When a sudden cardiac arrest (SCA) strikes, every second counts. In those frantic moments, an Automated External Defibrillator (AED) is the single most effective tool available to bystanders to help save a life. However, if you open a casualty’s shirt and notice a distinct scar or a hard, raised lump just under their collarbone, panic can set in. You realise they have an implanted medical device.
A flood of questions might race through your mind: Can you use an AED on someone with a pacemaker? Will the electric shock explode the device? Will the pacemaker block the defibrillator from working? Is it safe to proceed?
The direct answer is yes, you absolutely can and should use an AED on someone who has a pacemaker. However, there is a vital protocol modification you must follow regarding pad placement to ensure the shock works effectively and the device remains undamaged.
Can You Put an AED on Someone Who Has a Pacemaker?
The short answer is a resounding yes. If an individual with an implanted pacemaker falls unconscious, stops breathing normally, and shows no signs of life, they are experiencing sudden cardiac arrest. Without immediate intervention, their chances of survival drop by roughly 10% for every minute that passes without cardiopulmonary resuscitation (CPR) and defibrillation.
To understand why it is entirely safe and necessary to use an AED, it helps to distinguish how these two devices function:
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A Pacemaker: This is a small, battery-powered device implanted under the skin (usually near the left or right collarbone). It continuously monitors the heart’s natural rhythm. If it detects that the heart is beating too slowly (bradycardia) or skipping beats, it emits tiny, low-energy electrical pulses to prompt the heart to beat at a normal rate. It is a regulatory system for a living heart.
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An AED (Automated External Defibrillator): This is a portable electronic device designed to treat life-threatening cardiac arrhythmias, specifically Ventricular Fibrillation (VF) and pulseless Ventricular Tachycardia (VT). During these events, the heart’s electrical activity becomes completely chaotic, causing the ventricles to quiver uselessly instead of pumping blood. An AED delivers a high-energy electrical shock to momentarily “reset” the heart, allowing its natural pacemaker to reclaim control.
When a person goes into cardiac arrest, their pacemaker has failed to prevent or fix the fatal arrhythmia. The pacemaker cannot deliver the massive energy burst required to stop ventricular fibrillation; only an AED can do that. Therefore, the presence of a pacemaker must never delay or prevent the use of a defibrillator.
Where Do You Place AED Pads on Someone with a Pacemaker?
While you must use the AED, you cannot simply stick the pads down without looking. Standard AED pad placement requires one pad to be placed on the upper right chest (just below the collarbone) and the other on the lower left side of the chest (just below the armpit).
Because many pacemakers are implanted under the right collarbone, a standard pad placement could end up sitting directly on top of the medical device.
The One-Inch Rule
When applying AED pads to a casualty with an implanted device, follow the one-inch rule (approximately 2.5 centimetres). You must ensure that the adhesive AED pad is placed at least one inch away from the visible bulge or scar of the pacemaker.
Why Avoid Direct Placement?
There are two critical scientific reasons why an AED pad should never cover a pacemaker:
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Electrical Deflection: The metal casing of a pacemaker can absorb, block, or redirect the electrical current emitted by the AED. If the current is diverted, an insufficient amount of energy will travel through the myocardium (the heart muscle), reducing the likelihood of successfully shocking the heart back into a viable rhythm.
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Device Damage: While modern pacemakers are built with internal shielding to withstand external electrical interference, a direct, high-energy shock from an AED pad placed squarely over the unit can permanently fry its circuitry or burn the surrounding myocardial tissue where the pacemaker leads connect.
Alternative Strategy: Anterior-Posterior Placement
If the casualty has a pacemaker or an Implanted Cardioverter-Defibrillator (ICD) positioned in a way that makes standard chest placement difficult to alter by an inch, you can use Anterior-Posterior (front and back) placement.
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Place one pad directly over the centre of the casualty’s chest (on the sternum).
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Place the second pad directly on their back, between the shoulder blades.
Most modern AEDs are designed to function perfectly with this path of electrical travel, and it keeps the current entirely clear of a pacemaker located near the collarbone.
Who Should You Not Use an AED On?
While an AED is remarkably safe and incorporates internal computer software that will never deliver a shock unless it detects a shockable rhythm, there are specific scenarios where modifications or extreme caution must be exercised.
