What is the simplest description of cardiac arrest?

The simplest description of cardiac arrest is the absence of cardiac output. Cardiac output refers to the amount of blood that the heart pumps in a minute, and during cardiac arrest, the heart is unable to effectively pump blood due to either a failure of the electrical system or the mechanical function of the heart itself. Without blood circulation, vital organs, including the brain, do not receive the oxygen and nutrients they need, leading to immediate life-threatening consequences.

Other options do not accurately capture the overall condition of the heart during a cardiac arrest. Failed respiration refers to the inability to breathe, which can occur in various situations, not just cardiac arrest. Persistent bradycardia involves a slower than normal heart rate and does not account for total cardiac failure. An irregular heartbeat (arrhythmia) may present during cardiac arrest but does not define the condition itself; cardiac arrest is characterized specifically by the total lack of effective heart action.