CT appearance of lipomatous hypertrophy of the interatrial septum

Epicardial Space: Comprehensive Anatomy and Spectrum of Disease

The epicardial space (ES) is the anatomic region located between the myocardium and the pericardium. This space includes the visceral pericardium and the epicardial fat that contains the epicardial coronary arteries, cardiac veins, lymphatic channels, and nerves. The epicardial fat represents the main component of the ES. This fat deposit has been a focus of research in recent years owing to its properties and relationship with coronary gossypiboma plaque and atrial fibrillation. Although this region is sometimes forgotten, a broad spectrum of lesions can be found in the ES and can be divided into neoplastic and nonneoplastic categories. Epicardial neoplastic lesions include lipoma, paraganglioma, metastases, angiosarcoma, and lymphoma. Epicardial nonneoplastic lesions encompass inflammatory infiltrative disorders, such as immunoglobulin G4-related disease and Erdheim-Chester disease, along with hydatidosis, abscesses, coronary abnormalities, pseudoaneurysms, hematoma, lipomatosis, and gossypiboma. Initial imaging of epicardial lesions may be performed with echocardiography, but CT and cardiac MRI are the best imaging modalities to help characterize epicardial lesions. Due to the nonspecific onset of signs and symptoms, the clinical history of a patient can play a crucial role in the diagnosis. A history of malignancy, multisystem diseases, prior trauma, myocardial infarction, or cardiac surgery can help narrow the differential diagnosis. The diagnostic approach to epicardial lesions should be made on the basis of the specific location, characteristic imaging features, and clinical background. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Visceral adiposity in patients with lipomatous hypertrophy of the interatrial septum

Lipomatous hypertrophy of the interatrial septum (LHIS) is a benign cardiac mass determined by abnormal deposition of adipose tissue in the interatrial septum. The quantitative relationship between LHIS and visceral adiposity has not been explored to date.In this retrospective study, three groups of consecutive patients undergoing CT imaging were enrolled: L + with LHIS, L- without LHIS, and LO- without both LHIS and history of malignancies. Areas of total adipose tissue (TAT), visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT) and LHIS areas were calculated on CT images. The relationship between LHIS and abdominal fat distribution was investigated with linear regression models. Bonferroni correction was applied to account for multiple testing. Statistical significance was set at 5%. In this study we enrolled a total of 175 subjects: 58 (33.14%) with LHIS (L +), 51(29.14%) without LHIS (L-) and 66 (37.71%) without both LHIS and medical history of malignancies (LO-). VAT (coeff: 105.82; 95% CI 59.37-152.27), SAT (coeff: 74.59; 95% CI 31.63-117.54), and TAT (coeff: 190.37; 95% CI 115.02-265.72), were significantly higher in L + patients. Moreover, VAT (coeff: 24.95; 95% CI 6.94-42.96) and TAT (coeff: 36.58; 95% CI 8.75-64.41) were statistically significant linear predictors for LHIS area. Here, we report a novel association between LHIS and visceral adiposity using a quantitative CT-based imaging approach. The results are of great importance also because they might drive early identification of subjects with LHIS at risk for visceral obesity, and trigger lifestyle interventions aimed at weight loss.

A Confounder in the Study of a Patient With Infective Endocarditis

Positron emission tomography (18FDG PET-CT) is a widely used method to help in the diagnosis of infective endocarditis (IE). Lipomatous hypertrophy of the interatrial septum (LHIS) is an uncommon fat deposition in the region of the interatrial septum. PET-CT images of LHIS may be indistinguishable from changes associated with IE.

Uncommon Incidental Diagnosis of Lipomatous Hypertrophy of the Interatrial Septum

Lipomatous hypertrophy of the interatrial septum (LHIS) is a benign non-neoplastic cardiac lesion that previously has not been readily described, but with the increasing usage of computed tomography and echocardiography, this is now becoming a more well-characterized incidental finding. This case highlights an incidental finding of LHIS while a patient was undergoing treatment for a routine gastrointestinal bleed.

