SEGMENTED FLAT ELECTRODE

Abstract

An electrode (10) for treating organic tissue by means of direct current, comprising an electrode holder (20), at least one electrically conductive electrode surface (30), which is let into the electrode holder (20), wherein the at least one electrode surface (30) is connected to at least one control element (400) and wherein the at least one control element (400) is connected to a control and energy supply unit by way of electrical lines (60, 70), wherein the at least one control element (400) is configured in such a way that each individual electrode surface (30) is actuable by the at least one control element (400) in such a way that a current density (J) provided within a predetermined interval for each one of the at least one electrode surfaces (30) can be maintained or that a current density (J) for each one of the at least one electrode surfaces (30) can be maintained around a predetermined value.

Claims

1-15. (canceled)

16. An electrode for treating organic tissue by means of direct current, comprising an electrode support, at least one electrically conductive electrode surface which is embedded in the electrode support, at least one control element, a control and power supply unit, at least one electric line connecting the at least one control element to the control and power supply unit, wherein the at least one electrode surface is connected to the at least one control element, wherein the at least one control element is configured in such a way that each individual electrode surface is controllable by the at least one control element in such a way that a current density provided within a predetermined interval for each one of the at least one electrode surface is maintained.

17. The electrode as claimed in claim 16, wherein the at least one control element is situated on the back or at the side of the at least one electrode surface.

18. The electrode as claimed in claim 16, wherein the at least one control element comprises a first control element and a second control element.

19. The electrode as claimed in claim 18, wherein the first control element is connected to the second control element by way of further electric lines, wherein the second control element is situated at a distance from at least one electrode surface.

20. The electrode as claimed in claim 19, wherein the second control element is situated in a connection area of the electrode having a supply line which includes the electric lines and can include the further electric lines.

21. The electrode as claimed in claim 19, being a segmented electrode having at least two electrically conductive electrode surfaces having each a first control element, wherein each of the first control elements is connected to a shared common control element.

22. The electrode as claimed in claim 16, wherein the at least one electrode surface is embedded in a shared, contiguous, integrally formed electrode support.

23. The electrode as claimed in claim 21, wherein at least two of the electrode surfaces are embedded in an electrode support surrounding the particular electrode surface, and the electrode supports are interconnected by way of a connection strand.

24. The electrode as claimed in claim 16, wherein the control element comprises a MOSFET or a bipolar transistor.

25. The electrode as claimed in claim 16, further comprising at least one one-way valve which permits the drainage of fluid which has accumulated under the electrode.

26. The electrode as claimed in claim 25, wherein the at least one one-way valve is situated within an electrode surface.

27. The electrode as claimed in claim 25, wherein the at least one one-way valve is situated between adjacent electrode surfaces.

28. The electrode as claimed in claim 25, wherein the at least one one-way valve is a diaphragm valve.

29. An electrode for treating organic tissue by means of direct current, comprising an electrode support, at least one electrically conductive electrode surface which is embedded in the electrode support, at least one control element, a control and power supply unit, at least one electric line connecting the at least one control element to the control and power supply unit, wherein the at least one electrode surface is connected to the at least one control element, wherein the at least one control element is configured in such a way that each individual electrode surface is controllable by the at least one control element in such a way a current density for each one of the at least one electrode surface is maintained around a predetermined value.

30. The electrode as claimed in claim 29, wherein the at least one control element comprises a first control element and a second control element, wherein the first control element is connected to the second control element by way of further electric lines, wherein the second control element is situated at a distance from at least one electrode surface, wherein the electrode is a segmented electrode having at least two electrically conductive electrode surfaces having each a first control element, wherein each of the first control elements is connected to a shared common control element.

31. The electrode as claimed in claim 29, wherein the at least one electrode surface is embedded in a shared, contiguous, integrally formed electrode support, and wherein at least two of the electrode surfaces are embedded in an electrode support surrounding the particular electrode surface, and the electrode supports are interconnected by way of a connection strand.

