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Description  |
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This invention generally relates to vascular catheters and particularly to
guiding members for the placement of catheters within a patient's vascular
system in procedures such as percutaneous transluminal coronary
angioplasty (PTCA).
In typical PTCA procedures a guiding catheter having a preformed distal tip
is percutaneously introduced into the cardiovascular system of a patient
and advanced therein until the distal tip thereof is in the coronary
artery. A guidewire is introduced through the guiding catheter and
advanced into the patient's coronary vasculature until the distal end of
the guidewire crosses the lesion to be dilated. A dilatation catheter
having an inflatable balloon on the distal portion thereof is advanced
over the previously introduced guidewire, with the guidewire slidably
disposed within an inner lumen of the dilatation catheter, until the
dilatation balloon is properly positioned across the lesion. Once in
position across the lesion, the balloon is inflated to a predetermined
size with radiopaque liquid at relatively high pressures to compress the
atherosclerotic plaque of the lesion against the inside of the artery
wall. The balloon is then deflated so that the dilatation catheter can be
removed and blood flow resumed through the dilated artery.
Steerable dilatation catheters with built-in guiding members are being used
with greater frequency because the deflated profiles of such catheters are
generally much smaller than conventional dilatation catheters and a
smaller profile allows the catheter to cross tighter lesions and to be
advanced much deeper into the patient's coronary anatomy. Additionally,
the use of steerable low-profile dilatation catheters shortens the time
for the angioplasty procedures because there is no need to first insert a
guidewire and then insert a conventional dilatation catheter over the
previously inserted guidewire.
Further details of dilatation catheters, guidewires, and the like for
angioplasty procedures can be found in U.S. Pat. No. 4,323,071
(Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No.
4,468,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson), U.S. Pat.
No. 4,538,622 (Samson et al.); U.S. Pat. No. 4,582,185 (Samson); U.S. Pat.
No. 4,616,652 (Simpson); and U.S. Pat. No. 4,638,805 (Powell) which are
hereby incorporated herein in their entirety by reference thereto.
Guidewires and steerable catheters generally have shapable tips so that
once a shaped or bent tip is pushed beyond the guiding catheter the tip
assumes the preformed shape which aids in the steering of the guidewire or
the steerable catheter through the coronary vasculature of the patient.
However, there has been little success in accurately controlling the shape
of the distal tip of a guidewire or steerable catheter once the guidewire
or steerable catheter is disposed within the patient's arterial system.
What has been needed and heretofore unavailable is a means to easily and
accurately control tip deflection of torqueable guidewires or steerable
catheters from the proximal end thereof when the guidewire or steerable
catheter is in the patient's arterial system. The present invention
satisfies that need.
SUMMARY OF THE INVENTION
The present invention is directed to a torqueable guidewire or guiding
member for vascular catheters having an easily deflectable tip which can
be operated from the proximal end of the guidewire when the guidewire is
being advanced through a patient's arterial system. The guide means is
particularly suitable for dilatation catheters used in PTCA procedures.
The guidewire in accordance with the present invention generally has an
elongated core element which preferably has a tapered distal portion to
provide selective flexibility at the distal end. A helical coil is
disposed about at least the most distal portion of the core element and is
provided with an expanded coil section at a location proximally of the
distal end thereof. The helical coil is secured to the core element at an
intermediate location distal to the expanded coil section and proximal to
the distal end of the coil The proximal end of the coil is preferably
joined to the distal end of an outer tubular guide element, such as a
hypotube, which extends about the core element to the proximal end of the
guidewire or guiding member. An elongated reference element is also
disposed within the coil and secured adjacent to an inner side thereof at
locations proximally and distally of the expanded coil section. Means are
provided at the proximal end of the guiding member to effect relative
axial movement of the core element with respect to the outer tubular guide
element, such as the hypotube or the coil, to change the spacing between
the turns of the expanded coil section, i.e., compressing or expanding the
expanded coil section and thereby causing the deflection of the tip of the
guiding member.
The guiding member of the present invention can be employed as an
independent guidewire or it can be incorporated or fixed within a
steerable dilatation catheter. It provides for effective tip deflection
yet it maintains the torqueing capabilities of the guiding member without
interference between the individual components thereof. These and other
advantages of the invention will become more apparent from the following
detailed description thereof along with the accompanying exemplary
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partial cross-sectional view of a guidewire embodying features
of the invention;
FIG. 2 is a longitudinal cross-sectional view of the proximal end of the
guidewire shown in FIG. 1 with the manipulator or handle in a position to
cause the deflection of the distal tip of the guidewire;
FIG. 3 is a cross-sectional view taken along the lines 3--3 shown in FIG.
