Electrode assemblies for shockwave generating catheters

Abstract

Disclosed herein is an electrode assembly for a shockwave-generating catheter, said electrode assembly comprising at least one electrically non-conductive layer, a first electrode and a second electrode, the first and second electrodes being physically separated from each other and connectable to a voltage power source, the electrode assembly having a tubular configuration with an outer surface and an inner surface, the inner surface forming a lumen, the outer surface of the electrode assembly formed from an outermost electrically non- conductive layer of the at least one electrically non-conductive layer, the outermost electrically non-conductive layer being disposed over the first electrode and the second electrode, a first hole extending through the at least one electrically non-conductive layer to expose a portion of the first electrode to a surrounding environment, a second hole extending through the at least one electrically non-conductive layer to expose a portion of the second electrode to a surrounding environment, where the first and second holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when a potential difference is applied across the first and second electrodes by the voltage power source. Also provided herein is a shockwave-generating unit comprising the electrode assembly, a shockwave-generating system comprising one or more shockwave generating units, and a shockwave generating catheter comprising a shockwave generating system.

Description

[0001] ELECTRODE ASSEMBLIES FOR SHOCKWAVE GENERATING CATHETERS

[0002] Field of Invention

[0003] The present invention relates to an electrode assembly for shockwave-generating catheters. The present invention also relates to shockwave-generating units, shockwave-generating systems and shockwave-generating catheters comprising one or more of the electrode assemblies.

[0004] Background

[0005] The listing or discussion of a prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

[0006] A balloon angioplasty catheter is an interventional device used to expand blood vessels and soften calcified lesions in order to restore the normal flow of blood. Numerous enhancements to the traditional device have been made over time, one of which is the addition of shockwave generating electrode assemblies within the balloon that aid in the softening or cracking of calcification in the intimal vessel wall. The shockwave generators produce high-powered shockwaves that impinge upon the hard and brittle calcium while the balloon applies physical pressure. The combined effects of both the shockwaves and balloon pressure have been proven to more effectively restore patency of the vessel for a longer period of time. However, a limitation of current devices is the power of the shockwaves produced and the longevity of the generators producing them.

[0007] Therefore, there exists a need for alternative and / or improved electrode assemblies for shockwave-generating systems and catheters.

[0008] Summary of Invention

[0009] Aspects and embodiments of the invention are described in the following numbered clauses.

[0010] 1. An electrode assembly for a shockwave-generating catheter, said electrode assembly comprising: at least one electrically non-conductive layer, a first electrode and a second electrode, the first and second electrodes being physically separated from each other and connectable to a voltage power source; the electrode assembly having a tubular configuration with an outer surface and an inner surface, the inner surface forming a lumen, the outer surface of the electrode assembly formed from an outermost electrically non- conductive layer of the at least one electrically non-conductive layer, the outermost electrically non-conductive layer being disposed over the first electrode and the second electrode; a first hole extending through the at least one electrically non-conductive layer to expose a portion of the first electrode to a surrounding environment; a second hole extending through the at least one electrically non-conductive layer to expose a portion of the second electrode to a surrounding environment, wherein the first and second holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when a potential difference is applied across the first and second electrodes by the voltage power source.

[0011] 2. The electrode assembly of clause 1 , wherein the inner surface of the electrode assembly is formed from an innermost electrically non-conductive layer.

[0012] 3. The electrode assembly of clause 2, wherein the electrode assembly further comprises one or more internal electrically non-conductive layers each disposed between the innermost layer and the outermost electrically non-conductive layers.

[0013] 4. The electrode assembly of clause 3, wherein the electrode assembly further comprises at least two internal electrically non-conductive layers, for example, two, three, four, five or six internal electrically non-conductive layers.

[0014] 5. The electrode assembly of any one of clauses 3 to 4, wherein the first and second electrodes are each independently embedded within the innermost electrically non-conductive layer or one of the internal electrically non-conductive layers.

[0015] 6. The electrode assembly of any one of clause 2 to 5, wherein the first and second electrodes are each embedded within different electrically non-conductive layers.

[0016] 7. The electrode assembly of any one of clauses 2 to 6, wherein the first electrode is embedded within the innermost electrically non-conductive layer.

[0017] 8. The electrode assembly of any one of clauses 2 to 6, wherein the first and second electrodes are each independently embedded within one of the internal electrically non- conductive layers. 9. The electrode assembly of any one of clauses 3 to 8, wherein each of the one or more internal electrically non-conductive layers are formed from a polymer independently selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), an epoxy resin, and a combination of two or more thereof.

[0018] 10. The electrode assembly of any one of clauses 3 to 9, wherein the electrode assembly comprises:

[0019] - a first internal electrically non-conductive layer disposed over the innermost electrically non-conductive layer;

[0020] - a second internal electrically non-conductive layer disposed over the first internal electrically non-conductive layer;

[0021] - a third internal electrically non-conductive layer disposed over the second internal electrically non-conductive layer; and the outermost electrically non-conductive layer disposed over the third internal electrically non-conductive layer thereby forming the outer surface of the electrode assembly.

[0022] 11 . The electrode assembly of clause 10, wherein

[0023] - the first internal electrically non-conductive layer is formed from a polyimide;

[0024] - the second internal electrically non-conductive layer is formed from an epoxy resin;

[0025] - the third internal electrically non-conductive layer is formed from a polyimide.

[0026] 12. The electrode assembly of clause 11 , wherein the first electrode is embedded within the innermost electrically non-conductive layer and the second electrode is embedded within the second internal electrically non-conductive layer.

[0027] 13. The electrode assembly of any one of clauses 2 to 11 , wherein the innermost electrically non-conductive layer is formed from an epoxy resin.

[0028] 14. The electrode assembly of any one of clauses 2 to 12, wherein the outermost electrically non-conductive layer is formed from an impact resistant and / or shock absorbing material, for example the outermost electrically non-conductive layer is formed from an epoxy resin that is impact resistant and / or shock absorbing. 15. The electrode assembly of any one of clauses 2 to 14, wherein the first electrode and the second electrode are offset with respect to each other along the longitudinal axis of the electrode assembly.

[0029] 16 The electrode assembly of clause 1 , wherein the inner surface of the electrode assembly is formed from an innermost layer comprising the first and second electrodes and an electrically non-conductive member, wherein the electrically non-conductive member physically separates the first and second electrodes from each other.

[0030] 17. The electrode assembly of clause 16, wherein the electrode assembly further comprises one or more internal electrically non-conductive layers each disposed between the innermost layer and the outermost electrically non-conductive layer.

