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BACKGROUND OF THE INVENTION
This invention generally relates to vascular catheters suitable for
maintaining the patency of a blood vessel after a vascular procedure
therein, such as angioplasty.
In typical percutaneous transluminal coronary angioplasty (PTCA)
procedures, a guiding catheter having a preformed distal tip is
percutaneously introduced into the cardiovascular system of a patient
through the brachial or femoral arteries and advanced therein until the
distal tip thereof is in the ostium of the desired coronary artery. A
guidewire and a dilatation catheter having a balloon on the distal end
thereof are introduced through the guiding catheter with the guidewire
slidably disposed within an inner lumen of the dilatation catheter. The
guidewire is first advanced out of the distal end of the guiding catheter
into the patient's coronary vasculature until the distal end of the
guidewire crosses the lesion to be dilated and then the dilatation
catheter is advanced over the previously positioned guidewire until the
dilatation balloon is properly located across the lesion. Once in position
across the lesion, the flexible, relatively inelastic balloon of the
dilatation catheter is inflated to a predetermined size (preferably the
same as the inner diameter of the artery at that location) with radiopaque
liquid at relatively high pressures (e.g., greater than about 4
atmospheres) to radially compress the atherosclerotic plaque of the lesion
against the inside of the artery wall to thereby dilate the lumen of the
artery. The balloon is then deflated so that the dilatation catheter can
be removed and blood flow resumed through the dilated artery.
Further details of angioplasty procedures and the devices used in such
procedures can be found in U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S.
Pat. No. 4,332,254 (Lindquist); U.S. Pat. No. 4,439,185 (Lundquist); U.S.
Pat. No. 4,168,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson);
U.S. Pat. No. 4,582,181 (Samson); U.S. Pat. No. 4,538,622 (Samson et al.);
U.S. Pat. No. 4,597,755 (Samson); U.S. Pat. No. 4,616,652 (Simpson); U.S.
Pat. No. 4,748,982 (Horzewski et al.); U.S. Pat. No. 4,771,778 (Mar); and
U.S. Pat. No. 4,793,350 (Mar et al.) which are hereby incorporated herein
in their entirety.
Frequently, the stenotic plaque or intima of the blood vessel or both are
dissected during the angioplasty procedure by the inflation of the
balloon, so that upon the deflation of the balloon a section of the
dissected lining, commonly termed a "flap," will collapse into the
bloodstream, closing off blood flow through the vessel and thereby
abruptly stopping or significantly reducing the passage of blood
therethrough. In these instances, emergency bypass surgery is usually
required to avoid a myocardial infarct distal to the blockage.
Conceivably, the dilatation catheter could be replaced with a perfusion
type dilatation catheter such as described in U.S. Pat. No. 4,790,315 in
order to hold the blood vessel open for extended periods. However,
perfusion type dilatation catheters have relatively large profiles which
can make advancement thereof through the blockage difficult and therefore
immediate bypass surgery may be the only means of avoiding an infarct
distal to the blockage or possibly even death. Additionally, the inflated
balloon of these perfusion catheters can block off a branch artery, thus
creating ischemic conditions in the side branch distal to the blockage.
Copending application Ser. No. 283,729 filed Dec. 13, 1988, now pending
describes an intravascular catheter having an expandable cage on the
distal end thereof which is designed to hold a detached lining against an
arterial wall for extended periods to facilitate the reattachment thereof.
However, this vascular device does not have means to readily advance and
withdraw the device over a guidewire.
What has been needed and heretofore unavailable is an easily advanceable
and removable low-profile intravascular device which can hold a collapsed
dissected lining or flap against the blood vessel wall for sufficient
length of time to allow the natural adhesion of the flap to the blood
vessel wall while simultaneously allowing for the perfusion of blood
distal to the catheter without blocking a branch artery. The present
invention satisfies this need.
SUMMARY OF THE INVENTION
This invention is directed to an improved vascular catheter which can hold
a blood vessel open for a long period of time after a vascular procedure
therein and which also allows for the perfusion of blood through the blood
vessel while the blood vessel is held open.
The vascular catheter in accordance with the present invention includes an
elongated catheter body formed by a tubular member having a first inner
lumen which extends through essentially the entire length of the body and
a second, much shorter lumen in the distal portion of the catheter body
which is adapted to receive a guiding member therein and which extends
through the distal portion from a proximal opening in the sidewall of the
distal portion to an opening in the distal end of the catheter body.
An expandable cage formed by a plurality of spirally arranged strands is
secured by the proximal end thereof to the distal end of the catheter
body. The distal end of the cage is provided with an opening which allows
for the passage of a guiding member therethrough.
