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Description  |
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BACKGROUND OF THE INVENTION
The present invention relates to a wire guide for use in performing a
catheterization and, more particularly to a coil spring wire guide having
a movable mandril.
As described herein, the purpose of a wire guide is to aid the insertion
and placement of a flexible catheter within a body blood vessel. The wire
guide may be used in a procedure known as catheterization by the
percutaneous entry or Seldinger technique. Employing this technique, a
needle assembly including a stylet and a sharp pointed inner needle is
introduced into a desired blood vessel, such as for example, the femoral
artery or vein. The inner needle is then withdrawn and a coil spring wire
guide is inserted through the lumen of the stylet into the blood vessel.
External pressure is then applied to hold the wire guide in place while
the stylet is withdrawn thereover. At this point the wire guide may either
be manipulated to place the distal end in the desired body location and
the catheter threaded over the wire guide to the selected area, or the
catheter is threaded over the wire guide and pushed within 3 or 4
centimeters of the distal end of the wire guide, whereupon, using the wire
guide as a leader, the wire guide and catheter are together advanced to
the desired body location.
Anyone familiar with the body vascular system can easily appreciate that
considerable manipulation is required to direct the wire guide or wire
guide and catheter combination to the desired body location, due to the
typically tortuous path involved. As a result, wire guides used for this
purpose must be sufficiently flexible at the distal tip to permit
negotiation of the desired path, yet also sufficiently rigid to resist
undesirable bending or doubling back during insertion and withdrawal.
Heretofore, these requirements have attempted to be met by constructing
the wire guide of a closely wound coil spring having an inner opening
which is solder-sealed at the proximal and distal ends. The inner opening
includes a relatively stiff wire mandril which provides rigidity to the
wire guide. Typically, the distal portion of the mandril terminates
several centimeters short of the distal end of the wire guide. Wire guides
of this type, however, exhibited problems because they were too flexible
along the portion of the guide forward of the mandril and too rigid or
stiff along the distal portion of the mandril.
The pertinent art dislcoses at least two types of wire guides which propose
to solve the above noted problems. Wire guides of the first type provide a
mandril having a taper along the distal portion so that there is a more
gradual transition between the highly flexible distal tip of the wire
guide and the relatively rigid non-tapered portion of the mandril. While
an improvement, this type of wire guide still fails to provide the desired
degree of flexibility and stiffness.
Another construction which is disclosed in catheter wire guides of the
second type provides a mandril which is movable longitudinally within the
opening of the wire guide. The movable mandril permits the stiffness of
the distal portion of the wire guide to be varied by lengthening or
shortening of the flexible portion of the wire guide. In actual use,
however, movable mandrils have been found not to display the requisite
ease of movement which is necessary for accurate control of the distal tip
in the body.
The following patents are believed generally relevant to the apparatus of
the present invention in that they disclose various designs for catheter
wire guides:
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U.S. Pat. No. Inventor
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3,452,740 Muller
3,612,058 Ackerman
3,437,103 Cook
3,789,841 Antoshkiw
4,080,706 Heilman
4,005,369 Heilman
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U.S. Pat. No. 3,452,740 to Muller discloses a spring guide manipulator and
wire guide therefor, the wire guide being an example of a helically wound
wire guide with a flexible distal tip. The wire guide does not include a
moveable mandril.
U.S. Pat. No. 3,612,058 to Ackerman discloses a further example of catheter
stylet or wire guide having a helically wound wire and a tubular
stiffening portion or mandril disposed axially along all but the distal
most tip portion of the helically wound wire. The tubular stiffening
portion is not axially movable in the wire guide.
U.S. Pat. No. 3,547,103 to Cook discloses an example of a coil spring wire
guide for a catheter falling within the first type. The wire guide
includes a tapered mandril which is soldered to the proximal end of the
wire guide and terminates short of the distal end of the wire guide. The
mandril is not longitudinally movable in the wire guide.
U.S. Pat. No. 3,789,841 to Antoshkiw discloses a disposable wire guide of
the first type which includes a Teflon jacket coating the non-tapered
portion of the core wire. The core wire is, however, not longitudinally
movable within the wire guide.
