Lipomatous Hypertrophy of the Interventricular Septum
Echocardiography, Cardiac Magnetic Resonance, and Multidetector Computerized Tomography Imaging
A healthy 17-year-old boy with neither a personal nor familial cardiac history saw his family physician for a routine examination before participating in an athletic competition. His systolic blood pressure was normal. On physical examination, a heart murmur was detected and the boy was sent to a cardiologist for echocardiography, which showed hyperechogenic and increased interventricular septal thickness resembling an asymmetric hypertrophic cardiomyopathy (online-only Data Supplement Movie I). However, no mitral leak, no obstruction of the left ventricular outflow tract, and no systolic anterior motion were observed, and left ventricular function was normal, even during exercise testing. The ECG showed no increased PR interval and no T-wave anomaly or ventricular arrhythmia (Figure 1). Because of the unusual hyperechogenicity of the interventricular septum, indicating a possible infiltrative cardiomyopathy such as Fabry disease (glycosphingolipid storage disease), the patient underwent further investigations with cardiac magnetic resonance imaging (online-only Data Supplement Movie II and Figure 2), multidetector computerized tomography (MDCT) (Figure 3), and a blood sample analysis of α-galactosidase A activity.
Magnetic resonance imaging showed a large fatty area infiltrating the inferior interventricular septum, nonhomogeneous and hyperintense compared to the myocardial wall on steady-state free precession sequences. The borders were not sharply delineated, and the shape of the infiltrating mass was not rounded. This contractile anomaly was crossed by multiple kinetic myocardial fibers consistent with an infiltrative rather than organized mass (Figure 4). MDCT found negative fat values of −60 to −100 HU in several regions of interest, confirming the presence of fatty tissue (Figures 3 and 4⇓). Normal α-galactosidase A activity in leukocytes and plasma ruled out Fabry disease.
Cardiac lipomas are rare and are generally described as homogeneous, relatively rounded, well-encapsulated masses.1 Lipomatous hypertrophy differs from a lipoma by the absence of capsule,2 the location in the interatrial septum, and the presence of fetal fat.3 Even though we do not have any pathological material, all imaging characteristics in this case suggest that we are describing the first case of interventricular septal lipomatous hypertrophy. Because the patient was asymptomatic, he did not undergo an endomyocardial biopsy or surgery and was not given medication. Annual transthoracic echocardiography and clinical follow-up have been planned, and he was considered preventively unfit for high-level sports.
The online-only Data Supplement is available with this article at http://circ.ahajournals.org/cgi/content/full/118/4/e71/DC1.