SURFACE COATINGS FOR CATHETERS,
DIRECT CONTACTING DIAGNOSTIC AND
THERAPEUTIC DEVICES
CROSS REFERENCE TO RELATED
APPLICATIONS
This application is a continuation of application Ser. No. 08/879,343, filed Jun. 20,1997, now U.S. Pat. No. 5,991,650 of U.S. patent applications Ser. Nos. 08/545,105 filed Oct. 19, 1995, now U.S. Pat. No. 6,001,093 which is a continu- 10 ation of Ser. No. 08/138,142, filed Oct. 15, 1993, now abandoned, entitled "Systems and Methods for Creating Long, Thin Lesions in Body Tissue; U.S. patent application Ser. No. 08/763,169, filed Dec. 10, 1996 now U. S. Pat. No. 6,106,822 which is a continuation of Ser. No. 08/287,192, is filed Aug. 8, 1994, now abandoned, entitled "Systems and Methods for Forming Elongated Lesion Patters in Body Tissue using Straight or Curvilinear Electrode Elements; U.S. patent application Ser. No. 08/803,431, filed Feb. 20, 1997, now U.S. Pat. No. 6,032,061, entitled "Catheter 20 Carrying and Electrode and Methods of Assemblies"; U.S. patent application Ser. No. 08/747,811, filed Nov. 14, 1996 now U.S. Pat. No. 5,871,443 which is a continuation of Ser. No. 08/636,174, filed Apr. 22, 1996 abandoned, which is a divisional of U.S. patent application Ser. No. 08/168,476, 25 filed Dec. 16,1993 now U.S. Pat. No. 5,509,419, issued Apr. 23,1996, filed Dec. 16,1993 entitled "Cardiac Mapping and Ablation Systems"; U.S. patent application Ser. No. 08/630, 719 filed Apr. 8, 1996, claiming priority of U.S. provisional application Ser. No. 60/010,354, filed Jan. 19, 1996, entitled 30 "Expandable-Collapsible Electrode Structures with Electrically Conductive Walls"; U.S. patent application Ser. No. 08/631,356, filed Apr. 12, 1996, now U.S. Pat. No. 5,840, 076, claiming priority of U.S. Provisional Patent Application Ser. No. 60/010,225, filed Jan. 19, 1996, entitled "Tissue 35 Heating and Ablation Systems and Methods Using Electrode Structures with Distally Oriented Porous Lesions"; and U.S. patent application Ser. No. 08/631,252, filed Apr. 12, 1996, now U.S. Pat. No. 5,797,903 which claims priority of U.S. Provisional Application Ser. No. 60/010,225, filed Jan. 19, 40 1996, entitled "Tissue Heating and Ablation Systems and Methods Using Porous Electrode Structures with Electrically Conductive Surfaces".
BACKGROUND OF THE INVENTION
1. Field of the Invention The present invention relates generally to catheter distal
end assemblies, and more particularly to surface coatings for such assemblies.
2. Description of the Prior Art 50 Conventionally, catheter components such as electrodes
and thermocouples are placed onto electrophysiology catheters manually. The electrodes are then held in position and masked with adhesive. This process is very time consuming and thus quite expensive. An undesirable feature of such a 55 catheter-electrode construction for ablation is that it has high electrode edge effects that are attributed to delivering RF energy to an electrode having a sharp transition between the conductive electrode and the insulating catheter body. A further limitation in the prior art is that toxic materials such 60 as those composed of silver and lead, cannot be used where direct contact with the patient's tissues and bodily fluids occur. Additionally, many prior art catheter devices are formed with small openings and crevices which permit the ingress and retention of bodily fluids and tissue. There is 65 therefore a need for a surface coating for catheter distal end assemblies that solves these problems.
SUMMARY OF THE INVENTION
A catheter of the present invention includes a distal end assembly having an external surface coating. Where the distal end assembly includes electrodes or other electrical components, the coating is preferably electrically conductive. In the preferred embodiment, such an electrically conductive coating is formed from a material comprising regenerated cellulose, although other materials such as a hydrogel or a plastic having an electrically conductive component are utilizable. Where the distal end assembly includes optical or ultrasonic components, the preferred surface coating is substantially transparent to optical and ultrasonic transmissions therefrom. A regenerated cellulose coating is suitable for both optical and ultrasonic distal end assemblies.
