U.S. patent application number 10/731737 was filed with the patent office on 2004-08-05 for expandable coil endoluminal prosthesis.
This patent application is currently assigned to VASCULAR ARCHITECTS, INC., A Delaware corporation. Invention is credited to Fogarty, Thomas J., Hill, Bradley B., Kamdar, Kirti P., Klumb, Katherine J..
Application Number | 20040153142 10/731737 |
Document ID | / |
Family ID | 22981025 |
Filed Date | 2004-08-05 |
United States Patent
Application |
20040153142 |
Kind Code |
A1 |
Klumb, Katherine J. ; et
al. |
August 5, 2004 |
Expandable coil endoluminal prosthesis
Abstract
A coiled stent (196) has a coiled stent body with a main body
portion (106) and end portions (108). The end portions may be
substantially less stiff than the body portion to help prevent
tissue trauma. A graft material (124) may be used to cover at least
the main body portion to create a coiled stent graft (122) in which
adjacent turns (128) have gaps defined therebetween to create a
generally helical gap (130). The coiled stent may have side
elements (10) separated by connector elements (112) and be
placeable in a contracted, reduced diameter state and in a relaxed,
expanded diameter state. The connector elements are preferably
generally parallel to the stent axis when placed in the contracted,
reduced-diameter state, typically tightly wrapped around a
placement catheter (136).
Inventors: |
Klumb, Katherine J.; (Los
Altos, CA) ; Fogarty, Thomas J.; (Portola Valley,
CA) ; Kamdar, Kirti P.; (Sunnyvale, CA) ;
Hill, Bradley B.; (Portola Valley, CA) |
Correspondence
Address: |
HAYNES BEFFEL & WOLFELD LLP
P O BOX 366
HALF MOON BAY
CA
94019
US
|
Assignee: |
VASCULAR ARCHITECTS, INC., A
Delaware corporation
San Jose
CA
|
Family ID: |
22981025 |
Appl. No.: |
10/731737 |
Filed: |
December 9, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10731737 |
Dec 9, 2003 |
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09834145 |
Apr 12, 2001 |
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6660032 |
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09834145 |
Apr 12, 2001 |
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09400955 |
Sep 22, 1999 |
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6645237 |
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09400955 |
Sep 22, 1999 |
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09258542 |
Feb 26, 1999 |
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6248122 |
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Current U.S.
Class: |
623/1.22 |
Current CPC
Class: |
A61F 2/9517 20200501;
A61F 2/88 20130101; A61F 2002/075 20130101; A61F 2220/0058
20130101; A61F 2/954 20130101; A61F 2250/0039 20130101; A61F
2002/067 20130101; A61F 2/07 20130101; A61F 2002/065 20130101; A61F
2220/0075 20130101; A61F 2/958 20130101; A61F 2002/9511 20130101;
A61F 2220/005 20130101; A61F 2250/0018 20130101 |
Class at
Publication: |
623/001.22 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. A coiled endoluminal prosthesis comprising: a body comprising a
coiled ribbon of material; the body comprising a main body portion
and first and second end portions, the main body portion comprising
first and second edge elements separated by connector elements, at
least substantially all of the elements between the first and
second edge elements being said connector elements; the main body
portion having a maximum width and the end portions having a
maximum width no greater than the maximum width of the main body
portion; said body movable between a reduced diameter state,
extending along a body axis, and an expanded diameter state; and
all said connector elements being at an acute angle to the edge
elements when in the expanded diameter state, said angle chosen so
that all of said connector elements lie generally parallel to the
body axis when in the reduced diameter state so to provide a
smoother appearance when in the reduced diameter state.
2. A coiled endoluminal prosthesis according to claim 1 wherein the
end portions are substantially less stiff than the main body
portion.
3. A coiled endoluminal prosthesis according to claim 1 wherein
said end portions each have an inwardly-tapering portion with a
blunt tip.
4. A coiled endoluminal prosthesis according to claim 1 wherein the
main body portion comprises first, second and third longitudinal
sections each having a different radial stiffness.
5. A coiled endoluminal prosthesis according to claim 1 wherein the
stiffness of the main body portion continuously varies along at
least part of its length.
6. The coiled endoluminal prosthesis according to claim 1 further
comprising an orientation-specific marker carried by the body so to
aid proper rotary orientation and longitudinal placement of the
prosthesis.
7. The coiled endoluminal prosthesis according to claim 1 wherein
the end portions comprise generally U-shaped members, said
generally U-shaped members being thinner and more flexible than the
edge and connector elements of the main body portion.
8. The coiled endoluminal prosthesis according to claim 1 wherein
the end portions have a longitudinally-extending length and a
laterally-extending width, said length being greater than said
width.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a continuation of U.S. patent application Ser. No.
09/834,145 filed 12 Apr. 2001, now U.S. Pat. No. 6,660,032, which
is a continuation of U.S. patent application Ser. No. 09/400,955
filed 22 Sep. 1999, now U.S. Pat. No. 6,645,237, which is a
continuation-in-part of U.S. patent application Ser. No. 09/258,542
filed 26 Feb. 1999, now U.S. Pat. No. 6,248,122. This is related to
U.S. patent application Ser. No. 09/400,952 entitled Catheter With
Controlled Release Endoluminal Prosthesis and Method For Placing,
filed 22 Sep. 1999, now U.S. Pat. No. 6,238,430.
BACKGROUND OF THE INVENTION
[0002] The present invention provides devices and methods for the
endoluminal placement of prostheses, particularly within the
vascular system for the treatment of cardiovascular disease, such
as vascular stenoses, dissections, aneurysms, and the like. The
apparatus and methods, however, are also useful for placement in
other body lumens, such as the ureter, urethra, biliary tract,
gastrointestinal tract and the like, for the treatment of other
conditions which may benefit from the introduction of a reinforcing
or protective structure within the body lumen. The prostheses will
be placed endoluminally. As used herein, "endoluminally" will mean
placement by percutaneous or cutdown procedures, wherein the
prosthesis is transluminally advanced through the body lumen from a
remote location to a target site in the lumen. In vascular
procedures, the prostheses will typically be introduced
"endovascularly" using a catheter over a guidewire under
fluoroscopic guidance. The catheters and guidewires may be
introduced through conventional access sites to the vascular
system, such as through the femoral artery, or brachial and
subclavian arteries, for access to the target site.
