CA2208083A1

CA2208083A1 - Improved method of soft tip forming

Info

Publication number: CA2208083A1
Application number: CA002208083A
Authority: CA
Inventors: Michael C. Riopel; John B. Horrigan
Original assignee: Individual
Current assignee: Medtronic Inc
Priority date: 1995-01-04
Filing date: 1995-12-21
Publication date: 1996-07-11
Also published as: US5811043A; AU4605896A; DE69504104T2; EP0801581B1; DE69504104D1; JPH10511871A; US5792124A; EP0801581A1; WO1996020750A1

Abstract

The present invention comprises a catheter and method of manufacture. The catheter includes an elongated core having a unitary lubricous liner and a reinforcement means. The lubricous liner defines at least one lumen. The lubricous liner has the reinforcement means over its outer diameter and fused to the lubricous liner. The reinforcement means terminates proximal to the distal end of the lubricous liner. The catheter also has an elongated shaft tube which defines a shaft tube lumen. The shaft tube lumen is sized to receive the core, the core which extends longitudinally through the shaft tube lumen. The shaft tube is fused to the core. The catheter also has an elongated transition tube which defines a transition tube lumen. The transition tube lumen is sized to receive the core which extends longitudinally through the transition tube lumen. The distal end of the shaft tube is fused to the proximal end of the transition tube. The transition tube is made of softer material than the shaft tube and is fused to the core. The catheter further includes an elongated tip tube made of softer material than the transition tube. The tip tube defines a tip tube lumen sized to receive the core which extends longitudinally throughout the tip tube lumen. The distal end of the transition tube is fused to the proximal end of the tip tube. The tip tube is fused to the core distal to the distal end of the reinforcement means, the distal end of the tip tube forming a rounded edge which overlaps the distal end of the lubricous liner by about .5 mm such that the distal end of the lubricous liner is not exposed.

Description

IMPROVED METHOD OF SOFT TIP FORMING
Field of the Invention The present invention relates to catheters, and more particularly, to a method of soft tip ~tt~rhment 5 Back~round of the Invention C~thP,t~Prs are tube-like members inserted into the body for diagnostic or therapeutic reasons. One of the therapeutic procedures applicable to the presentinvention is known as pel~;ukllleous tr~n.~lllmin~l col~llaly angioplasty (PTCA).
This procedure can be used, for example, to reduce arterial build-up of cholesterol 10 fats or atherosclerotic plaque. ~thPters must have sufficient ~l;rrllPss to be pushed through vessels as well as sufficient rigidity to provide a high degree of torsional control. Stiffness or rigidity in the catheter tip poses the danger ofpnnttllrin~ or otherwise rl~m~gin~ a vessel as it twists through the vascular system.
It is therefore desirable for c~thPtP-rs to have a soft or flexible distal tip.
15 Examples of such soft tip c~thPters are known in the art.
The trend toward catheters with larger inside diameters and softer distal tip segments results, however, in a subst~nti~lly weaker bond between the soft tip and the distal catheter shaft because of the thinner wall fhi~nPss and lower tensilestrength of the softer materials. The following methods of tip ~tt~chmPnt are 20 known in the art.
Soft tips are often ~tt~hPcl by means of a lap joint or butt joint at the distal end of the catheter body where the soft tip has been fused or welded to the catheter body. A butt joint or lap joint is undesirable because they create a stress concentration area at the distal end of the catheter shaft in a plane perpen~ r 25 to the longitll-lin~l axis of the catheter shaft. The effect of this.stress concentration is an low bond strength between the catheter shaft and the soft tip when the wall thicknP-s~s of the catheter shaft is less than 0.3 mm.
U.S Patent No. 4,596,563to Pande for a "Thin-Walled Multi-Layered Catheter Having a Fuseless Tip" discloses a two layered tubular body having a 30 rigid inner sheath and a flexible outer sheath. The tip portion is fuseless with respect to the rest of the catheter, the tip portion being an integral extension of the flexible outer sheath that is formed over a gap between iengths of the rigidinner sheath.

