Which condition is characterized by a fluid-filled space around the heart?

The condition characterized by a fluid-filled space around the heart is pneumopericardium. This condition occurs when air leaks into the pericardial cavity, which is the space surrounding the heart. The pericardium is a double-walled sac that contains the heart and provides a protective barrier. When air enters this space, it can lead to various complications, including cardiac tamponade, which is a life-threatening condition where the pressure from the air compresses the heart and affects its ability to pump blood effectively.

In contrast, pneumothorax involves the presence of air in the pleural space around the lungs, pneumomediastinum refers to air in the mediastinum (the central compartment of the thoracic cavity), and subcutaneous emphysema occurs when air is trapped under the skin. Each of these conditions involves air but does not specifically involve a fluid-filled space around the heart.