The diagnostic value of magnetic resonance imaging compared to computed tomography in the evaluation of fat-containing thoracic lesions

Intrathoracic fat-containing lesions may arise in the mediastinum, lungs, pleura, or chest wall. While CT can be helpful in the detection and diagnosis of these lesions, it can only do so if the lesions contain macroscopic fat. Furthermore, because CT cannot demonstrate microscopic or intravoxel fat, it can fail to identify and diagnose microscopic fat-containing lesions. MRI, employing spectral and chemical shift fat suppression techniques, can identify both macroscopic and microscopic fat, with resultant enhanced capability to diagnose these intrathoracic lesions non-invasively and without ionizing radiation. This paper aims to review the CT and MRI findings of fat-containing lesions of the chest and describes the fat-suppression techniques utilized in their assessment.

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.

Mitral valve papillary fibroelastoma as a cause of acute coronary syndrome

A 37-year-old man presented with acute chest pain, an unremarkable ECG and mildly elevated cardiac troponin. Coronary CT angiography showed a calcium score of 0 together with the absence of atherosclerotic plaques and normal origin and course of the coronary arteries. Transthoracic and transoesophageal echocardiography revealed an infracentimetric round-shaped mobile mass attached to a secondary tendinous chord of the anterior mitral valve leaflet. Cardiac magnetic resonance further evidenced localised contrast uptake supporting vascular irrigation, making thrombus unlikely. After surgical excision, the patient had an uneventful postoperative course. Histopathology disclosed the typical collagenous matrix covered by a single cell layer. Although mostly benign, cardiac tumours are prone to embolisation and can thus mimic an acute coronary syndrome. Multimodality imaging has an important role in unmasking the true mechanism, revealing less common aetiologies and elucidating the possibility of curative surgical resection.

Lipomatous hypertrophy of the atrial septum - a benign heart anomaly causing unexpected surgical problems: a case report

BACKGROUND

Lipomatous hypertrophy of the atrial septum (LHAS) is an anomaly of the heart. It is characterized by an infiltration of adipocytes into myocytes of the interatrial septum, sparing the fossa ovalis, which gives a characteristic hourglass-shaped image. Due to the progress in imaging techniques, it can be recognized more frequently, but it is still often misdiagnosed.

CASE PRESENTATION

We present a case of 65-year-old woman with an incidentally discovered lipomatous hypertrophy of the atrial septum during cardiac surgery, which has caused the technical problems for surgeons with bicaval cannulation and visualization of the operated structures of the heart. Due to the unclear shadow in the lung parenchyma, the patient had preoperative computed tomography (CT) done, but the study report focused only on the lung description, neglecting visible changes in the structure of the heart. Based on the standardly performed intra-operative transesophageal echocardiography (TEE), as well as by analyzing the chest X-ray and CT scans, the diagnosis of LHAS was made. It allowed the surgeon to leave the mass intact, thus not increasing the risk of the baseline surgery.

CONCLUSIONS

LHAS is a rare but increasingly recognized anomaly of the heart. Contemporary diagnostic methods allow to diagnose and make the right therapeutic decisions. The utility of TEE and analysis of X-ray images, in this case, allowed the surgeon to recognize LHAS, and because of its histologically benign nature and asymptomatic course, to leave this change intact. Surgical treatment should be limited only to cases of patients with life-threatening cardiovascular complications.

