Interference in pacemakers

Influence of electrical stimulation therapy on permanent pacemaker function

BACKGROUND

Electrical stimulation therapy (EST) and transcutaneous electrical neuromuscular stimulation (TENS), a modality of EST, have become widely applied, accepted and effective methods for the treatment of musculoskeletal and other pain conditions. According to the rising number of permanent pacemaker (PM) wearers the number of potential candidates for EST with concomitant device implantation is growing. Contradictory recommendations exist regarding the application of EST or TENS on PM wearers.

AIM

The study was carried out to evaluate the impact of EST on PM function.

METHODS

A full size model mimicking the electrical characteristics of the human body was used to evaluate the application of EST on permanent PM devices. Various configurations with respect to energy modality, position of the stimulation electrodes and PM device models were evaluated. Intracardiac PM electrogram tracings (iEGM) were analyzed for the interference of EST with PM function.

RESULTS

Unilateral EST application did not cause interference with PM function in any of the configurations (0%; n = 700). On the contrary, bilateral stimulation (350 configurations in total) caused either ventricular inhibition or switch to V00 back-up pacing due to electrical interference in 165 cases (47.1%) depending on the applied stimulation parameters.

CONCLUSION

The use of EST potentially interferes with PM therapy, especially if the electrodes are positioned bilaterally; however, unilateral EST application appeared to be safe in all tested configurations.

Sacral Neuromodulation in Patients With a Cardiac Pacemaker

The objective of this study was to describe our experience using sacral neuromodulation to treat urinary urgency, frequency, urge incontinence, and chronic urinary retention in patients with cardiac pacemakers. With the increasingly widespread use of InterStim for bladder function restoration, we are seeing more complex patients with multiple comorbidities, including cardiac conditions. Herein, we report 3 cases of individuals with cardiac pacemakers who underwent InterStim implantation to treat urinary conditions. This study is a case series of 3 patients with cardiac pacemakers who underwent sacral neuromodulation to treat refractory voiding dysfunction. The initial patient screening for InterStim therapy involved percutaneous nerve evaluation (PNE), in which a temporary untined lead wire was placed through the S3 foramen. Patients who did not respond to PNE proceeded to a staged implant. All patients in this study had a greater than 50% improvement of their urinary symptoms during the initial trial and underwent placement of the InterStim implantable pulse generator (IPG). Postoperative programming was done under electrocardiogram monitoring by a cardiologist. No interference was observed between the Inter-Stim IPG and the cardiac pacemaker. In this group of patients, sacral neuromodulation in the presence of a cardiac pacemaker appears to have been safe.

Assessment of Electromagnetic Interference with Active Cardiovascular Implantable Electronic Devices (CIEDs) Caused by the Qi A13 Design Wireless Charging Board

Electromagnetic interference is a concern for people wearing cardiovascular implantable electronic devices (CIEDs). The aim of this study was to assess the electromagnetic compatibility between CIEDs and the magnetic field of a common wireless charging technology. To do so the voltage induced in CIEDs by Qi A13 design magnetic fields were measured and compared with the performance limits set by ISO 14117. In order to carry this out a measuring circuit was developed which can be connected with unipolar or bipolar pacemaker leads. The measuring system was positioned at the four most common implantation sites in a torso phantom filled with physiological saline solution. The phantom was exposed by using Helmholtz coils from 5 µT to 27 µT with 111 kHz sine-bursts or by using a Qi A13 design wireless charging board (Qi-A13-Board) in two operating modes “power transfer” and “pinging”. With the Helmholtz coils the lowest magnetic flux density at which the performance limit was exceeded is 11 µT. With the Qi-A13-Board in power transfer mode 10.8% and in pinging mode 45.7% (2.2% at 10 cm distance) of the performance limit were reached at maximum. In neither of the scrutinized cases, did the voltage induced by the Qi-A13-Board exceed the performance limits.

Pacing and sensing interference by air bubble surrounding the non-extended helix of intact active fixation lead

BACKGROUND

Active fixation pacing leads with silicon cylinder tips have been used for their safety and flexibility. Measurement of baseline sensing/pacing characteristics before fixation of helix helps to identify the optimal pacing site, but we encountered difficulties in making these measurements despite multiple attempts with the model LPA 1200M lead. To identify the cause and overcome this complication, we compared 4 different retractable active fixation lead models, which enabled baseline sensing/pacing measurements before extension of helix. METHODS AND RESULTS: We immersed 4 different lead tips and rings in a 0.18% saline solution, and measured the lead impedance before and after flushing of air bubble visible inside the lead tip. Before evacuation of the air bubble, the impedance of the model LPA 1200M lead was >4,000 Ω in 8 out of 10 measurements, although that of the other leads was within the measurable range. After evacuation of the air bubble, the lead impedance returned to within the measurable range. There was no prominent change in the impedance of the metal cylinder tip lead.

