WO2000028894A1

WO2000028894A1 - Electrode marker assemblies for medical instruments

Info

Publication number: WO2000028894A1
Application number: PCT/EP1999/008728
Authority: WO
Inventors: Robert E. Woodard; Josef V. Koblish; Thomas Jenkins
Original assignee: Boston Scientific Limited
Priority date: 1998-11-12
Filing date: 1999-11-12
Publication date: 2000-05-25
Also published as: AU1162500A

Abstract

A medical device (20) is disclosed having an elongate body (24), e.g. a catheter, a plurality of electrodes (34) carried on the exterior surface of the elongate body, and a corresponding plurality of radiopaque markers (40) also carried by the elongate body, each marker underlying a respective electrode for identifying the electrodes when viewed using fluoroscopic imaging.

Description

DESCRIPTION

Electrode Marker Assemblies For Medical Instruments

Field Of The Invention

The present invention relates to fluoroscopic markers for identifying electrodes disposed on invasive medical instruments, such as diagnostic and therapeutic catheters.

Background Of The Invention

Medical instruments, such as invasive diagnostic and therapeutic catheters, allow access to internal regions of a patient's body through relatively small incisions made in a vein or artery located in the leg, groin, or neck for diagnosing and treating a number of internal maladies.

For example, diagnostic and therapeutic catheter assemblies have been developed which can locate and eliminate irregular electrophysiological activity on the myocardial tissue of the heart. Such assemblies typically include an elongated catheter body having one or more operative electrodes located at one end that is inserted into a chamber of the heart. Electrical activity on the myocardial tissue wall of the heart may be detected by sensing a voltage potential between a selected pair of bi- polar electrodes located on the catheter when pressed against respective tissue locations. Once located, unwanted electrical pathways in the myocardial tissue are discontinued by ablating the pertinent tissue regions with RF electrical energy emitted from one or more electrodes located on the same, or different, catheter assembly.

During the mapping or ablation procedure, it is necessary for the attending physician to precisely locate and identify each of the respective diagnostic or therapeutic electrode elements on the catheter in order to properly perform the procedure. This is normally done with the aid of a fluoroscope, which allows the physician to view objects having a sufficient radiographic density relative to the patient's body tissue.

In accordance with another technique disclosed in U.S. Patent Application Serial No. 08/976,194, filed November 21, 1997, radiopaque electrode bands are employed, which function as both electrodes, i.e., the bands are electrically conductive, and as markers, i.e., the bands have radiopaque properties that make them visible with a fluoroscope. A platinum alloy is preferably used as the material for these dual-purpose bands because it has relatively low electrical resistance and relatively high radiopacity .

Other electrode materials exist that exhibit conductive properties that are as good or better than platinum alloys (and often less expensive) , but with less effective radiopaque properties. Similarly, other materials exist that exhibit radiopaque properties that are as good or better than platinum alloys, but with less effective conductive properties. Further, these other materials often are not bioco patible .

Summary Of The Invention

The present invention is directed to electrode marker assemblies, which have both superior fluoroscopic imaging properties and superior conductive qualities, for use on diagnostic and/or therapeutic medical instruments.

In one preferred embodiment, an electrophysiology catheter is provided having an elongate catheter body, a plurality of substantially non-radiopaque electrodes carried by the catheter body and a corresponding plurality of radiopaque markers for identifying the non-radiopaque electrodes when viewed .using fluoroscopic imaging. In accordance with one aspect of the present invention, the markers are encased by either the non-radiopaque electrodes or by the catheter body, thereby preventing contact with body tissue or blood. In particular, by sealing the markers from contact with body tissue or blood allows less expensive, non- biocompatible materials to be used for the markers, which also need not be conductive. The electrodes may also be made of less expensive material that is not required to be radiopaque.

Other features and advantages of the inventions are set forth in the following detailed description and drawings, which are intended to illustrate, but not limit, the invention.

