WO2012013212A1

WO2012013212A1 - Implantable electrode device, in particular for sensing an intracardiac electrogram

Info

Publication number: WO2012013212A1
Application number: PCT/EP2010/005703
Authority: WO
Inventors: Erhard Kisker
Original assignee: Md Start Sa
Priority date: 2010-07-30
Filing date: 2010-09-16
Publication date: 2012-02-02

Abstract

An implantable electrode device is proposed, in particular for sensing an intracardiac electrogram, comprising at least two electrodes for sensing a signal form the surrounding area and comprising a transceiver for sending the signal in a wireless manner, wherein the electrode device is configured to be supplied with energy exclusively by the sensed signal and/or in a wireless manner by means of a time-varying magnetic field.

Description

Implantable Electrode Device, in Particular for Sensing an Intracardiac

Electrogram

The present invention relates to an implantable electrode device or to a system, in particular for capturing an intercardiac electrogram and/or for cardiac pacing, and to a method, wherein an electrical signal is automatically sensed.

In the following description of the invention, the focus is primarily on sensing an intercardiac electrogram. However, the present invention is not restricted to this particular solution, but in general can be applied to sensing other signals, in particular bio-potentials like ECG, EEG, ERG, EMG, and EOG or the like. Furthermore, the signal may correspond to, e.g., a glucose concentration, a phonocardiography signal or a blood pressure. Electrocardiography (ECG) is a method using electrical signals caused by or during the heartbeat. This electrical signals, corresponding to the activity of the heart, can be used for detecting abnormal rhythms of the heart that may be caused by damages of its conductive tissue. Typically, more than two electrodes are placed on the skin of a human to measure potentials or a voltage correspond- ing to the electrical activity of the heart. A more direct and precise way to sense a signal corresponding to the electrical activity of the heart makes use of an implanted electrode close to the signal source, i.e. the heart itself, for sensing a so- called intracardiac electrogram. A system for monitoring and analyzing biosignals is known from EP 1 815 784 Al . Cable-less transducers are used for measurement of e.g. electrocardiograms. The transducers can be placed on or implanted under human skin. The transducers make use of a battery as an energy supply for measuring signals by an electrode or sensor. If the transducers are implanted, changing the battery is prob- lematic. Furthermore, using a battery leads to a size that is not small enough for an application around or inside a heart for sensing intracardiac electrograms.

An implantable pacemaker comprising a programmable sensing circuit for sensing a signal which allows for approximating a surface electrocardiogram is dis- closed in US 2008/0051672 A l . A medical device is implanted in the area of a shoulder and comprises a telemetry module for sending measured data. Pacing electrodes are connected to the medical device using wires or cables, wherein the pacing electrodes can be used for estimating an intercardiac signal as well . Nevertheless, these wires or cables are problematic or disadvantageous, because they run over a length of about 30 cm in the blood circulation system and can thereby cause undesirable or even fatal physical reactions. Furthermore, the risk of failure as a result of the mechanical stressing during body movements is high. In addition, the electrodes can be dislocated by movements of the patient due to the wires or cables.

US 2009/0024180 A l discloses a stimulation system comprising an implantable electrode device. The electrode device is supplied with energy and controlled in an exclusively wireless manner via a time-variable magnetic field generated by an implanted control device. This electrode device is small enough for a place- ment close to or inside a heart, as energy is transmitted in a wireless manner instead of using a battery. Nevertheless, this electrode device is part of a stimulation system and configured for delivery of an electrical impulse only. Thus, it is not suitable for sensing purposes. The object of the present invention is to provide an implantable electrode device, or a system, in particular for capturing an intracardiac electrogram and/or for cardiac pacing, or a method for automatically sensing an electrical signal , wherein a continuous operation and/or a more reliable signal sensing can be provided, and/or periodical surgeries for battery changing can be avoided.

The above mentioned object is achieved by an implantable electrode device according to claim 1 , by a system according to claim 12 or by a method according to claim 17. Advantageous embodiments are subject of the subclaims. According to a first aspect of the present invention, an implantable electrode device is provided, in particular for sensing an intracardiac electrogram. The electrode device comprises at least two electrodes for sensing a signal from the surrounding area. This signal preferably can be an intracardiac potential or voltage, a (bio-) potential as an ECG signal , an EEG signal , an EMG signal or the like. Alternatively or additionally, the implantable electrode device can comprise a sensor, preferably with electrodes, for sensing a signal like a glucose value, blood pressure or the like. The electrode device comprises a transceiver for sending the signal in a wireless manner, preferably a coil and/or an antenna. The electrode device is configured to be supplied with energy exclusively by the sensed signal and/or in a wireless manner by means of a time-varying magnetic field. This means, the implantable electrode device is an at least basically passive device, wherein the energy needed for operation is provided by the signal to be sensed itself and/or the power needed for operation is supplied by means of the time-varying magnetic field.

In the sense of the present invention, the term "magnetic field" preferably covers electro-magnetic fields or waves. Hence, fields, waves or the like with any kind of magnetic component can be a "magnetic field" in the sense of the present invention as well .

A signal sensed by the electrode device is transmitted in a wireless manner and the power is supplied by means of the time-varying magnetic field or the signal itself. Thus, it is advantageous that no wire, cable, lead or the like is needed and, hence, the reliability can be improved significantly. Furthermore, by using a pas- sive topology and/or a wireless power supply, no battery is needed within the electrode device. This is particularly advantageous for a small form factor, because typically the size for a portable and/or wireless sensing device is strictly limited to larger form factors due to the battery needed. Preferably, at least one electrode is connected to the transceiver, in particular via an amplifier for amplifying the signal . The transceiver can be configured for generating the time-varying magnetic field corresponding to the signal . Signals sensed inside or close to a heart are much stronger and, hence, more reliable and robust than voltages or potentials that can be detected via the skin of a body. Nevertheless, amplification can be advantageous for a good signal-to-noise ratio if the signal is transmitted and/or received.

The electrode device can comprise a rectifier for rectifying energy supplied to the electrode device, preferably from outside and/or in a wireless manner. The rectifier in particular comprises semiconductor switches, preferably in a H-bridge configuration. A rectifier in a H-bridge configuration or other full-wave rectifiers have a higher efficiency than half-wave rectifiers. Moreover, rectifiers comprising semiconductor switches are much more efficient compared to common diode-type rectifiers. Thus, using a rectifier with semiconductor switches and/or in a H-bridge contiguration is particularly advantageous for the field of wireless applications the electrode device is typically used for.

An energy buffer can be used in the electrode device and is preferably connected to the output of the rectifier. The energy buffer can smooth the power, e.g. the in- ternal voltage. The energy buffer typically is a capacitor, in particular with a capacitance for a few seconds or minutes of sending the signal in order to keep the form factor as small as possible.

The electrode device can comprise a supervisory component that preferably is adapted for controlling at least one switch and may comprise a timer for a delayed controlling, i .e. switching the switch. Switches in the rectifier can be used either for directing the signal or for directing energy flow inside the electrode device. It is preferred that the supervisory component can be supplied by the rectifier and/or by the energy buffer. The supervisory component can be or com- prise a controller, microcontroller or the like. It can be adapted for receiving and/or decoding information, in particular sent via the time-varying magnetic field . Alternatively or additionally, the supervisory component can be adapted for preprocessing or coding information to be sent by the electrode device, in particular information corresponding to the sensed signal or the sensed signal it- self.