[0003] An endoluminal prosthesis typically comprises at least one
radially expansible, usually cylindrical, body segment. By
"radially expansible," it is meant that the body segment can be
converted from a small diameter configuration (used for endoluminal
placement) to a radially expanded, usually cylindrical,
configuration which is achieved when the prosthesis is implanted at
the desired target site. The prosthesis may be non-resilient, e.g.,
malleable, thus requiring the application of an internal force to
expand it at the target site. Typically, the expansive force can be
provided by a balloon catheter, such as an angioplasty balloon for
vascular procedures. Alternatively, the prosthesis can be
self-expanding. Such self-expanding structures are provided by a
temperature-sensitive superelastic material, such as Nitinol, which
naturally assumes a radially expanded condition once an appropriate
temperature has been reached. The appropriate temperature can be,
for example, a temperature slightly below normal body temperature;
if the appropriate temperature is above normal body temperature,
some method of heating the structure must be used. Another type of
self-expanding structure uses resilient material, such as a
stainless steel or superelastic alloy, and forming the body segment
so that it possesses its desired, radially-expanded diameter when
it is unconstrained, e.g., released from radially constraining
forces a sheath. To remain anchored in the body lumen, the
prosthesis will remain partially constrained by the lumen. The
self-expanding prosthesis can be delivered in its radially
constrained configuration, e.g. by placing the prosthesis within a
delivery sheath or tube and retracting the sheath at the target
site. Such general aspects of construction and delivery modalities
are well-known in the art and do not comprise part of the present
invention.
[0004] The dimensions of a typical endoluminal prosthesis will
depend on its intended use. Typically, the prosthesis will have a
length in the range from 0.5 cm to 10 cm, usually being from about
0.8 cm to 5 cm, for vascular applications. The small (radially
collapsed) diameter of cylindrical prostheses will usually be in
the range from about 1 mm to 10 mm, more usually being in the range
from 1.5 mm to 6 mm for vascular applications. The expanded
diameter will usually be in the range from about 2 mm to 42 mm,
preferably being in the range from about 3 mm to 15 mm for vascular
applications.
[0005] One type of endoluminal prosthesis includes both a stent
component and a graft component. These endoluminal prostheses are
often called stent grafts. A stent graft is typically introduced
using a catheter with both the stent and graft in contracted,
reduced-diameter states. Once at the target site, the stent and
graft are expanded. After expansion, the catheter is withdrawn from
the vessel leaving the stent graft at the target site.
[0006] Grafts are used within the body for various reasons, such as
to repair damaged or diseased portions of blood vessels such as may
be caused by injury, disease, or an aneurysm. It has been found
effective to introduce pores into the walls of the graft to provide
ingrowth of tissue onto the walls of the graft. With larger
diameter grafts, woven graft material is often used. In small
diameter vessels, porous fluoropolymers, such as PTFE, have been
found useful.
[0007] Coil-type stents can be wound about the catheter shaft in
torqued compression for deployment. The coil-type stent can be
maintained in this torqued compression condition by securing the
ends of the coil-type stent in position on a catheter shaft. The
ends are released by, for example, pulling on wires once at the
target site. See, for example, U.S. Pat. Nos. 5,372,600 and
5,476,505. Alternatively, the endoluminal prosthesis can be
maintained in its reduced-diameter condition by a sleeve; the
sleeve can be selectively retracted to release the prosthesis. A
third approach is the most common. A balloon is used to expand the
prosthesis at the target site. The stent is typically extended past
its elastic limit so that it remains in its expanded state after
the balloon is deflated. One balloon expandable stent is the
PALMAZ-SHATZ stent available from the CORDIS Division of Johnson
& Johnson. Stents are also available from Arterial Vascular
Engineering of Santa Rosa, Calif. and Guidant Corporation of
Indianapolis, Ind.
SUMMARY OF THE INVENTION
[0008] The present invention is directed to an endoluminal
prosthesis configured to help avoid trauma to a patient's
tissue.
[0009] One aspect of the invention is directed to a coiled stent
having a coiled stent body with a main body portion and end
portions. The end portions are substantially less stiff than the
body portion to help prevent tissue trauma.
[0010] The main body portion may include a ladder-like stent having
edge elements separated by connector elements. The end portions may
have inwardly-tapering portions with blunt tips. The
inwardly-tapering portions may have lengths greater than the
widths. The main body portion may also be designed to have
longitudinal sections with different radial stiffnesses.
[0011] A graft material may be used to cover at least the main body
portion to create a coiled stent graft in which adjacent turns have
gaps defined therebetween to create a generally helical gap. The
generally helical gap helps to promote a helical pattern of tissue
ingrowth so that even if substantial tissue ingrowth occurs, the
vessel will be much less likely to be sealed off than if the
exposed tissue defined a circular pattern. The use of the generally
helical gap may help speed up healing because the generally helical
gap may help cells to proliferate more evenly between the coils and
may enhance non-turbulent flow to help reduce restenosis.
[0012] Further aspects of the invention relates to an endoluminal
prosthesis having a body with side elements separated by connector
elements and a placement method therefore. The body is placeable in
a contracted, reduced diameter state and a relaxed, expanded state.
The connector elements are generally parallel to the axis of the
body when placed in the contracted, reduced-diameter state,
typically surrounding a placement catheter.
[0013] According to another aspect of the invention the endoluminal
prosthesis includes a coiled body having first and second ends and
a main portion therebetween. The main portion has an average
cross-sectional dimension of x. At least one of the first and
second ends has a maximum cross-sectional dimension of about
5.times.to 25.times. and a blunt tip to avoid trauma to the
patient's tissue. The tip typically has a flattened, generally oval
shape while the main body portion typically has a rectangular
cross-sectional shape.
