U.S. patent application number 09/816952 was filed with the patent office on 2001-08-09 for apparatus and methods for selectively stenting a portion of a vessel wall.
Invention is credited to Deem, Mark E., Malisch, Timothy W..
Application Number | 20010012961 09/816952 |
Document ID | / |
Family ID | 22948845 |
Filed Date | 2001-08-09 |
United States Patent
Application |
20010012961 |
Kind Code |
A1 |
Deem, Mark E. ; et
al. |
August 9, 2001 |
Apparatus and methods for selectively stenting a portion of a
vessel wall
Abstract
Methods and apparatus for treating vascular abnormalities in
highly tortuous vessels are provided comprising a stent having at
least one end region that engages a first portion of a
circumference of a vessel in a region adjacent to an abnormality to
anchor the stent, and a mid-region that engages a second portion of
the circumference of the vessel wall to span the abnormality, the
second portion having a smaller circumferential extent than the
first portion. The mid-region includes a plurality of members that
span the abnormality and form a lattice that occludes the
abnormality. A delivery system also is provided to deliver the
stent within a parent artery and orient the mid-region of the stent
to span the abnormality.
Inventors: |
Deem, Mark E.; (San
Francisco, CA) ; Malisch, Timothy W.; (Chicago,
IL) |
Correspondence
Address: |
FISH & NEAVE
1251 AVENUE OF THE AMERICAS
50TH FLOOR
NEW YORK
NY
10020-1105
US
|
Family ID: |
22948845 |
Appl. No.: |
09/816952 |
Filed: |
March 22, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09816952 |
Mar 22, 2001 |
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09250710 |
Feb 16, 1999 |
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6231597 |
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Current U.S.
Class: |
623/1.15 |
Current CPC
Class: |
A61F 2/95 20130101; A61B
2017/12068 20130101; A61F 2002/075 20130101; A61F 2210/0019
20130101; A61F 2/91 20130101; A61F 2/885 20130101; A61B 17/12022
20130101; A61F 2002/823 20130101; A61F 2/07 20130101; A61F
2210/0033 20130101; A61F 2/92 20130101; A61F 2002/30092 20130101;
A61B 17/12118 20130101 |
Class at
Publication: |
623/1.15 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. Apparatus for treating an abnormality in a vessel, the apparatus
comprising: a tubular member configured to circumferentially engage
a first portion of a circumference of the vessel adjacent to the
abnormality; and a mid-region coupled to the tubular member, the
mid-region comprising a plurality of members having a convex outer
surface that engages a second portion of the circumference of the
vessel, the second portion smaller than the first portion, the
plurality of members spanning the abnormality.
2. The apparatus of claim 1 wherein the tubular member and the
mid-region comprise arcuate portions interconnected by a plurality
of bends or cusps.
3. The apparatus of claim 1 wherein the tubular member has a
longitudinal axis, the plurality of members oriented generally
perpendicular to the longitudinal axis.
4. The apparatus of claim 1 wherein the tubular member comprises a
coiled sheet.
5. The apparatus of claim 4 wherein the coiled sheet and mid-region
comprises a plurality of openings.
6. The apparatus of claim 1 wherein the first portion is
substantially equal to the full circumference of the vessel.
7. The apparatus of claim 1 wherein the first portion is less than
the full circumference of the vessel.
8. The apparatus of claim 1 wherein the plurality of members engage
one-half of the circumference of the vessel.
9. The apparatus of claim 1 wherein the tubular member and
mid-region further comprise a shape memory metal alloy or
biocompatible polymer.
10. The apparatus of claim 1 further comprising a graft material
covering the mid-region.
11. The apparatus of claim 1 further comprising a delivery system
comprising a first catheter having a distal end adapted to receive
the tubular member and mid-region, the first catheter having a
lumen and a first gear disposed within the lumen for orienting the
mid-region so that it spans the abnormality.
12. The apparatus of claim 11, wherein the first gear comprises a
lumen that permits a guide wire to extend beyond the distal end of
the first catheter into the vessel.
13. The apparatus of claim 11 further comprising a second catheter
configured for insertion into the lumen of the first catheter, the
second catheter having a distal end and a second gear disposed on
the distal end, the second gear configured to engage the first gear
when the second catheter is inserted in the lumen.
14. The apparatus of claim 13, wherein: the second gear comprises a
guide wire tip; and the first gear comprises a lumen that permits
the guide wire tip to extend beyond the distal end of the first
catheter into the vessel.
