Epicardial Fat Distribution Assessed with Cardiac CT in Arrhythmogenic Right Ventricular Dysplasia/Cardiomyopathy

Abstract

Purpose To compare epicardial fat in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) with that in healthy subjects. Materials and Methods In this retrospective study, cardiac CT scans in 44 patients with ARVD/C (mean age, 39 years ± 12; 23 men) were compared with those in 45 control group participants between January 2008 and July 2015. Volumes of intrathoracic adipose tissue, mediastinal adipose tissue (MAT), and total epicardial adipose tissue (EAT) were quantified. EAT was subdivided into three regions-right ventricular (RV) EAT, left ventricular (LV) EAT, and peri-atrial EAT (atrial EAT)-and normalized to MAT for all regions. Logistic regression and receiver operating characteristic analysis were performed to evaluate the association between epicardial fat with the diagnosis of ARVD/C. Results Total EAT volume was higher in patients with ARVD/C than in healthy control group participants (median, 98 mL vs 76 mL, respectively; P = .04). Regionally, LV and RV EAT volumes were higher in patients with ARVD/C than in control group participants, most notably when indexed to MAT (median LV EAT index: 0.49 vs 0.15, respectively; median RV EAT index: 0.91 vs 0.52; P ˂ .0005 for both). The optimal cutoff for diagnosis of ARVD/C was an LV EAT index of 0.24, with a sensitivity and specificity of 91% and 71%, respectively. Atrial EAT volume and total intrathoracic adipose tissue volume were not different between groups. RV diameter showed a positive correlation with total EAT index and LV EAT index (r = 0.21, P = .05 and r = 0.33, P = .002, respectively). Conclusion Higher amounts of right ventricular and left ventricular epicardial fat are found in hearts with arrhythmogenic right ventricular dysplasia/cardiomyopathy, particularly adjacent to the left ventricle, which correlates with disease severity and helps differentiate patients from healthy subjects. © RSNA, 2018 Online supplemental material is available for this article.

Figure 1:

Epicardial fat quantification with contrast-enhanced cardiac CT in 29-year-old woman with arrhythmogenic right ventricular dysplasia/cardiomyopathy. A, Axial image in midheart before performing analysis. B, Epicardial segmentation has been performed by tracing the pericardial contour. C, Threshold (−10 HU and lower limit of −190 HU) has been applied, highlighting all fat pixels in red. D, Example of left ventricular (LV) regional contouring to segment LV epicardial adipose tissue (EAT). E, Example of segmented LV EAT before fat thresholding. F, LV EAT after application of a fat threshold. The volume of fat (red pixels) is automatically calculated by the software. These steps were repeated for each epicardial fat region for each axial section through the heart.

Figure 2:

Contrast-enhanced cardiac CT images in, A, 26-year-old woman with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) with left ventricular (LV) epicardial fat infiltration (arrows) and, B, 28-year-old woman with ARVD/C without LV epicardial fat infiltration.

Figure 3:

Contrast-enhanced cardiac CT images in, A, 31-year-old healthy man with low epicardial adipose tissue (EAT) volume and, B, 39-year-old woman with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) and high EAT volume. In the healthy control group participant, a small amount of epicardial fat is seen around right ventricle (arrow) but not around left ventricle. In patient with ARVD/C, there is extensive fat around both the left and right ventricles (arrows).

Figure 4:

Graphs show that right ventricular (RV) diameter (in centimeters) in patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy is associated with epicardial but not mediastinal fat. A, Mediastinal adipose tissue (MAT), which is the fat in the mediastinum but outside of the pericardium, showed poor correlation to RV diameter. B, Epicardial adipose tissue (EAT) index, which is all the fat within the pericardium normalized to MAT, showed moderate correlation with RV diameter. C, D, At regional subanalysis of epicardial fat, RV and left ventricular (LV) epicardial adipose tissue indexed to MAT (RV index, LV index) showed a significant moderate correlation with RV diameter only for LV EAT index.

Figure 5:

Receiver operating curves for evaluating the ability of various epicardial fat parameters to enable the differentiation between patients with arrhythmogenic right ventricular dysplasia/cardiomyopathy (ARVD/C) and control group participants. Left ventricular (LV) epicardial adipose tissue index (EAT) has the greatest sensitivity and specificity for diagnosis of ARVD/C. AUC = area under the receiver operating characteristic curve, RV = right ventricle.