[0031] 18. The electrode assembly of clause 16 or 17, wherein the electrically non-conductive member is formed from one or more of the group consisting of a polymer, a ceramic, an epoxy, an adhesive and a combination thereof, optionally wherein the polymer is selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), and a combination thereof, for example, wherein the polymer comprises a polyimide.

[0032] 19. The electrode assembly of any one of clauses 16 to 18, wherein the electrically non- conductive member has a maximum radius that corresponds to the maximum radius of the first and second electrodes.

[0033] 20. The electrode assembly of any one of clauses 16 to 18, wherein the electrically non- conductive member has a maximum radius that is greater than the maximum radius of each of the first and second electrodes.

[0034] 21 . The electrode assembly of clause 1 , wherein the inner surface of the electrode assembly is formed from the first electrode and a first portion of an innermost electrically non-conductive layer; a second portion of the innermost electrically non-conductive layer disposed between the first electrode and the outermost electrically non-conductive layer; the second electrode disposed between the first portion of the innermost electrically non-conductive layer and the outermost electrically non-conductive layer. 22. The electrode assembly of clause 21, wherein the innermost electrically non- conductive layer is formed from a nylon, a poly(ether-b-amide) (e.g. Pebax®), or a heat- shrinkable tubing (e.g. fluorinated ethylene propylene or polyethylene terephthalate); and the outermost electrically non-conductive layer is formed from an impact resistant and / or shock absorbing material, for example the outermost electrically non-conductive layer is formed from an epoxy resin that is impact resistant and / or shock absorbing.

[0035] 23. The electrode assembly of any one of the preceding clauses, wherein the first and / or second electrodes are formed from one or more of the group consisting of tungsten, steel, titanium, cobalt, platinum, iridium, nickel, and an alloy thereof.

[0036] 24. The electrode assembly of any one of the preceding clauses, wherein the first and second holes are offset with respect to each other along the longitudinal axis of the electrode assembly.

[0037] 25. The electrode assembly of any one of clauses 1 to 23, wherein the first and second holes are offset with respect to each other around the circumference of the electrode assembly.

[0038] 26. The electrode assembly of any one of the preceding clauses, wherein the first and second holes have substantially the same diameter.

[0039] 27. The electrode assembly of any one of clauses 1 to 25, wherein the first and second holes have a different diameter from each other.

[0040] 28. The electrode assembly of any one of the preceding clauses, wherein the portion of the first and / or second electrode that is exposed to a surrounding environment comprises a surface shape that is configured to concentrate the location of electrical arc discharge.

[0041] 29. The electrode assembly of clause 28, wherein the surface shape that is configured to concentrate the location of electrical arc discharge comprises a surface indent.

[0042] 30. The electrode assembly of clause 28, wherein the surface indent has a shape selected from the group consisting of hemispherical concave, conical, and cylindrical deboss (e.g. a cylindrical deboss).

[0043] 31 . The electrode assembly of clause 28, wherein the surface shape that is configured to concentrate the location of electrical arc discharge comprises a surface protrusion, optionally wherein the surface protrusion has a conical or hemispherical shape.

[0044] 32. The electrode assembly of any one of the preceding clauses, wherein the first and second holes each have a diameter of from about 0.2 mm to about 1 mm.

[0045] 33. The electrode assembly of any one of the preceding clauses, wherein a minimum distance from an edge of the first hole to an edge of the second hole is from about 0.05 mm to about 10 mm.

[0046] 34. The electrode assembly of any one of the preceding clauses, wherein at least one of the electrically non-conductive layers has a thickness of from about 0.02 mm to about 0.8 mm, optionally wherein each of the electrically non-conductive layers has a thickness of from about 0.02 mm to about 0.8 mm.

[0047] 35. The electrode assembly of any one of the preceding clauses, further comprising: a third hole extending through the at least one electrically non-conductive layer to expose a portion of the first electrode to a surrounding environment; a fourth hole extending through the at least one electrically non-conductive layer to expose a portion of the second electrode to a surrounding environment, wherein the third and fourth holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when the first and second electrodes are connected to a high voltage power source.

[0048] 36. A shockwave-generating unit comprising an electrode assembly of any one of the preceding clauses and an axially extending elongate member that extends through the lumen of the electrode assembly, optionally wherein the axially extending elongate member comprises an outer surface comprising a polyimide.

[0049] 37. A shockwave-generating system for a shockwave-generating catheter comprising: one or more shockwave-generating unit of clause 36; a high voltage power source having an electrical output terminal electrically connected to the first and second electrodes of the one or more shockwave-generating units, optionally wherein the high voltage power source has a voltage of from 1000 V to 5000 V.

[0050] 38. The shockwave-generating system according to clause 37, wherein the electrical output terminal of the high voltage power source is connected to the first and second electrodes of the one or more shockwave-generating units by a wire that extends from the terminal along the outer surface of, or through an interior of, the axially extending elongate member.

[0051] 39. The shockwave-generating system according to clause 37 or 38, further comprising an integrated electronic printed circuit board configured to determine the output voltage of the high voltage power source.

[0052] 40. A shockwave-generating catheter comprising: a shockwave-generating system of one of clauses 37 to 39; and an inflatable balloon disposed over the axially extending elongate member and each of the one or more shockwave-generating units.

[0053] Drawings

[0054] FIG. 1A is a partial sectional view of a shockwave-generating unit of the present disclosure with two electrically non-conductive layers.

[0055] FIG. 1 B is a partial sectional view of a shockwave-generating unit of the present disclosure with three electrically non-conductive layers.

[0056] FIG. 2A is a partial sectional view of a shockwave-generating unit of the present disclosure with a single electrically non-conductive layer.

[0057] FIG. 2B is a partial sectional view of a shockwave-generating unit of the present disclosure with a single electrically non-conductive layer of a thinner thickness than that of the embodiment illustrated in FIG. 2A.

[0058] FIG. 3 is a partial sectional view of a shockwave-generating unit of the present disclosure with an electrically non-conductive member of greater diameter than the first and second electrodes.

[0059] FIG. 4 is a perspective view of a shockwave-generating unit of the present disclosure with the first and second holes offset with respect to each other around the circumference of the electrode assembly.

[0060] FIG. 5 is a perspective view of a shockwave-generating unit of the present disclosure with the first and second holes having a different diameter from each other. FIG. 6 is a partial sectional view of a shockwave-generating unit of the present disclosure with third and fourth holes extending through the single electrically non-conductive layer.

[0061] FIG. 7A is a partial sectional view of a shockwave-generating unit of the present disclosure with a hemispherical concave surface indent.

[0062] FIG. 7B is a magnified view of the hemispherical concave surface indent of the shockwavegenerating unit illustrated in FIG 7A.

