WO2012013342A2

WO2012013342A2 - Stimulation system with synchronized wireless electrode devices

Info

Publication number: WO2012013342A2
Application number: PCT/EP2011/003763
Authority: WO
Inventors: Zijian Bai; Christian Kocks; Sebastian Rickers; Guido Bruck; Peter Jung; Pierre Grandjean; Erhard Kisker; Heinrich Wieneke
Original assignee: Md Start Sa
Priority date: 2010-07-27
Filing date: 2011-07-27
Publication date: 2012-02-02
Also published as: WO2012013342A3

Abstract

Stimulation system, preferably a cardiac pacemaker, is provided comprising at least two implantable electrode devices for generating electrical impulses, wherein the electrode devices are configured as wireless units and are adapted to be supplied with energy exclusively in a wireless manner by means of a time varying magnetic field. The electrode devices are adapted such that a time delay between two or more electrical impulses of different electrode devices can be obtained and/or controlled, and/or the electrode devices are adapted to be controlled and/or supplied with energy by means of the time-varying magnetic field of different transmission characteristics, in particular frequencies and/or polarities.

Description

Stimulation System with Synchronized Wireless Electrode Devices

The present invention relates to a stimulation system, preferably a cardiac pace- maker, and to a method for operating at least two implantable electrode devices.

In the following description of the invention, the focus is primarily on cardiac pacemakers. However, the present invention is not restricted to this particular solution, but in general can be applied to other stimulation devices or systems which operate electrically and, in particular, deliver electrical impulses for stimulation. Alternatively or additionally, the stimulation system and/or the method according to the present invention can be applied to deep brain stimulation, nerve stimulation, muscle stimulation or the like. Cardiac pacemakers stimulate the heart beat by means of electrical impulses which are introduced into the muscle tissue of the heart. For this purpose, a cardiac pacemaker is usually implanted, for example, near the shoulder of the thoracic cage, at least one probe or electrical lead being guided from the implanted cardiac pacemaker via a vein into the atrium or the chambers of the heart and an- chored there. The electrical lead is problematical or disadvantageous. This runs 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 of the probes or leads due to material fatigue as a result of the severe mechanical stressing during body movements is particularly high. Another compli- cation frequently encountered is dislocation of the probes triggered by movements of the patient.

Stimulation by magnetic impulses has been proposed, for example, in US 5,170,784 A in order to avoid the electrical lead and the electrode. However, purely magnetic stimulation does not function satisfactorily so that magnetically stimulating cardiac pacemakers have not been generally accepted.

US 5,41 1 ,535 A discloses a cardiac pacemaker with an implantable control device and a separate electrode device. Electrical signals of 10 MHz to a few GHz in particular are transmitted without wires between the control device and the electrode device for controlling the electrode device. The actual power supply of the electrode device is provided via a battery integrated in the electrode device. Such cardiac pacemakers with a separate electrode device have not been widely accepted so far. This might reside in the fact that the electrode device is of a con- siderable size and has a limited operating time because of the battery.

The article "A Surgical Approach to the Management of Heart-Block Using an Inductive Coupled Artificial Cardiac Pacemaker" by L.D. Abrams et.al ., published in the journal "The Lancet", 25^th June 1960, pages 1372 to 1374, describes a method for stimulating a heart where an external control device comprising a coil to be located externally on the body is inductively coupled to a coil implanted between the skin and the ribs. Two electrical leads lead from the implanted coil to two electrodes in the heart muscle. The wiring between the implanted coil and the electrodes at a distance therefrom results in the same prob- lems as in the usual cardiac pacemaker described above where at least one electrode is connected to the implanted cardiac pacemaker via an electrical lead through a vein. Furthermore, the implantation of a pacemaker system requires opening the thoracic cage and involves an open-heart operation. Moreover, the implanted coil is very sensitive to external electromagnetic fields so that undesir- able interfering voltages are induced and appear at the electrodes.

JP 06 079 005 A discloses an implantable cardiac pacemaker whose battery can be inductively recharged from outside via a coil. US 5,405,367 A discloses an implantable microstimulator. The microstimulator comprises a receiving coil, an integrated circuit and electrodes. It can be supplied with energy and with control information via an external magnetic field generated by an external coil having an allocated oscillator and an allocated stimulation control device. Such a microstimulator is not suitable for cardiac stimulator or as a cardiac pacemaker since it is relatively large for sufficient capacity and requires an external energy supply.

WO 2006/045075 A l relates to various configurations of systems that employ leadless electrodes to provide pacing therapy. In particular, a single magnetic pulse is used to generate an electrical pulse in an electrode device. This is problematic, in particular due to magnetic saturation. US 2009/0024180 Al 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.

US 5,713,939 A l relates to a data communication system for control of transcu- tanous energy transmission to an implantable electrode device, wherein a transmitting coil of an external device and receiving coil of an associated implantable receiver are inductively coupled for energy transfer. The receiving coil is connected to an rectifier input. The rectifier output is permanently connected to a smoothing capacitor and switchable connected to a rechargeable battery. For terminating a charging procedure, the battery is disconnected from the rectifier, which can be detected by the external device by load analysis. The implantable device permanently rectifies energy provided to the receiving coil since the smoothing capacitor forms a short for alternating signals.

US 2009/0018599 Al relates to a cardiac stimulation system using leadless electrode assemblies, which can be selectively activated by means of a cable com- prising multiple transmitters individually associated with a particular electrode device. The cable has to be placed close to each electrode assembly for selective coupling only the associated one of the electrode devices. Implanting a cable, however, is disadvantageous in consideration of the above discussion. US 2006/0085041 Al relates to a leadless cardiac stimulation system for multi- site pacing, wherein multiple wireless pacing electrode assemblies are implantable at different sites of a heart. All electrode assemblies are charged simultaneously and can be addressed independently using different frequencies through a filter device to trigger pacing. The wireless pacing electrode assemblies are com- plex since they demand for at least a filter, a changeover switch as well as means for interpreting incoming frequencies and for controlling the switch based thereon. Further, increased energy consumption is caused since each electrode assembly is charged even if its activation it is not desired or intended. Object of the present is to provide a stimulation system or a method for delivering electrical impulses to multiple sites, wherein wireless electrode devices can be selected with a reduced complexity of the electrode device and/or with reduced losses due to leakage.

This object is achieved by a stimulation system according to claim 1 or by a method according to claim 22. Advantageous embodiments are subject of the subclaims.

According to a first aspect the present invention, a stimulation system, preferably a cardiac pacemaker, comprises at least two implantable electrode devices for generating electrical impulses. The electrode devices are configured as wireless units and are adapted to be supplied with energy exclusively in a wireless manner by means of a time- varying magnetic field.

According to a further aspect the present invention, The electrode devices are adapted to be controlled independently from each other by means of the time- varying magnetic field of different polarities associated with different ones of the electrode devices.

Using different polarities associated with different ones of the electrode devices for independently controlling different electrode devices allows for obtaining a small size, a cheap production as well as an improved reliability since there is no demand for a complex structures like a switch, control means for the switch or a filter, whose complexity can be quite high if high edge steepness is necessary for distinguishing several frequencies. For instance, a simple reed relay, an modified coil core or just choosing a particular orientation can be used for selecting electrode devices according to the present invention or groups thereof. The complexity of the electrode devices, thus, can be reduced significantly if a switch and associated control means can be avoided. According to a further aspect of the present invention, that can be realized independently as well, different ones of the electrode devices are adapted to be supplied independently from each other with energy by means of the time-varying magnetic field of different transmission characteristics associated with the different ones of the electrode devices. The electrode devices according to the present invention allow for selectively sourcing using different transmission characteristics. For instance, a tuned receiving coil, a simple filter, particular coil core or just a particular orientation can be used for selection of an electrode device and/or for blocking reception of en- ergy by the other electrode devices. Thus, the electrode devices according to the present invention can be selected without using a switch and associated control means. Further, the system can be adapted for activating different numbers of electrode devices without increased power consumption. The electrode device according to the present invention is cheap, provides a low complexity and is particularly reliable by omitting error prone components.

Supplying each electrode device any time consumes a large amount of energy which in parts is lost due to leakage. Using the inventive electrode devices which can be selectively supplied with energy allows for reducing power consumption since only the electrode devices currently needed have to be charged. In particular, the system according to the present invention can provide a mode for high stimulation energy, e.g. defibrillation, wherein a higher number of electrode devices are activated and a mode for low stimulation energy, e.g. for pacing, wherein just a few of the electrode devices have to be charged. Using the inven- tive electrode devices with a reduced complexity allows for selecting in particular a first, second or both first and second groups of electrode devices in a simple, reliable way.

The electrode device can be configured to be supplied with energy by means of the time-varying magnetic field of a particular transmission characteristic which is associated to this electrode device, which is different from that of at least one further electrode device, and/or which is exclusively specific to this electrode device. According to one aspect, an receiving means, in particular a coil, is configured to receive energy by means of the transmission characteristic being asso- ciated with this electrode device much more efficiently. Thus, hardly any energy is received by means of the time-varying magnetic field of a transmission characteristic being specific to a different electrode device.

According to a further aspect, the electrode device is configured to block the re- ceiving means, in particular coil, preferably such that prohibiting or stopping a current flowing from the receiving means to a rectifier, an energy buffer, elec- trodes or further components of the electrode device, in particular when the time- varying magnetic field does not comprise the transmission characteristic associated with the electrode device. Thus, the time-varying magnetic field of a transmission characteristic, which is different to the transmission characteristic which is associated with the electrode device, does not provide energy or provides hardly any energy to the electrode device, in particular compared to the time- varying magnetic field comprising the transmission characteristic associated with the electrode device. If the receiving means and/or current is blocked, in particular even if a induction voltage might occur in the receiving means, no or hardly any energy is withdrawn from the field and/or received by the electrode device. For instance, a means for blocking a current flow depending on the transmission characteristic, in particular a filter, can be connected to the receiving means, in particular coil, of the electrode device. The means for blocking preferably connects the receiving means to or disconnects the receiving means from the recti- fier and/or the electrodes, since any components placed between the receiving means and further components could consume energy, e.g., due to parasitic effects. Alternatively, the means for blocking can be placed in front of an energy storing means, in front of at least one electrode, or can connect the receiving means to a rectifier, to the energy storing means and/or the electrodes.

In the sense of the present invention, not receiving energy preferably covers receiving hardly any or a negligible amount of energy, since any conducting material might receive energy even if not intended. Preferably, energy provided by means of a time varying magnetic field different to that associated with the elec- trode device at least is not or to a negligible extend stored in an energy buffer of the electrode device, and/or is not provided via the electrodes of the electrode device, and/or is not provided to a rectifier of the electrode device. In particular, an electrode device receives more than 5, 10 or 20 times, preferably more than 50 times, in particular more than 100 times the energy from the time-varying magnetic field of the transmission characteristic being associated with it compared to a different transmission characteristic, preferably associated with a different electrode device. No, negligible or hardly any energy in the sense of the present invention or the maximum of energy received in spite of blocking current preferably is less than 5, 10 or 20 times, preferably less than 50 times, in particu- lar less than 100 times: lower than the energy received at the transmission characteristic associated with the present electrode device, and/or lower than deliv- ered via an electrical impulse, and/or lower than 1 μ], preferably less than 500 nJ, in particular less than 200 nJ or 100 nJ, and/or lower than 1 mW, preferably less than 500 μΨ, in particular less than 200 or 100 <W. The electrode devices are preferably adapted such that a time delay between two or more electrical impulses of different electrode devices can be obtained and/or controlled. This allows for providing an efficient stimulation which can be adapted to the natural movement or activation of muscle region. The electrode devices can be adapted to be controlled and/or supplied with energy by means of the time-varying magnetic field of different transmission characteristics.

Preferably, the transmission characteristics cover or are frequencies, and/or the at least two of the electrode devices are adapted to be each selective to and/or can each be selectively influenced by the time-varying magnetic field of different frequencies.

Alternatively or additionally, the transmission characteristics preferably cover or are polarities, and/or at least two of the electrode devices are adapted to be selective to and/or can each be selectively influenced by the time-varying magnetic field of different polarities.

According to the present invention, wireless electrode devices are used for gen- erating electrical impulses. These impulses can be used for stimulating, e.g., a heart, a tissue, a body or parts of it. These electrode devices are configured as wireless units and can be controlled and/or supplied with energy omitting a wire connection like a cable or lead. Thus, errors due to failure of a wire, cable or lead are avoided and the reliability of stimulation can be improved.

At least two, in particular separate, implantable electrode devices are used. These different electrode devices can be implanted in some distance to each other, e.g. on different sides or in different regions of a body, a heart or a tissue to be stimulated. This allows for generating electrical impulses at different sites, which in the following is referred to as "multi-site pacing". Moreover, at least two of the implantable electrode devices can be placed with a distance of at least 1 cm and/or less than 20 cm from each other, in particular on different sides and/or regions of a heart. Using at least two electrode devices enables a much more efficient stimulation. The present invention combines multi-site pacing and wireless electrode devices. By using wireless electrode devices, there is an ample scope for choosing suitable locations for implanting.