[0014] Other features and advantages of the invention will appear
from the following description in which the preferred embodiments
have been set forth in detail in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is an overall view of a catheter assembly using a
straight stent embodiment;
[0016] FIG. 1A is an enlarged cross-sectional view taken along line
1A-1A of FIG. 1;
[0017] FIG. 1B is an enlarged simplified partial cross-sectional
view of the distal portion of the catheter of FIG. 1, with the
addition of a general tubular external graft, to illustrate the
relative relationship between the various components;
[0018] FIG. 2A illustrates the catheter of FIG. 1A introduced into
a blood vessel at a target site after the sheath has been pulled
back to expose the stent and balloon at the target site, the graft
of FIG. 1B being omitted from FIGS. 2A-2G for clarity of
illustration;
[0019] FIG. 2B is similar to FIG. 2A with the distal portion of the
balloon partially inflated to cause the first, distal stent portion
to disengage from the first stent portion holder;
[0020] FIG. 2C is similar to FIG. 2B but after the balloon has been
deflated which permits the distal portion of the stent to spin
relatively freely and thus expand to press against the inside wall
of the blood vessel;
[0021] FIG. 2D illustrates the balloon fully reinflated and showing
the second, proximal end of the stent disengaged from the second
stent end holder;
[0022] FIG. 2E is similar to FIG. 2D but with the balloon fully
deflated;
[0023] FIG. 2F shows the stent in its second, expanded-diameter
state after withdrawal of the distal portion of the catheter
shaft;
[0024] FIG. 3A is an enlarged view illustrating a push wire
extending along the catheter shaft, passing through a push wire
tube to permit the second, proximal end of the stent to be
disengaged from the catheter shaft;
[0025] FIG. 3B illustrates the first stent end holder and the
first, distal end of the stent which slidably engages an opening
formed in the first stent end holder;
[0026] FIG. 4A illustrates the stent of FIG. 2G with the external
graft of FIG. 1B surrounding the stent and held against the inner
wall of the blood vessel by the stent;
[0027] FIG. 4B illustrates the stent of FIG. 2G with an internal
graft;
[0028] FIG. 4C illustrates fastening an internal graft to an
external stent using strips of graft material creating pathways for
the stent;
[0029] FIG. 4D illustrates an alternative coil-type stent in which
the stent comprises a pair of spaced-apart coiled stent wires;
[0030] FIG. 4E illustrates a stent graft in which parallel stent
wires are kept in a spaced-apart relationship by spacers, the
coiled stent wires being covered on both the inside and the outside
by graft material, only a portion of the stent of FIG. 4A shown
covered by the graft material to illustrate the arrangement of the
coiled stent wires and spacers;
[0031] FIG. 5 shows a bifurcated version of the catheter and
balloon allowing for deployment of a bifurcated prosthesis, the
prosthesis not shown;
[0032] FIG. 6 illustrates a bifurcated stent;
[0033] FIG. 7 shows the bifurcated stent of FIG. 6 loaded onto the
bifurcated catheter of FIG. 5 with the balloon deflated;
[0034] FIG. 7A is an enlarged cross sectional view taken along line
7A-7A of FIG. 7;
[0035] FIG. 8 shows the bifurcated stent of FIG. 7 deployed in a
bifurcated vessel with the balloon inflated;
[0036] FIG. 9 shows the stent of FIG. 8 deployed in the vessel and
the withdrawal of the catheter;
[0037] FIG. 10 shows a bifurcated catheter with a spring member
used to keep the catheter shaft arms apart;
[0038] FIG. 11 illustrates a stent blank used to create a coiled
stent similar to that shown in FIG. 4E;
[0039] FIG. 12 illustrates a stent blank similar to that of FIG. 11
but having different thickness along its length;
[0040] FIG. 13 illustrates a stent graft in a radially expanded
condition, the stent graft including a stent similar to that shown
in FIG. 11 covered with a sleeve of porous graft material, the
stent graft having a central turn with a greatly increased pitch
for placement at a branching intersection;
[0041] FIG. 14 illustrates a stent graft similar to that of FIG. 13
but in which one end of the stent graft has much greater radially
expanded diameter than the other portion to accommodate a vessel
having different internal diameters;
[0042] FIG. 15 illustrates an alternative embodiment to the stent
graft of FIG. 13 in which the stent graft has a large expanded
diameter and also has the one turn with the greater pitch at one
end of the stent graft;
[0043] FIG. 15A shows a stent graft similar to that of FIG. 13 but
with generally evenly-spaced turns;
[0044] FIG. 16A is an overall view of the distal end of a
three-shaft deployment catheter used to deploy the stent grafts of
FIGS. 13-15;
[0045] FIG. 16B is an end view of the shafts of 16A;
[0046] FIG. 16C is an embodiment similar to the catheter of FIG.
16A but including only inner and outer shafts;
[0047] FIG. 16D illustrates a proximal end adapter mounted to the
proximal end of the catheter of FIG. 16C;
[0048] FIG. 16E illustrates an alternative embodiment of the
catheter of FIG. 16C;
[0049] FIGS. 16F and 16G are simplified side and cross-sectional
views of a further alternative embodiment of the catheter of FIGS.
16A and 16B;
[0050] FIG. 17A illustrates the stent graft of FIG. 13 tightly
wrapped about the distal end of the catheter of FIGS. 16A and 16B
and placed within a vessel with the intermediate portion of the
stent graft at the intersection of the main and branching
vessels;
[0051] FIG. 17B illustrates the release of the proximal half of the
stent graft;
[0052] FIG. 17C illustrates the release of the distal half of the
stent graft prior to the removal of the catheter shafts;
[0053] FIGS. 18 and 19 illustrate the placement of radiopaque marks
at different positions along a coiled ladder-type stent having a
central turn with a greatly increased pitch;
[0054] FIG. 20 illustrates one example of a radiopaque marker
shaped to permit the determination of the orientation of the
prosthesis as well as its location; and
[0055] FIG. 21 illustrates a coiled prosthesis having enlarged
blunt ends to help prevent tissue trauma.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0056] FIG. 1 illustrates a catheter assembly 2 including broadly a
catheter 4 extending from a proximal end adaptor 6, the catheter
having an introducer sheath 8 slidably mounted over the catheter.
Proximal end adaptor 6 includes a body 10 to which a push wire
manipulator 14 is slidably mounted. Proximal end adaptor 6 also
includes an inflation port 16, to permit a balloon, discussed
below, to be inflated and deflated during use, and a guidewire port
17.
