis in a Young Male With Poorly Controlled Type 1 Diabetes Mellitus. Cureus. 2022 May 25;14(5):e25314.
11. Babs Animashaun I, Akinseye OA, Akinseye LI, Akinboboye OO. Right Atrial Myxoma and Syncope. Am J Case Rep. 2015 Sep 21;16:645-7.
12. Clark JR, Hoffman SC, Shlobin NA, Bavishi A, Narang A. Incidence of catheter-associated right atrial thrombus detected by transthoracic echocardiogram. Echocardiography. 2021 Mar;38(3):435-439.

 

Case prepared by:
Rebecca Kozor, MBBS, PhD
University of Sydney
Associate Editor, Cases of SCMR