The robustness of the surface coating permits the manufacture and utilization of electrode configurations that are formed on a non-conductive base member by processes such as pad printing, vapor deposition, ion beam assisted deposition, electroplating and other printed circuit manufacturing processes. Additionally, because the surface coating produces a smooth outer surface to the distal end assembly, lead wires and temperature sensing devices can be bonded to the exterior surface of electrodes and then coated to produce a smooth outer surface; thus providing a simple, inexpensive manufacturing method for the attachment of such components to the electrodes.
It is an advantage of the present invention that catheter distal end assemblies can be more efficiently manufactured.
It is another advantage of the present invention that catheter distal end assemblies can be more inexpensively manufactured.
It is a further advantage of the present invention that electrode configurations can be printed or deposited upon the surface of a catheter end assembly and withstand the mechanical and chemical stresses of usage without degradation.
It is yet another advantage of the present invention that catheter distal end assemblies having a surface coating are sealed against ingress of contaminating bodily fluids.
These and other features and advantages of the present invention will become obvious to those of ordinary skill in the art upon reading the following detailed description.
IN THE DRAWINGS
FIG. 1 is a perspective view of a catheter device having a distal end assembly having a surface coating thereon;
FIG. 2 is an enlarged perspective view the distal end assembly of FIG. 1;
FIG. 3 is a further enlarged view of the distal end assembly depicted in FIG. 2;
FIG. 4 is a cross-sectional view taken along lines 4—4 of FIG. 3;
FIG. 5 is a perspective view of a catheter distal end assembly having a surface coating having a variable thickness;
FIG. 6 is a perspective view of a regenerated cellulose casing for use as a surface coating for a catheter distal end assembly;
FIG. 7 is a perspective view of a catheter distal end assembly formed with a skive for the disposition of electrical interconnections, and having a surface coating;
FIG. 8 is a cross-sectional view taken along lines 8—8 of FIG. 7;
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FIG. 9 is a perspective view of another catheter distal end assembly that is covered with a surface coating;
FIG. 10 is a perspective view of a further catheter distal end assembly that is covered with a surface coating;
FIG. 11 is a perspective view of another catheter distal end assembly having a surface coating;
FIG. 12 is a perspective view of a further catheter distal end assembly that is covered with a surface coating.;
FIG. 13 is a perspective view of yet another catheter distal end assembly having serpentine shaped electrodes that are covered with a surface coating;
FIG. 14 is a perspective view of another catheter distal end assembly having printed circuit electrodes and lead lines that is covered with a surface coating;
FIG. 15 is a perspective view of a balloon catheter device having a surface coating;
FIG. 16 is a elevational view of a catheter distal end assembly having a basket electrode array that is covered with a surface coating;
FIG. 17 is an enlarged view of one of the splines of the basket electrode array depicted in FIG. 16;
FIG. 18 depicts an optical imaging probe having a surface coating thereon; and
FIG. 19 depicts an ultrasonic imaging probe having a surface coating thereon.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS
The present invention includes the use of a coating forming an external surface for catheters, direct contacting medical devices, and similar instruments, as well as a surface coating over components of such catheters and similar instruments. A particular application of the present invention involves using regenerated cellulose as a coating material for forming an external surface for catheter devices used for pacing, recording, and delivering RF energy. These catheter devices include devices that are capable of creating long, thin lesions of different curvilinear shapes, and devices that are capable of creating large, deep lesion patterns in heart tissue. Such devices are described in U.S. Pat. No. 5,582,609, issued Dec. 12, 1996, entitled: "Systems and Methods for Forming Large Lesions in Body Tissue Using Curvilinear Electrode Elements", U.S. patent application Ser. No. 08,763,169, entitled: "Systems and Methods for Forming Elongated Lesion Patterns in Body Tissue Using Straight or Curvilinear Electrode Elements"; U.S. patent application Ser. No. 08/545,105, entitled: "Systems and Methods for Creating Long, Thin Lesions in Body Tissue", the disclosures of each of these references being incorporated herein by reference as thought set forth in full. It is also to be appreciated that the invention is applicable for use in other tissue ablation applications. For example, various aspects of the invention have application in procedures for ablating tissue in the prostate, brain, gall bladder, uterus, and other regions of the body, using systems that are not necessarily catheter-based.