[0057] Catheter 4 includes elongate catheter shaft 18 defining
three lumens therein. FIG. 1A illustrates an inflation lumen 20,
coupled to inflation port 16, a guidewire lumen 22 housing a
guidewire 24, the proximal end of the guidewire passing through
guidewire port 17. The catheter shaft 18 also includes a push wire
lumen 26 housing a push wire tube 28, a push wire 30 being housed
within push wire tube 28. Push wire 30 is connected to push wire
manipulator 14 and is pushed and pulled through push wire tube 28
by the movement of manipulator 14. Push wire tube 28 is used to
help prevent push wire 30 from buckling, which may occur during use
due to the relatively thin diameter of the push wire, typically
about 0.10 to 76 mm (0.004 to 0.030 inch). The distal end of
guidewire 24, not shown, is positioned near the tip 32 of catheter
shaft 18 and is used to help guide tip 32 through the body,
typically through blood vessels, as is conventional. During the
typically percutaneous introduction of the distal portion 34 of
catheter 4 into the vasculature, sheath 8 is in the distal position
shown in FIG. 1 to cover up the balloon 36, stent 38, and graft 40
as shown in FIG. 1B.
[0058] Once in position at the target site 42 in blood vessel 44,
see FIG. 2A, handle 46 of introducer sheath 8 is pulled in a
proximal direction to expose graft 40, stent 38, and balloon 36.
Note that in FIGS. 2A-2F, graft 40 is not shown for clarity of
illustration.
[0059] Stent 38 is a coil-type of stent typically made of 0.10 to
0.76 mm (0.004 to 0.030 inch) diameter Nitinol wire. Stent 38 may
be made of other materials including stainless steel, Elgiloy.RTM.,
a cobalt-chromium-nickel alloy made by Elgiloy Inc., and polymers.
Stent 38, when in a relaxed state, typically has a diameter of
about 2 to 30 mm to accommodate blood vessel 44 having an internal
diameter of about 2 to 30 mm. The wire diameter, coil diameter, and
other properties of stent 38 may vary according to the particular
body region to be accessed and the procedure to be conducted. In
FIGS. 1B and 2A, balloon 36 is in a deflated condition while stent
38 is in a first, reduced-diameter state with the coil-type stent
38 in torqued compression onto catheter shaft 18 and balloon 36.
Stent 38 includes a proximal end 48, shown also in FIG. 3A, which
is housed within a hollow interior of a stent end holder 50.
Proximal end 48 of stent 38 can be selectively dislodged from
proximal stent end holder 50 by the distal movement of push wire 30
through push wire tube 28. In this embodiment, proximal stent end
holder 50 is an extension of push wire tube 28 as suggested in FIG.
3A. Instead of push wire 30, push wire tube 28 could be pulled into
catheter shaft 18 to release proximal end 48 of stent 38.
[0060] It may be desired that the length of stent 34 be about the
same when in the reduced-diameter state as when in the relaxed,
enlarged-diameter state. This is desirable to minimize shifting of
the stent at the target site during deployment. The use of a
coil-type stent helps to achieve this by permitting the appropriate
spacing the turns of the stent onto the balloon-covered catheter
shaft when in a reduced-diameter state. For example, stent 38
having a relaxed diameter of 6 mm, a relaxed length of 5 cm and 10
turns in a relaxed state, can be wound onto the balloon-covered
catheter shaft to assume a reduced-diameter state with about 30
turns, a diameter of about 2.5 mm and the same length of about 5
cm. The results will vary depending on various factors, such as the
pitch of the coil.
[0061] A proximal end 52 of balloon 36 is spaced-apart from stent
end holder 50 by a distance sufficient to permit at least one turn,
and preferably one-and-a-half to two turns, of stent 38 to be
wrapped directly around catheter shaft 18 without any of balloon 38
being between stent 38 and catheter shaft 18. The purpose of this
is to inhibit the dislodgment of proximal end 48 from stent end
holder 50 upon the initial inflation of balloon 36 as will be
discussed in more detail below. Thus, the initial turn or turns of
stent 38 are in effective contact with catheter shaft 18 because
there is no portion of balloon 36 between the turn or turns of the
stent and the catheter shaft.
[0062] The distal end 54 of balloon 36 is positioned near the
distal stent end holder 56. Accordingly, when the distal stent end
58 is engaged within distal stent end holder 56, stent 38 quickly
starts wrapping around balloon 36. Thus, upon inflation of balloon
36, distal stent end 58 is pulled from distal end holder 56 as
shown in FIG. 2B. Note that in FIG. 2B, balloon 36 is only partly
inflated. Inflation of distal end 54 of balloon 36 is aided in this
embodiment by somewhat more loosely wrapping stent 38 around the
balloon at distal end 54 than over the remainder of the balloon.
This reduces the resistance to inflation of the balloon at distal
end 54 thus permitting the expansion of the distal end of stent 38
before expansion at its proximal end. Other ways to promote this
initial expansion of distal end 54 of balloon 36, such as making
distal end 54 easier to expand than the remainder of the balloon or
only partially retracting sleeve 8 or using a balloon with
separately inflatable proximal and distal portions, can be
used.
[0063] After this partial expansion of balloon 36, the balloon is
deflated as shown in FIG. 2C. This permits stent 38 to more freely
expand within blood vessel 44 so that a greater portion of the
stent is in its expanded state in FIG. 2C than in FIG. 2B. FIG. 2D
illustrates balloon 36 after having been fully inflated and the
dislodgment of proximal end 48 of stent 38 from proximal end stent
holder 50 by moving push wire 30 distally through the manipulation
of push wire manipulator 14. This dislodgment of proximal end 48
preferably occurs after the full inflation of balloon 36; it could
also occur before the full inflation of the balloon as well.
[0064] FIG. 2E illustrates balloon 36 deflated leaving stent 38 in
its expanded-diameter state pressing graft 40, not shown in FIGS.
2A-2F but shown in FIG. 4A, against the inner wall of blood vessel
44. Though not always necessary, it may be desired to move sheath
40 in a distal direction to cover balloon 36 prior to removing the
distal portion of the catheter shaft. FIG. 2F illustrates stent 38
in its expanded-diameter state after removal of catheter shaft 18
and sheath 8. It can be noted that in FIGS. 1B and 4A the length of
graft 40 is shorter than the length of stent 38; this helps to
ensure that the ends of graft 40 are pressed against the interior
of blood vessel 44.
[0065] In use, the user introduces distal portion 34 of catheter 4
into, for example, a suitable blood vessel 44 and directs tip 32 of
catheter shaft 18 to a target site 42 using guidewire manipulator
12 and appropriate visualization techniques as is conventional.
