Implantable device

The invention relates to a permanently or temporarily implantable device with an elongated electrical conductor.

Such devices, for example, electrode lines for electrostimulation, have the disadvantage that their electrical conductors may heat up in an MRI scanner because the ruling in MRI scanners alternating magnetic fields in the electrical conductor induce not inconsiderable electric currents. Also, such induced currents can be delivered via electrode poles of the electrode line to surrounding tissue and thus, for example, lead to undesired tissue warming. Therefore, cardiac pacemaker patients today can usually not be examined or only to a limited extent in a magnetic resonance tomograph.

An implantable cardiac pacemakers or defibrillators (hereinafter also collectively (as cardiac stimulators or IPG implantable pulse generator) hereinafter) are in fact typically at least one stimulation electrode lead is connected, which at its proximal, provided for connection to the pacemaker or defibrillator end of a standardized electrical connection and has one or more electrode poles at its distal end provided for placement in the heart. Such an electrode pole serves to deliver electrical impulses to the tissue (myocardium) of the heart or to sense electric fields in order to be able to sense an activity of a heart within the framework of so-called sensing. For these purposes, electrode poles typically form electrically conductive surface portions of an electrode lead. Electrode poles are typically provided as a ring electrode in the form of a ring around the electrode lead or in the form of a tip or tip electrode at the distal end of the electrode lead. The electrode poles are electrically conductively connected via one or more electrical conductors to contacts of the electrical connection of the electrode line at its proximal end. Thus, between the contacts of the electrical connection, the electrode leads extend at the proximal end thereof and the electrode poles at the distal end of the electrode lead one or more electrical conductors electrically connecting one or more of the electrode poles to one or more of the contacts. These electrical conductors can, on the one hand, be used for transmitting stimulation pulses to the electrode poles and, on the other hand, for transmission by means of the electrode poles of recorded electrical signals to the proximal end of the electrode line and will also be referred to as function lines in the course of the further description. Such function lines are electrical conductors required for the functions of the respective electrode line and, as such, are exposed to the danger that electrical currents are induced in them by external alternating magnetic fields.

The <patcit id="pcit0001" dnum="WO2008073445A2A"><text>PCT application WO2008073445A2</text></patcit> describes an electrode lead suitable for use in a magnetic resonance tomograph.

The invention has for its object to provide a device which solves the problem described above.

According to the invention this object is achieved by a temporary or permanent implantable medical device, which is connected to at least two elongated electrical function conductors for the transmission of therapy signals or diagnostic signals, or both, or to join, and at least one associated with at least one of the functional lead electrode pole, electric over the Power can be delivered to surrounding body tissue in the case of use or can be sensed with the electrical potential in tissue surrounding in the case of use, or both.

According to the invention, the medical device has a wave transfer module, which is connected or connectable to the functional conductor and which is designed to transform waves arriving via a functional conductor and to switch them as transformed waves onto another functional conductor or the same functional conductor in such a controlled manner that the waves Overlap destructively at the electrode pole.

A medical device for which the invention is particularly relevant is an electrode lead, for example for a heart stimulator, in which the functional conductors are electrical conductors of the electrode lead, wherein the electrode lead has electrode poles, which are electrically connected to the wave transfer module via the function leads.

The medical device, for example an implantable heart stimulator connected to an electrode line, may have a housing which is electrically conductive or has an electrode pole via which electric current can be delivered to surrounding body tissue or sensed with the electrical potential in surrounding tissue both.

Preferably, the medical device comprises an interference field detection device which is designed to detect the presence of strong electromagnetic fields and to generate a corresponding output signal if present, and which is connected to a control unit for controlling the shaft transfer module.

The interference field detection device may include a temperature sensor arranged to detect heating of an electrode pole. In this way, the interference field detection device detects a heating as a result of high-frequency interference fields and thus interference fields indirectly on their effect. The temperature sensors are located at the electrode poles or other locations that may heat up due to interactions with electromagnetic fields.

Alternatively or additionally, the interference field recognition device can have a sensor for currents or voltages induced in a function conductor and thus be configured to directly detect induced currents or voltages.

The wave transfer module comprises a delay line, delaying the electromagnetic waves and or attenuates, so that a transformed wave is formed in the operating case, the destructively overlaid with an induced wave on the same or another function head and the induced wave compensated in this manner. The delay line may have an impedance that causes this effect.

