Cardiac tamponade is a condition caused by the accumulation of fluid in the pericardial sac, which surrounds the heart. Normally there is a small amount of fluid present, but too much fluid builds pressure and prevents the heart from filling properly. Symptoms include chest pain, difficulty breathing, and low blood pressure. The excess fluid must be drained through procedures like pericardiocentesis in order to relieve pressure on the heart and stabilize the patient. Left untreated, cardiac tamponade can cause loss of consciousness and sudden death due to insufficient blood flow.