An automated external defibrillator (AED) analyzes the heart’s electrical rhythm and delivers an electric shock to restart a heart that has stopped beating due to an electrical malfunction. A pacemaker or an implantable cardioverter defibrillator (ICD) is a small, battery-powered medical device surgically placed inside the chest to regulate heart rhythms. When a person with an implanted device collapses from sudden cardiac arrest, using an AED is necessary to save their life. An AED can and should be used, but specific precautions must be taken during the application of the electrode pads to ensure the shock is effective and does not interfere with the implanted hardware.
Understanding Implanted Cardiac Devices
Implanted cardiac devices fall into two main categories: pacemakers and Implantable Cardioverter Defibrillators (ICDs). A pacemaker primarily treats a heart that is beating too slowly or irregularly by delivering small, low-energy electrical pulses to maintain a steady rhythm.
In contrast, an ICD is designed for patients at high risk for life-threatening, fast heart rhythms, such as ventricular fibrillation. Like a pacemaker, an ICD constantly monitors the heart, but when it detects a dangerously fast rhythm, it delivers a high-energy electrical shock to reset the heart. Many modern ICDs also contain a pacing function.
Both types of devices are typically housed in a metal casing, about the size of a pocket watch, and are implanted just under the skin in the upper chest, often near the collarbone. The presence of either device is usually identifiable by a small bulge or a surgical scar in the upper chest area. Caution is necessary during AED use because the external electrical current could potentially be diverted or damage the internal circuitry.
Safe AED Application Guidelines
When a person is unresponsive and not breathing normally, the priority is to immediately begin the cardiac arrest protocol, utilizing an available AED. The first step is to quickly examine the patient’s upper chest for the bump or scar of an implanted device. This visual check is important because the primary instruction is to avoid placing the AED pads directly over the device.
To ensure the external shock travels correctly through the heart muscle, the AED pads must be placed at least one inch (2.5 to 3 centimeters) away from the implant site. Placing a pad directly over the pacemaker or ICD could divert the energy of the shock, making defibrillation ineffective, or cause the internal device to malfunction. Adherence to this clearance rule mitigates the risk of damage.
If the implanted device is located on the upper left chest, the rescuer must adjust the standard pad placement. The standard position, known as anterior-lateral, involves placing one pad on the upper right chest and the second pad on the lower left side, below the armpit. If the device interferes with this placement, an alternative configuration, such as the anterior-posterior position, must be used. This alternative involves placing one pad on the front of the chest and the other pad on the back, between the shoulder blades, ensuring the heart remains in the electrical path. The rescuer should never delay the delivery of the AED shock while waiting for an ICD to deliver its own internal shock.
What to Do After the Shock
Once the AED delivers a shock, the immediate focus remains on the patient’s condition and maintaining circulation. If the patient remains unresponsive and is not breathing normally, the rescuer must immediately resume CPR as instructed by the AED’s voice prompts. The AED will continue to analyze the heart rhythm every two minutes and advise if another shock is required.
The high-energy AED shock may temporarily disable or reprogram the implanted pacemaker or ICD. Therefore, informing emergency medical services (EMS) personnel immediately upon their arrival is necessary. The rescuer must communicate that the patient has an implanted device and confirm that an external defibrillation shock was delivered.
The patient must be transported to a medical facility for a comprehensive follow-up examination. The implanted device requires immediate checking by a cardiologist or specialist. This examination ensures the device’s circuitry and programming are intact and that the device is still functioning correctly.