Myocardial Fat at Cardiac Imaging: How Can We Differentiate Pathologic from Physiologic Fatty Infiltration?

Abstract

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.

Fatty foci within the heart and the accompanying changes in the coronary arteries diagnosed in electrocardiogram-gated multislice computed tomography of the heart

“…The similar dependence was found in our study-in the group of patients after MI most often fatty foci were localised subendocardially in the LV. A similar dependence was described by Kimura et al [10]. In patients without changes in the coronary arteries, significantly more often fatty deposits were localised within the RV.…”

“…Physiologic fat is located in the anterolateral RV free wall, RV outflow tract, and sometimes in RV trabeculae and the apex of the heart. In these cases the myocardial wall is either normal or thick [10]. Kirsch et al [11] showed that there is no correlation between the presence of the fat in the RV and the body mass index of patients.…”

“…The most commonly reported diseases, where there is fat infiltration of the myocardium, are arrhythmogenic right ventricular dysplasia (ARVD), tuberous sclerosis and scar tissue following myocardial infarction (MI) [1-3, 8, 13, 15]. However, fatty infiltration of the right ventricle can also be present in healthy people [9,10].…”

Cardiac MR Findings and Potential Diagnostic Pitfalls in Patients Evaluated for Arrhythmogenic Right Ventricular Cardiomyopathy

“…The fatty pattern is associated with preserved myocardial thickness, whereas in the fibrofatty pattern, there is marked thinning of the myocardium (7,17,20,21) (Fig 2). Intramyocardial fat is more commonly seen in the basal and mid free wall, the RVOT, and the lateral apex and occasionally is seen in the inferoseptal portion of the RV, the RV trabeculae, and the moderator band (12,15,22,23). Fibrosis is usually seen in the same place as fat and may result in delayed enhancement after contrast material administration.…”

“…The presence of myocardial fatty or fibrofatty infiltration is not included in either the revised or the original task force criteria because of (a) artifactual fat resulting from limited imaging techniques (22) and (b) the presence of fatty infiltration in physiologic (20)(21)(22)(23)(24) and other pathologic states, such as healed myocardial infarction (18,(24)(25)(26)(27)(28)(29)(30) (Fig 3), cardiac lipoma (31,32), lipomatous hypertrophy of the interatrial septum (33), tuberous sclerosis complex (34), and dilated cardiomyopathy. Isolated and marked lipomatous infiltration of the RV appears to be a separate condition from ARVC (35).…”