In particular, generation of electrical impulses by different ones of the electrode devices can be adapted to a natural behavior of stimulation. For example, a heart contracts at different areas at different times. According to the present invention, a sequence or order of electrical impulses, timing and/or a delay between electrical impulses generated by different ones of the electrode devices can correspond to a natural behavior, in parcitcular by synchronizing delivery of electrical impulses by different ones of the electrode devices depending on respective locations and/or to a movement, e.g., of the heart or to a signal corresponding there- to. Thus, the stimulation efficiency is increased significantly and an energy demand can be reduced.

The electrode devices preferably are adapted such that a time delay between two or more electrical impulses of different electrode devices can be obtained and/or controlled. This allows for synchronizing them. Alternatively or additionally, the electrode devices are adapted to be controlled and/or supplied with energy by means of the time-varying magnetic field of different transmission characteristics. Thus, the time delay can be controllable and/or modifiable by means of the time-varying magnetic field, preferably with different transmission characteris- tics.

In the sense of the present invention, the term "magnetic field" preferably covers electro-magnetic fields or waves. In particular, fields, waves or the like with any kind of magnetic component can be "magnetic fields" in the sense of the present invention. Furthermore, in the following "the magnetic field" is used in singular. However, the magnetic field can have different properties over time and in space, can comprise more than one (sub-) field and/or independent or superposed components and/or different transmission characteristics, in particular simultaneously or not. In the sense of the present invention, the term "time-varying magnetic field" preferably is related to one or more of the electrode devices or its location, in particular in an implanted or ready-to-use arrangement or condition. This means, a particular field, field strength, geometry or variation of the time-varying mag- netic field preferably is that of a position of the electrode device. Furthermore, it is preferred that the "magnetic field" reaches and/or affects at least one, preferably each one, of the electrode devices of the stimulation system. However, the magnetic field might affect different electrode devices in different manner, intensities and/or with different influence or effect on different electrode devices.

In the following, "transmission characteristics" of a magnetic field preferably relate to a field strength, to a geometry of the field, to a variation over time of the field and/or to a position of one or more of the electrode devices. In particular, a transmission characteristic is a characteristic of and/or affects the time-varying magnetic field strength or geometry of the magnetic field. The term "transmission characteristic" of the magnetic field preferably covers any characteristic assigned to the magnetic field with distinguishable states. Particularly preferably, transmission characteristics cover frequencies and/or polarities as explained in the following. However, further transmission characteristics might be, for exam- pie, particular directions, directivities, angles of transmission, foci, beam forms and/or field patterns. In particular, different transmission characteristics can be achieved using beam forming techniques.

According to the present invention, transmission characteristics particularly pref- erably are (characteristic) frequencies and/or polarities of the magnetic field.

In the sense of the present invention, a "frequency" of a magnetic field preferably is a variation of the field strength over time and/or at a location of one of the electrode devices. The magnetic field preferably has a significant amplitude at this frequency and/or comprises energy or is adapted to transfer energy at this frequency. For example, a significant amplitude can be greater than the thousand fold of the static magnetic field strength of the earth or can be greater than 100 μΤ, preferably greater than 1 mT, in particular greater than 5 or 10 mT. An advantage of using different frequencies for supplying particular electrode devices resides in the fact that a high number of different electrode devices or groups thereof can be separately supplied and/or activated. In particular, different filters, in particular a low pass filter and a high pass filter and, in particular if more than two electrode devices or groups thereof should be distinguished, band pass filters, can be used for blocking reception of energy at frequencies different to that the individual electrode device is selective to. Thus, no energy is withdrawn from the time-varying magnetic field unless it comprises the frequency the individual electrode device is selective to and the energy consumption is reduced, in particular if compared to systems, wherein each electrode device is charged first and only particular ones are selected afterwards for generating an electrical impulse.

Low pass filters and high pass filters can be realized much cheaper, less complex and with a smaller form factor compared to band pass filters. Thus, it is preferred for two electrode devices or two sourcing groups or control groups of electrode devices to use low pass filters for the one and high pass filters for the other. The cut-off frequency of the low pass filter preferably is lower, in particular at least factor 2, 4 or 8, than the cut-off frequency of the high pass filter. This allows for separately sourcing each one of the electrode devices or groups with less complex filters with low the edge steepness, in particular with filters of first or sec- ond order, since with increased distance between the frequencies selectivity of those filters can be sufficient and the complexity is further reduced. For more than two electrode devices or groups thereof, which are to be controlled and/or supplied separately, using band pass filters for the third and further is preferred, whose cut-off frequencies preferably are higher than the cut-off frequency of the low-pass filter and lower than the cut-off frequency of the high-pass filter. Further, low-pass and/or high-pass filters can be replaced by band-pass filters and optionally band-pass filters can be used only. However, by this measure the complexity of the respective electrode devices might be increased. Further, the complexity of the electrode device is reduced significantly compared to those systems, wherein each electrode device is charged first and only particular ones of the electrode devices are selected afterwards for generating an electrical impulse, since neither any switch nor any control means therefore is desired for the electrode device according to the present invention. Only a filtering means might be desired in both cases. However, a filtering or corresponding selection means regarding different transmission characteristics, in particular fre- quencies, according to the present invention can be obtained simply by tuning a receiving means of the electrode device, preferably by forming a resonant circuit with the receiving means, in particular a receiving coil . Preferably, simply a capacitor is assigned, added or connected to the receiving means for tuning or forming the resonant circuit, which preferably is selective to the transmission characteristic associated with the present electrode device. In systems wherein the electrode devices are supplied simultaneously, a filter separate from the receiving means is needed, the receiving means, thus, cannot be used which demands for additional parts and complexity to form a separate filter.

According to the present invention, a "polarity" of a magnetic field can be related to a spatial characteristic of the magnetic field, in the following referred to as "spatial polarity" and/or to a temporal characteristic of the magnetic field, in the following referred to as "temporal polarity" .

A "spatial polarity" of a magnetic field can be a field geometry or wave geometry, preferably a polarization or an orientation of oscillations and/or of field lines, in particular in a plane perpendicular to a direction of propagation, transmission, direction of travel, and/or to a transverse wave's direction of travel.

In particular, the spatial polarity can cover horizontal , vertical and/or circular polarizations or orientations of the magnetic field or its oscillations in a plane or the like, in the following referred to as "field polarity". An advantage of using field polarities for selecting and/or supplying particular electrode devices resides in the fact that choosing an orientations of the same or a similar type of electrode devices can be sufficient for achieving the desired selectivity. In particular, a coil or antenna with a directivity and associated electrodes can be sufficient and no controller, switch or the like are essential.

Alternatively or additionally, a spatial polarity according to the present invention relates to an orientation of a magnetic field source. In particular, a north and south pole of a magnetic field can be exchanged for changing the polarity. A polarity relating to different orientations of the magnetic poles of a magnetic field source in the following is referred to as "source polarity" . An advantage of using source polarities for selecting and/or supplying particular electrode devices resides in the fact that electrode devices can be identical or similar, wherein an orientation in space can be used for selecting electrode devices or a group thereof. For instance, a simple single reed switch or a particular coil core can be used.

A "temporal polarity" of a magnetic field according to the present invention preferably is a polarity that relates to a particular time-variation of the magnetic field, in particular of the magnetic field strength and/or at the location of an elec- trode device.

A magnetic field can increase or decrease over time. An increasing field strength over time has a positive slope or gradient and/or a decreasing field strength over time has a negative slope or gradient. Hence, the magnetic field can have differ- ent polarities in the meaning of slopes or gradients over time, in particular of a varying field strength, with different signs, which in the following is referred to as "gradient polarity".

An advantage of using gradient polarities for selecting and/or supplying particu- lar electrode devices resides in the fact that electrode devices can be identical or similar, wherein an orientation in space can be used for selecting electrode devices or a group thereof. For instance, a diode in series to a receiving coil of the electrode device can be used. A magnetic field ramp induces a current of different directions if electrode devices are differently orientated. Thus, the diode can be used for blocking the induced current in one and passing in an other electrode device, and vice versa for another or the opposite gradient polarity.

Alternatively or additionally, the magnetic field in addition to a time-variable component can comprise an, in particular at least temporarily, time-invariant component which is termed offset. In particular, an offset is a static magnetic field that is added to the time-varying magnetic field. Thus, a static and a time- varying magnetic field can be superposed. When added to the offset, the time- varying component of the magnetic field, even if it is alternating, does not need to change the source polarity. Hence, the magnetic field can have a polarity in the sense of an offset, which can have different source polarities (orientations) and/or field strengths, in the following is referred to as "offset polarity" . An advantage of using offset polarities for selecting and/or supplying particular electrode devices resides in the fact that electrode devices can distinguished, e.g., by using different reed switches for blocking reception of energy. This allows for a simple and cheap construction of the electrode devices.

Further, different polarities can be thresholds in the form of different minimum field strengths. An advantage of using thresholds for selecting and/or supplying particular electrode devices resides in the fact that coil cores with different switching properties, in particular Wiegand wires, can be sufficient for selecting particular ones or groups of electrode devices.

Preferably, time-varying magnetic fields of different polarities cover or are time- varying magnetic fields of at least one of a spatial polarity, temporal polarity, field polarity, source polarity, gradient polarity, offset polarity and/or field strength threshold.

In the sense of the present invention, a "negative magnetic field" or a "negative field strength" preferably is an magnetic field of an absolute value of a field strength, wherein poles are changed, i.e. a north pole is replaced by south pole and vice versa. If a magnetic field is generated by a current flow, e.g. through a coil, a negative field strength can correspond to and/or can be generated by inverting the direction of the current flow. It is particularly preferred that different electrode devices can be controlled, triggered and/or supplied with energy independently. Then, electrical impulses can be generated at different times, i.e. with a particular time delay between generation of electrical impulses of the different electrode devices. This allows for an improved synchronization of stimulation. Impulses generated by the electrode devices.

The electrode devices are supplied with energy exclusively in a wireless manner. The electrode devices preferably are passive or do not make use of a battery. This allows for a small shape and several, in particular two, three or more elec- trode devices can be used or placed even if little space is available, which further improves the stimulation efficiency. Moreover, locations for implanting electrode devices are not depending on positions of veins or the like.

The system according to the present invention allows for improved effectively and efficiency stimulating by using at least two wireless electrode devices for multi-site pacing, in particular wherein the electrode devices are synchronized by realizing a delay and/or by using different transmission characteristics for controlling and/or supplying. Moreover, the risk of failure of a wire, cable or lead is avoided.

A further aspect of the present invention, which can be realized independently as well, relates to a method for operating at least two implantable electrode devices for generating electrical impulses in a stimulation system, in particular in a cardiac pacemaker system. The electrode devices are supplied with energy in a wireless manner by means of a time-varying magnetic field.

Electrical impulses are generated by different ones of the electrode devices with a particular time delay. Alternatively or additionally, a first one of the electrode devices is controlled and/or supplied with energy by means of a time-varying magnetic field of a first transmission characteristic and a second one of the electrode devices is controlled and/or supplied with energy by means of a time- varying magnetic field of second, different transmission characteristic. Further electrode devices can be provided, wherein these can be controlled and/or supplied with energy by means of a time-varying magnetic field of the first, the sec- ond or a transmission characteristic different to the first and the second one.

The proposed stimulation system and/or one or more of the electrode devices of the stimulation system alternatively or additionally can be used and/or adapted to convert the self-action of the heart, in particular a movement of the heart and/or electrical activity of the heart, into a magnetic impulse or an other, in particular electrical , signal which can preferably be sent and/or detected by the stimulation system and the electrode device and/or an other receiving or control unit.

As has already been explained, the implantable electrode device is used in par- ticular for generating electrical signals or impulses to stimulate a heart. However, the present invention is not restricted to this. Rather, the electrode device and/or the stimulation system can generally generate any type of electrical impulse or electrical signal, in particular in the human or animal body. The terms "electrode device" and "the stimulation system" should accordingly be understood in a very general sense so that other applications and uses, such as for example to influence the brain, can be understood.

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 the following description of preferred embodiments with reference to the drawings.

In the figures:

Fig. 1 is a schematic view of a stimulation system according to the present invention;

Fig. 2 is a schematic view of one of the electrode devices according to the present invention;

Fig. 3 is a simplified schematic view of a further embodiment of the stimulation system according to the present invention;

Fig. 4 is a simplified schematic view of a further embodiment of the stimulation system according to the present invention;

Fig. 5 is a diagram of the magnetic field and induction voltages assigned to electrode devices; Fig. 6 is a diagram of the magnetic field and induction voltages assigned to electrode devices; Fig. 7 is a simplified schematic view of a further embodiment of the stimulation system according to the present invention; and

Fig. 8 is a diagram of the magnetic field and induction voltages assigned to electrode devices.

In the figures the same reference numerals are used for the same parts or parts of the same type, components or the like, wherein corresponding or similar advantages and properties are obtained even if a repeated description is omitted. Furthermore, in the following reference is made to definitions and explanations given above, in particular regarding transmission characteristics and various categories and implementations of different transmission characteristics.

Fig. 1 is a schematic view of a proposed stimulation system 1 , which in particular is configured as or works as a cardiac pacemaker in the example shown. However, the present invention is not restricted to this. For example, the stimulation system 1 can additionally or alternatively operate as a defibrillator or can be used for other purposes and at other locations in the human or animal body 2, including deep brain stimulation or in different fields of technology, for instance in production, for electroanalysis, electrolysis or the like, e.g., in a vessel, chamber, pipe and/or different inaccessible areas.

