~32~553 TITLE OF THE INVENTION
Guide Wire BACKGROUND OF THE INVENTION
This invention relates to a guide wire which is used to introduce a catheter to the predetermined site of a human body for treatment and examination purposes.
One of advanced medical practices in these years is to introduce a catheter into a blood vessel for the purposes of examination and treatment of heart diseases. In lntroducing the catheter to the predetermined site of a human body, a guide wire is inserted into the catheter until the leading edge of the guide wire slightly projects beyond the leading edge of the catheter so that the guide wire may lead the catheter to the predetermined site.
Several types of catheter guide wires are known in the art includin~ those disclosed in EPA 0141006. These guide wires generally include a core having at least a distal portion thereof formed of a super-elastic alloy and a coating of synthetic resin enclosing the entire core. The guide wlres can efflciently guide the catheter because of the high flexibility and elastic recovery of the distal portion.
Although the above-mentioned guide wires are excellent 2~5 in guidance of the catheter, they are less sensitive to radiographic X-rays. In general, the core is merely coated with synthetic resin. It may be devised to add a radiopaque material to the synthetic resin coating. However, the amount of such radiopaque matexial added is limited because the ;~ 3Q radiopaque material can adversely affect the physical properties of the resin coating. Consequently, the guidie wire as a whole cannot have fully high radiographic sensitivity. In particular, since the distal portion of the metallic core is made slender, the X-ray radiographic 35 ~ sensitivity of the distal portion is undesirably low.
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i 132~553 Nowadays, it is attempted to introduce a catheter into a thinner blood vessel, for example, intracerebral vessels and kidney vessels. To this end, the catheter must be of smaller diameter and the guide wire must be accordingly thinn0r.
Then the guide wire of the type wherein the core is coated with synthetic resin cannot provide suficient radiographic sensitivity particularly at its distal portion. This will make more difficult the operation of introducing the catheter to the predetermined site.
i SUMIIARY OF THE INVENTION
Therefore, an object of the present invention is to provide a novel and improved catheter guide wire of the design that maintains sufficient radiographic sensitivity particularly at its distal portion even when it has a small diameter, facilitating the introduction of the associated catheter to the predetermined site in a blood vessel.
According to the present invention, there is provided a guide wire comprising an elongated core formed o~ a super-elastic alloy including a body portion having high rigidity and a distal portion integrally formed`with the body portion, but having a -smaller diameter and a lower rigidity than said body portion, said distal portion providing a leading edge of the core;
an annular member made of a radiopaque metal secured to the leading edge of said core; and an envelope of synthetic resin enclosing the entirety of said core including the annular member and having a substantially even outer diamet~r.
It is to be noted that the terms radiography and radiographic sensitivity used in the present dlsclosure refer to X-ray radiography and X-ray radiographic sensitivity.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features, and advantages of the present invention will be better understood from the following description taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a longitudinal cross section of a guide wire according to one preferred embodiment of the present invention;
FIG. 2 is an enlarged transverse cross section of the guide wire taken along lines II-II in FIG. 1; and FIG. 3 is a longitudinal cross section of a guide wire according to another preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to FIG. 1, there is illustrated in longitudinal cross section a guide wire according to one preferred embodiment of the present invention. FIG. 2 is an enlarged transverse cross section of the guide wire taken along lines II-II in FIG. 1.
Briefly stated, the guide wire generally designated at 1 according to the present invention comprises an elongated core 2 including a body portion 2a having high rigidity and a distal portion 2b integrally formed with the body portion 2a but having a smaller diameter and lower rigidity than the body portion. The distal portion 2b provides a leading edge of the core. Means for providing radiographic sensitivity 3 is provided at the leading edge of the core 2. An envelope 4 of synthetic resin encloses the entirety of the core 2 including the radiographically sensitive means 3 and has a substantially even outer diameter.
The guide wire of the present invention is described in more detail by referring to FIGS. 1 and 2.
