A pacemaker is a small, battery-operated device implanted beneath the skin, typically near the collarbone, designed to regulate the heart’s rhythm by delivering precise electrical impulses. This device monitors the heart’s natural electrical activity, providing support when the heartbeat becomes too slow or irregular. The widespread use of technology in daily life, particularly devices containing small, powerful magnets, has led to public concern about potential interference. While pacemakers are built with shielding to protect against most common electromagnetic fields, they remain sensitive to strong magnetic fields due to a specific feature built into their design.
How Magnets Temporarily Affect Pacemaker Function
The interaction between a magnet and a pacemaker relies on an intentional engineering feature called the magnetic switch, historically a reed switch. This component is designed to activate when exposed to a magnetic field of sufficient strength, typically around 10 Gauss, a level often exceeded by modern small magnets. When activated, the switch forces the pacemaker into what is known as a “magnet mode.” This mode causes the device to temporarily cease its normal sensing functions, which monitor the heart’s own electrical signals.
Instead of sensing, the pacemaker switches to an asynchronous pacing mode, such as VOO, AOO, or DOO, delivering electrical pulses at a fixed, preset rate, regardless of the patient’s intrinsic heart rhythm. This fixed-rate pacing is protective in a clinical setting, allowing doctors to assess the device’s function without interference from the heart’s natural activity. The device will immediately revert to its original, programmed settings and resume normal sensing and pacing once the magnetic source is moved away from the implant site.
Everyday Items That Contain Small Magnets
Many modern consumer products utilize small but strong magnets, most commonly those made from Neodymium-iron-boron (NdFeB). These magnets are often embedded in the audio components of devices, such as the speakers and microphones found in cell phones and wireless headphones. The magnetic fields from these items are strong enough to activate the pacemaker’s internal switch if held in close proximity.
Magnetic closures are also a source of potential interference, including:
- Latches on certain smartwatches.
- Magnetic jewelry clasps.
- Magnetic snaps or closures incorporated into clothing or handbags.
Items like wireless charging pads for phones and earbuds also contain magnets that facilitate proper alignment and charging.
Establishing Safe Separation Distances
Maintaining a proper spatial distance between the pacemaker and any magnetic item is the most effective way to prevent temporary interference. For the vast majority of common electronic devices, including cell phones, smartwatches, and headphones, the minimum safe separation distance is 6 inches (15 centimeters). This distance allows the magnetic field strength to drop below the threshold required to activate the internal switch.
A cell phone should never be stored in a shirt pocket, jacket pocket, or on a belt positioned directly over the pacemaker site. When using a phone, hold it to the ear on the side opposite the implant, or use the speakerphone function. Magnetic components, like those in wireless earbud cases, should not be set down on the chest or placed in a breast pocket. For stronger magnetic sources, such as those found in some wireless charging stands, a more conservative distance of 12 inches (30 centimeters) is often recommended, especially when the device is actively charging.
Recognizing and Responding to Magnetic Interference
Experiencing magnetic interference can cause a temporary and noticeable change in heart rhythm, often leading to physical symptoms. A person may experience brief feelings of lightheadedness, dizziness, or a sensation of palpitations as the pacemaker switches to its fixed-rate mode. These symptoms occur because the fixed-rate pacing may not be synchronized with the heart’s natural rhythm or meet the body’s current metabolic demands.
The immediate response is to move the magnetic source away from the chest area. As soon as the magnetic field is removed, the pacemaker’s internal switch deactivates, and the device automatically returns to its programmed, normal sensing and pacing functions within a few seconds. If symptoms such as dizziness or a rapid heartbeat persist after the magnetic item has been removed, contact their cardiologist for a device check.