WO1992008501A1

WO1992008501A1 - Fixed wire catheter and unitary guidewire

Info

Publication number: WO1992008501A1
Application number: PCT/US1991/007394
Authority: WO
Inventors: Dong Ik Shin; Leo R. Rocher, Jr.
Original assignee: Medtronic, Inc.
Priority date: 1990-11-09
Filing date: 1991-10-03
Publication date: 1992-05-29

Abstract

A fixed wire catheter (110) having a torque-transmitting shaft, a flexible body surrounding the shaft (112), and an inflatable balloon (116) having a proximal end mounted on the flexible body is disclosed, where the torque-transmitting shaft is comprised of a unitary core wire (1). Also a unitary guidewire is disclosed. Usually the core wire or guidewire is comprised of a cylindrical main shaft (2), a flat distal portion (4), and a cylindrical distal tip (6), but it may have a tapered portion (8) between the shaft and the flat portion. The distal end is larger in cross-sectional area than the cross-sectional area of the flat portion, and the section connecting the two is usually tapered and preferably rolls outward toward the distal end. The catheter includes a tip spring (14) having a proximal end fixedly mounted to the shaft proximal to the distal end of the balloon and a distal end fixedly attached to the distal end of the shaft.

Description

FIXED WIRE CATHETER AND UNITARY GUIDEWIRE

BACKGROUND OF THE INVENTION

This is a continuation-in-part of U.S. Patent Application Serial Number 07/495,259 filed 3/16/90, which is incorporated herein by reference as though fully set forth.

Field of Invention

This invention relates to catheters, particularly fixed wire catheters for opening lesions in arteries, and guidewires for guiding such catheters in the vascular system.

Description of the Prior Art

Catheters designed for steering through a tortuous path of small arteries, such as the coronary arteries, have been of two general types. One type, the "over-the- wire catheter," slides over a separate guidewire. The second type, a "fixed wire catheter" has a guidewire built into the catheter in the unit.

Various considerations dictate the form of a guidewire and a fixed wire catheter. For example, the device must first be stiff enough to be able to be pushed into the vascular system. Usually, in order to steer it into branches of the vasculature or around bends, the tip is bent into a "J" shape ahead of time. To turn the tip so that the "J" reaches around a bend or into a branch, torque must be transmitted down the guidewire or down the core wire of the catheter. Thus torque transmission down the wire or shaft is an important characteristic. Finally, also in order to be pushed around bends in the vasculature, the device must be flexible. These characteristics may sometimes seem to be almost mutually exclusive in a T small device such as a catheter or guidewire.

To obtain the desired characteristics in a guidewire, various attempts have been made to taper the shaft and shape a spring which is fitted around the tip, as shown in many of the patents listed below. U.S. Patent Nos. 4,559,929, 4,538,622,

4,827,941, 4,763,647, 4,345,602 issued to Samson et al., Samson et al., Taylor et al., Gambale, and Yoshimura et al., disclose guidewires made of multiple pieces of wire. U.S. Patent Nos. 4,538,622, 4,719,924, 4,545,390, and 3,789,841 issued to Samson et al., Crittenden et al., Leary, and Antoshkiw disclose cylindrical wires apparently made of a single core unit and which may minimize weak points and off-center joints.

U.S. Patent no. 4,721,117 issued to Mar et al., discloses a single piece wire with a flattened distal tip. U.S. Patent No. 4,811,743 issued to Stevens discloses a unitary stainless steel wire with a flat distal portion and an unflattened end portion having about the same cross-sectional area as the flattened portion. The end is TIG welded with a tip spring in place to form a spherical distal tip that rotates independent of the distal end of the tip spring. All of these wires have had benefits and faults resulting from their design.

What is needed is a guidewire or catheter shaft structure which provides the needed pushability and torque transπvssion in the tip area while being flexible and of low profile. Also, to obtain the desired characteristics, it is helpful to avoid weak points in the wire resulting from brazed or welded joints as well as reduced torque transmission resulting from off-center joints. It would also be desirable to avoid the manufacturing steps involved in brazing or welding parts of the guidewire together. It would further be desirable to obtain such features in a fixed wire catheter which avoids the problem of "balloon wrap" described in Assignee's co-pending U.S. parent application Serial No. 07/495,259 filed 3/16/90. 0 , SUMMARY OF THE INVENTION

In one aspect, the invention is a fixed wire catheter having a torque-transmitting guidewire or shaft, a flexible body surrounding the shaft, and an inflatable balloon

65 having a proximal end mounted on the flexible body, where the torque-transmitting is comprised of a single or unitary core wire. Usually the core wire is comprised of a cylindrical main shaft, a flat distal portion, and a cylindrical distal end, but it may have a tapered (or stepped) portion between the shaft and the flat portion. The distal end is generally larger in cross-sectional area than the flat portion. In

70 some embodiments, the core wire may have two or three tapered (or stepped) portions and one or more smaller shafts therebetween, all disposed between the main shaft and the flat portion. In the preferred embodiment, the wire has a tapered portion between the flat portion and the distal tip, and the tapered portion is preferably radiused, for a strengthened member.