The regenerated cellulose coating acts as a mechanical barrier between the catheter components, such as electrodes, preventing ingress of blood cells, infectious agents, such as viruses and bacteria, and large biological molecules such as proteins, while providing electrical contact to the human body: As a result the electrodes can now be made using more efficient processes (such as pad printing) that have been previously rejected due to lack of robustness when directly exposed to bodily tissues on a catheter surface. The re gen
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erated cellulose coating also acts as a biocompatible barrier between the catheter components and the human body, whereby the components can now be made from materials that are somewhat toxic (such as silver or copper), because
5 the diffusional distance to tissues is increased substantially, and because a lower percentage of the metallic surface is exposed (both directly and indirectly) to the tissue. In addition, coating electrodes with regenerated cellulose decreases the effect of convective cooling on the electrode.
10 That is, since regenerated cellulose is a poor thermal conductor when compared to metal, the effect of convective cooling by blood flowing past the regenerated cellulose coated electrodes is diminished. This provides better control for the lesion-generating process because the hottest tissue
15 temperature is closer to the ablation electrode. Furthermore, the regenerated cellulose coating decreases the edge effects attributed to delivering RF energy to an electrode having a sharp transition between the conductive electrode and insulating catheter tubing. The current density along the elec
20 trode and power density within tissue are more uniform, which reduces the incidence and severity of char and/or coagulum formation. The more uniform current density along the axis of the catheter also results in a more uniform temperature distribution at the electrode, which decreases
25 the requirement for precise placements of the temperature sensors at the ablation electrodes. Furthermore, by coating a catheter with regenerated cellulose to create the outer catheter surface, less labor-intensive methods to form electrodes and for bonding wires to electrode surfaces can be used.
30 In the coating process of the present invention a device, such as a catheter distal assembly with components such as electrodes and wire conductors fixed in place, is coated with a viscose solution. In the preferred embodiment the viscose solution is cellulose xanthate, which is a form of solubilized
35 cellulose derivative that is dissolved in a sodium hydroxide solution. The viscose solution is dip-coated onto the distal end assembly, which includes the electrodes, signal wires, temperature sensors and distal tubing. The catheter coated with the cellulose xanthate derivative is then regenerated by
40 contacting it with an acid, such as sulfuric acid, which converts the xanthate back into the cellulose structure. The term regenerated cellulose refers to cellulose which has been converted from a solubilized cellulose derivative back into a pure cellulose structure. This regeneration process creates
45 large enough micro size pores in the coating allowing ionic transport yet small enough to prevent ingress of blood cells, infectious agents, such as viruses and bacteria, and large biological molecules such as proteins.
Once the cellulose is regenerated, it is rinsed with water
50 to remove acid residuals and sulfur compounds. An oxidizing agent (bleach, etc.) may be added to the rinse water to accelerate the removal of sulfur compounds. After the cellulose is regenerated, it is fully cured in an environmental chamber at a low humidity. Thereafter, it is preferable to
55 make the regenerated cellulose flexible when dry, and to do so moisture is reintroduced into the cellulose coating material by setting the environmental chamber to a higher humidity. Alternatively, a small quantity of a material such as glycerol may be applied to the coating, and the hydro
60 scopic nature of the glycerol will hydrate the cellulose coating to create sufficient flexibility. An overall thickness range for operable regenerated cellulose coatings is from 0.001 inches to 0.015 inches, with a preferable thickness range being from 0.001 inches to 0.003 inches; a preferred
65 thickness being approximately 0.002 inches.
Materials other than regenerated cellulose that are mechanically robust and that have suitable characteristics
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