WO 96/20750 PCT/US9~/16745 U.S Patent No. 4,636,346to Gold et al for a "Plepal.llg Guiding ~thPter"
discloses a three-layered tubular body having a lubricous inner sheath defining a lubricous guiding lumen, a rigid intenn~ te sheath and a flexible outer sheath.
The distal tip portion has a similar construction but from which the rigid S interm~ t~ sheath is omitted. Col. 5, lines 12 - 20 discloses a tip portion that may be an initially sepa~aLe member aff~ed to the el-~ng~t~cl tubular body 22 bysuitable means, such as by heating, by other energy sources, and/or by adhesivesor the like. Such assembly can be ~si~ted by the use of a length of shrinkable tubing that is placed over the joint location prior to and during the assembly operation in order to enh~nre the smoothness and strength of the joint. It is anobject of the invention to not require adding any braiding or strands of strengthening material.
U.S Patent No. 4,863,442to DeMello et al for a "SoftTip ~.~th~ter"
discloses a tubular body with a wire-braided Teflon~ core and a polyu~,ll,ane jacket. The distal end of the jacket is removed from the core, and a soft polyu,ell,d,le tip is applied to the core over the region where the jacket has been removed. The tip overlaps the core for approximately two millimeters and extends distally approximately two millimPters beyond the distal end of the core.
The tip may be applied to the core as a separate tube bonded to it or be built up on the core by repeatedly dipping the tip in a polyurethane slurry, or be moldedonto the distal end of the core. An embodiment at col. 5, lines 30 - 39 discloses a sleeve of shrink film 64 placed over the polyu,eLl,dlle tube 40 with the distal end of the jacket 18 and overlapping the shoulder 34. With the sleeve of shrink film64 in place as shown in Fig. 2G, the distal end of the assembly is heated to a tell,peldLul~ and for a time sufficient to cause the soft polyurethane tube 40 to flow and fill the gap 46 along with any other gaps which may exist between it and the shoulder 34, outer surface 36 of the core 16, and the outer surface 54 of the mandrel 50.
U.S Patent No. 5,254,107to Soltesz for a " Catheter Having Extended Braid Reinforced Transitional Tip" discloses an embodiment in col. 4, lines 34 - 41 wherein an inner tubular plastic layer 22 defines the inner diameter of the catheter, and which extends through the first and second sections 16, 18, but not Wo 96/20750 PcTlus9sll6745 through third tip section 20. Inner tubular layer 22 may be made of PTFE. A
braided st~inles~ steel fiber tubular member 24 ~ul~oullds inner plastic layer 22.
In the commonly owned, copending application of Brin et al. for "Improved Method of ~th~ter Segment ~tt~rhm~nt" U.S. application serial nllmher 08/236,766 the distal end of the catheter consists of three segments, the transition tubing which is attached to the shaft, the soft tip tubing which is ~tt~h~d to the transition tubing, and the "plug"tubing which is ~tt~chPd to the soft tip tubing for ease of h~nflling during m~nllf~tllre and into which a support mandrel is inserted.
All t_ree segments are ~ull~unded by a tube of heat shrink. The heat source actsupon the transition tubing with the heat being propagated to the soft tip tubing.
After assembly, the plug tubing and part of the soft tip tubing are trimmed off.The catheter shaft is comprised plillci~ally of three layers: a lubricous TEFLON~
liner, a composite layer of wire braid and polymer, and an outer jacket polymer.The wire braid and TEFLON~ liner do not extend into the transition tubing or into the soft tip tubing.
An object of the invention is to create a guiding c~th~ter soft tip with wall thickness less than 0.3 mm which provides improved bond strength to the ç~th~oter shaft joints, and in particular, the joint between the soft tip segment and the segment proximal to the soft tip.
Another object of the invention is to provide a lubricous inner lumen throughout the catheter body including throughout the soft tip while shielding the lubricous liner from contact with the vessel wall and while m~int~ining a curvedcontour at the distal end.
Another object of the invention is to minimi7~- the length of the unreinforced section of the soft tip to avoid devices snagging during deployment.
SUMl\IARY OF THE INVENTION
The present invention comprises a catheter and method of m~mlf~cture.