75

The catheter may further include a tip spring having a proximal end fixedly mounted to the shaft proximal to the distal end of the balloon and a distal end fixedly attached to the distal tip of the shaft. In some embodiments it also includes a housing having a first body portion with a male segment with a longitudinal

80 groove, a second body portion mounted for rotational movement about the male portion of the first body, the second body having a helical groove, and a ball means mounted for movement along the helical groove and along the longitudinal slot so that movement of the first body relative to the second body is stopped when the ball reaches the end of the slot. t. 85 ' In another aspect, the invention is a unitary or single core guidewire having a main cylindrical shaft, a distal flat portion and a dists! end larger in cross-sectional area than the cross-sectional area of the flat portion. Tapered portions may be included between the flat portion and the distal end, and the flat portion and the main shaft. 90 Multiple smaller shafts, and tapered portions, may be included between the main shaft and tapered portion. The taper between the flat portion and distal end is preferably radiused (or rolled) for a strengthened member. The invention in another aspect is a method of making the guidewire.

95 BRIEF DESCRIPTION OF THE DRAWINGS

Figs. 1A and 1B are top plan views of a portion of unitary wires of the present invention.

00 Fig. 2 is a side view of another unitary wire of the present invention.

Fig. 3 is a side view in cross-section of a fixed wire catheter according to the present invention.

05- Fig. 4 is a greatly enlarged side view in cross-section of the distal tip of a fixed wire catheter according to the present invention.

Fig. 5 is a side view in cross-section of the proximal end of the fixed wire catheter and balloon of the present invention. 10

Fig. 6 is a side view, also in cross-section, of the proximal portion of the balloon and the adjacent catheter body in the present invention, all greatly enlarged.

DETAILED DESCRIPTION OF THE SPECIFIC EMBODIMENTS 15

Turning to Figs. 1A, 1B, and 2 the core or guidewire of the present invention comprises a single piece of material (i.e., is "unitary" or is a "single core wire"), usually stainless steel to form the wire. The wire shown in Fig. 2 has a proximal cylindrical main shaft 2, a flat distal portion

4, and a distal end 6 also in the form of a cylindrical shaft. A first tapered (or, equivalent^, stepped) segment 8 is located between shaft 2 and flat portion 4; a second tapered 10 segment also is located between flat portion 4 and end 6; it smoothly blends into the flat portion but not into end 6. Sometimes, a straight tapered end such as 10 in Fig. 1 B is included, but sometimes the taper is radiused

(i.e., curved or rolled) as in Fig. 1A, for a stronger member.

End portion 6 may be of the same diameter, larger, or smaller than proximal shaft 2. Preferably it is the same size or slightly smaller in diameter than the main shaft. In the guidewire, it is larger in the cross-sectional area than the flat portion 6. A tip coil 4 may be included and is preferably attached as shown in Fig. 4 illustrating the wire when it is included in a fixed wire catheter.

In some embodiments, as that shown in Fig. 1A, a second shaft 12 and third tapered segment 14 are disposed between the first tapered segment and the flat portion. Yet another cylindrical shaft 11 and fourth tapered segment 13 can be disposed between the flat portion and main shaft as shown in Fig. 1B. The number of shafts of varying sizes are dictated by the requirements of the particular application.

The catheter core wire is preferably the version shown in Fig. 1A and the flat portion 4 is preferably only about one centimeter long and the end 6 is only a millimeter or less in length. Taper 8, in this version, ends about 30 cm. from the distal tip, near the marker portion 160 shown in Figs. 3 and 4.

Turning to Figs. 3, 4, 5, and 6,. the catheter 110 includes a flexible catheter body 112, a unitary core wire 1 like that shown in Fig. 2, a balloon 116, a flexible tip 118, and a manifold or handle 120. Handle 120 includes an arm 124 for mounting balloon inflation equipment and a second arm 126 for guidewire mounting. A 150 rotatable handle 128 is mounted for rotation within arm 126.