[0063] FIG. 8 is a partial sectional view of a shockwave-generating unit of the present disclosure with a conical surface indent.

[0064] FIG. 9 is a partial sectional view of a shockwave-generating unit of the present disclosure with a cylindrical deboss surface indent.

[0065] FIG. 10A is a partial sectional view of a shockwave-generating unit of the present disclosure with a hemispherical surface protrusion.

[0066] FIG. 10B is a partial sectional view of a shockwave-generating unit of the present disclosure with a conical surface protrusion.

[0067] FIG. 11 is a partial sectional view of a shockwave-generating unit of the present disclosure wherein the inner surface of the electrode assembly is formed by a first electrode and a first portion of an innermost electrically non-conductive layer. A second electrode is disposed between the first portion of the innermost electrically non-conductive layer and an outermost electrically non-conductive layer.

[0068] FIG. 12A is a perspective view of a shockwave-generating unit of the present disclosure wherein the first electrode is disposed within the innermost electrically non-conductive layer with a first, second and third internal electrically non-conductive layers and an outermost electrically non-conductive layer each disposed over innermost electrically non-conductive layer. The second electrode is disposed within the second internal electrically non-conductive layer.

[0069] FIG. 12B is a sectional view of the shockwave-generating unit illustrated in FIG 12A. FIG. 12C is a cross-sectional view of the shockwave-generating unit illustrated in FIG 12A.

[0070] Description

[0071] In embodiments herein, the word “comprising” may be interpreted as requiring the features mentioned, but not limiting the presence of other features. Alternatively, the word “comprising” may also relate to the situation where only the components / features listed are intended to be present (e.g. the word “comprising” may be replaced by the phrases “consists of’ or “consists essentially of”). It is explicitly contemplated that both the broader and narrower interpretations can be applied to all aspects and embodiments of the present invention. In other words, the word “comprising” and synonyms thereof may be replaced by the phrase “consisting of’ or the phrase “consists essentially of’ or synonyms thereof and vice versa.

[0072] The phrase, “consists essentially of” and its pseudonyms may be interpreted herein to refer to a material where minor impurities may be present. For example, the material may be greater than or equal to 90% pure, such as greater than 95% pure, such as greater than 97% pure, such as greater than 99% pure, such as greater than 99.9% pure, such as greater than 99.99% pure, such as greater than 99.999% pure, such as 100% pure.

[0073] Provided herein is an electrode assembly for a shockwave-generating catheter, said electrode assembly comprising: at least one electrically non-conductive layer, a first electrode and a second electrode, the first and second electrodes being physically separated from each other and connectable to a voltage power source (e.g. a high voltage power source); the electrode assembly having a tubular configuration with an outer surface and an inner surface, the inner surface forming a lumen, the outer surface of the electrode assembly formed from an outermost electrically non- conductive layer of the at least one electrically non-conductive layer, the outermost electrically non-conductive layer being disposed over the first electrode and the second electrode; a first hole extending through the at least one electrically non-conductive layer to expose a portion of the first electrode to a surrounding environment; a second hole extending through the at least one electrically non-conductive layer to expose a portion of the second electrode to a surrounding environment, wherein the first and second holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when a potential difference is applied across the first and second electrodes by the voltage power source. In certain embodiments, the electrode assembly comprises an axially extending elongate member that extends through the lumen. Typically, the axially extending elongate member comprises an outer surface comprising a polyimide.

[0074] The phrase “tubular configuration” as used herein encompasses any configuration having the form of a tube. It may include, but is not limited to, tubular configurations having a substantially circular cross-section, an oval cross-section, a regular polygonal cross-section with substantially equal sides (e.g., a square cross-section, a pentagonal cross-section) or an irregular polygonal cross-section with unequal sides. In certain embodiments, the electrode assembly has a tubular configuration that has a substantially circular cross-section.

[0075] The electrode assembly of the present invention is described below with references to the enclosed figures. An electrode assembly of the present invention which comprises an axially extending elongate member extending through the lumen of the electrode assembly may be referred to herein as a shockwave generating unit. The electrode assemblies of the present invention are described below in the context of a shockwave-generating unit.

[0076] FIG. 1A illustrates a shockwave-generating unit 100 of the present disclosure suitable for generating shockwaves. The shockwave-generating unit comprises an electrode assembly of the present invention with an axially extending elongate member 101 that extends through the lumen of the electrode assembly. The axially extending elongate member 101 has disposed on its outer surface a first electrode 102 and a second electrode 103. The electrodes are connectable to a high voltage power source. The electrodes are electrically-conductive and may be constructed of electrically-conductive materials such as, but not limited to, tungsten, steel, titanium, cobalt, platinum, iridium, nickel, or any of their alloys. Separating (e.g. disposed between) the first and second electrodes is an electrically non-conductive member 104 that physically and electrically separates the two electrodes. The electrically non-conductive member 104 may be constructed of electrically-insulating (i.e. electrically non-conductive) materials such as, but not limited to, thermoplastic elastomers, ceramics or fluoropolymers. The first electrode 102, second electrode 103, and electrically non-conductive member 104 may have similar inner and outer diameters that allow them to conform concentrically to the axially extending elongate member 101 , as well as sit radially flush to each other with respect to their outer surfaces. The consistency in inner and outer diameters may allow the two electrodes to be completely electrically isolated from each other. Cylindrically disposed over the first electrode 102, second electrode 103 and electrically non-conductive member 104, is a first (an internal) electrically non-conductive layer 105. Cylindrically disposed over the first (the internal) electrically non-conductive layer 105 is a second (an outermost) electrically non- conductive layer 106. The first and second electrically non-conductive layers 105 and 106 may be constructed of electrically non-conductive materials such as, but not limited to, polymers such as polyimides or fluoropolymers, or adhesives. The first electrode 102, second electrode

[0077] 103, electrically non-conductive member 104, first (internal) electrically non-conductive layer 105, and second (outermost) electrically non-conductive layers together form the electrode assembly having a tubular configuration with an outer surface and an inner surface, the inner surface forming a lumen through which the axially extending elongate member 101 extends. The inner surface of the electrode assembly is formed by the first and second electrodes 102, 103 and the electrically non-conductive member 104, wherein the electrically non-conductive member physically separates the first and second electrodes from each other.

[0078] In one variation of the shockwave generating unit 100, the first (the internal) electrically non- conductive layer 105 may preferably be constructed of a polyimide sheath for electrical insulation, and the second (the outermost) electrically non-conductive layer 106 may preferably be constructed of fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE) for high temperature resistance.

