AU2006201231B2 - An electrical lead - Google Patents

Description

AUSTRALIA

Patents Act 1990 CATHRX PTY LTD COMPLETE SPECIFICATION STANDARD PATENT Invention Title: An electrical lead The following statement is a full description of this invention including the best method of performing it known to us:- An electrical lead Field of the Invention The present invention relates to medical electrical leads and electrodes and in particular to medical leads having electrodes made from a metal-coated polymeric material.

Background Art Electrical leads and electrodes are commonly utilised in the medical field for applications such as stimulation, sensing, ablation and defibrillation.

Traditionally, medical electrodes comprise machined metal or coiled metal wire components which, while suitably conductive, do not provide the flexibility in both design and mechanical properties afforded by a metal coated polymer. Furthermore, metal coated polymers are particularly suitable for use in larger area electrodes where their light weight, flexibility and versatility are key advantages.

The use of metal coated or metal filled polymers as medical electrodes has been considered. For example, in US 5,279,781, a metal filled fibre for use as a defibrillation electrode is described. The metal in this case is added during the spinning process. To render the electrode suitably conductive, however, requires the addition of a significant proportion of metal to the fibre which in turn has an adverse effect on the mechanical strength of the electrode.

Further structures, including metal filled silicones and intrinsically conductive polymers, have been considered for use as medical electrodes although it has been found that such structures do not have the required level of conductivity necessary for the abovementioned medical applications.

Typically, the problem encountered with using a polymeric material as an electrode is that it is difficult to obtain a good electrical connection to the electrode. In US 5,609,622, an electrical connection was achieved by utilising an electrode having metal wires embedded in its wall. The electrode was then subjected to an ion beam treatment with metal such that the metal was deposited within the wall and therefore contacted the wires. In this case, however, the electrical connection was only shown to occur at one end of the electrode and further, it is questionable whether a good connection is achieved by this method as it relies upon the incidence of metal contacting wire through the thickness of the plastic.

The present invention provides an electrical lead and/or electrode which overcomes the problems of the prior art.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

Disclosure of the Invention Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

According to a first aspect of the invention, there is provided an electrical lead comprising an elongate body, the body having at least one electrically conductive region, the region being defined by a porous polymeric material, having a plurality of pores therein, coated with an electrically conductive material, wherein the pores extend transversely to a longitudinal axis of the elongate body and extend at least partly through a wall of the elongate body; and at least one electrical conductor embedded in the elongate body and extending into the at least one electrically conductive region so that the at least one conductor is in communication with a number of the pores of the at least one electrically conductive region.

Preferably, the electrical lead is adapted for medical use and in particular, but not limited to, use in cardiac mapping, defibrillation or pacing, neurological applications including neural stimulation implants, muscle stimulation, sensing and ablation.

Typically, the electrically conductive member is an elongate tube. While the entire length of the member may be made from a porous polymer coated with an electrically conductive material it is also envisaged that the electrically conductive member may comprise a plurality of distinct, spaced, electrically conductive regions made up of the coated porous polymer.

In the embodiment wherein the electrical lead is tubular, it is preferred that the pores of the at least one electrically conductive region extend at least partially through a wall of the tubular elongate body. Accordingly, in this embodiment, electrical connection may be made from within a lumen of the tube. It is further envisaged that electrical connection may be made from within the wall of the tube as further discussed below.

Rather than a tube, the electrical lead may comprise a solid cylindrical member.

In this embodiment, it is again preferred that the pores of the at least one electrically conductive region extend transversely at least partially through the cylindrical member.

In a preferred embodiment, the pores of the polymeric material may have a diameter greater than about 5 microns and preferably between about 30 and about 100 microns. When the porous polymeric material is coated with an electrically conductive material, said electrically conductive material preferably coats and lines at least some of, and preferably all of, the pores.

Typically, the electrically conductive material is a metal and, preferably, a biocompatible metal such as platinum. It is envisaged that a combination of at least two metals or metal alloys may be used, however, to improve electrical conductivity.

For example, it may be desirable to provide a first layer of copper or silver or any other suitably conductive metal and a second layer of platinum to enable use of the electrically conductive member within a body.

The coating of the porous polymeric material preferably creates a suitably thick layer of metal coating across the at least one electrically conductive region. Preferably, the resistance of the coating is less than 100 ohms and more preferably less than ohms.