32. The electrode as claimed in claim 29, further comprising at least one one-way valve which permits the drainage of fluid which has accumulated under the electrode, wherein the at least one one-way valve is situated either within an electrode surface or is situated between adjacent electrode surfaces, and wherein the at least one one-way valve is a diaphragm valve.

33. A method for controlling the current density on an electrode for treating organic tissue by means of direct current, the electrode comprising an electrode support, at least one electrically conductive electrode surface which is embedded in the electrode support, at least one control element, a control and power supply unit, at least one electric line connecting the at least one control element to the control and power supply unit, wherein the at least one electrode surface is connected to the at least one control element, wherein the at least one control element is configured in such a way that the current flowing through each electrode is regulated in such a way either that a current density provided within a predetermined interval for each individual electrode surface is maintained or that a current density for each of the at least one electrode surface is maintained around a predetermined value.

34. The method for controlling the current density on an electrode as claimed in claim 33, wherein the electrode can be used as a current-supplying electrode or a current-receiving electrode.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Preferred embodiments of the invention are described in the following with reference to the drawings which are intended merely for the purpose of explanation and are not intended to be interpreted to be limiting. In the drawings:

[0042] FIG. 1 shows a single electrode according to the invention;

[0043] FIG. 2 shows a further embodiment of an electrode according to the invention;

[0044] FIG. 3 shows a further embodiment of an electrode according to the invention;

[0045] FIG. 4 shows an alternative embodiment of the electrode from FIG. 1;

[0046] FIG. 5 shows an alternative embodiment of the electrode from FIG. 2;

[0047] FIG. 6 shows an alternative embodiment of the electrode from FIG. 3;

[0048] FIG. 7 shows a schematic diagram of the control circuit;

[0049] FIG. 8 shows a MOSFET control element;

[0050] FIG. 9 shows a bipolar control element;

[0051] FIG. 10 shows an electrode according to the invention during use; and

[0052] FIG. 11 shows an electrode according to the invention comprising a one-way valve.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0053] FIG. 1 shows a single electrode 1 according to the invention comprising a first electrode support 2, in which a first electrode surface 3 is embedded. The first electrode support 2 surrounds the first electrode surface around the sides and the back, at least partially, preferably completely. The electrode surface 3 is connected by way of an electric line 600 to a first control element 4 which is situated at a distance from the electrode surface 3 in a supply line 200 and which is connected by way of electric lines 60, 70 to a control and power supply unit 900 depicted in FIG. 10. The first control element 4 can be situated close to the electrode surface 3, i.e., in the connection area having the supply line 200, in the control and power supply unit 900, or therebetween. The current density J of the electrode surface 3 can be controlled/regulated by means of the first control element.

[0054] A non-illustrated second control element 5 (see FIG. 5) can be situated together with the first control element 4, adjacent thereto, or in the control and power supply unit 900.

[0055] An electrode surface can possibly detach from the tissue on which it preferably completely rests. If the electrode is then regulated in such a way that a constant current I flows therethrough, the current density increases when the electrode becomes detached, since the area through which the current I can flow is reduced.

[0056] Given, for example, an electrode surface 3 which is 100 square centimeters in size, and a direct current I of 1 milliampere, the current density is 0.01 milliamperes per square centimeter. If the electrode surface detaches from the tissue, then only 10 square centimeters (i.e., one-tenth), for example, are still in contact, in which current can flow. If constant-current regulation were applied, the current density would increase ten-fold, to 0.1 milliamperes per square centimeter, since the area has become ten times smaller due to the detachment. Such high current densities are undesired, since they can trigger cardiac arrhythmia, for example.

[0057] The electrode 1 optionally comprises at least one one-way valve 21 which essentially comprises an opening 22 and a diaphragm 23 covering the opening 22 on the outer side. A schematic sectional view of the one-way valve 21 is depicted in FIG. 11. The diaphragm is made from silicone, for example. The at least one one-way valve 21 is situated within the electrode surface 3.