The stimulation system 1 preferably comprises at least two implantable electrode devices 3 for generating electrical impulses I. These can be implanted close to or inside a heart 4, preferably at different sides of it. At least one control device 5 can be part of the stimulation system 1 and preferably is adapted to generate a time-varying magnetic field H for controlling, triggering and/or supplying the electrode devices 3 with energy, in particular using a sending means 6. The control device 5 can be implantable. In the example shown, the control device 5 is implanted between the thoracic cage 7 and the skin 8. Alternatively or addition- ally, the control device 5, e.g., can be placed in the area of a shoulder and/or out- side the body 2 as indicated using dashed lines. The control device 5 can be implanted like common cardiac pacemakers or those cited in the introductory part as well. More than one control device 5 can be provided in the system 1 as well. The electrode devices 3 in the stimulation system 1 preferably are configured as wireless units and are adapted to be supplied with energy exclusively in a wireless manner by means of a time-varying magnetic field H. Wireless electrode devices 3 preferably do not comprise any error-prone cable or lead. By supplying the electrode devices 3 with energy by means of the time-varying magnetic field H, there is no demand for a battery or the like to be used inside the electrode devices 3 and, thus, a compact size can be achieved and the lifetime is not limited by an energy storing device.

Depending on the configuration, the electrode devices 3 can also be used inde- pendently of the control device 5. For example, it is possible in principle that the electrode devices 3 can be supplied with energy and/or controlled by another device, optionally even by a nuclear spin tomograph or the like, in particular with suitable matching. Thus, further possible uses are obtained which go substantially beyond the possible uses of conventional cardiac pacemakers or other stimulation systems. The control device 5 can be used independently as well , e.g. for selectively supplying other components using different transmission characteristics.

The electrode devices 3 can be implanted close to or inside the heart 4 or in the heart muscle of a patient, whose body 2 is shown only schematically and in part. The electrode devices 3 can be implanted, for example, as described in US 5,41 1 ,535 A.

The control device 5 can comprise sending means 6, in particular a coil or an an- tenna, for generating and/or transmitting the time-varying magnetic field H. Preferably, the control device 5 adapted for generating the time-varying magnetic field H reaching at least one of the electrode devices 3, preferably both, if available further and/or all of the electrode devices 3. An optional third electrode device 3 is shown using dashed lines. Fig. 2 shows a schematic view of a preferred embodiment of one of the electrode devices 3. According to one aspect of the present invention, at least one, both or all of the electrode devices 3 is or are adapted to deliver an electrical impulse I, preferably electrical impulses I comprising a sequence of pulses or oscillations. Preferably, at least one, both or all of the electrode devices 3 of the system 1 can comprise at least two electrodes 1 1 for delivering electrical impulses I, preferably to an area, in particular of a body 2 or tissue, surrounding the electrode device 3, in particular for delivery to a surrounding tissue and/or body 2. The electrode device 3 preferably is constructed only of passive structural elements and/or without an energy storing device such as a battery. Nevertheless, in a preferred alternative, the electrode device 3 comprises an energy buffer, in particular for storing energy received in wireless manner and/or a capacitor. It is preferred that at least one, both or all of the electrode devices 3 are electrically passive, e.g., do not comprise a battery, rechargeable battery or the like. It is preferred that at least one, two or all of the electrode devices 3 are adapted to buffer electrical energy, preferably by means of a capacitor, wherein the total capacity per electrode device 3 is less than 50 μ¥, preferably less than 10 μ¥, in particular less than 1 μ¥. Alternatively or additionally, at least one, both or all of the electrode device 3 is or are each adapted to buffer a total amount of energy for delivery of a maximum of ten electrical impulses I, preferably two electrical impulses I, in particular one electrical impulse I. An advantage of omitting a battery and/or using only a small buffer resides in a reduced volume consumption and regarding the energy supply unlimited working time.

In the example shown in Fig. 2, the electrode device 3 preferably comprises a receiving means 9, in particular comprising or composed of a coil 10 and/or an antenna. The receiving means 9 can be selective to magnetic field H acting on the electrode device and/or affecting the electrode devices 3 and/or selectively influ- enceable, in particular controllable and/or suppliable, by different transmission characteristics of the time-varying magnetic field H. Thus, different ones of the electrode devices 3 are selective to different transmission characteristics. According to one aspect of the present invention, at least two or all of the electrode devices 3 are synchronizable, in particular wherein at least one of the elec- trode devices 3 is configured for delaying generation or for delaying delivery of an electrical impulse I with reference to generation or delivery of an electrical impulse I by a different one of the electrode devices 3. One or more of the electrode devices 3 can be synchronized to an natural activity of a heart, a reference signal corresponding to the natural activity of the heart and/or corresponding to further different measurement results or the like. Further, the electrode devices 3 can be used in different fields of technology as well . The electrode devices 3 can be synchronized to parameters, measurement results or further values, changes and/or to reaching or passing a reference value or range.

Preferably, the receiving means 9 and/or electrode device 3 is or are selective and/or exclusively selective by being adapted to receive and/or to reject commands and/or energy provided by means of the time varying-magnetic field H depending on its transmission characteristic.

In particular, the receiving means 9 is adapted to receive and/or to reject commands and/or energy provided by means of a time-varying magnetic field H of a particular frequency and/or polarity. Alternatively or additionally, the receiving means 9 can be adapted such that receiving and/or rejecting of commands and/or energy depends on a spatial orientation of the receiving means 9 or coil 10. Receiving means 9 can comprise or can be formed by coil 10.

One, two or more of the electrode devices 3 can comprise a filtering means 12 which preferably is selective to a transmission characteristic of the time-variable magnetic field H or to a signal, voltage or current corresponding thereto. Preferably, the filtering means 12 is adapted to block and/or to pass commands and/or energy provided by means of the time varying magnetic field H, preferably depending on the transmission characteristic of the time-varying magnetic field H, in particular on the frequency and/or polarity of the time-varying mag- netic field H, a corresponding signal , current value or the like.

One, two or more of the electrode devices 3 can comprise a rectifier 13 for rectifying energy, in particular received by the receiving means 9, converted to and/or in the form of a current or voltage. This allows for converting energy for buffer- ing and/or forming an electrical impulse I by the electrode device 3. One, two or more of the electrode devices 3 can comprise a delay means 14 which, preferably, is adapted to delay generation and/or delivery of an electrical impulse I, in particular relating to supplying the electrode device 3 with energy and/or relating to generation and/or delivery of an electrical impulse I by a dif- ferent one of the electrode devices 3.

One, two or more of the electrode devices 3 can comprise a pulse forming device 15 which, preferably, comprises an energy buffer, in particular a capacitor, and optionally a resistor. Additionally or alternatively, the pulse forming device 15 can comprise an inductor or a coil that can be used for pulse forming. The pulse forming device 15 is adapted for forming or reforming a pulse-like induction voltage which is generated or delivered under certain circumstances, as will be described in further detail hereinafter, by the receiving means 9 or coil 10. The reformed electrical impulse I can than be output for stimulation via the connected electrodes 1 1 .

The coil 10 can be configured such that a pulse-like deduction voltage is generated when a minimum field strength of the time-varying magnetic field H acting on the electrode device 3 or the coil 10 is exceeded. For this purpose, the coil 10 can comprise a coil core 16 which can comprise magnetic properties, which can cause an abrupt change in the magnetization. This abrupt change in the magnetization or magnetic polarization results in a desired pulse-like induction voltage in the allocated coil 10. In particular, the core 16 can comprise a so-called Wie- gand wire, meta materials, a combination of hard and soft magnetic materials and/or multiple sheets of different materials. Alternatively or additionally, a read relay in series with at least one electrode 1 1 can be used for generation and/or delivery of the electrical impulse I or for blocking it.

A controller 21 , in particular a processor, logical circuit, demodulating means or the like, can be used to interpret information, in particular control commands provided by the magnetic field H, for controlling the electrode device 3. For example, information about a particular delay can be transmitted to one of the electrode devices 3. The controller 21 preferably is adapted for intepretation of a received signal and, e.g., can configure the delay means 14 accordingly. Alterna- tively or additionally, the controller 21 can actively control the rectifier 13 leading to optimized energy efficiency. The controller 21 can be adapted to receive a control signal with information about a filter characteristic, in particular by the time-varying magnetic field H and/or from the control device 5. The filtering means 12 can be adapted by the controller 21 to provide a characteristic corresponding to this information. The pulse forming device 15 can be influenced by the controller such that a different pulse form or shape is generated.

Preferably, each one of the electrode devices 3 comprises at least one electrode 1 1 and a receiving means 9. Each one of the other components of the electrode device 3 of Fig. 2 is optional. In particular, the filtering means 12 and/or the pulse forming device 15 might not be necessary if a selectivity and/or pulse forming is realized by the receiving means 9 and/or rectifier 13 or vice versa. Different ones of the electrode devices 3 of the system 1 can have different configurations regarding the optional components. The electrode devices 3 preferably are very compact and in particular are configured substantially rod-shaped or cylindrical. In the example shown in Fig. 2, the length 10 to 20 mm, in particular substantially 15 mm or less. The diameter is preferably at most 5 mm, in particular substantially 4 mm or less. A retaining device can be attached to the electrode device 3, preferably an anchor or a screw which allows the electrode device 3 to be anchored in the heart muscle or close to it.

The electrode device 3 of Fig. 2 preferably is configured to generate electrical impulses I for the desired stimulation or signal generation. The electrical im- pulses I are delivered, for example, via electrodes 1 1 . In the example shown, the electrodes 1 1 are located on opposite sides of the electrode device 3. However, the electrodes 1 1 can be arranged concentrically or otherwise, for example, at one or at the opposite ends of the electrode device 3 or its housing 17. This housing 17 preferably is made with insulating material. The electrode 1 1 preferably is integrated in the electrically insulating housing 17 or attached thereon. Alternatively or additionally, spiral-like electrodes 1 1 can be used. The electrodes 1 1 preferably are electrically connected to the receiving means 9, in particular via one or more of the optional components. The electrode devices 3 preferably are placed in some distance D to each other, e.g. as shown in Fig. 1. In particular, the electrode devices 3 are placed at the dis- tance D of at least 1 cm, preferably 2 cm, 3 cm or more and/or less than 20 cm, preferably 15 cm, 10 cm or less. Within this distance, the electrode devices 3 can act on a common area of the body 2 in a particular efficient manner.

The electrode devices 3 preferably are adapted to generate an electrical impulse I after a control command, a triggering command and/or energy has been transmitted to the electrode device 3 by means of the time-varying magnetic field H. The electrical impulse 1 preferably is a voltage or current between at least two electrodes 1 1 of the electrode device 3 and can have different shapes. Preferably, the electrical impulse I is configured to form an action potential or stimulation for nerves or muscles.

In particular, the electrical impulse I can comprise a substantially rising slope and a substantially falling slope. Optionally, between rising and falling slope, the electrical impulse I can comprise a substantially constant behavior. Alternatively or additionally, the electrical impulse I can comprise alternating voltages and/or currents, in particular with an additional offset. However, different shapes of electrical impulses I can be used as well. In particular, a shape of the electrical impulse I can correspond to the field strength of the time-varying magnetic field H.

The stimulation system 1 can comprise a control device 5, which optionally can be implanted. The control device 5 preferably is adapted for controlling, supplying with energy and/or synchronizing at least two electrode devices 3. In particular, the control device 5 is adapted for controlling and/or transmitting energy to at least one of the electrode devices 3 by means of the time-varying magnetic field H of a transmission characteristic which, preferably, is exclusively specific to the first one of the electrode devices 3 of the system 1.

The control device 5 can be adapted to generate the time-varying magnetic field H of different transmission characteristics. For example, the control device 5 or the sending means 6, in particular a coil and/or antenna is adapted to generate the time-varying magnetic field H, in particular if a corresponding electrical signal is provided to the sending means 6. In a preferred embodiment, control device 5 is adapted for generating time- varying magnetic fields H of different transmission characteristics, in particular frequencies and/or polarities, which, preferably, correspond to the frequencies and/or polarities associated with different electrode devices 3 of the stimulation system 1 . The control device 5 can be configured to store energy and/or to be inductively charged, in particular in the implanted state. For example, the control device 5 can be charged using the sending means 6 as a receiver.

The control device 5 can be adapted to generate trigger pulses or pulse se- quences, in particular a sine and/or saw tooth shaped time-varying magnetic field H. The control device 5 particularly preferably can generate time-varying magnetic fields H of at least two different transmission characteristics, in particular at least two different transmission characteristics of the same type and/or at least two different frequencies, source polarities, field polarities, gradient polarities, offset polarities, spatial polarities, temporal polarities, directivities and/or directions.

The control device 5 can be adapted for controlling and/or transmitting energy, in particular exclusively, to at least one of the electrode devices 3 and/or for gen- erating the time-varying magnetic field H. Particularly preferably, the control device 5 is adapted to generate a time-varying magnetic field H of at least two different frequencies and/or of at least two different polarities. Alternatively or additionally, the control device 5 can be adapted to generate any one of the transmission characteristics which is exclusively specific to one of the electrode devices 3.