According to one embodiment, the delay line is realized by one or more, preferably discrete electronic components from a group comprising coils, capacitors, ohmic resistors and transformers (pulse transformer). These form, for example, an LC circuit, possibly also with an ohmic resistance, in order to set the damping.

Additionally or alternatively, the delay line can have spatial structures that have wave-delaying and / or damping effect due to their physical properties. Such spatial structures are not necessarily discrete electronic components but, for example, a waveguide, a coaxial line, a strip line, with possibly lossy materials to adjust the attenuation. Here, the wave transfer module is preferably adjustable in terms of its effect, in particular with regard to its delay effect and / or its damping effect, for example by the adjustable elements are operated electrically, mechanically, optically etc .. The setting of the controllable delay lines can also be done by an external programmer.

It makes sense for the wave transfer module to have a switching unit which is arranged and configured to switch on or off transformed waves to a function conductor determined by the switching unit. This makes it possible to use the shaft transfer module only if it is necessary and beyond to adapt to the particular application. The adjustment of the switching unit can also be done by an external programmer.

According to a preferred embodiment variant, a delay line of the shaft transfer module connects at least two function conductors, wherein the connection is to be established via the switching unit. The switching unit may take the form of a switching matrix in which each cross point in the switching matrix is ​​occupied by a switch.

In accordance with another embodiment, the medical device may include a termination impedance unit, and the shaft transfer module may include a switching unit that is arranged and configured to connect a function conductor to a termination impedance unit. The termination impedance can cause a phase shift of a wave on a function guide and thus also contribute to the desired effect of wave cancellation. For this purpose, preferably at least one impedance value of the terminating impedance unit is electrically, mechanically or optically controllable. The termination impedances can be realized discretely or physically. The setting of the controllable terminating impedances can also be done by an external programming device.

The control unit is preferably designed to control the controllable delay lines and / or the controllable terminating impedances and / or the switching unit in dependence on an output signal of the interference field recognition device in such a way that an interference-induced heating at the electrode poles is minimized.

Particularly preferred is a battery-operated electronic implant with an electrically conductive housing or housing with at least one Elektrodenpol, electrical function conductors that connect electrode poles electrical feedthroughs of the implant to conduct electrical signals from the respective Elektrodenpol in the implant can, an interference field detection device for detecting the presence strong electro-magnetic fields in particular MRI fields, and a Wellentransfermodul which is controlled by the Störfeldkennungsvorrichtung via a control device and the at least one functional conductor in the implant incoming waves so transformed and aufschaltet on at least one other function conductor, that the waves at the distal Elektrodenpolen destructively overlay,so that there MRI-related heating is minimized.

As an alternative to a controllable terminating impedance, it is also possible to provide a controllable generator which is designed to actively feed a compensation signal into a functional conductor. The compensation signal to be injected has the same frequency as the interference signal and a specific phase position wherein the frequency is determined by the Störfeldkennungseinheit and the phase position and amplitude after evaluation of the temperature signals are adjusted so that the interference field induced heating at the Elektrodenpolen (if necessary, the temperature measuring points ) is minimized.

The invention will now be explained in more detail by means of embodiments with reference to the figures. The figures show the following:<dl id="dl0001"><dt>Fig. 1</dt><dd>shows an implantable cardiac stimulator 10 and an implantable electrode lead 20 connected thereto as implantable medical devices.</dd><dt>Fig. 2</dt><dd>shows in a highly schematic representation of the internal structure of a heart simulator according to the invention.</dd><dt>Fig. 3</dt><dd>shows a highly schematic representation of a structure of a delay line.</dd></dl>

The implantable cardiac stimulator 10 may be a pacemaker or a cardioverter / defibrillator (ICD). In the illustrated embodiment, the heart stimulator 10 is a ventricular pacemaker and defibrillator. Other known cardiac stimulators are dual chamber pacemakers for stimulation of the right atrium and the right ventricle or biventricular pacemakers, which can also stimulate the left ventricle in addition to the right ventricle.

