Version May 2024
INTRODUCTION — While there has always been concern about the potential for electromagnetic interference (EMI) with pacemaker, implantable cardioverter-defibrillator (ICD), and cardiac resynchronization devices function due to interaction between the device and an electromagnetic field, the risk is generally low, unless there is a strong magnet or electrical field close to the generator (table 1) [1,2]. EMI can occur in a variety of settings, but overall is more likely in the hospital environment than in the nonhospital environment [3].
There are reports of cardiac implantable electronic devices (CIEDs) being impacted by sources of EMI in the nonhospital environment (eg, strong magnets, cellular phones, slot machines, laptop computers, etc). There are also disclaimers that wireless sources could be the source of EMI with CIEDs, even though no published data exists (eg, automobile manufacturers providing "caution" for device patients purchasing automobiles with "keyless" entry mechanisms, hybrid engines, etc). Nonetheless, most sources of EMI in the nonhospital environment are not concerning [4,5]. However, with the proliferation of wireless technology, any new device which operates on a new frequency or new technology platform should be assessed for the likelihood of clinically significant EMI.
Electromagnetic interference with medical sources is discussed separately. (See "Pacing system malfunction: Evaluation and management", section on 'Electromagnetic interference' and "Cardiac implantable electronic devices: Long-term complications", section on 'Electromagnetic interference'.)
HOUSEHOLD APPLIANCES — Although there are no studies that have systematically evaluated the effect of household microwave ovens on implanted devices, it is widely accepted that contemporary pacemakers and ICDs are adequately shielded from microwave energy produced by modern appliances [3]. Manufacturers do not recommend any special precautions when using common household appliances, such as televisions, radios, toasters, microwave ovens, and electric blankets; UpToDate experts agree with this approach. As a new appliance that uses a new or different energy source reaches the market, the appliance needs to be tested to determine whether there is any potential for device interference.
There are circumstances in which a device may be affected by specific sources of energy under narrow circumstances. This was illustrated in a study assessing the potential for induction cook tops to interfere with pacemaker function. Patients with a unipolar, left-sided implant could experience interference if the pot was not concentrically placed on the induction coil and if the patient stood as close as possible to the cook top. The most common response to interference was a reset to an asynchronous interference mode [6]. Most contemporary devices utilize bipolar pacing and sensing configuration, which minimizes the chance of device malfunction from electromagnetic interference.
CELLULAR TELEPHONES — The widespread use of cellular telephones requires a heightened awareness of their potential for adverse effects on cardiac device function.
Equipment with high-strength magnets — Patients with a pacemaker or an ICD should be aware that strong magnetic fields in close proximity to their device generator can alter normal cardiac device function [7-10]. Electronic equipment (eg, cellular phones with strong magnets for wireless charging) and accessories with powerful magnets (eg, watch bands) should be stored at least 15 inches away from pacemaker or ICD generators (figure 1 and picture 1). In general, we advise all patients to use cellular telephones at the ear on the side opposite the cardiac device and carry cellular telephones in a pocket below the waist. Similar warnings apply to magnets included in clothing, accessories, and elsewhere. (See 'Small magnets incorporated into clothing, furniture, and identification badges' below.)
When equipment with a strong magnetic field is in close proximity to an ICD or pacemaker generator, the cardiac device defaults to magnet mode. Generally, magnet mode causes ICDs to suspend tachyarrhythmia therapies (eg, shocks and antitachycardia pacing) until the magnet is removed. Magnet mode causes pacemakers to asynchronously pace at rates and modes determined by the type of device and manufacturer (table 2). (See "Perioperative management of patients with a pacemaker or implantable cardioverter-defibrillator", section on 'Magnet application' and "Pacing system malfunction: Evaluation and management", section on 'Magnet application'.)
While there are too many devices and magnet applications to provide a complete list of equipment and scenarios to avoid, the following case reports highlight specific devices and use scenarios that may induce magnet mode in an ICD or pacemaker:
●Working with a laptop on the chest while recumbent [7].
●Using a wristwatch with a magnetic band [11].
●Using a cellular phone with a magnetic array for wireless charging (eg, iPhone 12) [8].
Large interrogation studies describe the rate of unintended magnet mode induction (events) as between 7 and 11 events per 100 patient years [9,12]. Neither study recorded malignant arrythmias during magnet mode induction, suggesting that most magnet mode activations were short-lived.