Particularly preferably, the electrode device is adapted for generating electrical impulses and/or for delivering electrical impulses via the electrodes. Hence, the electrode device can have a double functionality. It is possible, that the electrode device can sense a signal , in particular corresponding to the electrical activity of a heart, and, at the same time, the electrode device can be used for pacemaker functionality. As a synergetic effect, the signal sensed by the electrode device can be used for triggering the stimulation or pacemaker functionality. Therefore, it is preferred that the electrode device senses the signal and receives a control signal synchronized to the sensed signal for triggering generation or delivery of the electrical impulse.

A second aspect of the present invention, that can be realized independently as well, relates to a system, in particular for capturing an intracardiac electrogram and/or for cardiac pacing, the system comprising at least one implantable electrode device according to the first aspect of the present invention and/or to any preferred detail mentioned before as well as a receiver adapted for receiving the signal transmitted via a time-varying magnetic field. With respect to the intracar- diac electrography, such a system can comprise at least one electrode device inside or close to the heart as well as a receiver for receiving the signal sensed by the electrode device. The receiver can be placed inside or outside the body and preferably comprises a transmit coil and/or a receive coil and/or a magnetic field sensor, in particular a magnetometer, for receiving the signal . Using the transmit coil can be advantageous as such a coil can be used for both supplying the electrode device with energy and receiving the signal . A receive coil can be much more sensitive to the signal and is cheaper than the magnetic field sensor. The magnetic field sensor or magnetometer is particularly preferred with respect to its high sensitivity.

A control device can be a further part of the system. Preferably, this control device is configured for transmitting energy to the electrode device and/or for controlling the electrode device in a wireless manner by means of the time-varying magnetic field. The receiver and/or the control device can be implanted as well and/or can form a joint constructional unit. An implantable control device and/or receiver enables a short distance to the electrode device leading to a good signal quality and low losses for wireless energy transmission. The receiver and/or the control device can comprise a, preferably rechargeable, battery that may be rechargeable by an inductive coupling method. Thus, a transportable system can be provided, wherein a leadless, wireless and/or cableless electrode device can be used for sensing a signal close to its source and the other component(s) can be used for controlling and/or supplying with energy.

A third aspect of the present invention that can be realized independently as well, relates to a method, wherein an electrical signal, in particular an (intracardiac) ECG and/or an EMG signal, is automatically sensed from a surrounding tissue by an implanted electrode device, wherein the signal is converted into a corresponding time-varying magnetic field, wherein the signal is transmitted to a receiver in a wireless manner, and wherein the signal is converted into an electrical signal by the receiver.

It is preferred that a control device triggers the electrode device in a wireless manner by means of the time-varying magnetic field for generating and/or delivering an electric impulse. Preferably the triggering is synchronized by or to the signal. Furthermore, the electrode device can be supplied with energy by the control device in a wireless manner by means of the time-varying magnetic filed.

It is pointed out, that the inventive method typically is a full-automatic process, wherein a signal is automatically sensed, transmitted, analyzed and/or used for controlling, i.e. for triggering the generation and/or delivery of a pacing electrical impulse. No human and in particular no healthcare professional or the like is needed either for configuring the method or for performing it.

The inventive method provides advantages according to the reliability of sensed signals as these can be covered close to its source. Converting the signal to a corresponding time-varying magnetic filed allows for an advantageous wireless transmission. Moreover, a wireless control of the electrode device and/or wireless energy supply of the electrode device enables a robust assembly. Thus, the error probability can be reduced by omitting wires.

As has already been explained, the implanted electrode device is used in particular for sensing a signal corresponding to the electrical heart activity and/or for a pacemaker functionality. However, the present invention is not restricted to these. Rather, the electrode device can generally sense any type of, preferably electrical, signals, e.g., signals caused by the brain, muscles and nerves. The electrode device even can be used implemented inaccessibly, e.g. for detecting a signal corresponding to the characteristics of a liquid flowing through an inaccessible pipe or the like. The preceding is a simplified summary of the invention to provide an understanding of some aspects of the invention. This summary is neither an extensive nor exhaustive overview of the invention and its various embodiments. It is intended neither to identify key or critical elements of the invention nor to delineate the scope of the invention but to present selected concepts of the invention in a simplified form as an introduction to the more detailed description presented below. As will be appreciated, other embodiments of the invention are possible utilizing, alone or in combination, one or more of the features set forth above or described in detail below.

Further advantages, properties, features and aspects of the present invention are obtained from the claims and from the following description of preferred exemplary embodiments with reference to the drawings.

In the figures:

Fig. 1 is a schematic view of a proposed electrode device;

Fig. 2 is a schematic view of a pulse forming device;

Fig. 3 is a schematic diagram of a magnetization curve of a transceiver of the electrode device;

Fig. 4 is a schematic sectional view of a core element of a transceiver;

Fig. 5 is a schematic view of a rectifier circuit;

Fig. 6 schematic view of a rectifier circuit;

Fig. 7A-7C is a timing diagram for the supervisory component;

Fig. 8 is a schematic view of an amplifier; is a schematic view of a system comprising a receiver and an trode device in the implanted state according to this invention; Fig. 10 is a schematic view of a control unit;

Fig. 1 1 is a schematic diagram of the time profile of a magnetic field and an induced voltage; and

Fig. 12 is a schematic block diagram of a further proposed stimulation system comprising a control device and an electrode device as well as a charging device according to this invention.

In the figures the same reference numerals are used for the same parts or parts of the same type, components and the like, where corresponding or similar advantages and properties are obtained even if a repeated description is omitted.

Fig. 1 is a schematical sectional view of a proposed implantable electrode device 1 which in particular can be used for sensing a signal S, in particular an intracardiac electrogram. However, the present invention is not restricted to this. For example, the electrode device 1 can be used for sensing and/or monitoring biopotentials and/or bio-signals, in particular for ECG, EEG, ERG, EMG and EUG as well as for detecting glucose concentration, blood pressure or phonocardiography signals, wherein the electrodes can be part of an sensor. Furthermore, the electrode device preferably can be used for stimulation purposes like pacing and/or defibrillating as well. Moreover, the electrode device 1 can be used for other purposes and at other locations, in particular in the human or animal body.

The electrode device 1 preferably comprises at least two electrodes 2. It can be constructed without a battery or the like. In the example shown, the electrode device 1 comprises a preferably implantable, waterproof, hermetical sealed, insulated and/or insulating housing 3, wherein the housing 3 preferably incorporates components of the electrode device 1 and the electrodes 2 are preferably integrated in the housing 3, or attached thereon.

The electrode device 1 is very compact and in particular configured substantially rod-shaped or cylindrical. In the example shown, the length of the electrode device 1 is less than 3 cm, preferably less than 2 cm, in particular less than 1 ,5 cm. The diameter is preferably at most 1 cm, preferably less than 8 mm, in particular 5 mm or less. A retaining device can be attached to the electrode device 1, preferably an anchor or a screw which allows the electrode device 1 to be anchored in the heart muscle.

The electrodes 2 are configured for sensing a signal S from the surrounding area, in particular a surrending tissue such as a heart 5 or the like. For operation, the electrode device 1 can be implanted into or close to the heart 5. The signal S can be an electrical potential, a voltage and/or a current, in particular for controlling or related to the heartbeat, that can be sensed by the electrodes 2. Hence, in the example shown, the signal S can be sensed e.g. by measuring a voltage across two or more electrodes 2. The electrode device 1 can comprise more than two electrodes 2 as well. The signal S to be sensed preferably is a EEG signal S or corresponds to it. Nevertheless, the signal S can be another electrical body signal S, e.g. related to muscles, alternatively or additionally.

