A pacemaker is a small, battery-powered medical device surgically implanted to regulate a slow or irregular heart rhythm by delivering low-energy electrical impulses. A smartwatch is a consumer electronic device worn on the wrist, integrating features like wireless connectivity, health sensors, and internal magnets for charging and other functions. The combination of this life-sustaining cardiac device and a modern electronic gadget raises an important question about potential electromagnetic interference. While contemporary pacemakers are built with shielding, the close proximity of high-powered consumer electronics necessitates caution. The primary concern is whether the smartwatch’s components can disrupt the pacemaker’s programmed function, depending heavily on the type of signal and the distance between the two devices.
The Main Concern: Smartwatch Magnets
The most direct and widely documented risk comes from the permanent magnets embedded within smartwatches, which are often used for wireless charging alignment, secure bands, or internal speakers. Pacemakers are designed with a magnetic sensor that responds to an external magnetic field, a feature known as “magnet mode.” This mode is intended for medical professionals to temporarily alter the device’s operation during certain procedures.
When a strong magnetic field is detected, the pacemaker typically switches to an asynchronous pacing mode (VOO, DOO, or AOO). In this mode, it delivers impulses at a fixed rate without sensing the heart’s natural rhythm. Studies confirm that a magnetic field strength of approximately 10 Gauss (1.0 millitesla) or greater is sufficient to trigger this change. Research shows that popular smartwatch magnetic fields significantly exceed this 10 Gauss threshold in close proximity.
This magnetic interference becomes dangerous only when the smartwatch or its charging component is placed directly over the implant site. If a person is pacemaker-dependent, this involuntary switch could prevent the device from sensing a deadly arrhythmia or delivering life-saving therapy. The temporary change resolves immediately once the strong magnetic field is moved away from the pacemaker.
Radiofrequency Signals and Pacemakers
Smartwatches also generate electromagnetic interference (EMI) through wireless communication components, including Bluetooth, Wi-Fi, NFC, and cellular LTE signals. These radiofrequency (RF) signals are low-power, and modern pacemakers are generally well-shielded against this type of energy. The consensus is that low-level RF transmission from a smartwatch is unlikely to cause clinically significant interference under normal operating conditions.
A more recent concern involves bioimpedance sensing technology, which many smartwatches use to measure body composition or perform an ECG. This technology works by sending a tiny electrical current through the body. Benchtop testing suggests this current can sometimes create electrical interference that exceeds safety guidelines for implanted cardiac devices.
This electrical interference from bioimpedance could potentially confuse the pacemaker’s sensing circuitry, leading to inappropriate pacing or inhibition of therapy. This electrical risk involves a different mechanism of disruption than the magnetic risk. While the risk from low-power RF is minimal, the electrical current from bioimpedance warrants caution, especially when the device is used close to the implant site.
Official Safety Recommendations and Distances
To mitigate potential interference, major medical device manufacturers and regulatory bodies, including the U.S. Food and Drug Administration (FDA), have issued clear recommendations. The primary precaution is maintaining a separation distance between the smartwatch and the implanted device. This minimum safe distance is widely recommended to be at least 6 inches (15 centimeters).
This distance ensures the static magnetic field from the smartwatch drops below the threshold required to trigger the pacemaker’s magnet mode. Patients should wear the smartwatch exclusively on the wrist opposite the implant site. They must also avoid carrying the smartwatch or its charging accessories in any pocket or bag that rests directly over the chest.
When wirelessly charging a smartwatch, the charging pad should be kept well away from the chest, such as on a nightstand or desk. Consulting with a cardiologist before using a new wearable device is advisable for guidance specific to the individual’s pacemaker model and medical history. Adhering to these distance guidelines allows most individuals with a pacemaker to safely use a smartwatch.