US20080091193A1 - Irrigated ablation catheter having magnetic tip for magnetic field control and guidance - Google Patents

Abstract

Embodiments of the present invention provide an irrigated ablation electrode assembly for use with an irrigated catheter device comprises at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly; a permanent magnet; a shield separating the permanent magnet from the at least one passageway and from an exterior, the shield being substantially less oxidizable than the permanent magnet; and an electrode having an external electrode surface. A catheter guidance control and imaging system drives the permanent magnet to guide and control the catheter tip. In specific embodiments, the irrigation fluid flow paths through the electrode assembly are thermally insulated from the electrode and temperature sensor. The irrigation fluid is directed at target areas where coagulation is more likely to occur. One or more monitoring electrodes are provided for mapping or other monitoring functions.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation-in-part of U.S. patent application Ser. No. 11/948,362, filed on Nov. 30, 2007, which is a continuation-in-part of U.S. patent application Ser. No. 11/434,200, filed May 16, 2006, the entire disclosures of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
• a. Field of the Invention
• The present invention pertains generally to ablation catheters and electrode assemblies. More particularly, the present invention is directed toward ablation electrode assemblies for use in the human body having a magnetic tip for magnetic field control and guidance, a mechanism for irrigating targeted areas, and mapping characteristics.
• b. Background Art
• Electrophysiology catheters are used for an ever-growing number of procedures. For example, catheters are used for diagnostic, therapeutic, and ablative procedures, to name just a few examples. Typically, the catheter is manipulated through the patient's vasculature and to the intended site, for example, a site within the patient's heart.
• The catheter typically carries one or more electrodes, which may be used for ablation, diagnosis, or the like. There are a number of methods used for ablation of desired areas, including for example, radiofrequency (RF) ablation. RF ablation is accomplished by transmission of radiofrequency energy to a desired target area through an electrode assembly to ablate tissue at the target site.
• Because RF ablation may generate significant heat, which if not carefully monitored and/or controlled can result in protein denaturation, blood coagulation, excess tissue damage, such as steam pop, tissue charring, and the like, it is desirable to monitor the temperature of the ablation assembly. It is further desirable to include a mechanism to irrigate certain target areas with biocompatible fluids, such as saline solution. This irrigation reduces or avoids excess, unwanted tissue damage, as well as blood coagulation and problems associated therewith. However, introduction of this irrigation solution may inhibit the ability to accurately monitor and/or control the temperature of the ablation assembly during use.
• There are typically two classes of irrigated electrode catheters, open and closed irrigation catheters. Closed ablation catheters typically circulate a cooling fluid within the inner cavity of the electrode. Open ablation catheters, on the other hand, typically deliver the cooling fluid through open orifices on the electrode. Examples of these known catheters include the THERMOCOOL brand of catheters marketed and sold by Biosense-Webster. The current open irrigated ablation catheters use the inner cavity of the electrode, or distal member, as a manifold to distribute saline solution. The saline thus flows directly through the open orifices of the distal electrode member. This direct flow through the distal electrode tip lowers the temperature of the distal tip during operation, rendering accurate monitoring and control of the ablative process more difficult.
• In these open electrode irrigated catheters, it has been determined that insulating the irrigation channels from the ablation electrode is beneficial. One such example was published on or around March 2005 in an article entitled “Saline-Irrigated Radiofrequency Ablation Electrode with Electrode Cooling,” by Drs. Wittkampf and Nakagawa et al., the content of which is hereby incorporated by reference in its entirety. Similarly, the content of PCT International Publication No. WO 05/048858, published on Jun. 2, 2005, is hereby incorporated by reference in its entirety.
• Recently, magnetic systems have been proposed, wherein magnetic fields produced by one or more electromagnets are used to guide and advance a magnetically tipped catheter. For example, U.S. Patent Application Publication No. 2007/0016006 discloses an apparatus and a method for guiding, steering, and advancing invasive devices and for accurately controlling their positions for providing positioning of magnetic fields and field gradient, for providing fields configured to push/pull, bend/rotate, and by further enabling apparatus to align the distal end of the catheter tip so as to achieve controlled movement in 3D space and ability of apparatus to control the magnetic field characteristics, preferably without excessively large power and field intensities that are potentially dangerous to medical personnel and that can be disruptive to other equipment. The entire disclosure of US 2007/0016006 is incorporated herein by reference.
BRIEF SUMMARY OF THE INVENTION
• Embodiments of the present invention provide an irrigated catheter configured to provide better electrode surface cooling and more accurate electrode tip temperature measurement, and having a magnetic tip that can be magnetically guided and controlled. The irrigated catheter may further include one or more monitoring or measuring electrodes for mapping or the like. The irrigation fluid is directed at target areas where coagulation is more likely to occur so as to minimize blood coagulation and the associated problems. In some embodiments, the invention further provides for significant improvements over known irrigation catheters, including those disclosed by Wittkampf and Nakagawa et al., by providing a multiple piece irrigated ablation electrode assembly that has the advantages of irrigating the target area while simultaneously improving the operation, temperature response, temperature monitoring and/or control mechanisms of the ablation assembly, so as to prevent unwanted, unnecessary tissue damage and blood coagulation.
• The present invention is directed to improved irrigated ablation electrode assemblies and methods useful in conjunction with irrigated catheter and pump assemblies and RF generator assemblies designed to monitor and control the ablation process while minimizing blood coagulation and unnecessary tissue damage, and with catheter guidance control and imaging systems designed to guide and control the magnetic tips of the electrode assemblies and perform mapping and other imaging functions.
• In accordance with an aspect of the present invention, an irrigated ablation electrode assembly for use with an irrigated catheter device comprises at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly; a permanent magnet; a shield separating the permanent magnet from the at least one passageway and from an exterior, the shield being substantially less oxidizable than the permanent magnet; and an electrode having an external electrode surface.
• In some embodiments, the electrode forms at least a portion of the shield, and comprises an electrically conductive material that is substantially less oxidizable than the permanent magnet. The electrically conductive material is selected from the group consisting of platinum, gold, tantalum, iridium, stainless steel, palladium, and mixtures thereof, and the electrically conductive material is plated onto a substrate made of a biocompatible material that is substantially less oxidizable than the permanent magnet. The shield comprises one or more materials selected from the group consisting of silicone, polyimide, platinum, gold, tantalum, iridium, stainless steel, palladium, and mixtures thereof. In one example, the permanent magnet comprises NdFeB. At least one mapping electrode is spaced proximally from the electrode which is a distal electrode capable of ablation.
