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Electromagnetic Interference With Implantable Cardioverter Defibrillators at Power Frequency: An in vivo Study
Study Questions:
What thresholds of extremely low frequency electric and magnetic fields (ELF-EMFs) present in daily life and occupational environments interfere with appropriate implantable cardioverter-defibrillator (ICD) sensing in vivo?
Methods:
Interference thresholds of 110 ICD patients (one-, two-, three-chamber ICDs) were evaluated in a specifically developed test site. Patients were exposed to single and combined electric and magnetic 50 Hz fields with strengths of up to 30 kVm-1 and 2.55 mT. Tests were conducted considering worst-case conditions including maximum sensitivity of the device or full inspiration.
Results:
With devices being programmed to nominal sensitivity, ICDs remained unaffected in 91 (83%) patients; 5 of 110 (5%) devices showed transient loss of accurate right ventricular (RV) sensing, while 14 of 31 (45%) of the two- and three-chamber devices displayed impaired right atrial (RA) sensing. No interference was detected in 71 (65%) patients within the tested limits with programming to maximum sensitivity, while 20 of 110 (18%) subjects exhibited RV disturbances and 19 of 31 (61%) subjects RA disturbances.
Conclusions:
The authors concluded that ELF daily life EMFs do not disturb sensing capabilities of ICDs. However, strong 50 Hz EMF, present in certain occupational environments, may cause inappropriate sensing, potentially leading to false detection of atrial/ventricular arrhythmic events. When comparing the RA/RV interferences, the atrial lead is more susceptible to EMF.
Perspective:
It is important to identify patients at risk of occupational electromagnetic interference (EMI). EMI may cause oversensing resulting in inappropriate shocks, inhibition of pacing, or a switch to an asynchronous noise-mode. Maximum achievable sensed P wave and R wave should be sought during the implant to decrease the risk of inappropriate sensing. An in vivo provocation study can provide a reliable and individual risk assessment for patients with potential occupational exposures to ELF.
Keywords: Magnetic Fields, Defibrillators, Electromagnetic Phenomena, Heart Atria, Death, Pacemaker, Artificial, Risk Assessment, Electromagnetic Fields, Heart Ventricles
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