Guidewire extension system with tactile connection indication

A guidewire extension system including a guidewire and an extension wire is disclosed. The system includes female and male connector segments located on the proximal end of the guidewire or the distal end of the extension wire. The hollow female connector segment, in one embodiment, includes a radial lip which intersects with at least one, i.e., one or more, lateral slots. The male connector segment includes an external groove. When the male connector is inserted into the female connector segment, the slots are expanded and the lip snaps into the groove providing a tactile indication that connection is completed. No restriction or frictional fit is created. The guidewire and extension wire are freely rotatable with respect to each other and can be multiply connected and disconnected. Methods of catheter exchange with tactile indication of guidewire extension wire connection are disclosed.

FIELD OF THE INVENTION
 The present invention relates in general to the field of guidewires.
 Guidewires are used to position catheters in exploratory procedures,
 diagnosis, and treatment of various medical conditions. More particularly,
 this invention relates to a guidewire extension system for connecting or
 coupling a guidewire, primary or initial wire to an extension or secondary
 wire during a medical procedure.
 BACKGROUND OF THE INVENTION
 Guidewires are used in various medical procedures to position medical
 devices at desired locations within a patient's vascular system.
 Guidewires, which are steerable, are inserted and maneuvered through the
 patient's vasculature to a previously chosen location. Once in place, the
 guidewire provides the means to place a non-steerable device, such as an
 over-the-wire catheter, at the chosen vascular site. For example, a
 catheter is slid over the guidewire until the catheter, or some working
 portion thereof, is positioned within the vasculature at the desired
 location. Generally speaking, guidewires of a standard length are longer
 than the non-steerable devices with which they are used to permit
 independent movement of the device and the wire.
 Angioplasty is one interventional procedure where a guidewire is often
 used. In angioplasty a dilatation catheter having an inflatable balloon
 structure is used to compress occlusive or blockage material against the
 sides of a vessel, thereby permitting (ideally) circulation to be
 reestablished. In preparatory procedures, the site of a vascular
 restriction, occlusion or stenosis is identified. In the usual procedure,
 the guidewire is inserted into the patient's femoral artery and maneuvered
 or steered to the location of the restriction. Maneuvering of the
 guidewire is facilitated by a video X-ray device which allows the
 physician to observe the movement of the guidewire's distal tip. The
 guidewire distal tip generally comprises a radiopaque metal to enhance
 X-ray viewing. A dilatation catheter then is inserted over the guidewire
 so that its working segment is located adjacent the restriction. Generally
 this means that the catheter balloon is positioned adjacent the vascular
 restriction or blockage.
 During a simple angioplasty procedure, the dilatation catheter balloon is
 inflated to open the restriction, and then is removed along with the
 guidewire. However, complications sometimes arise which prevent the
 physician from completing this simple procedure. Occasionally the balloon
 catheter malfunctions. Sometimes a larger (or smaller) balloon is required
 further to dilate the vascular restriction, or another device or other
 type of catheter is needed to remove vascular material. For whatever the
 reason, the guidewire extension system of this invention is used when the
 catheter, or other such device, has to be removed and replaced with
 another device or catheter.
 In the usual procedure to exchange catheters, the guidewire is removed from
 the patient, leaving the catheter in the vascular system. An exchange wire
 is inserted through the catheter and the catheter removed, leaving the
 exchange wire in place. The new catheter is inserted over the exchange
 wire and the exchange wire removed and replaced with the guidewire.
 It is desirable to keep the guidewire in the patient's vasculature for
 various reasons. One reason is that the initial placement of the guidewire
 requires extensive, time consuming, manipulation. Removal and
 repositioning of the guidewire would be equally time consuming, possibly
 requiring a patient to be exposed to additional drugs, radiation, and, in
 general, additional trauma. It is also of importance that once the
 guidewire has been steered to a position across a lesion, that the crossed
 lesion position not be lost by removal of the guidewire. Guidewires
 removed from a crossed lesion may induce spontaneous vascular restriction
 or closure making repositioning of the guidewire difficult if not
 precluded.
 In those cases where catheter exchange is desired, the physician would
 simply prefer to remove the catheter over the guidewire, leaving the
 guidewire positioned in the patient. However, to permit catheter exchange,
 a guidewire over which a catheter is to be exchanged must be sufficiently
 long to allow the physician to grip a portion of the wire as the catheter
 is being withdrawn over the guidewire. This requires the guidewire to be
 long enough to provide an external portion longer than the catheter in
 addition to the guidewire portion remaining in the patient.
 Unfortunately, a guidewire of sufficient length to provide suitably long
 external and internal portions has inferior handling characteristics,
 thereby making more difficult the steering and maneuvering manipulations
 needed for guidewire placement. The added length also imposes itself on
 the usually cramped vascular suite thereby causing distractions from other
 support activities. It is for these reasons that guidewires are usually
 only slightly longer than balloon catheters, e.g., 20-50 centimeters
 longer, and that a much longer exchange wire is used only with exchange
 procedures.
 Illustrating the above, a dilatation catheter has a shaft length in the
 range of about 120 cm to about 150 cm, a suitable guidewire for such a
 catheter would have a length in the range of about 150 cm to about 180 cm
 and an exchange wire would have a length in the range of about 260 cm to
 about 300 cm. As can be imagined from the above, utilization of an
 exchange wire in an exchange wire procedure is complicated and time
 consuming. This invention simplifies catheter exchange and eliminates the
 need to use an exchange wire.
