A model for determining the induced voltage at the terminals of a pacemaker exposed to a low frequency magnetic field.

This paper presents a method for calculating induced voltage, in vitro, at the terminals of a unipolar pacemaker (PM) subjected to a low frequency magnetic field. We propose a theoretical model which has been experimentally verified by using a homogeneous phantom model placed at the centre of the source generating a homogeneous magnetic field. The levels of the magnetic field used in our experiment are in accordance with the European Directive 2004/40/EC, which sets the occupational electromagnetic field exposure limits. The voltage induced at the terminals of an implanted pacemaker results in the superimposition of two different voltage sources. The first is due to the presence of the loop formed by the PM system and the second is due to the induced currents circulating in the coupling medium. The influence of the induced currents, calculated by the impedance method, is weak compared to the voltage of the loop. The theoretical results obtained agree with the experimental value. Thus, the proposed model can be used to predict the behaviour of a pacemaker subjected to a low frequency magnetic field as well as to those fields within the accepted exposure limits for a patient with a pacemaker.

Calculation of the induced voltage at the terminals of cardiac pacemakers submitted to conducted disturbances.

This paper presents a method of numerical simulation based on the admittance method which allows us to calculate the induced tension at the terminals of a cardiac pacemaker subjected to conducted disturbances. The physical model used for simulation is an experimental test bed that makes it possible to study in vitro the behavior of pacemakers subjected to electromagnetic disturbances. The studied frequencies correspond to domestic and industrial applications of electricity (50 Hz-500 kHz). The experimental tests are carried out with two different single-chamber pacemakers implanted in a tissue-equivalent phantom and correlated to tests performed in air (without the phantom). Results obtained by numerical simulation are in good agreement with experimental values and that allows us to validate the computer model. Numerical results are used to determine the transfer function between the signal source and the signal induced between the distal lead tip and the case of the implanted device.

The behavior of dual-chamber pacemakers exposed to a conducted low-frequency disruptive signal.

This paper presents a study of the behavior of dual-chamber cardiac pacemakers submitted to low-frequency conducted disruptions. The disruptive signal is sinusoidal, operating at 50 Hz, 60 Hz, 10 kHz and 25 kHz. The behavior of the pacemakers is described by statistical data obtained with a telemetry system and by visualization of the pacemaker signal during the application of the interfering signal. The pacemakers were tested in two configurations. The first one consists of direct application of the interfering signal between the pacemaker terminals. In the second, these attempts are completed by in vitro tests using an electromagnetic model which allow us to take into account the interface which constitutes the human body. The pacemaker under test is inserted into a gelatine phantom mimicking the electrical conductivity of tissues. This study allowed us to define the pacemaker detection thresholds for the two test configurations. For the in vitro approach, which constitutes a complementary approach to a realistic implantation situation, oversensing is noticed for 10 kHz and 25 kHz interfering signal frequencies. Detection thresholds vary from a few tens to a few hundreds of mV, depending on the interfering signal frequency, the device and its programmed detection sensitivities.

[Relevance of in vitro studies for the immunity of cardiac implants in an electromagnetic field environment]]. / Intérêt des études in vitro de l'immunité des implants cardiaques en environnement électromagnétique basse fréquence.

The object of this article is to show the contribution of the vitro experimental approach, based on the basic rules of electromagnetic compatibility (EMC), as a complementary tool to the clinical studies. Results can be obtained by a experimental approach in vitro with electromagnetic phantoms associated to a bench of "standard" test to allow a possible comparison between various studies. After describing the protocol developed for the cardiac implants (pacemakers and defibrillators), examples of partial results are presented by way of illustration.

A methodological approach for the characterization of cardiac pacemaker immunity to low frequency interferences: case of 50 Hz, 60 Hz, 10 kHz and 25 kHz led disruptions.

The goal of this work is the implementation of a metrological set up dedicated to the characterization of cardiac pacemakers' immunity at low frequency electromagnetic disruptions. The studied frequencies are 50 Hz, 60 Hz, 10 kHz and 25 kHz. The assessment methodology that is applied is in accord with the electromagnetic compatibility. The tests are carried out on single-chamber pacemakers. The first approach, consisting of the application of the interfering signal directly between the housing and the electrode, enabled us to point out the influence of a preset detection sensitivity on the signal levels induced between the terminal and the pacemaker's housing. These attempts are completed by in vitro tests using an electromagnetic model which allows one to take into account the interface which constitutes the human body, and thus to get closer to a real life situation. The visualization of the pacemaker generated signal illustrates the performance of the pacemaker according to different test configurations. It is an initial approach meant to create a base for the creation of a metrological protocol.

Intracardiac high-frequency catheter ablatherapy: technical aspects.

Arrhythmia and conduction disorders can be treated by intracardiac ablation. The paper presents an original intracardiac catheter ablation method using a high-frequency (HF) electromagnetic power source. A high-frequency signal is emitted through an electrophysiological catheter introduced into the femoral vein and passed along the course of that vein into the heart. To prevent impedance rise, a problem encountered with other techniques, HF signal wave trains are used for half-period impedance match control and, where necessary, automatic impedance adjustment. Fully automated impedance matching combined with frequency-specific catheter design prevents power reflection between load and source. Resulting lesions can be controlled as to location, area and depth. In addition, HF pulses can be released independently of cardiac rhythm. Additional comprehensive animal experimentation is currently going forward.