Pericardial effusion. Coloured coronal computed tomography (CT) scan of the heart of a 72-year-old patient with a pericardial effusion following heart bypass surgery. The heart (blue) is at lower centre and the chest wall is seen down right in this frontal view. A pericardial effusion is a condition where a large, abnormal amount of fluid accumulates in the pericardial space surrounding the heart. This can prevent the heart from effectively pumping blood. In an emergency, a needle can be used to drain the fluid from the pericardial space. The pericardial space is the space between the heart and the pericardium, the membranous sac enclosing the heart. The bright blue areas show blood in and around the heart. Spinal bones are seen at left.