Magnetic Fields and Cardiac Implantable Electronic Devices: Clinical Mechanisms, Device Behaviour, and Occupational Risk Assessment.

Magnetic and electromagnetic fields are increasingly encountered in consumer, medical, and industrial environments, creating frequent clinical uncertainty for patients with cardiac implantable electronic devices. This review synthesises current evidence on the mechanisms by which external fields interact with pacemakers and implantable cardioverter-defibrillators, distinguishing static magnetic field effects from time-varying electromagnetic interference. Static fields may activate device magnet response when brought close to the generator, whereas time-varying fields may induce lead signals causing oversensing, pacing inhibition, or inappropriate therapy. We integrate physical principles, device behaviour, manufacturer guidance, occupational regulations, and real-world exposure data into a practical clinical framework. Most everyday and occupational exposures are manageable with appropriate separation, task modification, and patient-specific assessment. A mechanism-based approach can support proportionate counselling, avoiding both unnecessary restriction from work and under-recognition of genuine risk.