What are the Two Non-Shockable Rhythms in Cardiac Arrest?

There are four main heart rhythms that can occur during a cardiac arrest. In this blog post, we will take a closer look at the two non-shockable rhythms.

‘Non-shockable’ means that defibrillation is not an effective treatment for these heart rhythms. If an Automated External Defibrillator (AED) detects a non-shockable rhythm, it won’t allow the rescuer to deliver an electrical shock to the victim.

The only treatment of non-shockable rhythms is high-quality CPR and Advanced Cardiac Life Support (ACLS) including drug treatments and identifying any reversible causes of the cardiac arrest.

The two non-shockable cardiac arrest rhythms are:

  • Asystole
  • Pulseless Electrical Activity (PEA)


Asystole occurs when all electrical activity in the heart stops. This is sometimes referred to as “flat-lining” by the media and medical television shows.

Unfortunately, asystole does not respond to defibrillation and the survival chances for the patient are incredibly low. The only treatment for asystole is high-quality cardiopulmonary resuscitation (CPR) and drugs.


Pulseless Electrical Activity (PEA)

Pulseless Electrical Activity (PEA) occurs when there is a rhythm (normally associated with a pulse) but the patient is in cardiac arrest.

Causes of a PEA cardiac arrest include:

  • Severe blood loss
  • Low oxygen levels (hypoxia)
  • Low body temperature (hypothermia)
  • Traumatic injuries

As with asystole, PEA is not treated with defibrillation. Treatment should focus on performing high-quality CPR and identifying the underlying cause of the PEA cardiac arrest.

Once again, unless there is a clearly reversible cause, the survival chances for a patient in PEA are small.

John Furst

JOHN FURST is an experienced emergency medical technician and qualified first aid & CPR instructor. John is passionate about first aid and believes everyone should have the skills and confidence to take action in an emergency situation.

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