CONCLUSIONS

Air bubbles may interfere with the measurement of baseline sensing/pacing characteristics before active fixation of pacing leads with cylindrical silicon tips. In the case of high impedance beyond the measurable range before extension of helix, the measurement should be repeated after fixation into the myocardium before suspecting lead dysfunction.

[Partial electrical reset of CT irradiation on implantable cardiac devices: relationship between reset and tube voltage, tube current, and rotation time]

The aim of this study was to investigate the relationship between partial electrical reset (PER) and CT scan parameters (tube voltage, tube current, rotation time, and product of tube current and rotation time in mAs). A cardiac resynchronization therapy pacemaker (Insync 8040, Medtronic Inc., Tokyo) and 320 area detector CT scanner (Aquilion ONE, Toshiba medical systems, Otawara, Japan) with volume scan were used. The pacemaker was put in DDD mode. The PERs were interpreted using both the programmer's wave forms and error messages. The exposure was repeated 5 times per CT setting. The pacemaker was placed on the anterior wall and upper side of a chest phantom. Each CT scan was performed using the following parameters: tube voltage of 80, 100, 120, and 135 kV; tube current of 50-550 mA; and rotation time of 0.35-1.5 s. PERs were observed at 100, 120, and 135 kV, and more PERs were observed as the tube voltage increased. The PER tube current decreased as the rotation time was increased. In contrast, the PER tube current and rotation time product (mAs) increased as the rotation time was increased. More specifically, the radiation dose rate was the affected factor of the PERs. To avoid PER of pacemakers, CT scan parameters with lower radiation dose rates (low rather than high tube current and rotational time) is recommended. In conclusion, our results will help with CT scans of patients who have implantable cardiac devices (included pacemakers and cardioverter defibrillators).

X-ray radiation causes electromagnetic interference in implantable cardiac pacemakers

BACKGROUND

X-rays are not thought to cause electromagnetic interference (EMI) in implantable cardiac pacemakers. However, x-ray radiation during computed tomography (CT) scanning has been reported to cause EMI in some implantable cardiac pacemakers. The objectives of this study were to identify the location within the pacemakers where x-ray radiation causes EMI and to investigate the association of EMI with the x-ray radiation conditions.

METHODS

We verified the location where x-ray radiation caused EMI using a CT scanner and conventional radiographic x-ray equipment. An inhibition test and an asynchronous test were performed using five types of implantable cardiac pacemakers.

RESULTS

X-ray radiation inhibited the pacing pulses of four types of implantable cardiac pacemakers when the body of each implantable cardiac pacemaker, containing a complementary metal-oxide semiconductor (CMOS), was scanned using a CT scanner. We confirmed that x-ray-induced EMI depends on the x-ray radiation conditions, that is, the tube voltage, tube current, x-ray dose, and direction of x-ray radiation, as well as the sensing thresholds of the implantable cardiac pacemakers.

CONCLUSIONS

X-ray radiation caused EMI in some implantable cardiac pacemakers, probably because the CMOS component was irradiated. The occurrence of EMI depended on the pacemaker model, sensing threshold of the pacemaker, and x-ray radiation conditions.

SAR evaluations of mobile phone close to a pacemaker implanted in human body

Recently, electromagnetic interference (EMI) of an implanted pacemaker with a mobile phone was largely investigated. As for the pacemaker, the Japan National Authorities have recommended to keep the mobile phone in safe distance from the cardiac pacemaker. Meanwhile, evaluation of the interaction between the electromagnetic (EM) wave and human body was in progress. Therefore, the absorption of EM energy to the human body especially around the pacemaker, where the mobile phone was in a chest pocket of the pacemaker holder, was thoroughly evaluated. We provided the calculation of specific absorption rate (SAR) distributions around the pacemaker model that implanted into a rectangular parallelepiped torso model, when a mobile phone model is placed in the vicinity. In addition, the SAR was also experimentally performed to validate the such numerical calculations. We confirmed that SAR distributions could be estimated from the presence or absence of pacemaker model. Moreover, the measurement results of the SAR distribution suited to the calculation, thus its validation was achieved.

Unipolar cardiac pacemakers in electromagnetic fields of high voltage overhead lines

Experimental studies have shown that both electric and magnetic extremely low frequency fields are able to disturb a cardiac pacemaker (CPM) at certain field strengths. However, the simultaneous influence of multiphase electric and magnetic fields beneath high voltage overhead lines (HVOLs) has not yet been investigated. Therefore, the distribution of the electric and the magnetic field as well as the phase angle between both components for an exemplary HVOL was numerically calculated. The calculations show that the phase difference of the capacitive and the inductive induced voltage on the input of an implanted cardiac pacemaker is position-dependent. Based on these and our earlier results a worst-case-scenario for two virtual patients beneath an exemplary HVOL was derived. It turned out that although the interference of CPMs by the electromagnetic fields (EMFs) of HVOLs cannot be ruled out, the life-threatening interference condition 'inhibition by EMF' is unlikely. Due to various factors depending on technical parameters and the individual patient a definite answer about the disturbance of an implanted CPM beneath HVOLs can be given by studies with real CPM patients only.

