When someone with a pacemaker needs an AED, place the pads at least 6 inches (about 15 cm) away from the implanted device. Pacemakers are typically implanted just below the collarbone on the left side of the chest, and you can usually spot them as a small, hard bulge under the skin with a thin scar nearby. The key rule: don’t put a pad directly over that bulge.
How to Spot an Implanted Device
Before placing AED pads, take a quick look at the person’s bare chest. Pacemakers and implantable defibrillators (ICDs) are inserted through a small incision below the collarbone, usually on the left side, though some are placed on the right. The device sits in a pocket just under the skin, creating a visible bulge roughly the size of a small matchbox. You may also see a thin surgical scar, typically 5 to 10 cm long, running along the upper chest.
You don’t need to know whether the device is a pacemaker or an ICD. The placement guidance is the same for both.
Standard Pad Placement With a Pacemaker
In normal AED use on someone without an implant, one pad goes to the right of the breastbone below the collarbone, and the other goes below the left breast along the side of the ribcage. When a pacemaker is present on the left side, that upper-right pad is usually fine, but the placement of the second pad may need adjusting to keep both pads at least 6 inches from the device.
If you can achieve that 6-inch distance with standard placement, go ahead and use it. The AED will still analyze the heart rhythm and deliver a shock effectively. But if the device sits in a spot that makes standard placement difficult, switch to the anterior-posterior method.
Anterior-Posterior Placement
This alternative approach is specifically recommended for people with implanted cardiac devices. Instead of placing both pads on the front of the chest, you put one pad on the center of the chest (over the breastbone) and the second pad on the back, directly behind the first one between the shoulder blades.
Anterior-posterior placement does two important things. It keeps the pads far from the implanted device, and it routes the electrical current through the heart along a different path that avoids passing directly through the device’s generator and wiring. Clinical guidelines from cardiology societies specifically recommend this configuration for patients with implanted devices to minimize the risk of damage from the external shock.
To use this position, you’ll need to partially roll the person onto their side to apply the back pad, then roll them flat again. This takes a few extra seconds, but the AED will function normally in this configuration.
Why Placement Over the Device Is Risky
Placing an AED pad directly over a pacemaker can cause real problems. The external shock can travel along the device’s internal wiring and deliver concentrated energy to the point where the wire meets the heart muscle. This can temporarily or permanently raise the amount of energy the pacemaker needs to stimulate the heart, a problem called “loss of capture,” where the device can no longer pace effectively.
External shocks can also cause the pacemaker to reset its programming, switching it into a backup pacing mode that may not match what the patient actually needs. In rare cases, the energy can damage the device’s circuits entirely. These aren’t theoretical concerns. They’re documented complications that cardiac device specialists check for after any external defibrillation.
That said, none of these risks should stop you from using an AED on someone in cardiac arrest. A person whose heart has stopped will die without defibrillation. A damaged pacemaker can be reprogrammed or replaced. The priority is always delivering the shock.
What Happens After the Shock
Once paramedics arrive or the person reaches a hospital, the implanted device will need to be checked with a specialized programmer, a handheld computer that communicates wirelessly with the pacemaker. Medical teams will verify that the device’s settings haven’t been altered by the external shock and that it can still pace the heart at the correct energy level. If the shock raised the pacing threshold, the device’s output can often be increased through reprogramming to compensate.
This interrogation is standard protocol after any external defibrillation in a patient with an implant. It’s not something you need to worry about as a bystander, but it helps to mention to paramedics that you noticed an implanted device so they can flag it for the receiving hospital.
Quick Reference for Rescuers
- Look first: Check for a hard bulge and scar below either collarbone.
- Keep distance: Place pads at least 6 inches from the device.
- Switch if needed: Use anterior-posterior placement (one pad on the chest, one on the back) if standard positioning puts a pad too close.
- Don’t hesitate: A pacemaker is never a reason to withhold defibrillation during cardiac arrest.
- Tell EMS: Let paramedics know you saw an implanted device so the hospital can check it.