Epicardial fat: definition, measurements and systematic review of main outcomes

Abstract

Epicardial fat (EF) is a visceral fat deposit, located between the heart and the pericardium, which shares many of the pathophysiological properties of other visceral fat deposits, It also potentially causes local inflammation and likely has direct effects on coronary atherosclerosis. Echocardiography, computed tomography and magnetic resonance imaging have been used to evaluate EF, but variations between methodologies limit the comparability between these modalities. We performed a systematic review of the literature finding associations of EF with metabolic syndrome and coronary artery disease. The summarization of these associations is limited by the heterogeneity of the methods used and the populations studied, where most of the subjects were at high cardiovascular disease risk. EF is also associated with other known factors, such as obesity, diabetes mellitus, age and hypertension, which makes the interpretation of its role as an independent risk marker intricate. Based on these data, we conclude that EF is a visceral fat deposit with potential implications in coronary artery disease. We describe the reference values of EF for the different imaging modalities, even though these have not yet been validated for clinical use. It is still necessary to better define normal reference values and the risk associated with EF to further evaluate its role in cardiovascular and metabolic risk assessment in relation to other criteria currently used.

Figure 1

Epicardial fat measurement by echocardiography in the parasternal longitudinal and transverse parasternal views. Epicardial fat (indicated by arrows) with increased thickness (1A and 1B) and minimum epicardial fat (1C and 1D).

Figure 2

Characterization of the pericardium (white arrow), epicardial fat (asterisk) and paracardial fat (star) by magnetic resonance. Left frame shows long-axis four‑chamber and the right, basal short-axis view at end-diastole (SSFP cine sequence - bright blood).

Figure 3

Measurement of epicardial fat volume by computed tomography. In the figure, acquired slices are used for evaluation of coronary calcium score (3-mm thickness). The area of interest is defined by the manual delineation of the pericardium and the volume calculated in a semi-automatic way by specific software.