Extendable guidewire assembly

An extendable guidewire assembly comprising: a guidewire whose proximal end carries a first axial interlocking member; and extension wire whose distal end carries (i) a second axial interlocking member that is adapted to overlap and axially interlock with the first member and (ii) a retractable sleeve that is retracted to permit the interlocking members to be interlocked and extended to enclose the interlocked members to maintain their interlocked relationship.

TECHNICAL FIELD 
This invention is in the general field of surgical instruments and relates 
specifically to guidewires that are used in cardiovascular and 
endovascular procedures to facilitate the placement of catheters within 
the vasculature of patients. 
BACKGROUND 
The general procedure for placing catheters within vessels is to track a 
guidewire through the vessel to the desired position and advance the 
catheter over the guidewire. Guidewires are required because the catheters 
themselves do not have sufficient column strength or torqueability to be 
able to be tracked or steered through the vessel. See, for instance, U.S. 
Pat. No. 4,884,579. 
In some procedures such as angioplasty using dilatation balloon catheters, 
it is necessary to exchange catheters to increase balloon size. It may 
also be necessary in some instances to replace catheters due to material 
fatigue. Two guidewire techniques have been employed in such instances. In 
one, the initial guidewire is removed and replaced with an exchange wire 
that is somewhat greater than double the length of the catheter. In order 
to avoid the need for a separate exchange wire a second technique that 
involves attaching an extension wire to the initial guidewire was 
developed. 
U.S. Pats. Nos. 4,917,103 and 4,922,923 describe an extendable guidewire 
assembly that employs a sleeve that is connected to the proximal end of 
the guidewire and into which the distal end of the extension wire is 
inserted. The sleeve and extension are then crimped to form a permanent 
joint or union between the two wires. 
U.S. Pat. No. 4,875,489 describes another type of extendable guidewire 
assembly in which one of the wires has a tapered tip and the other has an 
expandable sleeve into which the tip is received. A second concentric 
sleeve encloses the expandable sleeve to ensure a friction fit between the 
tapered tip and expandable sleeve. 
U.S. Pat. No. 4,966,163 describes yet another kind of extendable guidewire 
assembly. In this assembly one of the wires carries an internally threaded 
sleeve and the other wire carries a threaded head. The two wires are 
coupled together by threading the head into the sleeve. 
Applicant is also aware of an extendable guidewire assembly design in which 
one of the wires carries an open-ended sleeve and the other wire has a 
tapered tip encircled by a helical coil. The wires are coupled by 
inserting the tip into the sleeve and twisting it. The twisting causes the 
coil to expand and form a friction fit with the interior of the sleeve. 
The wires are uncoupled by twisting the tapered tip wire in the reverse 
direction. 
A primary object of the present invention is to provide an extendable 
guidewire assembly that may be connected and disconnected and is 
relatively simple to manufacture. 
DISCLOSURE OF THE INVENTION 
The invention is an extendable guidewire assembly for use within a 
patient's vasculature comprising in combination: 
(a) a guidewire having a distal end that is adapted to be fed into said 
vasculature and a proximal end that has a first longitudinal (axial) 
interlocking member; 
(b) an extension wire having a proximal end and a distal end that has a 
second longitudinal interlocking member that is adapted to longitudinally 
overlap and interlock with the first interlocking member; and 
(c) a retractable sleeve carried concentrically about one of either the 
proximal end of the guidewire or the distal end of the extension wire, the 
sleeve being longitudinally movable from a retracted position in which it 
does not enclose an interlocking member to an extended position in which 
it encloses the overlapped, interlocked members to prevent said members 
from substantial radial movement relative to each other.

MODES FOR CARRYING OUT THE INVENTION 
FIGS. 1 and 2 illustrate the preferred embodiment of the extendable 
guidewire assembly of the invention. The three principal components of the 
assembly are: a guidewire 11, an extension wire 12, and a sleeve 13. In 
these figures only the proximal end 14 of the guidewire and the distal end 
15 of the extension wire are shown. The remainders of the components are 
not shown and are of conventional structure. 