[Effect of diagnostic X-rays on implantable cardiac pacemakers and implantable cardioverter defibrillators, and its management]

The effects of diagnostic X-rays on implantable cardiac pacemakers and implantable cardioverter defibrillators (ICDs) were investigated. A total of 33 pacemakers from six manufacturers and nine ICDs from four manufacturers were irradiated using several X-ray units (plain X-ray diagnostic unit, under-table system fluoroscopy unit, over-table system fluoroscopy unit, biplane cardiac digital angiography unit, DSA unit and cone-beam CT unit). No systematic reset phenomena were observed in any pacemakers and ICDs under the X-ray irradiation. Nevertheless, over-sensing associated with the lack of a few pulses was observed in three of 33 pacemakers under radiation exposure. It has been proven that diagnostic X-rays might affect pacemaker function. Since the duration of the over-sensing under the radiation was very short and included transient episodes, this sensing failure, therefore, induced by radiation exposure would not affect the health of pacemaker recipients. ICDs were not affected by radiation exposure at a clinical dose. It is recommended that caution be exercised in direct irradiation to the pacemaker. Using a copper sheet of 2.0 mm thickness or more prevented over-sensing of pacemakers in the present study, especially when serial X-ray exposures were used with an over-table fluoroscopy system or cone-beam CT unit.

[Experimental study of the influence on pacemakers of X-rays from angiocardiography equipment]

We performed an experimental study of the influence on pacemakers (PM) of X-rays from the angiocardiography equipment. (1) We used one PM of DDD mode in this study. (2) The PM was irradiated under two exposure levels: one the standard dose and the other the maximum dose in the angiocardiography study situation. (3) We set the pacing lead wires to the bilateral atria and ventricles in Irnich's human body model. (4) We set two irradiation fields, one with a lead block on the PM and the other without the lead block. The result showed that when the PM was included in the irradiation field and the exposure level was of the maximum dose, the influence of irradiation on the PM was that of level 2 as classified by a research report by the Ministry of Internal Affairs and Communications. The absorbed dose of the PM was 93.4 mGy under these conditions. We confirmed that radiation dose does not affect a pacemaker with pacing lead wire. However, it acts on the generator of the PM owing to the direct photoelectric effect. When there were many dose rates (or total radiation dose), an obstacle occurred.

Sacral nerve neuromodulation in patients with cardiac pacemakers

OBJECTIVE

The objective of the study was to describe our experience using sacral nerve neuromodulation for urinary urgency, frequency, and urge incontinence in patients with cardiac pacemakers.

STUDY DESIGN

The study was a case series of 3 patients with cardiac pacemakers who underwent sacral nerve stimulation for refractory urgency, frequency, and urge incontinence.

RESULTS

Each patient underwent placement of an InterStim lead wire in the S3 foramen. Intraoperative cardiac monitoring revealed no evidence of cross-interference, even at maximum stimulation. Postoperative telemetry for 24 hours did not reveal any interference from the sacral nerve stimulator. All patients had a greater than 50% reduction in incontinence episodes during their test trial and underwent placement of the InterStim implantable pulse generator (IPG). Intraoperative and postoperative IPG programming was done with cardiac monitoring; no interaction was detectable.

CONCLUSION

Sacral nerve stimulation appears to be safe in the presence of a cardiac pacemaker.

Do electrical stun guns (TASER-X26) affect the functional integrity of implantable pacemakers and defibrillators?

AIMS

High voltage electric current can adversely affect pacemakers (PM) and implantable cardioverter-defibrillator (ICD). The standard shock from an electrical stun gun (TASER- X26, TASER International, Scottsdale, AZ) consists of a 5-s long application of high voltage, low current pulses at 19 pulses per second. Its effect on the functional integrity of PM and ICDs is unknown.

METHODS AND RESULTS

We tested the functional integrity of nine PMs and seven ICDs in a swine model after a standard stun gun shock. A transvenous, dual coil, bi-polar ICD lead (St Jude-SP01) and a PM lead were placed in the right ventricular (RV) apex and connected to pulse generators buried in the pre-pectoral pocket. The two darts were placed at the sternal notch (SN) and apex of the heart bracketing the device pocket. Standard neuromuscular incapacitating (NMI) discharges were delivered. Functional parameters of the devices and leads were checked before and after the shocks. The mean pacing thresholds, sensing thresholds, pacing impedances, and defibrillation coil impedances of the ICD lead were similar before and after the shocks. Similarly, pacing thresholds, sensing thresholds, and impedances of the PM lead were not significantly different before and after the shocks. No significant change was noted in battery voltage and projected longevity. Implantable cardioverter-defibrillator generators detected the NMI impulses at a mean cycle length of 176 +/- 20 ms with detection to charge time of 5.9 +/- 1.5 s. Shock delivery was aborted in all tests as tachycardia detection abruptly terminated at the end of the 5 s NMI application. None of the devices exhibited power on reset (POR), elective replacement indicator (ERI), or noise mode behaviour after the shock.

