Electromagnetic Interference of Pacemakers by Mobile Phones

The topic of interference of pacemakers by mobile phones has evoked a surprisingly strong interest, not only in pacemaker patients, but also in the public opinion. The latter is the more surprising, as in the past, the problem of interference has scarcely found the attention that it deserves in the interest of the patient. It was the intention of our investigation to test as many pacemaker models as possible to determine whether incompatibility with mobile phones of different modes may exist, using an in vitro measuring setup. We had access to 231 different models of 20 manufacturers. During the measurements, a pulse generator together with a suitable lead was situated in a 0.9 g/L saline solution, and the antenna of a mobile phone was positioned as close as possible. If the pulse generator was disturbed, the antenna was elevated until interference ceased. The gap in which interference occurred was defined as “maximum interference distance.” All three nets existing in Germany, the C-net (450 MHz, analogue), the D-net (900 MHz, digital pulsed), and the E-net. (1,800 MHz, digital pulsed) were tested in succession. Out of 231 pulse generator models, 103 pieces corresponding to 44.6% were influenced either by C- or D-net, if both results were totaled. However, this view is misleading as no patient will use C- and D-net phones simultaneously. Separated into Cor D-net interference, the result is 30.7% for C or 34.2% for D, respectively, of all models tested. The susceptible models represent 18.6% or 27% of today's living patients, respectively. All models were resistant to the E-net. With respect to D-net phones, all pacemakers of six manufacturers proved to be unaffected. Eleven other manufacturers possessed affected and unaffected models as well. A C-net phone only prolonged up to five pacemaker periods within 10 seconds during dialing without substantial impairment to the patient. Bipolar pacemakers are as susceptible as unipolar ones. The following advice for patients and physicians can be derived from our investigations: though 27% of all patients may have problems with D-net phones (not C- or E-net), the application should generally not be questioned. On the contrary, patients with susceptible devices should be advised that a distance of 20 cm is sufficient to guarantee integrity of the pacemaker with respect to hand held phones. Portables, on the other hand, should have a distance of about 0.5 m. Pacemaker patients really suffering from mobile phones are very rare unless the phone is just positioned in the pocket over the pulse generator. The contralateral pocket or the belt position guarantees, in 99% of all patients, undisturbed operation of the pacemaker. A risk analysis reveals that the portion of patients really suffering from mobile phones is about 1 out of 100,000. Nevertheless, it would be desirable in the future if implanting physicians would use only pacemakers with immunity against mobile phones as guaranteed by the manufacturers     

Incidence of Electromagnetic Interference in Implantable Cardioverter Defibrillators

KOLB, C., et al. : Incidence of Electromagnetic Interference in Implantable Cardioverter Defibrillators. Electromagnetic interference (EMI) with ICDs can lead to temporary inhibition of the device or to inappropriate delivery of antitachycardia pacing and shocks. The incidence of interactions between electronic devices and the current generation of ICDs is not known. In a retrospective study of 341 patients (665 patient-years) who underwent a regular follow-up every 3 months, five episodes of EMI were detected in four different patients. The risk for receiving inappropriate shocks due to EMI is < 1% per year and patient. In conclusion, although inappropriate delivery of shocks by ICDs due to EMI rarely occurs, patient information should emphasize the avoidance of situations of possible interference. Further efforts concerning lead technology and detection algorithms are necessary to minimize the risk of EMI.     

Interference in Pacemakers

We attempt here to outline the different sources of interference and the methods of interference detection and protection with their advantages and disadvantages. A proposal is made as to how a better interference suppression could be established. A comparison of 16 pacemakers from ten manufacturers tested with different interference sources revealed a great variety, which does not allow one to generalize the problem of interference. As an example, an electric steel furnace with its magnetic field is described and how its influence on pacemakers can be estimated. Rules are given as to how pacemaker patients may be treated by electrotherapy. A test procedure for characterizing the specific interference behavior is proposed.     

The Response of Implanted Dual Chamber Pacemakers to 50 Hz Extraneous Electrical Interference