The guide wire 1 has the core 2 including body and distal portions 2a and 2b which are most often formed as a : ~ .
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~324~53 one-piece member from a super-elastic alloy. It is to be noted that the right side as viewed in FIG. 1 is a leading edg~ of the guide wire or core. The body portion 2a i5 usually an elongated tubular member having a suitably chosen diameter. The distal portion 2b is also a tubular member, but is tapered. The diameter of the distal portion 2b is gradually reduced from the connection to the body portion to the tip thereo~. No definite boundary need be present between the body and distal portions, and the distal portion is distinguishable from the body portion in that the distal portion is tapered~ Because of its smallex diameter, the distal portion 2b is less rigid than the body portion. A
core having such a tapered distal portion is improved in operability because the distal portion can be bent more or less when a certain force is applied to the leading edge.
The core 2 is preferably formed of super-elastic alloys, for example, Ti-Ni alloys having 49 58 atom~ of nickel, Cu-Zn alloys having 38.5-41.5~ by weight of Zn, Cu-Zn X alloys having 1-10% by welght of X wherein X is selected from th~ group consisting of Be, Si, Sn, Al and Ga, and Ni-Al alloys having 36-38 atom% of aluminum. The most preferred alloys are Ti-Ni alloys of the above composition~ The body portion 2a of the core 2 preferably has an outer diameter of about 0.10 to about 1.00 mm, more preferably about 0.15 to about 0.40 mm, a length of about 1,000 to about 4,000 mm, more preferably about 1,500 to about 3,000 mm, a buckllng strength (yield stress under load) of about 30 to about 100 kg/mm2 at 22C, more preferably about 40 to about 55 kg/mm2 at 22C, and a restoring stress (yield stress upon unloadlng) of 20 to about 80 kg/mm2 at 22C, more preferably about 30 to about 35 kglmm2 at 22C. ~he distal portion 2b of the core 2 preferably has an outer diameter of about 0.03 to about 0.15 mm, more preferably about 0.05 to about 0.10 mm, a length of about 10 to about 300 mm, more preferably about 50 to about 150 mm, a bending load of about 0.1 to about 10 grams, more . . .
., ,. . ~ , " 1324~53 preferably about 0.3 to about 2.0 grams, and a restoring load of about 0O1 to about 10 grams, preferably about 0.3 to about 2.0 grams.
In the preferred embodiment in which the distal portion 2b has a continuously reducing diameter toward its leading edge, the outer diameter of the distal portion is con-structed as an average of its reducing diameter per its length. The body and distal portions each need not have an equal value of restoring stress over their length, but are rather desired to have restoring stress varied by a heat treatment so that controlled physical properties are available at different diameters. More particularly, the body and distal portions are separately heat treated such that the body portion may have a greater value o`f restoring stress and the distal portion may be more flexible. The core 2 is not limited to a single member and may comprise a plurality of parallel extending or twisted strands insofar as the above-mentioned design and function, that is, a tapered portion connected to a rod-shaped portion and stepwise or continuously varying physical properties are available.
The radiographically sensitlve means is illustrated in FIGS. 1 and 2 as an annular member 3 secured to the leading edge of the core 2. The annular member 3 is a tubular member in the illustrated embodiment. The annular member 3 is preferably formed of a radiopaque metal, for example, gold, platinum, lead, silver, bismuth, and tungsten, most preferably gold. The radiographically sensitive annular member 3 may be secured to the leading edge of the core 2 by any desired methods including mechanical methods like press fitting and bonding methods like brazing or soldering with or without a matchlng metal plated or vapor deposited on the leading edge of the core 2. The matching metal, when plated or vapor deposited on the leading edge of the core 2, is preferably Ni or of the same metal as the particular radiopaque metal used when the core 2 is of a Ti-Ni alloy.