Such stimulators typically have a housing 12, which is usually made of metal and thus is electrically conductive and can serve as a large electrode pole. On the outside of the housing 12, a terminal housing 14 is typically attached, which is also referred to as a header. Such a header typically has contact sockets for receiving plug contacts. The contact sockets have electrical contacts 16, which are connected via corresponding conductors with an arranged in the housing 12 of the heart stimulator 10 electronics.

For the purposes of this invention, the electrode line 20 likewise constitutes an implantable medical device. Electrode poles in the form of a tip or tip electrode 22 and a ring electrode 24 arranged in the vicinity thereof are arranged at the distal end of the electrode line 20 in a manner known per se. The electrode poles 22 and 24 are designed such that, depending on the function of a cardiac stimulator to which the electrode lead 20 is connected, they serve to sense electrical potentials of the heart tissue (myocardium) or to emit electrical signals, for example to deliver stimulation pulses to the surrounding area Heart tissue, are formed.<figref idref="f0001">FIG. 1</figref> shows how the electrode poles, so the tip electrode 22 and the ring electrode 24, in the application, the electrode line 20, located in the apex of a right ventricle of a heart.

Both the tip electrode 22 and the ring electrode 24 are electrically connected via at least one electrical conductor 26 with a plug contact 28 at the proximal end of the electrode line 20. The plug contact 28 has electrical contacts which correspond to the electrical contacts 16 of the contact socket in the connection housing 14 of the implantable cardiac stimulator. The electrical conductors 26 in the electrode line 20 may be formed as approximately elongated cable conductor or as a helical coiled conductor. Such conductors which electrically conductively connect functional electrode poles to electrical contacts of the plug-in contact at the proximal end of the electrode line 20 are referred to as function conductors in the context of this text,

The electrical conductors 26, which connect the electrode poles 22 and 24, respectively, to the electrical contacts of the plug 28 of the electrode line 20, are surrounded over most of their length by an insulating sheath, so that an electrical contact to the tissue of the heart is targeted via the electrode poles comes about.

In addition to the electrode poles 22 and 24, which typically serve the (in this case, ventricular) stimulation of the heart tissue, the electrode line 20 also has two larger-area electrode poles 30 and 32, which serve as defibrillation electrodes and are formed by at least one bare helix-like coiled wire ,

It should be noted that the invention is explained in the context of this embodiment with reference to a right ventricular pacemaker and defibrillator. As a medical device in the context of the invention may in principle but for example also serve an ablation electrode, which also protrudes in the application to the heart of a patient and which is controlled by a device disposed outside the patient and is connected thereto.

<figref idref="f0002">FIG. 2</figref> shows a schematic representation of the internal structure of a medical device according to the invention. The medical device has an electrically conductive housing 100, which is made of the housing 12<figref idref="f0001">FIG. 1</figref> equivalent. Connected to the housing are two electrode lines 102 and 104, each having a tip electrode 106 and a ring electrode 108. Each of the tip electrodes 106 and the ring electrodes 108 forms one electrode pole, respectively. Each electrode pole is connected via a separate supply line 110 to an electronics inside the housing 100. The supply lines 110 each form a functional conductor. In each case in the immediate vicinity of the electrode poles 106 and 108 temperature sensors 112 are arranged, which are connected via signal lines 114 to a control unit 116 in the interior of the housing 100.

Instead of the temperature sensors 112, other sensors may be used to detect electromagnetic interference fields or currents or voltages induced in the leads 110.

The leads 110 (function guide) and the signal lines 114 are over in <figref idref="f0002">FIG. 2</figref> not shown plug and guided through housing feedthroughs 140 in the housing 100. The function ladder 110 is connected to the typical components of a heart stimulator as well as sensing units or stimulation units. This is in<figref idref="f0002">FIG. 2</figref> represented by the block 118, which represents the sensory and therapeutic pacemaker electronics.

In <figref idref="f0002">FIG. 2</figref> It is shown that the functional conductors 110 are guided, on the one hand, to the pacemaker electronics 118 and, on the other hand, to switching units 120 and 122, which are designed as switching matrices. Connected to the switch matrices 120 and 122 is a wave transfer module 124 which has (in the illustrated case three) adjustable delay lines 126. The delay lines 126 are adjustable in terms of their delay effect and / or their damping effect. For this purpose they are connected via control lines 128 to the control unit 116. In this manner, they may be received by the controller 116 in response to the signals that the controller 116 receives via the signal lines 114 from the sensors 112 in the electrode lines 102 and 104. Specifically, the control unit 116 is configured to Both the switching matrices 120 and 122 and the delay lines 126 in response to the signals received via the signal lines 114 to receive so that the signals received via the signal lines 114 indicate as possible no heating of the electrode poles 106 and 108. In this sense, the control unit 116 can also be regarded as a controller.

