When someone suffers a Sudden Cardiac Arrest (SCA), their heart is no longer pumping blood effectively. The most important intervention at this point is a combination of CPR and a shock from a defibrillator.
While CPR keeps blood and oxygen circulating, only a shock from an Automated External Defibrillator (AED) can reset the heart’s electrical system and restore a normal rhythm.
Shockable vs Non-Shockable rhythms
A defibrillator does not work on every type of cardiac arrest. It only delivers a shock if the person’s heart is in certain abnormal rhythms that can potentially be corrected. These are known as shockable rhythms.
If the heart is in a rhythm that a shock will not help, the defibrillator will simply advise you to continue CPR until emergency services arrive.
Shockable Rhythms
There are two heart rhythms that can be treated with a defibrillator shock:
Ventricular Fibrillation (VF)
- The heart’s electrical activity becomes chaotic.
- The ventricles quiver instead of contracting, so no blood is pumped around the body.
- A shock can stop the chaos, giving the heart a chance to reset into a normal rhythm.
Pulseless Ventricular Tachycardia (VT)
- The heart beats too fast for blood to be pumped effectively.
- Without a pulse, this is a life-threatening emergency.
- A shock can reset the rhythm back to normal.
Both VF and pulseless VT are the most common causes of sudden cardiac arrest and are the main reasons early defibrillation is so critical.
It is vital to have a defibrillator nearby in an emergency, and one that is straightforward to use. We offer a range of defibrillators suited for untrained and trained responders.
Non-Shockable Rhythms
There are also rhythms where a defibrillator cannot help. In these cases, CPR and advanced medical support are the only options.
- Asystole (flatline): The heart has no electrical activity at all. A shock will not restart it.
- Pulseless Electrical Activity (PEA): The heart shows some organised electrical activity on a monitor, but it is not producing a pulse or pumping blood.
In both situations, high-quality CPR and rapid medical intervention are vital to give any chance at survival.
How a Defibrillator Knows
One of the most reassuring things about modern Automated External Defibrillators (AEDs) is that they are designed for anyone to use. The device:
- Analyses the heart rhythm automatically
- Decides whether a shock is needed
- Gives clear voice prompts guiding the rescuer through every step
This means you do not need to worry about diagnosing heart rhythms yourself, the AED will do the work for you.
Peace of mind with Defib Warehouse
Defib Warehouse has been one of the most trusted suppliers of defibrillators online since 2013, offering devices from all major brands, including ZOLL, Philips, Physio Control and Primedic.