• In specific embodiments, the electrode is disposed at a distal portion of the electrode assembly and includes an external electrode surface, and the electrode assembly further comprises a proximal portion which includes at least one proximal passageway for a fluid with an outlet disposed at an external surface of the proximal portion. The proximal portion comprises a material which is electrically nonconductive and has a lower thermal conductivity than a material of the electrode. The at least one proximal passageway extends toward the electrode at an acute angle with respect to the longitudinal axis of the proximal portion. The proximal portion comprises a material which is electrically nonconductive; the external surface of the proximal portion and the external electrode surface of the electrode at the distal portion meet at an intersection; and the at least one proximal passageway is configured to direct a fluid flow through the outlet toward a region adjacent the intersection. The permanent magnet is disposed in the distal portion, and the electrode assembly further comprises at least one temperature sensor disposed in the permanent magnet. The electrode includes an external electrode surface, and the electrode includes at least one electrode passageway for a fluid with an outlet disposed at the external electrode surface. The at least one electrode passageway is thermally insulated from the distal member by a poor thermal conductive material which is lower in thermal conductivity than a material of the electrode.
• In some embodiments, the permanent magnet comprises an annular permanent magnet with an axial opening to permit fluid flow to the at least one electrode passageway, and the electrode assembly further comprises a fluid lumen extending through the axial opening of the annular permanent magnet to the at least one electrode passageway. The fluid lumen comprises stainless steel braided polyimide forming a portion of the shield, and the electrode forms another portion of the shield. The shield includes a silicone seal to prevent fluid from reaching the annular permanent magnet via a junction between the electrode and the fluid lumen. The electrode is disposed at a distal portion of the electrode assembly, and the electrode assembly further comprises a proximal portion which includes at least one proximal passageway for a fluid with an outlet disposed at an external surface of the proximal portion. The proximal portion comprises a material which is electrically nonconductive. The external surface of the proximal portion and the external electrode surface of the electrode at the distal portion meet at an intersection. The at least one proximal passageway is configured to direct a fluid flow through the outlet toward a region adjacent the intersection.
• In accordance with another aspect of the invention, an irrigated ablation electrode assembly for use with an irrigated catheter device comprises a permanent magnet, at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly, the at least one passageway extending through the permanent magnet; an inner shield separating the permanent magnet from the at least one passageway, the inner shield being substantially less oxidizable than the permanent magnet; and an outer shield separating the permanent magnet from an exterior, the inner shield being substantially less oxidizable than the permanent magnet.
• In some embodiments, the inner shield comprises a fluid lumen supplying fluid to the at least one passageway. The electrode assembly includes an electrode that has an external electrode surface and forms at least a portion of the outer shield. The electrode is disposed at a distal portion of the electrode assembly; the electrode assembly further comprises a proximal portion having a material which is electrically nonconductive; and the proximal portion forms at least a portion of the inner shield.
• In accordance with another aspect of this invention, a catheter comprises a shaft; and an irrigated ablation electrode assembly coupled to a distal end of the shaft. The irrigated ablation electrode assembly has at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly; a permanent magnet; a shield separating the permanent magnet from the at least one passageway and from an exterior, the shield being substantially less oxidizable than the permanent magnet; and an electrode having an external electrode surface.
• In some embodiments, the catheter further comprises a second permanent magnet disposed near the distal end of the shaft and spaced from the permanent magnet in the irrigated ablation electrode assembly.
• The foregoing and other aspects, features, details, utilities, and advantages of the present invention will be apparent from reading the following description and claims, and from reviewing the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is an isometric view of an ablation electrode assembly according to an embodiment of the present invention in conjunction with an irrigated catheter assembly operably connected to an RF generator assembly and a pump assembly.
• FIG. 2 is an enlarged, isometric view of the ablation electrode assembly according to an embodiment of the present invention operably connected to an irrigated catheter assembly.
• FIG. 3 is a cross-sectional view of the ablation electrode assembly ofFIG. 2 taken along line4-4 ofFIG. 2.
• FIG. 4 is a cross-sectional view of an ablation electrode assembly according to another embodiment of the present invention.
• FIG. 4A is a cross-sectional view of an ablation electrode assembly according to another embodiment of the present invention.
• FIG. 5 is a cross-sectional view of an ablation electrode assembly according to another embodiment of the present invention.
• FIG. 6 is a perspective view of the magnet structure of the Catheter Guidance Control and Imaging (CGCI) system.
• FIG. 7A is a perspective view of the CGCI right section showing the hydraulically actuated core extended.
• FIG. 7B is a perspective view of the CGCI right section showing the hydraulically actuated core extracted.
• FIG. 7C is a system block diagram for a surgery system that includes an operator interface, a catheter guidance system, and surgical equipment.
• FIG. 7D is a block diagram of the imaging module for use in a CGCI surgery procedure that includes the catheter guidance system, a radar system, Hall Effect sensors, and a hydraulically actuating core extension mechanism.
• FIG. 8A is a first perspective view of a catheter assembly.
• FIG. 8B is a second perspective view of the catheter assembly.
• FIG. 9A is a side view of the apparatus ofFIG. 6.
• FIG. 9B is an underside view of the apparatus ofFIG. 6.
• FIG. 10 is an isometric view showing the apparatus ofFIG. 6 in an open mode where the left and right clusters are separated.
• FIG. 11 is a side view of the configuration shown inFIG. 10.
• FIG. 12 is an underside view of the configuration shown inFIG. 10.
• FIG. 13 is an end view of the configuration shown inFIG. 10.
• FIG. 14 is a block diagram of one embodiment of the CGCI apparatus with magnetic sensors.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
• Irrigated Catheter with Magnetic Tip
• In general, the instant invention relates to irrigated ablation electrode assemblies, and to methods of manufacturing and using such irrigated ablation electrode assemblies. For purposes of this description, similar aspects among the various embodiments described herein will be referred to by the same reference number. As will be appreciated, however, the structure of the various aspects may be different among the various embodiments.
• As seen inFIG. 1, the ablation electrode assembly may comprise part of an irrigatedablation catheter assembly12, operably connected to apump assembly15 and anRF generator assembly14 which serves to facilitate the operation of ablation procedures through monitoring any number of chosen variables (e.g., temperature of the ablation electrode, ablation energy, and position of the assembly), assist in manipulation of the assembly during use, and provide the requisite energy source delivered to theelectrode assembly10. The present embodiments describe RF ablation electrode assemblies and methods, but it is contemplated that the present invention is equally applicable to any number of other ablation electrode assemblies where the temperature of the device and the targeted tissue areas is a factor during the procedure.