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1~24~3 The matching metal is preferably Zn or of the same metal as the particular radiopaque metal used when the core 2 is of a Cu-Zn or Cu-Zn~X alloy. The matching metal is preferably Ni or of the same metal as the particular radiopaque metal used when the core 2 is of an Ni-Al alloy. The solders used herein are preferably hard solder~ including silver and gold solders.
The radiographically sensitive annular member 3 preferably has an outer diameter of about 0~2Q to about 0.90 mm, more preferably about 0.25 to about 0.40 mm, an inner diameter of about 0.04 to about 0.16 mm, more preferably about 0.06 to about 0.11 mm, and a length of about 1.0 to about 10.0 mm, more preferably about 1.5 to about 4O0 mm.
Another example of the radiographically sensitive annular member 3 is illustrated in FIG. 3. In the embodiment of FIG. 3, the radiographically sensitive annular member 3 is a coil formed by winding a slender filament of a radiopaque metal as defined above around the leading edge of the core 2.
Preferably, a filament having a diameter of about 0.02 to about 0.10 mm i8 wound over an axial distance of about 1.0 to about 10.0 mm, more preferably about 1.5 to about 4.0 mm from the leading edge of the core.
The radiographically sensitive annular member 3 in the form of a coil may be provided by any desirad methods as by directly winding a filament around the core or attaching a pre-wound coil onto the leading portion of the core. The coil is preferably secured to the leading portion of the cor`e, for example, by externally fastening the coil under pres3ure. Alternatively, the radiographically sensitive coil may be secuxed to the leading portion of the core by plating or vapor depositing to the leading portion a matching metal capable of promoting the bond to the coil, winding a filament thereon in coll form or attaching a pre-wound coil therato, and brazing the coil to the matching layer.
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~32~5~3 In addition to the tubular member and coil mentioned above, the radiographically sensitive means 3 may be formed by applying and press bonding a foil of radiopaque metal to the core leading portion, or plating or evaporating a radiopaque metal to the core leading portion to form a radiographically sensitive layer. In this case, the metal foil and deposited layer preferably have a thickness of at least 50 microns.
The synthetic resin envelope 4 covers the entirety of the core 2 including the radiographically sensitive means 3.
The envelope 4 has a substantially even outer diameter from the trailing edge to the leading edge as shown in FIGS. 1 and 3. The outer diameter of the envelope 4 is made substantially equal over its entire length in order that any irregularities on the core 2 including a step formed by the radiographically sensitive means 3 at the leading edge of the core 2 do not appear as the outer contour of the guide wire 1. The envelope 4 may be formed of any desired synthetic resins including polyethylene, polyvinyl chloride, polyester, polypropylene, poIyamide, polyurethane, polystyrene, fluoro-plastics, silicone rubber and othPr various elastomers and composites. Preferably the envelope 4 is sufficiently flexible to allow free bending of the core 2 and provides a smooth continuous outer surface free of ixregularities.
The envelope 4 may be further coated with an anti-coagulant, for example, heparin and urokinase, and an anti-thrombotic agent, for example, silicone rubber, urethane-~ilicone block copolymers such as cardiothane (for example, Abcothane, trade mark, available from Kontron Inc.), and hydroxyethyl methacrylate-styrene copolymers~ It is also recommended to form the envelope 4 from a fluoroplastic resin or another resin capable of providing a low friction surface.
A lubricating fluid such as silicone fluid may be applied to the outer surface of the envelope 4 to reduce the friction of the guide wire. It is preferred to incorporate a radiopaque .
:, , ~ , . ' ~3~4~i~3 material into the resin to form the envelope 4 because it becomes more easy to locate the guide wire during its introduction lnto the vessel. The radiographically sensitive material may be a metal such as Ba, W, Bi, Pb or a compound thereof in fine powder form.