[0079] In a second variation of the shockwave-generating unit 100, the first (the internal) electrically non-conductive layer 105 may preferably be composed of a suitable cured adhesive for binding the first and second electrodes 102 and 103 and electrically non-conductive member

[0080] 104, as well as the second (the outermost) electrically non-conductive layer 106, which may preferably be constructed of a polyimide sheath for optimum electrical insulation.

[0081] In another variation of the shockwave-generating unit 100, the first (the internal) electrically non-conductive layer 105 may preferably be constructed of a suitable cured adhesive for binding the first and second electrodes 102 and 103 and electrically non-conductive member 104, as well as the second (the outermost) electrically non-conductive layer 106, which may preferably be constructed of an FEP or PTFE heat-shrinkable tubing for further securement of the shockwave-generating unit 100.

[0082] The variation in materials used and combinations thereof may allow the overall device to adopt different mechanical properties to suit different operations. For example, for a durable shockwave-generating unit, having an adhesive as the first (the internal) electrically non- conductive layer and a heat-shrunk tube as the second (the outermost) electrically non- conductive layer may confer a higher level of wear resistance against shockwaves. In another variation of the shockwave-generating unit, as shown in FIG. 1 B, there may exist a third (a second internal) electrically non-conductive layer 107 disposed between the first (the first internal) electrically non-conductive layer 105 and the second (the outermost) electrically non-conductive layer 106. Multiple layers of electrically non-conductive layers of different materials may confer a higher insulating strength as well as protect against impact damage from the shockwaves produced. In order for an electrical arc to be produced between the two electrodes 102 and 103, there may exist a point of conduction on each electrode. A first hole 108 and second hole 109 extending through the insulating layers (i.e. the electrically non- conductive layers) expose small portions 111 and 112 of each electrode 102 and 103 respectively to the surrounding environment. These exposed areas form areas of conduction that allow an electrical arc to form in the conductive fluid between the exposed areas of the two conducting electrodes when a voltage pulse is sent through a circuit comprising the electrodes and a high voltage source located outside of the device. The electrical arc produced in turn causes the formation of cavitation bubbles within a conductive fluid that rapidly expand and collapse, causing powerful shockwaves to be created.

[0083] The strength of the shockwaves may be modified by adjusting the depth of the holes in the electrically non-conductive layer or layers of the electrode assembly. A deep hole facilitates the focusing of shockwaves originating from within the channel created by the hole. This focusing effect gathers and enhances shockwave strength through constructive interference, thus ensuring that less of the non-incident energy is wasted. The depth of the holes may be tuned by adjusting the thickness of the electrically non-conductive layer or layers. For example, in FIG. 2A, the holes 201 and 202 have a depth determined by the electrically non-conductive layer 203. The depth may confer a set level of reflecting ability for shockwaves generated within it. FIG. 2B, on the other hand, shows the holes 204 and 205 having a depth determined by the electrically non-conductive layer 206, which is shallower than that shown in FIG. 2A. This depth may confer a theoretically lower level of reflecting ability for shockwaves generated within it, as less of the shockwaves are focused in one direction and are allowed to scatter in a diffused manner immediately upon exiting the cylindrical hole. The depth of the holes may thus be tuned in this manner in order to produce an optimum level of reflecting ability.

[0084] In FIG. 2A and 2B, the shockwave-generating units are shown as comprising an electrode assembly that comprise a single electrically non-conductive layer 203, 206. As such, the electrically non-conductive layers 203, 206 are each considered the outermost electrically non-conductive layer of the electrode assemblies shown in these figures. While the depth of the holes may be directly tuned by varying the thickness of the electrically non-conductive layers, it may also be tuned by varying the number of electrically non- conductive layers present. Referring back to FIG. 1A and FIG. 1 B, a plurality of electrically non-conductive layers may be used as permitted by size limitations of the catheter. This may have the same effect as varying the thickness of each layer, but an advantage of using multiple layers may be the ability to use multiple types of materials in the construction of the shockwave-generating unit. As previously mentioned, one layer may be an adhesive used to improve the bond strength of all components within the unit, while another layer may be a fluoropolymer that provides electrical insulation and resistance to shockwave damage.

[0085] Typically, each electrically non-conducting layer of the electrode assembly disclosed herein has a thickness of from about 0.02 mm to about 0.8 mm. For example, each electrically nonconducting layer may have a thickness of from at least about 0.2 mm, such as from about 0.2 mm to about 0.4 mm. The combined thickness of all the electrically non-conducting layers of a shockwave-generating unit is typically from about at least 0.4 mm, for example from about 0.4 to about 1 mm, for example from about 0.4 mm to about 0.8 mm.

[0086] The depths of the holes may also be tuned by varying the outer diameters of the electrodes. For example, FIG. 3 shows a shockwave-generating unit 300 where the first electrode 301 and second electrode 302 have a smaller outer diameter than the outer diameter of the electrically non-conductive member 304. This allows the conducting surface of each electrode to sit lower within the device. Such a case may be useful when there is a limit to the overall outer diameter of the catheter. It should also be noted that the outer diameters of either electrode need not be the same as the other. This may then allow for different hole depths and may be useful from a durability standpoint, where the catheter design only allows for a permanently positive and a permanently negative electrode. For example, it is theorized that the region around the positive electrode tends to be where spark point of the plasma arc occurs. Thus, the electrodes may be configured in such a way that the positive electrode has a smaller outer diameter resulting in a deeper hole. With a deeper hole, there is more material for the spark to burn through, thus allowing the insulating layers around the positive electrode to last longer throughout the operation.

[0087] Another feature that can be adjusted to modify the strength of the shockwaves produced by the shockwave-generating unit of the present disclosure is the distance between each of the holes on the shockwave-generating unit. The location of the holes determines the spacing between each hole, and therefore the spark gap of the electrodes. This spark gap is the distance through the conductive fluid which an electrical arc must travel through in order to electrically bridge the conducting electrodes. A larger distance between each hole presents a path of higher resistance to the electrical arc, and consequently, a lower powered shockwave. Referring back to FIG. 1 , the two holes 108 and 109 are arranged to be aligned with each other on the circumference of the electrode assembly, but are offset with respect to each other along the longitudinal axis of the electrode assembly. This is the most basic arrangement of the holes. The distance between the holes may be varied by positioning them further apart from each other along the longitudinal axis of the electrode assembly. However, this may not be the most practical way to achieve a larger spark gap between the conducting electrodes due to space constraints on the catheter. Thus, alternatively, the holes may be arranged to be offset from each other around the circumference of the electrode assembly and offset with respect to each other along the longitudinal axis of the electrode assembly. FIG. 4 shows one such example of a pair of holes 401 and 402 that are offset from each other around the circumference of the electrode assembly and offset with respect to each other along the longitudinal axis of the electrode assembly. The distance between the two holes along the longitudinal axis of the electrode assembly remains the same as that shown in FIG. 1 , but the actual displacement from each other is increased by the holes being offset from each other along the circumference of the electrode assembly.

