Myocardial fat as a part of cardiac visceral adipose tissue: physiological and pathophysiological view.

Thoracic fat includes extra-pericardial (outside the visceral pericardium) and intra-pericardial (inside the visceral pericardium) adipose tissue. It is called ectopic adipose tissue although it is a normal anatomical structure. Intra-pericardial adipose tissue, which is predominantly composed of epicardial and pericoronary adipose tissue, has a significant role in cardiovascular system function. It provides metabolic-mechanical support to the heart and blood vessels in physiological conditions, while it represents metabolic-cardiovascular risk in case of qualitative and quantitative structural changes in the tissue: it correlates with coronary atherosclerotic disease, left ventricular mass, left atrium enlargement and atrial fibrillation presence. In the last decade there has been mounting evidence of fat cells presence in the myocardium of healthy (non-diseased) persons as well as in persons with both cardiovascular and non-cardiovascular diseases. Thus, it is necessary to clarify the incidence, aetiology, physiological role of fat cells in the myocardium, as well as the clinical significance of pathological fatty infiltration of the myocardium.