The catheter inr.llld~s an elongated core having a unitary lubricous liner and areinforcement means. The lubricous liner defines at least one lumen. The lubricous liner has the reinforcement means over the its outer rli~m~ter and fused to the lubricous liner. The l~h~olcement means termin~tes proximal to the distalend of the lubricous liner. The catheter also has an elongated shaft tube which defines a shaft tube lumen. The shaft tube lumen is sized to receive the core, the Wo 96/20750 PCTIUS95/16745 core which extends lon~ihl(lin~lly through ~e shaft tube lumen. The shaft tube is fused to the core. The c~tht~,ter also has an elongated transition tube which defines a transition tube lumen. The transition tube lumen is sized to receive the core which extends lonP~ihl~lin~lly through the transition tube lumen. The distal 5 end of the shaft tube is fused to the proximal end of the transition tube. Thetransition tube is made of softer material than the shaft tube and is fused to the core. The c-~th~ter further includes an elongated tip tube made of softer material then the tr~n~ition tube. The tip tube defines a tip tube lumen sized to receivethe core which extends longit~(lin~lly throughout the tip tube lumen. The distal10 end of the transition tube is fused to the proximal end of the tip tube. The tip tube is fused to the core distal to the distal end of the reinforcement means, the distal end of the tip tube forming a rounded edge which overlaps the distal end of the lubricous liner by about .5 mm such that the distal end of the lubricous liner is not exposed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is the preassembly plan view of the distal end of a guiding catheter prior to the outer jacket molding process;
FIGURE 2 is the molded assembly of Fig. l;
FIGURE 3 is the is a cross-sectional view of the distal tip of the molded 20 assembly of Fig. 2;
FIGURE 4 is the plan view of the distal end of a guiding catheter prior to the soft tip formation process;
FIGURE 5 is the molded assembly of fig 4; and FIGURE 6 is a cross-sectional view of the distal tip of the molded 25 assembly of Fig. 5.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention addresses the problem created by the trend toward catheters with larger inside diameters and softer distal tip segments. Soft tip guiding catheters are desirable because the gentle ostial engagement is less 30 tr~llm~tic. Soft tips provide a coaxial fit in all anatomies to allow for improved device delivery by m~int~inin~ a rounded tip shape which adapts to different ostial take-offs. Larger lumens are desirable because they permit more dye flow and offer more device delivery options. The trend toward catheters with larger inside Wo 96120750 PCT/US95/16745 tliAm~ters and softer distal tip segments results in a substantially weaker bondbetween the soft tip and the distal end of the catheter shaft due to thin cAth~ter shaft walls of less than 0.3 mm and to the lower tensile strength of the softer tip materials. Applicants address the problem of bond strength between segments and that of achieving greater lumen lubricity by extending a unitary liner throughout the shaft, transition tubing and soft tip segments, the liner being made of a fluoropolymer such as TEFLON~ from E.I. Du Pont de Nemours & Col~al,y, Wilmington, Delaware. TEFLON~ which is a form of polyleLl~fluoroethylene (PTFE). To m~intAin a soft tip, the TEFLON~ is shielded from contact with the vessel wall by using heat shrink tubing in a heating process to draw the distal end of the soft tip material over the exposed TEFLON~ liner.
~nllf~ctllring applicant's thin wall guiding catheter consists of two major processes, outer jacket molding and soft tip formation. Fig. 1 - 3, ~c~rcsell~
applicant's assembly for molding the outer jacket to the braided TEFLON~ core material. Figs. 4 -6 1~1CSe11~ applicant's assembly for forming the soft tip.
Referring to Fig. 3 which depicts the molded assembly, the shaft of the thin wall guiding catheter for outer jacket molding is assembled as follows. Slide the TEFLON~ liner 40 over a stAinles~ steel mandrel 30 (not shown in Fig. 3). The mandrel 30 may optionally be TEFLON~ coated. Next, braid wire 35 over the TEFLON~ liner 40. The mandrel 30 has an outer diameter of approximately .001 inch less than the inner ~ m~ter of the TEFLON~ liner 40. The mandrel 30 is used for support. TEFLON~ beading could be ~ Alively used for support.
After the catheter shaft is assembled, the support will be removed. The TEFLON~ liner 40 provides a lubricous surface which aids device delivery by providing a low friction interface. This is especially important for the smooth passage of large, non-balloon devices which may not conform as readily to guiding catheter curves. The TEFLON~ 40 enh~nres device deliverv with less device "capture" while ensuring ch~ulllfel~llLial integrity.
Wire 35 is braided by means of a conventional braiding mArhin~ over the TEFLON~ liner 40 as shown in Fig. 3. The wire braid 35 is advantageous because it reinforces and supports the large lumen for thin wall guiding catheters.
The wire braid 35 is a 16 strand stainless steel braid which runs the length of the catheter and is trimmed a ~ew millimeters proximal to the distal end of the W 096/20750 PCTrUS95/16745 TEFLON~ liner 40. The distal end of the wire braid 35 is then adhesively bonded to the TEFLON~ liner 40. Those skilled in the art would recognize that other reinforcement means could be used, such as carbon fibers.
