Cardiac tamponade is a condition in which the heart is “strangled” by a buildup of fluid within the sac (the pericardium) that surrounds the heart (see fig. 1). This sac normally contains a small amount of fluid which is thought to provide a lubricationg surface for the heart as it beats. Many conditions can cause an abnormal amount of fluid to accumulate. Blood can also collect in the pericardium. If the pressure caused by the fluid in the pericardial sac gets too high, it restricts the heart from filling up during its relaxation phase of the pumping cycle (see fig. 2). When this happens, the heart is not an effective pump. This can result in shock (low blood pressure) or even death. Removing the fluid with a needle (pericardiocentesis) or surgery may be necessary.

Figure 1: Fluid build-up inside the pericardium.

Figure 2: Pressure created by the fluid restricts the heart’s motion and reduces its function.