Electromagnetic Interference and Pacemakers

Electromagnetic Interference and the Pacemaker Patient

  • Clinically significant problems with electromagnetic interference (EMI) are rare.
  • Pacemaker's response to EMI becomes more diverse as technology advances.
  • Pacemaker manufacturers develop interference protection circuitry to keep up with vast sources of EMI.
  • Pacemaker's response to EMI depends on:
    • Characteristics of the EMI.
    • Proximity to the interference.
    • Available shielding.
    • Sensing characteristics and polarity of the pacemaker.
  • Pacemaker circuitry attenuates interference outside the normal intracardiac range (10 Hz – 100 Hz) using bandpass filters.
  • EMI sources:
    • Galvanic: Requires direct contact with electrical current.
      • Examples: Defibrillation/cardioversion, cautery, TENS units, and diathermy.
    • Electromagnetic/Electrically coupled: Does not require direct body contact.
      • Examples: Arc welders, ham radios, electrical appliances, metal detectors, therapeutic ultrasound, and high voltage power lines.
    • Magnetic: Occurs in close proximity to an intense magnetic field.
      • Examples: Nuclear magnetic resonance imaging (NMR/MRI) and steel mill induction furnaces.
  • EMI with signal modulation can mimic normal intracardiac signals.
  • Response to EMI may present as:
    • Single beat inhibition.
    • Total inhibition.
    • Noise reversion/asynchronous pacing.
    • Rate increase.
    • Erratic pacing.
    • No output.
  • Responses are usually temporary but can be permanent if the pulse generator circuitry is damaged.
  • Pacemaker's response to EMI is highly dependent on the specific EMI source, pacemaker's mode, and sensing polarity.