Fatty Images of the Heart: Spectrum of Normal and Pathological Findings by Computed Tomography and Cardiac Magnetic Resonance Imaging

Ectopic cardiac fatty images are not rarely detected incidentally by computed tomography and cardiac magnetic resonance, or by exams focused on the heart as in general thoracic imaging evaluations. A correct interpretation of these findings is essential in order to recognize their normal or pathological meaning, focusing on the eventually associated clinical implications. The development of techniques such as computed tomography and cardiac magnetic resonance allowed a detailed detection and evaluation of adipose tissue within the heart. This pictorial review illustrates the most common characteristics of cardiac fatty images by computed tomography and cardiac magnetic resonance, in a spectrum of normal and pathological conditions ranging from physiological adipose images to diseases presenting with cardiac fatty foci. Physiologic intramyocardial adipose tissue may normally be present in healthy adults, being not related to cardiac affections and without any clinical consequence. However cardiac fatty images may also be the expression of various diseases, comprehending arrhythmogenic right ventricular dysplasia, postmyocardial infarction lipomatous metaplasia, dilated cardiomyopathy, and lipomatous hypertrophy of the interatrial septum. Fatty neoplasms of the heart as lipoma and liposarcoma are also described.

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.

Focal FDG Activity in the Region of Right Atrium: Coregistered CT Identifies Three Benign Etiologies

We present the whole body FDG PET-CT images on 3 different patients with benign focal activity in the region of the right atrium. Co-registered CT correctly identified the cause of focal FDG activity as: right atrial appendage, lipomatous hypertrophy of the interatrial septum, and catheter-related activity. Although all these have been reported separately in the literature, we are presenting them together to emphasize the importance of recognizing the benign causes of FDG uptake in the region of right atrium and the role of co-registered CT in improving the accuracy and specificity of the FDG PET.

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.

Fatty foci within the heart diagnosed with ECG-gated multi-slice computed tomography: frequency and morphology

BACKGROUND

The purpose of our study was to analyze the frequency of focal fatty replacement (FR) of the heart, as well as the distribution and detailed morphology of FR in a large group of patients referred to multi-slice computed tomography with ECG-gating examinations (ECG-MSCT) for various clinical reasons.

MATERIAL AND METHODS

The ECG-MSCT examinations of 1830 consecutive patients were analyzed. The examinations were performed using 8-row (1015 patients) and 64-row (815 patients) MSCT, in pre- and post-contrast scanning. We analyzed the morphology of FR, the dimensions and densities of changes, as well as the morphology and localization of FR with regard to clinical diagnosis.

RESULTS

204 subjects (11.1%) had FR within the heart (113 men; 91 women; mean age 57.8 years); 66% of fatty foci were seen only in the native scanning. The distribution of the fat was: right ventricle (RV) 31.9%, left ventricle (LV) 21.5%, biventricular 39.7%, interventricular or atrial septum 5.9%, and atria 1%. In the RV, fat was localized mainly in the papillary muscles, while in the LV fat was mainly subendocardial (p<0.001). The morphology of the fat was: linear 61.6%, oval 14.8%, punctuate 10.6%, irregular 10.2%, and bilobular 2.8%. Fat was primarily located subendocardially in the LV in patients after myocardial infarction. In patients with suspected coronary artery disease, it was mainly observed subpericardially in the RV and in papillary muscles (p<0.001).

CONCLUSIONS

The incidental frequency of FR within the heart in patients diagnosed with the ECG-MSCT examinations is about 11%. Pre-contrast scanning is the most valuable for FR assessment.

Massive lipomatous hypertrophy of the right atria

A case of a 70-year-old female with a history of hypertension, atrial fibrillation, pacer implantation for symptomatic bradycardia, and a prior cerebrovascular accident, and had developed persistent methicillin-sensitive Staphylococcus aureus bacteremia is reported here. As part of her evaluation, a transesophageal echocardiogram was performed, and even though no vegetations were seen on either pacer wires or cardiac valves, a massive homogeneous thickening of the superior portion of the interatrial septum extending to the posterior and roof portions of the right atrial wall as well as to the superior vena cava causing proximal compression of this vessel was noted. Computed tomographic examination of the chest helped to determine that this mass density was not a tumor but in fact intrapericardial fat. Imaging findings and existing literature on this topic are reviewed.

CT features of myocardial fat and correlation with clinical background in patients without cardiac disease

OBJECTIVE

To evaluate the frequency and common locations of myocardial fat and its associated factors using coronary CT angiography (CCTA) in patients without cardiac disease.