More specifically, the control device 5 can be adapted to generate at least two differently directed time-varying magnetic fields H, i .e. magnetic fields H of different spatial shapes, and/or time-varying magnetic fields H of different polariza- tions, e.g. a horizontal, vertical and/or circular polarized time-varying magnetic field H. The control device 5 can be adapted to generate different offsets of magnetic fields, in particular with different signs, directions and/or with an at least in parts constant behavior. The mentioned time-varying magnetic field H with different transmission characteristics can be used for addressing, controlling, trig- gering and/or supplying with energy of different of the electrode devices 3 selectively. The control device 5 can be adapted to generate a time-varying magnetic field H of different transmission characteristics in a synchronized manner, for example with particular time delays T or the like. For example, different electrode devices 3 are intended to deliver electrical impulses I at different times in a particular sequence or the like. Then, the control device 5 can generate a first time-varying magnetic field H of a first transmission characteristic and, after a particular time delay T and/or with a command for delaying, a second time-varying magnetic field H of a different transmission characteristic, preferably wherein the trans- mission characteristics are different and/or specific to the respective electrode devices 3 that are intended to deliver an electrical impulse I. This allows for activating, i.e. controlling and/or supplying with energy, of different electrode devices 3 at different times. The stimulation system 1 in Fig. 1 comprises at least two implantable electrode devices 3 for generating electrical impulses I. The electrode devices 3 preferably are placed in some distance D to each other and can be controlled, triggered and/or supplied with energy such that an particular time delay T can be achieved between delivery of an electrical impulse I by the first one of the electrode de- vices 3 and delivery of an electrical impulse I by the second one of the electrode devices 3.

The electrode devices 3 are supplied with energy in a wireless manner by means of the time-varying magnetic field H. Electrical impulses I can be generated by different ones of the electrode devices 3 with a particular time delay T. Alternatively or additionally, a first one of the electrode devices 3 is controlled and/or supplied with energy by means of a time-varying magnetic field H of a first transmission characteristic and a second one of the electrode devices 3 is controlled and/or supplied with energy by means of a time-varying magnetic field H of a second, different transmission characteristic.

In particular, a first one of the electrode devices 3 can be configured to generate an electrical impulse I if the time-varying magnetic field H has a first transmission characteristic, and a second one of the electrode devices 3 is configured to generate an electrical impulse I if the time-varying magnetic field H has a different, second transmission characteristic. A transmission characteristic according to the present invention, in particular as defined in the beginning, preferably is a characteristic of the time-varying magnetic field H that allows for selective transmission of energy and/or of control commands, to the electrode devices 3. Thus, the electrode devices 3 can be activated and/or triggered independently.

The electrode devices 3 preferably are adapted such that the time delay T between two or more electrical impulses I of different electrode devices 3 can be obtained and/or controlled. Preferably, the electrode devices 3 are supplied with energy and/or controlled to deliver electrical impulses I in a synchronized manner, in particular with a delay between supplying, controlling and/or delivery of electrical impulses I by different ones of the electrode devices 3. The time delay T can be controlled and/or modified by means of the time-varying magnetic field H, preferably of different transmission characteristics, in particular different frequencies and/or different polarities.

In a first preferred embodiment, the control device 5 generates a time-varying magnetic field H with a first transmission characteristic and after a time delay T of a second, different transmission characteristic. The electrode devices 3 are adapted to be controlled, triggered and/or supplied with energy by means of a time-varying magnetic field H of different transmission characteristics. In particular, a first one of the electrode devices 3 is selective to the first and a second electrode device 3 is selective to a second transmission characteristic. Then, the first electrode device 3 is activated to generate an electrical impulse I if the time- varying magnetic field H of the first transmission characteristic is generated and the second one of the electrode devices 3 is activated to generate an electrical impulse I if the time-varying magnetic field H of the second transmission characteristic is generated. Thus, the time delay T can be controlled and/or modified by means of the time-varying magnetic field H with different transmission characteristics.

In a second preferred embodiment, the control device 5 generates the time- varying magnetic field H with a first transmission characteristic and with a sec- ond, different transmission characteristic, e.g. simultaneously. The electrode devices 3 are adapted to be controlled, triggered and/or supplied with energy by means of a time-varying magnetic field H of different transmission characteristics. In particular, a first one of the electrode devices 3 is selective to the first and a second electrode device 3 is selective to the second transmission characteristic. In addition, at least one of the electrode devices 3 comprises a delay means 14. In the example shown, the second one of the electrode devices 3 comprises a delay means 14. Then, the first electrode device 3 is activated to generate an electrical impulse I if the time-varying magnetic field H of the first transmission characteristic is generated. The second one of the electrode devices 3 is activated to generate an electrical impulse I after a time delay T if the time-varying mag- netic field H of the second transmission characteristic is generated. The time delay T can be predefined by the delay means 14 and/or can be controlled by the time-varying magnetic field H of the second transmission characteristic. Thus, the time delay T can be controlled and/or modified by means of the time-varying magnetic field H with different transmission characteristics.

Both embodiments can be combined. Then, a time delay T between generation of electrical impulses I by different ones of the electrode devices 3 can be controlled either by a delay means 14, by a delay between generation of the time- varying magnetic field H of the first and the second transmission characteristic, or by a cumulative delay, in particular a sum or difference of delays provided by delay means 14 and by a delay between different transmission characteristics of the time-varying magnetic field H. If two or more delay means 14 are active in different of the electrode devices 3, a delay between generation or delivery of electrical impulses I by them in particular is a difference in delay. Delaying all the electrode devices 3 of a system 1 might be useful for synchronizing generation or delivery of electrical impulses I and a movement of a heart 4 or the like.

The electrode devices 3 are controlled to deliver electrical impulses I, preferably to the surrounding area, body 2, heart 4 and/or tissue. According to one aspect of the present invention, it is preferred that the electrode devices 3 are supplied with energy in a wireless manner separately for each delivery of an electrical impulse I. At least one of the electrode devices 3 can be adapted to generate an electrical impulse I corresponding to the time-varying magnetic field H, in particular to the time-varying field strength over time of the time- varying magnetic field H. This allows for an improved efficiency and/or stimulation effectivity. A further aspect of the present invention relates to measurement or characterization of different ones of the electrode devices 3 of the system 1 . It is preferred that the system 1 , in particular the control device 5, is adapted to estimate transmission characteristics suitable for selectively controlling and/or supplying with energy of different ones of the electrode devices 3. A transmission characteristic of a first, a second and/or further one of the electrode devices 3 can be estimated, preferably based on a behavior, location and/or orientation of the electrode devices 3, wherein, preferably, the estimated transmission characteristics is or are used for selectively controlling and/or supplying the electrode devices 3.

Preferably, at least one, two or all of the electrode devices 3 is or are adapted to be controlled and/or supplied with energy exclusively by means of a time- varying magnetic field H with different transmission characteristics each being specific to respective ones of the electrode devices 3.

In the following, preferred aspects of the present invention are discussed in detail with reference to system 1 according to different embodiments depicted in Fig. 3, 4 and 7. These embodiments are reduced to a minimum. However, it has to be understood that the system 1 , the electrode devices 3 and/or the control device 5 can be realized as previously discussed.

Fig. 3 shows a preferred embodiment of stimulation system 1 , wherein a control device 5 and electrode devices 3 are shown in a simplified, schematic and sectional manner, the electrode devices 3 in particular reduced to their receiving means 9. In the example according to Fig. 3, an unidirectional means 18, in particular a diode or the like, is provided. Preferably, the unidirectional means 18 allow for current flow from the receiving means 9 and/or for generating an electrical impulse I in one particular direction and blocks current flow and/or generating an electrical impulse I in the opposite direction. Furthermore, the unidirec- tional means 18 of the first and the second one of the electrode devices 3 have opposite directions.

The time-varying magnetic field H, which can be generated by a control device 5, preferably acts on both of the electrode devices 3. For example, the time- varying magnetic field H causes induction voltages and/or currents 19, 20 in the receiving means 9 of both the electrode devices 3 as indicated using arrows in Fig. 3. The first one of the electrode devices 3 has an unidirectional means 18 which blocks the induced voltage and/or current 19. In contrast, the unidirectional means 18 of the other one of the electrode devices 3 allows for current 20 flowing due to the opposite orientation of unidirectional means 18. Hence, the unidirectional means 18 of the first one of the electrode devices 3 blocks controlling, supplying with energy and/or generation of an electrical impulse I, and in the second one of the electrode devices 3, the unidirectional means 18 allows for current flow 20 and, thus, the second electrode devices 3 can be controlled, triggered and/or supplied with energy for generating an electrical impulse I.

Consequently, the first one of the electrode devices 3 blocks generation of delivery of an electrical impulse I and the second one of the electrode devices 3 can generate an electrical impulse I, as long as a time-varying magnetic field H of a first transmission characteristic, in a particular a first polarity, is provided, wherein preferably the first one of the electrode devices 3 is selective (selectively blocking) and the second one of the electrode devices 3 is selective (selectively accepting) regarding this transmission characteristic.

With a different transmission characteristic, in particular (gradient) polarity, of the time-varying magnetic field H, the induced voltage and/or current flow has an opposite direction and, thus, the first one of the electrode devices 3 can operate and the second one of the electrode devices 3 is blocked, or vice versa. Thus, the electrode devices 3 can be controlled, triggered and/or supplied with energy separately and/or independently by means of time-varying magnetic fields H of different transmission characteristics, in particular (gradient) polarities.

In the example shown in Fig. 3, the electrode devices 3 in particular are selective to different gradient polarities, in particular signs of gradients or slopes over time of a varying field strength. Alternatively or additionally, different offset polari- ties, in particular orientations of a static magnetic filed added to the time-varying magnetic field H can be used.

In Fig. 4, receiving means 9 of two different electrode devices 3 are orientated in a different ways. In particular, a second one of the electrode devices 3 is orien- tated at least basically perpendicular to a first one of the electrode devices 3. Dif- ferent field polarities, in particular polarizations, of the time-varying magnetic field H can be generated by the control device 5 or the like.

The time-varying magnetic field H of a particular field polarity, e.g. orientation and/or polarization, is configured such that it can be used to control, trigger and/or supply at the first one of the electrode devices 3. The second one of the electrode devices 3 is not controlled triggered and/or supplied with energy due to the different orientation, in particular wherein no significant current 19 and/or voltage is induced or received due to the orientation. In particular, the receiving means 9 of different ones of the electrode devices 3 are orientated such that a time-varying magnetic field H of a different orientations and/or polarizations can be found and/or are used wherein induction voltages are caused in only one of the electrode devices 3 each. Thus, using a first field polarity can be used for generating an electrical impulse I by the first one of the electrode devices 3 and a second, different, in particular linear independent, field polarity can be used for generation an electrical impulse I by the second one of the electrode devices 3.

In Fig. 5 a) a particular example of variation in time of a time-variable magnetic field H and/or of a corresponding current C, in particular a current C of a control device 5 or a sending means 6, is shown. This example can be related to a system 1 of Fig. 3, for instance.

In time span t, , the field strength is increased with a first gradient g, , in particular between 1 T/s to 10⁴ T/s. In the following time span t₂, the field strength is de- creased with a gradient g₂, that, preferably, is smaller than the first gradient g in particular by a factor of two, five, ten or higher. In optional time span t₃, the field strength is about 0. In the following time span t₄, the field strength is decreased with a gradient g₃, whose absolute value can be similar or identical to that of time span t, and, preferably, has a different sign, i.e. a "negative" field strength in the sense of an absolute value and a changed polarity (source polarity). In time span t₅, the field strength is increased with a gradient g₄ that can be similar to the gradient g₂ of time span t₂, preferably with a different sign. Thus, the variation of the magnetic field H in time comprises a rising gradient g, and a falling gradient g₃ in time spans t, and t₄, respectively. The time-variable magnetic field H of Fig. 5 a) is provided to at least two different ones of the electrode devices 3 of the stimulation system 1 . These electrode devices 3 can be controlled, triggered and/or supplied with energy separately, independently and/or with a particular time delay by means of the time-varying magnetic field H of different transmission characteristics. In the present example, different transmission characteristics are provided as gradient polarities by the gradients g, to g₄ of different signs to the electrode devices 3, in particular to those of Fig. 3. Each one of the electrode devices 3 is adapted to receive or block energy and/or commands provided by the time-varying magnetic field H depend- ing on the respective transmission characteristic.

In Fig. 5 b), an induction voltage U, or a current received by a fist one of the electrode devices 3 is depicted. This fist one of the electrode devices 3 is influ- enceable and/or selective to a particular sign and/or an absolute value of a gradi- ent of a magnetic field strength of the time-varying magnetic field H. For example, the first one of the electrode devices 3 comprises an unidirectional means 18 like the electrode devices 3 of Fig. 3. The first one of the electrode devices 3 in the present example is adapted to be influenceable and/or selective to positive gradients. During a steep, rising gradient gi in time span t, , a high induction volt- age or current 20 is generated, which can be used for generating an electrical impulse I. During time span t₄, receiving of energy and/or a command, in particular a corresponding induction voltage Uj or current 19, is blocked, in particular by the unidirectional means 18. Thus, the first one of the electrode devices 3 is selective to a particular gradient polarity of the time-variable magnetic field H.