EMI Sources and Pacemaker Interactions

  • Ablation (RF):
    • Loss of capture- exit block is frequently seen during RF ablations.
    • Arrhythmia induction, undersensing, inhibition, rate increase and noise reversion pacing are also possible.
    • Circuit damage is less likely than DC ablation.
  • Acupuncture:
    • Low frequency electroacupuncture may cause inhibition and noise reversion at high frequencies.
  • Airport detector/Metal detectors:
    • Single beat inhibition is rare and seen only on unipolar devices.
  • Anti-theft devices/Electronic Article Surveillance (EAS):
    • Possible inhibition or rate increase reported primarily on unipolar devices, especially if patient leans or lingers near EAS.
    • Increased incidence of cross-talk is seen on unipolar DDD pacers.
  • Arc welders:
    • Single beat inhibition is commonly seen on unipolar devices each time the arc is struck.
    • High magnetic fields from the cables may cause reed switch closure resulting in asynchronous pacing.
  • Bone Stimulator:
    • Possible inhibition on unipolar devices.
  • Cardioversion:
    • Cardioversion, performed at high energies similar to that of defibrillation or performed directly over the pulse generator, may damage circuitry resulting in no output, erratic pacing, or rate increases.
    • Energy conducted through the lead may cause arrhythmias and myocardial burning.
  • Cautery:
    • Cautery used near the pacing system may result in inhibition, asynchronous pacing and/or circuit damage.
    • Energy conducted through the lead may cause arrhythmias and myocardial burning.
  • CB radio:
    • Single beat inhibition may be seen with microphone keying on unipolar devices.
  • Cellular phone:
    • Total inhibition or asynchronous pacing is possible with some digital cell phones if placed within 6 inches of the pacemaker.
    • Current SJM pacemakers (Identity, Integrity, Affinity, Trilogy, Synchrony, Paragon, Solus) are cellular tested.
  • CT Scan:
    • No documented reports of interference to date from CT scanners or full body scans.
  • Defibrillation:
    • Defibrillation performed at high energies, or defibrillation directly over the pulse generator, may damage circuitry resulting in no output, erratic pacing, or rate increases.
    • Energy conducted through the lead may cause arrhythmias and myocardial burning.
  • Dental scaler:
    • Older ferromagnetic ultrasonic scalers may cause single beat inhibition on unipolar pacemakers.
    • Piezo-electric scalers have no effect.
    • Activity rate responsive devices may exhibit increased pacing rates.
  • Diathermy:
    • Used in the near vicinity of the pacing system, diathermy may result in inhibition, asynchronous pacing, and/or circuit damage.
    • Energy conducted through the lead may cause arrhythmias and myocardial burning.
  • ECT/EST (Electro-convulsive shock therapy):
    • Inhibition and/or noise reversion is possible, especially with unipolar pulse generators.
    • Activity sensor rate responsive pulse generators may track the seizure activity.
  • Electric blanket/Heating pad:
    • Single beat inhibition is rare and seen only on unipolar devices.
  • Electric shaver:
    • Single beat inhibition is rare and seen only on unipolar devices.
  • Electric switch:
    • Single beat inhibition may be seen on unipolar devices.
  • Electric tools:
    • Single beat inhibition is rare and may be seen on unipolar devices during use of power tools like drills and saws.
  • Electric toothbrush:
    • No effect from standard or ultrasonic models.
  • Electrotome (dental device):
    • Single beat inhibition is rare and seen primarily on unipolar devices.
  • Ham radio:
    • Single beat inhibition may be seen on unipolar devices during microphone keying.
  • Lithotripsy - ESWL:
    • No effect on VVI and VOO pulse generators.
    • DDD pulse generators may track to maximum rate or totally inhibit ventricular output due to ESWL triggering off the atrial output.
    • Activity sensor rate responsive pulse generators may also track to maximum rate or be permanently damaged (piezo crystal shatters near focal point).
  • Magnet therapy:
    • Asynchronous pacing possible if magnetic pads/objects are used within 18 inches of pacemaker.
    • Prolonged asynchronous pacing from magnetic mattress pads is not recommended.
    • Magnetic pads used below the waist will not interfere with pacemaker operation.
  • Microwave ovens:
    • In 1976 the FDA stated there is no longer substantial risk of pulse generator interference from microwave ovens which are now built with leakage protection.
    • Pulse generators are now manufactured to prevent interference from microwaves.
  • MRI (Magnetic Resonance Imaging):
    • Frequent effect from MRI is asynchronous pacing.
    • Reed switch magnetization, rate increases in DDD, single beat inhibitions, component damage, lead dislodgment, rapid pacing (300 PPM), and generator movement within the pocket are also possible but not common.
  • PET Scan:
    • Possible CMOS damage. See Radiation.
  • Power lines, high voltage:
    • 400 kvolt high voltage power lines may cause asynchronous pacing, especially if patient is near a large metal object(e.g. car).
  • Pulp tester:
    • Single beat inhibition is rare but may be seen on unipolar devices.
  • Radar:
    • Single beat inhibition is rare but may be seen on unipolar devices.
  • Radiation, Diagnostic:
    • No effect, even with cumulative doses.
  • Radiation, Therapeutic:
    • Damage to the CMOS circuitry can occur as low as 200 rads in some pacemakers.
    • Devices now manufactured by SJM are tested to 3000 rads.
    • Effect is cumulative in dose and affects both bipolar and unipolar pulse generators.
    • Failure modes include circuit damage, run-away pacer, erratic pacing, sensing anomalies, and no output.
  • Radio transmitter, AM:
    • If signal modulation occurs, inhibition may be seen on unipolar pulse generators, relative to power, frequency, modulation, and proximity.
    • Noise reversion pacing is possible.
  • Radio transmitter, FM:
    • If signal modulation occurs, inhibition may be seen on unipolar pacemakers relative to power, frequency modulation, and proximity.
    • Noise reversion pacing is possible.
  • Respiratory/ECG monitors:
    • Impedance based ECG/respiratory monitors may cause upper rate pacing in impedance based pacemakers especially with monitors emitting a current signal parallel to the pacer system.
  • Shaw scalpel:
    • This non-electric cautery is thermally coupled and will not cause any interference.
  • TENS (Transcutaneous Electrical Nerve Stimulator):
    • Normally used high frequencies (>30 Hz) may cause noise reversion on unipolar pulse generators.
    • Low frequencies (<10 Hz) may cause inhibition on unipolar pulse generators.
    • Burst mode is contraindicated due to probable device inhibition.
  • Therapeutic Ultrasound:
    • Single beat inhibition is rare and may be seen on unipolar devices.
    • Therapy should not be given directly over the pulse generator.
    • Activity sensor rate responsive pulse generators may exhibit piezo crystal shatter.
  • Diagnostic Ultrasound:
    • No effect.

EMI Summary Table

  • EMI Source Interactions and Responses:
    • Y = Yes Possible
    • N = No Effect
    • Y* = Remote Potential for Interference
    • U = Unipolar only
    • B = Bipolar only
    • U & B = Unipolar and Bipolar
    • Dash (-) = No Data
    • 1 = Impedance-based pulse generators
    • 2 = DDD mode only
    • 3 = Piezo crystal-based pulse generators
    • 4 = SJM devices (Identity, Integrity, Affinity, Trilogy, Synchrony, Paragon, Solus) are cellular tested
    • Sources include: Ablation (RF), Acupuncture, Airport detector, Anti-theft device (EAS), Arc welder, Bone stimulator, Cardiokymography, Cardioversion, Cautery/coagulation, CB radio, Cellular phone, CT Scan, Defibrillation, Dental scaler, Diathermy, ECT/EST, Electric blanket/heating pad, Electric shaver, Electric switch, Electric tools, Electric toothbrush, Electrolysis, Electrotome, Ham radio, Lithotripsy, Magnet therapy, Microwave, MRI, PET scanner, Powerline (high voltage), Pulp tester, Radar, Radiation (Diagnostic & Therapeutic), Radio transmitter AM & FM, Respiratory Monitor (Impedance based), Shaw scalpel, TENS, TV transmitter and Ultrasound (Diagnostic & Therapeutic).