Balloon 36 is partially inflated through inflation port 16 to the
condition of FIG. 2B causing distal stent end 58 to be dislodged
from distal stent end holder 56. Balloon 36 is then deflated to
permit a distal portion of stent 38 to more fully expand within
blood vessel 44. Balloon 36 is then fully expanded as shown in FIG.
2D and push wire 30 is extended by moving push wire manipulator 14
in a distal direction causing proximal end 48 of stent 36 to be
dislodged from proximal stent end holder 50; alternatively, push
wire 30 could be extended to first dislodge proximal end 48 of
stent 38B from proximal end stent holder 50 and then balloon 36
could be fully expanded. The inflation of balloon 36 also expands
graft 40. Balloon 36 is then deflated as shown in FIG. 2E and
withdrawn into sheath 8. A distal portion of catheter shaft 18 and
balloon 36 therewith are then withdrawn from target site 42 in
blood vessel 44 (see FIG. 2F) leaving stent 38 and graft 40, which
together constitute a stent graft 59, in place as shown in FIG.
4A.
[0066] FIG. 4B illustrates an alternative embodiment in which graft
40A is an internal graft coupled to stent 38. One method of
coupling internal graft 40A to stent 38 is through the use of one
or more strips 60 of graft material. Pockets, not shown, are
created between stent 40A and strips 60 to permit stent 38 to pass
between the two. The gaps are relatively large to prevent graft 40A
from being overly deformed during the deployment of the stent and
graft.
[0067] FIG. 4D illustrates a stent 38A made up of a pair of
spaced-apart coiled stent wires joined together at their ends. To
permit the ends of stent 38 to be secured to catheter shaft 18, the
stent end holders could, for example, be modified to accommodate
the generally U-shaped ends or the ends could be squeezed together
or otherwise made to form a pointed end as suggested by the dashed
lines at one end of stent end 38A.
[0068] FIG. 4E illustrates a presently preferred embodiment in
which a stent 38B is made up of a pair of coiled stent wires 62
joined together and maintained in a spaced-apart relationship by
spacer wires 64 to create a ladder-like stent 38B. A strip 66 of
graft material is secured to coiled stent wire 62 to form a spiral
graft 40B surrounding stent 38B to lie on both the inside and the
outside of the stent. Only a portion of stent 38B is covered with
strip 66 to illustrate the construction of the stent. Strip 66 of
graft material can be adhered to stent 38B in a variety of ways
including use of an adhesive, heat welding, or making strip 66 in
the form of a tube or a double-sided strip with a hollow interior
which encases coiled stent wires 62. It can be seen that only one
of the two coiled stent wires 62 extend outwardly at each end of
stent 38B to form the proximal end 48B and the distal end 58B of
stent 38B.
[0069] Ladder-like stent 38B could also be made from a tube or
sheet of stent material by, for example, stamping, laser cutting,
waterjet cutting or other suitable processes. It is expected that
processes which do not overly heat the stent material, such as
waterjet cutting, may be preferred. The graft material can be in
the form of a tube of graft material which is slid over ladder-like
stent 38B and secured in place by, for example, suturing the ends
of the graft material.
[0070] FIG. 5 shows a distal portion 34D of a bifurcated catheter
made according to the invention with like reference numerals
referring to like elements. Catheter shaft 18D includes first and
second arms 70, 72 terminating at first and second tips 74, 76. In
FIG. 5 neither a stent, shown in FIG. 6, nor graft material is
illustrated for clarity of illustration. Balloon 36D is a
bifurcated balloon having a first portion 78 extending along first
arm 70 and a second portion 80 extending along second arm 72.
Proximal stent end holder 50 is carried on catheter shaft 50D while
distal stent end holder 56D is positioned along first arm 70D. The
stent end holders 50D, 56D are similar to stent end holders 50, 56
illustrated in FIGS. 3A and 3B with the hollow tubular members
extending distally for proximal stent end holder 50 and proximally
for distal stent end holder 56D. A second distal stent end holder
82 is carried along second arm 72 and has a distally extending
open-ended tube 84 corresponding to push wire tube 28D in that it
also extends in a distal direction and uses a push wire to
disengage the end of a stent from within the push wire tube 84. As
discussed above, other methods for removing the ends of the stents
from push wire tubes 28D, 84 such as retracting the push wire tubes
proximally, could also be used.
[0071] FIG. 6 illustrates a bifurcated stent 38D having a main
portion 86 and first and second arms 88, 90 which are wrapped
around main portion of catheter shaft 18D and first and second arms
70, 72 respectively. Arm 88 is an extension of main portion 86; arm
90 is joined to arm 88 and main portion 86 at junction 102.
Proximal end 48D of stent 38D corresponds to proximal end 48 of
stent 38 as shown in FIG. 3A while distal end 58D of stent 38D
corresponds to distal stent end 58 of stent 38 shown in FIG. 3D.
Proximal and distal ends 48D, 58D engage proximal and distal stent
end holders 50D, 56D in manner similar to those of FIGS. 3A and 3B.
However, the distal end 92 of second arm 90 may have a reverse
bend.
[0072] As shown in FIG. 7A, catheter shaft 18D defines three
lumens, inflation lumen 20D, guidewire lumen 22D, housing tube
guidewires 24D, one for each arm 70, 72, and a push wire lumen 26D
housing push wire tubes 28, 84 with push wires 30D slidingly
passing within the push wire tubes 28D, 84.
[0073] FIG. 7 illustrates distal catheter portion 34D with balloon
36D in a collapsed state, stent 38D wrapped around both balloon 36D
and distal portion 34D, and showing the outline of a branched
vessel 44D shown in dashed lines. Again, as with FIGS. 2A-2F, graft
material is not shown for ease of illustration. However, as with
the embodiments of FIGS. 1-4, graft material is typically used with
stent 38D. Of course other types of stents, other than the coiled
bifurcated stent shown in FIG. 6, could be used as well. The
placement of stent 38D occurs in substantially the same fashion as
can occur with the straight stent described above. The main
difference is that proximal ends 48D and 92 of stent 38D are both
released using push wires 30D while distal stent end 58D is
released by the partial inflation of balloon 36D. FIG. 8
illustrates the result of having gone through the stent end release
cycle, that is typically partial inflation, which releases stent
end 58D, deflation and then the full inflation and release of stent
ends 48D, 92. After stent 38D has been expanded, distal catheter
portion 34D and balloon 36D therewith are removed from the
bifurcated target site as suggested in FIG. 9. Again, graft
material is not shown for clarity of illustration. As with the
above embodiments, graft material may not be, but often is, used
with the stent or other prosthesis.