The c~thPter shaft comprises a plurality of segments ove.ly,l-g the wire braid 35 and TEFLON~ liner 40. These segments, the 72D shaft tubing 25, the 55D transition tubing 15, the 35D soft tip tubing 20 and the 72D plug tubing 45 are made from PEBAX~. Although other polymers can be found in a suitable durometer range, PEBAX~, a polyether block amide copolymer obtainable from the Elf Atochem Corporation, Phil~tlelpllia, PA, is preferable in catheter design because it is an el~tomer, has low moisture absorbance, offers long term stability of material properties, provides high tensile strength and can be processed at temp~ ures in the 400 degree F range as required by commonly available extrusion equipment. The segments are abutted as follows.
The shaft tubing 25 is made from PEBAX~ in the hardness range of Shore durometer D65-D75 and preferably 72D. The transition tube 15 may have a hardness range of Shore durometer 50D - 60D and preferably 55D. Taper the end of the 72D Pebax~ shaft tubing 25 using an outside taper cutting tool. Cut aShore 55D Pebax~ transition tube 15 to 3.7 cm in length and taper the end using an inside taper cutting tool. The 3.7 cm length was chosen from an acceptable range of 2 cm to 18 cm based on anatomical considerations, as 4 cm is the average width of the aortic root. Slide the ull~ d end of the Shore 72D shaft tubing over the braided TEFLON~ liner 40 from its distal end. Next slide the 55D transition tubing 15 onto the mandrel 30 and over the braided TEFLON~
liner 40 from its distal end such that the tapered end of the 55D transition tubing 15 mates with the tapered end of the 72D shaft tubing. The 72D shaft tubing 25 and 55D transition tubing 15 can be tapered because the materials are stiff enough to retain their shape when melted. The material at the joint will blend better when the mating ends are tapered yielding better bond strength than wouldan abutted end as there is greater surface area over which to blend the materials.
The 55D transition tubing 15 may have a wall thickness of .013 inches (.033 cm) and an inner diameter ranging from a mi~ of .078 inches for 6F to a m~ximllm of .126 inches for 10F. The wire braid 35 extends through the 55D
transition tubing 15 to offer better kink resistance and ends preferably at Wo 96/20750 PCTIUS95/16745 approximately the proximal end of the 35D soft tip tubing 20 to permit m~ximllm flexibility in the soft tip 20. The wire braid 35 can stop from 2 - 3 mm proximal to the 35D soft tip and still provide sufficient l~h~fo,cement but should not extend more that 1/3 of the length of the soft tip 20 into the proximal end of 35D soft tip 20 to provide optimal soft tip 20 flexibility. At least one inch of the mandrel 30 should extend beyond the distal end of the 35D tip tube 20 for ease of h~n~lling.
A softer durometer material is used for the soft tip 20 than for the transition tubing 15 to give the distal end more flexibility; this aids in tip pl~eem~nt The soft tip 20 may be in the range of Shore 25D to 40D and preferably 35D. The 35D tip tube 20 can be made of Pebax~. The 35D tip tube 20 preferably has a length of approximately 1 cm prior to trimming and a wall thickn~ss of .013 inches (.33 cm) and an inner diameter ranging from a mi~
of .078 inches for 6F to a m;.xi,,,ll,,~ of .126 inches for 10F. The 1 cm length was chosen for h~nl1ling convenience during the trimming process. Rec~llse the TEFLON~ liner 40 extends throughout all three segments (the 72D shaft tubing 25, the 55D transition tubing 15 and the 35D soft tip tubing 20) lubricity is improved and device delivery enh~nl e~ Furtherrnore, the unitary TEFLON~
liner 40 extending throughout the shaft improves joint strength between the 72D
shaft tubing 25 and the 55D transition tubing 15 as well as between the 55D
transition tubing 15 and the 35D soft tip tubing 20.
Slide a Shore 72D Durometer plug tube 45 of approximately 1 cm onto the distal end of the mandrel 30 until it butts against the distal edge of the 35D soft tip tubing. The plug tube 45 can be made of Pebax~. Leave approximately 15.2 cm or 6 inches of mandrel 30 extending distally beyond the assembly for h~ntlling convenience.
Slide a segment of TEFLON~ fluorinated ethylene propylene (FEP) heat shrink tubing 10 over the entire assembly with approximately 1 cm of heat shrinkextending beyond the distal end of the 72D plug tube 45 and over the mandrel 30.Heat shrink tubing such as that from Zeus Industrial can be used. Ensure that the joint between the 55D transition tubing 15 and the 35D soft tip tubing 20 is approximately 15.9 cm from the distal end of the mandrel 30 for h~nrlling convenience.

