Teaching Case

A 65-year-old asymptomatic woman with a history of hypertension was found to have a left ventricular mass during a routine transthoracic echocardiogram. To further characterise the mass, a cardiac MRI was performed.

Steady-state free precession (SSFP) Cine MR-images on four chambers and short-axis view showed a solitary, well-defined, small round mobile mass in the left ventricle attached by a stalk to the endocardial surface of the mid-anterior septum (Fig. 1a, b). No other masses were present. The mass was slightly hyperintense showing a dark rim with the adjacent blood on short-axis SSFP Cine MRI (Fig. 1) and hyperintense on T1-weighted black-blood MR images (Fig. 2). On fat-suppressed T1-weighted black-blood MR images, the mass appeared hypointense (arrowhead) (Fig. 3). Left ventricular function and regional wall motion were normal.

Primary tumours of the heart are rare. Approximately 75% of such tumours are benign and 25% are malignant. Most benign heart tumours are myxomas, and the majority of the rest are lipomas, papillary fibroelastomas, and rhabdomyomas [1].
Cardiac lipomas account for 8% of all cardiac tumours at any age and in men and women with equal frequency. They are well-encapsulated tumours composed of mature fat cells [2] and should be differentiated from most common hypertrophic lipomatosis of the interatrial septum, in which there is deposition of non-encapsulated mature and fetal adipose tissue. Fifty percent of cardiac lipomas are intracavitary and subendocardial in origin, 25% are intramyocardial, and 25% are epicardial and extracavitary [3]. The most common location is in the right atrium with a wide peduncle originating either from the septal wall or atrial roof [1, 2]. They have also been described in the pericardium, left atrium, on the heart valves, in the pulmonary veins, in the right coronary artery as well as in the right and left ventricles [4].
As in our case, almost all patients are asymptomatic, and the tumour is found incidentally. Subendocardial lipomas are typically small and sessile and can cause obstructive symptoms. Intramyocardial lipomas have been associated with a variety of arrhythmias including atrial fibrillation, ventricular tachycardia, and atrioventricular block. Surgical resection is recommended in symptomatic patients [1].
The echocardiographic findings of intracavitary lipomas are nonspecific, they usually are homogeneous and hyperechoic masses. Although echocardiography is the technique of choice for the routine cardiac evaluation and enables the detection of cardiac mass, a cardiac MRI is necessary to characterise the mass with regard to localisation, extent, tissue composition, point of attachment and furthermore its functional impact [1, 2].
Lipomas have specific MR imaging characteristics, with homogeneous high signal intensity on T1-weighted images and slightly less high signal intensity on T2-weighted images. The most characteristic finding is the signal dropout identified on the fat-saturation sequences confirming its fat containing [1]. SSFP-Cine MR images are particularly useful for evaluating tumours that are mobile, such as pedunculated lipomas. Like soft-tissue lipomas, cardiac lipomas do not enhance with the administration of contrast material [2].
Our report highlights the importance of a comprehensive cardiac MRI approach that can provide the clinician not only with an accurate description of the imaging findings but also the aetiological diagnosis.