Anaes · Measurement & monitoring physics

Diathermy, pacemakers and electromagnetic interference

Also known as Diathermy and pacemakers · Electromagnetic interference · CIED management · Pacemaker EMI · ICD perioperative · Cardiac implantable electronic device

Cardiac implantable electronic devices (pacemakers and ICDs) are exquisitely sensitive to electromagnetic interference (EMI), and monopolar diathermy is the commonest perioperative EMI source. The framework rests on six exam-critical ideas. First, a PACEMAKER senses the intrinsic cardiac electrical activity and delivers a pacing stimulus only when the intrinsic rate falls below a programmed threshold; modern pacemakers are also RATE-RESPONSIVE (adjusting the pacing rate to activity sensors). Second, an ICD (implantable cardioverter defibrillator) continuously monitors the heart rhythm and delivers anti-tachycardia pacing or a defibrillating shock when it detects a ventricular tachyarrhythmia. Third, monopolar DIATHERMY generates an electromagnetic field that the pacemaker or ICD may misinterpret as cardiac electrical activity — electrosurgery can damage the generator, inhibit pacing, activate asynchronous pacing or induce ventricular fibrillation, so an active management plan during electrosurgery is critical. Fourth, a MAGNET placed over a pacemaker typically triggers ASYNCHRONOUS (fixed-rate) pacing — the device paces at a fixed rate regardless of intrinsic activity, preventing inhibition by EMI; a magnet placed over an ICD SUSPENDS tachyarrhythmia detection (preventing inappropriate shocks) but does not affect pacing — though the response is device-specific and must be confirmed at pre-operative interrogation. Fifth, perioperative management scales with distance: thoracic electrosurgery causes EMI in 45% of cases, head/neck 35%, upper extremity 15%, abdominal surgery above the iliac crest 3%, and nothing below the iliac crest — so ICDs and pacing-dependent devices within 6 inches of the site are reprogrammed (therapies off, asynchronous pacing if dependent), ICDs further away but above the iliac crest get a magnet, and most others need no change. Sixth, other sources of EMI include MRI (in-vitro work confirms a 3T field can affect non-3T-compatible devices), radiofrequency ablation, extracorporeal shock-wave lithotripsy, peripheral nerve stimulators and electroconvulsive therapy — each requiring a specific management plan. Built on the electrosurgical-hazards review (Pearce 1985), the lead-perforation-tamponade report (Martinez-Ponce 2026), the CIED-perioperative consensus (Guglietta 2024), the leadless-pacemaker-air-embolism report (Ollitrault 2026), the MRI-CIED-EMI study (Fukuoka 2026), the CIED-infection-trends study (Baldauf 2026), the CIED-infection-vacuum-management study (Pranevicius 2026), the epicardial-pacemaker-anaesthesia report (Hu 2026), the ICD-ON perioperative registry (Gifford 2017), and the electrosurgery-principles review (Vilos 2013).