15. Apparatus for deploying a prosthesis to treat a region of a
vessel, the prosthesis having a feature that is aligned with the
region, the apparatus comprising: a flexible catheter having a
distal end adapted to receive the prosthesis, a lumen and a first
gear disposed within the lumen, the first gear rotating the
flexible catheter to orient the feature so that it is aligned with
the region.
16. The apparatus of claim 15 further comprising a torsion catheter
configured for insertion into the lumen of the flexible catheter,
the torsion catheter having a distal end and a second gear disposed
on the distal end, the second gear configured to engage the first
gear when the torsion catheter is inserted in the lumen.
17. The apparatus of claim 15, wherein the first gear comprises a
lumen that permits a guide wire to extend beyond the distal end of
the flexible catheter into the vessel.
18. The apparatus of claim 16, wherein: the second gear comprises a
guide wire tip; and the first gear comprises a lumen that permits
the guide wire tip to extend beyond the distal end of the first
catheter into the vessel.
19. The apparatus of claim 15 wherein: the first gear comprises a
cylindrical portion and a stepped portion having an engagement
surface; and the second gear comprises a cylindrical portion and a
stepped portion having an engagement surface that mates with the
engagement surface of the first gear.
20. The apparatus of claim 15 wherein the first gear further
comprises a longitudinally-oriented marker band.
21. The apparatus of claim 15 wherein the first catheter further
comprises an electrical conductor, the apparatus further comprising
a controller that supplies radio-frequency power to the second gear
via the electrical conductor.
22. The apparatus of claim 15 wherein the prosthesis is mounted on
the catheter by a thermally activated adhesive or polymer.
23. The apparatus of claim 15 wherein the prosthesis is mounted on
the catheter by an electrically erodible wire.
24. The apparatus of claim 15 wherein a retractable sheath retains
the prosthesis on the catheter.
25. A method of treating an abnormality at a treatment site within
a vessel, the method comprising: providing a stent having tubular
end region comprising at least one curved section having a convex
outer surface that engages a first portion of a circumference of
the vessel, and a mid-region comprising a plurality of members
having a convex outer surface that engages a second portion of a
circumference of the vessel, the second portion smaller than the
first portion; and transluminally disposing the stent at the
treatment site; and aligning the mid-region of the stent so that
the plurality of members span the abnormality.
26. The method of claim 25, further comprising: providing a
delivery system for deploying the stent, the delivery system
comprising a first catheter having a distal end configured to
receive the stent, a lumen, and a first gear disposed within the
lumen, wherein aligning the mid-region of the stent so that the
plurality of members span the abnormality comprises operating the
first gear to rotate the distal end of the first catheter.
27. The method of claim 26, wherein providing a delivery system for
deploying the stent further comprises providing a second catheter
having a proximal end, a distal end and a second gear disposed on
the distal end, the method further comprising: inserting the second
catheter into the lumen of the first catheter; and engaging the
second gear with the first gear, wherein operating the first gear
to rotate the distal end of the first catheter comprises rotating a
proximal end of the second catheter.
28. The method of claim 27 further comprising: providing a
controller that outputs a radio-frequency power; and coupling the
controller to the second catheter to release the stent from the
distal end of the first catheter.
29. The method of claim 26 wherein a thermally activated adhesive
or polymer retains the stent on the first catheter, and the method
further comprises selectively resistively heating a portion of the
first catheter to melt the adhesive or polymer to release the stent
from the first catheter.
30. The method of claim 26 wherein an electrically erodible wire
retains the stent on the first catheter, and the method further
comprises delivering electrical power to the electrically erodible
wire to release the stent from the first catheter.
31. The method of claim 26 wherein a retractable sheath retains the
stent on the first catheter, and the method further comprises
retracting the sheath to release the stent from the first catheter.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to apparatus and methods for
treating abnormalities or disease states in tortuous vessels. In
particular, this invention relates to stents and delivery systems
used to selectively support portions of a vessel wall, such as for
treating aneurysms and vascular dissections.
BACKGROUND OF THE INVENTION
[0002] Some forms of vascular abnormality or disease states, such
as aneurysms and vascular dissections, affect only portions of a
vessel. The term "abnormality," as used herein, refers to any
damage or disease state that affects a portion of a vessel wall. An
aneurysm, for example, is an area within an artery where the artery
wall integrity has become compromised by age, disease or trauma. As
a result, blood pressure within the artery causes a portion of the
artery wall to bulge or balloon. The portion of the aneurysm
attached to the undeformed wall of the parent artery is called the
"neck," and the bulbous pouch of the aneurysm is called the "dome."
