FDG Uptake in Lipomatous Hypertrophy of the Interatrial Septum Is Not Likely Related to Brown Adipose Tissue

Incidental Detection of Lipomatous Hypertrophy of the Interventricular Septum on FDG PET/CT

ABSTRACT

Cardiac lipomatous hypertrophy is a rare benign condition almost exclusively involving the interatrial septum. Interventricular septum involvement is seldom noted, with only a few documented case reports demonstrating the finding on various modalities such as ECHO, CT, and MRI. FDG PET can be a surrogate marker for lipomatous hypertrophy of the interventricular septum. Here, we describe a case of incidentally detected lipomatous hypertrophy of the interventricular septum on FDG PET/CT in a patient with squamous cell carcinoma of the oropharynx.

Myocardial metastasis within lipomatous hypertrophy of the interatrial septum

A 74-year-old lady with lipomatous hypertrophy of the interatrial septum presented with symptomatic anemia. Imaging revealed a new diagnosis of metastatic cancer of presumed lung origin, with a new soft tissue myocardial lesion adjacent to the right atrium within the region of lipomatous hypertrophy. This was favored to represent a myocardial metastasis within concurrent lipomatous hypertrophy of the interatrial septum.

Extinction of Lipomatous Hypertrophy of the Interatrial Septum FDG Uptake With Propranolol Premedication

ABSTRACT

Lipomatous hypertrophy of the interatrial septum is a rare lesion of the heart. CT and cardiac MR are often sufficient to determine the benign lipomatous nature of the tumor and can avoid the need for histological confirmation. Lipomatous hypertrophy of the interatrial septum contains variable amounts of brown adipose tissue, resulting in different degrees of 18 F-FDG uptake in PET. We report the case of a patient with an interatrial lesion suspected of malignancy, discovered on CT and failing cardiac MR, with initial 18 F-FDG uptake. Final characterization was made thanks to 18 F-FDG PET with β-blocker premedication, avoiding an invasive procedure.

Increased 18F-PSMA and 18F-FDG Uptake in Lipomatous Hypertrophy of the Interatrial Septum

ABSTRACT

Lipomatous hypertrophy of the interatrial septum (LHIS) is a benign anomaly with low prevalence. Lipomatous hypertrophy of the interatrial septum is asymptomatic in most of the cases and rarely leads to atrial arrhythmias, obstructive flow symptoms, or sudden death. It is mostly diagnosed as an incidental finding in cross-sectional imaging and echocardiography, and increased 18F-FDG uptake on LHIS has been described. We present a case of repeated increased 18F-PSMA uptake in LHIS. Although very rare, familiarity with the typical features and prevalence of LHIS in PET/CT can avoid misinterpretation for metastatic disease.

Multimodality imaging to distinguish between benign and malignant cardiac masses

BACKGROUND

To compare the diagnostic accuracy of CMR and FDG-PET/CT and their complementary role to distinguish benign vs malignant cardiac masses.

METHODS

Retrospectively assessed patients with cardiac mass who underwent CMR and FDG-PET/CT within a month between 2003 and 2018.

RESULTS

72 patients who had CMR and FDG-PET/CT were included. 25 patients (35%) were diagnosed with benign and 47 (65%) were diagnosed with malignant masses. 56 patients had histological correlation: 9 benign and 47 malignant masses. CMR and FDG-PET/CT had a high accuracy in differentiating benign vs malignant masses, with the presence of CMR features demonstrating a higher sensitivity (98%), while FDG uptake with SUVmax/blood pool ≥ 3.0 demonstrating a high specificity (88%). Combining multiple (> 4) CMR features and FDG uptake (SUVmax/blood pool ratio ≥ 3.0) yielded a sensitivity of 85% and specificity of 88% to diagnose malignant masses. Over a mean follow-up of 2.6 years (IQR 0.3-3.8 years), risk-adjusted mortality were highest among patients with an infiltrative border on CMR (adjusted HR 3.1; 95% CI 1.5-6.5; P = .002) or focal extracardiac FDG uptake (adjusted HR 3.8; 95% CI 1.9-7.7; P < .001).

CONCLUSION

Although CMR and FDG-PET/CT can independently diagnose benign and malignant masses, the combination of these modalities provides complementary value in select cases.

Interatrial septum: A pictorial review of congenital and acquired pathologies and their management

There are many different congenital abnormalities and acquired pathologies involving the interatrial septum. Differentiation of these pathologies significantly affects patient management. We have reviewed the various interatrial septal pathologies and discussed their congenital associates, clinical significance, and management. After reading this article, the reader should be able to better characterize the interatrial septal pathologies using the optimal imaging tools, and have a better understanding of their clinical significance and management.

