The pericardium can hold only a limited amount of excess fluid without causing problems. The inner layer of the pericardium is made of a single layer of cells that sticks to the heart. The outer layer is thicker and only somewhat elastic. When too much liquid collects, the pericardium expands inward, toward the heart.

When pericardial effusion puts pressure on the heart, the pumping chambers of the heart fail to fill completely, and one or more chambers may partially collapse. This condition, called tamponade (tam-pon-AYD), causes poor blood circulation and an inadequate supply of oxygen to the body. Tamponade is a life-threatening condition if left untreated.

Aug. 01, 2013