Electronic Security Systems and Active Implantable Medical Devices

Abstract

How do active implantable medical devices react in the presence of strong magnetic fields in the frequency range between extremely low frequency (ELF) to radiofrequency (RF) as they are emitted by electronic security systems (ESS)? There are three different sorts of ESSs: electronic article surveillance (EAS) devices, metal detector (MDS) devices, and radiofrequency identification (RFID) systems. Common to all is the production of magnetic fields. There is an abundance of literature concerning interference by ESS gates with respect to if there is an influence possible and if such an influence can bear a risk for the AIMD wearers. However, there has been no attempt to study the physical mechanism nor to develop a model of how and under which conditions magnetic fields can influence pacemakers and defibrillators and how they could be disarmed by technological means. It is too often assumed that interference of AIMD with ESS is inevitable. Exogenous signals of similar intensity and rhythm to heart signals can be misinterpreted and, thus, confuse the implant. Important for the interference coupling mechanism is the differentiation between a "unipolar" and a "bipolar" system. With respect to magnetic fields, the left side implanted pacemaker is the most unfavorable case as the lead forms approximately a semicircular area of maximum 225 cm2 into which a voltage can be induced. This assumption yields an interference coupling model that can be expressed by simple mathematics. The worst-case conditions for induced interference voltages are a coupling area of 225 cm2 that is representative for a large human, a homogeneous magnetic field perpendicular to the area formed by the lead, and a unipolar ventricular pacemaker system that is implanted on the left side of the thorax and has the highest interference sensitivity. In bipolar systems the fields must be 17 times larger when compared to a unipolar system to have the same effect. The magnetic field for interfering with ICDs must be 1.7 stronger than that of the most sensitive unipolar pacemaker. The lowest interference thresholds measured over the last 10 years in the low frequency range (16 2/3 Hz-24 kHz) together with thresholds > 24 kHz that were supplied by the CETECOM study are listed. Both sets of data together with the coupling model, allow for judging which fields of ESSs could influence AIMDs. From measurements at gate antennas, it is possible to derive a "maximum allowed field" curve over the whole frequency range, below which no interference will occur. Comparison of data from literature with these maximum allowed fields confirm the correctness of the calculations. Thus, it is possible to predict interference situations in gates if the magnetic field is known. If all future pacemakers were to have the immunity against interference of the better 50% of today's pacemakers, the magnetic field ceiling values could be at least four times higher. The same is true if the ventricular sensitivity is routinely set at 7 mV. Pacemaker manufacturers should consider filter im...

Silk-based resorbable electronic devices for remotely controlled therapy and in vivo infection abatement

“…These devices are designed to operate while embedded in living tissue, which can lead to complications and restrictions on material constituents and form factors (3). Among the primary constraints are resistance to degradation while performing reliably and integration in the biological milieu without inflammatory response or rejection (4).…”

In vitro Assessment of Electromagnetic Interference due to Low-Band RFID reader/writers on Active Implantable Medical Devices

“…However, the EMI caused by low-band RFID reader/writers is assumed to be caused by the alternating magnetic field from the antennas. 11,14) In this case, it is assumed that a ''one turn coil'' is connected between the anode and cathode electrode of the AIMD, since the tissues of the human body are electric conductors. The magnetic flux density through the coil generates an electromotive force between the electrodes of the AIMD.…”

“…EMI exposure to active implantable medical devices (AIMDs) due to the prevalence of wireless communication devices has become a very controversial issue in recent years. [2][3][4][5][6][7][8][9][10][11][12][13][14][15] This is because the number of AIMD users has increased every year due to technological advances in AIMDs and the aging of the population. In Japan, shipments of implantable-cardiac pacemakers and implantable-cardioverter defibrillators (ICDs) rapidly increased from 29,800 devices in fiscal 1996 to 57,000 devices in fiscal 2007.…”

“…8) Based on the results obtained, some EMI prevention guidelines, which define the minimum safe distance, have been published. 9,10) Other EMI sources such as electronic security systems, 11) induction cooking surfaces, 3) and electromagnetic stimulation 12) have also been investigated. Concerning the EMI due to RFID, the Ministry of Internal Affairs and Communications of Japan reported research results to determine the guidelines to prevent the EMI.…”

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

“…1 Clinically, a variety of medical appliances that produce electromagnetic or radiofrequency waves are now used for diagnostic or therapeutic purposes, and precautions or restrictions on their use have been enforced to protect patients with an implanted pacemaker from possible hazards. [2][3][4][5][6] Computed tomography (CT) is widely used in clinical practice, but a detailed report has not been published of the effects of CT scanning on the operation of pacemakers. Although it is commonly believed that CT scanning does not affect the functioning of pacemakers, we have previously reported a transient malfunction of the pacemaker probably caused by over-sensing.…”