Lipomatous Atrial Septal Hypertrophy: A Review of Its Anatomy, Pathophysiology, Multimodality Imaging, and Relevance to Percutaneous Interventions

Lipomatous atrial septal hypertrophy (LASH) is a histologically benign cardiac lesion characterized by excessive fat deposition in the region of the interatrial septum that spares the fossa ovalis. The etiology of LASH remains unclear, though it may be associated with advanced age and obesity. Because of the sparing of the fossa ovalis, LASH has a pathognomonic dumbbell shape. LASH may be mistaken for various tumors of the interatrial septum. Histologically, LASH is composed of both mature and brown (fetal) adipose tissue, but the role of brown adipose tissue remains unclear. In interventional procedures requiring access to the left atrium, LASH may interfere with transseptal puncture, as traversing the thickened area can reduce the maneuverability of catheters and devices. This may cause the needle to enter the epicardial space, causing dangerous pericardial effusions. LASH was once considered a contraindication to percutaneous device closure of atrial septal defects because of an associated increased risk for incorrect device deployment. However, careful attention to preprocedural imaging and procedural intracardiac echocardiography enable interventional cardiologists to perform procedures in patients with LASH without serious complications. In this review article, the authors describe anatomic and functional aspects of LASH, with emphasis on their roles in percutaneous interventions.

A rare case of regressively changed lipomatous hypertrophy of the interatrial septum presenting with anemia and recurrent fever

Lipomatous hypertrophy of the interatrial septum (LHIS) is characterized by excessive accumulation of adipose tissue within some segments of the interatrial septum. Only one published case so far describes fever as a presenting feature of LHIS. On the other hand, systemic symptoms including anemia and fever are well-known clinical presentations of cardiac myxomas. We report an unusual case of a 79-year-old woman who was thoroughly but unsuccessfully investigated for recurrent fever and anemia in several specialized departments over the course of 4 years. Computed tomography scan showed a pathological mass localized in the interatrial septum and spreading to ascending aorta. Histological analysis of the biopsy samples from surgery revealed the unexpected diagnosis of regressively changed LHIS. We discuss the clinical and pathologic features of this lesion suggesting that its regressive changes may be associated with inflammation and can cause systemic symptoms such as fever and anemia.

Positron Emission Tomography Computed Tomography: A Guide for the General Radiologist

Cancer remains a leading cause of death in Canada and worldwide. Whilst advances in anatomical imaging to detect and monitor malignant disease have continued over the last few decades, limitations remain. Functional imaging, such as positron emission tomography (PET), has improved the sensitivity and specificity in detecting malignant disease. In combination with computed tomography (CT), PET is now commonly used in the oncology setting and is an integral part of many cancer patients' pathways. Although initially the CT component of the study was purely for attenuation of the PET imaging and to provide anatomical coregistration, many centers now combine the PET study with a diagnostic quality contrast enhanced CT to provide one stop staging, thus refining the patient's pathway. The commonest tracer used in everyday practice is FDG (F18-fluorodeoxyglucose). There are many more tracers in routine clinical practice and those with emerging roles, such as 11C-choline, useful in the imaging of prostate cancer; 11C-methionine, useful in imaging brain tumours; C11-acetate, used in imaging hepatocellular carcinomas; 18F-FLT, which can be used as a marker of cellular proliferation in various malignancies; and F18-DOPA and various 68Ga-somatostatin analogues, used in patients with neuroendocrine tumours. In this article we concentrate on FDG PETCT as this is the most commonly available and widely utilised tracer now used to routinely stage a number of cancers. PETCT alters the stage in approximately one-third of patients compared to anatomical imaging alone. Increasingly, PETCT is being used to assess early metabolic response to treatment. Metabolic response can be seen much earlier than a change in the size/volume of the disease which is measured by standard CT imaging. This can aid treatment decisions in both in terms of modifying therapy and in addition to providing important prognostic information. Furthermore, it is helpful in patients with distorted anatomy from surgery or radiotherapy when there is suspicion of recurrent or residual disease. FDG PETCT is not specific for malignancy and can also be used for diagnosing and monitoring a number of inflammatory and infectious conditions that can be difficult to diagnose on anatomical imaging, some of which carry significant morbidity. FDG PETCT is increasingly used in patients with pyrexia of unknown origin and in patients with metastatic malignancies of unidentified primary on conventional imaging. This article reviews the uses of PETCT including an overview of the more common incidental lesions and conditions. It also provides guidance of how to approach a PETCT as a nonradionuclide radiologist and how to interpret a study in the multidisciplinary team setting.

Persistent high grade flurodeoxyglucose uptake in lipomatous hypertrophy of the interatrial septum on dual time point imaging and with ambient warming

Lipomatous hypertrophy of the interatrial septum (LHIS) is a relatively uncommon disorder of the heart characterized by benign fatty infiltration of the interatrial septum that usually spares the fossa ovalis. LHIS showing flurodeoxyglucose uptake has been reported, and is presumed to be due to activated brown adipose tissue (BAT). We here report a case of a patient who had isolated mediastinal uptake in interatrial septum, mimicking metastasis. Rescanning with external warming to deactivate BAT and a delayed time point image was done, which showed persistent and progressively increasing metabolic uptake respectively, suggesting that LHIS uptake might be unrelated to activated BAT or inflammation.