As shown in Fig. 6, catheter body 112 includes a body spring 140 which is a spring wound of metal of a rectangular cross-section. Body spring 140 forms a lumen 142 through which the core wire 1 passes. Mounted within lumen 142 is a 155 smaller diameter stainless steel spring 144 which is brazed to body spring 140 at brazed 146. In the illustrated embodiment, body spring 140 has an outside diameter of 0.30 inches and spring 144 has an outside diameter of .026 inches.

Flexible plastic tubing 148 is mounted over body spring 140, as in the prior art 160 Omniflex device. In the preferred embodiment, tube 148 is made of polyethylene shaft stock.

Tubing 148 is tapered at its distal section 150 where it narrows to fit over spring 144. Balloon 116 has a proximal section 152 mounted over the tapered section

165 150 of tube 148. Spring 148 is attached to tube 148 by adhesive. In the preferred embodiment, section 152 of balloon 116 is cut off with a square nontapered end. The section 150 of tube 148 which is not covered by balloon portion 152 is filled in with adhesive 154 to make a smooth external surface of the outside diameter of tube 148. Balloon proximal portion 152 and adhesive 154 are generally equal

170 in diameter. In the preferred embodiment, adhesive 154 is an ultraviolet cured adhesive.

Referring to Figs. 4 and 6, a radiopaque marker band 160 is mounted within balloon 16 on core wire 1, preferably by brazing. Marker 160 is made and 175 attached using common prior art techniques. Marker 160 is preferably a platinum cylinder, but may be platinum wire wound around wire 1. In order to have a smooth transition from wire 1 to marker 160, a ramp of adhesive 162 formed at either end of the marker 160. In the preferred embodiment, adhesive 162 is cyanoacrylate. f80

Referring to Fig. 6, shaft 1 is the unitary core wire formed of a single piece of material as described above. Separate tip spring or coil 14, preferably also made of platinum, is attached to core wire 1. Tip coil 14, usually made of platinum r another radiopaque material, is attached, preferably by welding or brazing to the

185 distal end. TIG (Tungsten inert gas) welding is preferred because it creates a well- rounded and smooth distal tip 16 unlikely to injure the artery at the same time the spring 4 is attached. Weakening of the wire due to the high temperatures required (above about 3000 degrees F) is minimized because the coil is welded distally to the large cylindrical distal end 6 rather than to a narrower, weaker portion such as

190 the flat portion 4. Thus, a stronger, more torqueable guidewire less likely to break is created. Where a wire of constant diameter throughout is desired, distal end portion 6 is smaller in diameter than main shaft 2 so that the overall diameter of the device with tip coil is the same as the diameter of the main shaft.

195 At its proximal end, the tip coil in the preferred embodiment is brazed to core wire

1 on main shaft 2 at area 18, although it can be attached elsewhere on the wire for particular needs. Therefore, spring 14 is fixed at either end but flexes throughout the rest of its structure.

00 In the fixed wire catheter shown, a tip tube 182 is mounted over proximal portions of coil 14. It is attached to main shaft 2 of core wire 1 distally of the marker by adhesive 113 which in the preferred embodiment is cyanoacrylate. This seals the ^' interior of tube 182 from the interior of balloon 116. Tip tube 182 extends distally through the distal end 186 of balloon 116. Distal end 86 of balloon 116 is bonded 05 to tube 182 by adhesive 115 which, in the preferred embodiment, is an ultraviolet cured adhesive. In turn, tube 182 is heat shrunk over coil 14, extends distal to the balloon, and acts as strain relief for the core wire. The structure of catheter 110 provides a free moving guidewire within spring 14 so that the catheter is not susceptible to balloon wrap. When wire 1 is rotated, it moves freely within lumen 142 of body spring 140 and within tip spring 14. If shaft

1 is turned excessively by the user of the catheter, the torque is taken up in spring 14 and not transmitted to balloon 116. Both proximal section 176 and distal section 178 of tip spring 14 are loosely wound springs which will absorb the torquing effect. This allows multiple turns of wire or shaft 1 without effect on balloon 116.

As a reminder to the physician to return wire 1 to the center position, means are provided to indicate the number of turns made. In manifold 120, wire or shaft 1 is attached to strain relief means 190. Shaft 1 continues through lumen 192 through silicone seal 194. A threaded lumen 195 has female threads 196.

Guidewire housing 197 has male threads 198 which mate with threads 196. The interacting threads squeeze silicone seal 194 to prevent backfiow of fluid out of lumen 192.