The envelope 4 has a substantially even outer diameter as described above. The term substantially even i~ used to encompass not only a completely even outer diameter, but also an envelope having a slightly tapered leading portion. The use of the envelope 4 having a substantially even outer diameter up to the leading edge minimizes the possible damage of the vascular inner wall by the gulde wire. The outer diameter of the envelope 4 is preferably in the range of from about 0.25 to about 1.04 mm, more preferably from about 0.30 to about 0.64 mm. Accordingly, the envelope 4 has a wall thicknass o~ about 0.03 to about 0.25 mm, preferably about 0.05 to 0.15 mm on the core body portion ~a.
The envelope 4 preferably enclose~ the core 2 in close contact relationship and is secured to the core both at the distal and body portions thereof. Such requirement can be met simply by applying a resin compound to the core, for example, by melt extrusion. It is also possible to form a hollow tube of synthetic resin compound, inserting the core into the tube, and securing the tube to the core at suitable 2S ~ites from the leading edge to the trailing edge by adhesive bonding or fusion welding.
The leadin~ edge of the guide wire 1 or the envelope 4 is preferably rounded to provide a semi-spherical surface as shown in FIGS. 1 and 3 in order to prevent any damage of the vascular wall and to facilitate the operation of the guide wire.
Preferably, the envelope 4 has a lubricating material atta˘hed to the surface thereof. By the lubricating material is meant a material which exhibits lubricating nature when wetted with water. The lubricating materials are typically ' - , .
~3245~3 water-soluble high molecular weight materials and derlvatives thereof. The lubricating materials are attached to the surface of the synthetic resin envelope through covalent or ionic bond~. These lubricating materials are generally chain-structured, non-crosslinked high polymers having a hydrophilic group such as -OH, -CONH2, -COOH, -NH2, -COO-, and -SO3-. ~he lubricating materlals absorb water to exhibit lubricity when wetted with water, that is, contactqd with blood.
The operability of the guide wire 1 is improved by attaching such a lubricating material to the envelope 4 or the outer surface of the guide wire 1 because when the guide wire is received in the catheter, the friction between the catheter inner wall and the guide wire outer wall is minimized to facilitate sliding motion of the guide wire within the catheter.
Exemplary lubricating materiaIs are natural water-soluble h~gh polymers, for exa~ple, starches such as carboxymethyl starch and dialdehyde starch; celluloses such as carboxymethyl cellulose and hydroxyethyl cellulose;
tannins and lignins; polysaccharides such as alginic acid, : gum arabic, heparin, chitin, and chitosan; and proteins such as gelatin and casein. Another class of lubricating material : include~ ~ynthetic water-soluble high polymers, for example, polyvinyl alcohol; polyalkylene oxides such as polyethylene oxide; polyalkylene glycols such as polyethylene glycol;
acrylates such as sodium polyacrylate; maleic anhydride polymer~ such as methyl vinyl ether-maleic anhydride : copolymers, methyl vinyl ether-sodium maleic anhydride, methyl vinyl ether-ammonium maleic anhydride, maleic anhydride-ethyl ester copolymers; phthalates such as poly-(hydroxyethyl phthalate); water-soluble polyesters such as poly(dimethylol propionate); acrylamides such as poly-: acrylamide hydrolyzates, quaternized polyacrylamide; poly vinyl pyrrolidone; polyethylene imine; polyethylene ~ 1324~53 sulfona-te; and water-soluble nylons. Preferred are maleic anhydride polymers, especially maleic anhydride-ethyl ester copolymers.
The derivatives of these water-soluble high polyme~s are not limited to water-soluble ones, but may be of any form so long as they have the above-mentioned water-soluble high polymer as a basic structure. Even insolubilized derivatives may be employed so long as they absorb water to provide lubricity when wetted. Examples include esters, salts, amides, anhydrides, halides, ethers, hydrolyzates, acetals, formals, alkylols, quaternized products, diazos, hydrazides, sulfonates, nitrates, and ion complexes which are obtained by addition, substitution, oxidation, or reduction reaction of the above-mentioned water-soluble high polymers. Also included are polymers crosslinked with substances having more than one reactive functional group such as diazonium group, azide group, isocyanate group, acid chloride group, acid anhydride group, imino carbonate group, amino group, carboxyl group, epoxy group, hydroxyl group, and aldehyde group. Also 20 included are copolymers with vinyl compounds, acrylic acid, methacrylic acid, diene compounds, and maleic anhydride.
