Pericardium

The pericardium is the double-walled fibrous sac that surrounds and encloses the heart and the roots of the great vessels (the aorta, pulmonary artery, vena cavae, and pulmonary veins). It has two main layers: the tough outer fibrous pericardium and the inner serous pericardium, which itself has two layers (the parietal and visceral layers). The space between the two serous layers (the pericardial space) normally contains 15 to 50 ml of lubricating fluid.

The pericardium serves several functions. It anchors the heart in a fixed position within the chest, limits acute overdistension of the heart chambers, and provides a smooth lubricated surface that allows the heart to move freely with each beat. It also provides a barrier against the spread of infection from adjacent structures.

Disease of the pericardium takes three main forms. Pericarditis (inflammation of the pericardium) causes sharp chest pain that is typically worse lying flat and relieved sitting forward, ECG changes, and elevated inflammatory markers; it is usually viral in origin and recurrent pericarditis can be debilitating. Pericardial effusion (excessive fluid accumulation in the pericardial space) can compress the heart (cardiac tamponade), causing haemodynamic compromise and cardiac arrest, when large. Constrictive pericarditis (chronic scarring and thickening) restricts cardiac filling and is treated with pericardiectomy (surgical removal of the pericardium).

The pericardium is also relevant to cardiac surgery (opened to access the heart) and to post-cardiac injury syndrome (a delayed inflammatory response after heart surgery or myocardial infarction, causing pericarditis and effusion).