A second one of the electrode devices 3 is influenceable and/or selective to a different polarity and, thus, can be controlled, triggered and/or supplied with energy by means of a time-varying magnetic field H of a different transmission characteristic, in particular inverse gradient polarity. Fig. 5 c) shows a respective induc- tion voltage U₂. During time span tj, an induction voltage is blocked by the second one of the electrode devices 3. During time span t₄, no blocking is provided and, thus, the second one of the electrode devices 3 can be controlled, triggered and/or supplied with energy for generating an electrical impulse I. In particular, the induced voltage U₂ can be used for generating or as an electrical impulse I. Consequently, different gradients, in particular gradients of field strength and/or with different signs, can be used for selectively controlling, triggering and/or supplying with energy of different ones of the electrode devices 3. In particular, different ones of the electrode devices 3 comprise opposite behavior with respect to transmission characteristics, in particular gradient polarities, of the time- varying magnetic field H. Moreover, a time delay I can be achieved as depicted by the arrow in Fig. 5.

As can be seen from Fig. 5, the electrode devices 3 can be adapted such that the gradients with smaller absolute values, like in time span t₂ and t₅, do not have a significant influence to the electrode devices 3, in particular cannot be used to generate an electrical impulse I. This allows for reduction of a current for generating the time-varying magnetic field H if a delay is needed which is at least a factor of 2, 5 or 10 higher than the time span for providing the electrode devices 3 with control signals and/or energy. Alternatively or additionally, gradients g, and g₂ of time spans t, and t₂ can be repeated to selectively supply and/or control the first one of the electrode devices 3 without activating the second one.

The time-varying magnetic field H of different transmission characteristics, in particular of different gradient polarities according to Fig. 5, can allow for synchronizing of different electrode devices 3. In particular, a time delay T between an electrical impulse I of the first and the second one of the electrode devices 3 can be modified by increasing or decreasing the time span t₃. Alternatively or additionally, the order of impulse I delivery by the first and the second one of the electrode devices 3 can be exchanged by switching the sign of the gradients g, , g₃, by replacing the gradients g, , g₂ of the time spans t, and t₂ with the gradients gi , g₄ of time spans t₄ and t₅ or the like.

The above embodiment particularly applies when saturation effects are signifi- cant, magnetic field H varies quite slowly, and/or if a large amount of energy is obtained from the receiving means 9. According to a further aspect of the present invention, in particular when rapidly varying magnetic fields H are used and/or saturation effects are negligible, different electrode devices 1 can be selected independently by different source polarities, i.e., by changing the polarity of the time-variable magnetic field H and/or of a corresponding current C, in particular a current C of control device 5 or sending means 6. Further, choosing different gradients does not need to be necessary.

Providing the sending means 6 with a positive voltage leads to a corresponding increasing strength of current C and/or field strength of the time-varying magnetic field H. Deactivating the voltage leads to a corresponding decreasing strength of current C and/or field strength of the time-varying magnetic field H, preferably down to zero without zero-crossing. The time-varying magnetic filed H preferably acts on different electrode devices 3, in particular having differently directed diodes in series with their receiving means 9, for example as depicted in Fig. 3.

Rising and falling field strengths without changing the source polarity can induce corresponding increasing and decreasing currents 19, 20 to the electrode devices 3. However, preferably no change in direction of this current occurs, in particular if changing the filed strength is sufficiently fast. The current preferably differs in amplitude only, without changing its sign as long as the source polarity, i.e. the pole orientation, does not change.

A fist electrode device 3 preferably blocks the current 19 in a first direction and a second electrode device 3 does not block the current 20 in this direction. Thus, the second electrode devices 3 can be selected, in particularly selectively controlled and/or supplied and/or the electrical impulse I can be generated with the first electrode device 3 selectively and/or independently of the different one. The first electrode device 1 is not supplied and/or controlled and/or no electrical impulse I is generated since the current 19 is blocked. Mutatis mutandis, the first electrode device 3 can be selected, in particularly selectively controlled and/or supplied and/or the electrical impulse I can be generated with the first electrode device 3 selectively and/or independently if the source polarity is changed, i.e., the current C and/or corresponding magnetic field H first decreases and increases afterwards, preferably up to zero and/or without changing the sign.

Thus, different electrode devices 3 can be selectively sourced, controlled, acti- vated and/or synchronized by means of different source polarities. Preferably, the different source polarities can be obtained by providing the sending means with pluses of different signs, preferably voltage and/or current pluses, in particular rectangular, delta or sawtooth-like pulses.

According to a further aspect of the present invention, different electrode devices 3 are configured for analyzing the sign of an incoming time-varying magnetic field H, e.g. by analyzing the starting sign of a current and/or voltage and/or starting direction of a current induced in the respective receiving means 9. The magnetic field H can alternate for providing energy, in particular several periods, to and/or for generating the electrical impulse I with an electrode device 3. For selecting a first one of the different electrode devices 3, the initial sign and/or polarity of the magnetic field H and/or the initial sign of the induced voltage can be specific to and/or associated with the first one of the different electrode devices 3, and a different sign and/or polarity and/or the different sign of the induced voltage can be specific to and/or associated with for a different one of the elec- trode devices 3.

In particular, the first one of the electrode devices 3 can be selectively sourced and/or activated for delivering an electrical impulse I if the sign of the first rising edge, in particular of an alternating sequence, of the time-varying magnetic field H or a corresponding current is positive and/or the different one of the electrode devices 3 can be selectively sourced, preferably exclusively, and/or activated for delivering an electrical impulse I if the sign of the first rising edge, in particular of an alternating sequence, of the time-varying magnetic field H or corresponding current is negative, preferably exclusively.

Alternatively or additionally, different electrode devices 3 can be sourced, controlled and/or activated for delivering an electrical impulse I selectively, wherein each of the electrode devices 3 reacts on the sign of the first rising edge, wherein the electrode devices 3 and/or their receiving means 9 are differently, in particu- lar at least essentially opposing, orientated. Thus, time-varying magnetic field H of a rising field strength generates different sings in different ones of the electrode devices 3. The selectivity can be achieved by means of a controller, microcontroller, logical element or the like of the electrode device 3 and/or associated with each of the receiving means 9 of the different electrode devices 3. Fig. 6 shows an alternative solution for synchronizing different electrode devices 3. A time-varying magnetic field H of a field strength is provided corresponding to current C according to Fig. 6 a), wherein the field strength in a first time span t₆ is increased, i.e. has a positive gradient. Afterwards, during optional time span t₇, the magnetic field strength is substantially constant. In the following time span t₈, the field strength decreases, i.e. has a negative gradient. The current C can be a current through a sending means 6 of a control device 5 and/or can correspond to a field strength of the magnetic field H. The system 1 can provide more than one control device 5, e.g. as depicted in Fig. 1 .

Different ones of the electrode devices 3 preferably are adapted such that different gradients of magnetic field strength, preferably gradients of different signs, can be used to selectively control, trigger and/or supply the electrode devices 3, in particular the electrode devices 3 of Fig. 3 or Fig. 4. In particular, in a first one of the electrode devices 3, the positive gradient during time span t₆ leads to an induction voltage U, that can be used for generating or as an electrical impulse I. An induction voltage by the negative gradient during time span t₈ is blocked as depicted in Fig. 6 b). As shown in Fig. 6 c), the second one of the electrode devices 3 has an opposite behavior. In particular, an induction voltage based on the rising gradient in time span t^ is blocked and induction voltage U₂ provided by a negative gradient in time span t₈ is not blocked, but preferably can be used for generating or as an electrical impulse I. Blocked voltages might be measurable but are preferably smaller than a voltage suitable for generating an electrical impulse I.

Fig. 7 shows three of the electrode devices 3, each with filtering means 12. In particular, these filtering means 12 are selective to particular frequencies. Preferably, a first one of the electrode devices 3 is selective to a frequency that is different to a frequency the second and/or the third one of the electrode devices 3 is selective to. In particular, the first one comprises a low-pass filter, the second one a band-pass filter and/or the third one a high-pass filter. This allows for controlling, triggering and/or supplying each of the electrode devices 3 separately. Hence, these can be synchronized as well. It is preferred that different ones of the electrode devices 3 are adapted to be controlled, triggered and/or supplied with energy by means of time-varying magnetic fields H of different frequencies. Hence, a time-varying magnetic field H of a first frequency can be assigned and/or selective to the first one and/or a time-varying magnetic field H of a second frequency can be assigned or selective to the second one of the electrode device 3, and, preferably, a third frequency is assigned or selective to the third one of the electrode devices 3.

In the example shown, a first frequency can be lower than a cut-off frequency of the low-pass filter of the first one of the electrode devices 3 and, preferably, energy is provided by this frequency passing the low-pass filter of the first one of the electrode devices 3 for generating an electrical impulse I. The (band-pass) fil- ter of the second one of the electrode devices 3 and/or the (high-pass) filter of the third one of the electrode devices 3 can be chosen such that the first frequency is blocked by the second and third one of the electrode devices 3.

A band-pass filter of the second one of the electrode devices 3 can have a pass- band preferably starting at a frequency higher than the cut-off frequency of the low-pass filter of the first one of the electrode devices 3 and/or ending at a frequency that is lower than a cut-off frequency of the high-pass filter of the third one of the electrode devices 3. A time-varying magnetic field H with a frequency inside the pass-band of the band-pass filter of the second one of the electrode de- vices 3 is, thus, blocked by the first and the third one of the electrode devices 3. Thus, a time-varying magnetic field H of a frequency within the pass-band of the band-pass filter of the second one of the electrode devices 3 can be used for controlling and/or supplying with energy of the second one of the electrode devices 3 and, preferably, this frequency is blocked by the first and the third one of the electrode devices 3 leading to separately controlling and/or supply the second one of the electrode devices 3.

A frequency higher than the cut-off frequency of the low-pass filter of the first one of the electrode devices 3 and/or of the band-pass filter of the second one of the electrode devices 3 can be used to separately controlling and/or supplying with energy of the third one of the electrode devices 3 providing a corresponding high-pass filter.

Additional electrode devices 3 can be provided, preferably with band-pass filters of pass-bands different to that of the second one of the electrode devices 3. Alternatively or additionally, additional electrode devices 3 being similar to the de- scribed ones can be used if electrical impulses I should be provided simultaneously and/or if a delay means 14 is used for providing a delay.

Fig. 8 a) shows a time-varying magnetic field H with different frequencies or a current C corresponding thereto. During a time span the magnetic field H has a first frequency. During optional time span t₁₀, the magnetic field H is substantially constant. In the following time span t_n, the magnetic field H has a frequency, e.g., twice the frequency of time span In optional time span t₎₂, the magnetic field H is substantially constant. In time span t₁₃, the magnetic field H has a frequency twice the frequency of time span t_u or four times the frequency of time span t₉. In optional time span t₁₄, the magnetic field H is substantially constant. In time span t₁₅, the time-variable magnetic field H comprises frequencies of time spans t₉ and t₁₃, simultaneously, in particular leading to a common, superposed oscillation of field strengths.

In Fig. 8 b), c) and d), voltages U, , U₂ and U₃ are depicted, in particular related to three different ones of the electrode devices 3 , in particular of Fig. 7, or to corresponding to currents, signals or the like. The first one of the electrode devices 3, is selective to a first frequency or frequency band, i.e. the first one of the electrode devices 3 can be adapted to block frequencies that are different or outside an accepted frequency band. The other ones of the electrode devices 3 can accept and/or block this first frequency or frequencies of this frequency band accepted by the first one of the electrode de- vices. For example, a low-path filter can be used for blocking frequencies higher than the first frequency of the time-varying magnetic field H of time span in the first one of the electrode devices 3. The first one of the electrode devices 3 can, thus, be adapted to accept induction voltages corresponding to the first frequency provided by the time-varying magnetic field H in time span Then, a command, triggering pulse and/or energy provided to the first one of the electrode devices 3 can be used for generating and/or as an electrical impulse I.

In time span t₁₅, time-varying magnetic field H provides two frequencies simultaneously. One of the frequencies provided is that of time span Thus, the first one of the electrode devices 3 accepts commands, triggering pulses and/or energy provided by means of the time varying magnetic field H in time span t₁₅ as well. Thus, the first one of the electrode devices 3 can provide an electrical impulse I during and/or after time spans t and t₁₅.

The induction voltage U₂ in Fig. 8 c) preferably corresponds to a second one of the electrode devices 3 which is preferably selective to a second frequency provided by the time-varying magnetic field H in time span t,, or to a frequency band comprising this frequency. Moreover, it is preferred that the second one of the electrode devices 3 blocks frequencies higher and/or lower than the second frequency the second one of the electrode devices 3 is selective to. It is not nec- essary to meet the frequency provided by the time-varying magnetic field H in time span t, , exactly. For example, a filtering means 12 with a band-path characteristic or with a band-stop characteristic can be used in the second one of the electrode devices 3, thus being selective to a frequency band. The second one of the electrode devices 3 preferably is selective to the frequency provided by the time-varying magnetic field H of time span t_n . Then, the second one of the electrode devices 3 can receive commands and/or energy provided by the time- varying magnetic field H in time span t,, as shown in Fig. 8 c). Thus, the second one of the electrode devices 3 can provide an electrical impulse I during and/or after time span t_n . Preferably, the second one of the electrode devices 3 blocks the first frequency and/or the first one of the electrode devices 3 blocks the second frequency. Thus, a selective control, supply and/or a synchronization is possible.

