<div>Giant Interatrial Septal Lipoma Filling with Right Atrium Causing Slight
Symptoms: A Case Report</div><div>Mingxiang Chen MD1, Fuping Li MD1, Haitao Zhang, MD2, Zhuyun Qin MD2, *</div><div>1Department of Cardiovascular Surgery, The Third Affiliated Hospital of
Chongqing Medical University, Chongqing, China</div><div>2Adult Cardiac Surgical Intensive Care Unit, Fuwai hospital, Chinese
Academy of Medical Sciences and Peking Union Medical College, Beijing,
China</div><div>*Correspondence: Zhuyun Qin, MD, Email: qinzhuyun@163.com</div><div>Abstract: Cardiac lipoma is extremely rare. Here we presented a unique
illustrative case of interatrial septal lipoma protruding into right
atrial causing symptoms in a 54-year-old male. Echocardiogram and
computed tomography showed a well-shaped, giant and fixed occupying
located in interatrial septum and right atrium. The only manifestation
was palpitation though the mass filled almost all atrium and compressed
superior vena cava. The patient received resection of the large-sized
lipoma sizing 87mm in diameter and weighing ~1000g.
Pathological exam demonstrated mature lipocytes and substantiated the
diagnosis of lipoma. The patient did well postoperatively, and symptoms
were resolved.</div><div>Key words: cardiac tumor; cardiac lipoma; case report; literature
review;</div><div>1. Introduction</div><div>Primary cardiac tumor is rare, the incidence is in a range of 1.38 to 30
per 100,000 people per year; among adult patients over 16 years old,
benign tumors account for 80% of primary tumors and 21% of benign
tumors are lipomas1. Patients with cardiac lipoma are usually
asymptomatic and can sometimes present with various symptoms, such as
heart failure, arrhythmias, cardiac compression and valvular
obstruction. Embolization can also occur if the tumor is not well
encapsulated2. Due to the low prevalence of cardiac lipoma, currently
there is no according treatment guidelines. Patients with asymptomatic
cardiac lipoma can be clinically observed and symptomatic patients
usually accept tumorectomy. Here, we reported a unique case of an
illustrative giant cardiac lipoma located in interatrial septum and
protruded into right atrium that caused symptoms and accepted surgery
removal that evaded patching to reconstruct interatrial septum. The
report was approved by the Ethics Committee of The Third Affiliated
Hospital of Chongqing Medical University, and written informed consent
was obtained from the individuals for the publication of any images or
data included in this article. Clinical trial registration is not
applicable for this report.</div><div>2. Case Report</div><div>A 54-year-old East Asian male patient was admitted to the local hospital
with chief complaint of recurrent spontaneous paroxysmal palpitation for
1 year, this symptom became more frequent for 1 month. No aberrant signs
found on physical examination. Patient’s NT-proBNP was 493.30 pg/ml
(normal range: 0-125 pg/ml). The cardiac function of the patient was
class I on NYHA classification. The rhythm was sinus on
electrocardiogram (ECG). Echocardiogram presented an ovoid mass located
in the right atrium and tightly attached to the interatrial septum. The
border of the mass was clear except the adherent part (Figure 1A, 1B).