Twenty-two patients with dual chamber pacemakers with interchangeable lead configuration were exposed to 50 Hz electromagnetic interference. Current, al corporeal levels from 0–600 μA, was applied between electrodes on shoulders and feet using a bedside injection unit. Pacemaker behavior was monitored with telemetered event markers and intracardiac eJectrograms. In bipolar mode, noise reversion mode was induced in all except two Medtronic units at high (> 170 μA) levels of corporeal current, In the Inlermedics, Siemens Pacesetter, and Telectronics models, onset of noise reversion mode was preceded by a window of inappropriate function, characterized by rate acceleration due to atriai maisensing, or pacemaker inhibition due to ventricular nialsensiiig. In unipolar mode, pacemaker malfunction occurred at much lower current levels. Inappropriate behavior preceded the onset of protective noise reversion mode. During current injection, all pacemakers could be interrogated and reprogrammed, and intracardiac telemetry was reliably obtained except in two Medtronic units at high current levels. No pacemaker was reset by the electrical interference, and no cross-talk was seen. Use of bipolar mode confers a high decree of protection from extraneous electrical interference, but in unipolarmode pacemakers may be inhibited by small amounts of corporeal current, potentially encountered in every day life. The current injection anit allows safe, controllable, and quantifiable investigation of the effects of the electric field induced by a current on implanted pacemakers. Telemetry of annotated intracardiac signals during electromagnetic interference clarifies observations of pacemaker acceleration and inhibition.     

Electromagnetic Interference of External Pacemakers by Walkie-Talkies and Digital Cellular Phones: Experimental Study

A number of experimental and clinical studies have documented the risk potential of interference with implanted pacemakers by various types of cellular phones. Radiofrequency susceptibility of external medical equipment has also been reported in experimental studies. The purpose of this experimental study was to evaluate electromagnetic interference of external pacemakers by walkie-talkies and digital cellular telephones. External bipolar pacing was monitored using a digital oscilloscope to record pacemaker pulses and electromagnetic interference separately. Tests with the walkie-talkie, Private Mobile Radio (PMR) (160 MHz, 2.5 W) were conducted during the calling phase. Tests with the cellular phones, global system for mobile communications (GSM) (900 MHz, 2 W) and Digital Cellular System (DCS) (1,800 MHz, 1 W) were conducted in the test mode. Nine widely used external pacemakers from four manufacturers were tested. Various disturbances including pacing inhibition and asynchronous pacing were observed in eight pacemakers by the PMR, in four by the GSM phone, and in two by the DCS phone. The maximum distance that interference persisted ranged from 10–200 cm. This experimental study shows a potential risk of interference of external pacemakers by walkie-talkies and cellular digital phones. Appropriate warnings should be issued against the potentially serious risks of using communication devices in the vicinity of acutely ill patients treated with temporary transvenous cardiac pacemakers.     

Electromagnetic Interference of Analog Cellular Telephones with Pacemakers

The aim of this study was to verify whether there is a public health risk from the interference of analog cellular telephones with pacemakers. We used a human trunk simulator to reproduce an actual implant, and two cellular telephones working with the TACS (Total Access Communication System) standard. Results showed that the electromagnetic field radiated from the analog cellular telephones interfered with a large number of the pacemakers tested (10/25). When the telephone antenna was in close proximity to the pacemaker head, pacemaker desensitizing and sensitizing and pulse inhibition was detected at the moment of an incoming call and throughout ringing. In the worst case of pulse inhibition, the pacemaker skipped three nonconsecutive beats and then resumed its normal pacing, while the desensitizing and sensitizing phenomena persisted as long as the interfering signal was on. Pulse inhibition was also observed when the connection did not succeed. Maximum sensing threshold variation was about 186% (increase) and 62% (decrease) for desensitizing and sensitizing phenomena, respectively. It was also demonstrated that the signal emitted by analog cellular telephones during the crossing of contiguous cells could induce pacemaker pulse inhibition, but under our experimental conditions this event did not seem to pose a risk for the pacemaker patient.     

Electromagnetic Interference of Digital and Analog Cellular Telephones with Implantable Cardioverter Defibrillators: In Vitro and In Vivo Studies

The present study examines the potential electromagnetic interference effects induced by cellular telephones on ICDs. We developed ad hoc protocols to conduct both in vitro and in vivo trials on most of the implantable cardioverter defibrillators available on the international market. Trials were conducted with three cellular telephones: two GSM (Global System for Mobile Communication) and one TACS (Total Access Communication System). A human trunk simulator was used to carry out in vitro observations on six ICDs from five manufacturers. In vivo tests were conducted on 13 informed patients with eight different ICD models. During the trials in air, GSM telephones induced interference effects on 4 out of the 6 cardioverter defibrillators tested. Specifically, pulse inhibition, reprogramming, false ventricular fibrillation, and ventricular tachycardia detections occurred, which would have entailed inappropriate therapy delivery had this been activated. Effects were circumscribed to the area closely surrounding the connectors. When the ICD was immersed in saline solution, no effects were observed. Three cases of just ventricular triggering with the interfering signal were observed in vivo.     

