U.S. patent application number 09/985498 was filed with the patent office on 2002-03-07 for implant deployment apparatus.
Invention is credited to Breton, Thomas G., Chan, Randy S., Leopold, Eric W., Pai, Suresh S., Thornton, Troy, Trautman, Joseph C..
Application Number | 20020029077 09/985498 |
Document ID | / |
Family ID | 25094855 |
Filed Date | 2002-03-07 |
United States Patent
Application |
20020029077 |
Kind Code |
A1 |
Leopold, Eric W. ; et
al. |
March 7, 2002 |
Implant deployment apparatus
Abstract
A delivery system including a restraining member maintains a
collapsed implant in its collapsed state for delivery through a
small passageway to a desired site in a mammalian body. Once the
implant is positioned at the desired site, the restraining member
is released so that the stent may expand or be expanded to its
expanded state. In a preferred embodiment, the restraining member
comprises a sheet of material that surrounds at least a portion of
the collapsed stent. Portions of the restraining member are
releasably coupled to one another with a low profile thread-like
member or suture.
Inventors: |
Leopold, Eric W.;
(Sunnyvale, CA) ; Trautman, Joseph C.; (Santa
Clara, CA) ; Thornton, Troy; (San Francisco, CA)
; Chan, Randy S.; (San Jose, CA) ; Pai, Suresh
S.; (Mountain View, CA) ; Breton, Thomas G.;
(Palo Alto, CA) |
Correspondence
Address: |
MORGAN & FINNEGAN, L.L.P.
345 Park Avenue
New York
NY
10154-0053
US
|
Family ID: |
25094855 |
Appl. No.: |
09/985498 |
Filed: |
November 5, 2001 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
09985498 |
Nov 5, 2001 |
|
|
|
08772373 |
Dec 23, 1996 |
|
|
|
Current U.S.
Class: |
623/1.11 ;
606/108 |
Current CPC
Class: |
A61F 2/848 20130101;
A61F 2/88 20130101; A61F 2002/067 20130101; A61F 2/90 20130101;
A61F 2220/005 20130101; A61F 2002/075 20130101; A61F 2/97 20130101;
A61F 2220/0075 20130101; A61F 2002/9511 20130101; A61F 2/9522
20200501; A61F 2220/0016 20130101; A61F 2/954 20130101; A61F 2/89
20130101; A61F 2230/001 20130101; A61F 2/07 20130101; A61F
2002/8486 20130101; A61F 2250/0059 20130101; A61F 2/9525
20200501 |
Class at
Publication: |
623/1.11 ;
606/108 |
International
Class: |
A61F 002/06 |
Claims
1. A delivery system for temporarily restraining an expandable
implant in a collapsed state for delivery to a deployment site,
said system comprising a sheet of material adapted and configured
for wrapping around an expandable implant to maintain said implant
in a collapsed state during delivery through a mammalian body
lumen, and a coupling member for coupling portions of the sheet to
one another to maintain said implant in said collapsed state.
2. The system of claim 1 wherein said sheet of material has a
length and a width, said width being less than about 40 mm.
3. The system of claim 1 wherein said sheet includes ends, side
margins extending between said ends, and an eyelet disposed along
each of said side margins.
4. The system of claim 3 wherein said eyelet is formed by a hole
formed in said sheet.
5. The system of claim 3 including a loop coupled to said sheet,
said loop forming said eyelet.
6. The system of claim 3 further including a reinforcing member,
said reinforcing member being disposed between one of said eyelets
and the outer perimeter of the side margin in which said eyelet is
disposed.
7. The system of claim 1 wherein said coupling member comprises a
thread adapted for threading through said eyelets.
8. The system of claim 7 wherein at least one of said side margins
comprises overlapping portions of said sheet, said reinforcing
member being positioned between said overlapping portions.
9. The system of claim 1 wherein said implant comprises a
stent.
10. An assembly comprising a stent and a restraining member coupled
to said stent, said stent having a collapsed and an expanded state,
said restraining member comprising a sheet of material adapted to
be wrapped around at least a portion of the stent when said stent
is in said collapsed state, and portions of said sheet being
adapted for coupling to one another to maintain said sheet wrapped
around at least or portion of said stent in its collapsed
state.
11. The assembly of claim 10 wherein said restraining member is
fixedly secured to said stent.
12. The assembly of claim 10 wherein said restraining member is
fixedly secured to said stent such that relative movement
therebetween is substantially prevented.
13. The assembly of claim 10 wherein said sheet has a length, width
and thickness, said width being less than the diameter of a portion
of said stent when said stent is in said expanded state.
14. The assembly of claim 10 wherein said sheet has a width that is
less than about 40 mm.
15. The assembly of claim 10 wherein the length of said restraining
member, measured along the longitudinal axis thereof, is less than
or equal to the length of said stent, measured along the
longitudinal axis thereof.
16. The assembly of claim 10 further including a discrete member
releasably coupling said portions to one another.
17. The assembly of claim 10 wherein said sheet includes ends and
side margins extending between said ends, said side margins being
releasably coupled to one another.
18. The assembly of claim 17 further including means for releasing
the coupling between said side margins.
19. The assembly of claim 17 further including means for
multidirectionally releasing the coupling between said side
margins.
20. The assembly of claim 10 wherein said sheet includes ends, side
margins extending between said ends, and at least one eyelet
disposed along each of said side margins.
21. The assembly of claim 20 wherein said eyelet is formed by a
hole formed in said sheet.
22. The assembly of claim 20 wherein said eyelet comprises a loop
coupled to said sheet.
23. The assembly of claim 20 further including a member releasably
coupling said eyelets to one another.
24. The assembly of claim 20 wherein each side margin includes
multiple eyelets, said device further including a thread passing
through said eyelets.
25. The assembly of claim 24 including multiple threads passing
through said eyelets.
26. The assembly of claim 20 wherein each side margin includes
multiple eyelets, said device further including a wire passing
through said eyelets.
27. The assembly of claim 26 including multiple wires passing
through said eyelets.
28. The assembly of claim 20 further including a reinforcing
member, said reinforcing member being disposed between at least one
of said eyelets and the outer perimeter of the side margin in which
said eyelet is disposed.
29. The assembly of claim 28 wherein at least one of said side
margins comprises overlapping portions of said sheet, said
reinforcing member being positioned between said overlapping
portions.
30. The assembly of claim 20 wherein the distance, measured along
said sheet between said side margins, is less than the diameter of
said stent when said stent is in said expanded state.
31. The assembly of claim 10 including multiple ones of said
restraining member.
32. The assembly of claim 10 wherein said stent is generally
cylindrical when in said expanded state.
33. The assembly of claim 10 wherein said stent has a bifurcated
configuration when in said expanded state.
34. The assembly of claim 10 wherein said sheet of material is
adapted for implantation within a human patient.
35. An assembly comprising a stent and a sheet of material, said
stent having a collapsed state and an expanded state, said stent
being in said collapsed state and having said sheet of material
wrapped around at least a portion thereof, said sheet having ends
and marginal side portions extending between said ends, said
marginal side portions being coupled to one another.
36. The assembly of claim 35 further including a discrete coupling
member, said coupling member coupling said marginal side portions
to one another.
37. The assembly of claim 35 wherein said sheet is arranged in
generally tubular form to maintain said stent in said collapsed
state.
38. The assembly of claim 35 wherein said sheet of material is
adapted for implantation within a human patient.
39. An assembly comprising a stent and a restraining member coupled
to said stent, said stent having a collapsed and an expanded state,
said stent having first and second portions that move relative to
one another when said stent moves between said collapsed and
expanded states, said restraining member comprising a sheet of
material adapted to be wrapped around at least a portion of the
stent when said stent is in said collapsed state, and portions of
said sheet being adapted for coupling to one another to maintain
said sheet wrapped around at least or portion of said stent in its
collapsed state, said assembly further including a member having a
first portion coupled to said restraining member and a second
portion coupled to one of said stent first and second portions.
40. The assembly of claim 39 wherein the relative circumferential
position of said first and second stent portions changes when said
stent moves between said collapsed to expanded state.
41. The assembly of claim 40 wherein the axial position of said
first and second stent portions axially changes when said stent
when said stent moves between said collapsed and expanded
states.
42. A method for delivering an expandable stent to a desired
endolumenal site in a mammalian body comprising the steps of: (a)
positioning an expandable stent which is restrained in a collapsed
state by a restraining member in a lumen having a wall, (b)
releasing said restraining member, and (c) urging said restraining
member into a position against said wall.
43. The method of claim 42 wherein the stent is a self-expanding
stent and it is allowed to self-expand to urge the restraining
member into a positions against said wall.
44. A method of preparing a stent for delivery to a desired site in
a mammalian body comprising the steps of: restraining a collapsed
stent in a sheet of material having side margins; and coupling said
side margins to each other.
45. The method of claim 44 wherein said coupling step comprises
coupling said side margins with multiple elements such that
multiple portions of the coupling between said side margins may be
released simultaneously.
46. A method for collapsing an expandable stent into a generally
tubular restraining member comprising the steps of: (a) pulling an
expandable stent through a tapered construct which radially
collapses the stent, and (b) pulling the stent into a generally
tubular restraining member.
47. The method of claim 46 wherein a portion of said stent is
folded before step (a).
Description
TECHNICAL FIELD
[0001] This invention relates generally to implants for repairing
ducts and passageways in the body. More specifically, the invention
relates to implant deployment apparatus.
BACKGROUND ART
[0002] Treatment or isolation of vascular aneurysms or of vessel
walls which have been thickened or thinned by disease has
traditionally been performed via surgical bypassing with vascular
grafts. Shortcomings of this procedure include the morbidity and
mortality associated with surgery, long recovery times after
surgery, and the high incidence of repeat intervention needed due
to limitations of the graft or of the procedure.
[0003] Vessels thickened by disease may be treated less invasively
with stents which mechanically hold vessels open. In some
instances, stents may be used subsequent to or as an adjunct to a
balloon angioplasty procedure. Stents also have been described in
conjunction with grafts where the graft is intended to provide a
generally smooth interface with blood flowing through the
vessel.
