Pericardial effusion is the abnormal accumulation of fluid in the pericardial space, the double-layered sac surrounding the heart, due to various causes such as infections, injuries, or chronic diseases. A sudden and significant accumulation of fluid can compress the heart, leading to a life-threatening condition called cardiac tamponade. This condition prevents the heart from filling adequately with blood, reducing the amount of blood pumped to the body and restricting sufficient blood flow to organs. In pericardial effusion, hundreds of milliliters of fluid can accumulate in the pericardial space. The severity of this condition varies depending on the underlying cause, the amount of fluid collected, and how quickly it accumulates.