Brief Description Of The Drawings

FIG. 1 is a perspective view of a catheter and handle assembly used for diagnostic and/or therapeutic purposes and includes a preferred distal end electrode marker assembly that embodies the features of the invention;

FIG. 2 is a partial, perspective view of a distal end assembly of the catheter in FIG. 1;

FIGS. 3A-3D are partial, cross-sectional views of an electrode marker assembly constructed in accordance with a first preferred embodiment of the invention;

FIGS. 4A and 4B are a partial, side-elevational view and an end view of an electrode marker assembly constructed in accordance with another preferred embodiment of the invention;

FIGS. 5A and 5B are a partial, side-elevational view and an end view of an electrode marker assembly constructed in accordance with a further preferred embodiment of the invention; FIGS. 6A-6C are partial, cross-sectional views of an electrode marker assembly constructed in accordance with a still further preferred embodiment of the invention;

FIG. 7 is a cross-sectional view of a marker assembly constructed in accordance with yet another preferred embodiment of the invention; FIGS. 8A-8C are side elevational views of a tip assembly constructed in accordance with an alternative preferred embodiment of the invention;

FIG. 9 is a partial, cross-sectional view of an electrode marker assembly constructed in accordance with yet another preferred embodiment of the invention;

FIG. 10 is a partial, cross-sectional view of an electrode marker assembly constructed in accordance with a still further embodiment of the invention; FIG. 11 is a partial, side view of an alternate preferred distal end electrode assembly for use with the catheter shown in FIG. 1;

FIG. 12 is an enlarged side view of the distal electrodes and catheter tip of the electrode assembly of FIG. 11;

FIG. 13 depicts a first preferred method of attaching the distal tip of the electrode assembly of FIG. 11; and

FIG. 14 depicts a second preferred method of attaching the distal tip of the electrode assembly of FIG. 11; and FIG. 15 is a partial side view of a still further alternate preferred distal end for use with a catheter assembly including a pull wire attached to the distal tip of the catheter for creating loop formations; and

FIG. 16 is an enlarged view of the distal end of the catheter of FIG. 15.

Detailed Description Of Preferred Embodiment

With reference to FIGS. 1 and 2, catheter assembly 20 is an exemplary invasive medical device that the encased electrode matters of the present invention will be described in conjunction with. However, it will be readily understood by those skilled in the art that the present invention may be used in conjunction with any device having electrodes that need to be identified. The catheter assembly 20 includes a handle 22 and an elongated tubular catheter 24. The catheter 24 is made of a highly flexible, low durometer, non-conductive polymer material such as Pebax® or Pellethane®. The catheter 24 has a proximal portion 26 with a proximal end 28 that engages the handle 22, and a distal portion 30 carrying a plurality of electrodes proximate a distal end 32. In particular, the distal portion 30 of the catheter 24 carries a plurality of external, conductive, non-radiopaque ring electrodes 34. The ring electrodes 34 are at defined points along the catheter body 24 and the number of electrodes 34 may vary depending on the purpose of the catheter assembly. Typically, the number of electrodes 34 ranges from three to thirty-two.

The ring electrodes 34 are preferably made of highly conductive, low-cost, non-radiopaque materials such as solid rings of stainless steel, or silver or silver chloride printed-on conductive ink or paint (FIG. 3A) . If the electrodes 34 are solid conductive rings, the distal portion 30 of the catheter 24 will preferably include longitudinal channels for carrying the electrode bands so that the outer surface of the solid rings are flush with the outer surface of the catheter 24. Electrodes made of a silver or silver chloride based printed conductive ink or paint are desirable because they are inexpensive to manufacture, and are more attuned to recording electrical activity in cardiac tissue during diagnostic or therapeutic procedures.