Equipment without high-strength magnets — Cellular telephone equipment without strong magnets is unlikely to cause clinically significant interference with pacemakers or ICDs [13-18]. However, cellular phones may disrupt telemetry, and patients should avoid using the cellular phone during telemetry [19]. In addition, patients should use the telephone at the ear on the side opposite the cardiac device and carry the telephone in a pocket below the waist. Use on the contralateral side will maximally reduce the risk of interference [20,21].
SECURITY SYSTEMS — Electromagnetic security systems (eg, antishoplifting gates, metal detectors) are in widespread use, and are often present in or near the workplace, in shopping malls, and at airports. Although device interference is possible, it is unlikely that any clinically significant interference would occur with the transient exposure associated with walking through such a field. There are case reports of inappropriate shocks and pacemaker inhibition associated with continued close exposure to electromagnetic security systems [22]. The best recommendation for patients is to move through the detection and do not stop close to the detectors (ie, be aware of the location of security systems and simply move through them at a normal pace) [1]. Single-beat inhibition of a device by anti-theft equipment would not be of clinical concern.
Permanent pacemakers — Electronic security systems can potentially interfere with pacemakers [23-25]. The frequency and type of complications were evaluated in a study of 204 patients who were exposed to an electronic security system for up to 30 seconds [23]. One or more episodes of pacemaker function interference developed in 17 percent of patients. Sensing abnormalities were the most common type of interference, and they were typically transient, lasting only for the duration of exposure. In patients with dual chamber pacemakers, interference at the atrial level was more common than at the ventricular level.
In another report, the most common complications were asynchronous pacing, atrial oversensing (producing a tachycardia in the ventricle), ventricular oversensing (with pacemaker inhibition), and paced beats due to direct induction of current in the pacemaker [24]. Symptoms such as palpitations and presyncope occurred in some patients while they were in the security system field. Interference with pacemaker function can occur at a distance of 50 cm from the security system [25]. This is of particular concern for those who are fully pacemaker-dependent; such patients should avoid remaining in close proximity to a security system.
General consensus is that it is safe for airport personnel to use a hand held metal detector or 'wand' for patients with a permanent pacemaker, even for those who are pacemaker-dependent. Additionally, a manual or pat-down search can be performed [1].
Implantable cardioverter-defibrillators — There are case reports of a patient with an ICD in whom interference from an electronic antitheft-surveillance device resulted in the delivery of multiple shocks due to oversensing [22,26]. In contrast, no interference was noted in another report of 25 patients with an ICD who were exposed to the fields of six different electronic article surveillance systems using three modes of operation (magnetic audio frequency, radiofrequency, or acoustomagnetic) [24].
The duration of exposure is an important determinant of risk as illustrated in a study of 170 patients with variable exposure to three common systems [27]. This again emphasizes the basic principle of "move through the detection and do not stop close to the detectors."
General consensus is that it is safe for airport personnel to use a hand held metal detector or 'wand' for patients with a ICD. Additionally, a manual or pat-down search can be performed [1].
EXTERNAL ELECTRICAL EQUIPMENT — Potential causes of concern in the workplace are welders, industrial welding machines, electric motors, and degaussing coils [1,28]. Functional evaluation of pacemakers and ICDs in the work place has rarely demonstrated oversensing of an external electrical field. Nevertheless, since interference remains a concern, it is recommended that assessment of potential electromagnetic sources in the workplace be considered when the patient returns to work. For the non-pacemaker dependent patient this should rarely, if ever, be a problem. For the pacemaker-dependent and/or ICD patient it may be necessary to monitor the patient with an ambulatory monitor to determine if proximity to and/or use of specific equipment results in any interference. Rarely, for patients that are felt to be at higher risk or using equipment that is known to generate higher electromagnetic fields, it may be necessary to have the work environment assessed by an occupational safety officer or engineer prior to return to work [1].
LEAKAGE OF CURRENT FROM ELECTRICAL EQUIPMENT DRIVEN BY A POWER LINE — Depending on the environment the patient is in, several scenarios could be considered. There has been concern raised regarding the potential for interference in CIED patients living under or near commercial power-lines. There is no sound evidence that any significant interference occurs in this situation [29].