[0004] Generally, it is important that the stent or stent-graft be
accurately deployed so that it may be positioned at the desired
location. Endovascular stent or stent-graft deployment can be
summarized as a two-step process. The first step is moving the
stent within the vasculature to a desired location. The stent or
stent-graft may be self-expanding or balloon expandable. In both
cases, the implant is typically delivered in a collapsed state to
facilitate delivery through relatively small vessel lumens. The
second step involves some method of "locking" the stent or
stent-graft into its final geometry so that it will remain
implanted in the desired location.
[0005] A number of techniques for delivering self-expanding or
balloon expandable stents and stent-grafts are known. In the case
of a self-expanding stent or stent-graft, a restraining mechanism
typically is used to keep the stent or stent-graft in its collapsed
state during delivery. The restraining mechanism is later removed
to allow the stent or stent-graft to expand and engage the vessel
wall at the desired implantation site. In the case of a balloon
expandable stent or stent-graft, a restraining mechanism typically
keeps the expandable device in a collapsed position during delivery
with an inflatable balloon positioned within the collapsed device.
The restraining mechanism is later removed to allow for inflation
of the balloon which causes the stent or stent-graft to expand so
that it engages the vessel wall. Generally, tubular sheaths or
tying elements, which may be in the form of a filament or thread,
have been described to restrain the collapsed devices.
[0006] U.S. Pat. No. 4,878,906, to Lindemann et al., discloses
balloon expandable stent-grafts which are deployed through a
tubular sheath. The stent-grafts are forwarded in a collapsed state
along the vessel until they are in the correct location where the
sheath is withdrawn, allowing expansion of the balloon within the
stent-graft. After the balloon has expanded the stent-graft into
final position, the balloon is deflated and drawn back into the
tubular sheath. An alternative deployment method disclosed
Lindemann et al. dispenses with the tubular sheath and uses a
"thread" wrapped around the stent-graft and balloon which can be
withdrawn when balloon inflation is desired.
[0007] Pinchuk, U.S. Pat. No. 5,019,090, shows a helically wrapped
spring stent which is deployed with a balloon expansion catheter
through a "sheath" which holds the stent and balloon catheter in a
generally compressed state. Once the stent and balloon have been
forwarded into the correct position along a lumen, the sheath is
withdrawn. The balloon is then inflated, deflated, and withdrawn,
leaving the stent in final implantation position.
[0008] U.S. Pat. No. 5,246,452, to Sinnott, discloses a porous
vascular graft which is implanted with a tear-away removable
nonporous sheath. Once the graft has been forwarded into the
desired position, circulation is restored to the area and blood is
allowed to clot inside of the porous graft After five minutes of
clotting, the nonporous sheath can be removed by cutting or by
pulling a string which tears the sheath and pulls it away.
[0009] U.S. Pat. No. 5,344,426, to Lau et al., discloses an
expandable stent which is preferably self locking when expanded.
The stent is positioned over an expandable member such as a balloon
catheter and covered by a one or two layer sheath which is
connected to a guidewire. When the assembly of sheath, stent, and
expandable member has been forwarded to the desired position, the
sheath is removed by moving the guidewire distally. With the sheath
pulled off of the stent, the expandable member can be activated to
expand the stent into its final position.
[0010] U.S. Pat. No. 5,366,473, to Winston et al., discloses an
assembly in which a vascular graft is held in a compressed state
over a pair of stents by a sheath. The stents take the form of
flexible sheets wound around a spool. After the spool has been
inserted to the correct endovascular site, the sheath is withdrawn
allowing the stents to unwind and press the graft against the
vessel walls.
[0011] Strecker, U.S. Pat. No. 5,405,378, discloses an expandable
prosthesis which is held in radially compressed condition by a
releasable sheath. The sheath can be a strippable meshwork which
allows the compressed prosthesis to expand when the meshwork is
controllably unraveled.
[0012] Generally, the mechanisms described above involve a number
of components that may increase operational complexity. In
addition, the size and mechanical properties of these mechanisms
may limit deliverability of implants in small vessels. Delivery
accuracy also may be a problem as discussed.
[0013] The diameter of conventional telescoping stent sheaths may
contribute to undesirable friction with the delivery catheter as
the sheath is pulled from the stent and over a push rod during
deployment. This may make deployment accuracy difficult to control.
Push rods, which are used to push the stent through the delivery
catheter and which typically have a length of up to about 100 cm,
also may contribute to undesirable friction with the catheter. This
problem may be exacerbated where the catheter bends along its path
in the vasculature The sheath may also reposition the stent as it
is retracted.
DISCLOSURE OF THE INVENTION
[0014] The present invention generally involves a delivery system
for an implant, such as a stent or stent-graft. The delivery system
generally comprises a sheet of material adapted to extend around at
least a portion of a collapsed implant, such as a collapsed stent
or stent-graft. The sheet of material may form a tubular member
when extending around at least a portion of a collapsed member. The
system also may include a coupling member for coupling portions of
the sheet together to maintain the implant in its collapsed state
during delivery to a desired site in a mammalian body. With this
construction a smooth interface between the collapsed stent and a
vessel lumen, as compared to thread-like restraining members, may
be achieved.
[0015] According to another aspect of the invention, the sheet may
be constructed of a thin material which does not significantly
contribute to the structural rigidity or cross-sectional profile to
the delivery assembly. This construction may also eliminate the
need for external sheathing or a guide catheter and is believed to
advantageously increase the ability of the surgeon to deliver the
device to relatively remote sites and through small tortuous
vasculature. In addition, the sheet may comprise implantable
material so that after release it may remain with the stent at the
desired site.
[0016] According to another embodiment of the invention, an
assembly comprising a stent and a restraining member coupled to the
stent is provided. The stent has a collapsed and an expanded state
and the restraining member comprises a sheet of material adapted to
be wrapped around at least a portion of the stent when the stent is
in the collapsed state. Portions of the sheet are adapted for
coupling to one another to maintain the sheet wrapped around at
least or portion of the stent in its collapsed state. Thus, in one
configuration, portions of the sheet are releasably coupled to one
another so that the sheet maintains the stent in its collapsed
state.
[0017] According to another aspect of the invention, the portions
of the sheet that may be coupled to one another may be coupled with
a filament or thread-like member. The stent may be expanded (or
allowed to expand when a self-expanding stent is used) after the
thread-like coupling member is removed such as by being remotely
pulled by a pull line, which may be an extension of the coupling
member. Since the pull line may also have a thread-like low
profile, friction between with the catheter, through which the pull
line is pulled, and the pull line is minimized. It is believed that
such construction may further facilitate deployment accuracy.
[0018] According to another aspect of the invention, multiple
restraining members may be used. Alternatively, multiple coupling
members may be used to couple multiple portions of one of more
restraining members. These constructions can reduce deployment time
and may reduce the time in which fluid flow may disturb the
position of the implant as it is deployed.
[0019] According to another aspect of the invention an assembly
comprises a stent and a restraining member coupled to the stent.
The stent has a collapsed and an expanded state and first and
second portions that move relative to one another when said stent
moves between its collapsed and expanded states. The said
restraining member comprises a sheet of material adapted to be
wrapped around at least a portion of the stent when it is in its
collapsed state, and portions of the sheet being adapted for
coupling to one another to maintain said sheet wrapped around at
least a portion of the stent in its collapsed state. The said
assembly further includes a member having a first portion coupled
to the restraining member and a second portion coupled to one of
the stent first and second portions.
[0020] According to another aspect of the invention, an expandable
stent, which is restrained in a collapsed state with a restraining
member, is released and the restraining member urged against the
wall of the lumen in which the stent is placed. Since the
restraining member remains at the site, the number of deployment
steps can be reduced as compared to other techniques (e.g. pushing
a self-expanding implant out the end of a radially constraining
sheath and retracting the sheath).
[0021] According to another aspect of the invention, a method of
preparing a stent for delivery comprises restraining a collapsed
stent in a sheet of material which may be in the form of a tube and
coupling side margins of the tube.
[0022] According to another aspect of the invention, an expandable
stent (or stent-graft) is collapsed into a generally cylindrical or
tubular restraining by pulling the stent through a tapered member
and into a tubular restraining member.
[0023] The above is a brief description of some deficiencies in the
prior art and advantages of the present invention. Other features,
advantages, and embodiments of the invention will be apparent to
those skilled in the art from the following description,
accompanying drawings, and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a perspective view of a mammalian implant that is
restrained in a collapsed state in accordance with the principles
of this invention.
[0025] FIG. 2 is an end view of the restrained implant of FIG.
1.
[0026] FIG. 3 is a perspective view of the assembly of FIG. 1 with
the restraint released and the implant in an expanded state.
[0027] FIG. 4A is an end view of the assembly of FIG. 3.
[0028] FIG. 4B is a bottom plan view of the restraining member of
FIG. 4A.
[0029] FIG. 5A shows a restraining member retraction mechanism
according to another embodiment of the invention where the
mechanism is in an unactuated state.
[0030] FIG. 5B shows the mechanism of FIG. 5A in an actuated
state.
[0031] FIG. 5C shows a retraining member retraction mechanism
according to yet another embodiment of the invention where the
mechanism is in an unactuated state.
[0032] FIG. 5D shows the mechanism of FIG. 5C in an actuated
state.
[0033] FIG. 6A is a perspective view of another embodiment of the
implant in conjunction with the restraining member of FIG. 1.
[0034] FIG. 6B is a perspective view of a further embodiment of the
implant in conjunction with the restraining member of FIG. 1.
[0035] FIG. 7A illustrates the restraining and coupling member of
FIG. 1 and the pull direction for removing the coupling member from
the restraining member.
[0036] FIG. 7B shows the assembly of FIG. 7A with the coupling
member loosened to illustrate the chain knots used according to one
embodiment of the invention.
[0037] FIG. 7C diagrammatically represents release of the assembly
of FIG. 7A or 7B as the coupling member is pulled in the direction
shown.
[0038] FIGS. 8A, 8B, 8C, 8D, 8E and 8F diagrammatically show a
procedure for loading an expandable stent-graft into a restraining
member in accordance with the present invention prior to
endolumenal delivery.
[0039] FIG. 9A diagrammatically shows delivering a restrained
implant to a desired site in a mammalian body lumen in accordance
with the present invention with the coupling member configured as
shown in FIGS. 7A-7C.
[0040] FIG. 9B is a sectional view of FIG. 9A taken along line
9B-9B.
[0041] FIG. 9C shows an alternate multiple restraining member
arrangement for that shown in FIG. 9A.