wo 96/20750 Pcr/uss5/16745 The outer jacket is molded when the heat shrink 10 is heated by any suitable means to fuse the segments. For example, radiant heating or conduction heating can be used. Heat shrink tubing 10 contraction, when coupled with heating the tip materials causes them to exp~n~1, resllltin~ in the m~t~.ri~lc 5 blending and flowing into one another. A lap joint between the materials is produced. Those skilled in the art would recognize that dirr~ time and temperature combinations would be suitable as time and temperature vary inversely.
To achieve bonding, the time and t~ ?eldlure selected must be sufficient 10 to render the materials flowable. T~nlp~,ld~ulcs which are too high will result in a brittle product. Temperatures which are too low will result in i~ ropel fusion. A
suitable convection oven temperature for outer jacket molding includes 185 degrees centigrade. This L~m~tl~Lulc should be m~int~in~d for app~o~ laLely 7 to 8 minllt~s depending on the size c~th~ter being molded. Those skilled in the 15 art would recognize that dirr~lt;lll time and telllpel~lule combinations would be suitable as time and tel~ a~ule vary inversely. Referring to Fig. 2, the heat source causes the catheter shaft tubing 25, the transition tubing 15, the soft tip tubing 20 and the plug tubing 45 to become flowable while the heat shrink 10 contracts both radially and longi~l-lin~lly thereby colliding all segments. This20 results in a lap joint between each segment.
The heat shrink tubing 10 is removed with a razor blade and the molded tip assembly is cut to length. The distal end is trimmed back to a point within the 35D soft tip tubing to result in a tip length of 2.5 mm distal to the 55D transition tubing 15. Lengths that are much longer are undesirable because the soft tip 20 is 25 not structurally rigid and may fold back upon itself and cause difficulty with device passage. The mandrel 30 is removed from the inside of the now bonded assembly.
Fig. 3 shows the enlarged longihl(1in~l cross section of the distal end portion of the molded assembly of Fig. 2.
After outer jacket molding, the soft tip 20 is formed. Extending the 30 TEFLON~ liner 40 to the distal end of the soft tip tubing improves lubricity. The unitary liner also improves joint strength between the 35D soft tip 20 and the 55D
transition tubing 15 but results in a tip that is too sharp. To remedy this, a so~t tip 20 tapered distal edge which overlaps and shields the TEFLON@3 liner 40 and can be created as follows to blunt the sharp TEFLON~ liner 40. See Figure 4.
Taking the assembly from the outer jacket molding process, insert a mandrel 30 into the distal end of the assembly such that at least I inch protrudes from thedistal tip of the assembly. Apply approxim~tely 2 inches of heat shrink tubing 110 5 over the distal end of the assembly such that the heat shrink 110 extends one-half to one centim~ter beyond the proximal and distal ends of the soft tip 20 material as seen in Fig. 4. Next insert the assembly (until the soft tip 20 material can no longer be seen) into a preheated forming die, as for example, a hot block con~ ting of a brass cylinder with and external band heater. Dwell at a 10 temperature of 400 degrees F. This temperature is m~int~in~ for approximately7 to 8 seconds depending on the size catheter being molded. Those skilled in theart would recognize that different time and temperature combin~tion~ would be suitable as time and temperature vary inversely. Remove the assembly from the forming die. The heat shrink 110 will have contracted about the soft tip 20 as 15 seen in Fig. 5. After the assembly has cooled for at least 10 seconds, remove the heat shrink tubing 110. Remove the supporting mandrel 30. As seen in Fig. 6, the contraction of the heat shrink 110 will have caused the 35D soft tip 20 material to flow and draw the distal end of the 35D soft tip 20 approximately .5mm over the distal end of the TEFLON~ liner 40, thereby covering the exposed 20 TEFLON~ liner 40 by creating a somewhat r~tlin~e~l, overh~nging edge 65.
Applicants leinfol~ed soft tip 20 with an unreinforced rounded edge 65 is advantageous. A rounded edge 65 shielding the exposed TEFLON~ liner 40 reduces trauma in body cavities. It is common to deliver such devices as ballooncatheters, stents or atherectomy devices through guiding c~th~ters. Having a short 25 unreinforced soft tip edge 65 of .5 mm is advantageous because it ~iimini~hes the likelihood of devices snagging during device delivery. Soft tips on guide catheters deflect easily, especially if they are ull~hlrol~;ed. Ul~eillrorced soft tips of two mm or more increase the likelihood of devices snagging during delivery.
Unreinforced soft tips of less than 1 mm reduce the likelihood of a device 30 snagging. Applicant's soft tip 20 having the TEFLON~ liner 40 throughout the soft tip 20 provides increased stiffn~ss which further avoids devices snagging during deployment.