The porous polymeric material may be expanded polytetrafluoroethylene (PTFE) having a variable pore size to allow the metal coating to penetrate the pores and to produce a coating of sufficient thickness to provide adequate electrical conductivity.

Other materials are envisaged including, but not limited to, porous silicones, porous polyurethanes, polyether block amide (PEBAX) or nylon. In each case, the pore size may be varied depending upon the method of formation of the porous material or by the addition of additives such as sodium chloride (NaC1), sodium bicarbonate (Na 2

HCO

3 or polyglycolide which can be leached out following moulding or extrusion leaving a porous structure.

Alternatively, the pores of the polymeric material may be formed by drilling into the polymer using a laser drill. This has the particular advantage of enabling only a portion of the polymer to be of a porous nature.

In one embodiment, the electrical conductor may comprise at least one straight or coiled wire embedded within the body of the electrical lead and preferably within the at least one electrically conductive region of the lead. If the electrical lead is a solid cylindrical member, the wire or wires may be coiled in a helical manner within the at least one electrically conductive region. If the electrical lead is a tubular structure, the wire or wires may be coiled in a helical manner within the wall of the tube and preferably within the at least one electrically conductive region. In either embodiment, the wire(s) may extend through several pores of the at least one electrically conductive region. Accordingly, when the porous polymeric material of the at least one region is coated with the electrically conductive material, the portions of wire which extend through the pores may be simultaneously coated with the electrically conductive material thereby creating a good electrical connection between the electrical conductor and the electrically conductive region.

The at least one wire may be one of a single wire and a multifilament wire.

Further, the at least one wire may be made of copper preferably coated with a noble metal such as palladium or platinum for corrosion resistance. Alternatively, the at least one wire may be a multifilament stainless steel wire. Other suitable materials include, but are not limited to, platinum or platinum alloy, a nickel-cobalt based alloy such as or a cobalt-chromium-nickel alloy such as Elgiloy.

In the above embodiment, depending upon the application of the electrical lead, the at least one wire may be connected by an insulated conductor to either a source of electricity or to an analyser means. Typically, the at least one wire may be connected to the insulated conductor by way of welding. Alternatively, the at least one wire may be connected by electrically conductive adhesives or by soldering.

In a further embodiment, the electrical conductor may be located internal the elongate body of the electrical lead. For example, if the electrical lead is a tube having at least one electrically conductive region, the electrical conductor may be positioned within the lumen of the tube. In this embodiment, the electrical conductor is preferably configured to engage the internal surface of the tube. To ensure that the electrical conductor engages the tube, it is preferred that the electrical conductor comprises a resilient spring, such as a spiral spring that, once positioned in the tube, can expand into contact with the inner wall of the tube.

In another embodiment, the electrical conductor may be a spring formed from a shape memory alloy such as a nickel-titanium alloy (Nitinol

TM

The shape memory spring preferably moves, when exposed to a pre-determined temperature, from a first, collapsed position to a second, expanded position in which the spring expands such that it has an outer diameter greater than the inner diameter of the tube. Accordingly, when internal the lumen of the tube and when in the expanded second position, the spring makes contact with the inner surface of the tube to a sufficient extent to provide a good electrical connection between the electrical conductor and the at least one electrically conductive region.

In one embodiment, the shape memory alloy spring expands into contact with the inner surface of the tube upon exposure to body temperature.

The shape memory spring may be connected to an insulated conductor by welding, the use of electrically conductive adhesives or soldering.

In the above embodiments, it is preferred that the electrical conductor such as the at least one wire embedded within the electrically conductive member or a shape memory alloy spring positioned within a lumen of a tubular electrically conductive member, extends the entire length of the electrically conductive member, or at least the length of the at least one electrically conductive region, such that a good electrical connection between the electrical conductor and the at least one electrically conductive region can be made.

In another embodiment, the electrical conductor is adapted to engage an end of the electrical lead. For example, the electrical conductor may include a shape memory alloy tube that is adapted to expand and increase its internal diameter upon heating above a pre-determined temperature or exposure to a particular pre-determined temperature. The shape memory alloy tube may then be slid over an end of the electrical lead. Upon heating above or cooling below the pre-determined temperature depending on the type of shape memory alloy, the shape memory alloy tube preferably returns to its original unexpanded shape therefore effectively clamping down on an end of the electrical lead. This embodiment provides a uniform radial pressure on the end of the member and provides a good electrical connection between the electrical conductor and the at least one electrically conductive region of the lead. If the electrical lead is a tube, it may be necessary to provide an inner tube which is relatively stiff and which may be positioned internal the lumen of the tube to prevent collapse of the lead.