[0074] FIG. 10 illustrates a distal catheter portion 34E similar to
that shown in FIG. 5 in which the first and second arms 70, 72 are
biased outwardly at their junction 94 by a biasing element 96 which
tends to separate arms 70, 72 from one another. Biasing element may
be made of a variety of materials, such as a leaf spring or, as
illustrated, a triangular section of a resilient spongy material
such as silicone or polyurethane. Using biasing element 96 helps to
ensure arms 70, 72 are directed down different vascular segments
98, 100. To do so distal catheter portion 34E is typically housed
within sheath 8 until just above the target site. At that point,
distal portion 34E is extended out through the open distal end of
introducer sheath 8 permitting arms 70, 72 to move freely into
vascular segments 98, 100. This movement may be aided using
guidewires 24D in addition to biasing element 96.
[0075] Modifications and variation may be to the above-described
catheter assembly and method may be made. For example, it may not
be necessary to only partly inflate the balloon as indicated in
FIG. 2B; rather, it may be desired to fully inflate the balloon to
release distal stent end 58 from distal stent end holder 56. Also,
it may not be necessary to deflate the balloon after the full or
partial inflation of the balloon as shown in FIG. 2C. In a
preferred embodiment, a coiled stent is placed in torqued
compression onto the catheter shaft and balloon. Other types of
radially expanding stents, which may or may not be self-expanding,
can be used as well. For example, tubes of stent material having
numerous axially extending slits which permit the tube to be
expanded radially in a diamond-like pattern using the balloon can
be used. The stent could also be made of a temperature-sensitive
shape-memory material. In the preferred embodiment, balloon 36 is
necessary to expand graft 40 from its reduced-diameter state of
FIG. 1B to its expanded-diameter state of FIG. 4A; graft material
may be used which does not require a balloon to place it into its
fully expanded condition. In the preferred embodiment, graft 40 is
an expandable, porous PTFE graft material such as that available
from IMPRA, Baxter, W. L. Gore or Atrium. Other types of graft
material, such as polyester or polyurethane, can be used. Instead
of mechanically releasing proximal end 48 of stent 38, the proximal
end can be held and selectively released by electrolytic methods as
shown in U.S. Pat. No. 5,122,136 to Guglielmi, et al. Distal stent
end 58 could be releasably coupled to catheter shaft 18 for release
by inflation of balloon 36 by other than holder 56, such as through
a releasable or breakable tether, a clip or other fastener,
adhesive or other releasable or breakable structure. The holding
and selective release of proximal stent end 48 could be by using a
range of conventional or unconventional holders; for example, the
distal end of sheath 8 could be left to cover the proximal end 52
of balloon 36 during the initial inflation of balloon and then
pulled back to uncover the proximal balloon end for the subsequent
inflation of the balloon. Pull or push wires could be used to
actuate a catch to release proximal stent end 48. Conventional
techniques, such as those shown in U.S. Pat. Nos. 5,372,600;
5,476,505; 5,683,451; 5,443,500; 4,913,141; 5,246,445; 5,360,401;
5,201,757; 4,875,480; 4,848,343; 4,732,152; and 4,665,918, and
those shown in WO 97/07756 and WO 94/16629, may also be used to
release proximal stent end 48.
[0076] Bifurcated embodiments have been shown illustrating use of a
single balloon. If desired, a number of separate balloons could be
used instead of a single balloon. For example, three separate
balloons could be used, one for each branch of the stent. The three
balloons could be all coupled to a single inflation lumen; in such
case the three separate balloons would act similarly to the single
balloon. However, if each balloon were separately inflatable, more
than one of the stent ends could be released through the inflation
of the various balloons. Stent 38D is shown with main portion 86
and first and second arms 88, 90 secured together at a common
location 102. It may be desired to have, for example, second arm 90
be joined to a section of stent 38D between main portion 86 and
first arm 88 by a sliding connection; this may be useful to help
properly seat or orient the stent or a stent graft within the
bifurcated vessel. First arm 88 is shown as a single continuous
coil in FIG. 6. If desired, first arm 88 could include one or more
separate sections of stent to create the first arm. Instead of
having a single catheter split into two catheter arms, second arm
72 could actually be a separate catheter extending through the
interior of catheter shaft 18D; this would facilitate inflating a
balloon associated with the second arm separately from the one or
more other balloons associated with the main portion of the
catheter shaft and the first arm. It may also permit the second arm
of the catheter shaft to move longitudinally relative to the main
catheter shaft and the first arm of the catheter shaft.
[0077] FIG. 11 illustrates a stent blank 104 used to create a
coiled stent similar to that shown in FIG. 4E. Stent blank 104
includes a main body portion 106 and first and second end portions
108. Main body portion 106 includes side edge or rail elements 110
connected by connector or rung elements 112. Rung elements 112 are,
as shown in FIG. 11, at an angle to rail elements 110 so that when
stent blank 104 is formed into a coiled stent and tightly wrapped
about an introducer catheter, such as in FIG. 17A, rung elements
112 are axially-extending so that they lie flat for a tighter
wrap.
[0078] End portions 108 are thinner and thus more flexible than
main body portion 106. In addition, end portions 108 have an
inwardly tapering portion 114 terminating at a blunt tip 115. The
shape of end portions 108 and the lessened stiffness of the end
portions, compared to body portion 106, help to prevent tissue
trauma during use. This type of coiled stent in which the end
portions 108 are less stiff than the main body portion 106 can find
particular utility in stabilizing a traumatic injury site within a
patient, such as in the case of a dissection, flap or false lumen.
End portion 108 could also be stiffer than main body portion; this
embodiment may be useful, for example, when treating occlusive
disease on either side of a branch vessel.
[0079] FIG. 12 illustrates a stent blank 104A similar to stent
blank 104 of FIG. 11 but in which main body portion 106A has three
different radial stiffnesses. That is, main body portion 106A has a
first, central longitudinal section 116 of a first, greater
stiffness, and second and third longitudinal sections 118, 120 on
either side of first section 116. Sections 118, 120 are
successively thinner and thus have successively lower radial
stiffnesses when stent blank 104A is formed into a coiled stent.
