||||||III
`US0055451.49A
`11
`Patent Number:
`5,545,149
`(45) Date of Patent:
`Aug. 13, 1996
`
`
`
`l/1992 Pomeranz ................................ 604/280
`5,078,702
`5,160,559 11/1992 Scovil et al..
`... 604/280
`5,221,270 6/1993 Parker .........
`... 604/282
`5,222,949
`6/1993 Kaldany ..........
`... 604/282
`5,234,416 8/1993 Macaulay et al. ...
`... 604/282
`5,254,107 10/1993 Soltesz .................................... 604/282
`OTHER PUBLICATIONS
`Handbook of Common Polymrs, Roff & Scott, editors, CRC
`Press 1971, pp. 209, 216, 218, 222,446,454-455, 600-601.
`Polymer Science 406, Penn State University, fall 1988, pp.
`12-13, section VIII.
`Polyuretous: The Bridge Between Silicone Rubbers and
`Plastics (chart).
`Photograph of 7F SciMed Triguide Sample A with Green
`Transition.
`Primary Examiner-C. Fred Rosenbaum
`Assistant Examiner-Chalin Smith
`Attorney, Agent, or Firm-Hal Patton; Dianne M. F. Plunkett
`57
`ABSTRACT
`Atherapeutic catheter and used in percutaneous transluminal
`coronary angioplasty with the catheter comprising a shaft (5)
`a soft tip assembly. The assembly consists of a transition
`tube (15), a soft tip tube (20), and plug tube (25). The
`assembly is surrounded by a shrink wrap means. An infrared
`source (45) is applied to the interface of the shaft (5) and
`transition tube (15) with the heat being propagated to the
`transition tube (15) and the soft tip tube (20). The transition
`tube (15) is formed of materials having a tensile strength of
`at least 150% of the materials comprising the soft tip tube
`(20).
`
`24 Claims, 4 Drawing Sheets
`
`United States Patent (19)
`Brin et al.
`
`(54)
`
`(75)
`
`(73)
`
`(21)
`22
`
`METHOD OF CATHETER SEGMENT
`ATTACHMENT
`
`Inventors: Dav id S. Brin, West Newbury; Peter
`A. Lunn, Beverly; Stuart R.
`MacDonald, Danvers, all of Mass.
`Assignee: Medtronic, Inc., Minneapolis, Minn.
`
`Appl. No.: 236,766
`Filed:
`May 2, 1994
`Related U.S. Application Data
`
`(63)
`
`(51)
`52)
`58)
`
`56)
`
`Continuation-in-part of Ser. No. 083,840, Jun. 25, 1993,
`abandoned.
`Int. Cl. ... A61M S/32
`U.S. Cl. ............................................. 604/265; 604/282
`Field of Search ..................................... 604/200, 202,
`604/264, 265; 128/658, 656
`References Cited
`U.S. PATENT DOCUMENTS
`6/1975
`3,890,976
`7/1985
`4,531,943
`4551.292 11/1985
`4,563,181
`1/1986
`4,636,346
`1/1987
`4,782,834. 11/1988
`4,863,442 9/1989
`4,886,506 12/1989
`4,899,787 2/1990
`4,917,667 4/1990
`
`Bazell et al. ............................ 604/280
`Van Tassel .............................. 604/280
`Fletcher et al. ......................... 264/139
`Wijayarathna et al. ................ 604/280
`Gold et al. .............................. 264/139
`Maguire et al. ........................ 128/344
`DeMello et al. ........................ 604/282
`Lovgren et al. ........................ 604/280
`Ouchi et al. .....
`... 604/282
`Jackson ..................................... 604/96
`
`5
`v
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`8O
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`35
`
`Z/Z//
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`U.S. Patent
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`Aug. 13, 1996
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`Aug. 13, 1996
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`2O
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`F. G.5
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`U.S. Patent
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`Aug. 13, 1996
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`5,545,149
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`1
`METHOD OF CATHETER SEGMENT
`ATTACHMENT
`
`This is a continuation-in-part of application Ser. No.