The dome is considerably thinner and weaker than the undeformed
parent artery wall, and therefore is much more prone to
rupture.
[0003] A vascular dissection describes vessel damage in which a
portion of a vessel wall delaminates, and a flap of vascular tissue
may extend into and partially occlude blood flow in the parent
artery. In each of these different types of vascular abnormalities,
a portion of a vessel wall is damaged, but the remaining vessel
wall is otherwise healthy.
[0004] Vascular abnormalities can rupture and result in
debilitating injury or death, depending on the size and location of
the rupture and the amount of extra-arterial bleeding. For example,
an aneurysm located in the brain is called a cerebral aneurysm, and
hemorrhagic stroke results when a cerebral aneurysm ruptures. In
addition to the risk of stroke, large aneurysms located in certain
regions of the brain may result in neurologic problems due to so
called "mass effect." This effect is characterized by the enlarged
blood filled dome pressing upon important areas of the brain, and
may be manifested by symptoms such as seizure, or impaired speech
or vision.
[0005] Previously known methods for treating cerebral aneurysms
include extravascular and endovascular techniques. Extravascular
methods require delicate brain surgery to place a clip across the
neck of the aneurysm to effectively exclude the dome from blood
flow through the undeformed parent artery. Such surgical treatments
can be associated with high trauma, long recovery times, incomplete
recovery of all neurologic functions, morbidity and mortality
associated with open brain surgery. Additionally, aneurysms located
in some extremely sensitive areas, such as those surrounding the
brain stem, may be inoperable due to the high risk of
mortality.
[0006] Endovascular techniques, in contrast, treat aneurysms using
a microcatheter positioned within the aneurysm or the parent
artery. U.S. Pat. No. 5,122,136 to Guglielmi et al. describes one
such previously known endovascular technique using a device
commonly called a "Guglielmi Detachable Coil" (GDC). A GDC
comprises a soft pliable coil made from platinum or platinum alloy
that is soldered to a stainless steel coil and push wire. The
stainless steel coil and push wire are used to position the
platinum coil in the dome of the aneurysm, and position the
junction between platinum coil and stainless steel coil near the
neck of the aneurysm. A direct current (DC) is applied to the push
wire, stainless steel coil and platinum coil to form a thrombogenic
mass within the dome and thereby occlude the aneurysm.
[0007] By exposing the junction between the platinum coil and its
push wire coil to blood and continuing to apply electric current to
the push wire, the exposed portion of the stainless steel coil
electrolytically dissolves. The remaining portion of the stainless
steel coil and push wire then may be withdrawn from the artery,
leaving the platinum coil within the dome. Depending on the size of
the aneurysm, many such coils (typically from 5 to 20) may need to
be placed within the dome to prevent blood from entering the
aneurysm. Because pressure on the fragile dome is reduced, the risk
of rupture is eliminated or greatly reduced.
[0008] Endovascular treatment permits access to vascular lesions
through percutaneous introduction of microcatheters through the
femoral artery, and therefore involves less patient trauma than an
open surgical approach. This often results in a faster recovery and
reduced morbidity and mortality. Drawbacks of GDC techniques
include patient selection issues--the neck of the aneurysm must be
of a sufficient size and orientation to allow coil entry, but
prevent coil migration after detachment. Because multiple devices
often must be placed directly in the fragile dome, each device
introduction risks rupturing the dome due to mechanical trauma
induced by the device.
[0009] U.S. Pat. No. 5,135,536 to Hillstead describes a stent for
treating occlusive vascular disease comprising an expandable wire
tube having a reduced diameter for transluminal placement. Once the
stent is positioned within a vessel, a balloon catheter is used to
expand the stent to support and reinforce the full circumference of
the vessel. Such prior art stents typically have high radial
strength to resist collapse due to vessel disease. U.S. Pat. No.
5,314,444 to Gianturco describes a stent having similar
construction and operation.
[0010] Such previously known devices are not suitable for treating
vascular abnormalities, such as aneurysms, occurring in highly
tortuous vessels. For example, previously known endovascular stents
are designed to provide high radial strength when deployed, and
therefore generally are too rigid to negotiate the tortuous anatomy
of cerebral vessels. In addition, because a stent, once deployed,
is often overgrown by thick layer of vessel endothelium, a
phenomenon referred to as "neointimal hyperplasia," there is some
reduction of the vessel flow area after placement of the stent.
