Method Of Making A Catheter

Abstract

Electro-conductive catheters and methods of manufacture thereof.

Parent Case Text

This is a division of application Ser. No. 718,434, filed Apr. 3, 1968, now U.S. Pat. No. 3,590,822.

This invention relates to catheters and, more particularly, to electro-conductive catheters and to methods of manufacture thereof.

It is a primary object of the present invention to provide novel electro-conductive catheters and novel methods of manufacture thereof.

Another primary object of the present invention, in addition to each of the foregoing objects, is the provision of such novel catheters particularly adapted for use, for example, as a pacing electrode.

Yet another primary object of the present invention, in addition to each of the foregoing objects, is the provision of such catheters comprising an electrically conductive core and electrically insulating sheath.

Still another primary object of the present invention, in addition to each of the foregoing, is the provision of such catheters wherein the core comprises a wire cable and the sheath comprises a low friction fluid impervious, easily cleaned and non-toxic substance.

Another and yet still further primary object of the present invention, in addition to each of the foregoing objects, is the provision of such catheters wherein the sheath comprises a thermoplastic material.

A still further primary object of the present invention, in addition to each of the foregoing, is the provision of such catheters further comprising an electrode tip having a smoothly rounded nose securely and firmly connected with the core and extending outwardly of the sheath.

Another and yet still further primary object of the present invention, in addition to each of the foregoing, is the provision of novel methods of forming such a tip and of connecting such a tip with such a core.

In addition to each of the foregoing, it is also a primary object of the present invention to provide such catheters wherein the sheath is securely bonded with the electrode and adjacent core at the distal end and with the core at the proximal end.

Yet further, still another primary object of the present invention, in addition to each of the foregoing, is the provision of novel methods of bonding the sheath to the core and electrode.

Another and still further primary object of the present invention, in addition to each of the foregoing, is the provision of such catheters wherein the core is sealed at both the distal and proximal ends of the sheath to preclude passage of fluids therethrough.

A still further primary object of the present invention, in addition to each of the foregoing, is the provision of such catheters wherein the distal and proximal end portions of the sheath are caused to flow between to seal and bond with the individual core strands at the distal and proximal ends.

Yet another primary object of the present invention, in addition to each of the foregoing, is the provision of novel methods of bonding the sheath to the core at the distal and proximal ends.

The invention resides in the combination, construction, arrangement and disposition of the various component parts and elements incorporated in improved catheters constructed in accordance with the principles of this invention and in methods of manufacture thereof. The present invention will be better understood and objects and important features other than those specifically enumerated above will become apparent when consideration is given to the following details and description, which when taken in conjunction with the annexed drawing describes, discloses, illustrates and shows a preferred embodiment or modification of the present invention and what is presently considered and believed to be the best mode of practicing the principles thereof. Other embodiments or modifications may be suggested to those having the benefit of the teachings herein, and such other embodiments or modifications are intended to be reserved especially as they fall within the scope and spirit of the subjoined claims.

Description

ordance with the principles of this invention and in methods of manufacture thereof. The present invention will be better understood and objects and important features other than those specifically enumerated above will become apparent when consideration is given to the following details and description, which when taken in conjunction with the annexed drawing describes, discloses, illustrates and shows a preferred embodiment or modification of the present invention and what is presently considered and believed to be the best mode of practicing the principles thereof. Other embodiments or modifications may be suggested to those having the benefit of the teachings herein, and such other embodiments or modifications are intended to be reserved especially as they fall within the scope and spirit of the subjoined claims.

IN THE DRAWING

FIG. 1 is a process flow chart depicting the various steps which may be utilized in producing catheters in accordance with the present invention;

FIG. 2 is an enlarged illustration of an end portion of a core cable and an electrode for use therewith showing one step of the method;

FIG. 3 is a view similar to FIG. 2 illustrating a succeeding step in the method;

FIG. 4 is a view similar to the preceding figures illustrating a yet further step in the method; and

FIG. 5 is a view similar to the preceding illustrating a yet still further step in the method.

With reference now to the drawing, catheters constructed in accordance with the principles of the present invention may comprise an electrically conductive elongate and bodily flexible core 10, an electrically conductive electrode 12 electrically and mechanically connected therewith adjacent one end portion thereof and an electrically non-conductive and chemically substantially inert sheath 14 extending substantially entirely of the core 10. The core 10, electrode 12 and sheath 14 accordingly define a catheter constructed in accordance with the principles of the present invention and designated generally by the reference character 16.

Catheters constructed in accordance with the present invention are particularly suitable for use as cardiac pacing electrodes. Hence, the catheters are intended to be inserted through the veinous system into the heart to provide electrical impulses directly thereto. To be suitable for such utilization, there are several criteria which must be fulfilled. The catheter must be of sufficient flexibility as to be capable of easy passage through the veinous system. The outer surface and the nose portion of the catheter must be sufficiently smooth as to preclude any chance of trauma or injury to the patient's veins or heart. The catheter must be capable of being sterilized. Any possibility of breakage or separation of the tip or electrode from the remainder of the catheter must be minimized. The catheter must be substantially impervious to body or other fluids to prevent any infection or contamination. For ease in passing the catheter through the veinous system and positioning the tip or electrode portion thereof at the desired location, the catheter should be capable of being easily steered from the proximal end. This steering may be accomplished by providing a slight curvature to the tip portion and constructing the catheter to enable the smooth transmission of torque therethrough to enable a rotation of the proximal end to direct the curved portion in a desired direction.

