What condition is characterized by the presence of excessive fluid in the pericardial sac?

The presence of excessive fluid in the pericardial sac is known as cardiac tamponade. This condition occurs when the accumulation of fluid, pus, blood, or other material in the pericardial space exerts pressure on the heart, impairing its ability to fill and pump effectively. This can lead to reduced cardiac output and is often associated with symptoms such as hypotension, distended neck veins, and muffled heart sounds—often described in relation to Beck's triad.

In contrast, cardiac dilation involves an increase in the size of the heart chambers, primarily due to volume overload or damage, rather than fluid accumulation in the pericardial space. Myocardial infarction refers to the blockage of blood flow to a part of the heart, resulting in damage to the heart muscle itself, while heart failure denotes the heart's inability to pump sufficient blood to meet the body’s needs. Neither of these conditions specifically pertains to the accumulation of fluid around the heart.