Which of the following is a reversible cause of cardiac arrest that relates to fluids around the heart?

Cardiac Tamponade is a condition characterized by the accumulation of fluid in the pericardial space, which exerts pressure on the heart and ultimately hampers its ability to pump effectively. This condition can lead to decreased cardiac output and cardiac arrest. The fluid exerts external pressure on the heart chambers, particularly during diastole, which limits the heart's filling capacity.

Identifying and treating cardiac tamponade is crucial because it is a reversible cause of cardiac arrest. In emergency situations, intervention may involve procedures such as pericardiocentesis, where the fluid is drained, or surgical intervention depending on the situation. The prompt recognition and treatment of cardiac tamponade can restore normal heart function, making it a key concept in advanced cardiovascular life support (ACLS).

The other options listed represent causes of cardiac arrest that are not specifically related to fluid accumulation around the heart. For instance, coronary thrombosis refers to blockage in coronary arteries, pulmonary embolism involves blockage in the pulmonary arteries typically due to blood clots, and hyperkalemia pertains to high levels of potassium in the blood that can affect cardiac electrical activity but does not involve fluid around the heart.