• FIG. 1 is a general perspective view of an irrigated ablation catheter assembly having anRF generator assembly14 and afluid pump assembly15 operably connected to an irrigatedcatheter assembly12 having an irrigatedelectrode assembly10 according to the present invention operably attached thereto. The structural and functional features of thecatheter assembly12 and theRF generator assembly14 and pumpassembly15 are well-known to those of skill in the art. For example, the RF generator assembly could be an IBI-1500T RF Cardiac Ablation Generator available from Irvine Biomedical, Inc. in Irvine, Calif. 92614. The RF generator assembly could also be any other known assembly, including, for example, a Stockert RF generator available from Biosense, or one of the Atakr® series of RF generators available from Medtronic. The pump assembly can be any known assembly, including fixed volume rolling pumps, variable volume syringe pumps, and any other pump assembly known to those of skill in the art.FIGS. 2-5, discussed in more detail below, exemplify various embodiments of the irrigatedablation electrode assembly10 according to the present invention.
• FIG. 2 is an isometric view of anablation electrode assembly11 connected to an irrigatedablation catheter assembly12 having afluid delivery tube16 therein. Theablation electrode assembly11 generally comprises anirrigation member20 and anablation electrode member18. The orientation of themembers18,20 are generally such that theablation electrode assembly18 is situated at the distal end of the assembly with theirrigation member20 located at the proximal end of the assembly, although it is conceivable the orientation could be reversed. Theproximal member20 has at least one passageway24 (seeFIG. 3) and at least oneoutlet22 for delivery of a fluid to targeted tissue areas and the outside of theelectrode assembly11. Thedistal member18 further comprises at least one temperature sensing mechanism26 (seeFIG. 3) disposed therein and operably connected to theRF generator assembly14. Thedistal member18 is comprised of any electrically, and potentially thermally, conductive material known to those of ordinary skill in the art for delivery of ablative energy to target tissue areas. Examples of the electrically conductive material include gold, platinum, iridium, palladium, tantalum, stainless steel, and any mixtures thereof. Moreover, there are a number of electrode designs contemplated within the scope of the present invention including tip electrodes, ring electrodes, and any combination thereof.
• In general accordance with the embodiments described herein, the fluid passageway(s)24 and outlet(s)22 are separated from thedistal member18, and accordingly thetemperature sensing mechanism26, by at least one poor thermally conductive material. A poor thermally conductive material is one with physical attributes that decrease heat transfer between the passageway(s)24 and thedistal member18 by about 10% or more, and more preferably by about 25% or more measured by known methods to one of ordinary skill in the art. In particular embodiments, materials that decreased heat transfer by more than approximately 75% performed favorably. It is further contemplated that a poor thermally conductive material could have physical attributes that decrease heat transfer less than about 10%, provided that the remaining structural components are selected with the appropriate characteristics and sensitivities to maintain adequate monitoring and control of the process. Thus, while these properties are preferred, the poor thermally conductive material may be any material known to one of skill in the art consistent with the spirit of the invention. Examples of poor thermally conductive materials useful in conjunction with the present invention include, but are not limited to, high-density polyethylene (HDPE), polyimides, polyaryletherketones, polyetheretherketones, polyurethane, polypropylene, oriented polypropylene, polyethylene, crystallized polyethylene terephthalate, polyethylene terephthalate, polyester, ceramics, and plastics such as acetal, and mixtures thereof.
• As shown in more detail with respect to specific embodiments below, the poor thermally conductive material may be the material comprising theproximal member20, or thedistal member18, a separate material from theproximal member20 and thedistal member18, or any combination thereof. Additionally, the passageway(s)24 and outlet(s)22 defined by theproximal member18 may also be separated longitudinally from the end46 (seeFIG. 3) of thedistal member18 thereby providing the benefit of insulating the passageway(s)24 from the temperature sensor(s)26 for improved temperature monitoring of the ablated target area during operation. The poor thermally conductive material, and the separation from thetemperature sensing mechanism26 disposed near the end46 of thedistal member18, serve individually, and cooperatively, to minimize the effect of the lower temperature of the fluid delivered through the passageway(s)24 and outlet(s)22 from the temperature sensing mechanism(s)26 within thedistal member18. The separation of the passageway(s)24 and outlet(s)22 from thedistal member18, and more particularly thetemperature sensing mechanism26, facilitates the dual purposes of (1) effectively irrigating theelectrode assembly11 and the targeted tissue area to minimize coagulation and unwanted tissue damage and (2) effectively controlling the operation of theablation electrode assembly11 in accordance with objects of the present invention.
• FIG. 3 is a cross-sectional view of an embodiment of theablation electrode assembly11. Anablation electrode assembly11 is connected to an irrigatedcatheter assembly12 having afluid delivery tube16 and a catheter shaft17. Theablation electrode assembly11 comprises a proximal member ormanifold20, adistal member18, and atemperature sensing mechanism26 operably connected to the RF generator assembly14 (seeFIG. 1). In this embodiment, theproximal member20 itself is comprised of a poor thermally conducting material that serves to insulate the irrigation fluid from the remaining portions of theassembly11. Preferably theproximal member20 is made from a poor thermally conductive polymer, more preferably from a polyether ether ketone (“PEEK”) because of this material's combination of thermal and physical properties. Another possible material is Ultem® polyetherimide. Theproximal member20 is configured to receive thefluid tube16 of thecatheter assembly12 and comprises a plurality of passageways24 (e.g., 4-8 passageways) extending from acentral axis28 of theassembly11 axially toward the outer portion of theproximal member20 terminating in correspondingoutlets22. Preferably, the plurality ofpassageways24 are equally distributed around theproximal member20 so as to provide equal distribution of fluid to the targeted tissue area and the outside of theassembly11. Thepassageway24 may be a single, annular passageway, or a number of individual passageways equally distributed around theproximal member20. In this embodiment, thepassageways24 are at an acute angle with respect to thelongitudinal axis28 of theassembly11. In operation, fluid is pumped through thedelivery tube16 and passes through thepassageways24 and through theoutlets22 where it contacts with targeted tissue areas and the outside portion of theablation electrode assembly11.
• In this embodiment, the fluid delivery conduits orpassageways24 extend at an angle substantially less than perpendicular to thelongitudinal axis28. Angling of thepassageways24 away from perpendicular, but less than parallel, further assists in the delivery of the fluid to the targeted tissue areas, further decreases the risk of coagulation of the bodily fluids during ablation procedures, and allows for improved measurement and control of theablation assembly11 during operation. More specifically, thepassageways24 are oriented to direct irrigation fluid flow at the target area adjacent, preferably immediately adjacent, the intersection between theproximal member20 and thedistal member18. Blood coagulation is more likely to occur in the target area due to a sharp rise in RF intensity, material discontinuity, and potentially geometric discontinuity caused by manufacturing imperfection in joining theproximal member20 and thedistal member18. In specific embodiments, thepassageways24 extend at an angle between approximately 20 and 70 degrees, preferably at an angle between approximately 30 and 60 degrees, and more preferably at an angle of approximately 30 degrees. It is also contemplated that the passageways may be further angled in a second dimension, such that the passageways and orifices are configured to provide fluid to the external portion of the assembly in a swirling, or helical fashion. This configuration also serves to keep the fluid in closer proximity to the electrode assembly, thereby further preventing against coagulation during operation.