For monitoring or therapeutic purposes, a patient may be connected to electromechanical equipment that is connected to a power-line. Such connections may permit accidental flow or leakage of weak alternating current through patients to ground. Similarly, an intracardiac catheter may provide a low-resistance path to ground through the patient's heart and thereby place the patient at risk for electrically induced ventricular tachyarrhythmia [30].
As previously noted, faulty household appliances have the potential for causing interference in patients with a CIED. Similarly, there have been multiple reports of CIED interference from a nongrounded or current-leaking light in swimming pools [31].
TRANSCUTANEOUS MUSCLE/NERVE STIMULATORS — There are several case reports of electromagnetic interference resulting from transcutaneous muscle or nerve stimulation which caused inappropriate ICD discharges [32]. However, for many patients with implantable devices a transcutaneous stimulator can be used. For the pacemaker dependent and/or ICD patient, a monitored in-clinic assessment while operating the stimulator in the desired location should be considered prior to allowing the patient to use the equipment. It should be noted that commercial transcutaneous stimulators such as those used in doctor and chiropractor offices use larger currents and thus are more likely to cause interference.
SMALL MAGNETS INCORPORATED INTO CLOTHING, FURNITURE, AND IDENTIFICATION BADGES — Patients occasionally ask about the use of magnets that have been incorporated into clothing, jewelry, furniture (specifically mattresses), and identification badges. While there could be potential for electromagnetic interference with a CIED, it would be dependent on the strength of the magnet. There is a relative paucity of published literature, although there are case reports of small magnets in a variety of devices (eg, snaps sewn inside a patient's jacket, continuous positive airway pressure mask for sleep apnea, etc) resulting in interference and audible alerts from an ICD [33-36]. In general, there is minimal to no concern unless a strong magnet is positioned directly adjacent to the CIED; strong magnets can induce magnet mode in pacemakers and ICDs. (See 'Equipment with high-strength magnets' above.)
MAGNETIC RESONANCE IMAGING — Issues relating to magnetic resonance imaging and cardiac devices are discussed separately. (See "Patient evaluation for metallic or electrical implants, devices, or foreign bodies before magnetic resonance imaging", section on 'Cardiovascular implantable electronic device'.)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Pacemakers (The Basics)")
●Beyond the Basics topic (see "Patient education: Pacemakers (Beyond the Basics)")
●Basics topic (See "Patient education: Implantable cardioverter-defibrillators (The Basics)".)
●Beyond the Basics topic (See "Patient education: Implantable cardioverter-defibrillators (Beyond the Basics)".)
SUMMARY AND RECOMMENDATIONS
●Background – While there is the potential for electromagnetic interference with pacemaker, implantable cardioverter-defibrillator (ICD), and cardiac resynchronization devices function in the nonhospital environment, the risk of a clinically significant problem is generally low. (See 'Introduction' above.)
●Household appliances – Pacemaker manufacturers do not recommend any special precautions when using normally functioning common household appliances, such as televisions, radios, toasters, microwave ovens, and electric blankets. UpToDate experts agree with this approach. (See 'Household appliances' above.)
●Cellular telephones – Patients with a pacemaker or an ICD should be aware that strong magnetic fields (eg, selected cellular phones [iPhone 12], magnetic accessories) in close proximity to their device generator (figure 1 and picture 1) can alter normal cardiac device function. Cellular telephone equipment without strong magnets is unlikely to cause clinically significant interference with pacemakers or ICDs. The safest strategy is for all patients to use cellular telephones at the ear on the side opposite the cardiac device and carry the telephones in a pocket below the waist. (See 'Cellular telephones' above.)
●Security systems – While inappropriate ICD shocks and pacemaker inhibition have been associated with prolonged exposure to electromagnetic security systems (eg, antishoplifting gates, metal detectors), similar problems are only rarely seen in brief exposure. Patients should be advised to be aware of the location of security systems and to move through them at a normal pace (ie, "don't linger, don't lean"). (See 'Security systems' above.)
●Issues relating to magnetic resonance imaging and cardiac devices are discussed separately. (See "Patient evaluation for metallic or electrical implants, devices, or foreign bodies before magnetic resonance imaging", section on 'Cardiovascular implantable electronic device'.)
ACKNOWLEDGMENT — The UpToDate editorial staff thank David L Hayes, MD, who contributed to earlier versions of this topic review.
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