CONCLUSION

Pacemakers and ICD generators and leads functions were not affected by the tested standard 5 s stun gun shocks.

Wavelet-Based Event Detection in Implantable Cardiac Rhythm Management Devices

This paper presents a novel event detector for implantable devices. The algorithm is based on a signal model which describes an event as a linear combination of basis functions. The linear combination involves two fundamental electrogram waveforms represented at different time scales. An efficient, low-complexity detector is developed using the dyadic wavelet transform with integer filter coefficients, and a generalized likelihood ratio test. The results show that reliable detection is obtained at an intermediate signal-to-noise ratio (SNR = 25 dB) for various common noise sources. In terms of probabilities of missed events and false alarms, an over-all performance of 0.7% and 0.1%, respectively, was achieved on electrograms corrupted by the different noise types at an intermediate SNR.

Does High-Power Computed Tomography Scanning Equipment Affect the Operation of Pacemakers?

BACKGROUND

Computed tomography (CT) is widely used in clinical practice, but there has not been a detailed report of its effect on the functioning of pacemakers.

METHODS AND RESULTS

During CT, ECGs were recorded in 11 patients with pacemakers and the electromagnetic field in the CT room was also measured. The effect of CT on a pacemaker was also investigated in a human body model with and without shielding by rubber or lead. Transient malfunctions of pacemakers during CT occurred in 6 of 11 patients. The model showed that malfunctioning of the pacemaker was induced by CT scanning and this was prevented by lead but not by rubber. The alternating electrical field was 150 V/m on the CT scanning line, which was lower than the level influencing pacemaker functions. The alternating magnetic field was 15 muT on the CT scanning line, which was also lower than the level influencing pacemaker functions.

CONCLUSIONS

Malfunctions of the pacemaker during CT may be caused by diagnostic radiant rays and although they are transient, the possibility of lethal arrhythmia cannot be ignored.

Influence of electromagnetic interference on implanted cardiac arrhythmia devices in and around a magnetically levitated linear motor car

This study was designed to determine the susceptibility of implanted cardiac arrhythmia devices to electromagnetic interference in and around a magnetically levitated linear motor car [High-Speed Surface Transport (HSST)]. During the study, cardiac devices were connected to a phantom model that had similar characteristics to the human body. Three pacemakers from three manufacturers and one implantable cardioverter-defibrillator (ICD) were evaluated in and around the magnetically levitated vehicle. The system is based on a normal conductive system levitated by the attractive force of magnets and propelled by a linear induction motor without wheels. The magnetic field strength at 40 cm from the vehicle in the nonlevitating state was 0.12 mT and that during levitation was 0.20 mT. The magnetic and electric field strengths on a seat close to the variable voltage/variable frequency inverter while the vehicle was moving and at rest were 0.13 mT, 2.95 V/m and 0.04 mT, 0.36 V/m, respectively. Data recorded on a seat close to the reactor while the vehicle was moving and at rest were 0.09 mT, 2.45 V/m and 0.05 mT, 1.46 V/m, respectively. Measured magnetic and electric field strengths both inside and outside the linear motor car were too low to result in device inactivation. No sensing, pacing, or arrhythmic interactions were noted with any pacemaker or ICD programmed in either bipolar and unipolar configurations. In conclusion, our data suggest that a permanent programming change or a device failure is unlikely to occur and that the linear motor car system is probably safe for patients with one of the four implanted cardiac arrhythmia devices used in this study under the conditions tested.

Electromagnetic Interference of Implantable Unipolar Cardiac Pacemakers by an Induction Oven

Induction ovens have been reported to exert electromagnetic interference on implanted cardiac pacemakers. In an attempt to quantitatively investigate the electromagnetic interference caused by an induction oven on implantable unipolar cardiac pacemakers, we measured the distribution profile of the magnetic field intensity, both with and without a pan on the induction oven. We also performed the inhibition test and asynchronous test using four kinds of pacemakers housed in the standardized Irnich human body model, and measured the maximal distance from the induction oven up to which the interference occurred. In the pan-detection mode of the oven in the absence of a pan, the distribution profile of the magnetic field intensity peaked at the center of the cooking plate, and during induction heating of a pan placed on the induction oven, it was the largest at the circular top-edge of the pan. Pacemaker pulses were inhibited by the induction oven, or generated by the reversion mechanism. The maximal interference distance from the oven was 34 cm for one of the pacemakers. Thus, the safe distance from an induction oven of a patient with an implanted cardiac pacemaker is considered to be 50 cm or more. In conclusion, in the pan-detection mode of the oven in the absence of a pan, the distribution profile of the magnetic field intensity peaked at the center of the cooking plate, and during the induction heating of a pan placed on the oven, it peaked at the circular edge of the pan. The induction oven asynchronized or generated pulses in implantable unipolar cardiac pacemakers up to a maximal distance of 34 cm from the induction oven.