`08/083,840 filed on Jun. 25, 1993, now abandoned.
`
`5
`
`FIELD OF THE INVENTION
`The present invention relates to catheters, and more
`particularly, to a method of soft tip attachment.
`
`10
`
`2
`U.S. Pat. No. 4,863,442 to DeMello et al for a "Soft Tip
`Catheter' discloses an embodiment at col. 5, lines 30-52
`wherein a sleeve of shrink film is placed over the polyure
`thane tube and the distal end of the jacket and overlaps the
`shoulder. With the sleeve of shrink film in place, the distal
`end of the assembly is heated to a temperature and for a time
`sufficient to cause the soft polyurethane tube to flow and fill
`the gap along with any other gaps which may exist between
`it and the shoulder, outer surface of the core, and the outer
`surface of the mandrel. The time and temperature is a
`function of the particular polyurethane used. With one
`material tested, the temperature was approximately 320
`degrees for a duration of approximately five minutes. As the
`film shrinks under the application of heat, it will somewhat
`compress the polyurethane and cause it to conform closely
`to the contours of the mandrel. After the assembly cools, the
`mandrel may be removed and the shrink film should be
`stripped from the assembly.
`U.S Pat. No. 4,886,506 to Lovgren et al for a "Soft Tip
`Catheter' discloses a method of achieving a lap joint at col.
`2, ins. 60-62 defining a frusto-conical profile on the distal
`catheter shaft to which the tip is subsequently fused by RF
`welding, resulting in a lap joint. The tip has a size and shape
`adapted to be placed over the tapered portion coaxially, and
`a composition softer than that of the distal end portion that
`is suitable for bonding to the fustoconically-shaped outer
`surface.
`U.S. Pat. No. 4,899,787, issued to Ouchi et al., discloses
`a flexible tube having two or more tube sections which are
`bonded to a tubular core which comprises one or more fabric
`mesh tubes and one or more metallic tubular spirals. The
`tube sections are butted together and then fused to the
`tubular core. A catheter utilizing this tubular core structure
`possesses undesirable stiffness and rigidity because of the
`presence of mesh tubes and metallic tubular spirals at the
`distal end of the catheter shaft. As a result, the tubular core
`poses the danger of puncturing or otherwise damaging a
`vessel as the catheter is manipulated through the vascular
`system.
`U.S. Pat. No. 5,078,702 to Pomeranz for a "Soft Tip
`Catheter' discloses a tip welded to a tubular body. The tip
`has an inner sheath of a rigid polymeric material encapsu
`lated by an outer sheath of a flexible polymeric material. The
`inner sheath of both the body and tip portions are formed
`from the same polymeric material.
`U.S. Pat. No. 5,160,559 to Scovil et al for a "Method for
`Forming a Guide Catheter Tip Bond" discloses setting a
`mating distal end of a tubular member against a mating
`proximal end of a soft, deformable tip to form a butt joint.
`The butt joint is then softened to render the mating proximal
`and distal ends of the deformable tip and tube flowable. The
`tubular member and the deformable tip are then oscillated
`and advanced into one another along alongitudinal axis such
`that the materials of the mating proximal and distal ends
`flow into one another creating a connection zone which
`solidifies to form a lap joint tip bond.
`U.S. Pat. No. 5,234,416, issued to Macaulay et al., dis
`closes a distal soft tip comprising at least two relatively
`short, coaxially disposed flexible tubular elements. The "first
`tubular element' 17 is secured to the "distal section' 13 of
`the catheter shaft, and the "second tubular element' 18
`which is softer than the "first tubular element' 17 is secured
`to the "first tubular element' 17. The "first tubular element'
`17 incorporates a radiopaque filler to make the distal tip
`fluoroscopically observable. See col. 5, In 32-35. The "first
`tubular element' 17 has a durometer in the range of Shore
`
`15
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`20
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`25
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`30
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`35
`
`BACKGROUND OF THE INVENTION
`Catheters are tube-like members inserted into the body for
`diagnostic or therapeutic reasons. One of the therapeutic
`procedures applicable to the present invention is known as
`percutaneous transluminal coronary angioplasty (PTCA).