According to a second aspect of the invention, there is provided a method of manufacturing the electrical lead of the first aspect, said method comprising: extruding an elongate body of polymeric material wherein at least one region of the elongate body is porous in nature; and (ii) coating at least a part of said elongate body with an electrically conductive material such that the electrically conductive material substantially coats the pores of said at least one region.

While the entire length of the elongate body may be coated with the electrically conductive material, in the embodiment wherein there are distinct regions of porous polymeric material, it may be preferred that only the distinct porous regions are coated with said electrically conductive material rather than the entire length of the elongate body which may include non-porous regions.

Where the electrical conductor comprises at least one straight or coiled wire, the electrical lead may be manufactured in a number of stages. For example, a first tube, or layer, or solid cylindrical member may be formed from either a porous polymeric material or non-porous polymeric material or a combination thereof. The at least one wire may then be wrapped around and along at least a portion of the first tube or solid cylindrical member in a helical manner or extended along at least a portion of the length of the first tube or layer or solid cylindrical member. The at least one wire and the first tube or layer or solid cylindrical member may then be overlaid with a coating or another layer. The coating or the other layer may be a porous polymeric material or, alternatively, a polymeric material having regions which are of a porous nature. In one embodiment, the coating may be a second tube.

In a further embodiment of the second aspect, the electrical lead may comprise a tube. In this embodiment, the electrical conductor is positioned within the lumen of the tube. The electrical conductor is preferably positioned such that it engages the internal surface of the tube. To ensure that the electrical conductor engages the tube, it is preferred that the electrical conductor comprises a resilient spring, such as a spiral spring that, once positioned in the tube, can expand into contact with the inner wall of the tube.

In another embodiment of the second aspect, the electrical conductor can be formed in a spring form from a shape memory alloy such as NitinolTM. The shape memory spring can preferably move from a first, collapsed position to a second, expanded position in which the spring expands such that it has an outer diameter greater than the inner diameter of the tube.

The electrical conductor may be adapted to engage an end of the electrical lead.

For example, the electrical conductor may include a shape memory alloy tube that is adapted to expand and increase its internal diameter upon heating above a predetermined temperature. The shape memory alloy tube may then be slid over an end of the electrical lead. Upon heating above or cooling below the pre-determined temperature depending on the type of shape memory alloy, the shape memory alloy tube preferably returns to its original unexpanded shape therefore effectively clamping down on an end of the electrical lead. This embodiment provides a uniform radial pressure on the end of the electrical lead and provides a good electrical connection between the electrical conductor and the at least one electrically conductive region of the lead.

Typically, method may include applying the electrically conductive material to the elongate body or preferably to the at least one electrically conductive region using a wet technique such as electroless plating. In this embodiment, the the method may include forcing the electrically conductive material through the pores of the at least one electrically conductive region by the application of pressure.

Alternatively, the method may include applying the electrically conductive material by electroless plating followed by the additional step of electroplating.

Each of the above processes preferably ensures that a coating of electrically conductive material penetrates substantially all the pores of the region. If the at least one region of electrically conductive material has pores disposed substantially throughout the entire thickness of said region, it is envisaged that electrical connection may be made by way of an electrical conductor, as described above, either within the wall of the elongate body or on the inside of the elongate body (for example if the elongate body is a tubular structure).

The process of coating the elongate body with an electrically conductive material such that the pores of the at least one electrically conductive region are coated with such a material may involve a number of steps prior to the actual coating with the electrically conductive material. The steps may include: Cleaning.

Surface Modification.

Catalysis.

Coating.

The material to be coated may typically be washed in an organic solvent such as acetone or ethyl acetate or in a solution containing a suitable surface active agent.

Usually some agitation is required such as from an ultrasonic cleaner or a shaker water bath. The step of cleaning may be carried out above room temperature.

The step of surface modification results in a more wettable or hydrophilic surface such that the deposition of the coating may be accelerated and, further, chemical and mechanical adhesion of the coating to the surface may be improved.