While this invention may be produced with guidewires of any length and 
diameter, it will typically be employed with stainless steel or 
nickel-titanium alloy guidewires and extensions that are .ltoreq.0.46 mm 
in diameter, more normally 0.30 to 0.41 mm in diameter. In most instances 
the length of the guidewire will be in the range of 100-200 cm and the 
extension will be on the order of 125 to 225 cm in length. 
The proximal end 14 of guidewire 11 has a tapered section 16 and an 
elongated small diameter tip 17. Tip 17 is deformable and, in the case of 
a 0.36 mm diameter wire, will typically have a diameter in the range of 
0.08 to 0.15 mm and a length of 0.2 to 0.7 cm. A tightly wound coil 18 is 
affixed to the end of the tip such as by soldering. The outer diameter of 
the coil is greater than 1/2 the inner diameter of the sleeve and will 
normally be 0.10 to 0.20 mm. The length of the coil will normally be 0.2 
to 0.7 cm. 
The distal end 15 of extension wire 12 similarly tapers at 19 to an 
elongated tip 22. A tightly wound coil 23 is similarly affixed to the end 
of tip 22. The dimensions of tip 22 and coil 23 are in the same ranges as 
the dimensions of tip 17 and coil 18. Proximal to taper 19 is a reduced 
diameter segment 24 of extension wire 15. In the case of a 0.36 mm 
diameter extension wire, the diameter of segment 24 will normally be 0.20 
to 0.25 mm. Segment 24 extends between 19 and a second taper 25 and will 
normally be about 2.0 cm to 10.0 cm in length. Sleeve 13 is carried 
concentrically about segment 24 as is a coil spring 26. The proximal end 
of coil spring 26 is connected to the inner end of taper 25. Its distal 
end is affixed to the proximal end of sleeve 13. The spring serves to bias 
the sleeve distally. The outer diameters of coil 26 and sleeve 13 are 
preferably less than or equal to that of the diameter of the main body of 
the extension wire (proximal to 25). Also, the diameter of the proximal 
end 14 of guidewire 11 is such that it may be received within the lumen of 
sleeve 13. 
Sleeve 13 is retractable, that is, it is slidable on segment 24 from a 
retracted position (FIG. 1) in which spring 26 is compressed and the 
entire portion of tip 22 that is wrapped in coil is exposed, to an 
extended position (FIG. 2) in which the tip 22 is entirely enclosed. For 
use with guidewires and extensions of the above-described dimensions, the 
sleeve will normally have an outer diameter of about 0.36-0.46 mm, an 
inner diameter of 0.2 to 0.30 mm and a length of 1 to 8 cm. 
In the embodiment depicted in FIGS. 1 and 2 the guidewire and extension 
wire connect as follows. The sleeve 13 is retracted to the position shown 
in FIG. 1 by exerting axial force on the sleeve in the proximal direction. 
The coil-wrapped tip 17 of the guidewire is then inserted into the open 
(distal) end of the sleeve so that it rests between the unwrapped portion 
of tip 22 and the inner wall of the sleeve. The axial force on the sleeve 
is then removed and the sleeve is slid distally by the force exerted by 
spring 26 so that it encloses both tips 17 and 22 and portions of segment 
24 of the extension and end 14 of the guidewire. The sleeve is dimensioned 
such that its inside diameter is less than the combined outside diameters 
of the coil-wrapped portions of tips 17, 22. Accordingly, as shown in FIG. 
2, the tips 22 axially or longitudinally overlap each other with the ends 
of the coil wrappings abutting in a longitudinally interlocking 
relationship. In this regard, the sleeve prevents substantial radial 
movement of the interlocked tips thus ensuring that the tips remain 
axially interlocked. The guidewire and extension may be disconnected by 
retracting the sleeve to a position such that tip 17 may be moved radially 
and withdrawn from its overlapping position with tip 22. 