Implantable Cardioverter Defibrillator: Possible Hazards of Electromagnetic Interference

We report on three patients with an automatic, implantable cardioverter defibrillator (AICD, CPI) in whom the device had been deactivated due to electromagnetic interference. In all cases, the source of the electromagnetic disturbances could be identified.     

Induction Ovens and Electromagnetic Interference:

Electromagnetic fields may interfere with normal pacemaker function. Despite the introduction of modern pacemakers and bipolar lead systems, electromagnetic interference (EMI) still remains to be a concern during daily lives when patients are exposed to cellular phones, electronic security systems, and several household appliances. The aim of this study was to evaluate potential EMI risk of induction ovens, which are increasingly used in private households. The study included 40 consecutive patients (22 men, 18 women; age   73 ± 11  years   ) with implanted DDD, VVI, VDD, and AAI pacemaker systems. The pacemakers were programmed to unipolar sensing and pacing. Sensitivity remained unchanged, if the measured sensing threshold was more than twice the programmed value; otherwise, it was set at half of the measured sensing threshold. Patients were placed in a sitting position at the closest possible distance of about 20 cm between two cooking pots and pacemaker bending the upper part of the body slightly over the induction oven. The energy was increased stepwise to the maximum. One pot was removed and placed again at the highest oven level. Potential interference was monitored continuously. The study showed no incidence of pacemaker malfunction during the entire test while the patients with intrinsic cardiac rhythms were exposed to the induction oven at varying energy strengths. Likewise, there was no external interference when the patients were paced at heart rates of 10–15 beats/min above their heart rates. The programmed parameters remained unchanged after the study. In conclusion, this study shows no EMI risk of an induction oven in patients with bipolar or right-sided unipolar pacemakers. (PACE 2003; 26[Pt. I]:1494–1497)     

Electromagnetic Device‐Device Interaction between a New Generation Implantable Pacemaker and Left Ventricular Assist Device: Recognition and Potential Solutions

An electromagnetic interaction between St. Jude Medical Inc. (St. Paul, MN, USA) permanent pacemakers and HeartMate II left ventricular assist devices (LVADs) (Thoratec Inc., Pleasanton, CA, USA) has been reported before, but the problem was thought to be resolved in the St. Jude Medical's most recently released pacemaker platform. We report a case of interference between the HeartMate II LVAD and the most recently released St. Jude Medical pacemaker (model no. PM3210; Anthem) and review new developments to overcome the electromagnetic interference problem in this setting. (PACE 2010; 1–3)     

The Effects of Electronic Article Surveillance Systems on Permanent Cardiac Pacemakers: An In Vitro Study

Five Siemens Pacesetter cardiac pacemakers (PM) were subjected to in vitro testing with six different electronic article surveillance (EAS) devices. The PMs consisted of polarity programmable, dedicated bipolar, and dedicated unipolar types. EAS equipment included UHF, RF, Magnetic, and Magnetoacoustic (MA) devices from two manufacturers. Prior to testing, each PM was interrogated and normal operation confirmed. Each PM was attached to a heart simulator via an eight foot cable and then subjected to testing within the EAS field. The PMs were passed through the field in two axes, positioned stationary within the field, and, worst case (WC), placed directly against the transmitter. During testing the ECG was observed and PM behavior recorded. In one PM (Synchrony III^R), Event Records, and Event Histograms were utilized. At the conclusion of testing with each EAS device the PM was evaluated for normal operation. Results: No PM was reprogrammed by the EAS devices. UHF produced no effect on the PMs. RF produced noise response in one unipolar PM while in the WC position. High frequency and multifrequency magnetic units produced positive results only in the WC position. Unipolar PMs were affected more often than bipolar. MA and older magnetic EAS units produced more positive responses than newer lower power devices. One incident of close coupled (400 msec) ventricular pacing was seen with the MA EAS unit. Conclusions: UHF, RF, high frequency, and dual frequency magnetic FAS produced few effects during in vitro testing. Except with the MA and low frequency magnetic devices, positive results occurred only in WC conditions. Additional in vitro and in vivo testing is required to evaluate the interaction between PM patients and EAS devices. Careful evaluation of MA EAS systems with a wide variety of PMs is indicated to rule out RF induction through the lead system of the PM.     

