Pericardial effusion
Too much fluid within the fibrous sac (the pericardium) that surrounds the heart. The inner surface of the pericardium is lined by a layer of flat cells (mesothelial cells). The pericardial sac normally contains a small amount of fluid which acts as a lubricant to allow normal heart movement within the chest. A pericardial effusion refers to the presence of an excessive amount of pericardial fluid, a serous fluid of a pale yellow color, within the pericardium. The term "effusion" comes from the Latin "effusio" meaning a pouring out. A pericardial effusion is, literally, a pouring out of fluid around the heart.
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the accumulation of more than 50 mL of pericardial fluid in the pericardium.
Medical dictionary.
2011.