Guidewire housing 197 has a longitudinal groove 199 which has a semicircular cross-section. Rotatable handle 128 is mounted over second housing 197. Handle 128 is held to housing 197 by spring clip 189 and has a bore 187 which is cut with helical threads 185. The cross-section of helical thread 185 is a semicircle matching in diameter the cross-section of longitudinal groove 199. A ball 183 is mounted to ride within groove 199 and helical threads 185. As rotatable handle 128 is turned relative to guidewire housing 197, ball 183 follows helical grooves 185 and moves, correspondingly, up and down longitudinal groove 199. When ball 183 reaches an end of groove 199, handle 128 can no longer rotate in that direction. Therefore, the amount of turn of rotatable handle 128 relative to housing 197 depends on the number of turns of helical groove 199. In the embodiment illustrated, handle 128 can be turned four times in either direction. Although balloon twist does not occur in the design illustrated, the limitation on rotation reminds the physician that rotation has occurred in one

240 direction and that further rotation in the same direction can cause spring compression in the tip section.

The use of the unitary core wire in the catheter of the present invention minimizes weak points in the wire by eliminating joints and minimizing heat damage from TIG

245 welding in narrow areas of the wire. It also eliminates off-center segments or joinings and thereby maximizes torque transmission by eliminating off-center shaft segments. It eliminates the manufacturing steps of brazing. The large distal end allows easy welding of the tip spring during manufacture to create a smooth and rounded distal tip without separately brazing attaching both the tip 16 and the

250 spring 14.

To make the core wire or guidewire of the present invention, a cylindrical stainless steel wire is utilized. Tapered regions such as 8 and 10 are created by grinding as are the smaller shaft areas 11 and 12. The wire is then flattened as desired to 255 create flat distal portion 4. A flat press can be used, but a roller is preferred, to smoothly form the flat portion and create a smooth transition to the tapered portion adjacent the distal end. The remainder of the fixed wire catheter is made by conventional methods or by methods already described.

60 To use the guidewire or the fixed wire catheter of the present invention, a guiding catheter is normally threaded through the vascular system to a position near the _*f coronary veins or arteries. The tip of the guidewire or the catheter core wire is then usually bent or deflected to promote steerability, and inserted and steered through the guiding catheter into the twisting pathways of the coronary arteries, to 65 the point of interest, usually just past a stenosis to be removed. In the case of the guidewire, an over-the-wire catheter is then threaded over it for insertion into the vascular system and ultimate use. In the case of the fixed wire catheter, it is already inserted and is then used for the operation needed, for example, angioplasty, in the standard manner.

While the present invention is disclosed in terms of particularly illustrated embodiments, it is understood that those skilled in the art may use the invention, which is described in the appended claims, in other forms.

Claims

275WHAT IS CLAIMED IS:

1. A fixed wire catheter comprising:

280 a torque-transmitting shaft;

a flexible body surrounding the shaft; and

an inflatable balloon having a proximal end mounted on the flexible body 285 and wherein the torque-transmitting shaft is comprised of a unitary core wire.

2. A catheter according to claim 1 and wherein the core wire is comprised of a cylindrical shaft, a flat distal portion, and a cylindrical distal end.

290

3. A catheter according to claim 1 and wherein the cross-sectional area of the cylindrical distal end is greater than the cross-sectional area of the flat portion.

295 4. A catheter according to claim 3, the core wire having a tapered portion between the shaft and the flat portion.

5. A catheter according to claim 3, the core wire having two tapered portions and a smaller shaft therebetween, all disposed between the shaft and the 00 flat portion.

«

6. A catheter according to claim 3, the core wire having a tapered portion between the flat portion and the distal end.

305 7. A catheter according to claim 3 and further comprising a tip spring having a proximal end fixedly mounted to the shaft proximal to the distal end of the balloon and a distal end fixedly attached to the distal tip of the shaft.

8. A catheter of claim 7 further comprising:

310 a housing having a first body portion with a male segment with a longitudinal groove;

a second body portion mounted for rotational movement about the male 315 portion of the first body, the second body having a helical groove;

a ball means mounted for movement along the helical groove and along the longitudinal slot so that movement of the first body relative to the second body is stopped when the ball reaches the end of the slot. 320

9. A unitary guidewire compounding a cylindrical main shaft, a distal flat portion and a cylindrical distal end larger in cross-sectional area larger than the cross-sectional area of the flat portion.

325 10. A unitary guidewire according to claim 9 and wherein a first tapered portion is located between the flat portion and the distal end and a second tapered portion is located between the flat portion and the main shaft.

11. A unitary guidewire according to claim 10 and wherein the first tapered 330 portion is radiused to improve the strength of the member.

12. A unitary guidewire according to claim 10 and including more than one shaft and tapered portion between the main shaft and flat portion.