[0058] FIG. 2 shows yet another embodiment of a segmented electrode 10 according to the invention. The electrode 10 comprises multiple electrode surfaces 30 which are separated from one another and are embedded in a shared, second electrode support 20.

[0059] All electrode surfaces 30 are of the same size and are situated in pairs, symmetrically with respect to the longitudinal central axis of the electrode. Eight electrode surfaces 30 are shown, wherein four are situated on one side of the longitudinal central axis and four are situated on the opposite side of the longitudinal central axis.

[0060] The electrode support 20 comprises a border 26 which laterally encloses all electrode surfaces and comprises webs 25 which separate the individual electrode surfaces from each other, wherein the web lying on the longitudinal central axis is a central web 27 which contains the electric lines 600 which connect a control module 400 to the individual electrode surfaces 30. The control module 400 comprises multiple control elements 4 which control/regulate the current density J in the particular electrode surface. The number of control elements 4 per control module 400 correlates with the number of electrode surfaces 30.

[0061] Electric lines 60, 70 connect the control module 400 to the non-illustrated control and power supply unit 900. The second control element 5 (not shown) can be disposed in the control module 400, adjacent thereto, or in the control and power supply unit 900. In other words, situated between the control and power supply unit 900 and the control module 400 are electric lines 60, 70, in particular, which are used for the power supply and can establish the connection to the battery provided there.

[0062] In the depicted arrangement, the electrode surfaces 30 are situated opposite one another with respect to the longitudinal central axis of the electrode 10 in groups of two and form one pair of electrode surfaces in each case. Four such pairs are situated next to one another in the direction of the longitudinal central axis.

[0063] The use of a plurality of electrode surfaces 30 has the advantage that, if one of the electrode surfaces 30 becomes detached, the current density J of the corresponding electrode surface can be regulated in such a way that it does not exceed an established value and the remaining electrode surfaces 30 of the segmented electrode 10 are not adversely affected thereby.

[0064] The electrode 10 comprises at least one one-way valve 21. The at least one one-way valve 21 can be situated within the webs 25. Alternatively or additionally, said valve can be situated within an electrode surface 30. Alternatively or additionally, said valve can be situated within the central web 27.

[0065] Alternatively or additionally, said valve can also be situated in the middle of four adjoining electrode surfaces 30, i.e., at intersections of the webs 25 and the central web 27. The at least one one-way valve 21 is designed in such a way that fluid which accumulates under the electrode surface 30 can reach the back side of the electrode 10 in only one direction through said electrode.

[0066] FIG. 3 shows one alternative embodiment of a segmented electrode 11 according to the invention. In contrast to the previous embodiment, each of the individual electrode areas 30 is embedded in separate electrode supports 2 which are connected to one another by means of a connection strand 201.

[0067] As in the previous embodiment, a control module 400 is provided, by means of which the current density J of each electrode area 30 can be controlled/regulated. In turn, the control module 400 is connected to the non-illustrated control and power supply unit by way of electric lines 60, 70 which are routed in the supply line 200.

[0068] Electric lines 600 extend from the control module 400 to the particular electrode surface 30. The electric lines 600 are routed in the connection strand 201. The connection strand comprises lateral branches along its longitudinal direction, each one of which leads to an electrode surface 30.

[0069] The electrode 10 can comprise at least one one-way valve 21 which is situated within an electrode surface 30.

[0070] In the case of the electrode surfaces 3, the electrodes 1, 10, 11 depicted in FIGS. 1 to 3 are knitted fabrics or woven fabrics made of thin, conductive, biocompatible metal wires having low polarization, for example, of platinum or platinum iridium. Alternatively, thin metal foils can be used instead of the knitted fabrics or woven fabrics.

[0071] FIG. 4 shows one alternative embodiment of the electrode from FIG. 1. In contrast to the embodiment from FIG. 1, the first control element 4 is situated directly on the electrode surface 3. Electric lines 6, 7 are routed in the supply line 200 and are connected to the non-illustrated control and power supply unit 900. The second control element 5 can again be situated in the first control element 4, adjacent thereto, or in the control and power supply unit 900.

