Most people think of the pericardium as just a double-layered, membranous sac (The Pericardial Cavity) that is around the heart. But, the pericardium is actually TRIPLE layered: the visceral layer, the parietal layer, and the fibrous layer (fibrosa).The visceral pericardium is the inner-most layer of the pericardium, and is also known as the Epicardium as it lays upon the heart.The Pericardial Cavity lies between the visceral pericardium and the parietal pericardium.ost people think of the pericardium as just a double-layered, membranous sac (The Pericardial Cavity) that is around the heart. But, the pericardium is actually TRIPLE layered: the visceral layer, the parietal layer, and the fibrous layer (fibrosa).