 A recent development involves coupling or connecting a second length of
 wire, sometimes called an extension wire or secondary wire, to the
 exposed, proximal end of a positioned guidewire. The secondary wire length
 should be sufficient to allow the catheter to be withdrawn while leaving
 the primary or lesion-crossing guidewire positioned within the patient's
 coronary or peripheral vasculature. Various approaches have been suggested
 for effecting the attachment of an extension wire to a guidewire.
 In one approach, such as that described in U.S. Pat. No. 4,922,923 to
 Gambale et al., a guide wire and an extension are joined together by
 crimping. A special crimping tool is disclosed in the Gambale et al., '923
 patent. A drawback of this approach is that once the wires have been
 crimped, the connection therebetween is substantially permanent, and the
 extension wire cannot be detached from the guidewire except by severing
 it, e.g., by cutting.
 Instead of crimping the guidewire to the extension wire, attempts have been
 made to engage the extension wire to the guidewire frictionally. Such
 attempts are described, for example, in U.S. Pat No. 5,113,872 to
 Jahrmarkt et al., and related U.S. Pat No. 5,117,838 to Palmer et al.
 These two patents disclose a guidewire extension system in which the
 distal end of the extension wire comprises a small diameter tube in which
 there is disposed a small diameter, open pitch, flat wire coiled spring.
 The proximal end of the guidewire has a reduced diameter portion which is
 inserted into the tube assembly to complete the connection. The reduced
 diameter proximal end of the guidewire is slightly larger than the
 internal diameter of the coiled spring of the extension wire, thereby
 creating a frictional engagement when one is inserted into the other.
 Palmer et al. disclose the utilization of a swivel joint for minimizing
 twisting of the extension guidewire when connecting or disconnecting it
 from the extension wire. A device as described in these two patents would
 be very difficult to manufacture reliably and apparently requires an
 alignment tool to ease insertion.
 U.S. Pat No. 4,875,489 to Messner et al., discloses an extendable guidewire
 in which concentric tubular segments are secured to one or the other of
 the sections to be connected. The inner tubular segment has a longitudinal
 slot therein which permits it to expand when a cooperating male portion is
 inserted therein. The outer tubular member of the connector assembly
 restricts the expansion of the inner tubular member as the male portion is
 inserted therein.
 U.S. Pat. No. 4,846,193 to Tremulis et al., disclose a guidewire having
 first and second telescopically extendable sections movable between
 axially extended and retracted positions. No disengagement of the
 guidewire and extension wire is disclosed.
 U.S. Pat. No. 4,966,136 to Kraus et al., discloses an internally threaded
 female connection member secured to the distal end of the extension wire.
 The internally threaded female connection member is disclosed to be freely
 rotatable with respect to the extension wire with securement thereto by
 means of a collar. The body of the extension wire has a distal enlargement
 which cooperates with the collar to permit it to be freely rotated. The
 female connection member of the extension wire cooperates with a threaded
 male portion located on the proximal end of the guidewire. The mechanism
 disclosed by Kraus et al., requires the difficult step of threading the
 segments into each other. Threading pieces having the diameters of a
 guidewire and an extension wire into each other can be difficult to
 accomplish, especially under operating room conditions.
 U.S. Pat. No. 4,827,941 to Taylor et al. discloses a guidewire extension
 system employing a tubular female connector portion on one wire and a
 cooperating male portion on the other. The connecting male portion has an
 effective diameter in one radial dimension which is slightly larger than
 the inner diameter of the tubular portion. In a preferred practice, the
 male end portion of the Taylor et al. guidewire has an undulating shape,
 which, when inserted into the tube creates an interference friction fit.
 U.S. Pat. No. 5,247,942 to Prather et al. discloses a guidewire with a
 swivel. The Prather et al. invention provides for permanent connection of
 a main part and an extension part. A swivel is included in the system to
 permit the permanently affixed parts to be rotated with respect to each
 other to enhance steerability of the main or guidewire segment. The
 Prather '942 structure has the same drawback as the Gambale '923 system
 discussed above.
 U.S. Pat. No. 5,246,009 to Adams discloses a complicated guidewire assembly
 utilizing an inner core wire and an outer tube. Torque transmission is an
 aspect of the Adams invention.
 U.S. Pat. No. 5,271,415 to Foerster et al. describes a guidewire extension
 system comprising a tubular outer body with guidewire and extension wire
 elements, e.g., helically wound wires, therein. The device of Foerster et
 al. has the same disadvantage as that of the Kraus et al. '136 patent,
 i.e., the interconnect step requires threading of the parts into each
 other. Moreover, the device described by Foerster et al., with brazed
 wires inside a tubular structure, may be difficult to manufacture.
 The guidewire extension systems discussed above all have one or more
 drawbacks. Some are difficult or tedious or intricate to engage and
 disengage. Others do not disengage at all. While frictional engagement
 overcomes the disadvantages of crimping, disengagement may occur too
 easily. Problems of discontinuity at the guidewire/extension wire
 connection, e.g., kinking, have been experienced with some systems. Some
 connector systems are difficult or expensive to build, especially in
 smaller diameter sizes. Moreover, prior extendable wires for use in
 coronary angioplasty procedures have been found to be unsuitable in
 peripheral arteries because the connections are not sufficiently strong.
 Further, some connections have larger diameters than the rest of the
 guidewire system. This may cause snagging of, e.g., over-the-wire
 catheters. It also means that the catheter with which such connection
 system is used must have a larger internal diameter lumen than would be
 necessary were a smaller diameter coupler employed.