The core 10 may be of either stranded or solid construction. However, in order to provide the requisite flexibility and torque response, the core 10 preferably comprises a plurality of wire strands 18 twisted or laid together to define a wire rope or cable. The strands 18 may also be woven or braided together. However, it has been found that a twisted wire rope type of construction utilizing 21 wires twisted in regular lay 7 .times. 3 is especially suitable. By regular lay 7 .times. 3 is meant that the rope comprises seven strands twisted with a righthand lay, each of the seven strands comprising three wires twisted together in a lefthand lay. It has been found that such a wire rope fabricated of brass coated stainless steel wire and having an overall diameter of approximately 0.023 inches forms a suitable core.

The electrode 12 may similarly be fabricated of substantially any material and may, for example, comprise a stainless steel sleeve approximately 3/16 inch long having a generally axial bore 20 of slightly greater diameter than that of the wire rope or core 10. The electrode 12 may be assembled with the wire rope or core 10 by inserting the distal end portion of the wire rope or core 10 through the bore 20 of the electrode 12 to extend outwardly thereof a distance slightly greater than the length of the electrode 12. Then, the wires and strands of the wire rope or core 10 may be spread apart, untwisted, and separated to flair outwardly, as illustrated in FIG. 2. The electrode 12 may then be moved relative to the wire rope or core 10 to a position adjacent the distal end portion thereof so as to overlie the spread apart wires or strands thereof, as illustrated in FIG. 3. The resilience of the wires of the rope or core 10 after having been spread apart and then positioned or disposed within the electrode 12 will engage the bore 20 thereof while remaining somewhat separated one from the other. The electrode 12 and associated distal end portion of the wire rope or core 10 may then be firmly and securely electrically and mechanically interconnected, as by silver solder. The solder may be applied in any desired manner, as by dipping the electrode and associated distal end portion of the core 10 into a molten pool of solder. The solder will flow between the wires or strands of the rope or core 10 and will firmly bond the wires together and to the electrode 12. The distal end of the electrode 12 will be rounded, as shown, by the solder. It is exceedingly important, in structures of this kind, that there be absolutely no danger of the electrode 12 becoming separated from the wire rope or core 10 since, if it should become separated, it would be left within the circulatory system of the patient where it could cause substantial injury or death. It is believed readily apparent that the strong mechanical interconnection between the wires of the wire rope or core 10 and the electrode 12 formed in accordance with the present invention provides exceptional strength for effectively precluding any danger of accidental separation of the electrode 12 and the wire rope or core 10.

With reference now to FIG. 4, the sheath 14 may then be positioned on the wire rope or core 10 with the distal end thereof generally adjacent to or abutting the electrode 12. The sheath 14 may, for example, comprise a chemically and organically substantially inert material. The sheath 14 may further comprise a material which presents, or is capable of presenting, a substantially smooth, low friction surface. Yet further, the sheath 14 may comprise a material which is substantially non-porous and which may be sterilized, either by heat or chemical action. The sheath 14 may, for example, comprise polyethylene tubing. The sheath 14 may be of slightly lesser longitudinal extent than that of the wire rope or core 10 so that when the sheath 14 is positioned thereon and adjacent the electrode 12, the proximal end of the wire rope or core 10 will project outwardly therefrom a short distance, for example, several centimeters, as illustrated in FIG. 4. The proximal end portion of the wire rope or core 10 may then be dipped or otherwise soldered, to securely bond the wires or strands thereof together.

To enable the transmission of torque along the catheter from the proximal to the distal end, especially to enable easy and accurate steering thereof, and to retain the sheath 14 positioned on the wire rope or core 10, at least the end portions of the sheath 14 should be secured with the wire rope or core 10. While the sheath 14 may be secured with the core or wire rope 10 substantially entirely longitudinally thereof, it is sufficient that the sheath 14 be secured with the wire rope or core 10 at or adjacent the distal and proximal end portions thereof. Moreover, it is preferable that the catheter, and particularly the interstices between the wires and strands of the wire rope or core 10 be sealed to preclude the absorption or transmission of fluids therethrough, especially at the distal end portion, and to reduce or eliminate possible site for bacterial or other organic activity.

The sheath 14 may, for example, comprise a thermoplastic material, such as polyethylene and the end portions thereof may be softened, as by the application of heat thereto, and, while softened caused to move or flow in such a manner as to fill the interstices of the wire rope or core 10 to preclude the passage of fluid therethrough and to secure the end portions of the sheath 14 against movement relative to the wire rope or core 10. Moreover, by appropriately working or forming the softened distal end portion of the sheath 14, it may be caused to flow into intimate contact with the electrode 12 to form a sealed and smooth juncture therewith.