Electromagnetic Interference of an Implantable Loop Recorder by Commonly Encountered Electronic Devices

De COCK, C.C., et al. : Electromagnetic Interference of an Implantable Loop Recorder by Commonly Encountered Electronic Devices. Electromagnetic interference of pacemaker systems has been well established and can lead to an inappropriate function of these devices. Recently, an implantable loop recorder (ILR) (REVEAL, Medtronic Inc.) has been introduced to evaluate the possible arrhythmic etiology of patients with recurrent syncope. We evaluated the interference of this device in two patients with implantable ILR and in three nonimplanted ILRs with four electromagnetic sources: cellular phones (GSMs), electronic article surveillance systems (EASs), metal detector gates (MDGs), and magnetic resonance imaging (MRI). The GSM did not affect appropriate function of the ILR whereas radiofrequency (RF) EAS could interfere with normal function in implanted and nonimplanted systems. The MDG had no influence on ILR function. The magnetic field induced by the MRI resulted in an irreversible error in one nonimplanted ILR. Therefore, although interference between electromagnetic sources and ILRs appears to be rare in our study, physicians should be aware of possible malfunctioning of these devices.     

Electromagnetic interference in implantable pacemakers.

The inhibited pacemaker (VVI or AAI) has become the most popular in recent years because of its ability to combine a physiological advantage with economical current consumption in cases with spontaneous activity. One of its disadvantages is its sensitivity to external electromagnetic interference. Though today's pacemakers possess effective protection against most interference signals there may be instances in which patients are subjected to uncomfortable or even life-threatening situations. This is the case of "amplitude modulated" or "pulsed" fields with modulation frequencies in the physiological range. Fields of that sort have been found in the vicinity of a welder, an electric steel plant, and in medical practice where therapeutic currents were applied. Even touch-actuated switches may influence a demand pacemaker. However, these situations may be overcome by a device within the pacemaker for simple time analysis which can be carried out with few components. If electromagnetic fields of diathermy equipment are applied, today's pacemakers may react with intolerably high or low rates. They should, therefore, be avoided.     

Implantation of Pacemakers and Implantable Cardioverter Defibrillators in Orally Anticoagulated Patients

AL-KHADRA, A.S.: Implantation of Pacemakers and Implantable Cardioverter Defibrillators in Orally Anticoagulated Patients. The safety of pacemaker and defibrillator implantations in orally anticoagulated patients using standard techniques has not been thoroughly evaluated. This article describes a prospectively collected experience in such patients. Patients presenting for device implantation who were treated with warfarin were allowed to continue therapy provided that the INR was <3.5. Implantations involved cannulation of the left axillary vein. Except for defibrillator leads, 7 Fr introducers were used, and all were leads actively fixated. The study included 47 patients who underwent implantation of permanent pacemakers (n = 39), defibrillators (n = 5), or biventricular pacemakers (n = 3). The mean INR was 2.3. The primary indication for anticoagulation was a mechanical cardiac prosthesis in 11 (24%) patients. Atrial fibrillation was present in 33 patients. There were no instances of major bleeding or hematomas requiring evacuation. One patient had a small soft hematoma, which resolved spontaneously. At 6 weeks, all patients had well-healed scars with satisfactory pacing and sensing thresholds. In experienced centers, patients requiring treatment with warfarin may undergo implantation of pacemakers or defibrillators with minimal risk despite continuation of anticoagulation. (PACE 2003; 26[Pt. II]:511–514)     

Implementation of a Postoperative Electronic Health Record Alert for Cardiac Implantable Electronic Device Patients

PurposeApproximately 2% of surgical patients have an existing cardiac implantable electronic device (CIED). Perioperative device reprogramming requires postoperative care to ensure that device settings are restored. Electronic health record (EHR) alerts have been shown to improve communication between providers and decrease time to necessary interventions in other areas of medicine. The aim of this quality improvement project was to create an EHR alert for postoperative CIED patients who require device reprogramming to help clinicians track, remember, and document the timely and safe restoration of device settings.DesignThis project used a pre-post observational design.MethodsThis project was conducted at a major academic medical center using a pre-post observational design. To prevent anesthesia providers from closing an encounter in the EHR before postoperative restoration of device settings, an alert was developed and embedded within the intraoperative EHR to track preoperative device reprogramming, and alert anesthesia providers to perform and document postoperative restoration of safe settings.FindingsThe postimplementation group (n = 272) had fewer unknown or undocumented preoperative CIED interventions (12.9% vs 30.9%), a 7.3% shorter device suspension time (median = 165 minutes vs 178 minutes), 6.8% improvement in documentation of postoperative re-enabling of device therapies (78.8% vs 72.0%), and a 72.48% decrease in length of stay (median = 625 hours vs 172 hours) when compared with the preimplementation group (n = 132).ConclusionElectronic prompts effectively captured patients who received preoperative CIED reprogramming and provided a process for reprogramming devices to safe settings, both significant steps in preventing negative patient outcomes associated with undocumented CIED interventions. Perioperative CIED documentation improved, and length of stay decreased after project implementation.