 Accordingly, a principal object of the present invention is to provide a
 guidewire extension system which is reliable, easy to use, and easy to
 manufacture, particularly in smaller diameter, coronary sizes.
 Another object of the present invention is to provide a guidewire extension
 system which does not require that either the guidewire or extension wire
 be rotated when attaching one to the other, i.e., they can be
 non-rotatively coupled. It is advantageous that the guidewire be held
 stationary because the guidewire is located within the patient's blood
 vessel where unnecessary movement can induce trauma. It is also
 advantageous to have the majority of the length of the extension wire held
 stationary (e.g., by retention within a carrier structure) during the
 connection process. Having the extension wire self-contained in a tubular
 carrier package allows medical personnel to concentrate upon engaging the
 two wires using the present extension system. An uncontained extension
 wire is awkward, and thus complicates the process of effecting a
 guidewire/extension wire union during a medical procedure.
 It is a further object of this invention to provide an easily attachable
 (and reattachable) and easily detachable guidewire extension system which
 has a readily identifiable tactile sensation, e.g., a "snap", when the
 system components are affirmatively attached, engaged, or coupled.
 It is still a further object of the present invention to provide a
 guidewire extension system which has substantially the same flexibility
 and pushability at its connection as that of the remainder of the length
 of the guidewire. The system provides an advantageously controllable
 coaxial alignment of the guidewire and extension wire.
 It is yet another object of the present invention to provide a unitized
 guidewire extension system having a substantially uniform, smooth,
 continuous outer diameter or profile along the guidewire, connector, and
 extension wire. A smooth, continuous transition in external profile from
 the distal end of the guidewire to the proximal end of the extension wire,
 especially over the connector segment, permits an over-the-wire catheter
 to be positioned by use of the guidewire/extension wire without getting
 caught. Methods of manufacturing an extension system of this invention and
 methods of using a system of this invention also are disclosed.
 BRIEF SUMMARY OF THE INVENTION
 Briefly, in one aspect, the present invention is an extension system for
 affirmatively connecting the proximal end of a guidewire to the distal end
 of an extension wire. In its connected form, the entire structure is
 sometimes referred to herein as an exchange wire. In one practice, a
 tactile "snap" is experienced by the user when guidewire/extension wire
 connection or docking is achieved.
 In accordance with one aspect of the present invention, there is provided a
 coupler for a guidewire/extension wire system, the coupler comprising a
 male segment and a cooperating female segment. The coupler of this
 invention permits multiple coupling and decoupling, as needed, of the
 guidewire/extension wire to which it is attached. The male and female
 segments are fixedly attached to one or the other of the distal end of the
 extension wire or the proximal end of the guidewire, and yet the system
 permits either or both of the guidewire/extension wires to be freely
 rotated with respect to each other without the structural complication of,
 e.g., a separate swivel.
 The female coupler segment of this invention comprises a hollow, elongate
 sleeve, the sleeve having opposite ends and a sleeve wall which defines
 inside and outside sleeve diameters, one of said sleeve ends having an
 inside diameter such that it can be firmly attached to one of said
 guidewire or said extension wire. The sleeve wall has an interior reduced
 diameter zone, segment, bead or lip located (in a preferred practice)
 approximately midway between the opposite ends of the sleeve. Passing
 through the reduced diameter zone is at least one, i.e., one or more axial
 or lateral slots or slits. The slot(s) or slit(s) of this invention pass
 entirely through the sleeve wall. In a preferred practice of this
 invention, the aforementioned female coupler segment reduced diameter zone
 is created by roll-forming a segment of formable hypotube, i.e., by
 rolling a bead or dent into the sidewall of a segment of hypotube. In one
 practice of this invention, a plurality of axial slots pass through the
 reduced diameter zone. In a further preferred practice, a single axial
 slot passes through the reduced diameter zone or bead, generally
 perpendicular to its plane or diameter.
 The male coupler segment of this invention comprises an elongate member
 located on the other of the guidewire or extension wire. The elongate
 member has an exterior surface and opposite ends which are referred to
 herein, as insertion or leading and following or connection ends,
 respectively. The insertion or leading end of the elongate member is the
 first portion of the elongate member to enter the female sleeve in the
 coupling process. The male coupler segment is affixed to the proximal end
 of the guidewire or the distal end of the extension wire, as appropriate.
 Several attachment locations and methods of attachment are discussed
 below. The exterior surface of the elongate member defines at least a
 portion of a radial groove and an annular shoulder in the following end,
 the groove having a diameter which cooperates with the female coupler
 segment bead so that when said male member is inserted into said female
 segment, the bead passes or slides along the exterior surface of the male
 member in a slightly separated position, passes over said shoulder and
 returns to a non-separated position within the groove or notch. In this
 manner, the female coupler segment is retained substantially coaxially
 along the male coupler segment after insertion. Coupling occurs with a
 tactile sensation that insertion is completed, e.g., with an identifiable
 "snap."
 In a further practice, the outside diameter of the male coupler segment, as
 defined by its exterior surface, is less than the inside diameter of the
 female coupler sleeve, leaving an annular space therebetween and
 precluding a possible restriction or frictional interaction between the
 cooperating segments.
 In yet a further preferred practice, the male member has a tapered
 insertion end, permitting easy insertion of said male member into the
 female coupler sleeve.
 A guidewire extension system of this invention can be used to connect an
 otherwise conventional extension wire to a steerable guidewire having a
 plurality of multifilar, oppositely wound coils. Of course the guidewire
 also may have only a single coil, depending upon application. For smaller
 diameter guidewire applications, e.g., 0.014 in. diameter coronary wires,
 a guidewire core having no coil at all may be used.