In Fig. 8 d), an induction voltage U₃ of a third one of the electrode devices 3 is shown. The third one of the electrode devices 3 is selective to the third frequency provided by the time-varying magnetic field H during time span t,₃. In time span t₁₅, the third frequency of time span t₁₃ is superposed with the first frequency of time span tg. Thus, in time spans t₁₃ and t₁₅ the third frequency, the third one of the electrode devices 3 is selective to, is provided by means of the time-varying magnetic field H according to Fig. 8 a). Thus, the third one of the electrode devices 3 accepts commands and/or energy provided by the time-varying magnetic field H during time spans t_I3 and t₁₅. During and/or after time spans t₁₃ and t₁₅, electrical impulses I can be provided by the third one of the electrode devices 3. Alternatively, the third one of the electrode devices 3 might generate a common electrical impulse I based on the energy provided in time span t₁₃ and t,₅, in particular if time span t₁₄ is sufficiently short. This leads to an impulse I varied in in- tensity and/or to a longer electrical impulse I. The selectivity of the third one of the electrode devices 3 can be achieved, for example, by high-path filter.

In example of Fig. 8, three different electrode devices 3, in particular those of Fig. 7, are selectively controlled and/or provided with energy by means of a time-varying magnetic field H of three different frequencies. Superposing at least two of these frequencies allows for activating, i.e. delivery of electrical impulses I, by two or more of the electrode devices 3 simultaneously. However, using single frequencies allows for controlling and/or supplying the electrode devices 3 selectively as well, which enables synchronizing them.

The energy provided by the time-varying magnetic field H can be rectified, shaped and/or filtered, in particular by a rectifier 13 and/or pulse forming means 15, such that a direct current component or offset is achieved as shown in Fig. 8 b) to d).

An electrical impulse I according to the present invention can be an alternating current or voltage, it can comprise a pulse-like shape, an at least substantially rectangular shape and/or a superposed or free-form shape, in particular a pulse- and/or rectangular shape which are superposed with an alternating component, for example as shown in Fig. 8 b) to d).

The electrical impulses I and/or time spans t_{l 5} t₄, t₆, t₈ , t,, , t₁₃ and/or t₁₅ can have a time duration of substantially 10 ^s to 500 ^s, preferably between 20 //s and 300 /*s, in particular between 50 /*s and 200 μ$. The electrical impulse I can have an amplitude of between 100 mV and 10 V, preferably between 500 mV and 5 V, in particular between 1 V and 2 V. The same values can apply to different impulse forms, wherein these values can apply to a intermediate amplitude, an average value and/or to an offset which might be superposed with an alternat- ing component , ripple or the like.

The control device 5 can be adapted to generate a time-varying magnetic field H of more than 0.1 mT and/or less than 2 mT and/or more than 0.1 ms and/or less than 5 ms. A plurality of short magnetic field pulses and/or of an alternating field strength can be generated as a sequence by the control device 5 and/or during switch-on time of the magnetic field H. Switch-on times of the time-variable magnetic field H in the example of Fig. 8 a) are time spans t₉, t_n , t₁₃, t₁₅, which can be longer than 0,1 ms and/or shorter than 50 ms, each. Time spans t₁₀, t,₂ and t,4 are optional switch-off times or brakes. It has to be pointed out, that different types of transmission characteristics can be combined in a common stimulation system 1. For example, three electrode devices 3 can be provided, wherein two of them are selective to different frequencies and two of them are selective to different polarities. Preferably, at least one of the electrode devices 3 is selective to and/or selectively influenceable particu- lar frequencies and polarities simultaneously. Different other types of transmission characteristics can be used and combined as well. For example, in a stimulation system 1 two groups of at least one electrode device 3 are provided, wherein the first group is selective to by different polarities of the time-variable magnetic field H and electrode devices 3 of a different groups can be selective to and/or selectively influenceable, i.e. are adapted to be selectively controlled, triggered or supplied by means time-varying magnetic fields of, different transmission characteristics, e.g. different frequencies. The control device 5 can be adapted to generate different transmission characteristics of the same or of different types, e.g. polarities and/or frequencies, simultaneously, intermittingly or the like.

It is preferred that electrode devices 3 are selective to different transmission characteristics of the magnetic field H, in particular each one of the electrode devices 3 is selective to and/or influenceable by a different transmission characteristic and/or different transmission characteristics are assigned to different ones of the electrode devices 3, respectively. However, it is not necessary that the transmission characteristic, to which a particular one of the electrode devices 3 is selective or sensitive, is exactly identical to the transmission characteristic provided by the time-varying magnetic field H. Preferably, it is sufficient that the transmission characteristic of the time-varying magnetic field H and the trans- mission characteristic the electrode device 3 are similar, in particular such that the magnetic field H can affect the respective electrode device 3. Furthermore, the electrode devices 3 should be sufficiently selective such that a time-varying magnetic field H of a particular transmission characteristic assigned to a particular one of the electrode devices 3 should not be able to control, trigger and/or supply a different one of the electrode devices 3 at the same time. However, a time-varying magnetic field 3 might provide different transmission characteris- tics at the same time and/or more than one electrode device 3 of identical selectivity can be provided in order to be controlled, triggered and/or supplied with energy simultaneously. In particular, the following aspects of the present invention can be realized independently or in any combination:

According to a further aspect of the present invention, the electrode device 3 comprises a rectifier 13, wherein, preferably, the rectifier 13 comprises semicon- ductor switches with a control port for commutation. Preferably, these semiconductor switches with control ports are transistors, in particular MOSFETs, wherein the control port an be their gate. Alternatively or additionally, it is possible that semiconductor switches are IGBTs, four-layer-elements or any kind of semiconductor devices with controllable impedance. Preferably, the rectifier 13 comprises semiconductor switches in a (H-) bridge configuration. The term "commutation" preferably is understood as switching an output from one to another (input-) phase, e.g. connecting an output port from a first to a second input port, in particular if a potential difference of the input is zero, in the area of zero- crossing or the like. Using a rectifier 13 comprising semiconductor switches leads to an efficient rectifying i .e. low losses, as semiconductor switches can provide a low impedance, in particular at low operation voltages.

According to a further aspect of the present invention, the electrode device 3 comprises a delay means 14 for generating a delay between reception of energy and the generation and/or delivery of at least one of the electrical impulses I. Thus, a time for generating and/or for emitting and/or delivering an electrical impulse I can be defined more precisely. This is advantageous for an exact and reliable stimulation. According to a further aspect of the present invention, the electrode device 3 comprises a protection means to prevent or block generation or delivery of electrical impulses for a time span after a first electrical impulse has been generated. Hence, it is possible to prevent the system from generating and/or emitting electrical impulses when it is not intended. In particular, it is possible to prevent er- rors caused by possible disturbance or interference, in particular by undesired strong magnetic or electromagnetic fields. According to a further aspect of the present invention, the system 1 , in particular a cardiac pacemaker, comprising an implantable control device 5 and at least a first implantable electrode device 3 according to the aspects of the present inven- tion. Such a stimulation system 1 can be much more efficient and reliable, in particular benefiting from the advanced electrode device 3. With improvements in efficiently, portable systems can provide an extended life time until recharge is necessary. In addition, a better and/or more powerful stimulation can be reached. Preferably, the stimulation system 1 can comprise at least a second electrode device 3 which may be an electrode device 3 according to aspects of the present invention also, but does not need to. In particular, the second electrode device 3 is implantable and configured as a wireless and/or compact structure unit and can be supplied with energy and, preferably, controlled by means of a time-varying magnetic field H. With at least two electrode devices 3 it is possible to realize a much more efficient stimulation, in particular by stimulating different areas. It can be useful to realize a time delay T between electrical impulses I of the different electrode devices 3. Hence, it can be particularly advantageous to make use of the delay means 14 of the at least one electrode device 3 according to an as- pect of the present invention.

According to a further aspect of the present invention, a method for operating at least two implantable electrode devices 3 is provided. These devices 3 preferably are used in a cardiac pacemaker system 1 and/or for generating electrical im- pulses I. According to this method, the electrode devices 3 are supplied with energy exclusively in a wireless manner, and electrical impulses I are generated by the electrode devices 3 with a particular time delay T. The time delay T is controlled and/or modified by means of the magnetic field H, in particular wherein the electrode devices 3 are triggered by magnetic fields H of different strength. Controlling or modifying the time delay T between the electrical impulses I generated by each of the electrode devices 3 can lead to an optimized stimulation result. Furthermore, it is advantageous to trigger the electrode devices 3 by magnetic fields H of different strength, as these magnetic fields H can be generated easily, in particular without additional hardware. According to a further aspect of the present invention, it is possible to combine any of the above mentioned aspects and/or alternatives. It is pointed out that it can be extraordinary advantageous if an implantable electrode device 3 comprises a delay means 14 as well as protection means, wherein both of them can make use of a common switch in series with the electrode 1 1 , preferably a semiconductors switch, in particular a MOSFET. Furthermore, a supervisory component (controller) 21 can be adapted to control the switch for the delay and/or the protection functions. Nevertheless, the delay means 14 and/or the protection means can be realized separately, too.

Another aspect of the present invention resides in the fact that the implantable electrode device 3 for generating electrical impulses I can be supplied with energy and/or preferably directly controlled in an exclusively wireless or leadless manner by means of a time-varying magnetic field H. This permits a very simple and compact structure of the electrode device H, whereby in particular no wiring of the electrode device 3 is required so that implantation is simplified and the risk of failure of an electrical lead is avoided and in particular, whereby the use of an energy storage device such as a rechargeable battery, a battery or similar in the electrode device 3 can be avoided. Furthermore, substantially greater free- dom in the placement of the electrode device 3 is obtained.

The magnetic field H is preferably generated by an, in particular implantable, control device 5 so that an external controller can be avoided. This is particularly desirable when the stimulation system 1 is used as a cardiac pacemaker and is substantially more reliable in use than control by an external, i.e. non-implanted, control device 5.

The electrode device 3 is particularly preferably controlled directly by the time- varying magnetic field H. "Direct" control is to be understood in the present pat- ent application in that the electrical impulses I are generated in direct dependence on the magnetic field H, for example, depending on the magnitude of the magnetic field H, the polarity of the magnetic field H and/or the rate of change of the magnetic field H, in particular without any active electronic component being interposed in the electrode device 3. Preferably, the electrode device 3 is adapted such that the amount of energy received by the magnetic field H is equal or grater than the amount of energy delivered by means of the electrical impulses I. The electrode device 3 preferably is passive in the sense of a black-box view, i.e. the electrode device 3 is not able to provide more energy in form of the electrical impulse I than previously received by means of the magnetic field H, in particular over a time span of one, two or more electrical impulses 1 and/or over lifetime and/or as long as implanted in the body 4. Consequently, in the preferred direct control, electrical impulses I or stimulations are generated so that they are only temporally correlated to the magnetic field H. This also permits a very simple and in particular compact structure of the electrode device 3 and/or a very reliable defined control.

According to a further aspect of the present invention, an aspect includes configuring the electrode device 3 such that an electrical impulse I is only generated when a minimum field strength of the magnetic field H is exceeded. This very simply measure permits reliable control which in particular is not sensitive to in- terference when the minimum field strength is selected as suitably high, since strong magnetic fields H occur very rarely but alternating electromagnetic fields having various frequencies are common.

In particular, a first electrode device 3 can be configured to generate and electri- cal impulse I, if a first, minimum field strength of the magnetic field H is exceeded and a second electrode device 3 is configured to generate an electrical impulse I, if a second minimum field strength of the magnetic field H is exceeded. Preferably, the first and the second minimum field strength can be different such that the electrical impulses I can be controlled independently using magnetic fields H of different strength. Thus, a time delay T between two or more electrical impulses I of different electrode devices 3 can be obtained and/or controlled.

According to a further aspect of the present invention, the electrode device 3 must first be activated before a further electrical impulse I can be generated. This activation is effected in particular by another signal, preferably by the opposite field direction of the magnetic field H, shortly before triggering and generating the next electrical impulse I. Thus, two-stage triggering or signal generation is required to generate an electrical impulse I by means of the electrode device 3. This two-stage property results in particularly reliable triggering, i.e., not sensitive to interference. Alternatively or additionally, the protection means can be used to prevent or block the generation and/or delivering of an electrical impulse I, in particular by deactivating a trigger function, by decoupling electrodes 1 1 or the like. According to a further aspect of the present invention, the aforesaid triggering safety can be further improved or enhanced whereby the activation of the electrode device 3 always takes place shortly before the generation of the next electrical impulse I. Accordingly, the possibility that an electrical impulse I as a result of an interference signal (external magnetic field H with corresponding field orientation and exceeding the minimum field strength) can lead to undesirable or premature triggering of the next electrical impulse I is so minimal that there is no risk for a patient.