`This procedure can be used, for example, to reduce arterial
`build-up of cholesterol fats or atherosclerotic plaque. Cath
`eters must have sufficient stiffness 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 of puncturing or otherwise damaging a
`vessel as it twists through the vascular system. It is therefore
`desirable for catheters to have a soft or flexible distal tip.
`Examples of such soft tip catheters are known in the art.
`The trend toward catheters with larger inside diameters
`and softer distal tip segments results, however, in a substan
`tially weaker bond between the soft tip and the distal
`catheter shaft because of the thinner wall thickness and
`lower tensile strength of the softer materials. The following
`methods of tip attachment are known in the art.
`U.S. Pat. No. 4,531,943 to Van Tassel et al for a "Catheter
`with Soft Deformable Tip' discloses an embodiment at col.
`4, lns. 43-47 wherein the tip member comprises a tubular
`sleeve which surrounds and fits by means of a lap joint at the
`distal end of the catheter body and the sleeve extends beyond
`the distal end thereof by a predetermined length.
`40
`U.S Pat. No. 4,551,292 to Fletcher et al for a "Method for
`Making a Catheter with a Soft, Deformable Tip' discloses a
`method of tip construction whereby the tip is heated to
`soften the plastic, then a forming tool is inserted into the
`catheter lumen distal end and advanced to the point where an
`annular protuberance of a predetermined outside diameter is
`forced into the lumen so as to stretch and shape the plastic
`to conform to the forming tool. The distal end is then cooled
`and the forming tool removed, leaving a soft, collapsible
`segment integrally formed at the distal end of the catheter.
`U.S Pat. No. 4,563,181 to Wijayarathna et al for "Fused
`Flexible Tip Catheter' discloses a soft tip formed from a
`blend of the nylon of the body portion with an ester linked
`polyether-polyamide co-polymer which is soft and rubbery
`to render the tip soft to avoid injury to a blood vessel. The
`tip is fused or welded at a butt joint to the tubular body
`which is made of a stiffer nylon.
`U.S Pat. No. 4,636,346 to Gold et al for a "Preparing
`Guiding Catheter' discloses an embodiment in col. 5, lines
`12–20 wherein the tip portion may be an initially separate
`member that is affixed to the elongated tubular body by
`suitable means, such as by heating, by other energy sources,
`and/or by adhesives or the like. Such assembly can be
`assisted 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 enhance the smoothness and
`strength of the joint.
`
`45
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`3
`80A to 100A while the "second tubular element' 18 has a
`durometer in the Shore 70A to 90A range. See col. 6, In
`54-59. The distal end of the catheter shaft has a circumfer
`ential shoulder over which the proximal end of the first
`tubular element, which is stepped to mate with the shoulder,
`is placed. The proximal end of the "" tubular element"
`18 is abutted against the distal end of the "first tubular
`element' 17. The short tubular elements are joined with the
`distal end of the catheter shaft by means such as melt fusing
`or adhesive bonding.
`The joints employed to bond the tubular elements of the
`416 Macaulay patent suffer from the same problems as the
`above-referenced prior art. The overlappingjoint of the "first
`tubular element' 17 with the "distal section' 13 of the
`catheter shaft, similar to the '943 Van Tassel patent, supra,
`is undesirable because it creates a stress concentration area
`at the distal end of the catheter shaft in a plane perpendicular
`to the longitudinal axis of the catheter shaft. The effect of
`this stress concentration is an unacceptably low bond
`strength between the catheter shaft and the "first tubular
`element' 17 when the wall thickness of the catheter shaft is
`less than 0.3 min. Further, the butt joint design of the
`"second tubular element' 18 with the "first tubular element'
`17, similar to the 181 Wijayarathna patent, supra, does not
`yield adequate bond strength because of the low surface area
`of contact and the stress concentration area at the junction of
`the "first and second tubular elements' 17 and 18 in a plane
`perpendicular to the longitudinal axis of the catheter shaft.