• Thedistal member18 of theablation electrode assembly11 has a generally cylindrical shape terminating in a rounded end which may be a hemispherical end or an end that is non-spherical. Thedistal member18 includes apermanent magnet48 at least partially encased in adistal electrode shell50 and anelectrode anchor52. Thepermanent magnet48 is desirably made of NdFeB which has a strong magnetic field so that only one such permanent magnet is needed for magnetic field control and guidance of the catheter tip (instead of a plurality of magnets spaced apart from each other). Other rare earth permanent magnets with similar characteristics may be used in other embodiments. If two or more permanent magnets are used, additional materials may be considered. Thepermanent magnet48 typically has a length of about 2-6 mm, typically about 4 mm, in the longitudinal direction. Thedistal electrode shell50 provides most of the external surface of the distal electrode. Theelectrode anchor52 is coupled to theproximal member20 and connected to a power line or cable such as anRF wire54. Theelectrode anchor52 may be connected to theproximal member20 by any known mechanism including adhesives, press-fit configurations, snap-fit configurations, or the like. Aninner tube56 is connected to theelectrode anchor52 and/or theproximal member20 to accommodate thepower line54 and the temperature sensor conductor for thetemperature sensor26. Because thetemperature sensor26 is embedded in thepermanent magnet48, the permanent magnet material preferably is a good thermal conductor (e.g., NdFeB) so that thetemperature sensor26 can measure the temperature of the distal electrode accurately.
• In the embodiment shown, thedistal electrode shell50, theelectrode anchor52, and theinner tube56 form a shield that keeps thepermanent magnet48 from exposure to irrigation and/or bodily fluids, comprising an inner shield that separates thepermanent magnet48 from the irrigation fluid including thepassageways24 and an outer shield that separates thepermanent magnet48 from the exterior. Because thepermanent magnet48 is highly oxidizable, any contact between the permanent magnet and liquid is undesirable since oxidation of thepermanent magnet48 can lead to corrosion problems. The shield prevents such contact from occurring. The materials for the shield are less oxidizable, preferably substantially less oxidizable, than thepermanent magnet48. For instance, the oxidization rate of a shield material is less than about 50%, more preferably less than about 20%, most preferably less than about 5%, of the oxidation rate of thepermanent magnet48. Thedistal electrode shell50 and theelectrode anchor52 are made of an electrically conductive material such as platinum, gold, tantalum, iridium, stainless steel, palladium, tantalum, and mixtures thereof. The electrically conductive material selected is preferably biocompatible. In some embodiments, the biocompatible electrically conductive material is plated onto a substrate made of copper or beryllium copper to improve the biocompatibility of thedistal electrode shell50 and theelectrode anchor52. Theelectrode anchor52 may be laser welded to thedistal electrode shell50. Theinner tube56 may be made of silicone, polyimide, stainless steel braided polyimide, or the like. Theinner tube56 may be thermally bonded or molded onto theplatinum anchor52. In alternate embodiments, thedistal electrode shell50 and theelectrode anchor52 form a complete shield around thepermanent magnet48 without the need for theinner tube56 for separating thepermanent magnet48 from irrigation fluid flow.
• Theproximal member20 preferably is made of a poor thermally conductive material (as discussed above) having a thermal conductivity that is lower, more preferably substantially lower, than the thermal conductivity of the material of thedistal member18. Theproximal passageways24 do not come into contact with any interior portion of thedistal member18. In this way, the irrigation fluid flowing through theproximal passageways24 is substantially insulated from the electrode and the temperature sensor of thedistal member18 by distance and material of poor conductivity, so that thetemperature sensor26 can more accurately measure the temperature of the distal electrode. The proximal members may be made of a variety of materials that have insulating properties such as, for example, acetal, polyetheretherketone (PEEK), and high-density polyethylene (HDPE), as well as other materials of poor thermal conductivity mentioned above.
• One or more monitoring or measuring electrodes may be provided in thecatheter assembly12 for mapping or other monitoring or measuring functions.FIG. 3 shows twomonitoring electrodes58,59 that are ring electrodes spaced from thedistal electrode18. To facilitate catheter tip positioning and location in a mapping system, the position of each electrode is determined. Calibration of the positioning system is achieved by the twomonitoring electrodes58,59 separated by a known interelectrode distance, or by thedistal electrode18 and one monitoring electrode (58 or59) that are separated by a predetermined distance. In use, a voltage is sensed between one electrode on the catheter assembly12 (typically the distal electrode18) and a reference electrode on the patient's body (suitably a surface electrode on the patient's skin). For a catheterization procedure which is to lead to ablation, sensing is performed to gather data relating to the heart, such as the location of an arrhythmia focus. Such data gathering techniques are well known in the art. The location information is determined based on the calibration (see, e.g., U.S. Pat. Nos. 5,697,377 and 5,983,126, the entire disclosures of which are incorporated herein by reference), and the sensed information and location are stored and/or mapped.
• FIG. 4 is a cross-sectional view of another embodiment of theablation electrode assembly61. Theablation electrode assembly61 is connected to an irrigatedcatheter assembly62 having a fluid delivery tube orlumen64 and acatheter shaft66. Theablation electrode assembly61 comprises adistal member68, apermanent magnet70 disposed proximal to thedistal member68, and ashell72 surrounding the outer surface and the proximal surface of thepermanent magnet70. Thedistal member68 has a generally cylindrical shape terminating in a rounded end which may be a hemispherical end or an end that is non-spherical. Thepermanent magnet70 is an annular member having an inner surface covered by a portion of thefluid delivery tube64. Thepermanent magnet70 is desirably made of NdFeB which has a strong magnetic field so that only one such permanent magnet is needed for magnetic field control and guidance of the catheter tip (instead of a plurality of magnets spaced apart from each other). Thepermanent magnet48 typically has a length of about 2-6 mm, typically about 4 mm in the longitudinal direction. Thedistal member68,shell72, andfluid delivery tube64 form a shield that keeps thepermanent magnet70 from exposure to liquid, comprising an inner shield that separates thepermanent magnet70 from the irrigation fluid flowing through thecatheter assembly62 and an outer shield that separates thepermanent magnet70 from the exterior. Asealant74 is preferably provided between the proximal surface of thedistal member68 and the distal surface of thepermanent magnet70 to further ensure no liquid reaches thepermanent magnet70 via the junction between thedistal member68 and thefluid delivery tube64.
• Thedistal member68 provides the external surface of the distal electrode. Theshell72 may also be an electrically conductive surface to provide additional external surface of the distal electrode. In that case, theelectrode shell72 is connected to a power cable or line such as anRF wire76. One ormore temperature sensors77 may be provided in thedistal member68 and thetemperature sensor conductor78 for thetemperature sensor77 extends proximally through thecatheter shaft66.
• Because thepermanent magnet70 is highly oxidizable, any contact between the permanent magnet and liquid is undesirable. The shield prevents such contact from occurring. The materials for the shield are less oxidizable, preferably substantially less oxidizable, than thepermanent magnet70. Thedistal member68 and theelectrode shell72 are made of an electrically conductive material such as platinum, gold, tantalum, iridium, stainless steel, palladium, tantalum, and mixtures thereof. The electrically conductive material selected is preferably biocompatible. In some embodiments, the biocompatible electrically conductive material is plated onto a substrate made of copper or beryllium copper to improve the biocompatibility of thedistal member68 and theelectrode shell72. Thefluid delivery tube64 is electrically nonconductive, and may be made of silicone, polyimide, stainless steel braided polyimide, or the like. Theelectrode shell72 is connected to thedistal member68 by laser weld or the like. Thedistal member68 and theelectrode shell72 form the distal electrode. Theshell72 may be connected to thecatheter shaft66 using adhesives or the like. Thefluid delivery tube64 may be connected to theshell72,permanent magnet70, anddistal member68 by thermal bonding, molding, adhesives, or the like.