W 096/20750 PCT~US95/16745 The prece~ling specific embo~lim~nf.~ are illll~tr~tive of the practice of the invention. It is to be understood, however, that other expedients known to thoseskilled in the art or disclosed herein, may be employed without departing from the spirit of the invention or the scope of the appended claims.

Claims

1. A catheter comprising:
an elongated core having a unitary lubricious liner (40) and a wire braid reinforcement means (35), the wire braid reinforcement means having a proximal end and a distal end, the lubricious liner (40) having a distal end, an outer diameter and a proximal end, the lubricious liner (40) defining at least one lumen, the lubricious liner (40) having the wire braid reinforcement means (35) over the outer diameter and fused to the lubricious liner (40), the wire braid reinforcement means (35) terminating proximal to the distal end of the lubricious liner (40);
an elongated shaft tube (25) having a distal end and a proximal end, the shaft tube (25) defining a shaft tube lumen, the core extending longitudinally through the shaft tube lumen, the shaft tube (25) being fused to the core;
an elongated transition tube (15) having a distal end and a proximal end, the transition tube defining a transition tube lumen, the core extending longitudinally through the transition tube lumen, the distal end of the shaft tube (25) being fused to the proximal end of the transition tube (15), the transition tube (15) being fused to the core, the transition tube (15) being made of softer material than the shaft tube (25); and an elongated tip tube (20) having a distal end and a proximal end, the tip tube (20) being made of softer material than the transition tube (15), the tip tube (20) defining a tip tube lumen, the distal end of the transition tube (15) being fused to the proximal end of the tip tube (20), characterized in that;
the tip tube (20) forms with the lubricious liner (40) and the and the wire braid reinforcement means (35) a soft tip, the soft tip having a proximal end and a distal end, the lubricious liner (40) and the wire braid reinforcement means (35) extending through the proximal end of the soft tip, the wire braid reinforcement means (35) terminating proximal to the distal end of the lubricious liner (40) and proximal to the distal end of the soft tip, the lubricious liner (40) terminating adjacent to the distal end of the soft tip, the distal end of the tip tube (20) being drawn distally over the distal end of the lubricious liner (40) to form the distal end of the soft tip, the distal end of the tip tube (20) forming a unity rounded edge at the distal end of the soft tip which curves over the distal end of the lubricious liner (40) such that the distal end of the lubricious liner (40) is not exposed, so that the soft tip is structurally secured to at least one of the lubricious liner (40) and the wire braid reinforcement means (35) over substantially the length of the soft tip.

2. The catheter of claim 1 wherein the shaft tube is made from a polymer material exhibiting a hardness in the range of Shore durometer 65D to 75D.

3. The catheter of claim 1 wherein the transition tube is made from a polymer material exhibiting a hardness in the range of Shore durometer 50D to 60D.

4. The catheter of claim 1 wherein the tip tube is made from a polymer material exhibiting a hardness in the range of Shore durometer 25D - 40D.