`The effect of the low surface area and the stress concentra
`tion is inadequate bond strength when the catheter shaft wall
`thickness is less than 0.3 mm and when soft, typically low
`tensile strength materials, such as Shore 70A to 90A
`TECOFLEXOR) are used for the 'second tubular element' 18.
`The tensile strength ratio of the "first tubular element” 17
`TECOFLEXQ) of EG93A-HT60 compared to the "second
`tubular element' 18 TECOFLEXCE) of EG80A is 126% as
`derived from the manufacturer's specification.
`
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`5,545,149
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`longitudinally thereby colliding all segments which results
`in an improved lap joint. With applicant's invention it is not
`necessary to use prior art methods such as grinding the
`exterior surface of the catheter body on a centerless grinder
`to create a Zone of lesser thickness proximate to the distal tip
`of the catheter and form a lap joint by fitting the preformed
`soft tip member onto the end portion where it is held in place
`by a suitable adhesive. Such a process is somewhat slow and
`considering the cross-sectional dimensions of angiographic
`catheters, slight variations in the wall thickness which occur
`during the centerless grinding operation can render the
`resulting catheter unacceptable, decrease the manufacturing
`yield and increase the manufacturing cost.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is the preassembly plan view of the distal end of
`a guiding catheter constructed according to the invention;
`FIG. 2 is the molded tip assembly of FIG. 1;
`FIG. 3 is the molded tip assembly of FIG. 2 with the heat
`shrink removed;
`FIG. 4 is the molded tip assembly of FIG. 3 with the
`mandrel removed and the tip cut to length;
`FIG. 5 is the enlarged longitudinal cross section of the
`distal end portion of the catheter; and
`FIG. 6 is the plan view of the infrared assembly.
`FIG. 7 is a cross-sectional view of the bonded assembly
`of the catheter shaft, the transition segment and the soft tip
`segment.
`
`DETALED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`Refer to FIG. 1. To bond a soft tip to the distal end of a
`guiding catheter shaft 5, insert a TEFLONG) coated stainless
`steel mandrel 30 into the distal end of the shaft 5 with
`approximately 15.2 cm or 6 inches of mandrel 30 extending
`beyond shaft 5. Mandrel 30 has an outer diameter approxi
`mating the inner diameter of the shaft 5. Advance a segment
`of 65D Durometer transition tubing 15 over the mandrel 30
`and abut the 65D transition tubing 15 to the distal end of the
`catheter shaft 5. The 65D transition tubing 15 can be made
`of polyurethane loaded with radiopacifier such as that from
`Dow chemical company. The 65D transition tubing 15 may
`have a length of approximately 2.5 mm, a wall thickness of
`0.013 inches (0.33 cm) and an inner diameter ranging from
`a minimum of 0.057 inches (0.14 cm) to a maximum of
`0.110 inches (0.28 cm). The catheter shaft 5 can be made of
`75D tubing.
`Next, advance a segment of 80A Durometer soft tip tubing
`20 such as a clear polymer to which titanium dioxide has
`been added, over the mandrel 30 and abut the proximal end
`of the 80A soft tip tubing 20 to the distal end of the 65D
`transition tubing 15. The 80A tip tubing 20 can be made of
`polyurethane. The 80A tip tubing 20 may have a length of
`approximately 0.5 cm with a tolerance of plus or minus 1
`mm, a wall thickness of 0.013 inches (0.33 cm) and an inner
`diameter ranging from a minimum of 0.057 inches (0.14 cm)
`to a maximum of 0.110 inches (0.28 cm). The 0.5 cm length
`was chosen for handling convenience during the trimming
`process.
