Hemopericardium refers to blood in the pericardial sac of the heart. It is clinically similar to a pericardial effusion, and, depending on the volume and rapidity with which it develops, may cause cardiac tamponade.The condition can be caused by full-thickness necrosis (death) of the myocardium (heart muscle) after myocardial infarction, chest trauma, and by over-prescription of anticoagulants. [Source: Wikipedia ]