In this case, the synthetic resin of the envelope should preferably possess a reactive functional group capable of ionic or covalent bond with the lubricating material, or contain a compound possessing such a reactive functional group, or have such a reactive functional group introduced therein as will be described later.
The lubricating material is bonded with a reactive functlonal group existing or introduced in the synthetic resin to impart lubricity to the surface of the synthetic resin. The lubricating layer thus formed on the surface is long lasting without being dissolved in water. Reference is fir~t made to the lubricating layer attached to the underlying synthetic resin throu~h a covalent bond. The type of lubricating material is not critical, but there can be -. .. , . : .
~3245~3 mentioned as typical examples celluloses, maleic anhydride polymers, acrylamides, polyethylene oxides, and water soluble nylons as mentioned a~ove. Particularly preferred among them are hydroxypropyl cellulose, methyl vinyl ether-maleic anhydride copolymers, polyacrylamide, polyethylene glycol, and water-soluble nylon (AQ-Nylon P-70 manufactured and sold by Toray K.K.). The avera~e molecular weight of the lubricating material is not critical although those having a molecular weight of about 30,000 to 5,000,000 advantageously form a lubricating layer of an appropriate thickness having increased lubricity and a controlled degree of swelling upon water absorption.
The lubricating materials which are attached to the underlying synthetic resin through an ionic bond include polyvinyl pyrrolidonel and carboxylates, sulfonates, and ammonium salts of the foregoing water-soluble high polymer~.
More illustratively, examples of the carboxylates include the sodi~m salt o~ methyl vinyl ether-maleic anhydride, sodium polyacrylate~ polyacrylamide hydrolyzate, sodium carboxy-methyl cellulose, and sodium alginates; examples of the sulEonates include sodium poly(styrene sulfonate) and sodium poly(vinyl sulfonate); and examples of the ammonium salts include the ammonium salt of methyl vinyl ether-maleic anhydride and quaternized polyacrylamide.
The reactive functional groups exlsting or introduced in the synthetic resin are not critical insofar as they are reactive, bondable and crosslinkable with the lubricating material to bind it. Examples of the reactive functional groups include a diazonium group, azide group, isocyanate group, acid chloride group, acid anhydride group, imino carbonate group, amino group, carboxyl group, epoxy group, hydroxyl group, ~nd aldehyde group. Particularly preferred are isocyanate, amino, aldehyde and epoxy groups.
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': . '. : . ~, , ' ~32~5~3 Then, polyurathanes, polyamides and the like are pre~erred as the reactive functional group-bearing synthetic resin.
Other examples of the reactive functional yroup-bearing material are isocyanates such as methylenediisocyanate~ ethylene diisocyanate, toluene diisocyanate, and diphenyl methane diisocyanate, and adducts and prepolymers of these isocyanates with polyols. Also included are low molecular weight polyamines such as ethylene diamine, trimethylene diamine, 1,2-diaminopropane~ and tetramethylene diamine; and high molecular weight polyamines, for example, (i) poly(alkylene polyamines) synthesized from amines and alkylene dihalides or epichlorohydrin, (ii) alkylene imine polymers produced through open-ring polymerization of alkylene imines such as ethylene imine and propylene imine, and (iii) polyamines such as polyvinyl amine and polylysine.
Also included are polyaldehydes such as glutaraldehyde and terephthalaldehyde, and polyepoxides such as ethylene glycol diglycidyl ether.
Examples of the present invention are given below by way of illustration and not by way of limitation.