According to a further aspect of the present invention, a coil device (receiving means 9 or coil 10) having a high number of turns, that is a coil having many turns, is used to generate an electrical impulse having a high voltage of at least 0.5 V, preferably substantially 1 V or more and having a relatively long duration of at least 0.05 to 2 ms. In this case, the coil device (receiving means 9 or coil 10) can in particular have a soft-magnetic or ultrasoft magnetic core 16. The high number of turns, in particular at least 1 ,000 turns, of a suitably insulated wire made of, for example, Cu, Ag or Al in particular having a diameter of about 0.01 to 0.1 mm permits the generation of a strong and long electrical impulse I in said sense. According to a further aspect of the present invention, when the magnetic field H is switched on, no continuous or persistent, for example, sawtooth-shaped ascending magnetic field pulse is generated by the control device 5 but a plurality of short magnetic field pulses, in particular so that the core 16 of the coil device (receiving means 9 or coil 10) or electrode device 3 always varies its magnetiza- tion far below the saturation state. Thus, a minimal energy consumption can be achieved, in particular if the largest possible temporal flux variation takes place in the core 16 of the coil device (receiving means 9 or coil 10) or electrode device 3 throughout the entire duration of the stimulating pulse (optionally a contiguous sequence of electrical impulses of the electrode device 3; in the present invention, this sequence is considered as a single electrical impulse I for stimulation). This can be achieved by short magnetic field pulses. According to a further aspect of the present invention, the magnetic field H or magnetic field pulses can be unipolar or bipolar when using soft-magnetic core material . When using bistable materials (in particular Wiegand or pulsed wires), bipolar magnetic fields can be used.

According to a further aspect of the present invention, instead of an electrode device 3, direct electrical stimulation by a magnetisable element can take place. This magnetisable element can comprise a rectifier 13 comprising semiconductor switches and/or a delay means 14 and/or a protection means as well. The element in particular comprises a coil core without coil or the like. This means that a coil 10 for transforming the magnetic field into electric current can be omitted. Instead, the magnetisable element generates directly the desired electric impulse for stimulation.

According to a further aspect of the present invention, an implantable stimulation device comprises the magnetisable, preferably ferromagnetic element, the magnetization of the element being varied by an external or varying magnetic field H so that the magnetic leakage flux of the element results in the desired electrical stimulation or generation of an electrical impulse I in the surrounding tissue. This permits a particularly simple structure where electrical contact electrodes are omitted and the associated problems can be avoided.

According to a further aspect of the present invention, a proposed electrode de- vice 3 or another electrode device 3 can be used alternatively or additionally to convert the self-action of the heart 4, in particular a movement of the heart 4 and/or electrical activity of the heart 4, into a magnetic impulse or another, in particular, electrical signal which can preferably be detected by the stimulation system 1 or another receiving unit or the control device 5.

According to a further aspect of the present invention, the implantable electrode device 3 is used in particular for generating electrical signals I to stimulate the heart 4. However, the present invention is not restricted to this. Rather, the electrode device 3 can generally generate any type of electrical impulse(s) I or elec- trical signals in the human or animal body 2. The terms "electrode device" and "stimulation system" should accordingly be understood in a very general sense so that other applications and uses, such as for example to influence the brain, can also be understood.

According to a further aspect of the present invention, the control device 5 or its energy storage device can be inductively recharged, e.g. in the implanted state. Thus, in particular when the energy consumption is high, an otherwise necessary operation to change the battery or changing the control device 5 can be avoided. The coil 6 provides a way to generate the magnetic field H, and is preferably used for the inductive charging. However, another induction device not shown can also be used for charging.

According to a further aspect of the present invention, the electrode device 3 is very compact and in particular is configured as substantially rod-shaped or cylindrical . In the example shown, the length is 10 to 20 mm, in particular substan- tially 15 mm or less. The diameter is preferably at most 5 mm, in particular substantially 4 mm or less. A retaining device can be attached to the electrode device 3, preferably an anchor or a screw which allows the electrode device 3 to be anchored in the heart muscle. According to a further aspect of the present invention, the electrode device 3 is configured to generate electrical impulses I for the desired stimulation or signal generation. The electrical impulses I are delivered, for example, via the electrodes 1 1. In the example shown, the electrodes 1 1 are located on opposite sides. Alternatively or additionally, the electrode 1 1 can comprise windings or turns at, attached to and/or projecting therefrom. However, the electrodes 1 1 can also be arranged concentrically or otherwise, for example, at one end or at the opposite ends of the electrode device 3 or the housing 17.

According to a further aspect of the present invention, the pulse forming device 15 is used for forming or reforming a pulse-like induction voltage which is generated or delivered under certain circumstances, as will be described in further detail hereinafter, by the induction or coil device (receiving means 9 and/or coil 10). The reformed electrical impulse I can then be output directly for stimulation via the connected electrodes 1 1 . According to a further aspect of the present invention, further structural elements are not required in principle but are possible. The electrode device 3 preferably comprises a rectifier 13 for rectifying energy received by the coil device (receiving means 9 and/or coil 10), a delay means 14 for generating a time delay T be- tween reception of the energy and generation of the electrical impulse I, and/or a protection means to prevent or block generation or delivery of electrical impulses I when delivery is not intended. Furthermore, the electrode device 3 can also be implemented by other structural elements having a corresponding function. According to a further aspect of the present invention, the induction or coil device (receiving means 9 and/or coil 10) is preferably configured such that a pulse-like induction voltage is generated when a minimum field strength of the, i .e., external magnetic field H acting on the electrode device 3 or coil device (receiving means 9 and/or coil 10) is exceeded. For this purpose, the coil device particularly preferably has a coil core 16 which exhibits an abrupt change in the magnetization, i .e. bistable magnetic properties, when the minimum field strength is exceeded. This abrupt change in magnetization or magnetic polarization results in the desired pulse-like induction voltage in an allocated coil 10. Alternatively or additionally, a reed relay in series with at least one electrode 1 1 can be used for generation and/or delivery of the electrical impulse I. In order to achieve the aforesaid bistable magnetic behavior of the coil core 16 is preferably constructed of at least one core element, preferably of a plurality of core elements. The core elements preferably run parallel to one another so that the coil core 16 has a bundle-like structure of the core elements. If necessary, however, only a single core element can be used to form the coil core 10, especially if the energy of the electrical impulse I to be generated is relatively low or a different arrangement, for example, comprising a plurality of coil devices (receiving means 9 and/or coil 10) is used. The individual core elements preferably have a diameter of about 50 to 500 μχη, in particular substantially 100 μπ\ and/or a length of 5 to 20 mm, in particular substantially 15 mm.

According to a further aspect of the present invention, the impulse generation and triggering preferably takes place as a result of the external magnetic field H acting on the coil device (receiving means 9 and/or coil 10) being varied in time so that when the first minimum magnetic field strength is exceeded, an abrupt change in the magnetization of the core elements or the coil 10 takes. As a result of the inverse Wiedemann effect, this abrupt change in the magnetization results in a pulse-shaped induction voltage (impulse I) in the allocated coil 10. This first minimum field strength is therefore a switching threshold. Alternatively or additionally, a delay means 14, in particular a reed relay, and/or a protection means may be activated or controlled by the first minimum magnetic field strength. The induced voltage pulses or electrical impulses I 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 15 is preferably used. The induced voltage pulse or electrical impulses I can thus in particular be stretched in time. Alternatively or additionally, a longer pulse duration can also be achieved by bundling a plurality of core elements in the coil 10, in particular so that the pulse forming device 15 can be completely omitted. The magnitude of the minimum field strength depends on various factors, in particular the manufacturing conditions of the core elements. The mini- mum field strength 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 H usually permissible in public so that any triggering of an electrical impulse I by interference fields usually expected is eliminated.

According to a further aspect of the present invention, the external magnetic field H, in particular generated by the control device 5, is used both for controlling (triggering) the generation and delivery of an electrical impulse I by the electrode device 3 and also for supplying the electrode device 3 with the energy necessary for generating the electrical impulse I. In addition, the magnetic field H is preferably also used for said activation of the electrode device 3 for the possible generation of the next electrical impulse I. However, this can be also be affected in another manner or by another signal. According to a further aspect of the present invention, a plurality of electrode devices 3 can be used which in particular can be controlled and supplied with energy by a common control device 5. The electrode devices 3 can then be implanted at different locations, for example. As a result of different first minimum field strengths, different coil devices (receiving means 9 and/or coil 10) and/or pulse forming devices 15 or the like, desired phase shifts, energy differences or the like can then be achieved in the electrical impulses I or signals delivered by the individual electrode devices 3. In particular, the delay means 14 can be used for synchronizing the electrode device 3.

It should be noted that the preferred synchronization of the stimulation of the heart 4 with the heat beat can be achieved, for example, by evaluating the electric voltage induced in the coil 6 of the control device 5 by the movement of the electrode device 3, optionally in conjunction with the ECG voltage which can be detected galvanically via the housing of the control device 5 or a respective electrode.

Particular advantages of the invention reside in the possibility that the wireless electrode device 3 can be implanted in more suitable regions for stimulation, in particular, of the heart muscle, than is possible with wire-bound electrodes. Moreover, a plurality of electrode devices 3 can be implanted at different locations or sites whereby improved stimulation and in particular better cardiac dynamics can be achieved.

According to a further aspect of the present invention, as a result of the special RLC properties (impedance) of the primary coil 6 of the control device 5, the ex- citing magnetic field H can only increase relatively slowly (typically from 0 to a maximum of, for example, 0.1 to 2 mT in 0.1 to 5 ms). In the proposed coil device (receiving means 9 and/or coil 10) of the electrode device 3 and under loading with a characteristic resistance for the heart muscle of, for example, about 1 kOhm, a relatively broad or long-lived impulse having a duration of at least 0.1 ms, in particular of substantially 0.25 to 2 ms, can be generated. This can possibly be attributed to the alternating current properties of the LRC arrangement (or the coil device (receiving means 9 and/or coil 10), high inductance and high winding capacity of the coil) and/or to the retroactive effect of the coil current on the core.

According to a further aspect of the present invention, the duration of the respective electrical impulse I (a single stimulation) generated by the electrode device 3 depends on the respective switch-on time of the magnetic field H, in particular on the number of trigger pulses generated in a sequence and thus on the number of magnetic field pulses generated by the control device 5. Consequently, the control device 5 controls the generation of the electrical impulse I or the elec- trode device 3 by the magnetic field H directly in the initially specified sense of the present invention.

According to a further aspect of the present invention, typically, diodes in a bridge configuration are use for rectifying. A rectifier 13 preferably comprises semiconductor switches with a control port for commutation instead or additionally. These can be configured to switch already in the area of a zero-crossing, preferably in contrast to diodes having a threshold voltage of about 0.4 to 0.8 Volt. Particularly preferably, the semiconductor switches, in particular MOS- FETs or the like, of the rectifier 13 have a threshold voltage of about zero and/or are biased at about threshold, preferably the threshold voltage and/or an biasing offset from threshold is less than ±200 mV, in particular less than ±100 mV or ±50mV. By this measure, a voltage drop across the devices forming the rectifier 13 can be minimized and/or avoided. Thus, the rectifier 13 with semiconductor switches can allow for reduced power losses and/or more efficient rectifying.

According to a further aspect of the present invention, the electrode device 3 preferably comprises a protection means, in particular with a supervisory component (controller 21 ) and/or a semiconductor switch. The semiconductor switch can be controlled by the supervisory component (controller 21). The semiconductor switch preferably connects the rectifier and/or the storing element to at least one of the electrodes 1 1. The semiconductor switch can be provided in series with at least one of the electrodes 1 1. Thus, generating an electrical impulse I and/or delivery of the electrical impulse I can be blocked by semiconductor switch. Preferably, the semiconductor switch has a high resistance state for blocking electrical impulse as well as a low resistance state for generating an electrical impulse I or for enabling its generation. Preferably, the protection means is adapted to prevent generation and/or to block delivery of electrical impulses I for time span greater than 0.5 ms, preferably greater than 1 ms and/or less than 100 ms, preferably less than 20 ms in particular 10 ms or less.

According to a further aspect of the present invention, the supervisory component (controller 21 ) and/or semiconductor switch can provide or act as a means for generating a time delay T 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 (controller 21) may control the semiconductor switch to get into its high resistance state directly. Afterwards, the energy delivered to the electrode device 3 can be stored in the energy buffer for a particular time span. Afterwards, the semiconductor switch can be switched into its low resistance state, in particular by the supervisory component (controller 21 ), and the electrical impulse I can be generated and/or delivered. Thus, the protection means alternatively or additionally can provide the functionality of a delay means 14, in particular as well. Preferably, the supervisory component (controller 21) can be programmed in advanced and/or by signals transmitted by the magnetic field H accordingly. The supervisory component (controller 21) and/or the electrode device 3 can comprise a decoding means for decoding a signal 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 (controller 21) and can be used for programming and/or controlling the supervisory component (controller 21). Alternatively or additionally, the electrode device 3 may comprise a delay means 14, in particular a reed-switch. This delay means 14 can block generating and/or delivering the electrical impulse I until a particular field strength or minimum field strength of the magnetic field H is reached. The delay means 14 preferably is placed in series with at least one electrode 1 1 . For example, the time-varying magnetic field H can provide energy to the electrode device 3 using field strengths lower than that needed for controlling or triggering the delay means 14. At the time, the electrical impulse I has to be delivered, the magnetic field H can reach or exceed the minimum field strength. According to a further aspect of the present invention, different electrode devices 3 in the stimulation system 1 are placed in some distance D, in particular in a distance D 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 3 comprises a delay means 14 for generating a delay between re- ception of the energy and the generation of at least one of the electrical impulses I. Thus, different electrode devices 3 can generate electrical impulses I with a time lack between a first electrical impulse I generated by the first electrode device 3 and a second electrical impulse I generated by the second electrode device 3 which preferably comprises the delay means 14 in this example. Thus, a com- mon, additive stimulation can be adapted to the natural behavior of an object to be stimulated, e.g. a heart 4 can be stimulated at a first position and, after a short delay D, at a second position, preferably according to its typical activation and/or stimulation. Therefore the second electrode device 3 may comprise a reed relay as delay means 14 that can block the output and/or generation of the electrical impulse I for the particular time span, e.g., until a minimum field strength for triggering is exceeded. In a stimulation system 1 with more than two electrode devices 3, it is particularly preferred that all electrode devices 3 or at least one less than the number of electrode devices 3 actually used comprise delay means 14, in particular (micro-) reed relays. Then, different electrode devices 3 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 for triggering.