5. The catheter of claim 1 wherein the shaft tube distal end and the transition tube proximal end have complimentary tapers.

6. The catheter of claim 1 wherein the lubricous liner is made of a fluoropolymer material.

7. The catheter of claim 1 wherein the shaft tube, or transition tube or the tip tube may be made from a polyether block amide copolymer material.

8. The catheter of claim 1 wherein the tip tube is fused to the core between 2 - 3 mm distal to the distal end of the reinforcement means.

9. The catheter of claim 1 wherein the distal end of the wire braid reinforcement (35) means extends into the proximal end of the tip tube (20) for not more than one third of the length of the tip tube (20).

10. The catheter of claim 1 wherein the transition tube has a length of approximately 3.7 cm.

11. The catheter of claim 1 wherein the tip tube has a length of approximately 2.5 mm.

12. The catheter of claim 1 wherein the rounded edge extends approximately .5 mm distally beyond the lubricous liner.

13. The catheter of claim 1 wherein the reinforcement means comprises a wire braid.

14. A method of manufacturing a catheter comprising the steps of:

providing a catheter subassembly having a core comprising a lubricous liner and a reinforcement means, the lubricous liner having a distal end, an outer diameter and a proximal end, the lubricous liner defining at least one lumen, the lubricous liner having the reinforcement means over the outer diameter and fused to the lubricous liner, the reinforcement means terminating proximal to the distal end of the lubricous liner;
placing an elongated shaft tube over the proximal end of the core;
placing an elongated transition tube of softer material than the shaft tube overthe distal end of the core and abutting the distal end of the shaft tube to the proximal end of the transition tube;
placing an elongated tip tube of softer material then the transition tube over the distal end of the core and abutting the distal end of the transition tube to the proximal end of the tip tube such that the distal end of the reinforcement means ends approximately at the proximal end of the tip tube;
placing a tube of heat shrink over at least a portion of the shaft tube, transition tube and tip tube;
heating the heat shrink to fuse the core to the shaft tube, to fuse the transition tube and tip tube, to fuse the distal end of the shaft tube to the proximal end of the transition tube and to fuse the distal end of the transition tube to the proximal end of the tip tube;
removing the heat shrink;
trimming off a portion of the soft tip tubing;
placing a tube of heat shrink over the tip tube such that the heat shrink extends beyond the distal end and beyond the proximal end of the tip tube; and applying heat to the tip tube causing the tip material to flow and the heat shrink to draw the distal end of the tip tube over the distal end of the lubricous liner forming a unitary rounded edge covering the lubricous liner.

15. The method of claim 14 wherein the shaft tube distal end and the transition tube proximal end have complimentary tapers.

16. The method of claim 14 wherein the tip tube has a length of approximately 2.5 mm.

17. The method of claim 14 wherein the transition tube has a length of approximately 3.7 cm. mm.

18. The method of claim 14 wherein the distal end of the reinforcement means ends not less then approximately 2-3 mm proximal to the proximal end of the tip tube and not more then approximately 1/3 of the length of the tip tube from the proximal end of the tip tube.

19. The method of claim 14 wherein the reinforcement means comprises a wire braid.

20. The method of claim 14 wherein the transition tube is made from a polymer material exhibiting a hardness in the range of Shore durometer 50D to 60D.

21. The method of claim 14 wherein the tip tube is made from a polymer material exhibiting a hardness in the range of Shore durometer 25D - 40D.

22. The method of claim 14 wherein the rounded edge extends approximately .5 mm distally beyond the lubricous liner.

23. A method of manufacturing a catheter comprising the steps of:
providing a catheter having a lubricous liner extending longitudinally throughout the catheter, the lubricous liner defining at least one lumen;
placing a tube of heat shrink over the distal end of the catheter such that the heat shrink extends beyond the distal end of the catheter; and applying heat to the heat shrink causing the material at the distal end of the catheter to flow and the heat shrink to draw the distal end of the catheter over the distal end of the lubricous liner thereby forming a unitary rounded edge covering the lubricous liner.

24. The method of claim 14 wherein the rounded edge extends approximately .5 mm distally beyond the lubricous liner.

25. The method of claim 23 wherein the rounded edge extends approximately .5 mm distally beyond the lubricous liner.