Feasibility of Spinal Cord Stimulation in Angina Pectoris in Patients with Chronic Pacemaker Treatment for Cardiac Arrhythmias

Spinal cord stimulation (SCS) has been used since 1985 as additional symptom-relieving treatment for patients with severe angina pectoris despite optimal conventional medical and invasive treatment. SCS has antiischemic effects and is safe and effective in long-term use. Several patients with coronary artery disease also suffer from disorders that necessitate the use of a cardiac permanent pacemaker (PPM). The combination of SCS and PPM has previously been considered hazardous because of possible false inhibition of the PPM. To assess if thoracic SCS and PPM can be safely combined in patients with refractory angina pectoris, 18 patients treated with both SCS and PPM were tested. The PPM settings were temporarily modified to increase the probability of interference, while the SCS intensity (used in bipolar mode) was increased to the maximum level tolerated by the patient. Any sign of inhibition of the ventricular pacing was recorded by continuous ECG monitoring. With the aid of a questionnaire, symptoms of interference during long-term treatment were evaluated. No patient had signs of inhibition during the tests. Reprogramming of the pacemaker because of the test results was not needed in any of the patients. The long-term follow-up data revealed no serious events. This study indicates that bipolar SCS and PPM can be safely combined in patients with refractory angina pectoris. However, individual testing is mandatory to ascertain safety in each patient. A testing procedure for patients in need of SCS and PPM is suggested in this article.

Influence of mobile magnetic resonance imaging on implanted pacemakers

PURPOSE

Mobile magnetic resonance imaging (MRI) systems will be widely used in Japan. When traveling, mobile MRI generate alternating electromagnetic waves which may cause electromagnetic interference (EMI). This study was designed to determine whether this may influence the function of implanted pacemakers (PM).

METHODS AND RESULTS

The influence of the static magnetic fields was tested in the first method using a PM-human model (Phantom). Magnetic force was simultaneously measured. The PM was switched to the magnet mode within 90 cm from the vehicle, where the magnetic force was = 2 mT. In the second method, six phantoms were placed on the side of the road, facing in three different directions in X-Y-Z axis orientations, at 1.3 m and 2.0 m above the ground. The mobile MRI passed by at a distance of 1 m from the phantoms at the speed of 20 or 40 km/h. In these experiments, magnet mode switch of the PM was observed for 2 seconds when the vehicle passed close to the phantoms, though no electrical noise was recorded.

CONCLUSION

Mobile MRI vehicles can switch a PM to magnet mode when the distance between patient and vehicle is < 90 cm, regardless of whether the vehicle is moving or at a stop. Patients with implanted PM should not approach within < 1 m of a mobile MRI. No other EMI-induced PM dysfunction was detected.

Pacemaker interference by magnetic fields at power line frequencies

Human exposure to external 50/60-Hz electric and magnetic fields induces electric fields within the body. These induced fields can cause interference with implanted pacemakers. In the case of exposure to magnetic fields, the pacemaker leads are subject to induced electromotive forces, with current return paths being provided by the conducting body tissues. Modern computing resources used in conjunction with millimeter-scale human body conductivity models make numerical modeling a viable technique for examining any such interference. In this paper, an existing well-verified scalar-potential finite-difference frequency-domain code is modified to handle thin conducting wires embedded in the body. The effects of each wire can be included numerically by a simple modification to the existing code. Results are computed for two pacemaker lead insertion paths, terminating at either atrial or ventricular electrodes in the heart. Computations are performed for three orthogonal 60-Hz magnetic field orientations. Comparison with simplified estimates from Faraday's law applied directly to extracorporeal loops representing unipolar leads underscores problems associated with this simplified approach. Numerically estimated electromagnetic interference (EMI) levels under the worst case scenarios are about 40 microT for atrial electrodes, and 140 microT for ventricular electrodes. These methods could also be applied to studying EMI with other implanted devices such as cardiac defibrillators.

The interference threshold of cardiac pacemakers in electric 50 Hz fields

The aim of the study was to determine a 'worst-case' and a 'real-case' interference threshold for implanted cardiac pace-makers (CPM) in electric 50 Hz fields as they appear in high-voltage plants, e.g. beneath high voltage overhead lines. For this purpose the resulting electrical potential distribution within the thorax area of volunteers from an external homogeneous electrical 50 Hz field was measured. Different factors such as different body geometries as well as inspiration and expiration of the lung were considered. Measurements showed that 1 per 1 kV m(-1) unimpaired electrical field strength (RMS) an interference voltage of about 180 microVpp as real-case value an 400 microVpp as worst-case value would occur at the input of a unipolar ventricularly controlled, left pectorally implanted cardiac pacemaker. Therefore, it is possible under worst-case conditions but unlikely under practice-relevant conditions that an implanted cardiac pacemaker is disturbed by present electric 50 Hz fields beneath high voltage overhead lines.