`Next, advance a segment of approximately 2.5 mm of
`75D plug tubing 25 over the mandrel 30 and abut the
`proximal end of the 75D plug tubing 25 to the distal end of
`the 80A soft tip tubing 20. The 75D plug tubing 25 is made
`of polyurethane and may have a length of approximately 2.5
`
`SUMMARY OF THE INVENTION
`The present invention addresses the problem created by
`the trend toward catheters with larger inside diameters and
`softer distal tip segments. This trend results in a substantially
`weaker bond between the soft tip and the distal catheter shaft
`due to thin catheter shaft walls of less than 0.3 mm and to
`the lower tensile strength of the softer tip materials. Appli
`cants address this problem by employing a transition seg
`ment, a heat shrinkable FEPTEFLONGR) (polytetrafluoroet
`hylene or PTFE) and an infrared radiation source. The
`transition segment is selected from a group of thermoplastic
`elastomers having an ultimate tensile strength of at least 45
`MPa. The transition segment also has tensile strength of at
`least 150% of the materials comprising the soft tip tubing.
`During assembly, 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 attached to the transition
`tubing, and the "plug' tubing which is attached to the soft tip
`tubing for ease of handling during manufacture and into
`which a support mandrel is inserted. All three segments are
`surrounded by a tube of heat shrink. The infrared source acts
`upon 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 infrared source causes the catheter shaft, the transi
`tion tubing, the soft tip tubing and the plug tubing to become
`flowable while the heat shrink contracts both radially and
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`5,545,149
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`mm, a wall thickness of 0.013 inches (0.33 cm) and an inner
`diameter ranging from a minimum of 0.057 inches (0.14 cm)
`to a maximum of 0.110 inches (0.28 cm).
`Finally, slide a segment of approximately 10 cm of
`TEFLONG) polytetrafluoroethylene (PTFE) heat shrink tub
`ing 10 over the mandrel and all tubing segments (65D
`transition tubing 15, 80A soft tip tubing 20, 75D plug tubing
`25) and center the heat shrink tubing 10 longitudinally over
`the 65D transition tubing 15. Use heat shrink tubing as for
`example, that from Zeus Industrial.
`The manufacturing process has three main phases, heat
`ing, cooling and cutting. To begin the heating process, insert
`the FIG. 2 assembly into a clamping fixture, preferably one
`with a Programmable Logic Controller (PLC), as for
`example, that manufactured by General Electric. The PLC
`will advance the infrared source over the center of the
`assembly and execute a timed exposure and cooling cycle.
`An example of such an infrared source 45 is the 25 ohm
`one-halfinch (1.27 cm) Glow-Ring IR radiantheater assem
`20
`bly as for example, that from Eraser, Inc., part number AH
`1901 which is depicted in FIG. 6. It includes an aluminum
`heat sink/socket assembly, Eraser part number IH3H6 and 2
`IR elements, Eraser part number IH6515. The following
`steps will accomplish this. Activate the "start” button on the
`PLC to begin execution. The infrared source 45 powers up
`to processing voltage of approximately 50 volts. Insert the
`FIG. 2 molded tip assembly into the clamping assembly. The
`operator activates the "cycle on' button and aligns the 65D
`transition tubing 15 with a marker positioning the infrared
`source 45 centrally over the 65D transition tubing 15. The
`PLC clamps the FIG. 2 molded tip assembly and positions
`the infrared source 45. The PLC timer counts to the heating
`process value of approximately 30 seconds such that suffi
`cient heat is propagated to allow the shaft 5, transition tube
`35
`15, tip tube 20, and plug tube 25 to blend and flow into one
`another while minimizing concentricity loss. The PLC
`removes the infrared source 45 from the FIG. 2 molded tip
`assembly upon the counter reaching the heating process
`value.