Although close to or insight the heart 5 the signal S advantageously is much stronger than on the skin, an amplification can be reasonable for sending this signal S. Therefore, an amplifier 6 can be provided and the signal S can be led to the input of amplifier 6, in particular via a closed switch 10. The preferably amplified signal S in the following can drive a transceiver 4 for generating the time- varying magnetic filed, preferably corresponding to the signal S, that can be used for sending, i.e., for transmitting the information sensed by the electrodes 2. The transceiver 4 preferably is or comprises one or more coils 21 for generating a time-variable magnetic filed H. Additionally or alternatively, it is possible that the transceiver 4 comprises or is formed by an antenna or the like.

In particular, if the optional amplifier 6 is omitted, sending the signal S can be performed using the intrinsic energy of the sensed signal S. If an amplifier 6 is used, it is preferred that energy is transmitted to the electrode device 1 in a wireless manner by means of the time-varying magnetic filed H for energy supply. A time-varying magnetic filed H generated outside the electrode device 1 can induce a current into the transceiver 4, in particular if the transceiver 4 comprises a coil 21 as depicted in Fig. 1. The energy supplied in a wireless manner can pref- erably be rectified by a rectifier 7, in particular comprising semiconductor switches 8A to 8D, which later will be described in further detail.

While sending the signal S, a switch 1 1 can be opened such that the signal S is not rectified by rectifier 7 in order to improve the sending performance of the transceiver 4. A further switch 12 may be used to connect one node of the transceiver directly to one of the electrodes 2 and/or to close the current circuit if a two-way rectifier 7 is used, that would possibly block the sending process. As will be described in context of implementations for rectifier 7, switches 1 1 and 12 can be omitted if a rectifier 7 with semiconductor switches is used.

The electrode device 1 preferably comprises an energy buffer 9, in particular a capacitor. The energy buffer 9 can be connected to the output of rectifier 7. Thus, the rectified energy delivered by rectifier 7 can be smoothed by energy buffer 9. It is preferred, that the energy buffer 9 is no battery, accumulator or the like. In particular, it is an energy storing device which is at least basically based on physical effects. Nevertheless, other solutions can be possible. The energy buffer 9 can have a maximum capacity for generation and/or delivery of five electrical impulses or less, preferably for two, in particular for one electrical impulse and/or for transmitting the signal S less than 60 sec, preferably less than 5 sec, in particular 3 sec. or less. In the example shown, the energy buffer 9 preferably has a capacity of less than 500 μ¥, preferably less than 300 μ¥, in particular 200 μ¥ or less. A current induced into the transceiver 4 by magnetic field H, thus, can be rectified by rectifier 7 and stored in energy buffer 9, preferably resulting in a rising voltage across the energy buffer 9. This voltage can be used for supplying, e.g., the amplifier 6. Alternatively or additionally, the energy stored in the energy buffer 9 can be used for supplying a supervisory component 15. The supervisory component 15 preferably comprises or is implemented as at least one controller, microcontroller, processor, any other preferably programmable circuit or the like. For instance, a microcontroller with a low power consumption and/or a sleep mode for energy saving purposes can be used, in particular an Atmel AT tiny 10 or any controller of the tiny series provided by Atmel Cooperation, 2325 Orchard Parkway, San Jose, Ca 95131 .

The supervisory component 15 can be adapted for processing and/or coding the signals S sensed by the electrode device 1 . For example, a signal S sensed by the electrode device 1 or information corresponding to the signals S, to an internal status of the electrode device 1 or of the supervisory component 15 can be coded by the supervisory component 15 and the coded signals S or information can be sent by the electrode device 1 . This can lead to a reduced error probability while transmission is performed.

Alternatively or additionally, the supervisory component 15 can be adapted for processing and/or decoding information, in particular commands received via the time-varying magnetic field H. Hence, it is possible to control the electrode device 1 in an easy and reliable way, e.g. the electrode device 1 can be synchronized or particular information can be requested this way. It is possible to address or control a particular one among several electrode devices 1 , in particular by controlling or addressing and/or selecting one supervisory component 15 in the described manner.

The supervisory component 15 can be adapted for controlling one or more of the switches 10 to 14, preferably using separate leads and/or a bus system as shown in the depicted example. In particular, the supervisory component 15 controls switch 1 3 for different possible purposes. Closing switch 13 can allow for gener- ating at least one electrical impulse and/or for delivering electrical impulses via the electrodes 2. This is particularly preferred if the electrode device 1 is used for stimulation, e.g. pacing, additionally or alternatively. In one example, the switch 13 is basically closed and an electrical impulse can be delivered as soon as a sufficient amount of energy is available. After generation and/or delivery of the electrical impulse is performed, switch 13 can be opened to prevent any further delivery of an electrical impulse that might be not intended. Thus, the supervisory component 15 together with switch 13 can form a protection means for pro- tecting against unwanted delivery of electrical impulses, e.g., due to any failures or disturbances with effects on the transceiver 4. Alternatively or additionally, the switch 13 can be typically open and can be closed, preferably after the energy buffer 9 has been charged, after a particular time span and/or at a particular time. The switch 13 can be closed by the supervisory component 15 for delivery of the electrical impulse. Hence, the supervisory component 15 can act as a delay means. It preferably comprise a timer for delaying controlling one ore more switches 1 1 to 14.

The time or time span and/or other control schemes, timings, variables or the like can be preset within the supervisory component 15 or can be controlled by the signal S and/or by commands from outside, in particular by a time-varying magnetic field H of a particular shape or comprising a modulation, coding or the like.

The supervisory component 15 can be adapted for closing the switch 1 3 only if switch 10 is open to prevent damaging at the input of amplifier 6 during delivery of an electrical impulse. The supervisory component 15 can be adapted for opening switch 1 1 if it is desired to send a signal S such that the energy of the signal S is not consumed by rectifier 7. Depending on the architecture used for rectifier 7 , it can be necessary to close switch 12 in order to allow for current flowing through the transceiver 4. Thus, it is preferred that the supervisory component 14 is adapted for closing the switch 12 while sending the signal S is intended. Additionally or alternatively, the supervisory component 15 can be adapted for controlling switches inside the rectifier 7 or for controlling further switches, biasing networks or the like not shown in Fig. 1 , in particular inside the amplifier 6 or a pulse forming device 16.

Alternatively or additionally to switch 13 , switch 14 can be provided that does not need to be controllable by supervisory component 15. It is preferred that switch 14 can be controlled from outside e.g. using the magnetic field H. For example, the switch 14 is a reed switch that can be closed using at least a magnetic field of a particular, minimum field strength e.g. minimum field strength H I (cf. Fig. 3). The minimum field strength HI preferably is higher than the field strength of the time-varying magnetic field H used for energy transmission to the electrode device 1 . Thus, generation and/or delivery of the electrical impulse can be controlled independently from transmitting energy to the electrode device 1 using switch 14. It is preferred that the electrode device 1 provides two different work modes or functions, a first one for sending the signal S sensed and a second one for generation and/or delivery of the electrical impulse for stimulation purposes. Is it pointed out, that the magnetic field H preferably is at least basically generated by transceiver 4 while sending the signal S is intended and that the magnetic field H is generated externally if energy transfer to the electrode device 1 and/or delivery of an electrical impulse is intended. Nevertheless, the magnetic field H can be composed by different sources, in particular if energy and signal S transfer are performed at the same time.

