The normal pericardium is a fibroelastic sac surrounding the heart that contains a thin layer of fluid. A pericardial effusion is considered to be present when accumulated fluid within the sac exceeds the small amount that is normally present. Pericardial effusion can develop in patients with virtually any condition that affects the pericardium, including acute pericarditis and a variety of systemic disorders. The development of a pericardial effusion may have important implications for prognosis (as in patients with intrathoracic neoplasm), diagnosis (as in myopericarditis or acute pericarditis), or both (as in dissection of the ascending aorta).
Pericardial effusions may develop rapidly (acute) or more gradually (subacute or chronic). The normal pericardium can stretch to accommodate increases in pericardial volume, with the amount of stretch related to how quickly the effusion develops. The ability to stretch is greater with slowly developing effusions. However, regardless of how quickly an effusion develops, with ongoing accumulation of pericardial fluid into a closed space, eventually the intrapericardial pressure begins to increase. When the intrapericardial pressure becomes high enough to impede cardiac filling, cardiac function becomes impaired, and cardiac tamponade can be considered to be present. (See "Cardiac tamponade".)
A general overview of the diagnosis and treatment of pericardial effusion will be presented here. The full spectrum of causes of pericardial disease, management of specific causes of pericardial disease, and the details of pericardial fluid drainage are discussed separately. (See "Etiology of pericardial disease" and "Clinical presentation and diagnostic evaluation of acute pericarditis" and "Emergency pericardiocentesis".)
Pericardial effusions can occur as a component of almost any pericardial disorder (table 1), but the majority result from one of the following conditions (see "Etiology of pericardial disease"):
●Acute pericarditis (viral, bacterial, tuberculous, or idiopathic in origin)