Relationship between indexed epicardial fat volume and coronary plaque volume assessed by cardiac multidetector CT

Abstract

We explored whether baseline indexed epicardial fat volume (EFVi) and serial changes in EFVi were associated with increase in coronary plaque volume as assessed by multidetector computed tomography.We retrospectively reviewed 87 patients with coronary artery plaque, identified during either baseline or follow-up cardiac computed tomography (CT) examinations. Each plaque volume was measured in volumetric units using a semiautomatic software tool. EFVi was quantified by calculating the total volume of epicardial tissue of CT density -190 to -30 HU, indexed to the body surface area. Clinical cardiovascular risk factors were extracted by medical record review at the time of the cardiac CT examinations. The relationship between EFVi and coronary plaque volume was explored by regression analysis.Although the EFVi did not change significantly from baseline to the time of the follow-up CT (65.7 ± 21.8 vs 66.0 ± 21.8 cm/m, P = 0.620), the plaque volumes were increased significantly on the follow-up CT scans. The annual change in EFVi was not accompanied by a parallel change in coronary plaque volume (P = 0.096-0.500). On univariate analysis, smoking, hypercholesterolemia, 10-year coronary heart disease risk, obesity, and baseline EFVi predicted rapid increases in lipid-rich and fibrous plaque volumes. On multivariate analysis, baseline EFVi (odds ratio = 1.029, P = 0.016) was an independent predictor of a rapid increase in lipid-rich plaque volume.EFVi was shown to be an independent predictor of a rapid increase in lipid-rich plaque volume. However, changes in EFVi were not associated with parallel changes in coronary plaque volume.

Figure 1

A 54-year-old male patient with low pretest probability underwent calcium score CT (A) and coronary CT angiography (B). (A) The semiautomated software was used to identify an area of at least 0.5 mm² with a density ≥130 HU as calcified plaque, and then to measure the coronary calcium score and volume. The calcified plaque volume of the patient was 13.61 mm³. (B) Noncalcified plaque volume was measured on coronary CT angiography. Noncalcified plaque was color-coded according to CT value (HU) and classified into low attenuation plaque (0–49 HU; designated as lipid-rich plaque) and intermediate attenuation plaque (50–129 HU; designated as fibrous plaque). Lipid-rich and fibrous plaque volumes of the patient were 13.13 and 31.59 mm³, respectively. CT = computed tomography.

Figure 2

A 50-year-old male patient with low pretest probability. Epicardial fat was defined as the adipose tissue between the surface of the myocardium and the visceral layer of the pericardium. (A) The border of the epicardium (yellow line) was traced semiautomatically. (B) EFV was quantified by calculating the total volume of the tissue (green color) showing a CT density of −190 to −30 HU within the epicardium. (C) The computer software constructed a 3-dimensional image of the epicardial fat automatically, with the data reported in cubic centimeters. The EFV of the patient was 119 cm³, and that indexed to body surface area (EFVi; 1.91 m²) was 62.3 m³/m². CT = computed tomography, EFV = epicardial fat volume, EFVi = indexed epicardial fat volume.

Figure 3

A 43-year-old male patient with an intermediate pretest probability underwent baseline cardiac CT (A–D). The baseline EFV was 54.0 cm³ (A, B), calcified plaque volume was 380.1 mm² (C), and noncalcified plaque volume (D) was 289.4 mm² (lipid-rich plaque volume, 103.9 mm²; fibrous plaque volume, 185.5 mm²). After 31 months, follow-up CT images (E–H) showed no rapid annual change in EFV (Δ 1.9 cm³/y) or EFVi (Δ 1.0 cm³/m²/y). Although the calcified plaque volume (Δ 62.9 mm³/y) increased rapidly, the noncalcified plaque volume (lipid-rich plaque volume, Δ 9.4 mm³/y; fibrous plaque volume, Δ 1.2 mm³/y) did not. CT = computed tomography, EFV = epicardial fat volume, EFVi = indexed epicardial fat volume.