Echocardiographic Epicardial Fat: A Review of Research and Clinical Applications

Epicardial fat plays a role in cardiovascular diseases. Because of its anatomic and functional proximity to the myocardium and its intense metabolic activity, some interactions between the heart and its visceral fat depot have been suggested. Epicardial fat can be visualized and measured using standard two-dimensional echocardiography. Standard parasternal long-axis and short-axis views permit the most accurate measurement of epicardial fat thickness overlying the right ventricle. Epicardial fat thickness is generally identified as the echo-free space between the outer wall of the myocardium and the visceral layer of pericardium and is measured perpendicularly on the free wall of the right ventricle at end-systole. Echocardiographic epicardial fat thickness ranges from a minimum of 1 mm to a maximum of almost 23 mm. Echocardiographic epicardial fat thickness clearly reflects visceral adiposity rather than general obesity. It correlates with metabolic syndrome, insulin resistance, coronary artery disease, and subclinical atherosclerosis, and therefore it might serve as a simple tool for cardiometabolic risk prediction. Substantial changes in echocardiographic epicardial fat thickness during weight-loss strategies may also suggest its use as a marker of therapeutic effect. Echocardiographic epicardial fat measurement in both clinical and research scenarios has several advantages, including its low cost, easy accessibility, rapid applicability, and good reproducibility. However, more evidence is necessary to evaluate whether echocardiographic epicardial fat thickness may become a routine way of assessing cardiovascular risk in a clinical setting.