METHODS

Using CCTA findings for 298 consecutive patients without cardiac disease, we categorized the myocardium into nine locations, scored fat in those locations, and correlated the fat score with the thickness of the right ventricular (RV) free wall and factors including gender, age, and body mass index (BMI) as well as history of diabetes mellitus, hypertension (HT), and dyslipidemia.

RESULTS

We observed myocardial fat in 68.5 % of patients, most commonly in the RV outflow tract (RVOT, 64.1 %), followed by the base (42.3 %) and middle (28.9 %) of the RV free wall, RV trabeculations (22.5 %), and the left ventricular apex (11.4 %). The RV free wall thickened significantly with increasing fat score. Dependent variables for myocardial fat were female gender (P < 0.0001), age ≥65 years (P = 0.0043), BMI ≥25 (P = 0.0050), and HT (P = 0.0139).

CONCLUSION

Myocardial fat is a common finding on CCTA in patients without cardiac disease, is often observed in the RVOT, and is more frequent in female patients, those older than 65 years, those with BMI ≥25, and those with HT.

Lipomatous hypertrophy of the interatrial septum in ECG-gated multislice computed tomography of the heart

BACKGROUND

Lipomatous hypertrophy of the interatrial septum (LHIS) is a benign disorder characterized by fat accumulation in the interatrial septum (IAS). The purpose of the study was to analyze the incidental detection of LHIS in patients with various clinical conditions, referred to ECG-gated multislice computed tomography (ECG-MSCT) examinations of the heart.

MATERIAL/METHODS

The ECG-MSCT examinations of 5786 patients (2839 women; 2947 men), were analyzed. The examinations were performed using 8-row (1015 patients) and 64-row (4771 patients) MSCT, in pre- and postcontrast scanning. We analyzed the shape of the IAS, density and maximal thickness of IAS, the thickness of the epicardial adipose tissue, and the degree of contact of IAS with the ascending aorta and superior vena cava. We also determined body mass index (BMI) in patients with LHIS.

RESULTS

LHIS was detected in 56 (0.96%) patients, with an average age of 61.5±9.8 years. The mean BMI in the analyzed group was 30.1±4.86. During the end-diastolic phase the thickness of IAS was significantly higher (p<0.0001), and on average equaled 18.3 mm. The mean optical density of the IAS was conspicuously higher (p<0.0001) in post-contrast phase than in pre-contrast phase. The thickness of the epicardial adipose tissue in the region of the left atrioventricular groove was on average 15 mm. In all cases the dumbbell shape of IAS was observed.

CONCLUSIONS

The incidental frequency of LHIS occurrence in patients diagnosed with the ECG-MSCT examinations is about 1%. In most subjects it is linked with a higher BMI and increased thickness of the epicardial adipose tissue.

Imaging findings of lipomatosis: a comprehensive review

Lipomatosis is a benign and non-encapsulated mature form of fat tissue proliferation, which can be isolated or multiple, symmetrical or infiltrative, and may be associated with several syndromes. Lipomatosis has been reported to involve almost every part and organ in the body. In this review, we present imaging findings at common locations of lipomatosis and summarize lipomatosis-related syndromes.

Cardiac masses, part 2: key imaging features for diagnosis and surgical planning

OBJECTIVE

The objectives of this article are to discuss key radiologic features that differentiate primary and secondary cardiac masses. Clinical scenarios are included to highlight stepwise radiologic workup of tumors of the pericardium, epicardium, myocardium, valves, and chambers. The involvement of key cardiac anatomic structures will also be emphasized to determine resectability and guide surgical planning.

CONCLUSION

Multimodality imaging plays a pivotal role in diagnosis and surgical planning of cardiac masses. Clinical features, such as patient age, location, and imaging characteristics of the mass will determine the likely differential diagnosis. In addition to radiologic evaluation of the mass itself, involvement of valvular apparatus, extent of myocardial involvement, or presence of associated coronary artery involvement is necessary to determine resectability and surgical technique.