In the example shown, the electrode device 1 preferably comprises at least the transceiver 4 and the electrodes 2, wherein transceiver 4 and preferably the amplifier 6, the rectifier 7, the supervisory component 15 and/or the pulse forming device 16 are placed inside the housing and the electrodes 2 are preferably integrated in the electrically installed housing 3 or attached thereon. Thus, it is possible to achieve a compact electrode device 1 comprising at least basically smooth surface. In the example shown, the electrodes 2 are allocated on opposite sides. However, the electrodes 2 can also be arranged, for example, circumferen- tial , at one and or at the other end of the electrode device 1 or the housing 3.

The electrode device 1 optionally can comprise an analyzing means for analyzing the signal S (not shown). This analyzing means can be part of the amplifier 6 or placed in front of its input. In particular, the analyzing means can be config- ured for detecting peaks and/or patterns in the signal S e.g. a P-wave, R-wave and/or S-wave of an electrical activity of heart 5. The analyzed signal S and or a result of these analyses can be sent alternatively or additionally to the signal S itself, in particular by means of the time-varying magnetic field H. The supervisory component 15 can be adapted for controlling the analyzing means, in par- ticular in a pre-defined manner or by means of the time-varying magnetic field H.

In the following, preferred embodiments or implementations of components and operating methods of the electrode device 1 are discussed in further detail . Nev- ertheless, similar or different solutions exist. The transceiver 4 can comprise a coil 21 , a coil core 20 and/or core elements 22, in particular made of a soft magnetic material or ultrasoft magnetic material , for example in the form of wires or strips (cf. Fig. 4) . Such a material has a very low coactive field strength which corresponds to the minimum field strength H I and in particular is less than 0.1 mT. The saturation field strengths of the material are less than about 0.01 to 3 mT. The coil core 20 preferably consists of nonmagnetic or completely or partially of said soft magnetic or ultrasoft magnetic material or a combination of various such magnetic materials.

As an example, the transceiver 4 comprises a coil 21 preferably having a high number of turns, in particular at least 1 ,000 turns, particularly preferably 2,000 turns or more. In the example shown, the coil 21 has substantially 3 ,000 turns or more. In the example shown, the coil inside diameter is preferably 1 to 3 mm, the coil outside diameter is preferably 2 to 6 mm and the coil length LI is preferably 10 to 30 mm. In general , ferrites or ferromagnetic metal powder and/or compound materials, in particular laminated structures, can be used as core materials or soft magnetic materials. An advantage is that as a result of the poor electrical conductivity, these materials only exhibit low eddy current losses.

The proposed transceiver 4 can permit the generation of relatively strong electrical impulses, currents or voltages, in particular an impulse having a voltage of at least 1 V and a time duration of substantially 0.1 ms or more, in particular if stimulation function is intended. In particular, this relatively strong and relatively long-lived electrical impulse can also be achieved with the soft magnetic core material . A magnetic resetting pulse as with the Wiegand wires or the like can be used. However, a combination with other magnetic materials or structures is possible. The transceiver 4 can be configured such that a pulse-like induction voltage is generated, in particular for stimulation, when a minimum field strength H I of the, e.g., external magnetic field H acting on the electrode device 1 or transceiver 4 is exceeded (cf. Fig. 3). For this purpose, the transceiver 4, particularly preferably, has a coil core 20 which exhibits an abrupt change in the magnetization, i .e. bitable magnetic properties, when the minimum field strength H I is ex- ceeded. This abrupt change in magnetization or magnetic polarization results in the desired pulse-like induction voltage in an associated coil 21 . Alternatively or additionally, a reed relay or switch 14 and/or switch 13 in series with at least one electrode 2 can be used for generation and/or delivery of the electrical impulse. The switches 13 and/or 14 alternatively or additionally can be or comprise semiconductor devices.

In order to achieve the aforesaid bitable magnetic behavior of the coil core 20, as shown in the diagram according to Fig. 3 as an example, in the example shown the coil core 20 is preferably constructed of at least one core element 22, preferably of a plurality of core elements 22 (cf . Fig. 4).

It is possible to use more than one transceiver 4 for the electrode device 1 , in particular at least one for receiving energy and one for sending purposes. These transceivers may comprise different coils, in particular coils of a different number of turns. For example, it can be preferred that the transceiver 4 for receiving energy can comprise at least 500 turns, preferably at least 1 .000 turns, in particular 2.000 turns or more. A transceiver 4 for sending the purposes can comprise a lower number of turns, for example more than 5, preferably more than 50 turns and/or less than 500 turns, preferably less than 200 turns. If different transceivers 4 are use, it is particularly preferred to realize them using a joint core or a coil , wherein the sending part can be contacted using a center tab. Thus, advantages regarding consumption of space can be obtained. The individual core elements 22 preferably have a diameter of about 50 to 500 μ χη, in particular substantially 100 μτη and/or a length of 5 to 20 mm, in particular substantially 15 mm.

The core elements 20 are particularly preferably so-called Wiegand wires as de- scribed in US 3,820,090 and/or supplied by HID Corp., 333 St. Street, North, Heaven, CT 06473 , USA under the trade name "Wiegand Effect Sensors" or so- called impulse wires as supplied by Tyco Electronics AMP GmbH, Siemen- strasse 1 3 , 67336 Speyer, Germany. In the Wiegand wires the soft and hard magnetic layers are formed of the same material , the different magnetic proper- ties being achieved in particular by mechanical reforming. With regard to the possible structure and/or the materials used, reference is made supplementarily, additionally or alternatively to the article "Power Generating Device Using Compound Magnetic Wire" by A. Matsushita et al. published in the journal "Journal of Applied Physics", Vol. 87, No. 9, 1^st May 2000, page 6307 to 6309 and to the article "A Soft Magnetic Wire for Sensor Applications" by M. Vazquez et al . published in the journal "J. Phys. D: Appl . Phys.", Vol . 29, 1996, pages 939 and 949, which are introduced as additional disclosure. As already explained in the beginning, the transceiver 4 can be provided with energy in a wireless manner, in particular by the time-varying magnetic field H. Preferably, a current is induced in the coil 21 by the time- varying magnetic field H. Alternatively or additionally, the transceiver 4 may comprise an antenna and/or is adapted for receiving energy from electromagnetic waves or the like. Preferably, the term "time-varying magnetic field" in the sense of the present invention incorporates any field or wave comprising a magnetic component, e.g. electromagnetic waves or the like.

Energy received by transceiver 4 preferably can be transmitted to the rectifier 7. The rectifier 7 is adapted to transform energy from a time-varying or alternating nature to a substantially continuous one. In particular, an alternating current or voltage is rectified.

Typically, diodes in a bridge configuration are use for rectifying. As shown in Fig. 5, the rectifier 7 for commutation preferably comprises semiconductor switches 8A to 8D with a control port instead or additionally to (intrinsic) diodes. These switches 8A to 8D can be configured to have a threshold in the area of a zero-crossing or, particularly in contrast to diodes having a threshold voltage of about 0.4 to 0.8 V. Particularly preferably, the semiconductor switches 8A to 8D, in particular MOSFETs or the like, of the rectifier 7 have a threshold voltage of about zero and/or are biased at about threshold. In the example shown, the threshold voltage and/or a biasing offset from threshold are less than ±200 mV, in particular less than ±100 mV or ±50 mV. By this measure, a voltage drop across the devices forming the rectifier 7 can be minimized and/or avoided. Thus, the rectifier 7 with semiconductor switches 8 A to 8D can allow for reduced power losses and/or more efficient rectifying.