• Thefluid delivery tube64 flows fluid through one or moredistal passageways79 in thedistal member68 to their external outlets. There is preferably a central passageway along the longitudinal axis of thedistal member68 and, optionally, additional passageways distributed around the central passageway. Thepassageways79 are preferably lined with a poor thermally conductingmaterial75 such as a polyether ether ketone (“PEEK”) that serves to insulate the fluid from the material of thedistal member68 and from thetemperature sensor77. In this way, the fluid flow through thepassageways79 does not influence the measurement of thetemperature sensor77, so that thetemperature sensor77 can more accurately measure the temperature of the distal electrode. Preferably, the additional passageways are equally distributed around the central passageway so as to provide equal distribution of fluid to the targeted tissue area and the outside of theassembly61.
• One or more monitoring or measuring electrodes may be provided in thecatheter assembly62 for mapping or other monitoring or measuring functions.FIG. 4 shows onemonitoring electrode80 that is a ring electrode spaced from the distal electrode (formed by thedistal member68 and the electrode shell72) by a known interelectrode distance for calibration. In use, a voltage is sensed between the distal electrode (68 and72) and a reference electrode on the patient's body (suitably a surface electrode on the patient's skin). The location information is determined based on the calibration, and the sensed information and location are stored and/or mapped.
• FIG. 4A shows an irrigatedcatheter assembly62A that is virtually identical to the irrigatedcatheter assembly62 ofFIG. 4. Theassembly62A includes a second permanent magnet70A disposed near the distal end of theshaft66 and spaced from the firstpermanent magnet70. In the embodiment shown, the second permanent magnet70A is an annular magnet and is smaller in size and thickness than the firstpermanent magnet70. The second permanent magnet70A does not require an additional shield because it is disposed in a space between thecatheter shaft66 and thefluid delivery tube64 which is free from exposure to liquid. Of course, the second permanent magnet may have other configurations in different embodiments, and may be formed in the irrigatedablation electrode assembly61 instead of being inside thecatheter shaft66 and spaced proximally from theelectrode assembly61. Additional permanent magnets in the assembly may provide additional options for magnetically controlling and guiding the catheter tip.
• FIG. 5 is a cross-sectional view of another embodiment of the ablation electrode assembly81 which is connected to an irrigatedcatheter assembly82. The electrode assembly81 ofFIG. 5 is similar to theelectrode assembly61 ofFIG. 4, in that it also includes adistal member68, apermanent magnet70, ashell72 connected to anRF wire76, asealant74, and atemperature sensor77 connected to atemperature sensor conductor78. In this embodiment, thedistal member68 has acentral passageway79 that is preferably lined with a poor thermally conductingmaterial75 such as a polyether ether ketone (“PEEK”). Afluid delivery tube64 extends through acatheter shaft66 to the electrode assembly81. One or more monitoring or measuringelectrodes80 may be provided in thecatheter assembly62 for mapping or other monitoring or measuring functions.
• InFIG. 5, the ablation electrode assembly81 includes aproximal member84 located on the proximal side of thepermanent magnet70 andelectrode shell72. Theproximal member84 has at least oneproximal passageway86 with at least oneoutlet88 for delivery of a fluid to targeted tissue areas and the outside of the electrode assembly81. The proximal passageway(s)86 and outlet(s)88 are separated from thedistal member68 andelectrode shell72, and accordingly thetemperature sensing mechanism77, by at least one poor thermally conductive material. The poor thermally conductive material may be the material comprising theproximal member84, or thedistal member68, a separate material from theproximal member84 and thedistal member68, or any combination thereof. In this embodiment, theproximal member84 is comprised of a poor thermally conducting material that serves to insulate the fluid from the remaining portions of the assembly81. Theproximal member84 is configured to receive thefluid tube64 of thecatheter assembly82 and comprises a plurality of proximal passageways86 (e.g., 4-8 passageways) extending from a central axis of the assembly81 axially toward the outer portion of theproximal member84 terminating in correspondingoutlets88. Preferably, the plurality ofproximal passageways86 are equally distributed around theproximal member84 so as to provide equal distribution of fluid to the targeted tissue area and the outside of the assembly81. Theproximal passageway86 may be a single, annular passageway, or a number of individual passageways equally distributed around theproximal member84. In this embodiment, theproximal passageways86 are at an acute angle with respect to the longitudinal axis of the assembly81. In operation, fluid is pumped through thedelivery tube64 and passes through theproximal passageways86 and through theoutlets88 where it contacts with targeted tissue areas and the outside portion of the ablation electrode assembly81.
• In this embodiment, theproximal passageways86 extend at an angle substantially less than perpendicular to the longitudinal axis. Angling of thepassageways86 away from perpendicular, but less than parallel, further assists in the delivery of the fluid to the targeted tissue areas, further decreases the risk of coagulation of the bodily fluids during ablation procedures, and allows for improved measurement and control of the ablation assembly81 during operation. More specifically, theproximal passageways86 are oriented to direct irrigation fluid flow at the target area adjacent, preferably immediately adjacent, the intersection between theproximal member84 and theelectrode shell72. Blood coagulation is more likely to occur in the target area due to a sharp rise in RF intensity, material discontinuity, and potentially geometric discontinuity caused by manufacturing imperfection in joining theproximal member84 and theelectrode shell72. In specific embodiments, theproximal passageways24 extend at an angle between approximately 20 and 70 degrees, preferably at an angle between approximately 30 and 60 degrees, and more preferably at an angle of approximately 30 degrees. It is also contemplated that the proximal passageways may be further angled in a second dimension, such that the proximal passageways and orifices are configured to provide fluid to the external portion of the assembly in a swirling, or helical fashion. This configuration also serves to keep the fluid in closer proximity to the electrode assembly, thereby further preventing against coagulation during operation.
• Theproximal member84 further includes a longitudinal outlet that transfers fluid through acentral conduit90 to thecentral passageway79 of thedistal member68. Thecentral conduit90 is electrically nonconductive, and may be made of silicone, polyimide, stainless steel braided polyimide, or the like. Thecentral conduit90 may be connected to theelectrode shell72,permanent magnet70, anddistal member68 by thermal bonding, molding, adhesives, or the like. Thedistal member68,electrode shell72, andcentral conduit90 form a shield that separates thepermanent magnet70 from the irrigation fluid and the exterior.
• Catheter Guidance Control and Imaging (CGCI)
• One example of a system for magnetically guiding and controlling a catheter having a magnetic tip is found in U.S. Patent Application Publication No. 2007/0016006, the entire disclosure of which is incorporated herein by reference.FIGS. 6, 7A, and7B are isometric drawings of a Catheter Guidance Control and Imaging (CGCI) system1500 (FIG. 7C), having aleft coil cluster100 and aright coil cluster101 provided torails102. Therails102 act as guide alignment devices. TheCGCI system workstation1500 includes astructural support assembly120, ahydraulic system140, and apropulsion system150.
