Sudden Cardiac Arrest in Australia: What It Is, Who's at Risk, and Why AEDs Save Lives

Every year, approximately 25,000 Australians experience sudden cardiac arrest outside a hospital. Fewer than 10 per cent survive. The single most important factor determining survival — more than ambulance response time, more than CPR quality — is how quickly a defibrillator is applied.

For every minute that passes without defibrillation, survival odds drop by approximately 10 per cent. After 10 minutes without a shock, survival is rare. Paramedics in most Australian cities arrive in 8–12 minutes. The maths is uncomfortable.

This is why AEDs exist — and why having one is increasingly not just recommended, but legally required in South Australia. Read our SA AED legislation guide to understand what's required for commercial buildings.

What Does an AED Actually Do?

An automated external defibrillator analyses the heart's electrical rhythm and delivers a controlled electric shock to interrupt a lethal arrhythmia — typically ventricular fibrillation (VF) or ventricular tachycardia (VT). The AED does the diagnostic work itself. It reads the ECG through the electrode pads, determines whether a shockable rhythm is present, charges to the appropriate energy level, and either prompts the rescuer to press a button (semi-automatic) or delivers the shock automatically (fully automatic).

Who Is Most at Risk of Sudden Cardiac Arrest?

Sudden cardiac arrest can happen to anyone, at any age — but risk increases significantly with:

• Coronary artery disease and previous heart attacks
• Heart failure or cardiomyopathy
• Undiagnosed structural heart abnormalities
• High blood pressure, diabetes, or high cholesterol
• Age over 45 in men or 55 in women
• Family history of sudden cardiac death

For patients managing cardiovascular risk factors at home, see our guides on home blood pressure monitoring and how to take accurate blood pressure readings.

Is My Business Required to Have an AED?

In South Australia, the answer may now be legally yes. The Automated External Defibrillators (Public Access) Act 2022 came into full effect on 1 January 2026, requiring privately owned commercial buildings with 600m² or more of publicly accessible floor space to have a compliant AED installed. See our Queensland AED guide for what QLD businesses should be doing ahead of expected legislation.

Semi-Automatic vs Fully Automatic AEDs

A semi-automatic AED charges to the correct energy and prompts the rescuer to press a button to deliver the shock. A fully automatic AED delivers the shock automatically after a countdown warning. For untrained responders, fully automatic has a practical advantage.

For a full brand and model comparison, see our guide to choosing the right AED for your Australian workplace.

What Happens After the Shock?

CPR must continue between shock cycles. AEDs like the ZOLL AED 3 include Real CPR Help technology — measuring compression depth and rate in real time. The combination of quality CPR and timely defibrillation dramatically outperforms either alone. Our AED training guide covers how to ensure your team is prepared.

What Should My Organisation Do?

1. Install a TGA-registered AED in a visible, accessible location
2. Mount it in an alarmed wall cabinet
3. Add clear AED signage using the internationally recognised ILCOR symbol
4. Register with your state ambulance service
5. Schedule annual testing — NATA-certified calibration certificate for WHS records
6. Brief your team — see our AED training guide for how to do this effectively

For a complete maintenance and compliance checklist, read our AED compliance and maintenance guide.

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