[0042] FIG. 10A diagrammatically shows partial deployment of the
implant assembly illustrated in FIG. 9A showing progressive
expansion in a direction away from the distal end of the
illustrated guidewire (i.e., toward the illustrated hub).
[0043] FIG. 10B is a sectional view of FIG. 10A taken along line
10B-10B.
[0044] FIG. 11A diagrammatically shows full deployment of the
implant assembly illustrated in FIG. 9A.
[0045] FIGS. 12A, 12B, 12C and 12D diagrammatically show deployment
of a restrained implant according to another embodiment of the
invention where the coupling member configuration provides release
from the middle portion of the implant outward toward the implant
ends.
[0046] FIG. 13 illustrates one coupling member configuration for
deployment as shown in FIGS. 12A-12D.
[0047] FIG. 14A is a perspective view of a bifurcated stent-graft
that can be used with the illustrated delivery systems.
[0048] FIG. 14B is a top plan view of the bifurcated stent-graft of
FIG. 14A.
[0049] FIG. 14C is a cross-section view taken along section line
14C-14C depicted in FIG. 14A.
[0050] FIG. 14D is a cross-sectional view taken along section line
14D- 14D depicted in FIG. 14A showing an alternate embodiment.
[0051] FIG. 15 is a front view of the assembled bifurcated
stent-graft of FIG. 14A placed at a bifurcation site within the
vasculature of a body.
[0052] FIG. 16 is a perspective break-away view showing a close-up
of one construction of stent anchoring apexes.
[0053] FIG. 17 is a perspective break-away view showing a close-up
of a preferred construction of the stent anchoring apexes.
[0054] FIG. 18 is a cross-sectional view of the stent-graft of FIG.
14B taken along section line 18-18.
[0055] FIG. 19 is a cross-sectional view of the stent-graft of FIG.
14A taken along section line 19-19.
[0056] FIG. 20 is an enlarged partial cross-sectional view of the
contralateral leg connection depicted in FIG. 19.
[0057] FIG. 21 and FIG. 22 are enlarged partial cross-sectional
views of alternative constructions of the receiving lumen.
[0058] FIG. 23 is a partial perspective view of an alternate
scalloped construction of the proximal region of the contralateral
leg component.
[0059] FIGS. 24A and 24B are cross-sectional views taken along
section line 24A-24A as shown in FIG. 14A depicting a free state
and a forced state respectively.
[0060] FIGS. 25A and 25B are cross-sectional views taken along
section line 25A-25A as shown in FIG. 23 depicting a free state and
a forced state respectively.
[0061] FIG. 26 is a front view of preassembled graft
components.
[0062] FIGS. 26B and 26C are respectively the front view and top
view of the assembled graft of FIG. 26A.
[0063] FIG. 27A is a front view of the unassembled components of an
alternate construction of the graft element.
[0064] FIG. 27B is a front view of the assembled graft element
according to the alternative construction of FIG. 27A.
[0065] FIGS. 28A through 28E diagrammatically show deployment of a
bifurcated stent-graft.
[0066] FIGS. 29A, 29B and 29C diagrammatically show deployment of a
bifurcated stent-graft using an alternate delivery system.
DETAILED DESCRIPTION
[0067] Referring to the drawings in detail wherein like numerals
indicate like elements, delivery systems for delivering implants or
devices, such as stents or stent-grafts, to a desired site in
mammalian vasculature are shown in accordance with the principles
of the present invention. The delivery systems of the present
invention generally include a restraining member that is adapted
and configured for surrounding at least a portion of a collapsed or
compressed implant and a coupling member(s) for releasably coupling
portions of the restraining member to one another to maintain the
implant in its collapsed or compressed state.
[0068] Referring to FIGS. 1-4, an implant delivery system
constructed in accordance with the present invention is shown.
Delivery system (100), generally includes a restraining member
(102), which as shown may be in the form of a sheet of material,
and a coupling member (104) for releasably coupling portions of the
restraining member to one another. The restraining member portions
that are coupled may differ than those illustrated, but preferably
are selected to maintain the implant, such as self-expanding
stent-graft (106), in a collapsed or compressed state as shown in
FIGS. 1 and 2 where the restraining member (102) is shown in the
form of a tube. In the illustrative embodiment, the coupling member
(104) is shown as a filament or thread-like element which prevents
the restraining member (102) from rearranging to a configuration
where the stent-graft (106) could expand to its expanded state.
[0069] The implant may be collapsed in any suitable manner for
placement within the restraining member (102). For example, the
implant may be folded or radially crushed before placement within
the restraining member (102) as will be described in more detail
below. As shown in FIGS. 9-11, a delivery assembly (108), which
includes the restraining member (102) and the stent-graft (106),
has relatively small cross-sectional dimensions which facilitate
endolumenal delivery of the assembly to a site where the natural
lumen diameter may be smaller than the expanded diameter of the
stent-graft (106).
[0070] Referring to FIGS. 3 and 4A, the assembly (108) is shown in
a deployed state after removal of the coupling member (104). The
restraining member (102) may be fixedly secured to the stent-graft
(106) so that the two components remain attached after expansion at
the desired deployment site. The attachment between the restraining
member and the implant preferably is made to prevent significant
movement between the restraining member and stent-graft after
deployment which could disrupt endovascular fluid flow. Referring
to FIGS. 4A and 4B multiple sutures (110) may be used to fixedly
attach the restraining member (102) to the stent-graft (106). More
specifically, the sutures can form loops that pass through the
restraining member and around portions of the stent as shown in
FIG. 4A. It is further noted that although one arrangement of the
sutures (110) is shown in FIG. 4B other arrangements may be
used.
[0071] Although other configurations of the restraining member
(102) can be used, a preferred configuration is a generally
rectangular one having constant width as shown in FIG. 4B. For
example, in the case where the restraining member is used in
conjunction with a modular bifurcated stent as will be described
below, the restraining member may have a similar rectangular
configuration as that shown in FIG. 4B. Alternatively, it may have
two differently sized rectangular portions arranged to mate with
the regions of different diameter (trunk and leg) or another
configuration that would maintain the implant in a collapsed stent
when secured. Returning to FIG. 4B, the restraining member may be
described as having side margins (112) that extend between the ends
(114) of the member. Eyelets (116) are disposed along the side
margins so that the coupling member (104) may be laced or threaded
therethrough. The eyelets may be in the form of through holes
(118), which may be formed by a uniform-diameter puncturing device
or by other means such as laser-drilling. Alternatively, the
eyelets may be formed by loops (120) which may be attached to the
side margins (112) or formed by other means as would be apparent to
one of ordinary skill in the art.
[0072] It is further desirable to have structural reinforcement at
the side margins (112) to minimize or eliminate the possibility of
the coupling member (104) from tearing the restraining member (102)
when under load. Reinforced side margins may be formed by folding a
portion of the restraining member (102) over a reinforcement member
(122), such as a small diameter suture, which may be heat bonded
between the two layers of sheet material. With this construction, a
relatively low profile bead of material along the side margins
(112) prevents or minimizes the possibility of tear propagation
and, thus, accidental uncoupling of the restraining member (102).
The small diameter suture (122) may comprise ePTFE, for
example.
[0073] As the restraining member (102) constrains a collapsed
self-expanding stent-graft, for example, forces resulting from
stored spring energy in the collapsed stent-graft (106) will be
acting on the restraining member (102) when it is configured for
delivery. Thus, according to another aspect of the invention the
restraining member (102) may comprise a material which is creep
resistant and can withstand required loads without stretching over
time. The restraining member (102) may comprise, for example,
ePTFE, which is believed to provide suitable creep resistance,
flexibility, and biocompatibility in a thin sheet form which can be
heat bonded. Other materials also may be used including polyethers
such as polyethylene terepthalate (DACRON.RTM. or MYLAR.RTM.) or
polyaramids such as KEVLAR.RTM..
[0074] The thread-like coupling member (104) may also comprise
ePTFE. Sutures of polyethers such as polyethylene terepthalate
(DACRON.RTM. or MYLAR.RTM.) or polyaramids such as KEVLAR.RTM. or
metal wire comprising nitinol, stainless steel or gold may also be
used for the coupling member (104). The coupling member (104) may
simply extend to form a remote pull line as will be discussed
below. Alternatively, a metallic pull line, such as one comprising
stainless steel may be coupled to a nonmetallic coupling member
(104) such as one comprising ePTFE. The coupling may be made by
folding the end of the metallic pull line back upon itself to form
an eyelet and threading the coupling member therethrough and
securing it to the eyelet with a knot.
[0075] It is further noted that the width of the restraining
member, when in a flat orientation as shown in FIG. 4A, preferably
is less than the diameter of the implant. Typically the restraining
member width will be less than about 40 mm (typically about 25-40
mm when the device is sized for thoracic aorta applications), and
typically less than about 15 mm in other applications where the
lumen is smaller. The sheet of material preferably has a thickness
less than 0.010 inch (0.254 mm) and more preferably less than 0.005
inch (0.127 mm). In addition, the length of the restraining member
preferably is less than or equal to that of the implant.
[0076] According to the present invention, a retraction assembly
may be provided to retract the restraining member during expansion
of the implant, so that the length of the restraining member is
maintained to be about equal to or less than that of the implant.
The expandable portion of the implant may undergo minor amounts of
shortening along the axial direction due to the expansion thereof
in the radial direction, which may lead to an overlap of the
restraining member at the ends of the implant, but for the use of
some type of retraction assembly in these situations. The
retraction assembly minimizes or eliminates the risk of the
restraining member extending beyond the implant and interfering
with any channel formed by the implant, or any fluid flowing
therethrough after expansion.
[0077] Referring to FIGS. 5A-5D, retraction assemblies or
mechanisms constructed according to the principles of the invention
are shown. In FIG. 5A, a retraction assembly (340) is shown
including a biocompatible filament (342), which includes a portion
that is stitched, tied or otherwise fixed to the restraining member
(102), as shown at an attachment point (348), adjacent to one end
of the restraining member. Filament (342) is passed underneath the
members forming the first or end helical turn of the stent (126)
and looped under or otherwise slidably secured to a portion of the
second, third or another helical turn other than the first helical
turn such a an apex or bend portion (344) in a second turn. The
other end portion of filament (342) is further fixed, by tying or
other means, to a portion of the stent that is circumferentially
spaced from the attachment point (348) or the apex or bend portion
(344), for example, such as an apex or bend portion (346) of the
same helical turn. Preferably, the filament (342) is looped through
an apex portion (344) of the second helical turn and tied to an
apex portion (346) which is adjacent to the apex portion (344) as
shown in FIG. 5A.
