A pacemaker is a small, implanted device designed to regulate heart rhythm by delivering low-energy electrical pulses to keep the heart beating at a steady rate. Despite its function, the answer to whether a patient with one can be defibrillated during cardiac arrest is a definitive yes. The life-saving priority of delivering a high-energy electrical shock to restore a normal heart rhythm overrides all other concerns. However, the procedure requires specific precautions to protect the implanted device from the surge of external electricity.
The Primary Rule for Pad Placement
When a person with an implanted cardiac device needs defibrillation, the most important action is to ensure the defibrillator pads do not make direct contact with the device’s generator. The pacemaker or implantable cardioverter-defibrillator (ICD) is typically visible or palpable as a small bulge under the skin, usually located in the upper chest near the collarbone. Rescuers must visually locate this site before applying the electrode pads.
The electrical current delivered by the defibrillator must be routed through the heart, bypassing the device generator entirely. Standard guidelines recommend positioning the pads a significant distance away, ideally at least eight centimeters from the pacemaker site. This distance helps prevent the high-energy shock from directly damaging the device’s internal circuitry.
If the standard anterior-lateral pad placement would place a pad too close to the device, an alternative technique must be used. The anteroposterior placement is often the best choice, with one pad placed on the front of the chest and the other on the back, usually below the left shoulder blade. This repositioning creates a clear electrical pathway through the heart while minimizing the risk of device interference.
Risk of Device Damage and Malfunction
The high-voltage electrical energy from a defibrillator is powerful enough to cause significant harm to the pacemaker’s components if the current path intersects the device. Direct exposure can lead to physical hardware damage, such as insulation breakdown in the leads that connect the device to the heart muscle. More often, the shock causes electrical or programming corruption that disrupts the device’s function.
This surge of energy can cause the device to “reset” to its factory settings, potentially involving a temporary battery voltage reduction. A reset is dangerous because it might halt the pacing function, leaving a pacemaker-dependent patient without life support. The shock can also corrupt stored diagnostic data, which the patient’s cardiologist needs for ongoing care. The risk of damage is similar whether the implanted device is a pacemaker or an ICD.
Post-Defibrillation Protocols
Following successful defibrillation, emergency medical services (EMS) must be immediately informed that the patient has an implanted device that received an external electrical shock. The patient requires urgent medical evaluation, even if they appear stable. The external shock may have erroneously been sensed by the pacemaker as a dangerous rhythm, causing it to deliver its own internal therapy, which also needs to be checked.
The most important follow-up step is a complete device interrogation performed by a cardiac specialist, such as an electrophysiologist or a trained technician. This process involves using specialized equipment to connect to the pacemaker and download stored information. The specialist verifies that the device’s battery, leads, and internal programming are intact and working correctly. This check ensures that any potential damage or corruption is identified and corrected before it leads to future complications.