[0072] Further electric lines 8 can likewise lead up to the second electrode support 20. Said electric lines can be measuring lines which are required for measuring the EKG or impedance.

[0073] FIGS. 5 and 6 show one alternative embodiment of the electrode from FIGS. 2 and 3, respectively. In contrast to the embodiment from FIGS. 2 and 3, the first control element 4 is situated directly on the electrode surfaces 30. The first control elements 4 of the electrode surfaces 30 are connected to one another and to the second control element 5 by way of electric lines 60, 70.

[0074] The electrode surfaces 3 of the electrodes 1, 10, 11 depicted in FIGS. 4 to 6 are thin, conductive, biocompatible metal foils having low polarization, being made, for example, of platinum or platinum iridium. Alternatively, knitted fabrics or woven fabrics made of thin metal wires can be used instead of the metal foils.

[0075] FIG. 7 shows a schematic diagram of the control circuit of an electrode arrangement according to the invention comprising an electrode 10 and a counterelectrode 100 of the type in use in FIG. 10. The control circuit comprises, for each electrode surface 30, a first control element 4 in the form of a constant-current source, and comprises a second control element 5 which establishes the polarity of the first control elements 4.

[0076] The first control element 4 is preferably a transistor-based control element, for example, a first control element 4 having a MOSFET transistor 9 or an alternative first control element 4 having a bipolar transistor 90.

[0077] Viewing FIG. 2 and FIG. 7 in combination reveals the possibility of providing only the control with the first control elements 4 on the implant, on the patch electrodes, and of moving the second control with the second control elements 5 to another point, as indicated by way of the connection labeled with the reference numbers 60 and 70 which, in the exemplary embodiment according to FIG. 2, establish the connection to the outside, where the control and power supply unit 900 is located, i.e., in deviation from the exemplary embodiment according to FIGS. 5 and 6.

[0078] FIG. 8 shows a schematic illustration of a MOSFET control element 40 comprising a MOSFET transistor 9, and FIG. 9 shows a schematic illustration of a bipolar control element 41 having a bipolar transistor 90.

[0079] The bipolar control element 41 is described in greater detail in the following with reference to FIG. 9. The principle of current regulation for a current direction (predefined polarity) can be implemented by means of a bipolar transistor 90, an emitter resistor R7, and a reference voltage at the base of the transistor. The emitter resistor R7 is situated at the reference potential (at the positive or negative supply voltage for the current regulator). The collector output is connected to the electrode 10 which rests flat on the heart muscle.

[0080] As depicted in FIG. 10, the current circuit is closed via the second counterelectrode 100 lying on the opposite side of the heart. The opposite electrode is likewise provided with current regulators, in order to ensure a defined distribution of the current.

[0081] Alternatively, the current circuit can be closed via the control and power supply unit 900. In this case, only one electrode 10 is present, however.

[0082] Diodes D6, D7 in the collector lines provide for the intended current direction, for example, of the PNP and NPN transistors. Independently of the intended current direction, the diodes perform a protection function, in order to prevent a control of the bipolar transistors 90 along the collector-base path.

[0083] Safety considerations (limitations of high frequencies) are the reason for dispensing with a Miller capacitor (negative feedback capacitor between the collector and the base), in order to prevent feedback from the electrode via the collector onto the base. The limiting of high frequencies is achieved by means of further capacitors.

[0084] The voltage drop, measured across the emitter resistor R7, determines the constant current at each individual electrode 1 or each individual electrode segment 10. This voltage can be changed via the control line which leads to the bases of the transistors. As a result, the setpoint current (therapy current), which is supposed to flow through the heart muscle via the corresponding electrode surface, is set.

[0085] Each individual transistor automatically regulates itself via its own emitter, as a voltage probe, and thereby maintains the setpoint current which has been set, in the presence of fluctuating transistion resistances, without feedback loops to the control and power supply unit.

[0086] The automatic regulating range (change in internal resistance of the transistor) is multiple times larger than the adjustment range via the control voltage.