 In another practice, the female segment is disposed on the distal end of
 the extension wire and the male segment is disposed on the proximal end of
 the guidewire.

DETAILED DESCRIPTION OF THE INVENTION
 One of the advantages of this invention is that the male member and the
 female coupler are conveniently coupled and decoupled using insertion and
 withdrawal forces easily applied by medical personnel. They are not
 permanently affixed to each other and no restriction or frictional fit is
 created. Neither of the male nor the female coupler segments are threaded,
 thereby eliminating the need to create those threads. This also eliminates
 any need to thread relatively small components into each other during a
 coupling/decoupling sequence. In application of this invention, no
 rotation of either part is required in order to achieve coupling and
 decoupling.
 The extent of coaxial alignment at the coupler can be controlled by
 adjusting the length of the overlap between the male coupler segment and
 the female coupler segment. For example, if a relatively longer male
 coupler segment is used, i.e., an elongate member which is relatively
 longer between its leading end and its groove, then axial alignment of the
 connected ends of the guidewire/extension wire is more rigidly maintained.
 Conversely, if a shorter male member (up to and including a substantially
 spherical ball) and a corresponding sized female coupler segment are used,
 then the axial rigidity of the overlapped coupler segments will be
 relatively minimal. Adjustment of guidewire/extension wire overlap at the
 coupler may produce changes in the "feel" of an extended guidewire to a
 catheter user.
 One skilled in this art will appreciate that there are likely to be a
 number of structural equivalents to the "lip" and "groove" construction
 described here. All of such constructions are within the scope of the
 present invention. For example, instead of a lip on the female coupler
 segment, one or more dimples or protrusions (or a series or locus of
 dimples or protrusions) could be machined, stamped, or molded therein. In
 that embodiment, the male segment would have surfaces, detents, or dents
 which would cooperate with the dimples to provide a tactile sensation at
 coupling and to couple the segments. A slide-stop (such as that mentioned
 in U.S. Pat. No. 5,247,942) could be used if the cooperating surfaces of
 the slide and stop permitted the slide/stop to be decoupled using
 decoupling or withdrawal forces in the range discussed below.
 It will also be appreciated that a "lip" or bead, as that term is used
 herein, may be located within the coupler sleeve rather than at one end.
 In such an arrangement, an intermediate narrow region or lesser diameter
 segment would be stretched, expanded or moved further within the coupler
 sleeve to create the tactile sensation of connection as the male member
 passed therewithin. One or more lateral slots would be utilized and pass
 through the intermediate narrow region to permit the male member to pass
 therethrough more easily. As noted above, a preferred practice of this
 invention is utilization of a single axial slot passing through the bead.
 The single slot embodiment is particularly preferred for smaller diameter
 coronary guidewire applications, e.g., guidewire applications where
 outside diameters in the range of about 0.010 inches to about 0.020
 inches, preferably about 0.014 inches to about 0.018 inches are used.
 As is shown in FIG. 1, a guidewire extension system 10 embodying features
 of the present invention has a guidewire or main section 11 which is
 adapted to be inserted into a patient's vascular system and an extension
 wire or extension section 12 which can be connected and disconnected to
 the main section 11. Connection and disconnection of guidewire 11 and
 extension wire 12 facilitates catheter exchange without the need for
 removing the main guidewire section 11 from the patient's vascular system.
 In the embodiment shown, guidewire section 11 generally comprises an
 elongated shaft 13 having a distal end (not shown in FIG. 1) with a male
 coupler segment 15 located at its proximal end. (The details of a
 preferred guidewire structure are discussed below.) Shaft 13 optionally
 may be covered with a polymeric, e.g., polytetrafluoroethylene (PTFE),
 polyurethane, or other coating (not shown). Single filar coils, multifilar
 coils, radiopacity markers, or other commonly utilized guidewire
 structures, may be disposed on shaft 13. These structures have been
 omitted from this description of the invention for purposes of clarity.
 Extension section 12 has an elongated shaft 24 with a hollow female coupler
 segment 26 secured to its distal end. Female coupler segment 26 may be
 fixed to extension wire 24 using techniques well known in this art such as
 resistance welding, crimping, gluing, soldering, or brazing. Female
 coupler segment 26 may comprise, for example, a suitably modified section
 of hypotube brazed to the distal end of an extension wire. Female coupler
 segment 26 may also be machined from a segment of solid, cylindrical core
 workpiece. Powder metallurgy techniques also may be used to manufacture
 female coupler segment 26.
 Also shown in FIG. 1 are the plurality of longitudinal slots 25 and a
 circular lip 16. Slots 25 intersect and divide circular lip 16 producing
 opposite, semicircular tabs 17, 18 which can be radially separated (in the
 direction of arrows 19) as male and female segments 15 and 26 are mated.
 Slots 25 may be machined into coupler segment 26 using conventional
 grinding and cutting operations or they may be created by any of a number
 of other known processing techniques including electrical discharge
 machining. The portion of the shaft 24 proximal to the female member 26
 may be covered with, e.g., a polymeric, or other type of coating.
 Male connector segment 15 is elongate, having opposite leading or insertion
 and following ends 20, 21 respectively. In this embodiment, insertion end
 20 is tapered (at 22) to ease the connection process. The exterior surface
 of male connector segment 15 further defines a radial groove 23.
