Role of the Pericardium in Diastolic Dysfunction

Pericardial diseases are often confused with other pathologic entities such as chronic liver diseases, heart failure, and restrictive cardiomyopathies. The pericardium is the external layer of the heart providing protection and support to inner structures. It is composed of an external fibroserosal part (parietal pericardium) and an internal serosal part (visceral pericardium or epicardium). The normal thickness of the pericardium is less than 3 mm in imaging studies. The pericardium acts as a relatively inelastic sac because of its high content of collagen fibers enveloping the heart and providing mechanical protection to the heart allowing movement of cardiac chambers without attrition, and also limiting their distension and affecting diastolic function. This effect is especially evident on right cardiac chambers. This effect explains the exaggerated interventricular interdependence that can be observed in pathologic conditions (e.g., cardiac tamponade and constrictive pericarditis), as well as how rapidly accumulating pericardial fluid may be responsible of cardiac tamponade with limited amount of fluid, such as 200 to 300 mL in hemopericardium. On the contrary, slowly accumulating pericardial fluid can allow the generation of large pericardial effusions as 1 to 2 L without the development of cardiac tamponade (e.g., large chronic pericardial effusions).