As mentioned above in the Background of the Invention, relatively expensive platinum alloy materials were used in the past as combination electrodes and radiopaque markers. For the present invention, less expensive materials are preferred that are at least as conductive as platinum alloy materials for the electrodes 34. By way of example, the catheter assembly 20 may be a therapeutic instrument for use in an ablation procedure, wherein the distal portion electrodes 34 would be configured for creating lesion patterns in internal body tissue. By way of alternate example, the catheter assembly 20 may be a diagnostic instrument for use in detecting the location of aberrant electrical pathways in a patient's myocardial tissue, wherein the distal portion electrodes 34 would be configured for detecting electrical activity in body tissue. By way of still further example, the electrodes 34 may be configured to be multi-functional so as to perform both of the above-described therapeutic and diagnostic procedures. The handle 22 encloses a steering mechanism 36 for the distal end 32 of the catheter 24. Left and right steering wires (not shown) extend through the catheter body 24 to interconnect the steering mechanism 36 with the distal end 32. The steering mechanism 36 includes a steering lever 38. Rotation of the steering lever 38 to the left pulls on the left steering wire, causing the distal end 32 to bend to the left. Rotation of the steering lever 38 to the right pulls on the right steering wire, causing the distal end 32 to bend to the right. In use, a physician holds the catheter handle 22 and introduces the catheter 24 through a body passageway such as a main vein or artery into the interior region of the body that is to be diagnosed and/or treated. The physician then further steers the distal portion 30 of the catheter 24 by means of the steering lever 38 to place the electrodes 34 into contact with the tissue that is targeted for the therapeutic and/or diagnostic procedure.

With reference to FIGS. 3A-3C, a marker assembly 40 constructed in accordance with a preferred embodiment of the invention will now be described. A catheter tip assembly 42 is adapted to be affixed to the distal end 32 of the catheter 24, e.g., by an adhesive or thermal bonding process .

The tip assembly 42 includes a hemispherical tip 44 having a flat, rear face 46. The hemispherical tip 44 has a diameter similar to the outer diameter of the catheter 24 and ring electrodes 34. A stem-like support 48 extends from the rear face 46 of the hemispherical tip 44. The tip assembly 42 is preferably made of the same highly flexible, low durometer polymer material as the catheter 24, i.e., Pebax or Pellethane, to promote attachment of the tip assembly 42 to the catheter 24. The marker assembly 40 includes multiple markers 50 circumferentially printed, painted, or otherwise placed on the support 48. In a presently preferred embodiment, the markers 50 are made of a printed radiopaque ink or paint such as tungsten ink. The placement distances of the markers 50, when measured from the rear face 46 of the tip assembly 42, is the same as the placement distances of the respective electrodes 34 from the distal end 32 of the catheter 24. The thickness of the markers 50 depends on the material used but is typically .003 to .005 inches to provided visualization under fluoroscopy.

During assembly of the marker assembly 40, the catheter tip assembly 42 is located outside of the distal portion 30 of the catheter 24 and the markers 50 are printed or painted on the support 48. The catheter tip assembly 42 is then put into the distal portion 30 of the catheter 24 by sliding the support 48 of the tip assembly 42 into the catheter 24, until the flat rear face 46 of the hemispherical tip 44 contacts the distal end 32. This assembly aligns the radiopaque markers 50 with the electrodes 34 on the catheter 24.

The tip assembly 42 and the distal end 32 of the catheter 24 are then bonded together by an adhesive 52, such as cyanoacrylate . Other well known adhesives or solvent bonds well known in the medical device industry may be used. The adhesive 52 seals the radiopaque markers 50 off from the outside of the catheter 24, allowing for relatively inexpensive, non-biocompatible materials to be used for the markers 50. Alternately, the tip assembly 42 may be thermally bonded to the catheter 24, e.g., by heating the attached assembly to a temperature greater than the melting temperature of the polymer material, while compressing the tip assembly 42 into the catheter distal end 32. With reference to FIGS. 4A and 4B, a marker assembly 60 constructed in accordance with another preferred embodiment of the invention will now be described. The marker assembly 60 includes crimpable radiopaque marker rings 62 that are carried by a catheter tip assembly 64 such as catheter tip assembly 42 previously described in association with FIGS. 3A-3C. The catheter tip assembly 64 includes a hemispherical tip 66 and a support 68. The support 68 preferably comprises one or more wires attached to the hemispherical tip 66. The markers 62 are applied to the tip assembly 64 by sliding them over the support 68, e.g., wire or wires, and crimping the markers 62 to the support 68. The tip assembly 64 is bonded to the distal end 32 of the catheter 24 in the manner described above, sealing in the markers 62. The markers 62 are preferably made of relatively inexpensive radiopaque materials such as tungsten, lead, mercury, tantalum, or alloys of these materials whose biocompatibility is either unknown or known as a hazard, but which have high radiopacity. Alternately, more expensive, biocompatible radiopaque materials, such as platinum or gold, may be used. The thickness of the markers 62 is .0015 to .005 inches.