End portion 108A acts as the fourth longitudinal section with the
least radial stiffness of any of the sections in this embodiment.
Instead of a set of generally discrete radial stiffnesses, the
radial stiffness could vary continuously along at least part of the
length of stent blank 104A, and then along the resulting stent
body.
[0080] In addition to providing less traumatic end portions 108,
108A, a coiled prosthesis formed from either of stent blanks 104,
104A, when uncoiling, will have a tendency to open up first in the
center, because of the greater stiffness at the center, followed by
the ends. This helps to reduce the degree to which the end portions
108, 108A are dragged along the surface of the vessel or other
hollow body structure as the prosthesis is released.
[0081] FIGS. 13, 14, 15 and 15A illustrate four stent graft
embodiments 122, 122A, 122B, 122C. Stent graft 122 includes a
ladder-type coiled stent formed from stent blank 104 and covered
with tubular graft material 124. Graft material 124 is preferably
porous PTFE or ePTFE. The ends 126 of graft material 124 are
sealed, or for example, by using an adhesive or by placing a
suitable heat seal material, such as FEP (fluorinated ethylene
propylene) or other thermoplastic materials, between the layers of
the graft material 124 and applying heat and pressure. The porous
nature of the graft material permits sealing in this manner in
spite of the inert nature of PTFE. In addition, a direct bond of
the PTFE to itself, via a process known as sintering, may be
employed. Other methods for sealing ends 126 could also be used.
Coiled stent graft 122 includes a number of spaced apart turns 128
defining a generally helical gap 130 therebetween. The helical
nature of the gap 130 is believed to help prevent restenosis in two
ways. First, the helical nature of stent graft 122 and of gap 130
is expected to help induce a blood flow pattern which helps to
reduce plaque build up. Second, if plaque build up does occur along
the edges of helical gap 13, the helical nature of gap 13 is
expected to help cells to proliferate more evenly between adjacent
turns 128 and may enhance non-turbulent flow to help reduce
restenosis.
[0082] The average width of helical gap 130 is equal to about 0% to
1200% of the average width of turns 128. More typically the average
width of gap of 130 is about 50% to 800% of the average width of
turns 128 when stent graft 122 is deployed. Also, stent graft 122
has a generally constant pitch except at its central region. The
pitch of a central turn 132 of stent graft 122 is substantially
greater than the pitch of its adjacent turns 128 to accommodate
placement of stent graft 122 at the intersection of a main or first
vessel and a branching vessel as will be discussed in more detail
with reference to FIGS. 17A-17C.
[0083] FIG. 14 illustrates a stent graft 122A in which a central
turn 132A also has an increased pitch as opposed to adjacent turns
128A. However, the turns on one side of central turn 132A have a
larger fully-expanded diameter than turns on the other side to
accommodate transition between smaller and larger diameter
vessels.
[0084] FIG. 15 illustrates a stent graft 122B designed for
placement with the end turn 134 having a substantially greater
pitch than its adjacent turn 128B. Stent graft 122B is used when
one end of the stent graft is to be positioned at the intersection
and main and branching vessels so that the stent graft extends to
one side of the intersection as opposed to both sides as in the
embodiments of FIGS. 13 and 14. FIG. 15A illustrates stent graft
122C, which may be used at locations other than bifurcations,
having generally uniformly spaced turns 128C.
[0085] FIGS. 16A-16B illustrate a catheter 136 used for deploying
the stent grafts of FIGS. 13 and 14. Catheter 136 includes outer,
intermediate and inner rotating, telescoping shafts 138, 140, 142
each having a distal end 144, 146, 148. Each of the shafts has a
prosthesis portion holder 150, 150A, 150B at its distal end 144,
146, 148. Prosthesis portion holders 150, 150A, 150B include pull
wires 152, 152A, 152B which pass along axially-extending lumens
154, 154A, 154B formed in the body of shafts 138, 140, 142, out of
exit holes 156, 156A, 156B, across gaps 158, 158A, 158B and back
into reinsertion openings 160, 160A, 160B. Pull wires 152, 152A,
152B pass through and engage different portions of, for example,
stent graft 122 and secure those portions of the stent graft to
shafts 138, 140, 142. As shown in FIG. 17A, prosthesis portion
holder 150B at distal end 148 of inner shaft 142 engages the distal
end 166 of stent graft 122. Holders 150, 150A at distal ends 144,
144A of outer and intermediate shafts 138, 140 engage proximal end
168 and central turn 132 of stent graft 122, respectively. One or
more of shafts 138, 140, 142 may be braided to enhance torquing
stiffness to aid rotation.
[0086] FIG. 16C illustrates the distal end of a catheter 136A
including only two shafts, outer shaft 138A and inner shaft 142A.
Catheter 136A is typically used when placing an endoluminal
prosthesis of the type which does not have a central turn with an
increased pitch, such as those of FIGS. 15 and 15A, and thus does
not need a catheter with an intermediate shaft.
[0087] FIG. 16D illustrates, in a simplified form, a proximal end
adapter 170 mounted to the proximal end of catheter 136A of FIG.
16C. Proximal end adapter 170 includes distal and proximal portions
172, 176 through which catheter 136A passes. Proximal end adapter
170 provides for the rotation of either or both shafts 138A, 142A
through the manipulation of thumb wheel 174 mounted to portion 176.
A flip lever 175 extends from distal portion 172 and is movable
between secured and released positions to either secure shafts
138A, 142A to one another or to permit shafts 138A, 142A to move
axially relative to one another. Pull wires 152, 152B are normally
secured to their respective shafts 138A, 142A by deployment knobs
178, 180; pulling on deployment knobs 178, 180 releases pull wires
152, 152B, respectively to permit the pull wires to be pulled to
release the endoluminal prosthesis from the appropriate holder 150,
150B.
[0088] FIGS. 16F and 16G illustrate a further three-shaft
embodiment of the invention similar to the three-shaft embodiment
of FIGS. 16A and 16B. Instead of using lumens 154 to house pull
wires 152, tubular members 162, 162A, 162B, typically hypotubes,
could be secured to the outside of the shafts 138B, 140B, 142B.