Pacemaker interference and low-frequency electric induction in humans by external fields and electrodes

The possibility of interference by low-frequency external electric fields with cardiac pacemakers is a matter of practical concern. For pragmatic reasons, experimental investigations into such interference have used contact electrode current sources. However, the applicability to the external electric field problem remains unclear. The recent development of anatomically based electromagnetic models of the human body, together with progress in computational electromagnetics, enable the use of numerical modeling to quantify the relationship between external field and contact electrode excitation. This paper presents a comparison between the computed fields induced in a 3.6-mm-resolution conductivity model of the human body by an external electric field and by several electrode source configurations involving the feet and either the head or shoulders. The application to cardiac pacemaker interference is also indicated.

Study of interactions between permanent pacemakers and electronic antitheft surveillance systems

Interference of electronic antitheft systems (EASs) with pacemakers has been an object of controversy. This study was performed in 204 patients followed by our pacemaker surveillance center. The data from a total of 408-patient exposures to the EAS were analyzed. The device tested consisted of 129 DDD, 71 VVI, and 4 VDD pacemakers from seven manufacturers. The EAS studied consisted of an "acoustomagnetic" system that emits an intermittent 58-kHz signal, and a magnetic audio frequency system that emits a continuous 73-Hz signal. Complete interrogation of the pacemakers was performed before and after the consecutive exposure of the patients to both EASs. Electrocardiograms were recorded while the patients were exposed to the magnetic fields of each EAS for up to 30 seconds. One or more EAS interferences occurred in 17% of patients. EAS was observed in 26 (20%) of 129 patients with DDD, 7 (10%) of 71 patients with VVI, and 2 (50%) of 4 patients with VDD pacemakers. Over twice as many instances of EAS interference were observed with the "acoustomagnetic" system as were with the magnetic audio frequency system. Among pacemakers programmed in the DDD mode, a considerably greater prevalence of interference was observed at the atrial versus ventricular level, despite the same programmed sensing polarity in both chambers in all but one case. Sensing anomalies were the most common EAS induced disturbance, and typically lasted for the duration of exposure. In a few instances of pacing inhibition, the phenomenon was limited to 1 cycle at the onset of EAS exposure. No changes occurred in the programming of the pacemakers, and a single patient experienced palpitation during EAS induced rapid pacing. During exposure to EAS mimicking the normal use of the systems, interference with a variety of pacemakers was relatively common. However, the anomalies observed were transient and the cause of no symptom or device reprogramming. Patients should be advised to not stand unnecessarily in the close proximity of EASs.

Interference with cardiac pacing

Most exposures to electromagnetic interference are transient and pose no threat to patients with pacemakers and implantable cardioverter defibrillators. Prolonged exposure may be catastrophic in pacemaker dependent patients. New technologies (wireless phones, electronic antitheft surveillance) are safe if proper precautions are takes. Radiofrequency ablation requires concomitant temporary pacing. MR imaging remains contraindicated in patients with these devices until further study is undertaken.

Concerns about sources of electromagnetic interference in patients with pacemakers

Electromagnetic noise is rapidly increasing in our environment so electromagnetic interference (EMI) with pacemakers (PM) may become a more important problem despite technological improvements in PM. The aim of this study was to evaluate the kinds of EMI which affect the quality of life of PM patients. The participants (1,942 Japanese Association for Pacemaker Patients: Pacemaker-Tomonokai) were asked to respond to a questionnaire about their major EMI troubles, and 1,567 patients (80.7%) responded by mail. The main concerns were from mobile telephones (MT) (39%), magnetic resonance imaging (MRI) (17%), electronic kitchen appliances, automobile engines and high voltage power lines. If possible, PM implantation sites should be carefully selected not only according to the physician's convenience but also considering information on each patient's habits and physical limitations.

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.

Hospital pager systems may cause interference with pacemaker telemetry

Electromagnetic interference (EMI) is a well-known cause of pacemaker dysfunction. The communication between pacemakers and programmers, enabled by telemetry, is also susceptible to EMI. We have observed that hospital pager systems have the potential to interfere with pacemaker telemetry. Measurements in our pacemaker clinic and in a technical laboratory have shown that inductive pager systems may disturb telemetry in the form of inaccurate battery voltage, current and impedance measurements, disturbances in intracardiac electrogram tracings, or total interruption of telemetric communications. The reason for EMI was an overlap of carrier frequencies of some pacemaker programmers (32-37 kHz) with those of our inductive pager system (36.11 kHz). Radiofrequency pager systems using higher frequencies (in MHZ range) are unlikely to cause such interference. Awareness of this interference potential may have practical implications in choosing the carrier frequencies of inductive hospital pager systems, as well as pacemaker programmers, and in planning the location of pacemaker clinics.

