Epicardial adipose tissue

Epicardial adipose tissue (EAT) is the visceral fat depot between the myocardium and the visceral pericardial layer, sharing its microcirculation with the heart and — unlike other fat depots — separated from the myocardium by no fascial barrier. This contiguity enables paracrine and vasocrine signalling: in metabolic dysfunction, EAT secretes pro-inflammatory cytokines (IL-6, TNF-α, CCL2), profibrotic mediators (TGF-β, matrix metalloproteinases), and free fatty acids directly into adjacent myocardium and coronary adventitia, promoting cardiomyocyte fibrosis, conduction delay, and plaque vulnerability. EAT is quantified by cardiac CT (voxels approximately −190 to −30 HU) or by echocardiography (thickness on the right ventricular free wall at end-systole); CT shows stronger prognostic associations than echo in head-to-head data. A 2023 meta-analysis of 29 studies (19,709 patients; Chong et al., Circ Cardiovasc Imaging) found odds ratios of 2.53 and 2.63 for cardiac death and myocardial infarction. EAT volume expands with age independent of weight gain; CT attenuation — reflecting local inflammation — is a proposed complement to volume, though randomised interventional evidence remains limited.