 FIG. 2 illustrates the detailed interaction between lip 16 and radial
 groove 23. FIG. 2 is a cross-sectional view of an embodiment of the
 invention 10, shown in FIG. 1, after the segments have been coupled or
 "snapped" together. In this embodiment, female coupler segment 26
 comprises a section of hypotube which has been brazed (at 40) to extension
 section wire 12. Other methods of securement, e.g., soldering, or gluing,
 may be employed. As is shown, the glue, solder, or braze zone itself can
 be employed to provide a smooth transition between the guidewire or
 extension wire to which the female coupler segment is attached and to the
 coupler segment itself.
 A circular lip 16 of this invention is described in greater detail as
 follows. Circular lip 16 has a slightly rounded or tapered leading or
 opening edge 42, a substantially uniform or single diameter intermediate
 portion 44 and an angled or rounded interior edge or shoulder 46 which
 merges (at 50) to the interior diameter 48 of the hypotube section 26.
 Angled interior edge 46 can be, for example, the byproduct of drilling to
 create interior diameter 48. Interior edge 46, in cooperation with the
 configuration of radial groove 23, determines at least the magnitude of
 the force needed to disengage male and female coupler segments 15 and 26.
 Other factors such as the material employed, its treatment prior to
 incorporation into the present coupler, and the precise interaction
 between the slots and tabs also affect the magnitude of withdrawal forces.
 The details of male coupler segment 15 also are shown in FIG. 2. Male
 coupler segment 15 (best seen in FIG. 1) is defined by the configuration
 of exterior surface 60 of the male segment of the connector system. As was
 discussed above, male segment 15 has an insertion end 20 and a following
 end 21. Insertion end 20, in this embodiment, is rounded or tapered (at
 22) to provide ease of insertion. The outside diameter 62 of the male
 segment 15 leads to and defines radial groove 23. Radial groove 23, in
 this embodiment, comprises an angled, radiussed, or perpendicular annular
 shoulder 23A, a neck 23B which has a uniform diameter, and a radial stop
 surface 23C. Radial stop surface 23C can be disposed substantially
 perpendicularly to the axis of the guidewire extension wire system, as is
 illustrated, or it may be filleted or shaped to provide a more rounded
 stop. As shown, interior edge 46 of female coupler segment 26 is angled so
 as to be complimentary with and to cooperate with annular shoulder 23A
 when lip 16 is lying within radial groove 23. Radial stop surface 23C
 normally controls the extent to which the male and female coupler segments
 can be engaged, provided the elongate member is short enough to fit
 completely within female coupler segment 26 and not abut against the
 extension wire main section. For purposes of orientation, longitudinal
 slot 25 is shown in phantom.
 Three significant observations should be made with respect to the
 embodiment of FIG. 2. First, the interior diameter 48 of female coupler
 segment 26 is larger than the outside diameter 62 of male coupler 15. This
 fact means that no restriction or frictional fit is needed for coupling to
 occur between the male and female segments. The absence of a restriction
 fit also permits male and female coupler segments 15, 26 (and therefore
 the guidewire or extension wire to which they are attached) to rotate
 freely with respect to each other. In other words, this embodiment of the
 invention obviates the need for a structure like the swivel of U.S. Pat.
 No. 5,117,838(Palmer et al.) described above.
 The second important observation is that the structure shown in FIG. 2
 provides a definite tactile "snap" when the segments are coupled. A sound
 may also be heard, especially in the larger sized peripheral wires.
 Whether a sound is generated or not, the tactile sensation of coupler
 engagement is a significant indicator to the system user that coupling is
 complete. A small amount of play, as shown in the system illustrated, also
 permits the physician to move the coupler segments with respect to each
 other and thereby establish that proper engagement has occurred.
 Third, this system permits multiple, affirmative engagement and
 disengagements of the male and female segments, i.e., multiple catheter
 exchanges, can be accomplished. This is yet a further advantage over the
 prior art coupler systems which require permanent connection of the
 segments.
 FIG. 3 is a sectional view of a portion of the female coupler segment 26 of
 the present invention. FIG. 3A is an end view of the female coupler
 segment shown in FIG. 3. In particular, female coupler segment 26
 comprises a hollow tubular body 30 having a substantially circular lip 16
 with longitudinal slots 25 therein. Lip 16 has outside and inside edges
 16', 16", respectively, with a radial surface 16'" therebetween. Lip 16
 can be formed by any of several techniques. However, in the embodiment
 shown, lip 16 was formed by coining a segment of hypotube. This technique
 of formation is to be contrasted with that of FIG. 2 where drilling,
 cutting, and grinding steps were employed. It is noted that coining lip 16
 tends to create a more rounded or radiussed intersection (at 33) between
 tubular body 30 and lip 16 than the same intersection (at 50) in FIG. 2.
 The configuration of the interior intersection between the lip 16 and
 tubular body 30 will, to some extent, determine connector withdrawal
 forces.
 Slots 25 and lip or tabs 16 define flaps 17 and 18 which move from a
 substantially parallel, axial, alignment to a slightly oblique alignment
 (with respect to the system axis) in the coupling process. In the
 connection step, radial surface 16'" slides along the exterior surface 60
 of the male segment, separating the semicircular flaps 17, 18 to a
 slightly opened position. Tubular body 30 biases flaps 17, 18 toward each
 other and tends to reduce the radial width of slot 25. When the connection
 is made, flaps 17, 18 return to substantially their original position, a
 "snap" is heard or felt (or both), and the coupling process is completed.
 When the coupling process is complete, interior edge 16" aligns in
 substantially parallel fashion with shoulder 23A on male connector segment
 15.