According to a further aspect of the present invention, the protection means preferably is adapted to prevent generation and/or to block delivery of electrical im- pulses I 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 I that may occur due to a disturbance event, and at the same time a generation of a following electrical impulse I is not affected.

According to a further aspect of the present invention, the induction pacemaker technology described can also be used in combination with conventional cardiac pacemaker technology. In this connection, the use for left-ventricular stimulation within the framework of resynchronization therapy is particularly appropriate.

According to a further aspect of the present invention, the pulse shape, in particular of the electrical impulse I, can be adjusted arbitrary for the most effective stimulation with respect to the pacing pulse height and width by using a pro- grammable sequence of amplitudes, durations and delay times of the individual burst pulse voltages applied to the primary coil. The importance of choosing an optimal pulse shape has been described in US 5,782,880 A.

According to a further aspect of the present invention, the control device 5 is preferably in a flexible housing as it should be implanted directly above the heart 4 near the thoracic wall . To achieve this flexibility the control device 5 can be embedded in a silicon cushion, however other soft materials can also be used. Preferably, the electrode devices 3 comprises a flexible housing 17 and/or means for magnetic field concentration at the inner surface of the housing 17. According to a further aspect of the present invention, the control device 5 can be configured such that the magnetic field H is generated intermittently and/or wherein the control device 5 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 frequency of the magnetic field H can be less than 3 Hz, in particular corresponds to the desired frequency of the electrical impulses I to be generated. The control device 5 in particular is configured in such a manner that the field strength of the magnetic field H in the region of the electrode device 3 is substantially 1 to 20 mT, in particular 2 to 10 mT. The control device 5 in the implanted state can be charged inductively from outside.

According to a further aspect of the present invention, the stimulation system 1 is configured in such a manner that in the switched-on state the magnetic field H is formed by a plurality of unipolar or bipolar magnetic field pulses and/or that the respective switch-on duration of the magnetic field H controls or determines the length of each electrical impulse I of a stimulation generated by the electrode device 3 and/or the magnetic field H is utilized for energy recovery.

Individual features, aspects and elements of the individual embodiments and variants can be combined with one another, but also realized independently from each other and/or combined with one or more of the following aspects:

Preferably a 40 μ≤ long and/or rectangular pulse, preferably with about 2V, can be used for stimulation.

For a single pulse the sign of the first pulse from a pulse burst can be evaluated.

The receiving means 9 can use a diode 18 in series with the electrodes 1 1 .

At the transmitter site, preferably care has to be taken to ensure that the decay of the magnetic field H is relaxed compared to its leading flank in order to accord- ingly induce at the receiving means 9 preferably strongly different pulse amplitudes of the opposite voltages as obtained from such a magnetic field timing. This can be accomplished per example by an inductance switchable, i.e. addable and/or removable, in parallel to the primary coil, i.e. sending means 6 of control device 5, when the voltage pulse to this coil ends (other circuits might be possible).

Instead of drawing reversed diodes at the two receiving means 9, the coil winding sense can be reversed.

A smoothing capacitor across the receiving means 9 and/or the electrodes 1 1 can be added to reduce fluctuations.

The flyback current from the sending means 6, after the end of the primary voltage pulse can be sufficiently stretched in time to yield a di/dt small enough to produce an induction voltage well below the pacing threshold.

The second receiver preferably has a reversed behavior for the two voltage pulse polarities applied to the primary coil, i.e. when exchanged correspond to the voltage pulses at the second receiver for identical primary excitation conditions.

The primary pulse polarity thus determines which of the two receivers will generate a pacing voltage of sufficient amplitude.

Reference signs:

1 System

2 Body

3 Electrode devices

4 Heart

5 Control device

6 Sending means

7 Thoracic cage

8 Skin

9 Receiving means

10 Coil

1 1 Electrode

12 Filtering means

13 Recitfier

14 Delay means

15 Pulse forming device

16 Coil core

17 Housing

18 Unidirectionla means

19 Current

20 Current

21 Controller

D Distance

gl - g4 Gradient

1 Electrical impulse

H Magnetic field t. - t₁₅ Time span

T Time delay

Claims

Claims:

1. Stimulation system (1), preferably a cardiac pacemaker, comprising at least two implantable electrode devices (3) for generating electrical impulses (I), wherein the electrode devices (3) are configured as wireless units and are adapted to be supplied with energy exclusively in a wireless manner by means of a time-varying magnetic field (H), wherein

the electrode devices (3) are adapted to be controlled independently from each other by means of the time-varying magnetic field (H) of different polarities associated with different ones of the electrode devices (3); and/or different ones of the electrode devices (3) are adapted to be supplied independently from each other with energy by means of the time-varying mag- netic field (H) of different transmission characteristics associated with the different ones of the electrode devices (3).

2. System of claim 1 , wherein the transmission characteristics cover or are fre- quencies, and/or wherein the at least two of the electrode devices (3) are adapted to be selective to the time-varying magnetic field (H) of different frequencies.

3. System of claim 1 or 2, wherein the transmission characteristics cover or are polarities, and/or wherein the at least two of the electrode devices (3) are adapted to be selective to the time-varying magnetic field (H) of different polarities.

4. System of any one of the preceding claims, wherein the electrode devices (3) are adapted such that a time delay (T) between two or more electrical impulses (I) of different electrode devices (3) can be obtained and/or controlled, preferably wherein the time delay (T) is controllable and/or modifiable by means of the time-varying magnetic field (H), preferably with different transmission characteristics.

5. System of claim 3 or 4, wherein time-varying magnetic fields (H) of differ- ent polarities cover or are time-varying magnetic fields (H) of at least one of: different source polarities, in particular different orientations of the magnetic poles of a magnetic field source; different field polarities, in particular polarizations of the time-varying magnetic field (H);

different grandient polarites, in particular signs of gradients (g_1-4) or slopes over time of a varying field strength; and

different offset polarities, in particular strength and/or orientations of a static magnetic filed added to the time-varying magnetic field (H).

6. System of any one of the preceding claims, wherein the electrode devices (3) are adapted to be controlled, triggered and/or supplied with energy independently from each other.

7. System of any one of the preceding claims, wherein at least one, two or all of the electrode devices (3) is or are adapted to be controlled and/or supplied with energy exclusively by means of the time-varying magnetic field (H) with different transmission characteristics, each field or characteristic being specific to respective ones of the electrode devices (3).

8. System of any one of the preceding claims, wherein a first one of the electrode devices (3) is configured to generate an electrical impulse (I) if the time- varying magnetic field (H) has a first transmission characteristic, and a second one of the electrode devices (3) is configured to generate an electrical impulse if the time-varying magnetic field (H) has a second transmission characteristic dif- ferent from the first one.

9. System of any one of the preceding claims, wherein at least a first one of the electrode devices (3) is adapted to be, preferably exclusively, controlled, in particular triggered, for generation of an electrical impulse (I), by means of a field strength of the time-varying magnetic field (H), preferably wherein at least the first one of the electrode devices (3) is adapted to generate the electrical impulse (I) if the field strength exceeds a minimum absolute value or exceeds a slope of a minimum absolute value.

10. System of any one of the claim 9, wherein a different, second one of the electrode devices (3) is adapted to be, preferably exclusively, controlled, in particular triggered for generation of an electrical impulse (I), by means of a field strength of the time-varying magnetic field (H) of a different transmission characteristic, preferably wherein the second one of the electrode devices (3) is adapted to generate the electrical impulse (I) if the field strength exceeds a different minimum absolute value or exceeds a different slope of a minimum abso- lute value.

1 1. System of any one of the preceding claims, wherein a first one of the electrode devices (3) is adapted to be controlled and/or supplied, in particular exclusively, using a offset in field strength, and/or a second one of the electrode de- vices (3) is adapted to be controlled and/or supplied with energy, in particular exclusively, using a different, preferably inverse or inverse signed, offset.

12. System of any one of the preceding claims, wherein at least two or all of the electrode devices (3) comprise filtering means (12) being selective to different transmission characteristics, wherein, preferably, the filtering means ( 12) are adapted to block and/or pass commands and/or energy provided by means of the time-varying magnetic field (H) depending on its transmission characteristic.

13. System of any one of the preceding claims, wherein at least two or all of the electrode devices (3) comprise receiving means (9), in particular coils (10) and/or antennas, being selective to different transmission characteristics, wherein, preferably, the receiving means (9) are adapted to receive and/or reject commands and/or energy provided by means of the time-varying magnetic field (H) depending on its transmission characteristic.

14. System of any one of the preceding claims, wherein at least two or all of the electrode devices (3) are synchronizable, in particular wherein at least one of the electrode devices (3) is configured for delaying generation or for delaying delivery of an electrical impulse (I) with reference to generation or delivery of an electrical impulse (I) by a different one of the electrode devices (3).

15. System of any one of the preceding claims, wherein at least one, both or all of the electrode devices (3) is or are adapted to deliver an electrical impulse (I), preferably electrical impulses (I) comprising a sequence of pulses or oscillations.

16. System of any one of the preceding claims, wherein at least one, both or all of the electrode devices (3) comprise at least two electrodes (8) for delivering electrical impulses (I), preferably to an area, in particular of or to a body (2) or tissue, surrounding the electrode device (3).

17. System of any one of the preceding claims, wherein at least one, both or all of the electrode devices (3) are electrically passive, and/or each has a capacity for buffering electrical energy of less than 50 μ¥, preferably less than 10 μ¥, in particular less than 1 μ¥.

18. System of any one of the preceding claims, wherein at least one, both or all of the electrode devices (3) is or are each adapted to buffer a total amount of energy for delivery of a maximum of ten electrical impulses (I), preferably two electrical impulses (I), in particular one electrical impulse (I).

19. System of any one of the preceding claims, wherein the system ( 1) comprises a control device (5) adapted for controlling, supplying with energy and/or synchronizing the at least two electrode devices (3).

20. System of claim 19, wherein control device (5) is adapted for generating a time-varying magnetic field (H) of different transmission characteristics, in particular frequencies and/or polarities, preferably where the transmission characteristics at least substantially correspond to transmission characteristics associated with different ones of the electrode devices (3) of the system ( 1).

21 . System of claim 19 or 20, wherein the control device (5) is adapted for controlling and/or transmitting energy, in particular exclusively, to at least one of the electrode devices (3) and/or for generating a time-varying magnetic field (H), in particular with a transmission characteristic which is exclusively specific to the particular one of the electrode devices (3).

22. Method for operating at least two implantable electrode devices (3) for generating electrical impulses (I) in a stimulation system (1), in particular in a cardiac pacemaker system, wherein the electrode devices (3) are supplied with en- ergy in a wireless manner by means of a time-varying magnetic field (H), wherein a first one of the electrode devices (3) is selectively controlled by means of the time-varying magnetic field (H) of a first polarity and a second one of the electrode devices (3) is selectively controlled by means of the time- varying magnetic field (H) of a second, different polarity; and/or

a first one of the electrode devices (3) is selectively supplied with energy by means of a time-varying magnetic field (H) of a first transmission characteristic and a second one of the electrode devices (3) is selectively supplied with energy by means of a time-varying magnetic field (H) of a second, different transmission characteristic.

23. Method of claim 22, wherein electrical impulses (I) are generated by different ones of the electrode devices (3) with a particular time delay (T), preferably wherein the time delay (T) is controlled and/or modified by means of the time- varying magnetic field (H), preferably of different transmission characteristics, in particular different frequencies and/or different polarities.

24. Method of claim 22 or 23, wherein the electrode devices (3) are controlled to deliver electrical impulses (I), preferably to the surrounding area, body (2) and/or tissue.

25. Method of claim 22 to 24, wherein the electrode devices (3) are supplied with energy and/or controlled to deliver electrical impulses (I) in a synchronized manner, in particular with a time delay (T) between supplying, controlling and/or delivery of electrical impulses (I) by different ones of the electrode devices (3).

26. Method of any one of the claims 22 to 25, wherein a transmission characteristic of a first, a second and/or further one of the electrode devices (3) is or are estimated, preferably based on a behavior, location and/or orientation of the electrode devices (3), wherein, preferably, the estimated transmission characteristics is or are used for selectively controlling and/or supplying the electrode devices (3).

27. Method of any one of the claims 22 to 26, wherein the electrode devices (3) are supplied with energy in a wireless manner separately for each delivery of an electrical impulse (I).

28. Method of any one of the claims 22 to 27, wherein at least one of the electrode devices (3) generates an electrical impulse (I) corresponding to the time- varying magnetic field (H), in particular to the time-varying field strength over time of the time-varying magnetic field (H).