2;
FIG. 4 is a perspective view of the manipulator or handle shown in FIGS. 1
and 2;
FIG. 5 is a partial cross-sectional view of a low-profile steerable
dilatation catheter having a fixed guide member embodying features of the
invention;
FIG. 6 is a longitudinal cross-sectional view of the distal tip of the
low-profile steerable dilatation catheter shown in FIG. 5;
FIGS. 7, 8, and 9 are enlarged transverse cross-sectional views taken along
the lines 7--7, 8--8, and 9--9 shown in FIG. 5;
FIG. 10 is an enlarged view of the catheter shown in the circle in FIG. 5;
FIG. 11 is a longitudinal cross-sectional view of the manipulator or handle
at the proximal end of the catheter shown in FIG. 5; and
FIG. 12 is a is a longitudinal cross-sectional view of the distal tip of an
alternate embodiment of a low-profile steerable dilatation catheter
embodying features of the invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a guidewire 10 embodying features of the invention which
generally comprises a core element 11, an outer tubular element 12
disposed about the core element and extending along a substantial part of
the length thereof, a helical coil 13 disposed about the distal tapered
portion 14 of the core element and a handle or manipulator element 15
secured to the proximal end of the core element for the manipulation
thereof. The coil 13, disposed about the tapered distal portion 14 of the
core element 11, is provided with an expanded section 16 at an
intermediate location spaced proximally from the distal tip 17 of the
guidewire 10. The expanded section 16 should be expanded at least 50%,
preferably at least 70% of the stacked distance thereof.
The proximal end of coil 13 is joined to the distal end of the outer
tubular element 12, preferably hypotubing, which extends proximally to the
handle 15. A reference element 18 is disposed within the coil 13 and is
joined to an inner side thereof at a first location 20 proximal to the
expanded section 16 and at a second location 21 distally thereof, which in
this case is the plug 22. The core element 11 is joined to the coil 13 at
an intermediate location 23 between the distal end of the expanded portion
16 and the distal tip 17. Preferably, the core 11 is joined to the coil 13
immediately adjacent to the distal end of the expanded section 16. The
core 11, the outer tubular element 12, the coil 13, and the reference
element 18 may be joined by brazing, soldering or other suitable means.
As shown in FIG. 1, the tapered portion of core element 11 is preferably
flattened in one or more stages 24 to provide improved flexibility and
stiffness transition in the tip thereof. The reference element 18 is
preferably a ribbon also flattened in one or more stages 25 in the distal
direction to also improve flexibility. At least the portion 26 of the coil
13 distally of the expanded section 16 should be formed of suitable
radiopaque material, such as platinum, tungsten, and alloys thereof, to
facilitate the fluoroscopic observation thereof during angioplasty
procedures. The distal portion 26 may be provided with an expanded set
(e.g., 10% of the stacked length) as shown to provide greater tip
flexibility. Plug 22 at the distal tip 17 of the guidewire 10 is made from
gold, platinum, tungsten or other suitable radiopaque materials for
essentially the same reason, i.e., improved fluoroscopic observation
thereof.
The manipulator or handle 15 at the proximal end of guidewire 10 generally
comprises a proximal portion 27 a distal portion 28 and a collar 30 which
is slidably mounted about the legs 31 which extend distally of proximal
portion 27. The distal portion 28 has a cammed surface 32 which slidably
engages distal ends 33 of the legs 31. A helically coiled spring 34 is
disposed in part about the proximal projection 35 on the distal portion
28. The proximal end 36 of the core element 11 passes through the handle
15 and is fixed by a suitable adhesive 37 to the proximal portion 27 of
the handle 15. The distal end 28 of the handle 15 is joined by a suitable
adhesive 38 to outer tubular element or hypotube 12 which passes
therethrough. The proximal end of the spring wire 34 is secured to the
proximal portion 27 by adhesive 37, as shown. The handle parts 27, 28, and
30 can be formed of suitable plastic material such as ABS.
The operation of the handle manipulator 15 is best shown in FIGS. 1 and 2.