Relatively inexpensive radiopaque materials that are normally not biocompatible can be used in the present invention making the catheter assembly less expensive to manufacture, because the markers are encased and sealed in the body of the catheter 24.

With reference to FIGS. 5A and 5B, a marker assembly 80 constructed in accordance with another preferred embodiment of the invention will now be described. The marker assembly 80 includes radiopaque markers 82 constructed of split rings or "C" rings that are carried by a catheter tip assembly 84 such as catheter tip assembly 60 previously described in association with FIGS. 4A and 4B. The catheter tip assembly 84 includes a hemispherical tip 86 and a support 88. Similar to the support 68 described in conjunction with FIGS. 4A and 4B, the support 68 may comprise one or more wires 90. The markers 82 are applied to the tip assembly 84 by applying an "opening pressure" to the markers 82, sliding the markers 82 over the support 88, while maintaining the opening pressure on the markers 82. The "opening pressure" on the markers 82 is then released, so that the rings 82 are retained onto the support 68 at locations corresponding to the electrodes 34 on the catheter 24.

With reference to FIGS. 6A and 6B, a marker assembly 100 constructed in accordance with another preferred embodiment of the invention will now be described. The marker assembly 100 includes a distal tip assembly 102, a tube 104, and one or more markers 106 and spacers 108 carried by the tube.

The distal tip assembly 102 has a hemispherical tip 110 and a short, reduced-diameter stem 112 that extends rearward from a rear face 114 of the tip 110. The markers 106 are short pieces of fine wire made of a radiopaque material such as gold, lead, platinum, or the like. The markers 106 have a length that corresponds to the length of the electrodes 34 and a diameter that is approximately the same as the diameter of the stem 112. The spacers 108 are short pieces of wire or beading made of a non-radiopaque material such as Teflon, polyethylene, or similar polymer. The spacers 108 have a length that corresponds to the distance between the electrodes 34 and, like the markers 106, a diameter that is approximately the same as the diameter of the stem 112.

The tube 104 is preferably a thin-wall shrink tubing having a recovered inner diameter that is smaller than the collective diameter of the stem 112, markers 106, spacers 108. The tube preferably has a length that is slightly longer than the length from the most proximal electrode 34 to the most distal electrode 34. The shrink tube 104 is preferably made of a material that can be adhered to the inner wall of the catheter 24.

The marker assembly 100 is manufactured by placing a distal end of the shrink tube 104 on the stem 112 of the tip 110, placing the markers 106 and spacers 108 into the shrink tube 104, and then adjusting the position of the markers 106 and spacers 108 in the tube 104 so that they correspond to the placement of the electrodes 34 on the catheter 24. The shrink tube 104 is then placed into a heat source, causing the tube 104 to shrink in diameter down onto the stem 112 of the tip 110 and the markers 106 and spacers 108. The marker assembly 100 is then slid into the catheter 24. An affixant such as cyanoacrylate may be used to affix the outer surface of the tube 104 to the inner surface of the catheter 24.

With reference to FIG. 7, a marker assembly 120 constructed in accordance with an additional preferred embodiment of the invention is shown. The marker assembly 120 is similar to the marker assembly 100 immediately described above with respect to FIGS. 6A-6C, except the marker assembly 120 includes a distal tip assembly 122 having a barbed portion 124, and a non-shrink tube 126 to carry markers 128 and spacers 130. The barbed portion 124 is used to hold the distal end of the tube 126 to the distal tip assembly 122 and an adhesive 132 such as cyanoacrylate is used to contain the markers 128 and spacers 130 in the tube 126 at the proximal end of the tube 126.

