CIED Magnets + Intraop Pacemaker/ICD Management

ICD indications: secondary prevention (survived VT/VF), primary prevention (EF <35% + NYHA II-III, post-MI EF <30%, HCM with risk factors, channelopathies — LQTS, Brugada, CPVT).

CRT indications: HF EF <35% + LBBB QRS >150 ms + NYHA II-IV.

The NASPE/BPEG code (e.g., DDD-R) describes chamber paced, chamber sensed, response, rate-modulation, multisite.

Medtronic: ~85 bpm (drops to 65 bpm as battery depletes).

Boston Scientific: 100 bpm (drops with battery).

Abbott (St.

Jude): 100 bpm then 85 as battery wears.

Mode becomes AOO/VOO/DOO depending on configuration.

Sensing disabled — paces regardless of intrinsic rhythm.

Useful to prevent EMI-induced oversensing inhibition.

ICD + magnet: DISABLES tachy detection + therapy (no shocks, no antitachy pacing).

Does NOT change bradycardia pacing — if patient is pacemaker-dependent with a backup-pacing ICD, the ICD continues to pace in its programmed mode (still sensing → still vulnerable to EMI-induced oversensing inhibition).

PACEMAKER-DEPENDENT + ICD = magnet alone is INSUFFICIENT; you must have the device REPROGRAMMED to an asynchronous mode preop.

This is the single most-tested point in CIED management.

Decide preop reprogramming need based on: pacemaker-dependent (yes → asynchronous), ICD with electrocautery above umbilicus (yes → disable tachy therapy), CRT (consider asynchronous to ensure biventricular pacing during EMI), rate-responsive features (disable — surgical vibration can falsely accelerate pacing).

Monopolar electrocautery is the major intraoperative EMI source: current flows from active tip through patient to grounding pad → if device + leads are in the current path, EMI couples to leads → device senses it as cardiac activity → pacemaker INHIBITS pacing (asystole if dependent), ICD interprets as VT/VF → DELIVERS INAPPROPRIATE SHOCK + ATP.

Site BELOW umbilicus + grounding pad placed so current path doesn't cross device = lower risk; many institutions don't reprogram for below-umbilicus elective cases.

Bipolar electrocautery, harmonic scalpel, plasma coagulation: minimal EMI risk — preferred near device.

Continuous ECG (5-lead), plethysmography or arterial line (mechanical confirmation of perfusion during EMI when ECG is uninterpretable), external defibrillator pads on patient BEFORE start (anterior-posterior placement to avoid the device site — never directly over generator).

Magnet doughnut available + position confirmed by device interrogation report — different manufacturers have different sweet spots; loose-fitting on obese patients may not engage.

For ICDs, magnet ON during electrocautery bursts (suspends tachy therapy), OFF between or at procedure end.

Document magnet rate observed at start (confirms expected manufacturer behavior).

If patient develops VT/VF intraop: remove magnet → ICD will detect + treat; or external defib if ICD slow to respond.

If pacemaker patient becomes bradycardic or paced rhythm drops out: place magnet → asynchronous pacing.

MRI: 'MRI-conditional' devices (most implanted after 2011) tolerate 1.5T or 3T MRI under specific conditions (mode + monitoring); 'legacy' non-conditional devices increasingly studied + done safely in expert centers (MagnaSafe Registry) with specific protocols.

RFA (renal denervation, ablation for AF, tumor): generally safe with bipolar configuration; reprogram + monitor closely.

Postop CIED interrogation is MANDATORY in any of: device was reprogrammed preop (must restore baseline programming), magnet was used intraop on ICD (must verify tachy therapy reactivated), prolonged or above-umbilicus electrocautery, any hemodynamic instability or sustained arrhythmia intraop, lithotripsy/MRI/radiation/RFA/ECT exposure, perioperative resuscitation event.

Patient cannot leave PACU until tachy therapy reactivated for ICD or restored asynchronous-to-DDD reprogramming for PPM.

If interrogation not immediately available, keep patient on continuous telemetry + external defibrillator immediately available.

Document the full chain (preop interrogation, intraop magnet use, postop interrogation) in the anesthetic record.