Surrounding the heart is a sac known as the pericardium

Pericardium

The pericardium is a double-walled sac that contains the heart and the roots of the great vessels.-Layers:...

, which consists of two membranes. The outer layer being the fibrous parietal pericardium and the inner layer being the serous visceral pericardium. It is the serous visceral pericardium that secretes the pericardial fluid into the pericardial cavity

Pericardial cavity

The pericardial cavity is a potential space between the parietal pericardium and visceral layer. It contains a supply of serous fluid. The serous fluid that is found in this space is known as the pericardial fluid....

, (the space between the two pericardial layers). It is similar to the serous fluid that is found in the brain for cushioning and ability to move semi-freely.

Function

The pericardial fluid reduces friction within the pericardium by lubricating the epicardial surface allowing the membranes to glide over each other with each heart beat.

Composition

Ben-Horin et al. (2005) studied the composition of pericardial fluid in patients undergoing open heart surgery

Open Heart Surgery

Open Heart Surgery was released on August 8, 2000 by rock band Virginwool. The band signed to Breaking/Atlantic Records after initially beginning signed to Universal Records. The album was produced and mixed by Brad Wood....

. They found that the fluid is made up of a high concentration of lactate dehydrogenase

Lactate dehydrogenase

Lactate dehydrogenase is an enzyme present in a wide variety of organisms, including plants and animals.Lactate dehydrogenases exist in four distinct enzyme classes. Two of them are cytochrome c-dependent enzymes, each acting on either D-lactate or L-lactate...

 (LDH), protein and lymphocytes. In a healthy adult there is usually 15-50ml of clear, straw-coloured fluid. However there is little data on the normal composition of pericardial fluid to serve as a reference.

Ischemic Heart Disease

In patients with ischemic heart disease there is an accumulation of angiogenic growth factors in the pericardial fluid. These contribute to angiogenesis

Angiogenesis

Angiogenesis is the physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over terminology, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for the formation of new blood...

 (the formation of new blood vessels) and arteriogenesis

Arteriogenesis

-Mechanical Stimulation:Mechanically, arteriogenesis is linked to elevated pressure, which increases radial wall stress, and elevated flow, which increases endothelial surface stress. The vessel increases in diameter until the stress is normalized . Arteriogenesis does not occur every time there...

 (the increase in diameter of existing arterioles). This helps to prevent myocardial ischemia

Myocardial ischemia

Myocardial ischemia is an imbalance between myocardial oxygen supply and demand. Left untreated, it results in angina pectoris, myocardial stunning, myocardial hibernation, ischemic preconditioning, postconditioning, or under the most severe instances, acute coronary syndrome and myocardial...

 (lack of oxygen to the heart).

Pericardial Effusion

A pericardial effusion

Pericardial effusion

Pericardial effusion is an abnormal accumulation of fluid in the pericardial cavity. Because of the limited amount of space in the pericardial cavity, fluid accumulation will lead to an increased intrapericardial pressure and this can negatively affect heart function...

 is the presence of excessive pericardial fluid, this can be confirmed using an echocardiogram. Small effusions are not necessarily dangerous and are commonly caused by infection such as HIV

HIV

Human immunodeficiency virus is a lentivirus that causes acquired immunodeficiency syndrome , a condition in humans in which progressive failure of the immune system allows life-threatening opportunistic infections and cancers to thrive...

 or can occur after cardiac surgery. Large and rapidly accumulating effusions may cause cardiac tamponade

Cardiac tamponade

Cardiac tamponade, also known as pericardial tamponade, is an emergency condition in which fluid accumulates in the pericardium ....

, a life-threatening complication, that puts pressure on the heart preventing the ventricles from filling correctly.

Pericardiocentesis

Pericardiocentesis

Pericardiocentesis

In medicine, pericardiocentesis is a procedure where fluid is aspirated from the pericardium .-Position:The patient undergoing pericardiocentesis is positioned supine with the head of the bed raised to a 30- to 60-degree angle.This places the heart in proximity to the chest wall for easier...

 is a procedure used to remove the pericardial fluid from the pericardial cavity. It is performed using a needle and under the guidance of an ultrasound

Ultrasound

Ultrasound is cyclic sound pressure with a frequency greater than the upper limit of human hearing. Ultrasound is thus not separated from "normal" sound based on differences in physical properties, only the fact that humans cannot hear it. Although this limit varies from person to person, it is...

. It can be used to relieve pressure from pericardial effusions or for diagnostic purposes, revealling the cause of abnormalities such as:
Cancer, Cardiac perforation, Cardiac trauma, Congestive heart failure, Pericarditis rupture of a ventricular aneurysm.