Study of Pacemaker and Implantable Cardioverter Defibrillator Triggering by Electronic Article Surveillance Devices (SPICED TEAS)

The magnetic fields emitted by electronic article surveillance (EAS) systems (shoplifting gates) are a source of interference for implanted medical devices. In the Study of Pacemaker and Implantable Cardioverter Defibrillator Triggering by Electronic Article Surveillance Devices (SPICED TEAS), 25 adult volunteers with ICDs and 50 with pacemakers were exposed to the fields of six different EAS systems. These EAS systems used three modes of operation: magnetic audio frequency, swept radiofrequency, and acoustomagnetic technology. No ICD exhibited interference mimicking sensing of tachyarrhythmias with any EAS system. Pacemakers interacted variably, depending on the type of EAS system. Swept radiofrequency systems produced no interaction with any implanted medical device. One magnetic audio frequency system interacted with 2 of 50 pacemakers. The acoustomagnetic system interacted with 48 of 50 pacemakers. Interactions included asynchronous pacing, atrial oversensing (producing "EAS induced tachycardia" in the ventricle), ventricular oversensing (with pacemaker inhibition), and paced beats resulting from the direct induction of current in the pacemaker ("EAS induced pacing"). These interactions produced symptoms in some patients (palpitations, presyncope) only while patients were in the EAS field. No pacemaker was reprogrammed. We conclude that high energy, pulsed low frequency EAS systems such as acoustomagnetic systems interfere with most pacemakers. Pacemaker patients should be advised to minimize exposure to the fields of such systems to prevent the possibility of serious clinical events.

Interactions between pacemakers and security systems

Electromagnetic fields arising from a variety of different sources have been shown to interfere with normal pacemaker function. This study evaluated the possible interactions between two modern security systems and different pacemaker types. Fifty-three patients (27 single chamber pacemakers, 25 dual chamber pacemakers) have been tested routinely for their pacemaker function. Thirty-eight patients presented with unipolar sensing and 15 with bipolar sensing. The patients were asked to walk through an installed security system, an antitheft device, and electromagnetic access device with different field strengths while a six-channel ECG monitored the patients. The pacemaker systems were first measured in their basic programmed modes, then the intervention frequency was changed to 100/min and, thereafter, the maximum sensitivity without T wave oversensing was added. In the security system with the highest field strength (2,700 mA/m), a pacemaker malfunction could be observed in 13% of the monitored patients. In one case, a pacemaker (VVIR) switched to ventricular safety pacing (VOO mode). In the security system with the lower field strength (1,600 mA/m) we found a pacemaker malfunction in 4% of the tested patients. In the antitheft device (50 mA/m), in the electromagnetic access device (300 mA/m), and in pacemaker systems with bipolar sensing, none of these dysfunctions were observed. Phantom programming as described previously did not occur in any of the systems. Persons who are often in the vicinity of security systems should be equipped with a bipolar pacemaker system. Our findings indicate that patients with pacemakers should avoid contact with security systems.

Efficacy and safety of permanent cardiac DDD pacing with contemporaneous double spinal cord stimulation

Spinal cord stimulation (SCS) is currently used to treat peripheral vascular disease (PVD) and refractory angina pectoris not amenable to revascularization. In a case of contemporaneous SCS implant and permanent cardiac pacemaker (PPM), if multipolar electrodes are used it is possible to avoid any interference between the systems. We describe the case of a patient with a DDD pacemaker, in whom two bipolar SCSs were implanted at different times: one to control refractory angina pectoris and the other for PVD. No interference between the three systems has been observed.

[Does thermotherapy of prostatic hypertrophy interfere with pacemaker function? - First results of a pilot-study]

In 8 patients with implanted pacemaker (3 unipolar, 5 bipolar systems) the risk of interference of a regular pacemaker function and an energy source with a capacity of 110 Watt and a frequency of 434 MHz was investigated. The results show that thermotherapy in patients with prostatic hypertrophy can be used without the risk of interference with regular pacemaker function.

Clinical evaluation of a thin bipolar pacing lead

The main disadvantages of bipolar pacing leads have traditionally been related to their relative thickness and stiffness compared to unipolar leads. In a new "drawn filled tube" plus "coated wire" technology, each conductor strand is composed of MP35N tubing filled with silver core and coated with a thin ETFE polymer insulation material. This and parallel winding of single anode and cathode conductors into a single bifilar coil resulted in a bipolar lead (ThinLine, Intermedics) with a body diameter and flexibility similar to unipolar leads. The lead is tined, polyurethane, with the cathode and the anode made of iridium-oxide-coated titanium (IROX). The slotted 8-mm2 cathode tip is coated with polyethylene glycol, a blood soluble material. We present the clinical evaluation results from four pacemaker clinics, where 47 leads (23 atrial-J model 432-04 and 24 ventricular model 430-10) were implanted in 25 patients and followed for up to 2 years. The lead handling characteristics were found to be very satisfactory. Electrical parameters of the leads were measured at implant and noninvasively on postoperative days 1, 2, 21, 42, and months 3, 6, 12, and 24. Mean chronic pulse width thresholds at 2.5 V were 0.14 +/- 0.05 ms in the atrium and 0.10 +/- 0.02 ms in the ventricle, pacing impedances 443 +/- 104 omega and 520 +/- 241 omega, while median electrogram amplitudes were > or = 3.5 mV and > or = 7 mV, respectively. Pacing impedances and thresholds were found to be slightly but statistically significantly higher in unipolar than in bipolar configuration--the findings are explainable by the lead construction. One of 47 leads failed 3 weeks after implant; the conductors were short circuited due to an error during the manufacturing process. We conclude that the new lead thus far has demonstrated appropriate mechanical and electrical characteristics.