[0078] FIG. 5A shows the stent in the compressed state. Upon
expansion of the stent, as mentioned above, the members of the
stent expand to effect the radial expansion of the stent, as shown
in FIG. 5B. Because the distance between apex portions (344) and
(346) becomes greater upon expansion of the stent, and because the
filament (342) is relatively unyieldable and inelastic, the
distance between the attachment point (344) and the apex portion
(348) necessarily decreases. The result is that the end of the
restraining member (102) is retracted with respect to the stent
(126), as shown in FIG. 5B. Thus, the retraction along the
longitudinal axis of the restraining member is driven by the
expanding distance between adjacent apexes in this embodiment.
Although only one retraction mechanism is shown at one end of the
restraining member, another similarly configured and arranged
retraction mechanism may be used at the other end of the
restraining member.
[0079] FIGS. 5C and 5D show another embodiment for a retraction
assembly. The views of this assembly (as are those shown in FIGS.
5A and 5B) are taken from a location between the generally
cylindrical graft and stent looking radially outward. In contrast
to that shown above where one end portion of a filament is secured
to the restraining member and another to a portion of the stent
that circumferentially moves during stent expansion, the other end
of the filament is secured to a portion of a stent that moves
generally parallel to the longitudinal axis of the stent (axially)
as the stent expands. In this embodiment, at least one apex portion
(364) of an end helix of the stent member (126') (which differs
from stent (126) in that it includes eyelets or loops which may be
formed as shown in the drawings) is made shorter than the majority
of apex portions (366). However, the apex portions may be otherwise
configured such as those shown in FIGS. 4A and 4B. A filament (362)
is tied or otherwise fixed at one end to apex portion (364), and at
the other end, to one end portion of the restraining member (102).
As shown in FIG. 5D, upon radial expansion of the stent, inwardly
positioned apex portion (364) retracts to a greater extent in the
longitudinal or axial direction than the full height apex portions
(366) which are shown in the last or most outwardly positioned turn
of the stent. This relative greater retraction directly translates
through filament (362) such that the end of the restraining member
(102) is retracted relative to apex portions (366). As described
above, another similarly constructed retraction mechanism may be
provided at the other end of the restraining member.
[0080] Returning to FIG. 1, one stent-graft construction that may
be used in conjunction with the delivery systems disclosed herein
is shown. Stent-graft (106) generally includes a thin-walled tube
or graft member (124), a stent member (126), which can be a
self-expanding stent, and a ribbon or tape member (128) for
coupling the stent (126) and graft (124) members together. The
stent (126) and graft (124) members may be heat bonded together,
thus sealing in portions of the stent member (126) that are between
the tape member (128) and the graft member (124). The mechanical
properties of the stent-graft (128) may be customized, for example,
through materials selection, by varying the structural pattern of
the stent member, varying the thickness of the tape (128) and graft
(124) members, and varying the pattern with which the tape member
contacts the stent and graft members.
[0081] As shown in FIG. 1A, the tape member (128) may cover only a
portion of the stent member (126) as it follows the helical turns
of the undulating stent member. With this construction, regions of
the stent member do not interface with the tape member when the
stent-graft is in an uncompressed state, for example. This is
believed to advantageously reduce shear stresses between the stent
member (126) and the tape member (128) when the stent-graft
undergoes bending or compression, thereby reducing the risk of
tearing the graft (124) or tape (128) members or causing
delamination between the stent (126) and graft (124) members.
[0082] The tape member (128) also preferably has a generally broad
or flat surface for interfacing with the stent (126) and graft
(124) members as compared to filament or thread-like structures
such as sutures. This increases potential bonding surface area
between the tape member (128) and the graft member (124) to enhance
the structural integrity of the stent-graft. The increased bonding
surface area also facilitates minimizing the thickness of the tape
member (128). It has been found that a tape member in the form of a
generally flat ribbon as shown in the drawings provides desired
results.
[0083] Tape members having widths of 0.025, 0.050 and 0.075 inches
applied to a stent member having a peak-to-peak undulation
amplitude of about 0.075 inch are believed to provide suitable
results. However, it has been found that as the tape member band
width increases, the stent-graft flexibility generally is
diminished. It is believed that a tape member width of about
one-fourth to three-fourths the amplitude of the stent member
undulations, measured peak-to-peak, may be preferred (may be more
preferably about one-third to two-thirds that amplitude) to
optimize flexibility. It also has been found that by positioning
one of the lateral margins of the tape member adjacent to the
apexes, the tape member width may be reduced without significantly
sacrificing apex securement. Varying the width of the tape member
(e.g., varying width of the tape along the length of the stent
graft) can also result in the adjustment of other structural
properties. Increasing the width can also potentially increase the
radial stiffness and the burst pressure and decrease the porosity
of the device. Increasing band width can also diminish graft member
wrinkling between coupling member turns.
[0084] The tape member (or separate pieces thereof) also may
surround the terminal end portions of the stent-graft to secure the
terminal portions of the graft member to the stent member.
[0085] FIGS. 6A and 6B illustrate further stent-graft constructions
that may be used with the delivery systems described herein.
Referring to FIG. 6A, stent-graft (200) is the same as stent-graft
(106) with the exception that stent-graft (200) includes a filament
that couples stent undulations in adjacent turns. Filament (202) is
laced or interwoven between undulations of the stent member and
acquires a helical configuration (i.e., it forms a secondary helix)
in being laced as such. Such a configuration is disclosed in PCT
publication No. WO 95/26695 (International Application Ser. No.
PCT/US95/04000) the entirety of which is hereby incorporated herein
by reference. The stent-graft (300) shown in FIG. 6B is the same as
that shown in FIG. 6A with the exception that the filament (302) is
interwoven between undulations in the same helical turn of the
stent member.
[0086] The filaments (202, 302) are of the same construction and
may be of any appropriate filamentary material which is blood
compatible or biocompatible and sufficiently flexible to allow the
stent to flex and not deform the stent upon folding. Although the
linkage may be a single or multiple strand wire (platinum,
platinum/tungsten, gold, palladium, tantalum, stainless steel,
etc.), much preferred is the use of polymeric biocompatible
filaments. The flexible link may be tied-off at either end of the
stent-graft (100), for example, by wrapping its end portion around
the stent and tying it off at the point at the beginning of the
last turn as would be apparent to one of ordinary skill.
[0087] A percutaneously delivered stent-graft must expand from a
reduced diameter, necessary for delivery, to a larger deployed
diameter. The diameters of these devices obviously vary with the
size of the body lumen into which they are placed. For instance,
the stents of this invention may range in size from 2.0 mm in
diameter (for neurological applications) to 40 mm in diameter (for
placement in the aorta). A range of about 2.0 mm to 6.5 mm (perhaps
to 10.0 mm) is believed to be desirable. Typically, expansion
ratios of 2:1 or more are required. These stents are capable of
expansion ratios of up to 5:1 for larger diameter stents. Typical
expansion ratios for use with the stents-grafts of the invention
typically are in the range of about 2:1 to about 4:1 although the
invention is not so limited. The thickness of the stent materials
obviously varies with the size (or diameter) of the stent and the
ultimate required yield strength of the folded stent. These values
are further dependent upon the selected materials of construction.
Wire used in these variations are typically of stronger alloys,
e.g., nitinol and stronger spring stainless steels, and have
diameters of about 0.002 inches to 0.005 inches. For the larger
stents, the appropriate diameter for the stent wire may be somewhat
larger, e.g., 0.005 to 0.020 inches. For flat stock metallic
stents, thicknesses of about 0.002 inches to 0.005 inches is
usually sufficient. For the larger stents, the appropriate
thickness for the stent flat stock may be somewhat thicker, e.g.,
0.005 to 0.020 inches.
[0088] The following example is provided for purposes of
illustrating a preferred method of manufacturing a stent-graft as
shown in FIG. 3. It should be noted, however, that this example is
not intended to limit the invention. The stent member wire is
helically wound around a mandrel having pins positioned thereon so
that the helical structure and undulations can be formed
simultaneously. While still on the mandrel, the stent member is
heated to about 460.degree. F. for about 20 minutes so that it
retains its shape. Wire sizes and materials may vary widely
depending on the application. The following is an example
construction for a stent-graft designed to accommodate a 6 mm
diameter vessel lumen. The stent member comprises a nitinol wire
(50.8 atomic % Ni) having a diameter of about 0.007 inch. In this
example case, the wire is formed to have sinusoidal undulations,
each having an amplitude measured peak-to-peak of about 0.100 inch
and the helix is formed with a pitch of about 10 windings per inch.
The inner diameter of the helix (when unconstrained) is about 6.8
mm. (The filament when used as shown in FIGS. 6A and 6B may have a
diameter of about 0.006 inch.)
[0089] In this example, the graft member is porous expanded
polytetrafluorethylene (PTFE), while the tape member is expanded
PTFE coated with FEP. The tape member is in the form of a flat
ribbon (as shown in the illustrative embodiments) that is
positioned around the stent and graft member as shown in FIG. 3.
The side of the tape member or ribbon that is FEP coated faces the
graft member to secure it to the graft member. The intermediate
stent-graft construction is heated to allow the materials of the
tape and graft member to merge and self-bind as will be described
in more detail below.
[0090] The FEP-coated porous expanded PTFE film used to form the
tape member preferably is made by a process which comprises the
steps of:
[0091] (a) contacting a porous PTFE film with another layer which
is preferably a film of FEP or alternatively of another
thermoplastic polymer;
[0092] (b) heating the composition obtained in step (a) to a
temperature above the melting point of the thermoplastic
polymer;
[0093] (c) stretching the heated composition of step (b) while
maintaining the temperature above the melting point of the
thermoplastic polymer; and
[0094] (d) cooling the product of step (c).
[0095] In addition to FEP, other thermoplastic polymers including
thermoplastic fluoropolymers may also be used to make this coated
film. The adhesive coating on the porous expanded PTFE film may be
either continuous (non-porous) or discontinuous (porous) depending
primarily on the amount and rate of stretching, the temperature
during stretching, and the thickness of the adhesive prior to
stretching.