FIGS. 3 and 4 depict another embodiment of the invention assembly. In this 
embodiment, the main bodies of the guidewire and extension wire and the 
retractable sleeve are structured as in the embodiment of FIGS. 1 and 2. 
Only the structures of the interlocking tips of the guidewire and 
extension wire differ from those of the embodiment of FIG. 1. The tip of 
the guidewire 11 has a pair of tapers at 27 and 28 that define a reduced 
diameter segment 29. The diameter of segment 29 is less than the inner 
diameter of the sleeve. Proximally of taper 28 is a second segment 32 of 
still smaller diameter that terminates in a ball 33. Correspondingly, the 
distal end of extension wire 12 has a pair of radially expandable 
resilient jaw members 34, 35 that define a generally spherical socket 36. 
When the sleeve 13 is retracted (FIG. 3), the jaws are open. When the 
sleeve is in its extended position (FIG. 4), it exerts radial force on the 
jaws to close them. Thus, the following procedure is employed to connect 
the guidewire and extension wire of this embodiment. The sleeve is 
retracted to a position proximal of jaws 34 and 35 allowing the jaws to 
open. The ball 33 on the proximal end of the guidewire is then inserted 
into socket 36. The sleeve is then released to permit it to slip over the 
jaws and close them about ball 33. 
FIGS. 5 and 6 show yet another embodiment of the invention. Again only the 
structures of the tips of the guidewire and extension wire differ in 
structure from the previously described embodiments. In this embodiment 
the proximal end of the guidewire has a taper at 37 and a reduced diameter 
tip 38. The end of the tip is formed into a locking tang 39. 
Correspondingly, the distal end of the extension wire is formed into a 
second locking tang 42 that is configured to interlock with tang 39. The 
guidewire and extension are connected by retracting (FIG. 5) sleeve 13 to 
expose tang 42, positioning tang 39 to interlock with tang 42, and 
releasing the sleeve so that it encloses the interlocked tangs (FIG. 6). 
FIGS. 7 and 8 illustrate a fourth embodiment of the invention. Again only 
the structures of the tips of the guidewire and extension wire differ in 
structure from the previously described embodiments. In this embodiment 
the proximal end of the guidewire has a taper at 43, a reduced diameter 
segment 44, and a generally cylindrical head 45 with a tapered end 46. The 
distal end of the extension wire has a cylindrical bore 47 of slightly 
smaller diameter than the diameter of head 45. The length of the bore is 
at least the combined length of the head 45 and reduced diameter segment 
44. A first axial slot 48 in the extension wire extends radially from the 
surface of the wire through to the bore 47 and axially from the end of the 
wire. This slot opens into a second slot 49 whose radial dimension is 
equal to or greater than the diameter of head 45. The guidewire and 
extension wire of this embodiment are connected as follows. The sleeve is 
retracted (as seen in FIG. 7). The tapered end of the head 45 is then 
inserted into the opening of bore 47 and axial force is applied. The slot 
48 permits the bore 47 to expand slightly to permit the head 45 to be 
foreced into the bore until the head is seated in registry with the slot 
49 (as seen in FIG. 2). Once the head reaches that position the radial 
expansion exerted on the distal segment of bore 47 by the head is relieved 
and the distal segment snaps shut behind the head, thus axially locking 
the head in place. The sleeve is then moved to its extended position (FIG. 
2) to enclose the ends of the wires. The wires may be disconnected by 
retracting the sleeve and lifting the guidewire tip out of the bore via 
the slots 48, 49. 
While the above-described embodiments all show the sleeve being carried on 
the extension, it will be appreciated that the respective tip structures 
may be reversed (i.e., the sleeve, etc., carried on the guidewire). 
Similarly, other modifications of these embodiments that are obvious to 
those of skill in the mechanical and guidewire/catheter arts are intended 
to be within the scope of the following claims.