In the following, an example for operating the rectifier 7 is given. If the potential of node K l is higher than the potential of node K2, semiconductor switch 8B, preferably a n-channel-MOSFET, is conducting and connects node K3 to node K2. Furthermore, semiconductor switch 8C, preferably a p-channel-MOSFET, is conducting and connects node K4 to node Kl . Semiconductor switches 8A and 8D are non-conducting or having a high resistance and/or impedance as long as the potential of node K l is higher than the potential of node K2.

If potential of node K2 is higher than the potential of node K l , semiconductor switches 8A and 8D are conducting and semiconductor switches 8B and 8C having a high resistance behavior. Thus, node K3 preferably is always connected to the one of the nodes K l and K2 with the higher potential and node K4 always is connected to the one of the notes Kl and K2 with the lower potential leading to the rectifying behavior.

The control ports or steering ports, in particular gates, of the semiconductor switches 8A to 8D can be connected and/or contacted via inductive elements I as shown in Fig. 6. Typically, semiconductor switches 8A to 8D comprise an intrinsic capacitive behavior at their control ports that can be compensated for using the inductive elements I. Furthermore, Zehner diodes Z may be used to prevent over-voltage at the control ports of semiconductor switches 8A to 8D.

After rectifying has been performed, the energy can be stored in the energy buffer 9, in particular a capacitor. Preferably, the energy buffer 9 is adapted for storing the energy needed for five electric impulses or less, in particular for generating only one single electrical impulse. Thus, the energy buffer 9 can be very small , in particular much smaller than a storing device as a battery or the like.

The amplifier 6 can be realized as shown in Fig. 8. A push-pull output stage comprises MOSFETs M5 and M6, wherein, preferably, MOSFET M5 is of the n- channel type and/or MOSFET M6 is of the p-channel-typ. The gates of MOSFETS M5 and M6 preferably are controlled by the signal S sensed via elec- trodes 2 and the amplified signal S is delivered at the node connected to the drains of MOSFETS M5 and M6. Nevertheless, other solutions are possible.

For sending the signal S , the supervisory component 15 can close switch 10, open switch 1 1 and close switch 12. Alternatively or additionally, in particular if a rectifier 7 comprising semiconductor switches 8A to 8D is used, switch 1 1 and/or switch 12 can be omitted and their function can be realized using switches 8A to 8D. Opening switch 1 1 can correspond to opening switches 8A and 8C. Closing switch 12 can correspond to closing switch 8B . Switch 8D should be opened as well in order to prevent a short across energy buffer 9. Here, switches 8A to 8D preferably are controlled by the supervisory component 15 as well .

Then the signal S , preferably sensed across two ore more electrodes 2, preferably is amplified by amplifier 6 and converted to a corresponding time-varying mag- netic field H by means of one ore more transceivers 4.

In the following, methods and/or components for controlling and/or generating an electrical impulse for stimulation, in particular of the heart 5, using electrode device 1 are explained in further detail .

The electrode device 1 preferably comprises means for sensing and sending the signal S , a rectifier 7 for rectifying energy received by the transceiver 4, a delay means for generating a delay between reception of the energy and generation of the electrical impulse, and/or a protection means to prevent or block generation and/or delivery of electrical impulses when delivery is not intended. Furthermore, the electrode device 1 can also be implemented by other structural elements having a corresponding function.

The electrode device 1 preferably comprises a protection means, in particular re- alized by supervisory component 15 and/or (semiconductor) switch 13 as already mentioned . The semiconductor switch 13 preferably connects the rectifier 7 and/or the storing element 9 to at least one of the electrodes 2. The semiconductor switch 13 can be provided in series with at least one of the electrodes 2. Thus, generating an electrical impulse and/or delivery of the electrical impulse can be blocked by semiconductor switch 13. Preferably, the semiconductor switch 13 has a high resistance state for blocking generation and/or delivery of electrical impulses as well as a low resistance state for generating an electrical impulse or for enabling its generation, the state in particular is controlled by the supervisory component 15.

For example, energy is transmitted to the electrode device 1 and a first electrical impulse is generated and/or delivered. As long as this first electrical impulse is generated , the semiconductor switch 13 is conducting, i .e. closed, and/or the supervisory component 15 generates a corresponding signal S that leads to a con- ducting semiconductor switch 13. After delivery of the first electrical impulse, the supervisory component 15 generates a signal S controlling the semiconductor switch 1 3 such that it changes from a low resistance state (closed) to a high resistance state (open) for blocking generation and/or delivery of further electrical impulses. Preferably, the supervisory component 15 holds this state for particular time span . Afterwards, the supervisory component 15 can change the control signal S in order to switch the (semiconductor) switch 13 into a low resistance state and the next electrical impulse can be generated and/or delivered. By this measure, any generation or delivery of an electrical impulse caused by a disturbance or the like can be prevented.

The protection means preferably is adapted to prevent generation and/or to block delivery of electrical impulses for time span greater than 0.5 ms, preferably greater than 1.0 ms and/or less than 100 ms, preferably less than 20 ms, in particular 10 ms or less. Thus, generation and/or delivery of an electrical impulse can be prevented or blocked during a short time span that has been found to be sufficient for preventing unwanted electrical impulses that may occur due to a disturbance event, and at the same time a generation of a following electrical impulse is not affected. Alternatively or additionally, supervisory component 15 and/or semiconductor switch 13 can provide or act as a means for generating a delay between reception of the energy and the generating of at least one of the electrical impulses. If energy is received and preferably rectified, the supervisory component 15 may control the semiconductor switch 13 to get into or keep the high resistance state (open) directly. Afterwards, the energy delivered to the electrode device 1 can be stored in the energy buffer 9 for a particular time span, in particular greater than 1 ms, preferably 10 ms and/or less than 500 ms, preferably less than 300 ms. Afterwards, the semiconductor switch 13 can be switched into its low resistance state, in particular by the supervisory component 15, and the electrical impulse can be generated and/or delivered.

Preferably, the supervisory component 15 can be programmed in advanced and/or by signals S transmitted by the magnetic field H accordingly. The supervisory component 15 can comprise a decoding means for decoding a signal S provided by the time varying magnetic field H. Therefore, the magnetic field H may comprise modulated information that can be demodulated by the supervisory component 15 and/or the rectifier 7, in particular an amplitude modulation that automatically can be demodulated by rectifier 7. This information can be used for programming and/or controlling the supervisory component 15.

It is preferred to use a supervisory component 15 with a low power consumption, in particular in the nW regime. Fig. 7A to 7C show typical timing diagrams of the supervisory component 15. VCC can correspond to the rectified voltage delivered by the rectifier 7. Preferably, the voltage delivered by rectifier 7 is smoothed by energy buffer 9. Fig. 7A shows an example for the rectified voltage and/or for a voltage associated with the energy buffer 9, which in the following will be called process voltage. As soon as the energy transmission by means of the time-varying magnetic field H starts, the process voltage rises up, in particular exceeding the pinch off voltage V_TH of the supervisory component 15 i.e. its minimum operation voltage.

Fig. 7B and 7C are showing an inverted and a non-inverted reset signal S, respectively. The supervisory component 15 is configured such that the reset signal S shown in Fig. 7B keeps low although the process voltage exceeds the pinch of voltage V_{JI I} leading to an active reset. As shown in Fig. 20C, the non-inverted reset signal S has a high level, leading to an active reset, too. Thus, for the time span of t_RP (typically a few ms to 100 ms) starting from the time when the process voltage exceeds V_TH, the reset for the supervisory component 15 keeps active. Thus, disturbance of initialization of the supervisory component 15 can be prevented. Afterwards, the non-inverted reset signal S switches to high and/or the inverted reset signal S switches to low such that the supervisory component 15 starts working.