[0088] Typically, the distance from an edge of the first hole to a corresponding edge of the second hole of the electrode assembly disclosed herein from about 0.05 mm to about 10 mm, for example from about 1 mm to about 5 mm (e.g. from about 1.5 mm to about 3.5 mm such as from about 2 mm to about 3 mm).

[0089] Another feature that can be adjusted to modify the strength of the shockwaves produced by the shockwave-generating unit of the present disclosure is the size of the holes which may be altered in order to change the characteristics of the electrical arc and resulting shockwaves produced. FIG. 5 shows holes 501 and 502, where hole 502 has a greater diameter than 501 . Varying the size of the holes allows a change in the amount of surface area of electrode exposed. This may then alter the charge concentration of the current at the positive electrode before the electrical arc is formed, thereby affecting the strength of the shockwave produced.

[0090] Typically, the first and second holes of the electrode assembly disclosed herein may each have a diameter of from about 0.2 mm to about 1 mm (e g. about 0.5 mm).

[0091] The number of holes present in the shockwave-generating unit of the present disclosure may also be varied in order to affect the number of zones at which electrical arcs may be formed. Parallel spark gaps may thus be created, allowing shockwaves to be produced at more than one location around the circumference of the catheter. FIG. 6 shows an example of how a shockwave-generating unit 600 may comprise multiple holes across its surface. In this case, the holes 601 and 602 are located circumferentially opposite to the holes 603 and 604. In certain locations of the body, such as within a blood vessel, such a configuration may be useful as it allows multiple targeted shockwaves with a single voltage pulse discharge. The catheter thus does not need to be rotated within the vessel or body in order to target the opposite side. This may also have the effect of helping to increase the longevity of the conducting electrodes, as the power is now split between two of the arcs produced.

[0092] In order to increase the strength of the shockwave produced by the shockwave-generating unit of the present disclosure, the portion of the first and / or second electrode that is exposed to a surrounding environment may comprise a surface shape that is configured to concentrate the location of electrical arc discharge. This may take the form of an indent that may be introduced to the surface of the electrodes. Part of the reason the strength is increased when indents are present is because the depth of cut is effectively also increased. However, a large part of it is due to the effect of removing the available surface area for conduction of the current. As mentioned above, as the surface area is reduced, the charge tends to concentrate more intensely around the remaining surface area available, and thus more of the current is able to arc over to the other conducting electrode, resulting in an increase in the power of the shockwave produced.

[0093] Exemplary surface shapes are illustrated by Figures 7-10, which are discussed below.

[0094] FIG. 7A shows a shockwave-generating unit 700 where the first electrode 701 and the second electrode 702 have disposed on their outer surfaces the indents 703 and 704. These indents are concentrically aligned to the holes 705 and 706 on electrodes 701 and 702 respectively. The indents 703 and 704 take on the form of a hemispherical concave.

[0095] FIG. 7B further shows a close-up view of one of the indents 703 and 704 where 708 is the point at which the charges would concentrate to when the current arrives at the electrode 702. Because a large portion of the curved surface of the electrode 702 has been removed, the point 708 becomes the closest point of conduction where an arc may form with the other point 707 on electrode 701 through the conductive fluid. Alternative shapes of the indents may also be used to vary the power and consistency of the shockwave produced over time. These shapes affect the final topology of the exposed surface areas of the electrode once erosion from arc production sets in, and hence affects how much of the original power is retained after multiple instances of arc formation. FIG. 8 shows indents which are conical in shape, while FIG. 9 shows indents that are simply cylindrical debosses extending the holes into the material of the electrodes.

[0096] An alternative to the above indents may also be considered, where instead of a deboss or depression into the surface material of the electrode, a protrusion may be used instead. FIG. 10A-B illustrate what the corresponding shapes of FIG. 7A and FIG. 8 would look like if they were changed to protrusions. By forming a conical or hemispherical protrusion 1001 and 1002 respectively, the charge concentration may advantageously be intensified to a single point at the apex on either type of protrusion, enhancing the power of the resulting shockwaves.

[0097] A further embodiment of the shockwave-generating unit of the present disclosure is shown in FIG. 11. In this embodiment, the inner surface of the electrode assembly is formed from the first electrode 1102 and a first portion 1103a of an innermost electrically non-conductive layer

[0098] 1103. A second portion 1103b of the innermost electrically non-conductive layer 1103 disposed between the first electrode 1102 and the outermost electrically non-conductive layer

[0099] 1104. The second electrode 1101 is disposed between the first portion of the innermost electrically non-conductive layer and the outermost electrically non-conductive layer. This arrangement results in the innermost electrically non-conductive layer physically separating the first and second electrodes form each other. In this embodiment, the innermost electrically non-conductive layer may be considered an electrically non-conductive member. This arrangement can eliminate the need for a separate physical object placed between the conducting electrodes, which may confer advantages such as reducing the overall length and profile of the unit, increasing the flexibility of the catheter, and reducing the cost of production. This embodiment comprises an (outermost) electrically non-conductive layer 1104 that covers each of the first electrode 1101 and the second electrode 1102.

[0100] A further embodiment of the electrode assembly of the present disclosure is shown in FIG. 12A to FIG. 12C in the context of a shockwave generating unit. The shockwave-generating unit 1200 comprises a plurality of electrically non-conductive layers and more specifically, five electrically non-conductive layers 1204 to 1208 disposed over the outer surface of an axially extending elongate member 1203. First and second electrodes 1201 , 1202 are each independently embedded within one of the plurality of electrically non-conductive layers. Typically, the elongate member 1203 is formed from a polyimide.

[0101] In this embodiment, the electrode assembly is formed by the five electrically non-conductive layers 1204 to 1208, and the first and second electrodes 1201 , 1202. Together these components form a tubular configuration with an outer surface and an inner surface, the inner surface forming a lumen. The axially extending elongate member 1203 extends through the lumen.

[0102] The inner surface of the electrode assembly is formed from an innermost electrically non- conductive layer 1204. The outer surface of the electrode assembly is formed by an outermost electrically non-conductive layer 1208. The assembly comprises internal electrically non- conductive layers 1205, 1206, 1207 each disposed between the innermost layer and the outermost electrically non-conductive layers. In FIG. 12A-C there are three internal electrically non-conductive layers. The first internal electrically non-conductive layer 1205 is disposed over the innermost electrically non-conductive layer 1204, the second internal electrically non- conductive layer 1206 is disposed over the first internal electrically non-conductive layer 1205, and the third internal electrically non-conductive layer 1207 is disposed over the second internal electrically non-conductive layer 1206. The outermost electrically non-conductive layer 1208 is disposed over the third internal electrically non-conductive layer thereby forming the outer surface of the electrode assembly.