Such reduction in flow area may cause an unacceptable reduction of
blood flow in cerebral arteries. Some researchers believe that the
higher the percent coverage of an artery by a stent, the more
hyperplasia will occur.
[0011] As a result of the drawbacks of previously known
endovascular techniques, it is desirable to find an alternative
solution for treating vessels. In Wakhloo et al., "Self-Expanding
and Balloon-Expandable Stents in the Treatment of Carotid
Aneurysms: An Experimental Study in a Canine Model," Am. J.
Neuroradiology, 15:493-502 (1994), the authors describe the
feasibility of placing a stent across a portion of the neck of an
aneurysm to alter the hemodynamics and therefore induce spontaneous
clotting of stagnant blood within the dome. Those authors further
postulated that the struts of the stent covering the neck of the
aneurysm may provide a lattice for the growth of new endothelial
cells across the neck, permanently excluding it from blood flow
through the parent artery. Shrinking the aneurysm and resorption of
blood within the aneurysm are expected to follow, thus preventing
long-term mass effect problems.
[0012] In view of the foregoing, it would be desirable to provide
methods and apparatus to enable a stent to be atraumatically and
transluminally inserted into highly tortuous vessels, such as the
cerebral arteries.
[0013] It further would be desirable to provide methods and
apparatus for deploying a stent that spans a portion of a vessel to
provide a lattice for the growth of new endothelial cells across
the portion.
[0014] It also would be desirable to provide methods and apparatus
comprising a stent having sufficient radial strength to resist
downstream migration within the parent artery, but which is less
subject to narrowing of the vessel flow area.
SUMMARY OF THE INVENTION
[0015] In view of the foregoing, it is an object of this invention
to provide methods and apparatus to enable a stent to be
atraumatically and transluminally inserted into highly tortuous
vessels, such as the cerebral arteries.
[0016] It is another object of this invention to provide methods
and apparatus for deploying a stent that spans a portion of an
vessel to provide a lattice for the growth of new endothelial cells
across the portion.
[0017] It is a further object of the present invention to provide
methods and apparatus comprising a stent having sufficient radial
strength to resist downstream migration within the parent artery,
but which is less subject to narrowing of the vessel flow area.
[0018] These and other objects of the present invention are
accomplished by providing a stent and a delivery system for
implanting the stent. The stent comprises at least one end region
that engages a first portion of a circumference of a vessel in a
region adjacent to a vessel abnormality to anchor the stent, and a
mid-region that extends over a second portion of the circumference
of the vessel to span the abnormality, the second portion having a
smaller circumferential extent than the first portion. The
mid-region includes a plurality of members that span the
abnormality and form a lattice that occludes the abnormality. The
lattice also may be covered with a graft material, such as expanded
polytetra fluoroethylene (PTFE), or polyester mesh. Because the
mid-region extends over the smaller second portion of the
circumference, the stent is highly flexible and may result in
reduced narrowing of the flow area of the parent artery.
[0019] In accordance with the principles of the present invention,
a delivery system is provided comprising a catheter that enables
the mid-region of the stent to span the abnormality. In a preferred
embodiment, the catheter comprises a flexible outer catheter on
which the stent is releasably mounted, and an inner torsional
catheter that selectively engages the outer catheter to rotate the
stent to a desired orientation.
