Pericardial effusion is a buildup of fluid in the space between the heart and the sac around the heart (pericardium).
Pericardial effusion can be caused by pericarditis, an inflammation of the pericardium. Pericarditis may be caused by heart attack, kidney failure, bacterial or viral infection, or cancer treatment.
Pericarditis can also cause chest pain and, in rare cases, increased pressure on the heart (cardiac tamponade).
If the fluid buildup is gradual and the heart is tolerating the increased fluid around it, treatment of the underlying cause may be tried first. In some cases, the fluid might need to be drained.