• Acentral arc106 supports an uppercylindrical coil110 and twoshorter arcs107,108 support two conical shapedcoils115,116. The twoshorter arcs107,108 are displaced from thecentral arc106 by approximately 35 degrees. The angle of separation between the two smaller arcs is approximately 70 degrees. At the end of eacharc106,107 and108 is a machined block of 1010 steel with a connection that provides for attachment of thecoil assemblies115,116,110.
• Twocurved shield plates105 form a shield to at least partially contain and shape the magnetic fields. Theshields105 also provide lateral strength to the assembly. A base117 houses thepropulsion system150 andlocking mechanism118. In one embodiment, theplates105 are made from steel, nickel, or other magnetic material.
• In addition toFIG. 6,FIGS. 7A and 7B further show various mechanical details which form the CGCI cluster half section (right electromagnetic cluster101). A lockinghole103, a spur-drive rail104,cam rollers118, and thesolenoid locking pin119, are configured to allow portions of the CGCI to move along thetracks102. Thecluster101 includes three electromagnets forming a magnetic circuit. Theleft coil116 andright coil115 are mounted as shown and are supported by C-Arms107 and108. Thecoil110 includes a hydraulically actuatedcore111, supported by acoil clamping disc127 made of stainless steel. A coilstress relief disc113 is made of Teflon. Thecoil cylinder110, is enclosed by acoil base disc114 made of stainless steel. Thecoil core111 is actuated (extended and retracted) by ahydraulic system109.FIG. 7B shows theright coil cluster101 with the hydraulically actuatedcore111 retracted by the use of thehydraulic system109 which allows the CGCI to shape the magnetic field.
• FIG. 7C is a system block diagram for asurgery system800 that includes anoperator interface500, theCGCI system1500, surgical equipment502 (e.g., acatheter tip11 inFIG. 3, acatheter tip61 inFIG. 4, a catheter tip81 inFIG. 5, or acatheter tip377 inFIG. 8A, etc.), one or moreuser input devices900, and apatient390. Theuser input devices900 can include one or more of a joystick, a mouse, a keyboard, avirtual tip905, and other devices to allow the surgeon to provide command inputs to control the motion and orientation of the catheter tip377 (ortip11,61,81).
• In one embodiment, theCGCI system1500 includes acontroller501 and animaging synchronization module701.FIG. 7C shows the overall relationship between the various functional units and theoperator interface500,auxiliary equipment502, and thepatient390. In one embodiment, theCGCI system controller501 calculates the Actual Tip (AT) position of the distal end of a catheter. Using data from the Virtual Tip (VT)905 and the imaging andsynchronization module701, theCGCI system controller501 determines the position error, which is the difference between actual tip position (AP) and the desired tip position (DP). In one embodiment, thecontroller501 controls electromagnets to move the catheter tip in a direction selected to minimize the position error (PE). In one embodiment, theCGCI system controller501 provides tactile feedback to the operator by providing force-feedback to theVT905.
• FIG. 7D is a block diagram of asurgery system503 that represents one embodiment of theCGCI system1500. Thesystem503 includes thecontroller501, aradar system1000, a Halleffect sensor array350, and the hydraulically actuatedmechanism140. In one embodiment, thesensor350 includes one or more Hall effect magnetic sensors. Theradar system1000 can be configured as an ultra-wideband radar, an impulse radar, a Continuous-Wave (CW) radar, a Frequency-Modulated CW (FM-CW) radar, a pulse-Doppler radar, etc. In one embodiment, theradar system1000 uses Synthetic Aperture Radar (SAR) processing to produce a radar image. In one embodiment, theradar system1000 includes an ultra-wideband radar such as described, for example, in U.S. Pat. No. 5,774,091, hereby incorporated by reference in its entirety.
• In one embodiment, theradar1000 is configured as a radar range finder to identify the location of thecatheter tip377. Theradar1000 is configured to locate reference markers (fiduciary markers) placed on thepatient390. Data regarding location of the reference markers can be used, for example, forimage capture synchronization701. The motorized hydraulically and actuatedmotion control mechanism140 allows the electromagnets of the cylindrical coils51AT and51DT (seeFIG. 14) to be moved relative to thepatient390.
• In one embodiment, the use of the radar for identifying the position of thecatheter tip377 has advantages over the use of Fluoroscopy, Ultrasound, Magnetostrictive sensors, or SQUID. Radar can provide accurate dynamic position information, which provides for real-time, relatively high resolution, relatively high fidelity compatibility in the presence of strong magnetic fields. Self-calibration of the range measurement can be based on time-of-flight and/or Doppler processing. Radar further provides for measurement of catheter position while ignoring “Hard” surfaces such as a rib cage, bone structure, etc., as these do not interfere with measurement or hamper accuracy of the measurement. In addition, movement and displacement of organs (e.g., pulmonary expansion and rib cage displacement as well as cardio output during diastole or systole) do not require an adjustment or correction of the radar signal. Radar can be used in the presence of movement since radar burst emission above 1 GHz can be used with sampling rates of 50 Hz or more, while heart movement and catheter dynamics occur at 0.1 Hz to 2 Hz.
• In one embodiment, the use of theradar1000 reduces the need for complex image capture techniques normally associated with expensive modalities such as fluoroscopy, ultrasound, Magnetostrictive technology, or SQUID which require computationally intensive processing in order to translate the pictorial view and reduce it to a coordinate data set. Position data synchronization of thecatheter tip377 and the organ in motion is readily available through the use of theradar1000. Theradar1000 can be used with phased-array or Synthetic Aperture processing to develop detailed images of the catheter location in the body and the structures of the body. In one embodiment, the radar system includes an Ultra Wide Band (UWB) radar with a relatively high resolution swept range gate. In one embodiment, a differential sampling receiver is used to effectively reduce ringing and other aberrations included in the receiver by the near proximity of the transmit antenna. As with X-ray systems, the radar system can detect the presence of obstacles or objects located behind barriers such as bone structures. The presence of different substances with different dielectric constants such as fat tissue, muscle tissue, water, etc., can be detected and discerned. The outputs from the radar can be correlated with similar units such as multiple catheters used in electrophysiology (EP) studies while detecting spatial location of other catheters present in the heart lumen. Theradar system1000 can use a phased array antenna and/or SAR to produce 3D synthetic radar images of the body structures, catheter tip and organs.
• In one embodiment, the location of the patient relative to the CGCI system (including the radar system1000) can be determined by using theradar1000 to locate a plurality of fiduciary markers. In one embodiment, the data from theradar1000 is used to locate the body with respect to an imaging system. The catheter position data from theradar1000 can be superimposed (synchronized) with the images produced by the imaging system. The ability of the radar and the optionalHall effect sensors350 to accurately position thecatheter tip377 relative to the stereotactic frame allows the pole pieces to be moved by theactuators109,140 to optimize the location of the magnet poles with respect to thepatient390 and thus reduce the power needed to manipulate the catheter tip.
• FIGS. 8A and 8B shows one embodiment of acatheter assembly375 andguidewire assembly379 to be used with theCGCI apparatus1500. Thecatheter assembly375 is a tubular tool that includes acatheter body376 which extends into aflexible section378 that possesses sufficient flexibility for allowing a relatively more rigidresponsive tip377 to be steered through the patient. Thetip377 can be replaced by the tip21 ofFIG. 3, thetip61 ofFIG. 4, or the tip81 ofFIG. 5.
• In one embodiment, themagnetic catheter assembly375 in combination with theCGCI apparatus1500 reduces or eliminates the need for the plethora of shapes normally needed to perform diagnostic and therapeutic procedures. During a conventional catheterization procedure, the surgeon often encounters difficulty in guiding the conventional catheter to the desired position, since the process is manual and relies on manual dexterity to maneuver the catheter through a tortuous path of, for example, the cardiovascular system. Thus, a plethora of catheters in varying sizes and shapes are to be made available to the surgeon in order to assist him/her in the task, since such, tasks require different bends in different situations due to natural anatomical variations within and between patients.