[0020] Methods of using the stent and delivery catheter of the
present invention are also provided.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Further features of the invention, its nature and various
advantages will be more apparent from the accompanying drawings and
the following detailed description of the preferred embodiments, in
which:
[0022] FIG. 1 is a perspective view of an illustrative embodiment
of a stent constructed in accordance with the principles of the
present invention;
[0023] FIG. 2 is an end view of the stent of FIG. 1;
[0024] FIG. 3 is a side view of a member forming the mid-region of
the stent of FIG. 1;
[0025] FIG. 4 is a perspective view of an alternative illustrative
embodiment of a stent constructed in accordance with the principles
of the present invention;
[0026] FIG. 5 is a side view of an illustrative embodiment of a
delivery system constructed in accordance with the principles of
the present invention;
[0027] FIG. 6 is a sectional view of a distal end of an outer
catheter of the delivery system of FIG. 5;
[0028] FIG. 7 is a perspective view, in isolation, of the first
torsion gear of FIG. 6;
[0029] FIG. 8 is a sectional view of an inner torsion catheter of
the delivery system of FIG. 5;
[0030] FIG. 9 is a perspective view of the second torsion gear of
FIG. 8;
[0031] FIG. 10 is a partial cutaway view of the delivery system of
FIG. 5;
[0032] FIG. 11A is a partial sectional view of the stent of FIG. 1
and the delivery system of FIG. 5 disposed within a vessel;
[0033] FIG. 11B is a partial sectional view of the stent of FIG. 4
and the delivery system of FIG. 5 disposed within a vessel;
[0034] FIG. 12 is a perspective view of an alternative embodiment
of the stent of the present invention;
[0035] FIG. 13 is a perspective view of another alternative
embodiment of the stent of the present invention;
[0036] FIG. 14 is a sectional view of an alternative inner torsion
catheter of the present invention;
[0037] FIG. 15 is a partial cutaway view of the inner tortion
catheter of FIG. 14;
[0038] FIG. 16 is a sectional view of another illustrative inner
torsion catheter of the delivery system of FIG. 5;
[0039] FIG. 17 is a perspective view of the second torsion gear of
FIG. 16; and
[0040] FIG. 18 is a partial cutaway view of the delivery system of
FIG. 5 using the inner torsion catheter of FIG. 16.
DETAILED DESCRIPTION OF THE INVENTION
[0041] The present invention provides methods and apparatus for
negotiating highly tortuous vessels to treat abnormalities located
therein, without suffering from the drawbacks of previously known
devices. More particularly, apparatus constructed in accordance
with the principles of the present invention includes a stent
having at least one end portion that engages a first portion of a
circumference of a vessel to anchor the stent, and a mid-region
having a plurality of members that extend over a second portion of
the circumference of a vessel to span the abnormality, the second
portion having a smaller circumferential extent than the first
portion. Although the mid-region of the stent is highly flexible,
care must be taken to orient the mid-region relative to the
abnormality. Accordingly, a delivery system is provided for
orienting the stent within the vessel during deployment.
[0042] Referring now to FIG. 1, an illustrative stent constructed
in accordance with the principles of the present invention is
described. Stent 10, shown in FIG. 1 in a deployed state, has a
longitudinal axis 12, mid-region 15 comprising a plurality of
elements 14, and first end 16 and second end 18. Elements 14 of
mid-region 15 are formed of a plurality of curved sections 20
joined by a plurality of bends or cusps 22. First and second ends
16 and 18 include curved sections 24.
[0043] When deployed in a vessel, curved sections 24 and 20
preferably have a convex outer surface and engage a first portion
and a second portion, respectively, of the circumference of the
vessel, the second portion smaller than the first portion. As shown
in FIG. 1, curved sections 24 engage a first portion equal to the
full circumference of the vessel, whereas curved sections 20 engage
a second portion less than the full circumference (e.g.,
one-quarter, one half or three-quarters, etc.). Curved sections 20
and 24 preferably are oriented generally perpendicularly to
longitudinal axis 12.
[0044] As illustrated in FIGS. 2 and 3, curved sections 24 form a
tubular member having central opening 26, whereas curved sections
20, which have the same deployed diameter as curved sections 24,
extend over only a portion of the circumference of the vessel.
Accordingly, when stent 10 is deployed in a parent vessel, curved
sections 24 at first and second ends 16 and 18 engage the interior
surface of a parent vessel adjacent to the neck of the aneurysm,
whereas curved sections 20 form a plurality of members that span
the abnormality to promote clotting and endothelial growth.
Advantageously, because mid-region 15 does not extend over the
entire circumference of the vessel when deployed, stent 10 is
highly flexible and provides less resistance to blood flow through
the parent artery.
[0045] Stent 10 preferably is constructed of a shape-memory
material such as nickel-titanium alloy (nitinol) having an
austenite phase transition temperature slightly above body
temperature. In this case, the stent may be cooled into the
martensite phase and compressed to a reduced delivery diameter, and
conditioned to undergo a heat-activated phase transformation to a
deployed, expanded state when heated to a temperature slightly
above body temperature. Alternatively, an electric current may be
applied to heat the stent to a temperature at which it transitions
to the austenite phase, and assumes an expanded shape.
Alternatively, the transformation temperature may be set below body
temperature, and the stent mechanically constrained.