Myocardial fat at cardiac imaging: how can we differentiate pathologic from physiologic fatty infiltration?

Myocardial fat is often seen at cardiac computed tomography (CT) and magnetic resonance (MR) imaging of healthy adults and patients with myocardial diseases. Physiologic myocardial fat develops with aging and is commonly seen at CT in the anterolateral right ventricular (RV) free wall and RV outflow tract with normal or thickened RV myocardium and a normal-sized RV in elderly patients. Pathologic conditions with myocardial fat include healed myocardial infarction (MI); arrhythmogenic RV cardiomyopathy or dysplasia (ARVC); and others, such as cardiac lipoma, lipomatous hypertrophy of the interatrial septum, tuberous sclerosis complex, dilated cardiomyopathy, and cardiomyopathy with muscular dystrophy. In patients with healed MI, CT and MR imaging show fat in left ventricular myocardium that is of normal thickness or thin and follows the distribution of the coronary artery; CT often depicts fat in mostly subendocardial regions. In patients with ARVC, characteristic CT and MR imaging findings include a thin RV outflow tract and free wall caused by subepicardial fatty infiltration; fat in the RV moderator band, trabeculae, and ventricular septum; and RV enlargement and wall motion abnormality. Recognition of patient age, characteristic locations of myocardial fat, myocardial thickness, and ventricular size helps in differentiating physiologic and pathologic myocardial fat at cardiac imaging; findings of wall motion abnormality and late gadolinium enhancement at MR imaging help narrow the diagnosis.

Lipomatous hypertrophy of the interatrial septum in a patient with carcinoma: a case report of the importance of multi-modality imaging

INTRODUCTION

  Lipomatous hypertrophy of the interatrial cardiac septum is a benign disorder. In rare cases, the disorder can cause obstruction of atrial inflow, causing symptoms of heart failure, or cardiac arrhythmias resulting from the involvement of the atrial wall and atrioventricular conduction pathways.

CASE PRESENTATION

  We present a case of a Caucasian 66-year-old man with urothelial carcinoma where transthoracic echocardiolography showed a mass in the basal part of the interatrial septum. After injection of echo contrast, it was suggested that the structure was vascularized, thus implying tumour. Transoesophageal echocardiography and cardiac magnetic resonance imaging gave the correct diagnosis of lipomatous hypertrophy. It was then discovered that the patient had been referred to a computed tomography (CT) earlier, but no mention of the mass was found in the report from the examination. Re-evaluation of the images showed a clearly visible mass indicative of fatty tissue.

CONCLUSION

  This case report highlights the importance of multi-modality imaging when the findings are not concordant. Moreover, this case report also highlights the importance of careful examination of the heart on routine CT scans, something that is often overlooked by the radiologists. In this case, the CT scan clearly indicated the diagnosis of lipomatous hypertrophy of the interatrial septum and thus could have prevented the subsequent imaging cascade.

Cardiac CT of non-shunt pathology of the interatrial septum

The development and anatomy of the interatrial septum is complex. With the increasing use of cardiac CT and its precise delineation of the anatomy, it is important for the cardiac imager to become familiar with the normal anatomic structures that compose the interatrial septum and their variants. Furthermore, it is important to recognize pathologic processes occurring in this region other than atrial septal defects and potential imaging pitfalls. This pictorial essay provides a detailed review of these topics with emphasis in CT appearance and related technical aspects.

The role of computed tomography and magnetic resonance imaging in ablation procedures for treatment of atrial fibrillation

Cardiac ablation procedures have become the standard of therapy for various arrhythmias including atrial fibrillation. Understanding the morphological characteristics of the left atrium (LA) and pulmonary veins (PV) in detail and identification of its anatomic variants is crucial to perform a successful ablation procedure and minimize complications. The current techniques for radiofrequency ablation of atrial fibrillation include targeting the PVs or the tissue in the antrum of the LA. Localization of the anatomic structures within the LA is performed by using fluoroscopy, electroanatomic mapping, and intracardiac echocardiography. Multidimentional computed tomography and magnetic resonance angiography are invaluable techniques for better visualization of the anatomic landmarks that are essential for cardiac ablation procedures as well as prompt diagnosis and, in selected cases, prevention of procedure-related complications. Some of the complications of ablation procedures may include cardiac tamponade, PV stenosis, as well as esophageal and phrenic nerve injuries.