The safety of digital mobile cellular telephones with minute ventilation rate adaptive pacemakers

In vitro tests suggest that rate adaptive pacemakers using changes in transthoracic impedance to vary pacing rate may be affected by digital mobile telephones. Electromagnetic fields generated by digital mobile telephones (Global System for Mobile [GSM]) represent a potential source of electromagnetic interference (EMI) for the Telectronics META rate adaptive pacemakers, which use transthoracic impedance as a sensor to determine changes in minute ventilation. Sixteen implanted Telectronics META pulse generators were exposed to 25-W simulated GSM transmissions (900-MHz carrier pulsed at 2, 8, and 217 Hz with a pulse width of 0.6 ms) and the antenna of a 2-W digital mobile telephone (900-MHz, 217-Hz pulse, 0.6-ms pulse width). The 12 dual and four single chamber devices were programmed to maximum sensitivity and assessed in unipolar and bipolar settings and rate adaptive and nonrate adaptive modes. In all cases of EMI, testing was repeated at lower, more routinely set bipolar sensitivity levels. At maximum sensitivity, 11 of 16 devices displayed no evidence of EMI. Brief ventricular triggering occurred in 2, a brief pause in 1, a combination of both in 1, and a brief episode of pacemaker-mediated tachycardia in 1. With pulse generators programmed to more routine sensitivities, only one device displayed rare single beat ventricular triggering. No changes in minute ventilation rate adaptive pacing were observed. At maximum unipolar sensitivities, the META series of rate adaptive pacemakers are resistant to clinically important EMI from digital mobile telephones. Set at routine sensitivities, these devices perform reliably in the presence of digital mobile telephones.

Intermittent pacemaker dysfunction caused by digital mobile telephones

OBJECTIVES

This study was designed to evaluate possible interactions between digital mobile telephones and implanted pacemakers.

BACKGROUND

Electromagnetic fields may interfere with normal pacemaker function. Development of bipolar sensing leads and modern noise filtering techniques have lessened this problem. However, it remains unclear whether these features also protect from high frequency noise arising from digital cellular phones.

METHODS

In 39 patients with an implanted pacemaker (14 dual-chamber [DDD], 8 atrial-synchronized ventricular-inhibited [VDD(R)] and 17 ventricular-inhibited [VVI(R)] pacemakers), four mobile phones with different levels of power output (2 and 8 W) were tested in the standby, dialing and operating mode. During continuous electrocardiographic monitoring, 672 tests were performed in each mode with the phones positioned over the pulse generator, the atrial and the ventricular electrode tip. The tests were carried out at different sensitivity settings and, where possible, in the unipolar and bipolar pacing modes as well.

RESULTS

In 7 (18%) of 39 patients, a reproducible interference was induced during 26 (3.9%) of 672 tests with the operating phones in close proximity (<10 cm) to the pacemaker. In 22 dual-chamber (14 DDD, 8 VDD) pacemakers, atrial triggering occurred in 7 (2.8%) of 248 and ventricular inhibition in 5 (2.8%) of 176 tests. In 17 VVI(R) systems, pacemaker inhibition was induced in 14 (5.6%) of 248 tests. Interference was more likely to occur at higher power output of the phone and at maximal sensitivity of the pacemakers (maximal vs. nominal sensitivity, 6% vs. 1.8% positive test results, p = 0.009). When the bipolar and unipolar pacing modes were compared in the same patients, ventricular inhibition was induced only in the unipolar mode (12.5% positive test results, p = 0.0003).

CONCLUSION

Digital mobile phones in close proximity to implanted pacemakers may cause intermittent pacemaker dysfunction with inappropriate ventricular tracking and potentially dangerous pacemaker inhibition.

Pacemaker inhibition and asystole in a pacemaker dependent patient

A 17-year-old female with Kearns Sayre syndrome, complete heart block, and an implanted single chamber (VVIR) pacemaker, underwent testing with a GSM cellular phone that was placed directly over the pacemaker site. The pacemaker was immediately inhibited when the phone began to operate. A 6.5-second period of complete heart block with asystole occurred until the phone was switched off.