`To facilitate bonding the materials, the transition tubing
`15 receives greater radiation exposure than the soft tip
`tubing 20 which compensates for the differences in the two
`materials' melt characteristics. The infrared radiation ele
`ments are chosen to allow sufficient concentration of energy
`on the interface of the transition tubing 15 and catheter shaft
`5 materials, which have higher melt temperatures than the
`soft tip 20 material. This renders these materials flowable
`without material degradation from excessive radiation expo
`sure to the soft tip 20 material. The transition tubing 15
`material is chosen so that, in catheter wall thicknesses
`representative of current market trends, sufficient distal soft
`tip tensile strength is maintained while providing the req
`uisite level of tip softness. Furthermore, the transition tubing
`15 must be sufficiently compatible with the catheter shaft
`material and with the soft tip 20 material so that the
`materials may be blended together by the application of heat
`and pressure at the two interfaces while attaining adequate
`interface bond strengths.
`When the heating cycle is complete, the PLC activates air
`cooling while counting to a cooling process value of
`approximately 20 seconds at an ambient air temperature
`with 80 p.s.i. thereafter deactivating the air cooling and
`releasing the FIG. 2 molded tip assembly from the clamp
`fixture. Cooling can be accomplished using a needle valve.
`The cutting process consists of the operator removing the
`FIG. 2 molded tip assembly from a clamp fixture such as
`
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`Carr Lane's part number CFO-01188A and CL-H00-PTC,
`removing the heat shrink tubing 10 with a razor blade as in
`FIG.3, and cutting the FIG. 2 molded tip assembly to length
`as in FIG. 4. The distal end is trimmed back to a point within
`the 80A soft tip tubing in a cutting block, resulting in a tip
`length of 2.5 mm distal to the 2.5 mm 65D transition tubing
`15. The TEFLONG) (polytetrafluoroethylene or PTFE)
`coated mandrel 30 is removed from the inside of the now
`bonded assembly as in FIG. 4. FIG. 5 shows the enlarged
`longitudinal cross section of the distal end portion of the
`catheter. The wire braiding 35 in the shaft may stop before,
`or abut the transition tube 15.
`The infrared source 45 is placed over the interface of the
`65D transition tubing 15 and catheter shaft 5. Because the
`interface of the 65D transition tubing 15 and 80A soft tip
`tubing 20 is off-center from the infrared source, it receives
`less direct radiation than the interface of the 65D transition
`tubing 15 and catheter shaft 5. Thus the infrared source 45
`acts upon the 65D transition tubing 15 and catheter shaft 5
`interface where greater radiation absorption is required to
`render these materials flowable. Materials thin enough to be
`used as the 80A soft tip tubing 20 would degrade from
`excessive radiation exposure if the infrared source were
`applied directly. The plug tubing 25 must have a higher melt
`temperature than the 80A soft tip tubing 20 so that it will
`continuously surround the mandrel 30 without melting
`under the heat propagation. Once this function is served, the
`75D plug tubing 25 will be removed.
`The resulting heat shrink tubing 10 contraction, when
`coupled with heating the tip materials which causes them to
`expand, results in a local high pressure zone in the tip
`materials, causing them to blend and flow into one another.
`A lap joint between the materials is produced. Using 65D
`transition tubing 15, which is stronger than the 80A soft tip
`tubing 20, allows thinner walls to be bonded with the shaft,
`which because of the presence of wire braid 35 and
`TEFLONQ (polytetrafluoroethylene or PTFE) for reinforce
`ment, has a thinner polymer wall thickness. The 65D tran
`sition tubing 15, having a larger wall than the catheter shaft
`5, because it contains no wire or TEFLONGR), offers an
`improved bond surface for the 80A soft tip tubing 20.
`Referring to FIG. 7, a cross-sectional view of the com
`pleted assembly of FIG. 4 is shown. The catheter shaft 5 is
`comprised of principally three layers as shown in FIG. 7: a
`lubricous TEFLONGR) liner 40, a composite layer of wire
`braid 35 and polymer, and an outer jacket polymer 80. The
`distal end of the catheter shaft 5 is shown bonded to the
`proximal end of the transition tubing 15 and the distal end
`of the transition tubing 15 is shown bonded to the proximal
`end of the soft tip tubing 20.