[0096] In constructing this example, the thin wall expanded PTFE
graft was of about 0.1 mm (0.004 in) thickness and had a density of
about 0.5 g/cc. The microstructure of the porous expanded PTFE
contained fibrils of about 25 micron length. A 3 cm length of this
graft material was placed on a mandrel the same diameter as the
inner diameter of the graft. The nitinol stent member having about
a 3 cm length was then carefully fitted over the center of the thin
wall graft.
[0097] The stent member was then provided with a tape coupling
member comprised of the FEP coated film as described above. The
tape member was helically wrapped around the exterior surface of
the stent member as shown in FIG. 3. The tape member was oriented
so that its FEP-coated side faced inward and contacted the exterior
surface of the stent member. This tape surface was exposed to the
outward facing surface of the thin wall graft member exposed
through the openings in the stent member. The uniaxially-oriented
fibrils of the microstructure of the helically-wrapped ribbon were
helically-oriented about the exterior stent surface.
[0098] The mandrel assembly was placed into an oven set at
315.degree. C. for a period of 15 minutes after which the
film-wrapped mandrel was removed from the oven and allowed to cool.
Following cooling to approximately ambient temperature, the mandrel
was removed from the resultant stent-graft. The amount of heat
applied was adequate to melt the FEP-coating on the porous expanded
PTFE film and thereby cause the graft and coupling members to
adhere to each other. Thus, the graft member was adhesively bonded
to the inner surface of the helically-wrapped tape member through
the openings between the adjacent wires of the stent member. The
combined thickness of the luminal and exterior coverings (graft and
tape members) and the stent member was about 0.4 mm.
[0099] Although the invention has been described with reference to
the stent-graft examples illustrated in the drawings, it should be
understood that it can be used in conjunction with other devices,
stents or stent-grafts having constructions different than those
shown. For example, delivery systems described herein may be used
in conjunction with bifurcated stents or stent-grafts as will be
described in detail below. In addition, although a self-expanding
stent-graft has been described, balloon expanding stent-grafts also
may be used in conjunction with the delivery systems described
herein. These stent-grafts require a balloon to expand them into
their expanded state as opposed to the spring energy stored in a
collapsed self-expanding stent.
[0100] Referring to FIGS. 7A-C, one slip knot configuration that
may be used in conjunction with the thread-like coupling member
(104) will be described. The restraining member (102) is shown
without an implant positioned therein for purposes of
simplification. FIG. 7A illustrates the slip knot in a prerelease
or predeployment state. The series of knots are generally flush
with the restraining member (102) surface and add very little
profile to the construct which is preferred during implant
delivery. FIG. 7B shows the assembly of FIG. 7A with the
thread-like coupling member (104) loosened to illustrate how the
chain knots (130) may be formed. FIG. 7C diagrammatically
represents release of the assembly of FIG. 7A or 7B. The
illustrated stitch is releasable by pulling one end of the line
that results in releasing of the cylindrical or tubular restraining
member and then deployment of the device. This particular stitch is
called a chain stitch and may be created with a single needle and a
single line. A chain stitch is a series of loops or slip knots that
are looped through one another such that one slip knot prevents the
next slip knot from releasing. When the line is pulled to release a
slip knot, the following slip knot is then released and that
releases the next slip knot. This process continues during pulling
of the line until the entire line is pulled out of the restraining
member.
[0101] Referring to FIGS. 7A-C, as the unknotted portion or the
lead (132) of the thread-like coupling member (104) is pulled, such
as in the direction shown by reference arrow (134), each
consecutive chain knot (132) releases the next adjacent one. In the
preferred embodiment, the chain knots (130) of the coupling member
(104) are arranged to progressively release the collapsed implant
in a direction away from the distal portion of the delivery
catheter as shown in FIG. 10A and as will be discussed in detail
below.
[0102] Referring to FIGS. 8A through 8F, a method for making an
assembly comprising a restraining member with a collapsed or
compressed implant therein is shown for purposes of example. FIG.
8A shows the restraining member (102) with its side margins
releasably coupled to one another and its left end dilated by a
tapered mechanical dilator (402). A small funnel (404) is then
inserted into the restraining member (102) as shown in FIGS. 8B and
8C. The small funnel (404) and restraining member (102) are then
mounted onto a pulling frame (410), and a large funnel (406) is
fitted into the small funnel (404) as shown in FIG. 8D. Traction or
pull lines (408), which have been sutured to one end of the
stent-graft, (106) are pulled through the large funnel (406), small
funnel (404), and restraining member (102) with a tapered mandrel
(416). As shown in FIGS. 8F, the pull lines (408) are fastened to a
tie down post (412) located on a tension screw (414) and then are
pulled by the tension screw (414). The stent-graft (106) is then
pulled and collapsed sequentially through the large (406) and small
(404) funnels, and then into the restraining member (102). Once the
stent-graft (106) has been radially collapsed into the restraining
member (102), which has its side margins coupled together, the pull
lines (408) can be removed. The mandrel (416) may be inserted into
the restrained implant to facilitate introduction of another
component. In the preferred embodiment, a multilumen catheter (136)
(FIGS. 9-11) is introduced through the center of the compressed
stent-graft (106) and is used to deliver the radially restrained
stent-graft to the desired endolumenal site.
[0103] It also is noted that the funnels may be chilled to
facilitate compression of the stent when the stent is made of
nitinol. That is, when the stent is made of nitinol, the funnels
may be chilled below 0.degree. C. or below the transition
temperature (Mf) where nitinol is in its martensitic state. In
addition, the stent-graft could be folded first and then reduced in
profile by pulling through the funnel and into the restraining
member. Cooling may be accomplished by spray soaking the
stent-graft with chilled gas such as tetrafluroethane.
Micro-Dust.TM. dry circuit duster manufactured by MicroCare
Corporation (Conn) provides suitable results. The spray canister
preferably is held upside down to discharge the fluid as a liquid
onto the stent-graft.
[0104] A method of deploying an implant will be described with
reference to FIGS. 9-11. In general, an implant may be delivered
percutaneously with the delivery systems described herein,
typically through the vasculature, after having been assembled in
the reduced diameter form (see e.g. FIG. 1). At the desired
delivery site, the implant may be released from the restraining
member, thus allowing the implant to expand or be expanded against
the lumen wall at the delivery site. Although other devices
including stents or stent-grafts may be used, such as balloon
expandable stents, the following example will be made with
reference to a self-expanding stent-graft, which has the ability to
fully expand itself into its final predetermined geometry when
unconstrained. More particularly, the following example will be
made using a delivery system as shown in FIGS. 1 and 7A-C and a
stent-graft construction as shown in FIG. 3.
[0105] Referring to FIGS. 9A and 9B, an implant delivery assembly
including a collapsed stent-graft (106) that is confined within a
restraining member (102) and, which surrounds a distal portion of
the delivery catheter (136), is shown. The attending physician will
select a device having an appropriate size. Typically, the
stent-graft will be selected to have an expanded diameter of up to
about 20% greater than the diameter of the lumen at the desired
deployment site.
[0106] The delivery catheter preferably is a multilumen catheter.
The proximal portion of the catheter (136) is coupled to a hub
(140), which includes a guidewire port (142) for a guidewire (142),
and a deployment knob (144), which is coupled to the lead (132) of
the thread-like coupling member (104). Accordingly, when the knob
(144) is retracted, the restraining member (102) is released so
that the stent-graft may expand. The hub (140) also may include a
flushing port (146) as is conventional in the art. The stent-graft
(106) is held axially in place prior to deployment by a proximal
barrier (148) and distal barrier (150) which are positioned around
delivery catheter (136) adjacent to the proximal and distal
portions, respectively, of the restrained stent-graft. The proximal
and distal barriers (148, 150) may be fixedly secured to the
multilumen catheter (136) to restrict any axial movement of the
restrained stent-graft. The barriers preferably are positioned to
abut against the stent-graft or restraining member. The lead (132)
of the coupling member (104) is passed through an aperture (152) in
the proximal barrier (148) which is fluidly coupled to a lumen in
the delivery catheter (136) so that the coupling member lead (132)
can be coupled to the deployment knob (144). FIGS. 9A and 9B show
advancement of the catheter (136) and the restrained implant
through a vessel (154) toward a desired site. Referring to FIGS.
10A and 10B, once the restrained stent-graft reaches the desired
site (156), the deployment knob (144) is retracted so that the
stent-graft progressively expands as shown in the drawings as the
coupling member (104) is removed from the restraining member. The
coupling member preferably is arranged to facilitate stent-graft
expansion in a direction from the distal to proximal ends of the
stent-graft (i.e., in a direction from the catheter tip to the
catheter hub). FIGS. 11A and 11B show the stent-graft (106) and
restraining member (102) in their final implantation position after
the coupling member and catheter have been removed therefrom. In
another embodiment, multiple restraining members may be used as
shown in FIG. 9C. When the multiple coupling members (104) are
released simultaneously implant deployment time may be reduced.
[0107] A method for deploying a balloon expandable stent-graft may
be the same as that described above, with the exception that after
the coupling member (104) has been retracted from the eyelets
(116), the balloon, which may be positioned inside the stent-graft
prior to delivery, is inflated to expand the stent-graft (106) and
then deflated for removal through the catheter (136).
[0108] According to further embodiments of the invention,
multidirectional coupling member release or multiple coupling
members may be used. These configurations may facilitate more rapid
deployment of the implant than when a single unidirectional
coupling member is used. FIGS. 12A-12D diagrammatically show
multidirectional deployment of a restrained implant according to
the principles of the invention where a coupling member arrangement
is provided to release the implant from its middle portion,
preferably its axial center, outward toward the implant ends.
Although a particular coupling member configuration is not shown in
these diagrammatic representations, one suitable coupling
configuration is shown in FIG. 13 where the leads (132) may be
passed through the aperture (152) and coupled to the deployment
knob (144) as shown in FIG. 9A and described above.
[0109] Referring to FIG. 12A, the restrained stent-graft, which is
positioned on the distal end portion of delivery catheter (136), is
advanced through a vessel (154) for deployment in an aneurysm
(158). The axial midpoint of the restraining member (102)
preferably is positioned at the center of the aneurysmal sac. As
the coupling member arrangement unlacing propagates from middle of
the construct toward the proximal and distal ends of the
restraining member (102) and the stent-graft (106), the stent-graft
(106) progressively expands from its axial midportion toward its
ends as shown in FIGS. 12B and 12C. This may be accomplished by
pulling the leads (132) shown in FIG. 13 simultaneously when the
arrangement in that figure is used. The stent-graft size is
selected so that when the restraining member is fully released and
the stent-graft fully deployed as shown in FIG. 12D, the proximal
and distal portions of the stent-graft are positioned against the
proximal and distal necks of the aneurysm. The delivery catheter
may then be retracted.