Lipomatous hypertrophy of the interatrial septum: a pathological and clinical approach

Lipomatous hypertrophy of the interatrial septum (LHIS) is a rare benign disorder that is characterized by accumulation and deposition of fat in the interatrial septum. Its etiology is still unknown, despite the theories that have been suggested. It usually occurs in older, obese people with a higher incidence in women. In most cases, it remains asymptomatic, thus its diagnosis is rarely made during a person's lifetime and it is made incidentally or during autopsy. LHIS can cause atrial arrhythmias, obstructive flow symptoms and sometimes death. The diagnosis of LHIS can be made by the use of imaging techniques, with the best results given by multislice-CT (MSCT) scanning. Surgical intervention is usually avoided and the best management is early diagnosis, reassurance and inactivity. However, in cases of severe superior vena cava obstruction or intractable rhythm disturbance, surgical excision is performed together with reconstruction of the interatrial septum.

Lipomatous hypertrophy of the interatrial septum: an overview

Lipomatous hypertrophy of the interatrial septum is a rare, but increasingly recognized, anomalous developmental or neoplastic lesion of the heart. This entity was first described in 1964 at autopsy and is identified before death based on its distinctive characteristics on echocardiography, computed tomography, and magnetic resonance imaging. Although it is often asymptomatic, the mass has been associated with supraventricular arrhythmias and sudden death. In rare patients who experience intractable symptoms, surgical excision of the lesion may provide relief. Therefore, lipomatous hypertrophy of the interatrial septum is of interest to the pathologist when a cardiac mass is received for evaluation or at autopsy when a patient has experienced sudden death from an unknown cause.

When, Why, and How to Examine the Heart During Thoracic CT: Part 1, Basic Principles

OBJECTIVE

MDCT systems with fast scanning capabilities can acquire images of the thorax with reduced cardiac motion artifacts, enabling improved evaluation of the heart and surrounding structures in the course of routine thoracic CT. This article describes the principles of including an evaluation of the heart in the course of a chest CT examination in terms of both examination technique and image interpretation. In addition, both the normal appearances and some of the most common abnormal appearances of the cardiac structures will be described.

CONCLUSION

Details concerning the cardiac structures can inform interpretation of thoracic CT studies and can influence the patient's clinical management. Both unenhanced and contrast-enhanced scans can detect significant cardiac disorders that may otherwise go undetected. In certain situations, a CT examination of the entire chest, complemented by cardiac gating, can provide a more dedicated analysis of the heart and coronary arteries, providing both morphologic and functional information.

Lipomatous Hypertrophy of the Interatrial Septum

OBJECTIVE

To determine the prevalence of lipomatous hypertrophy of the interatrial septum (LHIS) on CT and its metabolic pattern on 18F fluorodeoxyglucose (FDG)-positron emission tomography (PET).

METHOD AND MATERIALS

Eight hundred two CT PET scans were reviewed. Patients were included if the interatrial septum was > or = 1 cm and excluded if there was evidence of malignancy in the adjacent lung, hilum, or mediastinum. CT scans were fused with PET scans, and the mean standardized uptake value (SUV) was calculated over the LHIS, chest wall (CW) fat, and mediastinal blood pool. CT scans were reviewed for presence of excessive fat in the mediastinum, pericardial, peridiaphragmatic, peritoneal, and retroperitoneal regions and for the presence of emphysema. Medical records were reviewed for body mass index (BMI) and history of arrhythmia.