The latter effect is achieved by means of the adjustable delay lines 126 by switching incoming waves via the function conductors 110 to the adjustable delay lines 126 and adjusting the delay lines 126 so that the waves are transformed in one way and onto the same or other functional conductors be switched so that they interfere destructively with induced waves and so cancel the effect of the induced waves.

Alternatively or additionally, this purpose is served by a terminating impedance unit 130, which in the specific case has three adjustable terminating impedances 132. The adjustable impedances 132 may be adjusted by the control unit 116 via control lines 134. The adjustable terminating impedances 132 allow the reflection of the waves on the function conductors 110 at their proximal ends defined by the termination units to be adjusted in terms of phase position and attenuation in order to likewise achieve a destructive superposition of waves in the region of the electrode poles of the respective function conductors.

Instead of the terminating impedance unit 130, it is also possible to provide a compensation signal generator which actively and by the control unit 116 generates compensation signals and feeds them into the respective functional conductor.

It should be noted that the housing 100 of the heart stimulator is a separate pole, which is also electrically connected (see reference numeral 136) to the switch matrices 120 and 122 and the heart stimulator electronics 118.

The control unit and thus the behavior of the switching units 120 and 122 and the settings of the delay lines 126 and the terminating impedances 132 are externally programmable. This is indicated by the arrow 300.

The structure of an exemplary delay line is in <figref idref="f0003">FIG. 3</figref> shown schematically. In<figref idref="f0003">FIG. 3</figref> the reference numbers indicate<dl id="dl0002" compact="compact"><dt>200:</dt><dd>Conductive implant housing</dd><dt>210:</dt><dd>Conduction of an electrode</dd><dt>211:</dt><dd>Leading an electrode (the same electrode as 110 or another)</dd><dt>220:</dt><dd>Wave transfer module</dd><dt>230:</dt><dd>Head of the delay line</dd><dt>240:</dt><dd>Reference conductor of the delay line</dd><dt>250:</dt><dd>Connection of the reference conductor of the delay line to the implant housing</dd><dt>260, 261:</dt><dd>counter</dd><dt>270, 271:</dt><dd>Connection to the electronics</dd></dl>

Upon detection of a strong electromagnetic field (in particular RF fields as they occur in MR scanners and pose a risk potential for patient and implant) by the temperature sensors 112 and the control unit 116, which form an interference field detection unit in this sense, the wiring of the electrode inputs is automatically in Implant reconfigured. This causes the control unit 116, which is programmed or constructed accordingly. This wiring occurs only temporarily while the fault is present, in everyday operation of the implant, the high-resolution and broadband signal recording, in particular the impedance detection for a hemodynamic sensor, not affected. Then the electrode leads run directly (as is conventional) into the electronics 118 of the heart stimulator. In a preferred implementation, during the fault and circuit according to the invention with delay lines, the electronics 118 are switched off at some or all inputs. An intended, controlled by the control unit 116 switch is in<figref idref="f0002">FIG. 2</figref> not shown.

In <figref idref="f0002">FIG. 2</figref> an optional additional disturbance detection unit 150 is shown which generally responds to disturbance fields and in this case activates the control unit 116 for the duration of the disturbance fields or a predetermined period of time as described above.

In a preferred implementation, the coupling of the supply lines by means of the switching matrices 120 and 122 is carried out so that, for example, the inner conductor of a first electrode (coaxial) is connected to the outer conductor of a second electrode. In a further realization, the inner conductor of the second electrode is simultaneously switched to the outer conductor of the first electrode (cross-connection). In another implementation, the delay is almost 0 seconds, ie it is directly connected without the use of delay lines.

In the wiring of the electrodes, in addition to the optimization of the heating, care is taken that the areas enclosed between the electrodes are minimal. This minimizes the stress induced by MRI gradient fields and reduces the risk of unwanted heart stimulation (induced by the MR scanner). In particular, no connection is made to the housing potential.