Chemical adhesion may be improved by creating the most suitable functional groups on the surface of the polymer such as amides, while mechanical adhesion may be improved by creating a roughened surface using chemical (etching) or mechanical (sandblasting) methods.

Typically, the surface modification chemicals may be infused into the pores using pressure via a pump or syringe. Alternatively, the porous material to be coated may be placed in the treatment solution and evacuated in a vacuum thereby removing gas bubbles from within the porous structure resulting in contact of all surfaces with the treatment solution.

Additionally, plasma treatment may be used to improve wettability and/or improve chemical or mechanical adhesion.

Following this step, the structure to be coated may be rinsed several times preferably in deionised water.

The catalyst step may result in the deposition of a small amount of noble metal on the surface of the material. This may provide the sites for deposition of the coating material, for example, platinum. While typical electroless plating uses a tin/palladium catalyst it is preferred that a process which eliminates the tin is used. For example, palladium in an acidic aqueous solution or dimethyl sulfoxide both of which can be reduced in a hydrazine solution is preferred. The latter is particularly useful as, being an organic solution, it allows improved wettability for many substrates.

In one embodiment of the catalysis of a material such as silicone, the catalyst, in the form of palladium metal powder can be mixed into a silicone dispersed in a solvent and then infused into the pores and cured prior to coating. In this embodiment, a small concentration of actual silicone may be required so as to provide a thin layer on the surface of the pores rather than fill the pores with silicone. The palladium metal may act as a catalyst and may be bound to the silicone and therefore increase the adhesion of the coating material which is subsequently applied.

Alternatively, the silicone mix may be infused with palladium prior to moulding or extrusion.

The catalyst step may be performed a number of times.

The coating process preferably uses electroless plating wherein a number of metals may be deposited using either commercially available or custom made solutions of complex metal ions together with a stabiliser and an added reducer. The solution typically allows controlled deposition of a metal over a specific period of time. If a biocompatible electrode is required, it is preferred that the metal is platinum.

A fifth step may be added to the above process if a thicker coating of metal and therefore higher conductivity is required. This may involve further electroless plating or electroplating.

In a further embodiment, following the process of coating, the pores may be infused with a liquid adhesive such as, but not limited to, a silicone dispersant to effectively seal the pores. Preferably the infusion of the adhesive is carried out from within the electrical lead when said lead is a tubular structure. This embodiment has the advantage of enabling an electrical lead to be implanted in a body for long periods of time with minimal tissue ingrowth into the lead. This facilitates easy removal of the lead if required.

The following examples describe the preparation of an electrical lead according to several embodiments of the present invention.

Example 1 A porous polyurethane tube was made using a spraying system. Firstly a wire mandrel was connected to an electrical motor using a chuck. The wire was the simultaneously coated with a mixture of polyurethane (Pellethane) dissolved in dimethylformamide polyurethane) and water. The water polymerised the polyurethane prior to deposition creating a porous layer. A copper wire was then wound onto the coated mandrel and a further layer was uniformly coated with the mixture of polyurethane dissolved in dimethylformamide and water. The spraying continued until the appropriate diameter was achieved ie. 2.2 mm (this was chosen as once assembled into a lead. a 2.2 mm lead body would comfortably pass down a 7 French introducer).

The porous component was then coated with platinum using the normal cleaning, surface modification, catalysis and coating steps previously outlined.

The resistance was then measured to be approximately 0.5 K for a 1cm length of the porous component, and approximately 1 0 from the end of the copper wire to the surface of the component.

Example 2 An expanded PTFE tube was supplied by Impra which had a pore size of microns. The tube was immersed in alcohol and placed in an ultrasonic cleaner to remove air bubbles and wet the surface.

The sample was removed from the alcohol and etched for 1 minute with FluoroEtch from Acton. A syringe was used to try and force the solution through the pores however this was unsuccessful.

The tube was then catalysed using a 2g/l solution of PdC1 2 in Dimethyl Sulfoxide for 5 minutes intermittently attempting to force the solutions through the pores. This was followed by a reduction step in 4% Hydrazine solution.

The catalysed tube was then electrolessly coated using a platinum complex solution and hydrazine.

After 1.5 hours the sample was a shiny, metallic colour on the outside.

After drying, the resistance along the surface was found to be approximately n for a lcm length, however the resistance through the thickness varied from 25

Q.

Example 3 Another expanded PTFE tube was supplied by Impra however this time the pore size was increased to 90 microns. The tube was immersed in alcohol and placed in an ultrasonic cleaner to remove air bubbles and wet the surface.