A control wire extends through the first inner lumen of the tubular member
and the interior of the expandable cage with the distal end thereof
connected to the distal end of the expandable cage. A flexible tubular
guide, such as a coiled spring, is provided on the interior of the
expandable cage between the ends thereof to ensure the proper passage of
the guidewire therethrough. If not properly guided the guidewire can
diverge out of the expanded cage through the side thereof. Longitudinal
movement of the control wire adjusts the axial spacing between the
proximal and distal ends of the expandable cage and thereby changes the
radial dimension thereof. Preferably, the control wire is sufficiently
stiff so that movement thereof in the distal direction will cause the
expandable cage to elongate without bending or kinking the wire. This
eliminates the need for biasing the expandable cage in some manner to
return to an elongate state with minimal radial dimensions after the
expansion thereof to allow for the ready removal of the catheter from the
blood vessel. A suitable manipulator is provided on the proximal end of
the catheter assembly to longitudinally move the control wire within the
first lumen of the tubular member.
The relatively short, second inner lumen disposed within distal portion of
the tubular member is preferably defined in part by a sidewall in the
distal portion of the tubular member which is provided with an elongated
slot extending distally from the proximal hole in the sidewall to a
location proximally adjacent the proximal end of the expandable cage. This
slotted construction greatly facilitates the rapid exchange of the
vascular device of the invention over an in-place guidewire.
The proximal opening or port of the second inner lumen should be spaced
proximally more than about 15 cm but less than about 60 cm, preferably
from about 20 to about 50 cm, from the distal end of the catheter to
ensure that the proximal opening in the sidewall of the tubular body does
not extend beyond the distal end of the guiding catheter during a vascular
procedure because the guidewire tends to form a loop if not restrained in
some manner when the vascular catheter of the invention is pulled
proximally. Loop formation can interfere with the subsequent removal of
the catheter device through the guiding catheter.
In a presently preferred embodiment, the proximal portion of the tubular
body is provided with a third inner lumen which has disposed therein a
stiffening member or stylet which adds to the pushability of the catheter
and facilitates the advancement thereof through a patient's vascular
system.
The vascular catheter of the invention allows for the rapid advancement
thereof over a guidewire or other guiding member to a vascular location
wherein an occlusion has occurred. The cage when expanded will hold the
blood vessel open and simultaneously allow blood flow through the expanded
cage thereby eliminating or preventing ischemic conditions distal to the
occlusion. Importantly, the vascular catheter of the invention can be
mounted and withdrawn from an in-place guidewire without the use of
extension wires and the like which can greatly increase the overall time
for the procedure. These and other advantages of the invention will become
more apparent from the following detailed description thereof when taken
in conjunction with the accompanying exemplary drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view, partially in section, of an intravascular
catheter embodying features of the invention;
FIG. 2 is a transverse cross-sectional view of the catheter shown in FIG.
1, taken along the lines 2--2;
FIG. 3 is a transverse cross-sectional view of the catheter shown in FIG. 1
taken along the line 3--3;
FIG. 4 is a transverse cross-sectional view of the catheter shown in FIG. 1
taken along the lines 4--4; and
FIG. 5 is an elevational view of the intravascular device shown in FIG. 1,
wherein the guiding member is a steerable low-profile dilatation catheter.
DETAILED DESCRIPTION OF THE INVENTION
FIGS. 1-4 illustrate an intravascular catheter assembly 10 embodying
features of the invention. The assembly 10 generally includes an elongated
catheter body 11, an expandable cage 12 secured within the distal end of
the catheter body and a control wire or cable 13 for adjustment of the
axial distance between the proximal end 14 and distal end 15 of the
expandable cage 12 to vary the radial expansion thereof.
The elongated tubular member which forms the catheter body 11 has a first
inner lumen 17 which extends through essentially the entire length thereof
and which is adapted to receive control wire 13 and a second much shorter
inner lumen 20 in the distal portion of the catheter body 11 which extends
from side port 21 in the sidewall 22 of the tubular catheter body 11 to
port 23 provided in the distal end of the catheter body. A guiding member
24 is slidably disposed within the relatively short inner lumen 20 to
facilitate the rapid advancement and replacement of the catheter assembly
10. A longitudinal slit 25 is preferably provided in the sidewall 22 which
extends distally from the side port 21. A third inner lumen 26 may be
provided within the catheter body 11 which extends from a location
proximal to the side port 21 to essentially the proximal end of the
tubular member. A rod or stylet 27 fits within the third inner lumen 26 to
provide additional stiffness to the catheter assembly 10 proximal to the
side 21 to increase its pushability.
The expandable cage 12 is formed from a plurality spirally arranged wires
28, preferably of stainless steel or a radiopaque alloy such as
platinum-nickel alloy, which have diameters from about 0.001 to about
0.005 inch, preferably from about 0.002 to about 0.004 inch. The number of
wires 28 forming the cage 12 typically varies from about 4 to 20 wires.
