Epicardial fat density obtained with computed tomography imaging - more important than volume?

Epicardial adipose tissue (EAT) is a unique fat depot located between the myocardium and the visceral layer of pericardium. It can be further subdivided into pericoronary (PCAT), periatrial (PAAT) and periventricular adipose tissue (PVentAT), each of them exhibiting specific characteristics and association with the underlying tissue. Since no physical barrier separates EAT from the myocardium, this fat tissue can easily interact with the underlying cardiac structure. EAT can be visualized using various imaging modalities. Computed tomography provides not only information on EAT volume, but also on its density. Indeed, EAT density reflected by the recently developed fat attenuation index (FAI) is emerging as a useful index of PCAT inflammation, PAAT inflammation and fibrosis, while the relevance of density of PVentAT is much less known. The emerging data indicates that FAI can be an important diagnostic and prognostic tool in both coronary artery disease and atrial fibrillation. Future studies will demonstrate if it also could be used as a marker of efficacy of therapies and whether FAI PVentAT could indicate ventricular pathologies, such as heart failure. The aim of the review is to present computed tomography derived FAI as an important tool both to study and better understand the epicardial fat and as a potential predictive marker in cardiovascular disorders.