Accordingly, and with reference now to FIG. 5, the distal end portion of the sheath 14 may be heated or otherwise softened and formed or flowed about the proximal end portion of the electrode 12 and through the interstices of the adjacent portion of the wire rope or core 10 by positioning the distal end portion of the catheter 16, that is, the electrode 12 and the adjacent portions of the wire rope or core 10 and sheath 14 within a forming sleeve 22 and applying heat thereto. The sleeve 22 may, for example, comprise a tapered portion 24 adapted to closely fit over the electrode 12 to define therewith a narrow tapered gap extending generally annularly about at least the proximal end portion thereof, as shown. Accordingly, when the distal end portion of the sheath 14 is heated, the plastic material will melt and flow into that tapered annular gap and into and through the portion of the wire rope or core 10 adjacent the electrode 12 which, as heretofore pointed out, comprises loosened or slightly separated wire or strand portions. Hence, the sheath 14 may be securely bonded with the electrode 12 and with the adjacent portion of the wire rope or core 10 while being smoothly tapered by the forming sleeve 22 to enable the transmission of torque, to provide a smooth surface, and to positively seal against contamination or transmission of fluids. The degree of heat applied should be sufficient to cause the plastic material to flow, as heretofore described, without introducing decomposition thereof.

The proximal end portion of the catheter 16 may then be disposed within a similar forming sleeve and heated or otherwise softened to cause the material of the sheath 14 to flow into and through the wire rope or core 10 to bond and seal the proximal end of the catheter 16. A slight curve may then be formed at the distal end of the catheter as an aid in steering the catheter through body passages by inserting the distal end into a curved forming tube and heating the distal end portion and subsequently pulling it while restraining it in such curved configuration, or by substantially any other setting process.

Accordingly, it is believed readily apparent that catheters constructed in accordance with the present invention fulfill the objects hereinabove set forth. Such catheters will be flexible while yet being torque responsive and easily steered. The entire catheter will be smooth and sealed against contamination, the electrode will be rounded, smooth and sealed by the silver solder bath and the proximal end portion of the electrode will be sealed, smooth and tapered by the overlying portion of the sheath formed in the tapered forming sleeve. The sheath will be bonded to the electrode and to the adjacent portion of the wire rope or core. The proximal end portion of the sheath will be similarly bonded to the wire rope or core and the proximal end portion of the wire rope or core will be soldered together to preclude unravelling and to enable ready connection thereof with an appropriate pacing device, or the like. The tip or electrode will be positively and securely associated with the wire rope or core substantially entirely eliminating any danger of the tip or electrode being inadvertently separated therefrom. The entire catheter will be readily sterilizable and present minimal possible contamination sites.

While the invention has been described, disclosed, illustrated and shown in terms of a preferred embodiment or modification which it has assumed in practice, the scope of the invention should not be deemed to be limited by the precise embodiments or modifications herein described, disclosed, illustrated or shown, such other embodiments or modifications as may be suggested to those having the benefit of the teachings herein being intended to be reserved especially as they fall within the scope and breadth of the claims here appended.

Claims

I claim:

1. Method of manufacturing a catheter comprising at least the steps of forming a smooth nose at a distal end of an elongate bodily flexible core of stranded wire, positioning a sheath having distal and proximate end portions over substantially the entire longitudinal extent of the core, and securing the end portions of the sheath with the core to define a bodily flexible catheter adapted to be readily rotated for steering, or the like, wherein said step of securing comprises the step of sealing the interstices between the core wires.

2. Method defined in claim 1 wherein the step of forming comprises positioning a metal sleeve on the distal end portion of the core and soldering the sleeve with the core to define an electrode.

3. Method defined in claim 2 wherein said step of positioning comprises the step of separating the core prior to soldering to enhance bonding between the sleeve and the core.

4. Method defined in claim 3 wherein said step of soldering provides a blunt, rounded end to the electrode, whereby said smooth nose is defined.

5. Method defined in claim 4 wherein said step of securing comprises securing the sheath with the nose.

6. Method defined in claim 2 wherein said step of positioning comprises the steps of passing the distal end portion of the core through the sleeve, spreading the projecting end portion of the core laterally outwardly of the sleeve and withdrawing the core until the distal end is entirely within the sleeve and engaged with the interior thereof.

7. Method defined in claim 2 wherein said step of soldering comprises dip soldering in a molten bath of silver solder.

8. Method defined in claim 2 comprising the additional step of applying solder to a proximal end portion of the core.

9. Method defined in claim 3 wherein the core comprises twisted regular lay wire rope, and said step of positioning comprises at least the step of untwisting.

10. Method defined in claim 1 wherein said sheath comprises a thermoplastic material, and said step of securing comprises the step of heating the end portions of the sheath to enable said end portions to flow around and between the wires of the core at a corresponding end portion thereof to form a bond therewith.

11. Method defined in claim 10 further comprising separating the wires of the core at the end portion to be sealed.

12. Method defined in claim 10 further comprising the additional step of positioning said end portions within a sleeve during such heating and sealing.

13. Method defined in claim 12 further comprising laterally confining the sheath material by said sleeve.