Wires made from radiopaque materials such as platinum-nickel alloys should
be greater than 0.0025 inch in diameter in order to be observed within a
patient by fluoroscopic examination. A slightly stretched (e.g., 25%)
helical coil 29 is provided within the interior of the cage 12 between the
proximal and distal ends 14 ad 15 thereof to guide guiding member 24
through the interior the cage. The proximal, ends of the wires 28 are
bonded between an inner sleeve 30 and the inner surface of the second
inner lumen 20. The distal ends of the wires 28 are bonded together by
suitable means such as brazing, soldering or welding to form a collar 31.
The distal end of control wire 13 is also fixed to distal collar 31 so
that longitudinal or axial movement thereof adjusts the axial spacing
between the proximal and distal ends 14 and 15 of the cage thereby varying
the radial dimension thereof. The wires 28 of the cage 12 should have
sufficient strength and be used in sufficient numbers so that the cage is
capable of supporting an external pressure of at least about 4 psi to
ensure that a flap can be properly held in position within a patient's
artery.
The guidewire 24 comprises a core member 32, a helical coil 33 or other
flexible body disposed about and fixed to the tapered distal portion 34 of
the core member. A rounded plug 35, preferably formed of radiopaque
material, is provided at the distal tip of the coil 33. The construction
of the distal portion of the guidewire 24 can have a conventional
structure with the core member 32 extending through helical coil 33 to the
plug 35 or with the core member terminating short of the plug 35 and a
shaping ribbon (not shown) extending from the core member 32 to the plug
35. The guide member 24 extends through the second inner lumen 20 disposed
within the distal portion of the tubular member 16 and out the distal port
23, through the coiled guiding spring 29 which extends through the
interior of the expandable cage 12 and out the distal end thereof through
the distal collar 31. An incline or ramp 36 is provided at the proximal
end of the second inner lumen 20 at the entryway of side port 21 to
facilitate the insertion and withdrawal of the guidewire 24 therethrough.
The distance between the distal end 15 of the expandable cage 12 and the
side port 21 should be at least 15 cm but not greater than 60 cm,
preferably from about 20 to about 50 cm, so that when the cage is expanded
within a patient's vascular system to hold a blood vessel open, the side
port 21 of the catheter assembly 10 will remain within the interior of a
guiding catheter to ensure that the guiding member 24 does not have the
opportunity to form a loop when the catheter assembly 10 is pulled back
into the guiding catheter.
A manipulator adapter 38 is provided on the proximal end of the catheter
body 11 to effect longitudinal movement of the control wire 13. Internally
threaded cap 39 is secured to the proximal end of the manipulator housing
40. Axial rotation of the cap 39 causes the longitudinal movement of the
internal member 41, as shown by arrow 42, and as a result to control the
axial spacing between the ends 14 and 15 of the cage 12 and thus the
radial dimension thereof. If the control wire 13 is relatively stiff, it
can be employed to extend the ends 14 and 15 of the cage 12 away from one
another, elongating the cage so that it can be removed from a blockage. If
not, the wire 13 can be used to shorten the spacing between the ends 14
and 15, but the wires 28 of the cage can be formed in a biased condition
so that upon release of the handle 38, the cage 12 returns to its
elongated condition. An indicator 43 is provided on the internal member 41
to display the radial dimension of the cage 12.
Other means can be employed to return the expanded cage 12 to an elongated
condition. For example, as previously mentioned, a spring 39 provided
between the ends 14 and 15 may be biased to cause the same elongation.
Additionally, the cage can be formed of nitinol which has a "memory" to
allow the cage 12 to change shape with changes in temperature. An
electrical current can be passed through the wires to resistively heat the
wires and thereby change the shape thereof.
The manipulator 38 has a side arm 44 to inject heparinized saline or other
solutions through the first inner lumen 17 to keep the lumen free of blood
and to prevent the formation of thrombus in the inner lumen or in the
expandable cage 12. Further details of the manipulator 38 can be found in
copending application Serial No. 404,818, (now pending) filed Sept. 8,
1989 by the present inventors, entitled Expandable Cage Catheter with a
Rotatable Guide.
Generally, the dimensions of the catheter assembly of the invention are
essentially the same dimensions of vascular catheters used in angioplasty
procedures. The overall length of the assembly may be about 100 to about
175 cm. The diameter of the catheter body may range from about 0.035 to
0.06 inch. The expandable cage in the unexpanded condition has
approximately the same diameter as the catheter body but may be expanded
to a maximum diameter of about 1 to about 10 mm. The diameter of the first
inner lumen 17 will depend upon the size of the control wire 13 and the
amount of fluid which will be passed therethrough. The diameter of the
second inner lumen 17 should be sufficiently larger than the diameter of
the guiding member 24 to allow the catheter to be easily advanced and
removed over the guiding member.