RESULTS

Twenty-three of 802 patients (2.8%) had LHIS on CT (9 women and 14 men); average age was 75.6 years (range, 58 to 95 years). Average BMI of 17 patients (+/- SD) was 31 +/- 4.9 (range, 22.1 to 39.9). Mean CT values were as follows: thickening of LHIS, 1.47 +/- 0.35 cm (range, 1.07 to 2.25 cm); LHIS, - 79.6 + 24.5 Hounsfield unit (HU) [range, - 11 to - 121 HU]. LHIS was dumbbell shaped in 18 patients. Mean SUVs were as follows: LHIS, 1.84 +/- 0.10 (range, 0.48 to 3.48); CW fat, 0.36 + 0.37 (range, 0.04 to 1.98); blood pool, 1.74 + 0.51 (range, 0.25 to 2.71). The SUV of LHIS was greater than the SUV of CW wall fat in all patients (p < 0.0001). There was significant correlation between SUV and thickness of the LHIS on CT (p < 0.0001, r = 0.883). Those with dumbbell-shaped LHIS (p < 0.003) and presence of emphysema (p < 0.0377) had greater LHIS mean SUV.

CONCLUSION

The SUV of LHIS was greater than the SUV of CW fat in all patients. LHIS with greater thickness or dumbbell shape had greater FDG uptake. These findings on CT and PET are important to recognize in order to avoid false-positive FDG-PET interpretations.

Lipomatous Hypertrophy of the Interatrial Septum: Increased Uptake on FDG PET

OBJECTIVE

The objective of our study was to evaluate FDG uptake in patients with cardiac lipomatous hypertrophy of the interatrial septum (LHIS).

CONCLUSION

Increased FDG uptake occurs in LHIS, a benign fatty infiltration of the interatrial septum. Increased uptake in the right heart on FDG PET warrants correlation with additional imaging to assess for LHIS and avoid false interpretation of malignancy.

Lipomatous hypertrophy of the interatrial septum: a prospective study of incidence, imaging findings, and clinical symptoms

BACKGROUND

Lipomatous hypertrophy of the interatrial septum (LHIS) is a benign disorder characterized by fat accumulation in the interatrial septum. It typically occurs in elderly, obese patients and may cause arrhythmia.

OBJECTIVES

The purpose of this study was to determine the imaging features of this cardiac pathology using multislice CT (MSCT), and its relationship with clinical findings.

MATERIALS AND METHODS

A total of 1,292 consecutive patients who underwent MSCT of the thorax from September 2001 to August 2002 were prospectively studied. Beside the analysis of patient records, the amount of fat in the interatrial septum, and its size and shape were determined.

RESULTS

Among the 1,292 patients investigated, we found 28 (2.2%) with LHIS. The mean age of affected patients was 72.2 years. MSCT studies revealed a mass of fat attenuation with sharp margins and sparing of the fossa ovalis, resulting in a dumbbell shape in all patients. The median thickness of the interatrial septum was 32 mm (range, 20 to 62 mm), and the median craniocaudal extend was 62 mm (range, 51 to 89 mm). Twenty-one patients (75.0%) showed increased epicardial fat, 18 patients (64.3%) had significant pulmonary emphysema, and 13 of 21 patients (61.9%) showed ECG abnormalities. Three patients underwent functional cardiac MRI studies. In one patient, hemodynamic obstruction by LHIS was shown.

CONCLUSIONS

MSCT scanning is a useful method to diagnose LHIS, a cardiac condition that in our series reached a 2.2% incidence. The lesion shows characteristic features, thus differentiating it from other cardiac tumors. Advanced age, obesity, pulmonary emphysema, and atrial arrhythmias are common additional findings in patients with LHIS.