[0046] Stent 10 may be formed, for example, by wrapping a nitinol
wire around a mandrel template, and then conditioning the wire
through a series of heat treatments in accordance with methods that
are per se known. Alternatively, stent 10 may be fabricated from
either nitinol or stainless steel tubing or sheets using previously
known electron discharge machining (EDM), chemical etching, or
laser cutting techniques. As a further alternative, stent 10 may be
formed from a biocompatible or bioerodible polymer.
[0047] FIG. 4 illustrates an alternative embodiment of a stent
constructed in accordance with the principles of the present
invention. Stent 101 is similar to stent 10, but includes cover 102
that spans elements 14 and is disposed about a portion of the
circumference of stent 101. Cover 102 may comprise a typical graft
material, such as polyester or expanded PTFE, and may be applied to
an exterior or interior surface of elements 14 using a
biocompatible adhesive or sutures. When stent 101 is deployed in a
parent vessel, cover 102 is oriented to span the abnormality to
promote clotting and endothelial growth.
[0048] Referring to FIG. 5, delivery system 30 for deploying a
stent of the present invention is described. As will be readily
apparent, the delivery system of the present invention
advantageously may be used whenever it is desired to align a
feature of a device with a region of a vessel. Delivery system 30
includes outer catheter 32 having proximal end 34 and distal end
36, inner torsion catheter 38 having proximal end 40 and distal end
42, and controller 44 coupled to proximal end of inner torsion
catheter 38 by insulated wires 46.
[0049] As illustrated in FIG. 6, outer catheter 32 preferably
comprises a highly flexible material, such as polyethylene,
silicone, nylon, polyester or polyurethane, having central lumen 52
that accepts guide wire 48 and has first torsion gear 50 mounted on
distal end 36. First torsion gear 50, shown in isolation in FIG. 7,
preferably comprises a radiopaque and conductive metal, metal
composite or metal alloy, and includes cylindrical portion 58,
stepped portion 60 having engagement surface 59, and lumen 62
extending through portions 58 and 60. Stent 10 is mounted adjacent
to distal end 36 of catheter 32, and/or first torsion gear 50, for
example, by a thermally activated adhesive or polymer, or
electrically erodible wire. Alternatively, a retractable sheath
could retain stent 10 on catheter 32, allowing stent 10 to expand
when the sheath is retracted.
[0050] Distal end 36 of outer catheter 32 also preferably includes
radio-opaque marker bands 54 disposed on outer surface 56, which
may be used to identify the longitudinal location of stent 10
relative to the neck of a target aneurysm, and
longitudinally-oriented marker band 57 on first torsion gear 50.
Marker band 57 enables the physician to determine the
circumferential orientation of stent 10 relative to the neck of an
abnormality, as described in greater detail below.
[0051] Referring to FIG. 8, distal end 42 of inner torsion catheter
38 is described. Inner torsion catheter 38 comprises tubular member
64 having second torsion gear 66 coupled to its distal end by clamp
ring 68. Insulated wires 46 extend from second torsion gear 66 and
through tubular member 64 to controller 44. Tubular member 64 is
flexible in the longitudinal direction, but is sufficiently rigid
to apply torque to second torsion gear 66. Tubular member 64
preferably comprises a combination of braided metal and metal alloy
wires enclosed within a polymer jacket and lubricious coating, or
alternatively, a helical coil and metal alloy wires covered with a
polymer jacket and lubricious coating. Tubular member 64 includes a
lumen or bore 70 for accepting a shank portion of second torsion
gear 66.
[0052] With respect to FIG. 9, second torsion gear 66, shown in
isolation, includes cylindrical portion 72, stepped portion 74
having engagement surface 75, and shank 76 extending from end face
78 of cylindrical portion 72. Shank 76 fits within bore 70 of
tubular member 64 so that when clamp ring 68 is applied, it secures
tubular member 64 to shank 76.
[0053] Second torsion gear 66 preferably comprises an electrically
conductive metal, metal composite or metal alloy that is
resistively heated when a radio-frequency ("RF") power is applied
from controller 44 through insulated wires 46. In this manner,
second torsion gear 66 may be selectively resistively heated by
controller 44, so that heat generated in second torsion gear 44 is
conducted to and melts the thermally activated adhesive or polymer
retaining stent 10 on outer catheter 32. Alternatively, second
torsion gear may be configured to electrically couple to first
torsion gear 50, to deliver power to an electrically erodible wire
that retains stent 10 on outer catheter 32.