[0103] The outermost, innermost and internal electrically non-conductive layers may each be formed from a polymer independently selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), an epoxy resin (e.g. a hardened epoxy or a cured epoxy, preferably an epoxy that is biocompatible, impact resistant and / or shock absorbing), and a combination of two or more thereof. Typically, the first and third internal electrically non- conductive layers are formed from a polyimide, and the second internal electrically non- conductive layer is formed from an epoxy resin. Typically, the inner most electrically non- conductive layer is formed from an epoxy resin and the outermost electrically non-conductive layer is formed from a polyimide. The polyimide and / or epoxy resin may confer excellent impact resistance, high temperature and electrical resistance to the shockwave-generating unit.

[0104] In this embodiment, the first and second electrodes 1201 and 1202 are independently disposed (e.g. embedded) within one of the electrically non-conductive layers. In FIG. 12B, the first electrode 1201 is embedded within the innermost electrically non-conductive layer 1204 with the first, second, third internal and outermost electrically non-conductive layers 1205 to 1208 disposed over the innermost electrically non-conductive layer 1204. The second electrode 1202 is embedded within the second internal electrically non-conductive layer 1206. Preferably, the first electrode and the second electrode are offset with respect to each other along the longitudinal axis of the electrode assembly, and typically embedded within different electrically non-conductive layer with respect to each other. Typically, the two electrodes are separated by at least one electrically non-conductive layer formed from a polyimide. The inner most electrode (e g. the first electrode embedded in the innermost electrically non-conductive layer) may be thicker than the second electrode, which may help the first electrode resist stronger corrosion caused by a stronger shockwave within the deeper layer of the electrode assembly.

[0105] As the first and second electrodes 1201 and 1202 are embedded within the innermost and second internal electrically non-conductive layers respectively, the first hole 1209 extends through the outermost electrically non-conductive layer and the third, second and first internal electrically non-conductive layers to expose a portion of the first electrode 1201 to the surrounding environment. The second hole 1210 extends through the outermost electrically non-conductive layer and the third internal electrically non-conductive layer to expose a portion of the second electrode 1202 to the surrounding environment. Accordingly, the first hole 1209 is deeper than the second hole 1210. As explained hereinabove, a deeper hole can facilitate the focusing of shockwaves originating from within the channel created by the hole. This focusing effect gathers and enhances shockwave strength through constructive interference. On the other hand, a shallower hole confers a theoretically lower level of reflecting ability for shockwaves generated from within the channel, as less of the shockwaves are focused in one direction and are allowed to scatter in a diffused manner immediately upon exiting the hole. The holes may be arranged to be offset from each other along the longitudinal axis of the electrode assembly. Additionally, the holes may be arranged to be offset with respect to each other around the circumference of the electrode assembly.

[0106] The present invention may also be described by the following numbered clauses:

[0107] 1. A shockwave-generating unit for a shockwave-generating catheter comprising: an axially extending elongate member having an outer surface; a first electrode and a second electrode each disposed on the outer surface of the elongate member, the first and second electrodes being connectable to a high voltage power source; an electrically non-conductive member separating the first and second electrodes; at least one electrically non-conductive layer disposed over each of the first and second electrodes; a first hole extending through one or more of the at least one electrically non-conductive layers to expose a portion of the first electrode to a surrounding environment; a second hole extending through one or more of the at least one electrically non-conductive layers to expose a portion of the second electrode to a surrounding environment, wherein the first and second holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when a potential difference is applied across the first and second electrodes by the high voltage power source.

[0108] 2. The shockwave-generating unit according to Clause 1 , wherein the first and / or second electrodes are formed from one or more of the group consisting of tungsten, steel, titanium, cobalt, platinum, iridium, nickel, and an alloy thereof.

[0109] 3. The shockwave-generating unit according to Clause 1 or 2, wherein the electrically non-conductive member is formed from one or more of the group consisting of a polymer, a ceramic, an adhesive and a combination thereof, optionally wherein the polymer is selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), and a combination thereof, more optionally wherein the polymer comprises a polyimide.

[0110] 4. The shockwave-generating unit according to any one of the preceding clauses, wherein at least one of the at least one electrically non-conductive layer disposed over each of the first and second electrodes is formed from one or more of the group consisting of a polymer, a ceramic, an adhesive and a combination thereof, optionally wherein the polymer is selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), and a combination thereof, more optionally wherein the polymer comprises a polyimide.

[0111] 5. The shockwave-generating unit according to Clause 4, wherein an outermost electrically non-conductive layer of the at least one electrically non-conductive layer is formed from a polymer, optionally wherein the polymer is selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), and a combination thereof, more optionally wherein the polymer comprises a polyimide. 6. The shockwave-generating unit according to any one of the preceding clauses, wherein: the at least one electrically non-conductive layer disposed over each of the first and second electrodes comprises: a first electrically non-conductive layer disposed over each of the first and second electrodes; and a second electrically non-conductive layer disposed over each of the first and second electrodes; and the first and second holes each extend through the first and second electrically non- conductive layers.

[0112] 7. The shockwave-generating unit according to any one of the preceding clauses, wherein: the at least one electrically non-conductive layer disposed over each of the first and second electrodes comprises: a first electrically non-conductive layer disposed over each of the first and second electrodes; a second electrically non-conductive layer disposed over each of the first and second electrodes; and a third electrically non-conductive layer disposed over each of the first and second electrodes; the first and second holes each extend through the first, second and third electrically non-conductive layers.

[0113] 8. The shockwave-generating unit according to Clause 6 or 7, wherein: the first electrically non-conductive layer is formed from a polyimide or an adhesive; and the second electrically non-conductive layer is formed from a nylon, a poly(ether-b- amide) (e.g. Pebax®), or a heat-shrinkable tubing (e.g. fluorinated ethylene propylene or polyethylene terephthalate).

[0114] 9. The shockwave-generating unit according to any one of the preceding clauses, wherein the electrically non-conductive member has a maximum radius that corresponds to the maximum radius of the first and second electrodes. 10. The shockwave-generating unit according to any one of the preceding clauses, wherein the electrically non-conductive member has a maximum radius that is greater than the maximum radius of each of the first and second electrodes.

[0115] 11. The shockwave-generating unit according to any one of the preceding clauses, wherein the first and second holes are axially offset from each other.

[0116] 12. The shockwave-generating unit according to any one of Clauses 1 to 10, wherein the first and second holes are axially collinear.