 FIG. 4 shows in section the details of one possible approach to attaching
 female coupler segment 26 to elongated shaft 24. As was discussed above,
 in a preferred embodiment, elongated shaft 24 is the distal end of an
 extension wire but may also be the proximal end of a guidewire or main
 wire. Hollow tubular body 30 is attached to shaft 24 at resistance weld or
 spot weld 32. As is noted above, other techniques for attachment may be
 used. In FIG. 4 the elongated shaft segment coupled to tubular body 30 is
 shown to be ramped or tapered at 34. Taper 34 leads to an extension wire
 segment 36 which has substantially the same outside diameter as that of
 hollow tubular body 30. Elongated shaft 24 has been ground to a smaller
 diameter than wire segment 36 to enhance flexibility. Taper 34 therefore
 provides a gentle transition between the extension wire body and tubular
 body 30 which is particularly desirable. Taper 34 permits a catheter to
 pass over hollow tubular body 30 (e.g., during a catheter exchange
 process) without becoming caught on the connector system structure.
 FIG. 5 illustrates one possible connection structure between a guidewire
 proximal end 14 and a male coupler segment 15. The particular guidewire
 structure employed is that of a core wire 70 having oppositely wound
 multifilar coils 72, 72' disposed therearound. Core wire 70 has a reduced
 diameter proximal segment 74 which connects to core wire main section 76
 through taper 78. Coils 72, 72' and reduced diameter proximal segment 74
 are attached to male coupler segment 15, e.g., by brazing, at 80 and 82,
 respectively. Male coupler segment 15 is brazed to guidewire proximal end
 82 at bore 84 which is drilled or machined in the following end 21 of male
 coupler segment 15. It is important that there be a smooth transition from
 male coupler segment 15 to the remaining structure of the guidewire so
 that a catheter can slide smoothly thereover during an exchange process.
 FIG. 6 illustrates another embodiment of the invention wherein groove 23'
 comprises a shoulder 23A', a portion of reduced diameter segment 74
 indicated at 23B' and the proximal end of coils 72, 72'indicated at 23C'.
 There are many possible ways to construct a groove which will cooperate
 with a connecting female segment in accordance with this invention.
 FIGS. 7, 8, 9, and 11 illustrate variations in construction of a male
 connecting segment of this invention. The variations illustrated are
 alternative ways in which the desired external configuration of the male
 coupler segment can be created. In each of the systems illustrated, a
 reduced diameter proximal guidewire segment 90, 91, 92, 93, respectively,
 is attached (at 94, 95, 96, and 97, respectively), to elongate male
 connector segment 98, 99, 100, and 101 respectively. In each instance a
 groove 102, 103, 104, and 105 is created or defined. FIG. 7 illustrates a
 coined sleeve that is attached to the wire core 90 by application of glue,
 solder, or braze through opening 97 on the insertion end of the segment
 98. This procedure keeps annular shoulder 150 clean. FIG. 8 illustrates a
 plasma ball weld 95 utilized on the insertion end of male connector
 segment 99.
 FIGS. 8, 8A and 8B illustrate different sized guidewires in which the
 present invention has been used. For example, the guidewire shown in FIG.
 8 would be the structure of a 0.035 in. and 0.038 in. diameter guidewire
 having two counterwound spring coils 72, 72'. The embodiment of FIG. 8A
 has a single spring coil 72 and would be structure employed in a 0.025 in.
 diameter guidewire.
 FIG. 8B is a structure useable for very small diameter, e.g., 0.014 in.,
 guidewires. No spring coils are used. The extreme proximal end of the
 guidewire is ground to a lesser diameter and groove 103" is defined by
 elongate male connector segment 99, a reduced diameter segment 152, and
 taper 154.
 FIG. 9 shows a sleeve which was crimped (at 96) on the guidewire body core
 92.
 FIG. 11 illustrates an embodiment where the requisite external
 configuration of the male segment is externally formed into a segment of
 hypotube 160. Hypotube 160 then is brazed onto the proximal end of the
 guidewire and a rounded tip 120 is created on the remaining end.
 FIG. 10 illustrates an embodiment of the invention wherein the male
 connector segment external configuration 15 is simply machined into the
 proximal section of the guidewire, e.g., by centerless grinding. A radial
 groove or notch 110 defined by surfaces 112, 114, and 116 cooperates with
 the lip portion of the female coupler segment.
 FIG. 12 is a sectional view of an alternative embodiment of a female
 coupler segment 120 of this invention. In FIG. 12 a section of hypotube
 122 has a metal ring 124 brazed, soldered or glued (at 123) to its open
 end. Metal ring 124 has a diameter which is slightly less than the inside
 diameter of the hypotube 122 and thereby creates a lesser diameter lip
 126. As shown, this approach produces a substantially circular lip.
 Hypotube section 122 then is resistance welded, glued, soldered or brazed
 to the guidewire or extension wire core (at 128) with which it is
 associated. Electrical discharge machining or other known fabrication
 techniques then are used to create lateral slot 130. Alternatively, ring
 124 could be fitted inside of hypotube segment 122 to create an inwardly
 disposed "lip" as is discussed above. Regardless of the location of the
 lip, as long as the female and male segments overlap sufficiently, kinking
 at the connection will be reduced.
 In FIGS. 13 and 14 there is shown a further embodiment 200 of the coupler
 system of the present invention. The embodiment shown is particularly
 useful for smaller diameter, e.g., cardiovascular dimensioned,
 guidewires/extension wires. Generally speaking, devices to which this
 embodiment of the invention may be applied will have outside diameters in
 the range of about 0.010 inches to about 0.020 inches.