Left ventricular ejection fraction was 58%. Coronary computed
tomography angiography (CTA) revealed a large mass within the
interatrial septum and right atrium, taking up almost all the roof of
the right atrium and constricting the superior vena cava (SVC). The
upper part of the mass surrounded the aortic root. The size of the mass
was 58mm×87mm×52mm and the density was distinctly lower than the
peripheral tissues (Figure 1C). The patient was then diagnosed as
cardiac lipoma and received surgery through a median sternotomy under
cardiopulmonary bypass. An ovoid, yellowish and brownish mass was
exposed between right auricle and SVC after opening patient’s
pericardium (Figure 2A). The mass was well-capsulated, vessel free and
connected with interatrial septum. Through right atrial atriotomy, a
firm, lipoid change of the interatrial septum was presented. Fossa
ovalis was absent; tricuspid valve and coronary sinus were free from
affected. The sessile tumor en bloc sizing 87mm in diameter was isolated
gradually by elongating the incision to the roof of the right atrium
(Figure 2B, 2C). Interatrial septum was reconstructed by barely suturing
and there was no incidence occurred during surgery. Mass sample was
performed with hematoxylin-eosin (HE) staining. Adipocytes and
myocardial tissue were intersected under a light scope (Figure 3A). The
patient did well postoperatively, though there was an intermittent
palpitation, the symptom was obviously relieved. Postoperative CT
revealed no anomaly (Figure 3B). Frequent ventricular premature beats
were found on postoperative ECG when the patient suffering palpitation
(Figure 3C). The patient complaint no other discomfort during the next 8
days of in-hospital follow-up and eventually discharged. Patient
remained asymptomatic on the follow-up of next 15 month.</div><div>3. Discussion</div><div>Cardiac lipomas mostly occur in an age group of 40-60 years old3.
Patients with cardiac lipoma are usually asymptomatic, thus the tumor is
often found incidentally during imaging check or autopsy4. Symptoms
caused by cardiac lipoma depends on its size and location. In this
reported case, the only clinical manifestation of the patient was
palpitation. Adipocyte infiltration in myocardium attributes to
perturbation of myocardial conductivity and leads to arrhythmia5.
Although the preoperative ECG of this patient was normal, postoperative
ECG revealed frequent ventricular premature beats, alongside with the HE
staining result that mature fat cells and myocardial cells are crossing,
indicating that patient’s preoperative palpitation was probably caused
by adipocytes causing related arrhythmia. The mechanisms of adipocytes
disturb cardiac conductivity is so far poorly elucidated and still in
progress of research. Mitochondrial dysfunction, autonomic dysfunction,
autophagy, oxidative stress, mitophagy and myocardial death may all play
vital roles in inducing aberrant signals6.</div><div>Cardiac lipoma accounts for 5% of primary cardiac tumors, it develops
from mesoderm and arise subendocardially, subepicardially and
myocardially7. Among these origins, lipomas of subendocardial and
subepicardial origin are encapsulated and partially encapsulated as for
myocardial origin. Cardiac lipoma can occur anywhere in the heart, of
which interatrial septum is the most common position8. In this case,
lipoma at the right atrium was well-enclosed, while in the interatrial
septal area, no capsule was presented. It baffled the surgeons, however,
whether the origin of cardiac lipoma in this case was arising from
interatrial septum and protruding to atrium or arising from epicardium
and infiltrating to interatrial septum.</div><div>Because of the location and the traits of lipoma, interatrial septal
lipoma is usually differentiated with lipomatous hypertrophy in
interatrial septum (LHIAS). LHIAS and interatrial septal lipoma are both
benign lipomatous changes in heart, consisting of mature fat cells.
LHIAS, occurring in 2% of populations, is interspersed lipocytes grow
within interatrial septum and make it thicker than 2cm, the fossa ovalis
is usually spared1. Of note, differing from lipoma, LHIAS is
unencapsulated and presents a typical dumbbell shape on CT scan9.</div><div>Though the etiology of cardiac lipoma is under investigation, genetical
change can be strongly related. The rearrangements of two gene members
of high-motility group family, HMGA1 (formerly HMGIY,6p21) and HMGA2
(formerly HMGI-C, 12q14) have been demonstrated involving in the
pathogenesis of 65% soft tissue lipomas10. Moreover, amplification of
MDM2 and/or CPM, derived from chromosome 12q13-15, are also implicated
in lipomatous change11. Nevertheless, in one study, HMGA2 rearrangement
was found in 42% cardiac lipomas and in 43% LHIAS cases while no HMGA1
rearrangement and MDM2/CPM amplification were demonstrated in either
lipomas or LHIAS4. Therefore, genetical screening can be performed for
strengthening the diagnosis and may also be an effective prevention and
treatment of cardiac lipoma in the future.</div><div>The scarcity of cardiac lipomas brings no treatment guideline at
present. In this reported case, resection was inevitable. SVC was
deformed by the tumor, though no symptoms of obstruction were shown,
further growth of the mass could have led to potential SVC obstruction
syndrome and venal thrombus formation. Even if lipoma is benign, it can
expand in size and oppress the heart, shrinking the volume of cardiac
chambers and impairing the heart function, which can be fatal to
patients. Furthermore, due to part of this lipoma was not encapsulated,
fat liquefaction can also occur and subsequently cause fat embolism. The
surgical option can decide the outcome of patients with cardiac tumors.
