What is the epicardium commonly referred to as?

The epicardium is commonly referred to as the visceral layer of the pericardium. This layer is integral to the structure of the heart, serving as a protective outer layer that directly adheres to the heart muscle (myocardium). It is part of the pericardial sac and plays a role in the lubrication of the heart’s outer surface, allowing for smooth motion as the heart beats. The epicardium also contains blood vessels, nerves, and fat, contributing to the functional and structural integrity of the heart. This definition aligns with the terminology used in cardiology and anatomy, making "visceral layer" the appropriate descriptor for the epicardium.