The pulse forming device 16 can be realized as a filter, a low pass filter or the like. Preferably, the pulse forming device 16 comprises a capacitor 18 and/or a resistor 19 (cf. Fig. 2). Additionally or alternatively, an inductive element (not shown), such as a coil , can also be used for pulse forming. The pulse forming device 1 6 can be used for forming or reforming a pulse-like induction voltage which is generated or delivered by transceiver 4 and/or energy buffer 9. The re- formed electrical impulse can then be delivered for stimulation via the connected electrodes 2.

In the following, the inventive system 23 is described with reference to Fig. 9 depicting a schematical sectional view .

In the example shown, the proposed system 23 is configured or works as a capturing system for an intracardiac electrogram and/or as a cardiac pacemaker. However, the present invention is not restricted to this. For example, the system 23 can additionally or alternatively operate as the system for capturing human body signals S and/or bio-potentials e.g. ECG signals S, EEG signals S, ERG signals S, EMG signals S, EOG signals S and/or signals S corresponding to a glucose concentration, a blood pressure and acoustic signal S for phono cardiography or the like. Furthermore, the system can work as a stimulation system as a defibrillator or can be used for other purposes and at other locations, in particular in the human or animal body.

The system 23 preferably comprises an, in particular implantable, receiver 24 and/or control device 28 and the implantable electrode device 1 separate therefrom . In the example shown, the receiver 24 and/or control device 28 are im- planted, preferably as a joint unit or control unit 31 , in particular in the thoracic cage between the skin and the ribs.

Fig. 10 is a schematic view of the joined control unit 3 1 comprising receiver 24 and control device 28. In the example shown, the receiver 24 and control device 28 are assigned to a common transceiver or coil 29 for receiving and/or generat- ing a magnetic field H. The control unit 31 , the receiver 24 and/or the control device 28 preferably comprise an energy storage device or battery 32, such as a rechargeable battery. Preferably, the receiver 24, the control device 28 and the coil 29 can form a joint constructional unit or control unit 31 , e.g. with a common and/or implantable case. The control unit 31 , control device 28 and/or receiver 24 in addition can comprise a battery 32 which can preferably be charged in an inductive manner. Fig. 10 shows a receiver comprising an input amplifier, preferably a low noise amplifier and/or the control unit comprises a power amplifier 34.

The control unit 31 , receiver 24 and/or control unit 28 are preferably in a flexible housing as it should be implanted directly above the heart near the thoracic wall . To achieve this flexibility, the control unit 31 can be embedded in a silicon cush- ion, however other soft materials can also be used. The control device 28 can be configured such that the magnetic field H is generated intermittently and/or wherein the control device 28 is configured such that the magnetic field H has a switch-on ratio of less than 0.5 , in particular less than 0.25, particularly preferably substantially 0.1 or less.

The receiver 24 and/or control device 28 can be implanted as present-day cardiac pacemakers . However, it is not absolutely essential to implant the receiver 24 and/or the control device 28. In principle, each of them can also be used in the non-implanted state, that is, as an external device for receiving a signal S from the electrode device 1 and/or for controlling and/or supplying the electrode device 1 .

The coil 29 can optionally be provided with a ferromagnetic, soft-magnetic or ul- trasoft magnetic core or a half-sided cladding or another shoe or conducting ele- ment to concentrate the magnetic flux. Alternatively or additionally, the coil 29 can comprise antenna-like elements or can form an antenna, and/or the receiver 24 and the control device 28 each comprise one or more elements or coils for transmitting and/or receiving signals S and/or energy. In particular, a coil 29 preferably comprising a sending coil 25 and/or a receiving coil 26. The sending coil 25 can comprise a lower number or turns than the receiving coil 26. Preferably, coil 29 or 26 is assigned to a receiver 24 and/or coil 29 or 25 is assigned to the control unit 28. Thus, coil 29 can comprise a tab that can divide the number of windings of coil 29 asymmetrically, such that only a few turns are used for sending purposes and more or all turns are used for receiving purposes. Moreover, a magnetic field sensor 30 can be used for receiving or detecting magnetic field H . The receiver can comprise the magnetic field sensor 30 as well as the coil 26 or 29. The magnetic field sensor 30 can be a sensor of the fluxgate type or the like.

The receiver 24 can preferably receive or take up the required heart information via a separate receiving coil (not shown) and/or magnetic filed sensor 30, and/or via the (common) coil 29, in particular so that the generation of electrical impulses by the electrode device 1 can be controlled using this signal S . For example, reference is also made here to US 5,41 1 ,535 A. For example, additional electrodes or sensors (not shown) can also be connected directly to the control device 28 or the receiver 24.

Various properties, features and operating modes of the proposed method and the proposed stimulation system 23 are explained in detail hereinafter. The electrode device 1 is preferably implanted in the heart 5 or the heart muscle of the patient, who is shown only schematically and in part. The electrode device 1 can be implanted, for example, as described in US 5,41 1 ,535 A .

Depending on the configuration, the electrode device 1 can also be used inde- pendently of the receiver 24 and/or the control unit 28. For example, it is possible that the electrode device 1 can be supplied with energy and/or controlled by another device, optionally even by a nuclear spin tomograph or the like, with suitable matching. Thus, further possible uses are obtained which go substantially beyond the possible uses of conventional sensing and/or stimulation sys- terns. An electrical signal S , in particular an intracardiac ECG, an EEG and/or an EMG signal S is automatically sensed from the surrounding tissue by the implantable and/or implanted electrode device 1 . The electrode device 1 converts the signal S into a corresponding time-varying magnetic field H as already described in detail . This signal S is transmitted to the receiver 24 in a wireless manner and the receiver 24, in particular the associated coil 26 and/or 29, preferably converts the signal S into an electrical signal S. Furthermore, the electrode device 1 is preferably supplied with energy by the control device 28 in a wireless manner by means of the time-varying magnetic field H, which will now be described in further detail .

The control device 28 preferably generates an amplified a power-signal S, for example a sawtooth signal S, a sign wave or the like. This power-signal S is provided to coil 29 for generating a corresponding magnetic field H . Furthermore, the control device 28 can comprise means for generating specific power-signal S shapes as peaks, modulation, coding or the like for controlling the electrode device 1 . The power-signal S and/or the result of the analyses can be use by the control device 28, and the control device 28 may generate a specific time- varying magnetic field H, of a special shape, minimum field strength, coding or the like, in particular preferably by coil 29. For example, a strong sine wave can be used for transfer an energy and information, in particular in form of peaks and/or modulation, is superposed to the power-signal S primarily used for energy transfer. The control device 28 further can be controllable or synchronable, preferably to bioelectrical activity of heart 5 , in particular to the signal S sent by the electrode device 1 . Preferably, the control device can control the electrode device 1 to send a sensed signal S. The receiver 24 can receive and, preferably, analyze the signal S and/or time varying magnetic field sent by electrode device 1 . Preferably, the signal S is received by means of coil 29 and/or by means of the magnetic field sensor 30 and/or internal magnetic field sensor 27. The incoming signal S can be amplified and/or analyzed. A data output and/or a display for delivery of the signal S, the analyzed signal S or the like can be provided (not shown). It is particularly pre- ferred that specific values or timings corresponding to the electrical activity of the heart 5 can be analyzed and, preferably, provided to the control device 28.