[0110] As is apparent from the drawings, this embodiment
advantageously allows fluid flow through the aneurysmal sac to
remain substantially unobstructed during the release of the
restraining member. For example, the stent-graft ends are still
constrained at the deployment time shown in FIG. 12C where the
aneurysm neck regions are shown minimally obstructed. In addition,
this simultaneous, multidirectional release of the restraining
member advantageously reduces the time in which fluid flow in the
vessel may disturb the implant position as it is deployed as
compared to a single directional release mechanism such as that
shown in FIGS. 9-11.
[0111] Referring to FIG. 13, a multiple coupling member
configuration is shown. The illustrated arrangement includes two
lacing configurations (150) and (152). Except for the placement of
the lead (132) of thread-like coupling member (104), configuration
(152) is the mirror image of configuration (150). Accordingly,
description of only one of the configurations will be made for
purposes of simplification. Referring to the lacing configuration
(152), configuration (152) is the same as that shown in FIGS. 7A-C
with the exception that configuration (152) further includes two
additional slip knots, generally designated with reference numeral
(504), and tuck or loop arrangement (506). The additional slip
knots are not interwoven in the restraining member and provide a
delay mechanism for release of the coupling member, as is apparent
from the drawings, when the lead (132) is pulled in the direction
of the arrow (134). Thus, inadvertent pulling of the lead (132)
will not immediately begin to release the coupling member from the
restraining member. The tuck arrangement simply involves tucking
the slack from lead (132) under stitches at various intervals as
shown so that the additional slip knots (504) may be pulled out of
the way for delivery. In addition, the tuck or loop arrangement
(506) provides an additional delay mechanism for release of the
slip knots.
[0112] As discussed, the delivery systems described above can be
used with other implants or devices. These systems, for example,
can be used in conjunction with the bifurcated devices described
below.
[0113] The modular stent-graft of FIGS. 14A through 14D generally
has two principal components; a main body (700) and a contralateral
leg (730) each generally having a graft member attached to a stent
member according to the description above. The main body (700)
generally has a number of sections which have distinct overall
constructions. A distal trunk section (708) has a single lumen
structure beginning at a distal end (702) of the main body (700)
and continuing until a bifurcation point (728). The bifurcation
point (728) is the location within the prosthesis where the single
lumen of the distal trunk section (708) bifurcates into internal
two flow lumen.
[0114] An intermediate section (710) begins at the bifurcation
point (728) and continues to the receiving hole (704). In the
intermediate section (710), the stent-graft has an internal graft
structure which is bifurcated into two lumen surrounded by a
generally tubular, single-lumen stent structure. Finally, a
proximal section (712) is a single lumen structure for both the
stent member and the graft member and includes an ipsalateral leg
(726) which terminates at an ipsalateral leg hole (706).
[0115] The graft member of the intermediate section (710)
bifurcates the single lumen distal trunk section (708) into the
ipsalateral leg (726) and am internal female receiving lumen (703).
The receiving lumen (703) terminates at a receiving hole (704). The
receiving hole (704) and receiving lumen (703) accommodate delivery
and attachment of the contralateral leg component (730).
Preferably, the graft material at the distal end (734) of the
contralateral leg component (730) is scalloped as shown more
clearly in FIG. 23 discussed below.
[0116] The receiving hole (704) is supported by a wire structure
around a substantial portion of its periphery so that the receiving
hole (704) is held open after deployment. In a preferred embodiment
the wire structure that supports the receiving hole (704) is an
independent wire ring (714).
[0117] The independent wire ring (714) is located in the general
area of the receiving hole (704) in the intermediate section (710).
The independent wire ring (714) ensures that the graft material at
the receiving hole (704) is supported in an open position to
receive the distal end (734) of the contralateral leg (730). In
absence of such support, the receiving hole (704) may not reliably
open after delivery of the main body component (700) because within
the intermediate section (710) the bifurcated graft member in the
area of the receiving lumen (703) does not have full stent support
on its interior periphery. This may be better seen in FIG. 18 which
shows the absence of any internal stent support of the interior
graft periphery (785) in the area of the receiving lumen (703).
[0118] The independent wire ring (714) may be comprised of the same
materials as the other stent-graft sections discussed above and is
preferably self-expanding. In a preferred embodiment, the
independent wire ring comprises a single turn of an undulating wire
stent material surrounded by at least one layer of tape which is
heat bonded to the receiving hole (704). Alternatively, the
independent wire ring (714) could be formed as the last turn of the
main body (700).
[0119] A radiopaque marker may be used to make the receiving hole
(704) visible during implantation. Such a marker may include a
radiopaque wire adjacent to the independent wire ring (714). Such
markers make it easier to see the location of the receiving hole
(704) after deployment of the main body (700) within the mammalian
body.
[0120] This construction of the intermediate stent section (710) as
seen in cross-section in FIG. 14C is characterized by a
single-lumen stent member and bifurcated graft member and offers
both a smaller compressed profile as well as simplified
manufacturing over constructions which have discreet stented leg
features. The compressed profile is determined largely by the
physical amount of stent and graft material present in a given
section. This construction eliminates the stent material that would
normally support the inside periphery of the bifurcated graft
section resulting in less stent material to compress in that
region. As the main body component (700) is compressed for delivery
as discussed above, the compressed profile is significantly smaller
than would be a structure that had a section of bifurcated stent
over the section of bifurcated graft.
[0121] Even though bifurcated flow is supported, manufacturing is
simplified because there is no bifurcated stent section. Winding a
bifurcated stent section in one piece, for example, is a more
complex process. Likewise, winding separate cylindrical stent
structures and connecting them to form a bifurcated stent structure
is complicated and ultimately may be less reliable. The
intermediate section (710) allows the entire stent member that
covers the main body component (700) to be made from a single
undulating wire arranged in multiple helical turns. The result is a
bifurcated stent-graft device which is simple to manufacture,
easily compressible and which expands reliably upon deployment.
[0122] An alternate construction of the intermediate stent section
(710), is shown in FIG. 14D. The intermediate stent section (710')
has a shape characterized by the indented regions (727). The shape
could generally be described as a `figure-8`, except that the area
between the bifurcated graft member remains unsupported at its
centermost region. This construction is still a single lumen stent
construction and therefore maintains much of the benefits of
reduced profile and simplified manufacturability while providing
the bifurcated graft member with increased support around a greater
portion of its perimeter. Further, indented portions (727) have
less of a tendency to spring outward upon application of external
forces.
[0123] As mentioned above, the main body component (700) and the
contralateral leg component (730) are adapted for delivery in a
compressed state to a bifurcation site within a body. For this
purpose the main body component (700) is preferably equipped with a
restraining member (722) constructed as described above. Likewise,
the contralateral leg component (730) has an attached restraining
member (732). These restraining members are typically sutured to
the graft material at intervals down their length.
[0124] FIG. 15 shows an assembled bifurcated stent-graft (740)
after deployment at a bifurcation site within a bifurcated body
vessel afflicted with an aneurysm (758). The prosthesis may be
positioned at the location where the abdominal aortic artery (752)
bifurcates into the left iliac artery (756) and the right iliac
artery (754) as shown. So that the various features of the implant
are more clearly shown, the restraining member is not shown in FIG.
15.
[0125] The assembled bifurcated stent-graft (740) is comprised of
the main body component (700) and the contralateral leg component
(730). The distal end (734) of the contralateral leg component
(730) has been inserted into the receiving leg hole (704) and the
female receiving lumen (703) of the main body component (700).
[0126] For best results in deploying any stent or stent-graft of
these types it is essential that they have the appropriate
structural properties such as axial stiffness, flexibility and
kink-resistance. With complicated structures, such as those
required for treating a bifurcated site, it is increasingly
difficult to obtain the desired structural properties because
optimizing one may negatively effect the other.
[0127] For instance, optimizing the global axial stiffness of a
stent or stent-graft will necessarily make the device significantly
less flexible and consequently impair its resistance to kinking and
lessen its ability to conform to the natural bends of curves the
body's vasculature. Conversely a device that has high flexibility
with little axial stiffness is difficult to properly deploy and
does not aid in anchoring the device in the desired location.
[0128] With these constraints in mind, it has been discovered that
having a bifurcated stent-graft which has segments constructed with
varying structural properties offers improved deployability, is
less susceptible to kinking, and favorably tends to maintain its
desired position after deployment while allowing sufficient
flexibility to accommodate movement by the body. The exact
structural properties desired may depend on the location where the
prosthesis is to be deployed.
[0129] For these reasons, it is preferable that the bifurcated
stent or stent-graft be constructed with at least two segments
having structural properties different from one another. For
example, in FIG. 14A, a length of the distal section (708) and the
intermediate section (710) may be constructed with a higher axial
stiffness for improved deployment and positional stability while
the proximal section (712) may be constructed to have higher
flexibility to accommodate the geometry of the iliac artery.
[0130] It may be further desirable to have a number of segments
that have different structural properties. Accordingly, the main
body component (700) and the contralateral leg component (730) of
the assembled stent-graft (740) have segments constructed with
structural properties different from adjacent segments. In one
preferred embodiment shown in FIG. 15, the main body component
(700) has four different segments constructed with different
structural properties. The distal segment (742) is constructed to
have higher axial stiffness than the more flexible proximally
adjacent segment (744). The proximal section (748) is constructed
to have a higher flexibility than that of its distally adjacent
segment (746). Likewise the contralateral leg component (730) has
an axially stiffer distal segment (750) and a more flexible
proximal segment (749).
[0131] There are a number of ways to alter the structural
properties of stent or stent-graft components. One way of
selectively altering the structural properties of a stent-graft
segment is to use a tape member for that segment that has different
physical dimensions. Such a tape member is discussed above with
reference to the tape member (128) of FIG. 1. For example the tape
member width, thickness or spacing may be increased, from the
preferred dimensions discussed above, in a segment where it is
desirable to have increased or decreased stiffness. For example,
the use of wider tape wound with closer spacing will increase the
stiffness in that area.