 In FIG. 13 system 200 comprises a male coupler segment 202 and a hollow
 female coupler segment 204. Arrow 201 shows the direction of insertion of
 the coupler segments. Male coupler segment 202 has a first diameter
 proximal segment 206, leading to a first tapered segment 208 and in turn
 to a second, smaller diameter segment 210. Distally attached to second
 diameter segment 210 is a bullet-shaped head 212. Head 212 has a leading
 or insertion end 214 and a following end 216. Insertion end 214 is of a
 hemispherical, rounded configuration to reduce insertion force. Following
 end 216 comprises an annular shoulder 218. In conjunction with second
 diameter segment 210 and taper 208, the exterior surface of male coupler
 202 defines an elongate groove or attachment zone which fits into female
 coupler segment 204.
 Female coupler segment 204 comprises, in this embodiment, a section of
 hypotube. In hypotube segment 204 there has been created or fabricated a
 reduced diameter segment 220. The interior diameter of hypotube segment
 204 (not shown in FIG. 13) is proportionately reduced. For example,
 segment 220 may be a radial bead or dent rolled into the hypotube segment
 204 so as to create a reduced interior diameter region. Intersecting bead
 220 is a single lateral slot 222. Slot 222 has been cut entirely through
 hypotube segment 204 from the outside to the inside so as to provide room
 for bead 220 to expand radially when male segment 202 is inserted into
 female segment 204. Slot 222 has generally parallel sides 223, 225 and
 symmetric, radiussed ends 227, 229. Especially for smaller diameter
 coupler systems, a single lateral slot intersecting bead 220 is preferred.
 Female coupler segment 204 is, in turn, attached to one or the other of
 the guidewire or the extension wire 221 at braze 224. As is shown, the
 outside diameter of coupler segment 204 is substantially the same as that
 of the guidewire or extension wire 221 to which it was attached. Thus,
 ease of catheter use is provided in that a catheter slides over the
 coupler system without becoming caught at the coupler
 segment-guidewire/extension wire intersection.
 FIG. 14 shows the interior details of the system of FIG. 13 in partial
 section. With male coupler segment 202 inserted into female segment 204,
 annular shoulder 218, second diameter segment 210 and taper 208 cooperate
 with reduced diameter segment or bead 220 to create a coupled system.
 Female coupler segment wall (shown in section and indicated generally at
 205) defines those structures. As is shown, an abruptly tapered section
 226 and a reduced diameter section 228 (reduced from the diameter of the
 main section of the guidewire/extension wire 231) are formed on the
 guidewire/extension wire end 231 to which female coupler segment 204 is
 attached at braze 224. Further, taper 208 is shown to cooperate with
 hypotube open end 230 to restrict or control the extent to which the male
 segment may be inserted into the female segment. Last, a tactile "snap"
 (and accompanying sound) will be heard as annular shoulder 218 passes
 through the reduced interior diameter segment 219 defined by bead 220, and
 the bead 220 abruptly returns or snaps to its original uncompressed
 diameter.
 Insertion and withdrawal forces are always of concern with connector
 systems of vascular (especially cardiovascular) dimension and are
 controllable in the practice of this aspect of the invention.
 Hemispherical bullet-shaped head 212 reduces the forces necessary to
 couple the male and female segments. The relationship between annular
 shoulder 218 and the cross-sectional configuration of bead 220 will
 determine the magnitude of force required to decouple the segments.
 Generally speaking, the configuration shown in FIG. 14, i.e., a bead
 having a lesser diameter following edge (at 230) and a larger diameter
 leading edge (at 232) will substantially increase withdrawal forces. The
 angular relationship between annular shoulder 218 and the following edge
 230 (among other factors) also will determine the magnitude of withdrawal
 forces.
 In light of the above disclosure, one skilled in this art will understand
 that several techniques may be used to create the inventive structure
 disclosed. Specifically, bead 220 can be rolled (i.e., roll-formed) into
 hypotube segment 204. Slot 222 may then be machined or otherwise cut,
 e.g., via laser, into, through bead 220, to complete this feature of the
 invention. The male segment can be created by, e.g., centerless grinding,
 of the end portion of the guidewire/extension wire on which it is located.
 The main guidewire section 11 is intended for use in positioning a catheter
 (not shown) in the vasculature of a patient, and it has a length
 corresponding to the length of a conventional guidewire for this purpose.
 Details of typical catheters and guidewires can be found in U.S. Pat. No.
 4,538,622 (Samson et al.) and U.S. Pat. No. 4,569,347 (Frisbie). Those
 patents are incorporated by reference herein in their entirety.
 Extension wire 12 is sufficiently long so that when the main guidewire
 section 11 and extension wire 12 are connected together, the guidewire
 system or exchange wire 10 has an overall length suitable for catheter
 exchange without removing the main guidewire 11 from the patient's
 vascular system. With a catheter having a length on the order of about 65
 cm to 175 cm, for example, guidewire 11 would have a length of about 100
 to about 200 cm, and extension wire 12 would have a length of about 100 to
 about 200 cm (or longer).
 Shafts 13 and 24 and female segment 26 can be fabricated from essentially
 any suitable material, such as stainless steel, Elgiloy, or the shape
 memory alloy referred to as Nitinol (55% Ni-Bal. Ti). Each should have an
 overall largest diameter which allows, e.g., a dilatation catheter, to
 pass freely thereover. Preferably, the two shafts 13 and 24 are provided
 with a smooth transition between them. Either or both of shafts 13, 24 can
 be provided with a coating of polymers or elastomers such as PEBAX
 polyamide, polyurethane, polytetrafluoroethylene (PTFE), or other such
 material well known to one skilled in this art.