[0054] As depicted in FIG. 10, engagement surface 75 of second
torsion gear 66 is configured to engage engagement surface 59 of
first torsion gear 50, so that rotation of inner torsion catheter
38 causes rotation of distal end 36 of catheter 32. Accordingly,
inner torsion catheter enables mid-region 15 of stent 10 to be
oriented so that it spans the neck of an aneurysm.
[0055] Referring now to FIGS. 11A and 11B, illustrative methods of
using the delivery system of FIG. 5 to deploy a preferred
embodiment of the stent of the present invention are described.
First, outer catheter 32 is percutaneously and transluminally
advanced over a guide wire to dispose distal end 36 in a portion of
vessel V containing aneurysm A using known radiological techniques.
Once stent 10 is disposed across neck N of aneurysm A, for example,
by determining the location of marker bands 54 with a fluoroscope,
the guide wire is withdrawn.
[0056] Inner torsion catheter 38 is inserted through hemostatic
coupling 80 of outer catheter 32 and then advanced and rotated
until second torsion gear 66 engages with first torsion gear 50.
Inner torsion catheter 38 is then rotated, for example, as guided
by radio-opaque marker band 57, until the convex portion of
mid-region 15 is aligned with and spans neck N of aneurysm A, as
depicted in FIG. 11A. More specifically, rotation of inner torsion
catheter 38 and outer catheter 32 may be as a unit. Alternatively,
because outer catheter 32 is more flexible than inner torsion
catheter 38, relative movement of inner torsion catheter 38 within
outer catheter 32 may simply cause the distal end of the outer
catheter to twist while the proximal end of outer catheter 32
remains stationary.
[0057] Controller 44 is then activated to cause an RF current to
flow through second torsion gear 66. In an embodiment where stent
10 is affixed to distal end 36 of outer catheter 32 by a thermally
activated adhesive or polymer, for example, a low temperature
biocompatible wax, the RF power delivered to second torsion gear 66
causes resistive heating of the distal end of the catheter, thereby
melting the thermally activated adhesive and permitting the stent
to expand to its deployed diameter. Delivery system 30 is then
withdrawn, leaving stent 10 with mid-region 15 disposed across neck
N of aneurysm A. Stent 10 serves to alter the hemodynamics within
aneurysm A to cause it to clot, and acts as a scaffold for
endothelial growth that excludes aneurysm A from vessel V.
[0058] Alternatively, in an embodiment where stent 10 is retained
on distal end 36 by an electrically erodible wire coupled to first
torsion gear 50, RF power supplied by controller 44 may be
delivered to and cause stent 10 to undergo a thermally activated
phase change to expand to its deployed state. Applying additional
power causes the erosion of the electrically erodible wire.
[0059] FIG. 11B illustrates deployment of stent 101 of FIG. 4. As
shown in FIG. 11B, during deployment, inner torsion catheter 38 is
rotated until cover 102 is aligned with and spans neck N of
aneurysm A. Once stent 101 expands to its deployed diameter, cover
102 acts as a scaffold for endothelial growth that excludes
aneurysm A from vessel V.
[0060] Other arrangements of insulating wires 46 and controller 44
will be apparent to one of skill in the art of interventional
catheter design. For example, in other embodiments, other release
mechanisms may be employed to release stent 10 from distal end 36
of outer catheter 32, such as the pull-wire arrangement described
in U.S. Pat. No. 5,443,500 to Sigwart, which is incorporated herein
by reference.
[0061] In still other embodiments, stent 10 may comprise an
elastically expandable, plastically deformable or super-elastic
material, rather than thermally-activated material, and may be
constructed using other shapes than the arcuate wire portions of
the embodiment of FIG. 1.
[0062] For example, as depicted in FIG. 12, stent 10 may comprise
first and second coil-sheet portions 91 and 92, respectively, such
as described in the above-incorporated patent to Sigwart,
interconnected by mid-region 93. Coil-sheet portions 91 and 92 and
mid-region 93 preferably comprise a mesh having a plurality of
openings 94, so that the lattice formed by openings 94 constitutes
a plurality of intersecting members 95. Coiled sheet portions 91
and 92 may be wound to a reduced diameter for transluminal
delivery, and then expanded (or permitted to self-expand) once
positioned within a vessel so that mid-region 93 spans the
abnormality. As shown in FIG. 12, when deployed, coiled-sheet
portions 91 and 92 engage a first portion equal to the full
circumference of the vessel, whereas mid-region 93 engages a second
portion of the circumference, the second portion less than the
first portion.
