The pericardium is a closed cystic membrane that covers the surface of the heart and is divided into a fibrous layer and a plasma layer. The fibrous layer is tough and less stretchable and serves to limit excessive enlargement of the heart chambers. The plasma membrane layer is divided into a wall layer, which lies adjacent to the fibrous layer, and a dirty layer, which is attached to the surface of the heart and is the outer membrane of the heart. A potential cavity exists between the mural and visceral layers.
When body fluid or blood collects in this potential space due to infection, tumour, renal failure, puncture injury, etc., it is called a pericardial effusion. Due to the restriction of the fibrous layer of the pericardium, the progression of intrapericardial effusion can affect the pulsation and cardiac output, developing into for a cardiac tamponade, affecting cardiac function leading to haemodynamic disturbances and even causing death.