Epicardial Fat Density Measurement

EF is the fat deposit located between the visceral pericardium and the myocardium. EF density decreases with fat gain and increases with fat loss.^{[16 (link),21 (link)]} In addition, EF density increases with inflammatory cell infiltration and metabolic dysfunction.^{[14 (link),16 (link),22 (link)]} Therefore, the higher the density, the more metabolically active the fat deposition might be.^{[13 (link),23 (link)]}EF density and volume were both assessed using non-contrast CT images and a semi-automated software (Aquarius Intuition version 4.4.11; TeraRecon Headquarters, Forster City, CA). The pericardium was manually traced on axial slices from the pulmonary artery bifurcation to the apex of the heart. A CT density between −190 and −30 HU was used to select the EF and exclude any other tissue. Mean EF density and volume were calculated using the software based on the adipose tissue area, the number of slices, slice thickness, and intersection gaps, and reported as a continuous value, expressed in HU and cm³.
Two observers both blinded to HIV status and clinical data measured EF volume and density using the semi-automated software. Inter-observer and intra-observer agreement for EF volume and density measurement were highly reproducible (intraclass correlation coefficient for inter-observer agreement 0.75 for EF volume and 0.99 for density; Intra-observer agreement 0.97 for EF volume and 0.97 for density).^{[24 (link)]}