`The selection of materials for the transition tubing 15 is
`based upon considerations of tensile strength, processing
`temperature compatibility with the polymers comprising the
`catheter shaft 5, and flexural modulus. A tensile strength in
`excess of 45 MPa is necessary to achieve a minimally
`acceptable bond strength of 18N between the catheter shaft
`5 and the transition tubing 15 when the wall thickness of the
`catheter shaft is less than 0.3 mm. This is because of the
`compromised bonding between the catheter shaft 5 and the
`transition tubing 15 caused by the presence of the wire braid
`in the composite layer 70 and by the TEFLONG) in the
`lubricous liner 40. The 65D transition tubing 15 does not
`bond to the lubricous liner 40 of TEFLONGR)because
`TEFLONG) does not adhere well to any materials. The 65D
`transition tubing 15 does not bond to the wire in the wire
`braid composite layer 35 which is composed of wire and a
`polymer. This is a consequence of the primary bonding
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`mechanism which is melt fusing. Since the wire cannot be
`melt fused to the 65D transition tubing 15, bonding between
`the 65D transition tubing 15 and the wire braid composite
`layer 35 is limited to the interstitial sites which are occupied
`by the 75D polymer of the outer jacket 80. The 65D
`transition tubing 15 bonds well to the 75D polymer of the
`outer jacket 80 because of melt compatibility. Because
`primary bonding occurs only at the interface of the 65D
`transition tubing 15, and because the 75D polymer of the
`outerjacket 80 is only approximately one third of the overall
`catheter wall thickness, the transition tubing 15 must be
`chosen for its tensile strength.
`w
`The cross-sectional area of the bond between the mate
`rials of the 65D transition tubing 15 and the polymer of the
`outer jacket 80 such as 75D Polyurethane is II/4 (0.091°
`0.085)=8.3e-4 in’. The cross-sectional area of the bond
`between the materials of the 65D transition tubing 15 and the
`80A polyurethane soft tip tubing 20 is II/4 (0.091°–0.072)=
`24.3e-4 in’. These cross-sectional areas can be related to the
`force required to break the bond with an axial stress on the
`bond. Force equals the average tensile strength multiplied by
`the area. The average tensile strength of 65D is 6800 lbs/in.
`The average tensile strength of 80A is 4200 lbs/in’. The
`force required to break the bond between the 75D polymer
`of the outer jacket 80 and the 65D transition tubing 15 is
`6800 psi 8.3e-4 in-5.6 lbs. Converted to SI units, the bond
`strength is 25N. The force required to break the bond
`between the 65D transition tubing 15 and 80A polyurethane
`soft tip tubing 20 is 4200 psi 24.3e-4 in’=10.2 lbs. Con
`verted to SI units the bond strength is 45N. Without appli
`30
`cant's transition tubing 15, bonding the 80A polyurethane
`soft tip tubing 20 directly to the 75D polymer of the outer
`jacket 80 yields a bond strength of 4200 lbs/in’* 8.33e-4=
`3.5 lbs or 15.5N in SI units.
`For the transition tubing 15 to bond adequately to the
`outer jacket polymer 80, the transition tubing 15 must have
`a processing temperature which is compatible with the outer
`jacket polymer 80. Further, the transition tubing 15 must
`exhibit sufficient flexibility to facilitate the manipulation of
`the catheter shaft 5 through the patient's vasculature. Suf
`ficient flexibility is achieved where the flexural modulus of
`the transition tubing 15 is less than 250 MPa. To meet the
`above requirements, the transition tubing 15 is comprised of
`a Shore 65D PELLETHANEQ) polyurethane. This material
`has a compatible processing temperature to the outer jacket
`45
`polymer 80, which is comprised of Shore 75D PELLE
`THANE(E) polyurethane.