The marker assemblies 100, 120 provide better radiographic imaging than the other embodiments of the invention because the markers 106, 128, respectively, are solid pieces of radiographic material. With reference to FIGS. 8A and 8C, an alternate distal tip assembly 140 is shown. The distal tip assembly 140 is similar to the distal tip assembly 102 described above in conjunction with FIGS. 6A-6C, except it includes a reduced- diameter cylindrical portion 142 that has a diameter that approximately corresponds in dimension to the inner diameter of the distal end 32 of the catheter 24 (See FIG. 8C) . The reduced-diameter cylindrical portion 142 fits snugly within the distal end 32 of the catheter 24 and is affixed thereto with a solvent bond or affixant such as cyanoacrylate. The snug fit and bond of the reduced-diameter portion 142 of the distal tip assembly 140 with the distal end 32 of the catheter 24 eliminates the need to affix the tubing of the marker assembly to the inner surface of the catheter 24. This is beneficial because most types of shrink tubing are made of materials that are difficult to bond to other materials . With reference to FIG. 8B, an alternate distal tip assembly 150 will now be described. The distal tip assembly 150 is similar to the distal tip assembly 140 shown in FIG. 8A in that it includes a reduced-diameter portion 152 and similar to the distal tip assembly 122 shown in FIG. 7 in that it includes a barbed portion 154.

With reference to FIG. 9, a marker assembly 160 constructed in accordance with another preferred embodiment of the invention is shown. The marker assembly 160 includes a plurality of radiopaque markers 162 constructed of expandable rings. The markers 162 include a cut-out 164 along their length. The markers 162 have an outer diameter that is less than the inner diameter of the catheter 24. The ring markers 162 are applied by sliding them into the catheter 24, in position under the electrodes 34, and expanding them into the catheter 24 with forceps, or a similar device.

Electrode wires 166 extend through the cut-outs 164 for connection to the electrodes 34. A catheter tip 168 is affixed to the distal end 32 of the catheter 24 and seals off the inside of the catheter 24 in the manner described above .

With reference to FIG. 10, a marker assembly 170 constructed in accordance with a further preferred embodiment of the invention is shown. The marker assembly 170 includes one or more markers 172 made of a radiopaque ink or paint such as tungsten ink applied to the outer surface of the catheter _.24. The markers 172 are shelled over or encased with an electrode 174 made of a non- radiopaque conductive ink such as silver or silver chloride ink. The electrodes 174 act as seals to contain the material of the radiopaque markers 172. Together, the markers 172 and electrodes 174 form a composite coating 176. Referring to FIGS. 11 and 12, an alternate preferred distal end electrode assembly 180 for catheter includes two sets of metal electrode bands 184A-B and 186A-B, respectively carried along the outer circumference of the catheter tube 24. As best seen in FIG. 12, the most distal electrode band 186B is retained on the catheter 24 by a dome-shaped tip section 188. In particular, the outer diameter of the distal edge 182 of tip section 188 is preferably at least equal or slightly greater than the respective outer diameter of the electrode band 186B, thereby preventing the electrode band 186B from becoming detached from the catheter 24.

As alternately depicted in FIGS. 13 and 14, there are two presently preferred methods for assembling the distal tip assembly 180.

Referring to FIG. 13, the respective electrode bands 184A-B (not shown in FIG. 13) and 186A-B are secured over the outer circumference of the catheter 24, with the most distal band 186B situated proximate the very distal end 190 of the catheter 24. By way of example, the electrode bands 184A-B and 186A-B are placed on the distal end of the catheter 24 as follows:

The distal end of the catheter 24 is stretched to decrease its outer diameter. The respective ring electrodes 184A-B and 186A-B are then positioned along the catheter 24, while the reduced outer diameter is maintained. The catheter 24 is then released, such that its outer diameter recovers to its non-stretched diameter, resulting in a mechanical interference fit of the respective electrode bands 184A-B and 186A-B. The remaining distal end portion of the catheter 24 is then removed, except for a very small margin, e.g., .015" to .025" amount of polymer tubing left extending beyond the outermost ring electrode 186B, in order to maintain the interference fit of electrode band 186B. A stem portion 189 of a mushroom-shaped tip section 188' made of the same polymer as catheter 24 is then inserted into the distal end 190 of the catheter 24, with a proximal edge 182' of the tip section 188' retaining the electrode band 186B in place. In a manner described above in conjunction with FIGS. 3A-C, the tip section 188' is secured to the catheter tubing by either adhesive or thermal bonding.