Gaps or breaks are provided at the distal ends of hypotubes 162,
162A, 162B to define the gaps 158, 158A, 158B.
[0089] FIG. 17A shows stent graft 122 of FIG. 13 tightly wrapped
about catheter 136. Distal end 166, proximal end 168 and central
turn 132 of stent graft 122 are secured to distal ends 148, 144 and
146 of inner, outer and intermediate shafts 142, 138 140 by
prosthesis portions holders 150. Stent graft 122 is housed within a
main vessel 182 with central turn 132 aligned with the intersection
184 of main vessel 182 and branching vessel 186. To help ensure
proper placement of central turn 132 at intersection 184, stent
graft 122 has one or more remote visualization markers at or
adjacent to turn 132. Radiopaque markers 188, 190 192 are shown in
FIG. 18 at distal, intermediate and proximal portions of the
central turn 194 of stent 196. Radiopaque markers may be shaped to
provide information as to both location and orientation of stent
196 on the catheter. For example, radiopaque marker 190A of FIG. 19
has a broad central portion 190B extending between rail elements
110 and arm portions 190C extending along rail elements 110; this
permits marker 190A to provide both location and orientation
information about stent 196A. Orientation marker 190A is configured
so that the viewer can determine whether the turn is facing the
viewer or is away from the viewer based upon the marker's
orientation. Various other marker shapes to provide both location
and orientation can also be used.
[0090] Radiopaque markers may also be used on the placement
catheter itself. For example, radiopaque markers 191, 193, 195 are
used on shafts 138B, 140B, 142B aligned with their respective
holders 150, 150A, 150B, as shown in FIG. 16F, to indicate the
location of the holders. Radiopaque marker 193 is shown to be
configured as an orientation specific marker to help in the proper
placement of the prosthesis. FIG. 20 illustrates the shape of an
orientation-specific radiopaque marker 197 which could be placed,
for example, on shafts 138, 140, 142 at one or more of the holders
150 of the embodiments of FIGS. 16A, 16C and 16E. Radiopaque or
other remote visualization markers may also be used at other
positions along the endoluminal prosthesis, such as at each end, or
along the placement catheter.
[0091] FIG. 17B illustrates the release of proximal end 168 of
stent graft 122 while FIG. 17C illustrates the subsequent release
of distal end 166 of stent graft 122. It should be noted that
central turn 132 remains secured to intermediate shaft 140 while
the distal and proximal ends 166, 168 of stent graft 122 are
released to ensure that the open region of central turn 122 remains
facing intersection 184 to help ensure substantially unrestricted
fluid flow between main vessel 182 and branching vessel 186. It
should also be noted that prior to releasing the stent graft, the
number of turns can be increased or decreased by the relative
rotation of shafts 138, 140 and 142. Also, the length of stent
graft 122 can be changed by the relative axial sliding motion among
outer, intermediate and inner shafts 138, 140, 142. For example,
instead of simply releasing proximal end 168 of stent graft 122 to
the position shown in FIG. 17B, it may be desired to rotate outer
shaft relative to intermediate shaft 140, keeping intermediate and
inner shafts 140, 142 stationary so to unwind the proximal half of
the stent graft to ensure that the stent graft is properly
positioned prior to releasing the stent graft. Similarly, both
outer shaft and inner shafts can be rotated while maintaining
intermediate shaft stationary to create the expanded diameter
condition of FIG. 17 prior to releasing any portion of the stent
graft. In this way the physician can ensure that stent graft 122 is
properly positioned, especially with respect to central turn 132.
If necessary or desired, intermediate shaft 140 could be, for
example, rotated relative to outer and inner shafts 138, 142 to
help properly position or reposition central turn 132.
[0092] FIG. 17A also shows how by properly selecting the angle of
connector elements 112 relative to side elements 110 for a
placement catheter of a particular outside diameter, connector
elements 112, indicated by dashed lines in FIG. 17A, will lie
generally parallel to the axis of stent graft 122. This permits
connector element 112 to lie closer to catheter 136, to provide a
much smoother wrap when in its contracted, reduced-diameter state,
than would result if connector elements were not generally parallel
to the axis in such a state. This axial orientation can be
contrasted with the off-axis orientation of connectors 112 when in
the expanded diameter state of FIG. 17C. The smoother outer surface
of stent graft 122 enhances the ease of insertion of the stent
graft within a hollow body organ, such as blood vessel 182.
[0093] As discussed above with reference to FIGS. 11 and 12, end
portions 108, 108A of sent blanks 104, 104A are less stiff than
main body portion 106, 106A, as well as having rounded, blunt tips
116, 116A. FIG. 21 illustrates a coiled prosthesis 198 in which the
main body 200 has an average cross-sectional dimension of x while
the enlarged blunt ends 202 have a maximum cross-sectional
dimension 204 of 5x to 25x, and more preferably 5x to 10x. In one
example main body 200 has a rectangular cross-sectional shape with
a minimum width of 0.025 mm (0.001 in) and a maximum width of 1 mm
(0.040 in); enlarged blunt end has a thickness of 0.025 mm (0.001
in) and a maximum cross-sectional dimension 204 of lcm (0.4 in).
This configuration of the ends 202 of prosthesis 198 helps reduce
trauma to the patient's tissue by making the ends of the prosthesis
less stiff and also by providing a much greater surface area so to
reduce the pressure exerted against the tissue, as opposed to what
could be exerted by a coiled prosthesis having a constant
cross-sectional dimension. The example of FIG. 21 could be modified
so that ends 202, rather being solid, are made from loops of wire
with open centers.
[0094] Modification and variation can be made to the above
described inventions without departing from the subject of the
inventions as defined in the following claims. For example,
connectors 112 could be oriented perpendicular to rail elements
110, graft material 124 could be placed upon only a portion of the
underlying stent or on only one side of the underlying stent.
Placement catheter 136 could include fewer or additional
telescoping rotatable shafts. The telescoping shafts may not need
to be coaxial shafts slidable within or over one another; the
telescoping shafts could be, for example, solid and/or tubular
elongate members positioned side-by-side. Holders 150 could be
constructed differently; for example, if the sequence of releasing
the prosthesis is known it may be possible to use a single pull
wire instead of three separate pull wires.
[0095] Any and all patents, applications, and printed publications
referred to above are incorporated by reference.
* * * * *