The sample was removed from the alcohol and etched for 30 seconds with FluoroEtch from Acton. A syringe was used to try and force the solution through the pores. This time the solution was able to freely pass through the structure.

The tube was then catalysed using a 2g/l solution of PdCI 2 in Dimethyl Sulfoxide for 5 minutes intermittently forcing the solutions through the pores. This was followed by a reduction step in 4% Hydrazine solution.

The catalysed tube was then electrolessly coated using a platinum complex solution and hydrazine intermittently forcing the solution through the pores After 1.5 hours the sample was a shiny, metallic colour on the outside.

After drying, the resistance along the surface was found to be approximately n for a 1cm length. The resistance through the thickness was approximately 1.5 Q. No materials were removed using a standard tape test to measure adhesion.

A 4 mm length was then cut and a 2.1 mm diameter NitinolTM spring (from Microvena, White Bear Lake Minnesota USA) was straightened and passed up the middle of the cut platinum coated tube. The structure was then placed in the oven at and the Nitinol

T

M spring went back to its original shape clamping on the inside of the platinum coated tube.

A length of 0.2 mm diameter copper wire was then welded to one end of the Nitinol spring. The resistance was found to be 1.8 Q2 from the end of the copper wire and the outside of the platinum coated expanded Teflon.

A PEBAX tube was passed over each end of the spring and then glued with epoxy forming a butt joint on each side of the platinum coated expanded Teflon component.

After curing the lead was then tested in an isolated cow heart, by immersing the heart with electrode attached into a conductive media and RF energy passed through the electrode to the heart creating lesions. The test device produced similar lesions to a commercially available ablation lead.

The same lead was tested when delivering pacing pulses and a suitable impedance resulted.

Due to flexibility and versatility the electrodes can be made different shapes, sizes, numbers and spacing. This is important when designing new leads for various applications eg ablation leads for treating atrial fibrillation.

The following examples describe the preparation of the electrode according to several embodiments of the third and fourth aspects of the present invention.

Example 4 A 1.6mm diameter cable was sourced from MicroHelix in Portland Oregon.

The cable contained 8 insulated wire coils in the wall of the tube. The insulating layer was made from a thin layer of PEBAX. Over one of the wires, a 4 mm length of insulation was removed to expose the corresponding amount of wire. A 4mm band of the cable around the exposed wire was masked. Some plateable conductive ink from Creative Materials (CMI 117-31) Tyngsboro MA was coated around the unmasked region covering the exposed conductor. The electrode with ink was then immersed in a platinum complex electroless bath and coated for 1 hour at 60 deg C using Hydrazine as the reducer resulting in a thickness of 0.5 microns. The pacing impedance of the plated electrode was then measured in a 0.18% NaC1 solution using a nickel plate as the return electrode. The pacing pulse used was 5 volts and 0.5 ms. The impedance was found to be 250 0. This value was compared to a commercially available ablation electrode which was found to be 180 K. No damage to the coated electrode resulted.

Example A 1.6mm diameter cable was sourced from MicroHelix in Portland Oregon.

The cable contained 8 insulated wire coils in the wall of the tube. The insulating layer was a thin layer of PEBAX. Over one of the wires, a 4 mm length of insulation was removed to expose the corresponding amount of wire. A 4mm band of the cable around the exposed wire was masked. Some plateable conductive ink from Creative Materials (CMI 117-31) Tyngsboro MA was coated around the unmasked region covering the exposed conductor.

The electrode ink was coated with a 3 micron layer of copper using electroless plating.

The copper coated electrode was then immersed in an acid palladium chloride solution to catalyse the surface and immersed again in platinum complex electroless bath and coated for 1 hour at 60 deg C using Hydrazine as the reducer. The pacing impedance of the plated electrode was then measured in a 0.18% NaCI solution using a nickel plate as the return electrode. The pacing pulse used was 5 volts and 0.5 mins. The impedance was found to be 120 n. This value was compared to a commercially available ablation electrode which was measure to be 180 Q. No damage to the coated electrode resulted.

Example 6 A 1.6mm diameter cable was sourced from MicroHelix in Portland Oregon.