• By using theCGCI apparatus1500, only a single catheter is needed for most, if not all patients. The catheterization procedure is now achieved with the help of theCGCI system1500 that guides the magnetic catheter andguidewire assembly375 and379 to the desired position within the patient'sbody390 as dictated by the surgeon's manipulation of thevirtual tip905. The magnetic catheter andguidewire assembly375,379 (i.e. themagnetic tip377 can be attracted or repelled by the electromagnets of the CGCI apparatus1500) provides the flexibility needed to overcome tortuous paths, since theCGCI apparatus1500 overcomes most, if not all the physical limitations faced by the surgeon while attempting to manually advance thecatheter tip377 through the patient's body.
• In one embodiment, thecatheter tip377 includes aguidewire assembly379, aguidewire body380 and atip381 response to magnetic fields. Thetip377 is steered around sharp bends so as to navigate a torturous path. Theresponsive tips377 and381 of both thecatheter assembly375 and theguidewire assembly379, respectively, include magnetic elements such as permanent magnets. Thetips377 and381 include permanent magnets that respond to the external flux generated by theelectromagnets110,115,116 and itssymmetric counterpart100.
• In one embodiment, theresponsive tip377 of thecatheter assembly375 is tubular, and theresponsive tip381 of theguidewire assembly379 is a solid cylinder. Theresponsive tip377 of thecatheter assembly375 is a dipole with longitudinal polar orientation created by the two ends of the magnetic element positioned longitudinally within it. Theresponsive tip381 of theguidewire assembly379 is a dipole with longitudinal polar orientation created by two ends of themagnetic element377 positioned longitudinally within it. These longitudinal dipoles allow the manipulation of bothresponsive tip377 and381 with theCGCI apparatus1500, as theelectromagnet assemblies100,101, and will act on thetips377 and381 and “drag” them in unison to a desired position as dictated by the operator.
• FIGS. 9A and 9B show additional views of the CGCIstructural support assembly120. Thestructural support assembly120 is configured so as to facilitate the use of X-Ray and/or other surgicalmedical equipment502 in and around the patient during operation. The twosymmetrical left100 and right101 electromagnetic clusters are mounted on the stainlesssteel guide rails102, allowing the twosections100 and101 to move away from each other as shown inFIGS. 10-12. Therails102 are bolted to a floor or mounting pad. The cluster on theCGCI structure120 rolls inside therails102, under relatively tight tolerance to prevent lateral or vertical movement during a seismic event. In one embodiment, therails102 are designed to withstand the forces of a Zone4 seismic event without allowing the CGCI structure to escape containment.
• A stainless steel spurtoothed rail104 is bolted to the floor or mounting pad under theCGCI structure120. A Servo Dynamic model HJ96 C-44 brushless servomotor128 (max 27 lb.-in torque) with its associated servomotor amplifier model 815-BL129 are provided to move theclusters101,100. The motor has a reduction gearbox with a ratio of 100:1. A stainless steel spur gear attached to the reduction gear shaft meshes with the spurtoothed rail104. Thepropulsion system150 is configured to exert up to 2700 lbs. of force to move theCGCI sections100 and101.
• FIGS. 9A and 9B further show theCGCI assembly120 when the system is set in the “operational mode.” The twosymmetrical clusters100 and101 are engaged as described above.FIGS. 9A and 9B show the location of the spurtoothed rail104 and thebrushless servo motor128.
• FIGS. 10-13 are isometric views of theCGCI assembly120 when its main twosymmetric left100 and right101 coil clusters are in a fully open mode (non operational) and the magnetic cores are retracted. The rear view of the symmetrical one half of the CGCI shows the parabolic flux collector shields105 with the C-Arm uppercylinder coil support106. In one embodiment, theCGCI assembly120 is configured to meet the structural as well as safety considerations associated with the generation of a magnetic field of 2 Tesla.
• FIG. 14 depicts theCGCI system1500 top architecture showing the major elements comprising thecontroller501 of the magnetic circuit. Thecontroller501 includes a system memory, a torque/force matrix algorithm residing in528 and a CPU/computer527. The CPU/computer such asPC527 provides computation and regulation tasks.FIG. 14 further shows the six-coil electromagnetic circuit formed out ofcoils51A,51B,51C,51D,51AT and51DT and the magnetic field sensors (MFS)351,352,353,354,355 and356 such asHall sensor ring350 mounted on an assembly forming the X, Y, and Z axis controls. A D/A converter550 and an I/O block551 provide communication between thecontroller501 and thecoils51A and thehydraulic systems140. The sixchannel DC amplifier525 provides current to the coils.
• FIG. 14 shows the relationship and command structure between thejoystick900, thevirtual tip905, and theCPU701. TheCPU701 displays control conveying real time images generated by the X-ray,radar1000, or other medical imaging technologies such as fluoroscopy, MRI, PET SCAN, CAT SCAN, etc., on adisplay730. A flow diagram of the command structure of the control scheme is shown by the use of the 2D virtual plane coil polarity matrixes. By assigning the coil position and polarity elements to the directions of torque rotation and force field gradient on each 2D plane of a six coil cluster414, a computer program such as MathLab or Math Cad is able to sift through the combination matrixes and compute the proper combination for the six coil current polarities and amplitudes. In one embodiment, a boundary condition controller is used for regulating the field strength405 and field gradient406 in the effective region. Thecontroller501 computes the fields in the neighborhood of thecatheter tip377 and as defined by the fields on the 2D planes in the effective area. Rules for computing the fields with rotated coil on the surface of the sphere are set forth in US 2007/0016066.
• In one embodiment, look-up tables are used as a reference library for use by thecontroller501. Lookup tables of the setting of various scenarios of force as well as torque position and magnitude allow thecontroller501 to use a learning algorithm for the control computations. The look-up tables shorten the computational process for optimal configuration and setting of the coil currents and pole positions. The D/A and A/D system550 allows the connection of voltage and current measuring instruments as well as input from the magnetic field sensor (MFS)350 array, theMFS351,352,353,354,355 and356. The magnetic field sensor measuring the boundary plane field strength allows the CGCI to use a low-level logic algorithm to compute the positions, settings, coil currents, etc. The low-level simulation is performed prior to activating the power section of theCGCI apparatus1500, thus providing a “soft” level check prior to action performed by actual machine. The two-level control architecture that starts with low-level simulation architecture of low-level simulation allows the surgeon or operator of theCGCI apparatus1500 to test each movement prior to actually performing the move. US 2007/0016066 describes the field regulator loop outlined inFIG. 14 using theHall effect ring350.
• Instead of using the radar system to identify the position of thecatheter tip377, the present invention may rely on the use of the monitoring or measuring electrodes (58,59 inFIG. 3;80 inFIGS. 4 and 5), optionally in conjunction with a visualization and mapping tool such as the EnSite NavX™ technology available from St. Jude Medical, Inc. See, e.g., U.S. Pat. Nos. 6,990,370 and 6,939,309, the entire disclosures of which are incorporated herein by reference.
• All directional references (e.g., upper, lower, upward, downward, left, right, leftward, rightward, top, bottom, above, below, vertical, horizontal, clockwise, and counterclockwise) are only used for identification purposes to aid the reader's understanding of the present invention, and do not create limitations, particularly as to the position, orientation, or use of the invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.