If a stimulation function is intended, the control device 28 can trigger the elec- trode device 1 in a wireless manner by means of the time-varying magnetic field H for generating and/or delivering at least one electrical impulse. It is particularly preferred, that the triggering is synchronized by or to the signal S sent by the electrode device l by the receiver 26. The received signal S preferably is converted to an electrical signal S by the receiver 26.

According to the example shown in Fig. 9, a plurality of electrode devices 1 can be used which, in particular, can be controlled and/or supplied with energy by a common control device 28. Particular advantages of the invention reside in the possibility that the wireless electrode device 1 can be implanted in more suitable regions for sensing and/or stimulation, in particular, of the heart muscle, than is possible with wire-bound electrodes. Moreover, a plurality of electrode devices 1 can be implanted at different locations whereby improved sensing and/or stimulation and, in particular, better cardiac dynamics can be achieved. The electrode devices 1 can then be implanted at different locations, for example.

As a result, if different minimum field strengths are used for the electrode devices 1 , different desired phase shifts, energy differences or the like of the electrical impulses delivered by the individual electrode devices 1 can be achieved. In particular, the delay means can be used for synchronizing the electrode de- vice 1 additionally or alternatively.

Preferably, different electrode devices 1 in the stimulation system 23 are placed in some distance, in particular in a distance greater than 1 cm, preferably greater than 2 cm and/or less than 20 cm, preferably less than 15 cm.

It is particularly preferred that at least one of the electrode devices 1 comprises a delay means for generating a delay between reception of the energy and the generation of at least one of the electrical impulses as already explained in detail. Thus, different electrode devices 1 can generate electrical impulses with a delay between a first electrical impulse generated by the first electrode device 1 and a second electrical impulse generated by the second electrode device 1 which preferably comprises the delay means in this example. Thus, a common, additive stimulation can be adapted to the natural behavior of an object to be stimulated. For example, the heart 5 can be stimulated and/or sensed at a first position and, after a short delay, at a second position, preferably according to its typical activation and/or stimulation. Therefore, the second electrode device 1 may comprise a reed relay as delay means that can block the delivery and/or generation of the electrical impulse for the particular time span until a minimum field strength HI for triggering is exceeded. In a stimulation system with more than two electrode devices 1 , it is particularly preferred that all electrode devices 1 or at least one less than the number of electrode devices 1 actually used comprise delay means, in particular (micro-) reed relays 14. Then, different electrode devices 1 can be triggered independently, in particular if, as preferred, the different reed relays of different electrode devices 3 comprising different thresholds, i.e. different minimum magnetic field strengths HI for triggering.

Figure 12 shows another embodiment of the proposed system 23 comprising the control device 28, the electrode device 1 and an external charging device 35 in a schematic diagram similar to a block diagram. In this embodiment a plurality of short magnetic field pulses are generated as a sequence by the control device 28 during the switch-on time of the magnetic field H, i.e. during the switch-on phases. In particular, it is thus achieved that the coil core 16 always changes its magnetization far below the saturation state. Thus, a minimum energy consump- tion can be achieved.

In the example shown according to Fig. 12, bipolar magnetic field pulses are preferably generated by means of power amplifier, in particular a bridge of switching transistors M l to M4 (e.g. MOSFETS, also in complementary design) or other switching semiconductor components. Also indicated in Fig. 12 are the coil 29, a control and the energy storage device or battery 32 of the control device 2. The control can, for example, comprise one or two signal generators V3 and V4. Preferably connected in parallel to the battery 32 is a smoothing capacitor 37. In addition, separating electronics 38 such as a switch or the like can be provided. The control device 28 or its coil 29 is preferably configured such that the control device 28 or its battery 32 can be inductively charged in the implanted state, in particular via the coil 29. For generating the required electromagnetic field dur- ing charging the charging device 35 is equipped with a suitable coil 39 and a corresponding power supply, in particular an alternating current supply 40.

In the following, an particular operation scheme for generating an electrical impulse using the system 23 described in detail .

According to the particular operation scheme, the electrode device 1 is configured such that an electrical impulse is only generated and delivered when a (first) minimum field strength of the magnetic field is exceeded. Furthermore, this or another pulse generation or triggering is preferably only made possible after re- spective previous activation.

The impulse generation and triggering preferably takes place as a result of the external magnetic field H acting on the transceiver 4 being varied in time so that when the first minimum magnetic field strength HI is exceeded.

According to one aspect, an abrupt change in the magnetization of the core elements 22 or the coil 21 takes place as shown in the schematic magnetization curve according to Fig. 1 1 . As a result of the inverse Wiedemann effect, this abrupt change in the magnetization results in a pulse-shaped induction voltage (pulse P in Fig. 1 1) in the allocated coil 21 of the electrode device 1 . This first minimum field strength H I is therefore a switching threshold. Alternatively or additionally, the delay means, in particular a reed relay 14, and/or the protection means may be activated or controlled by the first minimum magnetic field strength H I .

The induced voltage pulses P can have an amplitude of up to about 5 V and are about 5 to 100 ^s long. In order to achieve a preferably longer pulse duration, as is usual for cardiac stimulation, the optional pulse forming device 16 is preferably used that can realize a smoothing filter function or a low pass. The induced voltage pulse P can thus in particular be stretched in time. Alternatively or addi- tionally, a longer pulse duration can also be achieved by bundling a plurality of core elements 22 in the coil 21 , in particular so that the pulse forming device 1 1 can be completely omitted. The magnitude of the minimum field strength H I depends on various factors, in particular the manufacturing conditions of the core elements 22 if used. The minimum field strength H I is preferably between 0.5 and 20 mT, in particular between 1 to 10 mT and is quite particularly preferably about 2 mT. These values are already substantially above the values for magnetic fields usually permis- sible in public so that any triggering of an electrical impulse by interference fields usually expected is eliminated.

In one example with an transceiver 4 with optional the individual core elements 22 or coil core 20 having bistable magnetic properties, in particular in the pre- ferred structure of layers having alternately soft and hard magnetic properties (Fig. 4), can be used in various ways. In the example shown, preferably asymmetrical behavior is achieved on running through the magnetization curve or hysteresis. For resetting or attaining the starting point, that is activation for the triggering of the next impulse, the polarity of the coil core 20 is (completely) re- versed by the external magnetic field H having the opposite direction when the second minimum field strength H2 is exceeded, as can be deduced from the magnetization curve in Fig. 1 1 . It should be noted that in said processes in each case only the polarity of the soft magnetic material layers is reversed whilst the magnetization of the hard magnetic material layers is thus retained. In principle, however, higher magnetic fields H can also be used to reverse the polarity of the hard magnetic layers if required.

In the example shown, the external magnetic field H, in particular generated by the control device 28, is used both for controlling (triggering) the generation and delivery of an electrical impulse by the electrode device 1 and also for supplying the electrode device 1 with the energy necessary for generating the electrical impulse. In addition, the magnetic field H is preferably also used for said activation of the electrode device 1 for in order to enable generation of the next electrical impulse. However, this can be also be effected in another manner or by another signal S . The external magnetic field H preferably runs at least substantially parallel to the longitudinal direction of the coil core 20 or the core elements 22. Figure 1 1 shows schematically a preferred time profile V I of the external magnetic field H acting on the electrode device 1 and the corresponding time profile V2 of the voltage U induced in the electrode device 1 or its transceiver 4. Such a profile preferably is used for the stimulation functionality. The magnetic field H is preferably generated intermittently and/or as an alternating field . The magnetic field H preferably has a switch-on ratio of less than 0.5, in particular less than 0.25 , particularly preferably substantially 0.1 or less.

