The epicardium is the layer immediately outside of the heart muscle proper.
is largely made of connective tissue and functions as a protective layer.
During ventricular contraction, the wave of depolarization moves from the endocardial to the epicardial surface.
Adipose tissue in the epicardium is normally a source of cardiovascular development, regeneration, and nourishment, but when activated by systemic inflammation it becomes a source of pro inflammatory adipocytokines including leptin, tumor necrosis factor, Interleukin 1-beta and interleukin-6 which are transmitted directly to underlying tissues.
Systemic inflammation leads to epicardial adipose tissue expansion and explains atrial and ventricular myopathies.
The triad of accelerated coronary atherosclerosis leading to myocardial infarction, atrial myopathy leading to atrial fibrillation and from thromboembolic stroke, and ventricular myopathy leading to heart failure with preserved ejection fraction is seen in many chronic systemic inflammatory disorders including rheumatoid arthritis, chronic HIV infection, non-alcoholic steatohepatitis, and chronic kidney disease: epicardial adipose tissue inflammatory triad
Long-standing systemic inflammatory state can activate visceral fat depots, and the most relevant adipose tissue is that residing in the epicardium.