The cable contained 8 insulated wire coils in the wall of the tube. The insulating layer was a thin layer of PEBAX. Over one of the wires, a 4 mm length of insulation was removed to expose the corresponding amount of wire. A 4mm band of the cable around the exposed wire was masked. Some plateable conductive ink from Creative Materials (CMI 117-31) Tyngsboro MA was coated around the unmasked region covering the exposed conductor. The electrode ink was coated with a 3 micro layer of copper using electroless plating. The copper coated electrode was then immersed in an acid palladium chloride solution to catalyse the surface and immersed again in platinum complex electroless bath and coated for 1 hour at 60 deg C using Hydrazine as the reducer.

The electrode was then placed on a piece of meat immersed in a 0.18% solution of NaCI and a stainless steel return electrode underneath. High frequency RF power was delivered through the electrode for 60 seconds, resulting in a lesion similar to a commercially available ablation electrode.

Example 7 A 1.6mm diameter cable was sourced from MicroHelix in Portland Oregon.

The cable contained 8 insulated wire coils in the wall of the tube. The insulating layer was a thin layer of PEBAX. Over one of the wires, a 4 mm length of insulation was removed to expose the corresponding amount of wire. A 4mm band of the cable around the exposed wire was masked. Some plateable conductive ink from Creative Materials (CMI 117-31) Tyngsboro MA was coated around the unmasked region covering the exposed conductor. The electrode ink was coated with a 3 micron layer of copper using electroless plating. The copper coated electrode was then immersed in an acid palladium chloride solution to catalyse the surface and immersed again in platinum complex electroless bath and coated for 1 hour at 60 deg C using Hydrazine as the reducer.

The coated electrode was then immersed in a 0.18% NaC1 solution using a nickel plate as the return electrode. A biphasic defibrillation pulse 130 volts in amplitude and 6ms in pulse width was delivered through the coated electrode which resulted in no damage to the electrode and an impedance of 130 Q.

Brief Description of the Drawings Preferred embodiments of the invention are now described with reference to the accompanying drawings, in which: Figures la, lb and ic are side elevational views illustrating the construction of one embodiment of an electrical lead of the present invention; Figures 2a, 2b and 2c are cross-sectional view through I-I of Figures la, lb and ic respectively; Figure 3 is a side elevational view of a cut-away portion of an embodiment of an electrical lead of the invention; Figures 4a and 4b are part cut-away, part side elevational views of a further embodiment of an electrical lead of the invention; Figures 5a and 5b are side elevational views of a further embodiment of an electrical lead of the invention; Figure 6 is a schematic view of a multi-electrode assembly incorporating electrically conductive regions of the present invention; Figure 7 is a perspective view of a number of electrically conductive regions of the present invention in an electrode assembly; Figures 8a, 8b and 8c are schematic views showing the steps of manufacture of an electrical lead according to an embodiment of a further aspect of the invention; Figures 9a, 9b and 9c are schematic views showing the steps of manufacture of an electrical lead of another embodiment of the aspect depicted in Figures 8a, 8b and 8c; and Figures 10a, 10b and 10c are schematic views showing the steps of manufacture of an electrical lead of a further embodiment of the aspect depicted in Figures 8a, 8b and 8c.

Detailed Description of the Drawings The lead 10 of the present invention includes an elongate body 11 having at least one electrically conductive region 20 thereof made from a porous polymeric material. The porous polymeric material is coated with an electrically conductive material and preferably a metal such as platinum.

As discussed above, the lead of the present invention is adapted for medical use and in particular use in cardiac mapping, defibrillation or pacing, neurological applications including neural stimulation implants, muscle stimulation, sensing and ablation.

As depicted in the drawings, the lead 10 has a tubular structure having a wall 12 and an internal lumen 13. While only one region 20 of the tube may be made from the porous polymeric material, it may be preferable that the entire length of the tube is made from said material.

The pores within the wall 12 are preferably greater than 5 microns and preferably between 30 and 100 microns.

The coating of the porous polymeric material with the metal creates a suitably thick layer of metal coating thereby increasing electrical conductivity through the lead To establish a good electrical connection the lead includes a conductive member 14.