 Typical dimensions of the main guidewire section include an outside
 diameter of the shaft 13 of about 0.009 to about 0.065 inch, an outside
 diameter of the male insertion segment about 0.006 inch to about 0.050
 inch and a length of about 0.025 to about 0.250 inch. The female connector
 segment has dimensions which generally cooperate with the male segment
 dimensions and a length of about 0.060 inches to about 1.0 inches and an
 outside diameter of about 0.009 in. to about 0.065 in. While this
 invention is particularly applicable to larger diameter guidewires, e.g.,
 0.038 inches and 0.035 inches, smaller diameter applications, e.g., 0.025
 inches or less, down to 0.009 inch diameter wires, are also within its
 scope. Generally speaking, the ratio of male segment outside diameter to
 male segment length and female segment inside diameter to female segment
 length will fall in the range of 1:100 to about 1:1.Having a segment
 length which is larger than the respective segment diameter tends to keep
 the wires more axially aligned, thereby minimizing unwanted bending and
 kinking.
 Percutaneous transluminal angioplasty is a medical procedure in which the
 present invention can be used. In use, the main guidewire section 11 is
 percutaneously introduced into the vascular system of a patient with a
 dilatation catheter through the skin by means of an introducer (not
 shown). The distal tip of the guidewire is advanced beyond the distal tip
 of the dilatation catheter while the latter is held in place. The main
 guidewire section 11 is advanced into the selected vessel. The guidewire
 tip is preferably advanced through the lesion and beyond it, in order to
 permit the balloon portion of the dilatation catheter to be positioned
 within the lesion over a more supportive section of the guidewire. Once in
 position, the main guidewire section 11 is held in place and the
 dilatation catheter is advanced along it until the inflatable balloon
 thereof is within the lesion. Male connector segment 15 remains outside
 the patient's body and outside any adapter which may be connected to the
 proximal end of the dilatation catheter. If necessary, e.g., to retain a
 sufficient length of the main guidewire section 11 outside the catheter
 for the physician to grip, the guidewire and catheter may be advanced
 together substantially in unison.
 To exchange catheters, the main guidewire section 11 is extended by
 manually snapping the female tubular member 26 onto the male member 15.
 When the two guidewire sections are engaged, the dilatation catheter can
 then be withdrawn from the patient's body over the extended guidewire
 system.
 A new dilatation catheter may then be introduced over the extension section
 12 and advanced along the main guidewire section 11 within the patient's
 body until the balloon crosses the lesion. Once the proximal end of the
 new catheter has advanced beyond the connection between female member 26
 and male member 15, section 12 can be removed from section 11 by
 unsnapping the female member 26 by pulling the two sections apart. This
 can be accomplished without disturbing the position of the main section 11
 in the patient's body.
 The above description describes utilization of the present invention
 primarily in coronary angioplasty catheter exchange. It is to be
 understood that this invention has application in essentially any
 procedure where a catheter is utilized for diagnostic or interventional
 applications.
 This invention has a number of important features and advantages. The two
 sections of the guidewire can be connected together whenever a longer,
 exchange wire is needed, and they can be disconnected whenever the
 additional length is not required. The two sections of the guidewire may
 be connected and disconnected (and reconnected, if desired) by the
 physician by simply "snapping" and "unsnapping" the male segment into or
 out of the female segment. Subsequent to engagement, the segments can be
 freely rotated with respect to each other (e.g., to permit the guidewire
 to be steered) and can easily be disengaged. This can be done as needed,
 and no special tools are required whether to make the connection or to
 separate it. Thus, catheter exchange is greatly simplified. This also
 permits the same guidewire to be repositioned to second and multiple
 additional vascular sites which then may be treated with different
 catheters, making the present system very versatile.
 As noted in the previous paragraph, a guidewire extension system of this
 invention can be multiply engaged and disengaged. The present invention
 therefore permits two or more catheter exchanges, during a medical
 procedure, without a need to reposition or exchange the main or guidewire.
 Generally speaking, the ease of disengagement (i.e., the pounds of force
 needed to disengage an extension wire from a guide wire) has been found to
 be in the range of about 0.2 to about 5.0 lbs., preferably about 0.3to
 about 3.0 lbs., and most preferably about 0.7 lbs. to about 2.0 lbs.
 Factors which affect withdrawal forces include the overall device diameter
 (withdrawal forces being higher for larger diameter devices), wall
 thickness of the tube, slot configurations, the materials of which the
 male and female coupler segments are made, and the relationship between
 the cooperating surfaces on the male and female coupler segments. The more
 abrupt or acute the relationship, the higher the withdrawal forces. With
 reference to FIG. 2, the more nearly perpendicularly (relative to the axis
 of the device) shoulder 23A engages surface 46, the more difficult
 withdrawal of male coupler segment from the female coupler segment.
 It is apparent from the foregoing that a new and improved extended
 guidewire system has been provided. While the present invention has been
 described herein with the male connecting element fixed to the distal end
 of the main guidewire, and the female member located on the distal end of
 the extension section, it is obvious that the female connector member and
 male connector member may be interchanged. Moreover, it will be apparent
 to those familiar with the art that other modifications and improvements
 can be made without departing from the scope of the invention as defined
 by the following claims.