[0087] On the basis of the control voltage between the main line and the base, minus the base emitter voltage U.sub.BE of approximately 0.6 volt which drops across the base-emitter path, the constant current can be calculated according to Ohm's law:

(U−U.sub.BE)/R=I

wherein U.sub.BE=0.6 volt

[0088] Since the desired current lies in the μampere range, 0.6 volt should be taken into account, instead of 0.7 volt which is typical.

[0089] The emitter resistor R7 should have a size of 20-100 kiloohms, depending on the number of desired electrode segments and the current range which is used.

[0090] For medical reasons and due to electrochemical effects, the current direction should be changeable (change the polarity). For this reason, a second transistor (NPN-PNP) having a diode is required in the collector line.

[0091] For the particular other current direction, the polarity of the lines to the electrodes can be switched electronically in the control and power supply unit. This applies for the line for the control voltage just as it does for the lines for the therapy current.

[0092] In order to switch off the therapy current, the voltage can be lowered to below a threshold of 0.4 volt at at least one of the two control lines. For safety reasons, in addition to lowering the voltage below the aforementioned limit of 0.4 volt, it is provided that the corresponding analog switch is switched to high impedance. For this reason, analog switches having 3 connectors cannot be used.

[0093] The resistor R6 has relevance for the case in which the surface element of the electrode has a high resistance to the heart muscle (loss of contact). In this case, the regulating transistor would attempt to draw the missing current across the base. The resistor (R6, approximately 50-150 kiloohms) limits the lost current to tolerable values. In such a configuration, the resistor R6 is connected in series to the resistor R7.

[0094] The current loss which sets in can be calculated from the control current minus U.sub.BE 0.6 volt divided by (R6+R7).

[0095] In normal operation (good contact of the electrode to the heart muscle), the largest portion of the therapy current flows across the collector and only a minimal residual current flows across the base. In the case of amplification factors of 100 to 300, the size of the residual current is only approximately 1 to 0.33 percent of the therapy current.

[0096] The resistor R5 [100-500 ohms] has the function of a protective resistor and, together with the diode D8 [two 12-14 volt zener diodes connected back to back], forms a bidirectional overvoltage protection D8. The voltage for the zener diodes is selected to be so high because the zener diodes have a substantially lower leakage current starting at approximately 10-12 volts.

[0097] This not only has to do with static discharges which should be dissipated, but also with an effective protection against the defibrillator pulse having an amplitude of up to 1500 volts for 10 milliseconds (25 amperes). Therefore, the resistor must withstand impulse voltages of 1500 volts.

[0098] Capacitors C5, C6 are provided for protection against incident high frequency and against the inherent tendency to oscillate. The regulating transistor, by way of its stepless analog regulating task, can find a working point at which it starts to oscillate.

[0099] The capacitors are dimensioned in such a way that the correction time does not adversely affect the function. A proven standard value is 100 nanofarads for C6 and 10 nanofarads for C5, if the size of the capacitors does not play a role. In the present application within the electrode, values of 10 nanofarads (dielectric strength 10 volts) for C6 and of 5 nanofarads (voltage strength 20 volts) for C5 are also acceptable. It is permissible for the capacitance to deviate greatly upward in the event of a temperature change, but the indicated capacitance must not be fallen below.

[0100] Given a predefined overall surface area F of 6×8 centimeters, an area F of 48 square centimeters results. In the case of a setpoint current density J, for example, of 0.001 milliamperes per square centimeter, a required current I of 0.048 milliamperes results.

[0101] For 12 individual surfaces N, for example, wherein each surface has 4 square centimeters, this means that each surface has a maximum current I of 0.004 milliamperes which may be given off, as the maximum, as therapy current.

[0102] A value R of 40 kiloohms results for R7. The control voltage is calculated as follows:

R/N=3.33 kiloohms×I=0.16 volt=U,

wherein R=40 kiloohms, N=12, I=0.048 milliamperes

U+u=0.16+0.6=0.76 volt=U.sub.max

wherein u=0.6 volt (voltage drop)

[0103] A maximum control voltage of 0.76 volt must be available in parallel for all 12 current regulators for a multisensor electrode having 12 surfaces.