In FIG. 1, the slidable collar 30 is in its most proximal position with
the coiled wire spring 34 being under slight tension to urge the proximal
portion 27 against the distal portion 28. In FIG. 2, the collar 30 has
been slid to its most distal position urging the legs 31 radially
inwardly, sliding the ends 33 thereof over cam surface 32. This movement
causes the proximal portion 27 to be moved proximally with respect to the
distal portion 28, thereby creating a differential longitudinal or axial
movement between the core element 11 and the outer tubular element or
hypotube 12 which effects the deflection of the distal tip 17 of the
guidewire 10. When the collar 30 is moved to its most proximal position,
as shown in FIG. 1, the tension on spring 34 returns the proximal section
27 to its original position which in turn returns the distal tip 17 to its
original position.
The relative axial movement between the core 11 and the outer tubular
element 12 compresses the expanded coil section 16 causing the reference
member 18 to be thrust toward the tip 17. However, because the distal end
of reference member 18 is secured to the plug 22, the reference member 18
bends toward the side of the coil 13 secured to the core element 11
causing tip deflection in that direction, as shown by the arrow 40. The
individual turns of the coil 13 proximal to the expanded coil section 16,
which are stacked adjacent to one another, and the hypotube 12 provide
columnar support to the coil so that relative axial movement between the
core element 11 and the hypotube 12 caused by the actuation of handle 15
will be transmitted to the distal end, resulting in the compression of
expanded section 16 of the coil and the desired deflection of tip 17. It
is preferred to coat the outer surface of the core 11 with lubricious
material, such as polytetrafluoroethylene (Teflon), to reduce friction. If
desired, the hypotube may be replaced by a continuation of the coil 13,
provided the coils thereof proximal to the expanded section 16 are stacked
adjacent to one another to provide columnar support.
The cam surface 32, is shown in FIGS. 1 and 2 in the form of a smooth
truncated conical section which provides for a continuous relative
movement of the core element 11 upon the movement of collar 30. However,
the cammed surface 32 can be provided with a series of steps in order to
provide a stepped axial movement of the core 11 with respect to the outer
tubular element 12 so that the amount of tip deflection can be determined
from the proximal end of the guidewire when the guidewire is in position
within a patient.
Typical dimensions of the core element 11 shown in FIGS. 1 and 2 include a
length of about 150 to 200 cm, a diameter (including any lubricious
coating) which ranges from about 0.008 to about 0.018 inch (0.203-0.457
mm) at the proximal end, and at the distal end 22 of generally rectangular
shape of 0.001 by 0.006 inch (0.0254 by 0.1524 mm) in transverse cross
section. The length of the coil 13 and the outer tube is approximately the
same as the core element 11. The expanded coil section 16 may vary in
length from about 0.1 to about 0.75 preferably about 0.2 to about 0.4 cm,
with the expansion ranging from about 50 to 100%, preferably about 70 to
100% of the stacked length thereof. The distal coil portion 26 is
preferably formed from radiopaque wire of about 0.0025 inch (0.0635 mm) in
diameter, whereas the expanded coil section 16 and the portion proximally
thereof are formed from stainless steel wire about 0.003 inch (0.0762 mm)
in diameter. Preferably, the mating ends of the coil sections are
intertwined or threaded together then bonded by soldering, brazing, or
other suitable means to the core element 11 at the intermediate location
23. The reference member 18 is preferably rectangularly shaped, formed of
stainless steel and has proximal dimensions of 0.002 by 0.004 inch (0.051
by 0.102 mm) and distal dimensions of 0.001 by 0.006 inch (0.025 by 0.152
mm).
FIGS. 5-11 illustrate other presently preferred embodiments involving the
incorporation of a guide member with a deflectable tip in accordance with
the invention into a dilatation catheter. The dilatation catheter assembly
45 includes an outer tubular member 46 having an inflatable balloon 47
near the distal end thereof and an inner tubular member 48 disposed within
the outer tubular member defining an annular passageway 50 therebetween
for directing inflation fluid to the inflatable balloon 47. The proximal
ends of the tubular members 46 and 48 are fixed to an adapter 51 and the
distal ends thereof are secured together at 52 to prevent leakage of
inflation fluid from the interior of the balloon 47.