1. Infants Under One Year of Age (With Caveats)
Historically, guidelines were hesitant about using automated defibrillators on infants under 12 months. Today, UK Resuscitation Council guidelines state that an AED can be used on an infant if no manual defibrillator is available. However, you should ideally use paediatric pads or a machine with a paediatric attenuator switch, which reduces the energy dose from a standard adult level (typically 150–360 joules) down to a safer infant level (50–75 joules). If adult pads are all that are available, they can be used via anterior-posterior placement to ensure the pads do not touch each other.
2. Casualties Lying in Water
Water is an excellent conductor of electricity. If a casualty has been pulled from a swimming pool, a lake, or heavy rain, you must not shock them while they are pooling in water. The electricity from the AED will travel across the wet skin or puddles on the ground, bypassing the heart completely and potentially shocking bystanders or the first aider. Always drag the casualty to a dry area and quickly wipe their chest dry before applying the pads.
3. Explosive Environments
Never deploy an AED in an atmosphere high in volatile gases, uncontained oxygen tanks, or open chemical spills (such as at a petrol station forecourt or specific industrial settings). The tiny electrical spark generated when a shock is delivered could cause an explosion.
What Devices Should I Avoid with a Pacemaker?
To provide comprehensive context for individuals living with an implanted device—or those caring for them—it is helpful to understand the wider landscape of electromagnetic interference (EMI). While an AED is an emergency tool used only when a life is on the line, daily life involves navigating everyday devices that could temporarily disrupt a pacemaker’s programming.
Modern pacemakers are highly advanced and robustly shielded, but individuals should remain cautious around objects generating strong electromagnetic fields:
| Device Category | Risk Level | Safety Protocol |
| Smartphones & Headphones | Low | Keep at least 6 inches (15 cm) away from the pacemaker. Do not store your phone in a breast pocket. |
| Store Security Scanners | Low | Walk through at a normal pace. Do not linger or lean against the security gates. |
| Induction Hobs | Moderate | Keep a distance of at least 12 inches (30 cm) from the cooktop, as the magnetic fields can interact with the device. |
| Metal Detectors (Airport Security) | Moderate | Inform security staff. Request a manual pat-down, as the handheld detector wand should not be held over the device. |
| Industrial Arc Welding Equipment | High | Avoid entirely. The heavy electromagnetic fields can temporarily cause the pacemaker to misinterpret signals. |
| MRI Scanners | High | Standard MRIs are dangerous. However, many modern pacemakers are now classified as “MRI-conditional,” requiring specific programming adjustments prior to a scan. |
Step-by-Step Protocol: Using an AED on a Pacemaker Patient
If you witness someone collapse and suspect cardiac arrest, follow this exact sequence to ensure both efficiency and safety:
[ Casualty Collapses & Unresponsive ]
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[ Call 999 & Request an AED ]
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[ Begin High-Quality CPR ]
(30 compressions : 2 breaths)
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[ AED Arrives & Turn On ]
│
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[ Expose Chest & Inspect ]
Look/feel for a pacemaker lump or scar.
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[ Apply Defibrillator Pads ]
Place pads at least 1 inch (2.5cm) away
from the device, or use front/back.
│
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[ Follow Vocal Prompts of AED ]
Stand clear if a shock is advised. Resume
CPR immediately after.
Elevate Your Confidence with Hands-On First Aid Training
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FAQs About Using an AED on Someone with a Pacemaker
Can an AED restart a stopped heart?
No. Contrary to what is often depicted in television dramas, an AED cannot restart a heart that has completely flatlined (asystole). An AED looks for specific disorganised electrical rhythms like Ventricular Fibrillation. If the heart has no electrical activity left, the AED will state “No shock advised,” and you must continue high-quality CPR to manually pump oxygenated blood to the brain.
Can you use an AED on a pregnant woman?
Yes. Sudden cardiac arrest in a pregnant person is a double emergency. Saving the mother is the absolute best way to save the unborn child. The AED pads are placed in the standard positions, and the electrical current does not pose a direct threat to the foetus relative to the fatal alternative of untreated cardiac arrest.
What happens if I accidentally place the pad over a pacemaker?
If a pad is placed over a pacemaker and a shock is delivered, the shock may be less effective because the metal casing deflects some of the energy away from the heart muscle. The device itself may also suffer electronic damage. If you realise your error after a shock has been given, immediately adjust the pad placement for the next cycle of analysis, but do not stop CPR to do so.
