Epicardium

Overview
Epicardium describes the outer layer of heart tissue (from Greek; epi- outer, cardium heart). When considered as a part of the pericardium, it is the inner layer, or visceral pericardium.

Its largest constituent is connective tissue and functions as a protective layer. The visceral pericardium apparently produces the pericardial fluid, which lubricates motion between the inner and outer layers of the pericardium.

During ventricular contraction, the wave of depolarization moves from endocardial to epicardial surface.