Epicardial Fat Tissue and Severity of Coronary Artery Disease in Diabetic vs Non Diabetic Patients

Epicardial fat tissue (EFT) is is most commonly defined as adipose tissue surrounding the heart, located between the myocardium and the visceral layer of pericardium Once considered only as a mere storage compartment, the adipose tissue is now recognized for its extensive metabolic and endocrine function, EFT is a storage fat that covers 80% of the heart's surface, representing 20% of the organ total weight, EFT is considered to be a part of visceral adipose tissue. This fat is a major source of biomolecules and compartmentalized production of cytokines and hormones, acting as a localized gland.

Moreover, EFT and the underlying myocardium share the same microcirculation, suggesting a close and strong interaction between these two structures, it regulates heart and blood vessel physiologically, via paracrine and vasocrine mechanisms. It has also been reported that EFT acts as important energy reservoir for cardiomyocytes, which depend on fatty acids oxidations as energy source especially during periods of high demand.

Although EFT is needed for heart muscle function, in recent decades it has been published that increased thickness greatly enhances the risk of developing CVD and metabolic syndrome, becoming a new pharmacological target for primary and secondary prevention strategies. Therefore, the measurement of epicardial fat deposition is important. In terms of modulation, the use of statins could function as a possible treatment to help decrease the volume of EFT beside stabilization of atherosclerotic plaques.

Detection and quantification of EFT require a variety of useful imaging techniques, including 2-dimensional (2D) echocardiography, non-contrast computed tomography (CT) and magnetic resonance imaging (MRI) . Since fat tissue generates a strong MRI signal, both thickness and volume of epicardial fat can be easily measured with this modality.

Clinical research found that it was related to coronary artery disease, where it was found to be independently and linearly associated with CAD and its severity, atrial fibrillation as well as myocardial dysfunction.

It is known that abnormally accumulated visceral fat is a risk factor for insulin resistance, which can reduce insulin sensitivity, increase the expression and secretion of proinflammatory cytokines in adipose tissue and promote the development of DM and cardiovascular diseases. Since EFT is a part of the visceral fat, it carries that risk.

Regarding relation to CAD in DM, there have been conflicting data.

Maniam et al reported that EFT was higher in non-diabetics with CVD, but not in T2DM with or without CVD. This suggests EFT may play a greater role in CVD in non-diabetics than those with T2DM.

However, in the past few years, several other studies have reported that EFT is abnormally increased in DM patients. However, small sample sizes and potential confounders (such as differences in EFT measurements and DM typing) were thought to affect the strength of previous evidence.

A metanalysis conducted suggests that the amount of EFT is significantly higher in DM patients than in non-DM patients.

Another study addressing mainly type 1 DM found that Long-term survivors of T1DM have a higher prevalence of coronary atherosclerosis compared to controls but EFT volume was not associated with coronary atherosclerosis in T1DM patients.