[0104] The setpoint current density can be maintained in an interval of 0.1 to 20 milliamperes per square centimeter, preferably between 1 to 15 microamperes per square centimeter, preferably between 5 and 10 microamperes per square centimeter. Alternatively, the current density J can be maintained around a value contained in the aforementioned intervals. For example, the current density can be maintained around 10 microamperes per square centimeter.

[0105] If a MOSFET transistor 9 is used instead of a bipolar transistor 90, as depicted in FIG. 8, the threshold voltage increases relative to the control voltage to approximately 0.8 volt (this is the gate voltage at which MOSFETs just start to conduct), and a voltage drop of 0.25 volt occurs across the Schottky diodes D4, D5 situated in front of the gate. This results in a threshold voltage of 1.05 volts relative to the control line.

[0106] The temperature behavior of the diodes counteracts the temperature behavior of the MOSFETs. MOSFETs 9, in contrast to bipolar transistors 90, become higher-impedance when heated.

[0107] The primary task of the diodes D4, D5 is to prevent a discharge current across the internal protective diodes of the MOSFETs. Only 2 diodes are required for all current regulators. The gates of the P-channel MOSFETs can also be connected directly in parallel, as is the case with all N-channel MOSFETs.

[0108] The resistors R2, R4 (1 megaohm each) are high-impedance and are intended to ensure a reliable blockage of the MOSFETs. This is necessary due to the diodes. Two resistors are sufficient for all individual areas of the multi-area electrode.

[0109] The capacitors C3, C4, as is also the case with the capacitors C1, C2, are provided as protection against incident high frequency and against the tendency to oscillate (no difference from the circuit having the bipolar transistors). In this case as well, two capacitors C3, C4 suffice for all individual surfaces. While C3 and C4 are sufficient for all current regulators, the capacitors C1 and C2 should be provided in each current-regulating circuit.

[0110] FIG. 10 shows an electrode 10 according to the invention in use, wherein said electrode is situated on a first outer surface of the heart H of a patient P, and a counterelectrode 100 is situated on a second outer surface of the heart H, which is essentially opposite the first side. Preferably, the electrode 10, essentially, and the counterelectrode 100 are situated on a front and a rear surface, respectively, of the heart. Alternatively, the electrodes can also be situated on a left- or right-oriented surface of the heart. The advantage of these arrangements is that the current flows substantially through the heart or through the heart muscle.

[0111] The counterelectrode 100 can be designed identical to or substantially identical to the opposite electrode 10. Said electrode can also have a different distribution or segmentation of the electrode surfaces.

[0112] Supply lines 200 extend from the electrodes 10, from each electrode 10, 100 to a shared control and power supply unit 900 which, for example, comprises a generator and receiving unit, a telemetry unit, and a power supply unit.

[0113] An electrode according to the invention makes it possible to improve the effect of the treatment while simultaneously increasing the safety of the treatment.

LIST OF REFERENCE NUMBERS

[0114] 1 individual electrode [0115] 10 segmented electrode [0116] 100 counterelectrode [0117] 11 alternative segmented electrode [0118] 2 first electrode support [0119] 20 second electrode support [0120] 200 supply line [0121] 201 connection strand [0122] 21 one-way valve [0123] 22 opening [0124] 23 diaphragm [0125] 25 web [0126] 26 border [0127] 27 central web [0128] 3 first electrode surface [0129] 30 second electrode surface [0130] 4 first control element [0131] 40 MOSFET control element [0132] 400 control module [0133] 41 bipolar control element [0134] 5 second control element [0135] 6-8 electric line [0136] 9 MOSFET transistor [0137] 90 bipolar transistor [0138] 900 control and power supply unit [0139] R1-R7 resistor [0140] D1-D8 diode [0141] C1-C6 capacitor [0142] I current [0143] J current density [0144] U voltage [0145] P patient [0146] H heart