[0117] 13. The shockwave-generating unit according to any one of the preceding clauses, wherein the first and second holes have substantially the same diameter.

[0118] 14. The shockwave-generating unit according to any one of Clauses 1 to 12 wherein the first and second holes have a different diameter from each other.

[0119] 15. The shockwave-generating unit according to any one of the preceding clauses, further comprising: a third hole extending through one or more of the at least one electrically non-conductive layers to expose a portion of the first electrode to a surrounding environment; a fourth hole extending through one or more of the at least one electrically non-conductive layers to expose a portion of the second electrode to a surrounding environment, wherein the third and fourth holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when the first and second electrodes are connected to a high voltage power source.

[0120] 16. The shockwave-generating unit according to any one of the preceding clauses, wherein the portion of the first and / or second electrode that is exposed to a surrounding environment comprises a surface shape that is configured to concentrate the location of electrical arc discharge.

[0121] 17. The shockwave-generating unit according to Clause 16, wherein the surface shape that is configured to concentrate the location of electrical arc discharge comprises a surface indent. 18. The shockwave-generating unit according to Clause 17, wherein the surface indent has a shape selected from the group consisting of hemispherical concave, conical, and cylindrical deboss (e g. a cylindrical deboss).

[0122] 19. The shockwave-generating unit according to Clause 16, wherein the surface shape that is configured to concentrate the location of electrical arc discharge comprises a surface protrusion, optionally wherein the surface protrusion has a conical or hemispherical shape.

[0123] 20. The shockwave-generating unit according to any one of the preceding clauses, wherein the electrically non-conductive member forms an electrically non-conductive layer disposed over the second electrode but not over the first electrode; and the second, and when present fourth, hole extends through the electrically non- conductive member and through one or more of the at least one electrically non-conductive layers to expose a portion of the second electrode to a surrounding environment.

[0124] 21 . The shockwave generating unit according to any one of the preceding clauses, wherein the first and second holes each have a diameter of from 0.2 to 1 mm.

[0125] 22. The shockwave generating unit according to any one of the preceding clauses, wherein a minimum distance from an edge of the first hole to an edge of the second hole is from 0.05 to 10 mm.

[0126] 23. The shockwave generating unit according to any one of the preceding clauses, wherein at least one of the at least one electrically non-conductive layer disposed over each of the first and second electrodes has a thickness of from 0.04 to 1 mm, optionally wherein each of the at least one electrically non-conductive layers disposed over each of the first and second electrodes has a thickness of from 0.04 to 1 mm.

[0127] 24. A shockwave-generating system for a shockwave-generating catheter comprising: one or more shockwave-generating unit as defined in any one of Clauses 1 to 23; a high voltage power source having an electrical output terminal electrically connected to the first and second electrodes of the one or more shockwave-generating units, wherein when the shockwave-generating system comprises more than one shockwave-generating unit, the electrodes of the shockwave-generating units are arranged in a series configuration, optionally wherein the high voltage power source has a voltage of from 1000 V to 5000

[0128] V.

[0129] 25. The shockwave-generating system according to Clause 24, wherein the electrical output terminal of the high voltage power source is connected to the first and second electrodes of the one or more shockwave-generating units by a wire that extends from the terminal along the outer surface of, or through an interior of, the axially extending elongate member.

[0130] 26. The shockwave-generating system according to Clause 24 or 25, further comprising an integrated electronic printed circuit board configured to determine the output voltage of the high voltage power source.

[0131] 27. A shockwave-generating catheter comprising: a shockwave-generating system as defined in any one of Clauses 24 to 26; and an inflatable balloon disposed over the axially extending elongate member and each of the one or more shockwave-generating units.

[0132] The invention has been described broadly and generically herein. Those of ordinary skill in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and / or configurations will depend upon the specific application or applications for which the teachings of the present invention is / are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and / or method described herein. In addition, any combination of two or more such features, systems, articles, materials, kits, and / or methods, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, is included within the scope of the present invention. Further, each of the narrower species and subgeneric groupings falling within the generic disclosure also form part of the invention. This includes the generic description of the invention with a proviso or negative limitation removing any subject matter from the genus, regardless of whether or not the excised material is specifically recited herein.

Claims

Claims1. An electrode assembly for a shockwave-generating catheter, said electrode assembly comprising: at least one electrically non-conductive layer, a first electrode and a second electrode, the first and second electrodes being physically separated from each other and connectable to a voltage power source; the electrode assembly having a tubular configuration with an outer surface and an inner surface, the inner surface forming a lumen, the outer surface of the electrode assembly formed from an outermost electrically non- conductive layer of the at least one electrically non-conductive layer, the outermost electrically non-conductive layer being disposed over the first electrode and the second electrode; a first hole extending through the at least one electrically non-conductive layer to expose a portion of the first electrode to a surrounding environment; a second hole extending through the at least one electrically non-conductive layer to expose a portion of the second electrode to a surrounding environment, wherein the first and second holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when a potential difference is applied across the first and second electrodes by the voltage power source.

2. The electrode assembly of claim 1 , wherein the inner surface of the electrode assembly is formed from an innermost electrically non-conductive layer.

3. The electrode assembly of claim 2, wherein the electrode assembly further comprises one or more internal electrically non-conductive layers each disposed between the innermost layer and the outermost electrically non-conductive layers.

4. The electrode assembly of claim 3, wherein the electrode assembly further comprises at least two internal electrically non-conductive layers, for example, two, three, four, five or six internal electrically non-conductive layers.

5. The electrode assembly of any one of claims 3 to 4, wherein the first and second electrodes are each independently embedded within the innermost electrically non-conductive layer or one of the internal electrically non-conductive layers.

6. The electrode assembly of any one of claim 2 to 5, wherein the first and second electrodes are each embedded within different electrically non-conductive layers.

7. The electrode assembly of any one of claims 2 to 6, wherein the first electrode is embedded within the innermost electrically non-conductive layer.

8. The electrode assembly of any one of claims 2 to 6, wherein the first and second electrodes are each independently embedded within one of the internal electrically non- conductive layers.

9. The electrode assembly of any one of claims 3 to 8, wherein each of the one or more internal electrically non-conductive layers are formed from a polymer independently selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), an epoxy resin, and a combination of two or more thereof.

10. The electrode assembly of any one of claims 3 to 9, wherein the electrode assembly comprises:- a first internal electrically non-conductive layer disposed over the innermost electrically non-conductive layer;- a second internal electrically non-conductive layer disposed over the first internal electrically non-conductive layer;- a third internal electrically non-conductive layer disposed over the second internal electrically non-conductive layer; and the outermost electrically non-conductive layer disposed over the third internal electrically non-conductive layer thereby forming the outer surface of the electrode assembly.11 . The electrode assembly of claim 10, wherein- the first internal electrically non-conductive layer is formed from a polyimide;- the second internal electrically non-conductive layer is formed from an epoxy resin;- the third internal electrically non-conductive layer is formed from a polyimide.