Claims (25)

1. An irrigated ablation electrode assembly for use with an irrigated catheter device, the irrigated ablation electrode assembly comprising:

at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly;

a permanent magnet;

a shield separating the permanent magnet from the at least one passageway and from an exterior, the shield being substantially less oxidizable than the permanent magnet; and

an electrode having an external electrode surface.

2. The irrigated ablation electrode assembly ofclaim 1, wherein the electrode forms at least a portion of the shield, and wherein the electrode comprises an electrically conductive material that is substantially less oxidizable than the permanent magnet.

3. The irrigated ablation electrode assembly ofclaim 2 wherein the electrically conductive material is selected from the group consisting of platinum, gold, tantalum, iridium, stainless steel, palladium, and mixtures thereof, and wherein the electrically conductive material is plated onto a substrate made of a biocompatible material that is substantially less oxidizable than the permanent magnet.

4. The irrigated ablation electrode assembly ofclaim 1 wherein the shield comprises one or more materials selected from the group consisting of silicone, polyimide, platinum, gold, tantalum, iridium, stainless steel, palladium, and mixtures thereof.

5. The irrigated ablation electrode assembly ofclaim 1 wherein the permanent magnet comprises NdFeB.

6. The irrigated ablation electrode assembly ofclaim 1 further comprising at least one mapping electrode spaced proximally from the electrode which is a distal electrode capable of ablation.

7. The irrigated ablation electrode assembly ofclaim 1 wherein the electrode is disposed at a distal portion of the electrode assembly, and wherein the electrode assembly further comprises a proximal portion which includes at least one proximal passageway for a fluid with an outlet disposed at an external surface of the proximal portion.

8. The irrigated ablation electrode assembly ofclaim 7 wherein the proximal portion comprises a material which is electrically nonconductive and has a lower thermal conductivity than a material of the electrode.

9. The irrigated ablation electrode assembly ofclaim 7 wherein the at least one proximal passageway extends toward the electrode at an acute angle with respect to the longitudinal axis of the proximal portion.

10. The irrigated ablation electrode assembly ofclaim 7 wherein the proximal portion comprises a material which is electrically nonconductive, and wherein the external surface of the proximal portion and the external electrode surface of the electrode at the distal portion meet at an intersection, and wherein the at least one proximal passageway is configured to direct a fluid flow through the outlet toward a region adjacent the intersection.

11. The irrigated ablation electrode assembly ofclaim 7 wherein the permanent magnet is disposed in the distal portion, and wherein the electrode assembly further comprises at least one temperature sensor disposed in the permanent magnet.

12. The irrigated ablation electrode assembly ofclaim 1 wherein the electrode includes at least one electrode passageway for a fluid with an outlet disposed at the external electrode surface.

13. The irrigated ablation electrode assembly ofclaim 12 wherein the at least one electrode passageway is thermally insulated from the distal member by a poor thermal conductive material which is lower in thermal conductivity than a material of the electrode.

14. The irrigated ablation electrode assembly ofclaim 12 wherein the permanent magnet comprises an annular permanent magnet with an axial opening to permit fluid flow to the at least one electrode passageway, and wherein the electrode assembly further comprises a fluid lumen extending through the axial opening of the annular permanent magnet to the at least one electrode passageway.

15. The irrigated ablation electrode assembly ofclaim 14 wherein the fluid lumen comprises stainless steel braided polyimide forming a portion of the shield, and wherein the electrode forms another portion of the shield.

16. The irrigated ablation electrode assembly ofclaim 15 wherein the shield includes a silicone seal to prevent fluid from reaching the annular permanent magnet via a junction between the electrode and the fluid lumen.

17. The irrigated ablation electrode assembly ofclaim 12 wherein the electrode is disposed at a distal portion of the electrode assembly, and wherein the electrode assembly further comprises a proximal portion which includes at least one proximal passageway for a fluid with an outlet disposed at an external surface of the proximal portion, wherein the proximal portion comprises a material which is electrically nonconductive, wherein the external surface of the proximal portion and the external electrode surface of the electrode at the distal portion meet at an intersection, and wherein the at least one proximal passageway is configured to direct a fluid flow through the outlet toward a region adjacent the intersection.

18. An irrigated ablation electrode assembly for use with an irrigated catheter device, the irrigated ablation electrode assembly comprising:

a permanent magnet,

at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly, the at least one passageway extending through the permanent magnet;

an inner shield separating the permanent magnet from the at least one passageway, the inner shield being substantially less oxidizable than the permanent magnet; and

an outer shield separating the permanent magnet from an exterior, the outer shield being substantially less oxidizable than the permanent magnet.

19. The irrigated ablation electrode assembly ofclaim 18 wherein the inner shield comprises a fluid lumen supplying fluid to the at least one passageway.

20. The irrigated ablation electrode assembly ofclaim 18 further comprising an electrode having an external electrode surface, and wherein the electrode forms at least a portion of the outer shield.

21. The irrigated ablation electrode assembly ofclaim 20 wherein the electrode is disposed at a distal portion of the electrode assembly, wherein the electrode assembly further comprises a proximal portion having a material which is electrically nonconductive, and wherein the proximal portion forms at least a portion of the inner shield.

22. A catheter comprising:

a shaft; and

an irrigated ablation electrode assembly coupled to a distal end of the shaft, the irrigated ablation electrode assembly having at least one passageway for a fluid with an outlet disposed at an external surface of the electrode assembly; a permanent magnet; a shield separating the permanent magnet from the at least one passageway and from an exterior, the shield being substantially less oxidizable than the permanent magnet; and an electrode having an external electrode surface.

23. The catheter ofclaim 22 wherein the electrode is disposed at a distal portion of the electrode assembly, and wherein the electrode assembly further comprises a proximal portion which includes at least one proximal passageway for a fluid with an outlet disposed at an external surface of the proximal portion.

24. The catheter ofclaim 22 wherein the electrode includes at least one electrode passageway for a fluid with an outlet disposed at the external electrode surface, wherein the permanent magnet comprises an annular permanent magnet with an axial opening to permit fluid flow to the at least one electrode passageway, and wherein the catheter further comprises a fluid lumen extending through the axial opening of the annular permanent magnet to the at least one electrode passageway.

25. The catheter ofclaim 22 further comprising a second permanent magnet disposed near the distal end of the shaft and spaced from the permanent magnet in the irrigated ablation electrode assembly.

Images