U.S. Pat. No. 4,003,369 and U.S. Pat. No. 4,080,706 to Heilman et al.
disclose a further example of a coil spring wire guide of the first type
in which the coil spring wire is coated with Teflon prior to winding.
These patents also do not disclose a movable mandril or core wire.
There exists a distinct need for a catheter wire guide having the requisite
degree of flexibility and stiffness, yet which also avoids the
disadvantages associated with previous designs for catheter wire guides.
SUMMARY OF THE INVENTION
A wire guide for guiding a catheter within a body blood vessel according to
one embodiment of the present invention is characterized by a helically
wound wire having an opening therethrough. There is further provided a
mandril positioned within the opening and longitudinally movable therein
relative to the helically wound wire for varying the flexibility of the
distal tip of the wire guide. The wire guide is further characterized by a
coating of lubricating material which coats the outer surface of the
mandril and which facilitates smooth movement of the mandril within the
opening of the wire guide.
Accordingly, it is an object of the present invention to provide an
improved wire guide for guiding a catheter within a body blood vessel.
Further objects and advantages of the present invention will be made
apparent by reference to the following figures and detailed description.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a fragmentary sectional view of the wire guide of the present
invention.
FIG. 1A is an enlarged fragmentary view, in full section, of the Teflon
coated mandril of the present invention.
FIG. 2 is a fragmentary sectional view, similar to FIG. 1, of the wire
guide of the present invention, but having the mandril withdrawn from the
guide portion relative to the position shown in FIG. 1.
FIG. 3A is an enlarged fragmentary sectional view depicting the mandril
without a bulb on the distal tip protruding through coils in the wire
guide when an attempt is made to advance the mandril through a curved
section of the wire guide.
FIG. 3B is an enlarged fragmentary sectional view similar to FIG. 3A, but
with the mandril having a bulb on the distal tip and depicting how the
mandril with the bulb is able to follow the curvature of the wire guide
during advancement.
DESCRIPTION OF THE PREFERRED EMBODIMENT
For the purposes of promoting an understanding of the principles of the
invention, reference will now be made to the embodiment illustrated in the
drawings and specific language will be used to describe the same. It will
nevertheless be understood that no limitation of the scope of the
invention is thereby intended, such alterations and further modifications
in the illustrated device, and such further applications of the principles
of the invention as illustrated therein being contemplated as would
normally occur to one skilled in the art to which the invention relates.
Referring now to the drawings, there is illustrated the preferred
embodiment of the wire guide of the present invention designated generally
at 10. Wire guide 10 is seen to include a guide portion 11 and a handle
portion 12 which are connected by a core wire or mandril 13 which is
longitudinally movable within guide portion 11. Both guide portion 11 and
handle portion 12 are formed of lengths of stainless steel helically wound
wire 14 and 19, respectively. While not shown, it is to be understood that
guide portion 11 may also be coated along its entire outer surface with a
lubricating material such as Teflon in order to facilitate smooth movement
of guide portion 11 within a body blood vessel and thereby minimize the
hazards of blood clot generation and trauma to body tissues. The Teflon
coating is preferably applied to guide portion 11 after wire 14 is
helically wound so that the outer surface may be made more smooth than
would be the case if the Teflon coating was applied prior to wire 14 being
wound. This method of application also permits the Teflon coating to be
applied only to the outer surface of guide portion 11 where it is needed,
thereby resulting in a materials savings. The diameter of guide portion 11
will, of course, vary depending upon the size of the catheter to be placed
in the body, which is itself dependent upon the size of the blood vessel
or vessels to be catheterized, but will normally be within the range of
from approximately 0.025 to 0.052 inches. A relatively small diameter
(0.002 to 0.005") safety wire 15 having a circular cross-section extends
between the proximal and distal tips 16 and 17, respectively, of guide
portion 11 and is connected thereto by suitable means, such as a solder or
weld. Alternatively, safety wire 15 may have a rectangular cross-section
0.002 to 0.004 inches thick and 0.006 to 0.012 inches wide. It may be
appreciated that distal tip 17 is rounded to facilitate advancement of
guide portion 11 within a body blood vessel, and the solder or weld at
proximal tip 16 contains a passageway therethrough which is sized to allow
longitudinal movement of mandril 13 within guide portion 11. Mandril 13 is
disposed within the longitudinal opening 18 defined by the inner surface
of guide portion 11 and is longitudinally moveable therein by external
manipulation of handle portion 12 in a manner which will be fully
described later herein.
