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during cardiac arrest, what happens to a person?

During cardiac arrest, the heart suddenly stops effectively pumping, blood flow to the brain and organs ceases within seconds, and the person collapses, stops breathing normally, and quickly loses consciousness. Without rapid CPR and defibrillation, this leads to brain damage and then death within minutes.

What cardiac arrest is

Cardiac arrest is a sudden failure of the heart’s electrical system, so the heart either stops or quivers in a chaotic rhythm instead of pumping blood. It is different from a heart attack, which is usually a blockage of blood flow to part of the heart while the heart can still be beating.

During cardiac arrest:

  • The heart’s normal rhythm breaks down into a dangerous arrhythmia (often ventricular fibrillation or pulseless ventricular tachycardia).
  • Effective blood flow stops, so oxygen no longer reaches the brain and vital organs.

What happens to the person, moment by moment

From the outside, events unfold very fast once cardiac arrest begins.

  1. First few seconds
    • The person may suddenly collapse, often without warning or after brief symptoms like chest discomfort or palpitations.
 * They become unresponsive and cannot answer or follow commands.
  1. Within about 10–20 seconds
    • Breathing stops or becomes abnormal (gasping or agonal breaths, which are not effective breaths).
 * There is no detectable pulse because the heart is not effectively pumping.
  1. Within a few minutes
    • The brain is deprived of oxygen, and brain activity rapidly shuts down, so the person has no awareness or purposeful movement.
 * If blood flow is not restored, brain cells begin to die, leading toward irreversible brain injury.
  1. Beyond about 4–6 minutes without help
    • The risk of permanent brain damage rises sharply.
 * Without return of circulation, the event progresses from cardiac arrest to sudden cardiac death.

Inside the body and brain

During cardiac arrest, the entire body is essentially in a state of “global stroke,” because every organ loses blood supply at once.

Key internal changes:

  • Heart: Abnormal electrical activity stops coordinated contractions, so there is no meaningful cardiac output.
  • Brain: Loss of blood flow causes rapid loss of consciousness, then progressive brain cell injury and death if circulation is not restored.
  • Organs: Kidneys, liver, and other organs also begin to fail as oxygen and nutrients are cut off.

If the heart is restarted:

  • Restoring blood flow (return of spontaneous circulation) can save life, but the sudden return of oxygen can also injure cells further, a process sometimes called reperfusion injury.
  • Outcomes vary: some people recover well; others survive with neurological impairment depending on how long the brain was without adequate blood flow.

What bystanders see and can do

From a practical standpoint, what happens to the person is closely tied to how quickly others respond.

Typical signs a bystander might notice:

  • Sudden collapse to the ground.
  • No response to shouting or shaking.
  • Not breathing or only gasping abnormally.
  • No normal pulse when checked by trained rescuers.

Critical actions:

  • Call emergency services immediately.
  • Start hard, fast chest compressions in the center of the chest (CPR) to manually pump blood to the brain and heart.
  • Use an automated external defibrillator (AED) as soon as possible if available, following its voice prompts to deliver a shock when advised.

What happens after resuscitation (if they are revived)

If CPR and defibrillation restore a heartbeat, the person enters a very fragile recovery period.

Possible experiences and outcomes:

  • Many remain unconscious initially and are treated in intensive care, often with measures to protect the brain, such as controlled temperature management.
  • Some wake up with little or no memory of the event, while others may have confusion, memory gaps, or more severe neurological problems, depending on the duration of poor blood flow.
  • Long-term outcomes range from full recovery to varying degrees of disability or, if damage is too severe, progression to death despite initial resuscitation.

Bottom note: Information gathered from public forums or data available on the internet and portrayed here.