[0063] As shown in FIG. 13, stent 10 alternatively may comprise
first and second coiled expansile portions 96 and 97, respectively,
interconnected by mid-region 98. Coil-ring portions 96 and 97 and
mid-region 98 preferably comprise a mesh having a plurality of
openings 99, so that the lattice formed by openings 99 constitutes
a plurality of intersecting members 100. When deployed, coil-ring
portions 96 and 97 engage a first portion less than a full
circumference of the vessel, and mid-region 98 engages a second
portion of the circumference, the second portion less than the
first portion.
[0064] For certain applications, it may be desirable to keep a
guide wire or a guide wire tip in the vessel during stent
placement. In particular, the guide wire or guide wire tip may
provide additional stability during torquing of the inner and outer
catheters. FIGS. 14 and 15 illustrate a distal end of an
alternative embodiment of an inner torsion catheter that permits
catheter delivery and deployment with a guide wire in the
vessel.
[0065] As shown in FIG. 14, inner torsion catheter 103 comprises
tubular member 104 having second torsion gear 105 coupled to its
distal end. Tubular member 104 includes central lumen 106,
peripheral lumen 107 and bore 108. Peripheral lumen 107 terminates
at its distal end with opening 109 in a sidewall of bore 108.
Insulated wires 110 (one shown in FIG. 14) extend from second
torsion gear 105 and through peripheral lumen 107 to controller 44.
Tubular member 104 is flexible in the longitudinal direction, but
is sufficiently rigid to apply torque to second torsion gear 105.
Tubular member 104 preferably comprises a combination of braided
metal and metal alloy wires enclosed within a polymer jacket and
lubricious coating, or alternatively, a helical coil and metal
alloy wires covered with a polymer jacket and lubricious coating.
Bore 108 accepts a shank portion of second torsion gear 105.
[0066] As shown in FIGS. 14 and 15, second torsion gear 105
includes cylindrical portion 111, stepped portion 112 having
engagement surface 113, shank 114 extending from end face 115 of
cylindrical portion 111 and lumen 116 extending through shank 114,
cylindrical portion 111 and stepped portion 112. Shank 114 fits
within bore 108 of tubular member 104 and is secured to tubular
member 104 with a suitable adhesive, for example epoxy.
[0067] Second torsion gear 105 preferably comprises an electrically
conductive metal, metal composite or metal alloy. Insulated wires
110 are electrically bonded to shank 114, such as by soldering or
crimping. Second torsion gear 105 is resistively heated when RF
power is applied from controller 44 through insulated wires
110.
[0068] FIGS. 16-18 illustrate a distal end of a further alternative
embodiment of an inner torsion catheter having a guide wire tip. As
shown in FIGS. 16 and 17, second torsion gear 118 includes
cylindrical portion 119, stepped portion 120 having engagement
surface 121 and semi-circular bore 122, and guide wire tip 124
extending from front face 125 of cylindrical portion 119. Guide
wire tip 124 includes flexible coiled portion 126 and tapered tip
127. Proximal end 123 of guide wire tip 124 is engaged in
semi-circular bore 122 of stepped portion 120. Coiled portion 126
preferably comprises an electrically insulative, flexible helical
coil comprising a plastic or a metal alloy, such as stainless
steel, having an electrically insulative cover. Tapered tip 127 may
comprise a biocompatible material, such as nylon, disposed on the
distal end of coiled portion 126. Alternatively, guide wire tip 124
may comprise a short section of a conventional stainless steel
guide wire having an electrically insulative cover.
[0069] Second torsion gear 118 preferably comprises an electrically
conductive metal, metal composite or metal alloy that is
resistively heated when a radio-frequency RF power is applied from
controller 44 through insulated wires 46. As shown in FIG. 18,
engagement surface 121 of second torsion gear 118 is configured to
engage engagement surface 59 of first torsion gear 50. Guide wire
tip 124 extends through lumen 62 in first torsion gear 60.
[0070] Although preferred illustrative embodiments of the present
invention are described above, a person of ordinary skill in the
art will understand that various changes and modifications may be
made without departing from the invention. Applicants intend that
the appended claims cover all such changes and modifications that
fall within the true spirit and scope of the invention.
* * * * *