Cardiac tamponade is a condition caused by too much fluid in the space between the heart and the sac that surrounds it, called the pericardium. This fluid collection can put weight and pressure on the heart, which means that it cannot expand properly and so it does not fill with normal amounts of blood.
Cardiac tamponade is an emergency condition. The inability of the heart to pump enough blood may eventually lead to heart failure.
WebMD Medical Reference from Healthwise