The details of the deflectable tip construction of the catheter assembly 45
is best shown in FIG. 6, which has essentially the same construction as
that shown in FIG. 1, except that in the embodiment shown in FIG. 6 the
proximal end of coil 13 overlaps the distal end of the inner tubular
member 48 and abutts the distal portion of the outer tubular member 46
which provides columnar support for the relative core-coil movement
necessary for tip deflection. The dimensions of elements of the tip 17 are
essentially the same as those for the embodiments shown in FIG. 1. The
operation of the tip deflection for this embodiment is the same as
guidewire 10. Core element 11 is pulled axially in the proximal direction
causing the expanded coil section 16 to be compressed. Reference member 18
is thrust distally toward plug 22, but because it is secured thereto will
cause the tip to deflect as shown by arrow 40.
FIG. 11 illustrates in detail the core element manipulator 53 shown in FIG.
5 which is fundamentally equivalent to the handle 15 in the embodiment
shown in FIG. 1. It comprises a tubular extension 54, an insert 55
slidably disposed within the tubular extension 54, and a knob 57 on the
proximal end of the insert 55 to facilitate movement of the core element
11 secured thereto. A pair of O-rings 58 are provided about the periphery
of the insert 55 to seal the tubular extension 54 but allow axial movement
of the insert 55 mounted therein to effect tip deflection. Screw cap 56
secures tubular extension 54 to the proximal end of adapter arm 60. The
proximal end of core element 11 passes through arm 60 of adapter 51 and
the insert 55 and is fixed to the knob 57 by a suitable adhesive 62.
Pulling on the knob 57, as shown by arrow 40, causes tip deflection in the
same manner, as described for the embodiment shown in FIG. 1.
A further tip modification is depicted in FIG. 12 wherein the reference
element 18 is secured at a first location 20 proximal to expanded coil
section 16 and at a second location 21 intermediate between the expanded
coil section 16 and the plug 22. The distal end of the core element 11 is
secured to the coil 13 at an intermediate location 23 proximal to the
second location 27 but distally of the expanded coil section. Reference
element 18 passes through the solder or brazement at intermediate location
23 where the core element 11 is joined to the coil 13. The distal portion
of reference element 18 is secured to coil 13 at second location 21 by
brazement or solder 63 which also joins the core 13. The distal end of the
core element 11 is secured in the plug 22. The flattened section 24 of
core 11 is shown manually bent to a desired shape. The distal section of
the coil 13 is slightly expanded to provide flexibility.
The details of a particularly desirable inner tubular member 48 are shown
in FIGS. 7-10. In this embodiment, inner tubular member 48 includes a
hypotube 65 at the proximal portion thereof and secured to the distal end
of the hypotube is a high-strength plastic tubular element 66 formed of
polyimide. Preferably, both hypotube 65 and polyimide tubular element 66
are sized to have an inner lumen 67 along the length thereof with a
diameter of not more than about 0.003 inch (0.0762 mm) greater than the
diameter of the core element 11 disposed therein. This allows the inner
tubular member 48 to provide support to the core element as described in
copending application Ser. No. 000,646, filed Jan. 6, 1987, and assigned
to the present assignee. Additionally, essentially the entire inner lumen
67 of the inner tubular member 48 has a lining 68 formed of a lubricous
material, such as polytetrafluoroethylene, which is sold under the
trademark Teflon by DuPont. The transverse cross-sectional views shown in
FIGS. 7, 8, and 9 illustrate the variations in the length of the catheter
assembly 45. The close fit of the inner tubular member 48 about the core
11 which provides added support and the Teflon lining which reduces
considerably the force required to move the core 11 within the inner lumen
67 allows substantial reductions to be made in the diameter of the core
element 11. For example, core elements with maximum diameters of 0.01 inch
(0.254 mm) or less can be effectively employed with little risk of kinking
during the manipulation thereof and with excellent transmission of torque
from the proximal to the distal ends thereof.
The hypotube 65 may be made of suitable metallic material, such as type 304
stainless steel or nitinol which is a nickel-titanium alloy. Other
suitable materials may be used. The polyimide tubular element 66 of the
inner tubular member 48 is preferably Micro-Bore.TM. polyimide tubing
manufactured by PolyMicro Technologies of Phoenix, Ariz., which has a very
thin wall (i.e., 0.00075.+-.0.00024 inch).
While the description of the present invention has been described herein
primarily in terms of presently preferred embodiments, modifications and
improvements can be made without departing from the scope thereof.
* * * * *
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