Sudden cardiac arrest (SCA) can happen anywhere, at any time — at work, at home, or in a public space. It’s one of the leading causes of premature death in the UK, with over 30,000 out-of-hospital cardiac arrests (OHCAs) reported each year. Yet, with the right equipment in place and the right actions taken quickly, survival is possible.
This guide explains the life-saving role defibrillators play in cardiac emergencies, why time is critical, and how automated external defibrillators (AEDs) — devices that analyse heart rhythm and deliver a shock if needed — have revolutionised public access to emergency care.
What Is Sudden Cardiac Arrest?
Sudden cardiac arrest is not a heart attack. A heart attack is a plumbing problem — a blockage prevents blood from reaching part of the heart muscle. Cardiac arrest, however, is an electrical problem — the heart’s rhythm becomes disordered and stops pumping blood altogether.
The most common cause is ventricular fibrillation (VF), a chaotic and ineffective rhythm that must be treated immediately. Without oxygenated blood reaching the brain and vital organs, a person can lose consciousness within seconds and die within minutes. Survival rates drop by around 10–12% for every minute defibrillation is delayed.
How Defibrillators Work
A defibrillator delivers a carefully timed electric shock to stop the abnormal rhythm and give the heart a chance to restart with a normal rhythm. This process is called defibrillation. If a shockable rhythm like VF is present, the shock may restore a life-sustaining heartbeat. If not, CPR must be continued until emergency services arrive.
In medical settings, trained professionals use manual defibrillators. In public or workplace settings, automated external defibrillators (AEDs) are designed for non-clinical users, analysing the heart rhythm automatically and guiding the rescuer through every step.
Why Time Matters: Every Minute Counts
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After 1 minute, survival drops by 10–12%.
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By 5 minutes, brain damage is highly likely without intervention.
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After 10 minutes, survival is unlikely unless CPR and defibrillation were initiated quickly.
That’s why AEDs are installed in busy environments like schools, shopping centres, offices, gyms, and transport hubs. When positioned and signposted correctly, they allow bystanders to act immediately.
However, while early use of an AED is vital, calling 999 should always be the first action. Emergency call handlers will talk you through what to do, dispatch an ambulance, and often guide you to the nearest available AED — especially if it’s registered on The Circuit, the national defibrillator network.
The Chain of Survival
The Chain of Survival is a recognised UK framework for increasing cardiac arrest survival rates:
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Early recognition and call for help – Call 999 and alert others.
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Early CPR – Begin chest compressions immediately.
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Early defibrillation – Use the nearest AED to deliver a shock.
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Advanced life support – Paramedics provide airway management and medication.
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Post-resuscitation care – Hospital treatment to stabilise and recover.
Each link in the chain must work smoothly for the best possible outcome.
What Makes AEDs So Effective?
AEDs are engineered for simplicity and speed. They:
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Analyse the patient’s heart rhythm automatically
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Deliver a shock only if needed
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Use voice and visual prompts to guide users
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Work with paediatric pads or switch in child emergencies
Some models are fully automatic (they deliver a shock without user action), while others are semi-automatic (the user presses a button when prompted).
In the UK, AEDs can be used by anyone — no training or medical knowledge is required. However, training and familiarisation improve confidence and effectiveness, especially in workplace settings.
The Impact of AEDs in Public Spaces
Studies have shown that using an AED within 3 minutes of collapse can increase survival rates to up to 70%. In the UK, organisations like the British Heart Foundation, Resuscitation Council UK, and The Circuit national AED database are working to improve public access and awareness.
Our own experience across sectors like rail, education, and leisure confirms the value of site-specific AED deployment — when units are visible, accessible, and monitored, they save lives.
Manual Defibrillators in Clinical Settings
While AEDs are the right choice for most public settings, manual defibrillators remain essential in hospitals and ambulances. They:
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Require ECG interpretation by trained professionals
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Offer adjustable energy levels
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Can monitor patient vitals and rhythm over time
These devices form the foundation of resuscitation care in critical care units, theatres, and paramedic response.
Common Myths About AEDs — Debunked
“You need medical training to use one” – Not true. AEDs are safe, intuitive, and designed for public use.
“I might shock someone by mistake” – AEDs assess the heart rhythm and will not deliver a shock if it’s not needed.
“Defibrillators restart a stopped heart” – AEDs correct dangerous rhythms like VF. They are not effective in cases of asystole (flatline). CPR is essential to maintain blood flow until a shockable rhythm returns.
Our Expertise in AED Programmes
Whether you’re starting from scratch or managing multiple defibrillators, we support:
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Site surveys for correct quantity and placement
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Product selection tailored to your environment
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Wall cabinets, signage, carry cases, and paediatric kits
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Training via our partners at East of England Ambulance Service
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Day-to-day governance, annual servicing, and consumable replacement
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Remote monitoring and PUWER-compliant documentation
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Leasing options to support rollout and budgeting
Owning a defibrillator is not enough. A successful AED programme requires a system: clear policies, visible placement, signage, ongoing maintenance, a restocking plan, trained responders, and post-incident support. With the right setup, your AED will always be ready when it matters most.
We’ve helped organisations across the UK implement, expand, and maintain life-saving defibrillator programmes.
Final Thought: Be the Difference
Sudden cardiac arrest is unforgiving — but with the right tools, preparation, and response, survival is absolutely possible.
Every second counts. And every organisation that prepares properly can be the difference between life and death.