12. The electrode assembly of claim 11 , wherein the first electrode is embedded within the innermost electrically non-conductive layer and the second electrode is embedded within the second internal electrically non-conductive layer.

13. The electrode assembly of any one of claims 2 to 11 , wherein the innermost electrically non-conductive layer is formed from an epoxy resin.

14. The electrode assembly of any one of claims 2 to 12, wherein the outermost electrically non-conductive layer is formed from an impact resistant and / or shock absorbing material, for example the outermost electrically non-conductive layer is formed from an epoxy resin that is impact resistant and / or shock absorbing.

15. The electrode assembly of any one of claims 2 to 14, wherein the first electrode and the second electrode are offset with respect to each other along the longitudinal axis of the electrode assembly.16 The electrode assembly of claim 1 , wherein the inner surface of the electrode assembly is formed from an innermost layer comprising the first and second electrodes and an electrically non-conductive member, wherein the electrically non-conductive member physically separates the first and second electrodes from each other.

17. The electrode assembly of claim 16, wherein the electrode assembly further comprises one or more internal electrically non-conductive layers each disposed between the innermost layer and the outermost electrically non-conductive layer.

18. The electrode assembly of claim 16 or 17, wherein the electrically non-conductive member is formed from one or more of the group consisting of a polymer, a ceramic, an epoxy, an adhesive and a combination thereof, optionally wherein the polymer is selected from the group consisting of a thermoplastic elastomer (e.g. a polyimide), a fluoropolymer (e.g. fluorinated ethylene propylene (FEP) or polytetrafluoroethylene (PTFE)), and a combination thereof, for example, wherein the polymer comprises a polyimide.

19. The electrode assembly of any one of claims 16 to 18, wherein the electrically non- conductive member has a maximum radius that corresponds to the maximum radius of the first and second electrodes.

20. The electrode assembly of any one of claims 16 to 18, wherein the electrically non- conductive member has a maximum radius that is greater than the maximum radius of each of the first and second electrodes.21 . The electrode assembly of claim 1 , whereinthe inner surface of the electrode assembly is formed from the first electrode and a first portion of an innermost electrically non-conductive layer; a second portion of the innermost electrically non-conductive layer disposed between the first electrode and the outermost electrically non-conductive layer; the second electrode disposed between the first portion of the innermost electrically non-conductive layer and the outermost electrically non-conductive layer.

22. The electrode assembly of claim 21 , wherein the innermost electrically non-conductive layer is formed from a nylon, a poly(ether-b-amide) (e.g. Pebax®), or a heat-shrinkable tubing (e.g. fluorinated ethylene propylene or polyethylene terephthalate); and the outermost electrically non-conductive layer is formed from an impact resistant and / or shock absorbing material, for example the outermost electrically non-conductive layer is formed from an epoxy resin that is impact resistant and / or shock absorbing.

23. The electrode assembly of any one of the preceding claims, wherein the first and / or second electrodes are formed from one or more of the group consisting of tungsten, steel, titanium, cobalt, platinum, iridium, nickel, and an alloy thereof.

24. The electrode assembly of any one of the preceding claims, wherein the first and second holes are offset with respect to other along the longitudinal axis of the electrode assembly.

25. The electrode assembly of any one of claims 1 to 23, wherein the first and second holes are offset with respect to each other around the circumference of the electrode assembly.

26. The electrode assembly of any one of the preceding claims, wherein the first and second holes have substantially the same diameter.

27. The electrode assembly of any one of claims 1 to 25, wherein the first and second holes have a different diameter from each other.

28. The electrode assembly of any one of the preceding claims, wherein the portion of the first and / or second electrode that is exposed to a surrounding environment comprises a surface shape that is configured to concentrate the location of electrical arc discharge.

29. The electrode assembly of claim 28, wherein the surface shape that is configured to concentrate the location of electrical arc discharge comprises a surface indent.

30. The electrode assembly of claim 28, wherein the surface indent has a shape selected from the group consisting of hemispherical concave, conical, and cylindrical deboss (e.g. a cylindrical deboss).31 . The electrode assembly of claim 28, wherein the surface shape that is configured to concentrate the location of electrical arc discharge comprises a surface protrusion, optionally wherein the surface protrusion has a conical or hemispherical shape.

32. The electrode assembly of any one of the preceding claims, wherein the first and second holes each have a diameter of from about 0.2 mm to about 1 mm.

33. The electrode assembly of any one of the preceding claims, wherein a minimum distance from an edge of the first hole to an edge of the second hole is from about 0.05 mm to about 10 mm.

34. The electrode assembly of any one of the preceding claims, wherein at least one of the electrically non-conductive layers has a thickness of from about 0.02 mm to about 0.8 mm, optionally wherein each of the at least one electrically non-conductive layers has a thickness of from about 0.02 mm to about 0.8 mm.

35. The electrode assembly of any one of the preceding claims, further comprising: a third hole extending through the at least one electrically non-conductive layer to expose a portion of the first electrode to a surrounding environment; a fourth hole extending through the at least one electrically non-conductive layer to expose a portion of the second electrode to a surrounding environment, wherein the third and fourth holes are configured to allow an electrical arc discharge to pass from the first to the second electrode or vice versa when the first and second electrodes are connected to a high voltage power source.

36. A shockwave-generating unit comprising an electrode assembly of any one of the preceding claims and an axially extending elongate member that extends through the lumen of the electrode assembly, optionally wherein the axially extending elongate member comprises an outer surface comprising a polyimide.

37. A shockwave-generating system for a shockwave-generating catheter comprising: one or more shockwave-generating unit of claim 36;a high voltage power source having an electrical output terminal electrically connected to the first and second electrodes of the one or more shockwave-generating units, optionally wherein the high voltage power source has a voltage of from 1000 V to 5000 V.

38. The shockwave-generating system according to claim 37, wherein the electrical output terminal of the high voltage power source is connected to the first and second electrodes of the one or more shockwave-generating units by a wire that extends from the terminal along the outer surface of, or through an interior of, the axially extending elongate member.

39. The shockwave-generating system according to claim 37 or 38, further comprising an integrated electronic printed circuit board configured to determine the output voltage of the high voltage power source.

40. A shockwave-generating catheter comprising: a shockwave-generating system of one of claims 37 to 39; and an inflatable balloon disposed over the axially extending elongate member and each of the one or more shockwave-generating units.

Images