In one embodiment, depicted in Figures la, lb, Ic, the conductive member 14 comprises a coiled wire 15 embedded within a wall 12 of the lead 10. The wire 15 is wrapped around and along a substantial length of the lead and preferably along the entire lead. While not shown, the wire 15 may pass through several pores of the polymeric material and thus when the porous polymer is coated with the metal, the portions of wire 15 within the pores may simultaneously be coated with the metal thereby creating a good electrical connection between wire and the at least one electrically conductive region As shown in Figures 1 a, lb and 1 c, the lead of this embodiment may be made in a number of stages. A first tube 16 is created as shown in figure 1 a. The tube 16 may, or may not be, porous in nature. The wire 15 is subsequently wrapped around and along the first tube 16 in a helical manner and the wire 15 and first tube 16 subsequently overlayed with a second porous polymer material 17.

In another embodiment, the conductive member 14 is a shape memory alloy spring 18 such as a Nitinol T M spring. The spring 18 of this embodiment is positioned internal the lumen 13 of the lead 10. In use, the spring 18 may be exposed to a predetermined temperature that causes it to expand such that it abuts with the internal surface 19 of the lead 10. Preferably, the spring can normally expand to such an extent that its external diameter is greater than the diameter of the lumen 13 resulting in a good electrical connection between the spring and the at least one electrically conductive region.

In another embodiment of the invention depicted in Figures 5a and 5b, the conductive member 14 is adapted to engage one end 21 of the lead 10. Preferably the conductive member is a shape memory alloy tube 22 which is adapted to expand and increase its internal diameter upon heating above or cooling below a pre-determined temperature depending on the type of shape memory alloy. The shape memory alloy tube 22 may then be slid over the end 21 of the lead 10. Upon heating up or cooling below the pre-determined temperature depending on the type of shape memory alloy, the shape memory alloy tube 22 returns to its original unexpanded shape therefore effectively clamping down on an end of the lead as shown in Figure 5b. Accordingly, there is provided a uniform radial pressure on the end 21 of the lead 10 which results in a good electrical connection between the alloy tube and the at least one electrically conductive region. In this embodiment, it may be necessary to provide an inner, relatively stiff tube (not shown) which may be positioned internal the electrode 10 to prevent collapse of the lead Once the lead 10 has been coated with the selected metal, the lead 10 may be cut to the desired length depending on the application of the electrode. For example, a defibrillation electrode formed from the lead may need to be a length of around whereas a lead acting as an electrode for mapping or sensing need only be a few millimetres in length.

A multi-electrode system along a lead may be constructed by threading together lengths of coated 23 or uncoated 24 tubes of specified lengths as depicted in Figure 6.

The coated 23 and uncoated 24 tubes are joined together using butt joints which may have spring or tubing supports (not shown) within the lumen of the tubes 23 or 24.

In the aspect of the invention depicted in Figures 8a, 8b and 8c, the invention consists in an electrically conductive member 30 including an elongate body 31. The elongate body 31 has at least one electrically conductive region 32 which comprises a polymeric material together 33 together with at least one electrical conductor 34. A portion of the polymeric material 33 and a potion or all of the electrical conductor 34 are coated with an electrically conductive material The elongate body comprises a first cylindrical inner member 36 and a second outer member 37 said second outer member substantially forming a coating around the first inner member 36. The second outer member 37 extends substantially over the entire length of the first inner member 36. The at least one electrical conductor 34 is sandwiched between the first inner member 36 and the second outer member 37.

As shown in Figure 8b, the electrical conductor 34 is exposed. This may be achieved by a number of means including the application of heat, chemicals or lasers to remove the area of the outer member 37 covering the electrical conductor 34.

The exposed electrical conductor 34 and an area of the polymeric material 33 adjacent the electrical conductor 34 is then catalysed and coated with the electrically conductive material 35 to form an electrode 38.

As depicted in Figures 9a, 9b and 9c, two electrodes 38 may be formed by coating separate electrical conductors 34 together with an adjacent area of polymeric material 33.

For high energy applications such as RF or microwave ablation, Figures and 10c show how a number of electrical conductors 34 together with their adjacent polymeric material 33 may be coated with an electrically conductive material to form a single electrode 38. The electrical conductors of this embodiment may be electrically connected to each other at a proximal end of each electrical conductor. The number of electrodes formed together with the spacing between each electrode may be varied.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (31)

1. An electrical lead comprising an elongate body, the body having at least one electrically conductive region, the region being defined by a porous polymeric material, having a plurality of pores therein, coated with an electrically conductive material, wherein the pores extend transversely to a longitudinal axis of the elongate body and extend at least partly through a wall of the elongate body; and at least one electrical conductor embedded in the elongate body and extending into the at least one electrically conductive region so that the at least one conductor is in communication with a number of the pores of the at least one electrically conductive region.