`The selection of materials for the soft tip tubing 20 is
`based upon considerations of flexural modulus and tensile
`strength. The flexural modulus is an indicator of the ability
`of the polymer to deflect adequately when the soft tip tubing
`20 contacts a wall of the patient's vasculature. The tensile
`strength must be sufficient to ensure an 18N minimum bond
`strength between the soft tip tubing 20 and the transition
`tubing 15. For a catheter wall thickness of less than 0.3 ram,
`55
`a polymer exhibiting a minimum tensile strength of 30 MPa
`is required for the soft tip tubing 20. These criteria are met
`with a material such as Shore 80A PELLETHANEQ) poly
`urethane.
`It is noteworthy that the minimum tensile strength of the
`material comprising the soft tip tubing 20 is significantly
`less than that required for the transition tubing 15. This is
`because of the compromised bonding with the multi-layer
`catheter shaft 5 which requires a higher tensile strength
`material to compensate for the poor bonding which occurs
`between the transition tubing 15 and both the composite
`layer 70 and the lubricous liner 75. Where the transition
`
`8
`tubing 15 is not comprised of multiple layers as is the
`catheter shaft 5, the soft tip tubing 20 is bonded to the entire
`wall thickness of the transition tubing 15. Thus, a lower
`tensile strength is allowable to achieve the minimum bond
`strength of 18N. To meet the criteria of requisite tensile
`strength, materials should be chosen for the transition tubing
`15 and soft tip tubing 20 with a tensile strength ratio greater
`than 1.55.
`The preceding specific embodiments are illustrative of the
`practice of the invention. It is to be understood, however,
`that other expedients known to those skilled in the art or
`disclosed herein, may be employed without departing from
`the spirit of the invention or the scope of the appended
`claims.
`
`No.
`
`Component
`
`5
`10
`15
`20
`25
`30
`35
`40
`45
`50
`55
`60
`65
`80
`
`Catheter Shaft
`Heat Shrink Tubing
`65D Transition Tubing
`80A Soft Tip Tubing
`75D Plug Tubing
`Mandrel
`Wire Braid Composite Layer
`TEFLON (R) Liller
`infrared source
`Shaft Lumen
`Transition Tube Lunen
`Tip Tube Lumen
`Plug Tube Lumen
`Outer Jacket Polymer
`
`What is claimed is:
`1. A catheter comprising:
`(a) an elongated shaft having an inner diameter, a proxi
`mal end and a distal end, the shaft defining at least one
`lumen, the shaft having a lubricous liner coating the
`inner diameter of the shaft;
`(b) an elongated transition tube having a proximal end and
`a distal end, the transition tube defining at least one
`lumen, the proximal end of the transition tubing being
`affixed to the distal end of the shaft, the transition tube
`being generally free of the lubricous liner;
`(c) an elongated tip tube having a proximal end and a
`distal end, the tip tube defining at least one lumen, the
`proximal end of the tip tube being affixed to the distal
`end of the transition tube and the tip tube being made
`of materials having a lower melt temperature than the
`transition tube, the tip tube being free of the lubricous
`liner; and
`(d) the elongated transition tube being formed of materials
`having a tensile strength of at least 150% of the
`materials comprising the elongated tip tube.
`2. A catheter according to claim 1 wherein the shaft
`consists of 75D durometer tubing.
`3. A catheter according to claim 1 wherein the transition
`tube is approximately 2.5 mm long.
`4. A catheter according to claim 1 wherein the transition
`tube is made of 65D Durometer polyurethane loaded with
`radiopacifier.
`5. A catheter according to claim 1 wherein the transition
`tube is selected from a group of thermoplastic elastomers
`having a tensile strength of at least 45 Mpa.
`6. A catheter according to claim 1 wherein the tip tube is
`approximately 0.5 cm long with a tolerance of plus or minus
`1 min.
`7. A catheter according to claim 1 wherein the tip tube is
`made of a clear polymer to which titanium dioxide has been
`added.
`
`35
`
`40
`
`50
`
`60
`
`65
`
`Page 9
`
`Medtronic Exhibit 1452
`
`

`

`9
`8. A catheter according to claim 1 having an elongated
`plug tube having a proximal end and a distal end, the plug
`tube defining at least one lumen, the proximal end of the
`pl