Naseerullah FS et al.12 reported a large cardiac lipoma case with
surgery removal and reconstruction of atrial septum and roof of right
atrium using patch. No patch, however, was used in our case in order to
avoid risk of thrombogenesis and other unpredictable symptoms like
arrhythmias. Surgery provides 95% cure of cardiac benign tumor12,
however, surgeons should take the surgery option into consideration so
that potential hazards get evitable on patients.</div><div>Acknowledgment</div><div>All authors thank Ruoxi Sun for her assistance on providing information
about CT reading.</div><div>Disclosure Statement</div><div>The authors report no conflict of interest regarding the content.</div><div>References</div><div>1. Poterucha TJ, Kochav J, O’Connor DS, Rosner GF. Cardiac Tumors:
Clinical Presentation, Diagnosis, and Management. Curr Treat Options
Oncol. 2019;20(8):66.</div><div>2. Rainer WG, Bailey DJ, Hollis HW, Jr. Giant Cardiac Lipoma: Refined
Hypothesis Proposes Invagination from Extracardiac to Intracardiac
Sites. Tex Heart Inst J. 2016;43(5):461-464.</div><div>3. Ismail I, Al-Khafaji K, Mutyala M, et al. Cardiac lipoma. J Community
Hosp Intern Med Perspect. 2015;5(5):28449.</div><div>4. Bois MC, Bois JP, Anavekar NS, Oliveira AM, Maleszewski JJ. Benign
lipomatous masses of the heart: a comprehensive series of 47 cases with
cytogenetic evaluation. Hum Pathol. 2014;45(9):1859-1865.</div><div>5. Wong CX, Ganesan AN, Selvanayagam JB. Epicardial fat and atrial
fibrillation: current evidence, potential mechanisms, clinical
implications, and future directions. Eur Heart J. 2017;38(17):1294-1302.</div><div>6. Pabon MA, Manocha K, Cheung JW, Lo JC. Linking Arrhythmias and
Adipocytes: Insights, Mechanisms, and Future Directions. Front Physiol.
2018;9:1752.</div><div>7. Puvaneswary M, Edwards JR, Bastian BC, Khatri SK. Pericardial lipoma:
ultrasound, computed tomography and magnetic resonance imaging findings.
Australas Radiol. 2000;44(3):321-324.</div><div>8. Monti L, Scardino C, Nardi B, Balzarini L. Lipoma of the
interventricular septum. Eur Heart J. 2015;36(44):3073.</div><div>9. Hudzik B, Filipiak K, Zembala M, et al. Lipomatous hypertrophy of the
interatrial septum: a rare cause of right ventricular impairment. J Card
Surg. 2010;25(2):171-174.</div><div>10. Rodriguez FJ, Erickson-Johnson MR, Scheithauer BW, Spinner RJ,
Oliveira AM. HMGA2 rearrangements are rare in benign lipomatous lesions
of the nervous system. Acta Neuropathol. 2008;116(3):337-338.</div><div>11. Erickson-Johnson MR, Seys AR, Roth CW, et al. Carboxypeptidase M: a
biomarker for the discrimination of well-differentiated liposarcoma from
lipoma. Mod Pathol. 2009;22(12):1541-1547.</div><div>12. Naseerullah FS, Javaiya H, Murthy A. Cardiac Lipoma: An
Uncharacteristically Large Intra-Atrial Mass Causing Symptoms. Case Rep
Cardiol. 2018;2018:3531982.</div>