[0132] Another way of selectively altering the structural
properties of a stent or stent-graft segment is shown in FIGS. 14A
and 15. Extended struts (718) and (719) may be used to increase the
axial stiffness of a stent-graft segment. Extended struts are
formed by extending an apex on one turn of the undulating wire
until it contacts an apex on an adjacent turn. This contact between
an extended strut and the apex of an adjacent stent turn provides
an added amount of axial stiffness. In a preferred embodiment, a
layer of tape (not shown) is applied around the device in a helical
pattern that covers each of the apexes of the extended struts. This
additional layer of taping keeps the strut pairs together.
[0133] Referring to FIG. 14A, a first helical stent turn (720) and
a second helical stent turn (721) have a generally undulating shape
having apexes. An extended strut (718) of the stent turn (720) is
formed having its apex near or in contact with the apex of the
stent turn (721) directly below. The extended strut (719) is
similarly formed by extending an apex of the stent turn (721)
directly down to contact the apex in the turn below. This pattern
in continued, each time spacing the extended strut over one
undulation. This results in a helical pattern of extended struts
down the length of the device. Of course, the extended struts may
be arranged in patterns other than the helical configuration
described.
[0134] A number of these patterns may be employed in any one
segment or the extended strut pattern may be used in other segments
to increase axial stiffness. Preferably the distally adjacent
segment (746) on the main body component (700) and the axially
stiff distal segment (750) on the contralateral leg component are
constructed with extended struts as shown.
[0135] Referring to FIG. 15, the distal end (702) may be sized to
properly fit the inside diameter of the target artery, in this case
the abdominal aortic artery. Typically the prosthesis is designed
to have an unconstrained diameter slightly larger than the inside
of the target vessel.
[0136] The ipsalateral and contralateral legs of the assembled
bifurcated stent-graft (740) are typically the same size at their
distal ends regardless of the size of the distal end (702) and
undergo tapered sections (724) and (738) that taper to a diameter
which corresponds approximately to the internal diameter of the
iliac arteries. These tapered sections (724) and (738) are
preferable to abrupt changes in diameter as they tend to produce
superior flow dynamics.
[0137] After deployment, the assembled bifurcated stent-graft (740)
must establish sufficient contact with the healthy vessel lumen an
each side of the aneurysm (758) so that the device does not migrate
or dislodge when subjected to the relatively high fluid pressures
and flow rates encountered in such a major artery, especially when
the body again becomes mobile after recovery. Further, sufficient
contact must be made so that there is no leakage at the distal end
(702), the ipsalateral leg hole (706) or the proximal end (736) of
the contralateral leg.
[0138] Anchoring or staying features that allow the stent or
stent-graft exterior to anchor itself to the vessel lumen wall may
be provided to help the device seal to the vessel wall and maintain
its deployed position. For example, anchors (716) as seen in FIGS.
14A and 15 are provided on the main body component (700) and could
also be provided on the contralateral leg component (730).
Preferably the top stent portion (717) is directed angularly
outward. This flared stent portion works to force the anchors (716)
into the vessel wall as the top stent portion (717) expands under
force into radial interference with the vessel wall upon
deployment.
[0139] A preferred construction for an anchor (716) is shown in
FIG. 17. This construction involves extending two wires from the
upper stent turn (762) under an apex of an adjacent lower stent
turn (764). The two ends of stent wires (760 and 761) are then bent
out and away from the graft material (768). Extended struts (771)
are formed adjacent to each anchor in the manner described above
except the extended struts extend under the adjacent lower stent
turn (764) down to a third stent turn (765). This extended strut
arrangement provides support for the anchors (716) and provides for
low stresses in the wires (760 and 761) under the application of
bending forces encountered as the prosthesis expands into the
vessel wall. The extended struts (771) minimize the localized
deformation of the stent-graft structure in the area of the anchors
by providing broader support.
[0140] Another construction of the anchors (716') are shown in FIG.
16. An anchor (716') is formed in the same manner except the ends
of the anchor remain connected in a `U-shape` configuration as
shown. An anchor (716') may be formed at any location on the
stent-graft. Most preferably, the anchors are formed in an evenly
spaced pattern around the top stent portion (717) (FIG. 14A).
[0141] It should be apparent that the anchors as described above
are not limited in use to the stent-graft combination shown in the
figures but indeed could be used in any non-bifurcated or stent
only construction that require similar functionality.
[0142] Sealing at the vessel wall may also be enhanced by the
alternate construction shown in FIG. 17 by way of a sealing
mechanism. A sealing mechanism can be used with any type of
implant, including any of the implants discussed above. For
purposes of illustration, the sealing mechanism is shown with
reference to the bifurcated implant of FIG. 14 and comprises seal
member (772) as seen in detail in FIGS. 16 and 17. The sealing
mechanism described below can be used with any of the implants
discussed above.
[0143] One preferred construction for seal member (772) in the
variations shown in FIGS. 16 and 17 may be similar to the preferred
construction for the tape member used in constructing the
stent-graft tubular member, as is provided in reference to FIG. 1A
and FIG. 3 above.
[0144] In general, a thin walled ePTFE tape is used for seal member
(722) similarly as that for tape member (128), shown variously in
the previous figures. The tape used for seal member (722) is
adhered to the outer surface of the stent-graft, including over
tape member (128), described previously for bonding the stent and
graft members. Seal member (722) has an inner surface constructed
of a similar material for either the outer surface of the tape
member (128) or the outer surface of the graft-member (124),
depending upon which surface the seal member is desirably
adhered.
[0145] First cuff end (767) is bonded to the stent-graft outer
surface and second cuff end (769) is not, in order to form the
unadhered flange to function as a one-way valve against
peri-stent-graft flow. Seal member (722) may be selectively adhered
along its length in this manner by providing a variable inner
surface to the seal member such that, upon heating, only the
surface in the region of first cuff end (767) bonds to the outer
surface of the stent-graft. For example, the inner surface of seal
member (722) may have an FEP liner in the region of first cuff end
(767) but not in the region of second cuff end (769). In this case,
upon contacting an outer surface of the stent-graft that has a
uniform FEP outer surface, only first cuff end (767) may be heat
secured thereon.
[0146] Alternatively, seal member (722) may have a uniform inner
surface, such as constructed of FEP, and a variable outer surface,
such as with a selective portion of FEP, may be provided either on
the tape member (128) or on the graft member (124) in the region
where the heat bonding of seal member (722) is desired. Still
further, seal member (722) may have a uniform surface and may be
positioned over tape member (128) and graft member (124) so that
variability between the outer surfaces of tape member (128) and
graft member (124) causes a selective bonding with the first cuff
end (767) over one of those surfaces.
[0147] Further to the construction of seal member (722), the
particular wall thickness of the tape which may be used for this
component should desirably be as thin as possible to functionally
provide the flange-one-way-valve function for that member. This is
because, since seal member (722) is over the outer surface of the
other stent and graft components of the stent-graft, seal member
(722) is believed to be the profile-limiting feature of the overall
assembly. Therefore, in a particular design, seal member (722) may
desirably be a thinner wall than for the tape member used to
construct the stent-graft described in reference to FIGS. 1 and
3.
[0148] Further referring to the particular constructions and
related methods just described for adhering seal member (722) to
the outer surface of the underlying stent-graft, it should be
apparent to one of ordinary skill in the art that the desired
construction and heat securing technique for seal member (722) is
premised upon the theory that, where one polymer meets a like
polymer (such as FEP meeting FEP), heating under proper conditions
will allow for a selected heat bond. Any suitable means may be used
for securing a seal member to the outer surface of a given tubular
member, as would be apparent to one of ordinary skill.
[0149] Further there is a plurality of circumferential strut spaces
between the struts of the stent member. It is believed that these
spaces may provide a path for leakage flow around the outer surface
of the graft member and along the outside of the stent-graft.
Second cuff end (769), however, captures such leakage flow beneath
its flange, which can not propagate along the outer surface of the
stent-graft because first cuff end (767) is secured to the outer
surface of that stent-graft. In other words, flow over the
stent-graft and into an aneurysm is occluded.
[0150] Furthermore, when apex strut (716) is anchored into the wall
of abdominal aortic artery as shown in FIG. 15, it has been
observed that the portion of main body component (700) at and
adjacent to the apex strut (716) may be forced away from the artery
wall. This action causes a separation between the outer surface of
main body (700) and the artery wall, which separation is believed
to create a leakage flow path. The flange of seal member (772)
captures that flow and occludes it from propagating into the
aneurysm (758).
[0151] In addition to maintaining a good contact with the vessel
lumen walls, the components of the stent-graft must make sufficient
contact with each other such that the separate modules stay
attached and do not leak at their engagement interface. The
stent-graft shown in FIG. 18 illustrates several important features
designed to effectuate a leak-free and positionally stable seal at
the interface between the receiving lumen (703) of the main body
component (700) and contralateral leg component (730).
[0152] FIG. 18 shows a partial cross-section of the assembled
stent-graft. The contralateral leg component (730) has been
inserted into the receiving lumen (703) of the main body component
(700). This cross-sectional view shows clearly that the main body
component (700) includes a main body graft member (780) and a main
body stent member (782). The contralateral leg component (730)
includes a contralateral graft member (784) and a contralateral
stent member (786).
[0153] At the interface between the contralateral leg component
(730) and the receiving lumen (703), the assembly provides for an
extending sealing region (790). Preferably the extended sealing
region (790) consists of a generally cylindrical interfering
friction fit between the outside diameter of the contralateral leg
component (730) and the inside diameter of the receiving lumen
(703). That is, the natural or resting outside diameter of the self
expanding contralateral leg component (730) would be larger than
the natural inside diameter of the receiving lumen (703). Thus the
forces created by the interference act to seal the two components
and also serve to resist movement of the two components.
[0154] The type of generally cylindrical extended sealing region
just described has many advantages. First, it allows for the stent
and graft structures in the extended sealing region (790) to be
constructed of relatively simple generally cylindrical elements
that are easily manufactured. Because the extended sealing region
(790) extends over a large length it necessarily has a large
surface area to effectuate sealing between the components. This
larger sealing area typically provides that multiple turns of the
stent structures will be engaged in an interfering and thus sealing
relationship.
