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 — the consequences are PACEMAKER INHIBITION (the device stops pacing because it thinks the heart is beating), REPROGRAMMING (the device settings are corrupted), or RATE-RESPONSIVE OVERDRIVE (the device paces fast because the EMI mimics exertion); in an ICD the EMI may be misinterpreted as ventricular fibrillation, triggering an INAPPROPRIATE SHOCK. Fourth, a MAGNET placed over a pacemaker 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. Fifth, the perioperative management of a patient with a CIED follows the principles of the ASA/HRS guidelines: pre-operative INTERROGATION (check device type, pacing dependency, battery, recent thresholds); INTRAOPERATIVE choice of BIPOLAR diathermy where possible, or monopolar with the return plate positioned so the current path does not cross the device; short, intermittent bursts below 5 seconds; and a MAGNET available; and POST-OPERATIVE re-interrogation to check settings and thresholds. Sixth, other sources of EMI include MRI (static and gradient fields and RF pulses, with 3T MRI effects on non-compatible devices studied), radiofrequency ablation, extracorporeal shock-wave lithotripsy, peripheral nerve stimulators and electroconvulsive therapy — each requiring a specific management plan. Built on the pacemaker-implantation-complications review (Johnson 2026), the lead-perforation-tamponade report (Martinez-Ponce 2026), the leadless-pacing-and-S-ICD study (Dyrbus 2026), 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), and the epicardial-pacemaker-anaesthesia report (Hu 2026).