2. The electrical lead of claim I comprising a plurality of spaced, electrically conductive regions.

3. The electrical lead of claim 1 or claim 2 wherein said elongate body is tubular.

4. The electrical lead of claim 3 wherein the pores of the at least one electrically conductive region extend at least partially through a wall of the tubular elongate body.

The electrical lead of claim 1 or claim 2 wherein said elongate body comprises a solid cylindrical member.

6. The electrical lead of claim 5 wherein the pores of the at least one electrically conductive region extend transversely at least partially through the solid cylindrical member.

7. The electrical lead of claim 4 or claim 6 wherein the pores of the polymeric material have a diameter greater than about 5 microns.

8. The electrical lead of claim 7 wherein the pores of the polymeric material have a diameter of between about 30 and about 100 microns.

9. The electrical lead of any one of the preceding claims wherein the electrically conductive material comprises at least one biocompatible metal.

The electrical lead of claim 9 wherein the metal is a combination of at least two metals or metal alloys.

11. The electrical lead of any one of the preceding claims wherein the porous polymeric material is expanded polytetrafluoroethylene (PTFE) having a variable pore size.

12. The electrical lead of any one of claims 1 to 11 wherein the porous polymeric material is selected from the group consisting of porous silicones, porous polyurethanes, polyether block amide (PEBAX) and nylon.

13. The electrical lead of any one of the preceding claims wherein the pores of the polymeric material are formed by the addition of additives to the polymeric material, the additives being selected from the group consisting of sodium chloride (NaC1), sodium bicarbonate (Na 2 HCO 3 and polyglycolide.

14. The electrical lead of any one of claims 1 to 11 wherein the pores of the polymeric material are formed by laser drilling the polymeric material.

The electrical lead of any one of the preceding claims wherein said portion of the electrical conductor which extends through the pores is coated with the electrically conductive material.

16. The electrical lead of any one of the preceding claims wherein the at least one electrical conductor comprises at least one straight or coiled wire.

17. The electrical lead of claim 16 wherein the at least one wire is one of a single wire and a multifilament wire.

18. The electrical lead of claim 16 or claim 17 wherein the at least one wire is made of copper coated with a noble metal.

19. The electrical lead of claim 16 or claim 17 wherein the at least one wire is made from a material selected from the group consisting of stainless steel, platinum or platinum alloy, a nickel-cobalt based alloy, a cobalt-chromium-nickel alloy, copper and silver either alone or coated with another metal.

20. The electrical lead of claim 16 or claim 17 wherein the electrical conductor is a spring wire formed from a shape memory alloy.

21. The electrical lead of claim 20 wherein the shape memory alloy is a nickel- titanium alloy.

22. A method of manufacturing the electrical lead of claim 1, the method comprising: extruding an elongate body of polymeric material wherein at least one region of the elongate body is porous in nature; and (ii) coating at least a part of said elongate body with an electrically conductive material such that the electrically conductive material substantially coats the pores of said at least one region.

23. The method of claim 22 which includes applying the electrically conductive material to the elongate body by electroless plating.

24. The method of claim 23 which includes forcing the electrically conductive material through the pores of the at least one electrically conductive region by the application of pressure.

The method of claim 23 or claim 24 comprising a further step of at least one of Selectroplating and further electroless plating.

26. The method of any one of claims 22 to 25 which includes, prior to step (ii), Scleaning an outer surface of the elongate body.

27. The method of any one of claims 22 to 26 which includes, prior to step (ii), modifying an outer surface of the elongate body to produce a wettable or hydrophilic r i surface such that the deposition of the coating is accelerated and chemical and mechanical adhesion of the coating to the surface is improved. C1

28. The method of any one of claims 22 to 27 which includes, prior to step (ii), 010 catalysing a surface of the elongate body.

29. The method of claim 28 which includes catalysing a surface of only the at least one electrically conductive region.

An electrical lead as claimed in claim 1 and substantially as described herein with reference to the accompanying drawings.

31. A method of manufacturing an electrical lead as claimed in claim 1 and substantially as described herein with reference to the accompanying drawings. DATED this twenty-fourth day of March 2006 CathRx Pty Ltd Patent Attorneys for the Applicant: F.B. RICE CO.