Example 1 A guide wlre as shown in FIG. 1 was prepared. A
length of core was prepared from a Ti Ni alloy having 56 - atom~ of Ni. The core had an entire length of 1,800 mm, a leadlng edge diam~ter of 0.06 mm, and a trailing edge diameter of 0.25 mm. The leading or distal portion of the core extending 120 mm from the leading edge was tapered toward the leading edge. A rlng of pure gold was prepared which had an inner diameter of 0.07 mm, an outer diameter of 0.3 mm, and an axiaI length of 2.0 mm. The ring was put onto ~35 the leading portion of the core and secured thereto by ' ;` ~
132~5~3 fastening the ring against the core using a clamping tool, providing a radiographically sensitive portion.
A polyurethane composition containing 45% by weight of tungsten fine powder having a particle size of about 3-4 ~m was then extruslon molded on the core over its entire outer surface to form a resin envelope having a substantially even outer diameter. A solution containing 5 r 0% by weight of a maleic anhydride-ethyl ester copolymer in tetrahydrofuran was applied to the polyurethane envelope to bind the maleic anhydride-ethyl ester copolymer to the poly~lrethane, forming a lubricating surface.
The final guide wire had an overall length of about 1,800 mm, an overall diameter of 0.36 mm and its distal portion had a bending load o about 4 grams and a restoring load of about 2 grams.
; An X-ray radiograph of the guide wire as a whole was taken, finding a definite radiographic image of the distal portion.
The opera~ion of the guide wire is described.
Example 2 The guide wire 1 shown in FIG. 1 and prepared in Example 1 was inserted into a catheter (not shown in FIG~ 1) until the leading edge of the guide wire slightly projected beyond the leading edge of the catheter. The catheter having the guide wire received therein was then introduced into a blood vessel so that the leading edge of the guide wire might lead that of the catheter. The guide wire along with the catheter was slowly advanced through the vessel while externally locating the leading edge of them through a radiographic observation. After the leading edge of the catheter had reached the predetermined site along the vessel, the guide wire was withdrawn from the catheter.
1324~3 As described above, the guide wire according to the present invention comprises an elongated core including a body portion having high stiffness and a distal portion integrally formed with the body portion, but having a smaller diameter and lower stlffness than the body portion, means at the leading edge o~ the core for providing radiographic sensitivity, and an envelope of synthetic resin entirely enclosing the core including the radiographically sensitive means and having a substantially even outer diameterO
Particularly the radiographically sensitive means disposed at the leading edge oE the core ensures that the leading edge is visually located through a radiographic observation, facilitating insertion of the guide wire into a catheter and subsequent lntroduction of the catheter into a blood vessel.
When the core is formed of a super-elastic alloy and the distal portion is tapered toward the leading edge, the distal portion will bend a relatively large angle under a certain stress and have recoverable elastic strain. When the leading edge of the guide wire advances past a bend of the vessel, the distal portion undergoes substantial ~lexural deformation under a relatively small load and thus has an improved response. The distal portion will repeakedly bend or de~orm and recover as it passes bends or curves of the ; vessel, without causing damage to the vascular wall. The guide wire has improved sh~pe followability to a sexpentine blood vessel. The guide wire will relatively readily bend even at a branch of vessel. Consequently, the guide wire can be introduced to the predetermined site in the vessel without substantial difficulty.
In addition, the body portion of the guide wire has improved torque transfer in either twlsting direction, ensuring that the leading edge is readily advanced to the desired direction by applying a properly selected twisting torque to the body portion. The guide wire can thus be :
1324~S3 introduced to the predetermined site through a winding vessel with a relatively easy manual operation.
Obviously many modifications and variations of the present invention are possible in the light of the above teachings. Although a tapered head is described as the preferred distal portion in the above embodiments, a tubular head having an equal diameter or a modified head having stepwise varying diameters may be used as the distal portion.
In this case, a step is formed at the connection between the distal and body portions, but an envelope may be evenly coated over the core to accommodate the step, providing a smooth outer surfaceO It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
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