The field strength of the magnetic field H has a substantially ramp-shaped or sawtooth-shaped time profile, at least during the switch-on times as indicated in Fig. 1 1 .

The magnetic field H is alternately generated with an opposite field direction for alternate generation of an electrical impulse and activation of the electrode de- vice 1 before generation of the next electrical impulse. The activation preferably takes place only shortly before generating the next electrical impulse, as indicated in Fig. 1 1 .

The frequency of the magnetic field H is preferably only a few Hz, in particular less than 3 Hz and corresponds in particular to the desired frequency of the electrical impulses to be generated. Alternatively or additionally, the magnetic field H can comprise much higher frequencies, e.g. of a few Hz or in the kHz range, in particular for controlling and/or transmitting of energy. The frequency of only a few Hz may be used and/or part of the magnetic field H for triggering purposes and/or if a direct generation of the electrical impulse is intended.

Individual features, aspects and elements of the individual embodiments and variants can be arbitrarily combined with one another or used in other stimulation systems or electrode devices. Reference List

1 electrode device 35 30 magnetic field sensor

2 electrode 31 control unit

3 housing 32 battery

4 transceiver 33 amplifier

5 heart 34 power amplifier

6 amplifier 40 35 changing device

7 rectifier 36 control

8A semiconductor switch 37 smoothing capacitor

8B semiconductor switch 38 separating electronics

8C semiconductor switch 39 coil

8D semiconductor switch 45 40 supply

9 energy buffer H magnetic field

10 switch H I minimum field strength

1 1 switch H2 minimum field strength

12 switch I inductive element

13 switch 50 Kl node

14 switch K2 node

15 supervisory component K3 node

16 pulse forming device K4 node

17 housing M l transistor

18 capacitor 55 M2 transistor

19 resistor M3 transistor

20 core M4 transistor

21 coil M5 MOSFET

22 core element M6 MOSFET

23 system 60 S signal

24 receiver V I time profile

25 transmit coil V2 time profile

26 receive coil V3 signal generator

27 magnetic field sensor V4 signal generator

28 control device 65 Z zehner diod

29 coil

Claims

Claims:

1 . An implantable electrode device (1), in particular for sensing an intracardiac electrogram, comprising at least two electrodes (2) for sensing a signal S from the surrounding area and comprising a transceiver (4) for sending the signal (S) in a wireless manner, wherein the electrode device (1) is configured to be supplied with energy exclusively by the sensed signal (S) and/or in a wireless manner by means of a time-varying magnetic field (H).

2. The electrode device according to claim 1 , wherein at least one electrode is connected to the transceiver (4), in particular via an amplifier (6) for amplifying the signal (S), and wherein the transceiver (4) is configured for generating the time-varying magnetic field (H) corresponding to the signal (S).

3. The electrode device according to claim 1 or 2, wherein the electrode device (1 ) comprises a rectifier (7) for rectifying energy supplied to the electrode device (1 ), in particular comprising semiconductor switches (8A - 8D), preferably in a H-bridge configuration.

4. The electrode device according to claim 1 to 3, wherein the electrode device (1 ) comprises an energy buffer (9), preferably connected to the output of the rectifier (7), in particular wherein the energy buffer (9) has a maximum capacity for generation and/or delivery of five electrical impulses or less, preferably for two, in particular for one electrical impulse and/or for transmitting the signal (S) less than 60 seconds, preferably less than five seconds, in particular 3 seconds or less.

5. The electrode device according to any one of the preceding claims, wherein the electrode device (1) comprises one or more switches (10 - 14), preferably semiconductor switches, in particular MOSFETs, for connecting and disconnect- ing at least one electrode to the input of the amplifier (6), and/or the output of the amplifier (6) to the transceiver (4) and/or the input of the rectifier (7) to the transceiver (4) and/or the output of the rectifier (7) to at least one electrode (2).

6. The electrode device according to any one of the preceding claims, wherein the electrode device (1) comprises a supervisory component (15) adapted for controlling at least one switch (10 - 14), in particular with a timer for delayed controlling the switch (10 - 14) and/or adapted for coding the signal (S).

7. The electrode device according to any one of the preceding claims, wherein the electrode device (1) is adapted for generating electrical impulses and/or delivering electrical impulses via the electrodes (2).

8. The electrode device according to any one of the preceding claims, wherein the electrode device ( 1 ) is controllable in an exclusively wireless manner by means of the time-varying magnetic field (H), in particular for triggering generation or delivery of the electrical impulses.

9. The electrode device according to any one of the preceding claims, wherein the electrode device (1) comprises analyzing means for analyzing the signal (S), in particular for detecting peaks and/or patterns in the signal (S), wherein the electrode device (1 ) is adapted to send the analyzed signal (S) and/or an result of this analysis by means of the time-varying magnetic field (H).

10. The electrode device according to any one of the preceding claims, wherein the length of the electrode device (1) is less than 3 cm, preferably less than 2 cm, in particular less than 1 ,5 cm and/or the diameter of the electrode is less than 1 cm, preferably less than 8 mm, in particular 5 mm or less.

1 1 . The electrode device according to any one of the preceding claims, wherein the electrodes (2) are incorporated in or attached to the surface of the electrode device ( 1 ), preferably such that the electrode device (1 ) has an at least basically compact, smooth shape.

12. A system (23), in particular for capturing an intracardiac electrogram and/or for cardiac pacing, comprising at least one implantable electrode device (1) according to any one of the preceding claims and a receiver (24) adapted for receiving the signal (S) transmitted via a time-varying magnetic field (H).

13. The system according to claim 12, wherein a transmit coil (25) and/or a receive coil (26) and/or a magnetic field sensor (30), in particular a magnetometer, for receiving the signal (S) is assigned to the receiver (24).

14. The system according to claim 12 or 13 , comprising a control device (28) configured for transmitting energy to the electrode device (1) and/or for controlling the electrode device (1) in a wireless manner by means of the time-varying magnetic field (H).

15. The system according to claim 12 to 14, wherein the control device (28) is configured for triggering generation and/or delivery of electrical impulses by the electrode device ( 1 ), in particular depending on the signal (S), the analyzed signal (S) and/or the result of the analysis transmitted by the electrode device ( 1 ).

16. The system according to claim 12 to 15, wherein the control device (28) and the receiver (24) form a, preferably implantable, joint constructional unit or control unit (31 ).

17. Method, wherein an electrical signal (S), in particular an (intracardiac) ECG signal (S), an EEG signal (S) and/or an EMG signal (S), is automatically sensed from a surrounding tissue by an implantable electrode device (1 ), wherein the signal (S) is converted into a corresponding time-varying magnetic field (H), wherein the signal (S) is transmitted to a receiver (24) in a wireless manner, and wherein the signal (S) is converted into an electrical signal (S) by the receiver (24).

18. Method according to claim 17, wherein a control device (28) triggers the electrode device ( 1 ) in a wireless manner by means of the time-varying magnetic field (H) for generating and/or delivering an electrical impulse, preferably wherein the triggering is synchronized by the signal (S).

19. Method according to claim 17 or 18, wherein the electrode device (1) is supplied with energy by the control device (28) in a wireless manner by means of the time- varying magnetic field (H).