In the operation of the catheter assembly 10, the distal end thereof is
mounted onto the proximal end of a guiding member 24 such as a guidewire
which has been positioned within the patient's vasculature with the distal
portion of the guiding member positioned across the occluded portion of
the arterial passageway. The proximal end of the guiding member is
advanced proximally through the central passageway provided in the distal
collar 31, guided through the interior of the expandable cage 12 by the
helical coil 29 through the port 23 leading into the second inner lumen,
through the second lumen, and then out the side port 21. The proximal
portion of the guiding member 24 extending out of the side port 21 is then
manually held while the catheter assembly 10 is advanced over the guiding
member through a previously positioned guiding catheter to a desired
location within the patient's blood vessel, such as where a prior vascular
procedure has been performed. The cap 39 on the manipulator 38 is rotated
to expand the cage 12 and thereby to press a flap which may be obstructing
the blood flow against the arterial wall and thereby maintain the patency
of the artery. The cage 12 is held in the expanded condition for
sufficient time, typically about 15 minutes to 24 hours, to allow the
dissected lining to heal with the flap being reattached to the artery
wall. Treatment periods of up to three days or more are believed to be
beneficial. During the period of cage expansion, blood flows readily
through the open weave structure of the cage so that no ischemia occurs
distal to the catheter either in the occluded artery or a side branch
thereof.
After the detached flap has been resecured to the artery wall, the expanded
cage 12 can be elongated by rotating the cap in a direction opposite to
the direction for expanding the cage to reduce the radial dimensions
thereof. Then the catheter assembly 10 can be removed from the location
within the patient's vasculature.
As the distal section of the catheter body emerges from the proximal end of
the guiding catheter, the guiding member 24 can be separated from the
second inner lumen by pulling the guidewire through the slit 25 which
extends from the side port 21 to a location adjacent the proximal end of
the wires 28 of the cage 12. This allows the guiding member to be manually
held exterior to the guiding catheter while the catheter assembly 10 of
the invention is being exchanged for another catheter device.
FIG. 5 illustrates an embodiment of the invention wherein the guiding
member 24 is a steerable low-profile dilatation catheter 50 which includes
a tubular member 51, a dilatation balloon 52 and a helical coil 53 which
is disposed about and secured to a core member 54. The proximal end of
core member 54 may be secured to the interior of the distal portion of
tubular member 51 or it may extend to the proximal end thereof. Further
details of steerable dilatation catheters which are suitable for use as
guiding members herein can be found in U.S. Pat. No. 4,582,181 (Samson);
U.S. Pat. No. 4,771,778 (Mar) and U.S. Pat. No. 4,793,350 (Mar et al.),
which have been previously incorporated herein, and copending application
Serial No. 289,919 filed Dec. 23, 1988, (now pending) entitled STEERABLE
DILATATION CATHETER which is hereby incorporated herein in its entirety by
reference. The operation and construction of these steerable dilatation
catheters are adequately described in the aforesaid references and need
not be repeated herein.
The catheter assembly of the invention is described herein to be employed
after an angioplasty procedure to hold open an artery when a dissected
portion of the arterial lining collapses and occludes the arterial lumen.
The assembly shown in FIG. 1 is particularly suitable for use with
angioplasty catheters (not shown) having removable guiding members 24 such
as disclosed in U.S. Pat. No. 4,323,071 previously referred to. The
embodiment shown in FIG. 5 on the other hand includes a guiding member
which is a low-profile steerable dilatation catheter. It will be
recognized by those skilled in the art that the catheter of the invention
can be used within a patient's vascular system after vascular procedures
other than angioplasty.
The catheter assembly of the invention may be formed of conventional
materials of construction. For example, the catheter body 11 can be made
of suitable plastic material such as polyethylene, polyvinylchloride,
polyesters and the like. The proximal portion is preferably formed of a
suitable metal such as stainless steel (i.e., hypotubing) to provide
additional pushability to the catheter assembly. The control wire 13 and
the wires 28 forming the cage 12 may be formed of stainless steel but may
be formed of other materials such as platinum-nickel alloys (e.g., 90 wt %
Pt.-10 wt % NI) or suitable plastics or even composites.
As can be appreciated, various modifications can be made to the present
invention. For example, the catheter assembly of the invention may be
provided with an inflatable dilatation balloon proximal or distal to the
expandable cage. In this manner after dilatation of a stenosis by such a
balloon, the position of the catheter assembly can be quickly shifted to
position the expandable cage thereof within the occlusion so it can be
expanded to hold open the arterial passageway for sufficient time to tack
up the flap against the arterial wall. Other modifications can be made to
the present invention without departing from the scope thereof.
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