The proximal most portion of mandril 13 is received and securely anchored
at ends 20 and 21 of handle portion 12 by a solder or weld. Wire 19 is
made from stainless steel and may have a diameter which corresponds to the
diameter of wire 14. Mandril 13 is formed from a length of stainless steel
wire 13A having a diameter in a range from 0.012 to 0.021 inches and has a
tapered distal portion 23 which narrows towards an enlargement or bulb 23A
at the distal tip of mandril 13. Tapering of distal portion 23 serves to
permit a gradual transition in flexibility from the highly flexible
portion of guide portion 11 ahead of tip 23 to the relatively much stiffer
portion of guide portion 11 coextensive with the non-tapered portion of
mandril 13.
Bulb 23A allows mandril 13 to follow around curves in coil spring 14 when
it is advanced. As seen in FIG. 3A, without bulb 23A the tapered end of
mandril 13 would lodge in the space between the coils of wire 14 and
actually protrude outside the coils if it is advanced further. This would
cause considerable trauma to a blood vessel. As clearly seen in FIG. 3B,
bulb 23A has a relatively short length so that it does not appreciably
affect the stiffness of the coil and has a diameter which is sufficiently
large to prevent mandril 13 from exiting between the coils and protruding
into a blood vessel. Preferably, the diameter of bulb 23A is approximately
equal to the diameter of the untapered portion of mandril 13 and a length
which is 2-5 times this diameter.
Mandril 13 is coated with a layer 24 of lubricating material, such as
Teflon, which serves to facilitate the smooth movement of mandril 13
within longitudinal opening 18. It is to be appreciated that mandril 13
provides the necessary stiffness and rigidity to guide portion 11 to
permit it to be advanced through a typically tortuous path in the vascular
system. It must also be appreciated that the distal most portion of guide
portion 11 must be sufficiently flexible to permit guide portion 11 to
negotiate relatively sharp bends or turns, such as is for example
encountered when guide portion 11 is advanced through a side passage of a
blood vessel which is branched from the main passage. In order to provide
flexibility to the distal most portion of guide portion 11, mandril 13 is
positioned so as to terminate several centimeters behind distal tip 17 of
guide portion 11. This condition is depicted in FIG. 2. The relative
amount of flexibility at distal tip 17 may be varied therefrom as required
during advancement of the wire guide into a desired body location by
positioning the distal end of mandril 13 closer to or further apart from
distal tip 17. FIG. 1 shows the distal end of mandril 13 positioned
relatively closer to distal tip 17, such as would be accomplished when it
is necessary to increase the stiffness of the distal portion of the wire
guide.
Relative movement of mandril 13 within guide portion 11 is accomplished by
external manipulation of mandril 13 in the following manner. The proximal
portion of guide portion 11 is grasped with the thumb and forefinger of
one hand and held in position and handle portion 12 is grasped with the
thumb and forefinger of the other hand and moved towards or away from
guide portion 11 by a pushing or pulling movement on handle portion 12.
The use of a Teflon coating on mandril 13 permits smooth movement of
mandril 13 within opening 18 despite the tortuous path negotiated by guide
portion 11 and the presence of safety wire 15 which may otherwise
substantially inhibit longitudinal movement. Further, the use of a tapered
tip on mandril 13 ensures a gradual transition in the degree of
flexibility.
While the invention has been illustrated and described in detail in the
drawings and foregoing description, the same is to be considered as
illustrative and not restrictive in character, it being understood that
only the preferred embodiment has been shown and described and that all
changes and modifications that come within the spirit of the invention are
desired to be protected.
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