Referring to FIG 14, the respective electrode bands 186A and 186B are secured over the outer circumference of the catheter 24 in a manner similar to that described above in conjunction with FIG. 13, except that a longer end portion 194 of the catheter tubing 24 (approximately .125" in a presently preferred embodiment) is left extending beyond the most distal electrode band 186B. In accordance with this aspect of the invention, the end portion 194 is then molded into the sealed dome-shaped tip section 188 (FIGS. 11-12) by pressing portion 194 against into a semicircular face 202 of a heated die 200 (as depicted by arrow 196) .

Referring to FIGS. 15-16, a still further preferred catheter assembly 210 includes an elongate polymer catheter 212 disposed in a guide sheath 214. A distal end 213 of catheter 212 extends from a distal opening 215 of the guide sheath 214. The catheter distal end 213 carries a plurality of electrode bands 216 and a polymer distal tip 218. A pullwire 220 is attached at one end to the distal tip 218 of the catheter 212, with its other end (not shown) extending through the guide sheath 214, along with the catheter 212. In this manner, the pullwire 220 may be pulled by a user, i.e., from a proximal opening of the guidesheath 214 (not shown) , to thereby cause the catheter end 213 to bend, as illustrated in FIG. 15.

As best seen in FIG. 16, the pullwire 220 is attached to the polymer distal tip 218 of the catheter end 213 through an opening 222 having a smooth, tapered rounded edge 224. In this manner, as the pullwire 220 is pulled through the sheath 214, thereby deflecting the polymer tip 218, the end of the pullwire 220 proximate opening 222 confirms along the tapered edge 224, with the relative softness of the polymer tip 218 absorbing fatigue due to the deflection force.

Although the invention has been described in terms of preferred embodiments, other embodiments apparent to those of ordinary skill in the art are also within the scope of this invention.

Accordingly, the scope of this invention is intended to be defined only by the claims that follow.

Claims

Claims :

1. A medical device comprising: an elongate body having an external surface; a plurality of electrodes carried by the elongate body; and a corresponding plurality of radiopaque markers carried by the catheter body, each marker underlying a respective electrode.

2. The medical device of claim 1, wherein the radiopaque markers are sealed off from the external surface of the elongate body.

3. The medical device of claim 1, wherein the elongate body includes a lumen, the medical device further comprising a support member extending longitudinally within the lumen and carrying the plurality of markers.

4. The medical device of claim 3, wherein the markers each comprise a radiopaque ink disposed on the support member.

5. The medical device of claim 3, wherein the markers comprise radiopaque rings.

6. The medical device of claim 5, wherein the support member further carries a plurality of non-radiopaque spacers, disposed between respective markers, each spacer having a length approximately equivalent to the distance between corresponding electrodes disposed over the respective markers.

7. The medical device of claim 6, wherein the support member comprises a flexible tube that carries the respective radiopaque markers and non-radiopaque spacers therein.

8. The medical device of claim 7, wherein the tube is made of a shrinkable material.

9. The medical device of claim 7, wherein^' the tube is made of a polymer.

10. The medical device of claim 1, wherein the markers comprise bands of radiopaque material applied to the external surface of the elongate body.

11. The medical device of claim 1, wherein the invasive medical device is a catheter.

12. An invasive catheter, comprising: a catheter body; a plurality of electrodes carried by the catheter body; and a corresponding plurality of radiopaque markers carried by the catheter body, each encased by a respective electrode.

13. The catheter of claim 12, wherein the electrodes comprise conductive ink.

14. The catheter assembly of claim 12, wherein the radiopaque markers comprise radiopaque material printed on the catheter body.