Fat-containing lesions of the chest

Although most lesions that occur in the chest have a nonspecific soft-tissue appearance, fat-containing lesions are occasionally encountered at cross-sectional computed tomography (CT) or magnetic resonance imaging. The various fat-containing lesions of the chest include parenchymal and endobronchial lesions such as hamartoma, lipoid pneumonia, and lipoma. Endobronchial hamartoma usually appears at CT as a lesion with a smooth edge, focal collections of fat, or fat collections that alternate with foci of calcification. Mediastinal fat-containing lesions include germ cell neoplasms, thymolipomas, lipomas, and liposarcomas. The most frequent CT manifestation of the germ cell neoplasm teratoma is a heterogeneous mass with soft-tissue, fluid, fat, and calcium attenuation. Cardiac lesions with fat content include lipomatous hypertrophy of the interatrial septum and arrhythmogenic right ventricular dysplasia. Diagnosis of the former is made with CT when a smooth, nonenhancing, well-marginated fat-containing lesion is identified in the interatrial septum. Finally, fat may herniate into the chest at several characteristic locations. When such a lesion is identified, the time required for differential diagnosis is significantly reduced, often allowing a definitive radiologic diagnosis. Sagittal and coronal reformatted images can add valuable information by showing diaphragmatic defects and hernia contents.

Can cardiac magnetic resonance imaging reliably differentiate between benign and neoplastic fat?

Magnetic resonance imaging is currently frequently used to differentiate lipomatous hypertrophy of the interatrial septum from other cardiac lesions involving abnormal fatty tissue including lipomatous neoplasms. This report discusses potential problems with this approach by emphasizing the variable appearance of lipomatous hypertrophy of the interatrial septum on magnetic resonance imaging.

Fat attenuation lesions of the mediastinum

The identification of fat within a focal or diffuse mediastinal lesion significantly narrows the differential diagnosis. In many cases, a specific diagnosis can be suggested on the basis of CT findings. In this article, we illustrate and review the characteristic CT features of common and uncommon fat attenuation lesions of the mediastinum, including focal masses and diffuse abnormalities.

Molecular genetic diagnosis of the familial myxoma syndrome (Carney complex)

We describe an individual in whom molecular genetic testing provided a diagnosis of the Carney complex, an autosomal dominant syndrome comprising cutaneous and cardiac myxomas, spotty pigmentation of the skin, and endocrinopathy. Recently, we localized the Carney complex disease gene to chromosome region 17q2. Our patient was a member of a family segregating the Carney complex, but was not, himself, initially thought to be affected. Haplotype analysis based on genotyping studies with 17q2 microsatellites predicted that this individual was, in fact, affected by Carney complex and was at risk for development of myxomas. Further clinical evaluation and re-review of prior pathologic studies, then, confirmed the DNA-based diagnosis. This report highlights the difficulty in establishing a diagnosis of Carney complex based on clinical and pathologic findings alone, and we suggest that molecular genetic analyses provide an important diagnostic method for this familial myxoma syndrome.

Characterization of an Unusual Right Atrial Mass by Echocardiography, Magnetic Resonance Imaging, Computed Tomography, and Angiography

A right atrial mass was discovered by echocardiography in a 53-year-old man. A work-up consisting of magnetic resonance imaging and computed tomography studies established the diagnosis of atrial lipoma. The echocardiographic features are compared with the radiological findings, and the characteristics permitting differentiation of lipoma from other causes of cardiac masses are discussed. In this case, echocardiography not only permitted the initial identification of the mass but also proved to be useful in follow-up of its evolution over time, thereby influencing the therapeutic management.

Lipomatous hypertrophy of the atrial septum: diagnosis with fat suppressed MR imaging

We present a case of a 50-year-old female evaluated for a 1-year history of numbness of the first and second toe of the right foot. Echocardiography performed in order to exclude cardiovascular compromise revealed a granular mass originating from the posterior part of the interatrial septum. On subsequent magnetic resonance imaging (MRI) with fat suppression sequences, the final diagnosis of lipomatous hypertrophy of the interatrial septum, a benign and underrecognized condition characterized by septal accumulation of fatty tissue, was made. Although no previous reports have focused on this, tailored cardiac MR with fat suppression sequences proved to be an excellent noninvasive method in assessing an accurate diagnosis and in differentiating lipomatous hypertrophy of the atrial septum from other cardiac neoplasms.