[0155] In one preferred embodiment, the extended sealing region has
a length in excess of one-half of the diameter of the receiving
lumen (703), more preferably the length is greater that the
diameter of the receiving lumen (703), and most preferably the
length is more than 2 times the diameter of the receiving lumen
(703).
[0156] Because the manufacturing tolerances of the simplified
shapes are easily controlled and because the engagement of the
extended sealing region (790) is quite large, a highly reliable
joint is formed between the modular components. Even so it may be
desirable to create one or more localized zones of increased
interference to increase the sealing capability and positional
stability.
[0157] Localized zones of interference may be created in a number
of ways. In a preferred embodiment, an annular ring of decreased
diameter is formed within the receiving lumen. Such a localized
decreased diameter causes a greater interference with the outside
diameter of the contralateral leg component in a localized area
while the remainder of the engagement with the receiving lumen is
subject to the general interference friction fit described
above.
[0158] One way of creating a localized decreased diameter is
illustrated in FIG. 20 which shows a partial cross-section of the
extended sealing region (790). A zone of reduced diameter (799) is
created by placing an anchoring ring (798) between the graft member
(780) and the stent member (782) of the receiving lumen (703). The
anchoring ring may be made from any polymeric or wire material,
preferably a material that will not inhibit the receiving lumen
from self-expanding to an open position. Most preferably the
material is a suture material, typically ePTFE.
[0159] Alternately, localized zones of decreased diameter may be
created as shown in FIGS. 21 and 22 by folding a portion of the
graft member (780) back up into the receiving lumen (703). In FIG.
21, the zone of reduced diameter (806) is formed by creating a
folded flap (808) of the graft material (780) around an anchoring
ring (802). The flap is heat bonded in place roughly at a location
(804) as shown. In FIG. 22, the zone of reduced diameter (809) is
formed of flap (808) and heat bonded roughly at a location (807) in
a similar manner but without any anchoring ring. The localized
interference using these methods tends to cover a larger area and
the flap (808) provides a more flexible member to seal against the
outside diameter of the contralateral leg component (730).
[0160] One further aspect of ensuring a good seal between the
stent-graft components involves the use of a scalloped stent-graft
construction at the distal end of the contralateral leg component
(810). To create this scalloped construction, the graft material
between the apexes of the stent member is removed on the last turn
of the stent. For example scallop (812) may be formed by removing
(or cutting and folding under) the graft material from between a
first apex (814) and an adjacent apex (816).
[0161] The advantage of using a scalloped arrangement are
illustrated in FIGS. 24A through 25B. FIG. 24A shows a
cross-section of the fully expanded contralateral leg component
(730) having an unscalloped construction. A first apex (822) and an
adjacent apex (824) have continuous graft material (784) in the
area between them. When the apex (822) and the adjacent apex (824)
are forced together in the directions of the arrows (820), the
graft material (784) forms a buckle or wrinkle (818) which is a
potential leak path or is a potential site for thrombogenic
material to build up as seen in FIG. 24B. The scalloped
construction shown in FIGS. 25A and 25B, on the other hand, have no
graft material between the first apex (814) and the adjacent apex
(816) and therefore when forced together do not form a graft
material wrinkle.
[0162] The wrinkle (818), mentioned above may also be formed when
the stent-graft is not allowed to expand to its complete diameter.
For instance it is quite common that the receiving lumen or vessel
wall internal diameter is smaller than the fully expanded
stent-graft outer diameter. This being the case, it should be clear
that the scalloped construction may alternately be used at any of
the terminal openings of the main body component or the
contralateral leg component. Preferably, the distal end (702) of
the main body component (700) also has this scalloped construction
as shown in FIGS. 14A and !4B.
[0163] In the previous discussion we have referred generally to a
stent-graft that includes a graft member. While the construction of
such straight stent grafts are discussed at length above, the
construction of a bifurcated graft member is illustrated in FIGS.
26, 27A and 27B. A bifurcated graft member suitable for
construction of the main body component (700) discussed above is
generally formed of two graft members: the ipsalateral tapered
graft (840) and the contralateral tapered graft (842). The separate
contralateral leg graft component (844) is a straight or tapered
section and may be formed according to the principles discussed in
the first section above.
[0164] The ipsalateral tapered graft (840) has three sections which
are separated by tapers. A top section (846), a middle section
(848), and a bottom section (850). The body component graft (854)
is formed by heat bonding the top section (846) of ipsalateral
tapered graft (840) to the top section (847) of contralateral
tapered graft (842). This heat bonding forms a common septum (856)
which in a preferred embodiment is subsequently cut away to produce
a smooth bifurcation (858). Cutting away the septum material
prevents fluid flow disturbance or blockage that could result from
deviation of the septum. Such deviation is caused by the fluid
pressure and is aggravated if the stent-graft is radially
compressed in a manner which causes the septum to become loose or
no longer taut.
[0165] In another embodiment, a graft section may be constructed in
the manner illustrated in FIGS. 27A and 27B. According to this
embodiment, the body component graft (867) is constructed from two
pieces. A tubular graft section (860) is bent into a `U-shape`. A
top hole (864) is formed by notching the top of the `U-shape`.
Upper graft section (862) is placed over the top hole (864) of
tubular graft section (860). The two pieces are bonded together at
the bonding interface (866). Preferably, the two graft pieces are
heat bonded while supported by interior mandrels (not shown) to
obtain the desired shape and smooth interior. However, upper graft
section (862) may be attached to the tubular graft section (860) at
the bond interface (866) in any manner that provides a sufficiently
leak free seal. For example the components may be sutured together
or adhesive bonded.
[0166] In use, the modular bifurcated stent-graft is typically
delivered percutaneously through the vasculature of the body.
Preferably the prosthesis is delivered by way of a restraining
member as described in detail above. FIGS. 28A though 28E
diagrammatically illustrate deployment of a bifurcated stent-graft
with a restraining member (902) using a percutaneous catheter
assembly. Referring to FIG. 28A, a multilumen catheter assembly
(928) has been inserted to a selected site within a body lumen. The
main body component (700) of a bifurcated stent-graft is held in a
compressed state about a guidewire (926) and a guidewire lumen
(929) by a restraining member (902) and a coupling member (906).
The collapsed main body component (700) is held axially in place
prior to deployment by a distal barrier (930) and a proximal
barrier (932). The distal (930) and proximal (932) barriers are
typically affixed to the guidewire lumen (929). The coupling member
(906) extends through the eyelets (920) of the restraining member
(902) forming chain knots and into the multilumen catheter
(928).
[0167] FIG. 28A shows advancement of the multilumen catheter (928)
with the distally located main body component (700) and the
restraining member (902) into implantation position, typically at
the bifurcation of a major vessel. During deployment it is critical
that the surgeon align the main body component (700) so that the
ipsalateral leg (726) will extend down one branch of the bifurcated
vessel, and so the receiving hole (704) and the receiving lumen
(703) will be lined up with the other branch of the bifurcated
vessel so as to receive the contralateral leg component (730).
[0168] One way of facilitating this alignment is to provide
radiopaque markers so that the surgeon may readily determine the
rotational position of the main body component (700) prior to
deployment or release from the restraining member (902). In a
preferred embodiment, a long marker (934) is located on the
contralateral side of the compressed assembly and a shorter marker
(936) is placed on the ipsalateral side. Preferably these markers
are placed on the stent prior to compression but may alternatively
be part of the restraining member. Having one marker of a different
length allows the surgeon to identify the orientation of both the
ipsalateral leg and the receiving lumen relative to the bifurcated
vessel.
[0169] Once the assembly is properly aligned and positioned for
implantation, the coupling member (906) is pulled and the
restraining member (902) begins to release the implant, typically
at the distal end first. In the preferred embodiment, the
restraining member (902) is located down the side as shown because
it is less likely to interfere with deployment of the receiving
lumen (703).
[0170] FIG. 28B shows the main body component (700) radially
expanding as the coupling member (906) is retracted through the
eyelets (920) of the restraining member (902) and into the catheter
assembly (928). In the preferred embodiment, the restraining member
(902) has been fixedly attached to the main body component (700)
with a number of sutures along the length of the main body
component to prevent any relative longitudinal movement between the
implanted prosthesis and the restraining member (902). The
restraining member may optionally employ a retracting or pull-down
mechanism as described at length above.
[0171] FIG. 28C shows the main body component (700) and the
restraining member (902) in final implantation position at the
vessel bifurcation after the guidewire (926) and the catheter
assembly (928) have been retracted.
[0172] FIG. 28D shows the contralateral leg component (730) being
delivered to the contralateral receiving hole using a restraining
member (942). The procedure for positioning and releasing the
contralateral leg component (730) is the same as that described
above for implantation of a generally cylindrical stent-graft
except that certain radiopaque markers may be employed to ensure
its proper position relative to the bifurcation point (728) of main
body component (700).
[0173] Radiopaque markers may be located, for example, to indicate
the position of the receiving hole (704), the distal end (734) of
the contralateral leg component (730), and the bifurcation point
(728) of the main body component (700). These markers serve to
indicate the position of the contralateral leg component as it
enters the receiving hole (704) and its ultimate position relative
to the receiving lumen (703) which begins at bifurcation point
(728). In a preferred embodiment illustrated in FIG. 19, the
radiopaque wires (794) may be heat bonded or imbedded into the
graft material (780) around the periphery of the receiving lumen.
Such radioopaque wires could be used in other places such as the
contralateral leg component lumen, the ipsalateral leg lumen or the
lumen at the distal end of the main body component (700).
[0174] FIG. 28E shows the assembled bifurcated stent-graft in its
final implantation state with the contralateral leg component
expanded into and engaged with the receiving lumen of the main body
component (700).
[0175] FIGS. 29A through 29D diagrammatically show the same stent
or stent-graft components being deployed except that the
restraining member (902) is released from the center out towards as
the coupling member (906) is retracted. This may provide more
accurate placement relative to the bifurcation point of the vessel
instead of relative to the distal end as with end release.
[0176] While this invention has been described with reference to
illustrative embodiments, this description is not intended to be
construed in a limiting sense. Various modifications and
combinations of the illustrative embodiments, as well as other
embodiments of the invention will be apparent to persons skilled in
the art upon reference to the description. It is therefore intended
that the appended claims encompass any such modifications or
embodiments.
[0177] The disclosures of the publications and patents that are
cited in this application are hereby incorporated by reference.
* * * * *