U.S. patent application number 09/819454 was filed with the patent office on 2002-02-14 for methods and apparatus for intraluminal placement of a bifurcated intraluminal graft.
Invention is credited to Dehdashtian, Mark, White, Geoffrey H., Yu, Weiyun.
Application Number | 20020019665 09/819454 |
Document ID | / |
Family ID | 22759059 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020019665 |
Kind Code |
A1 |
Dehdashtian, Mark ; et
al. |
February 14, 2002 |
Methods and apparatus for intraluminal placement of a bifurcated
intraluminal graft
Abstract
Methods and apparatus for placing a bifurcated aortic graft,
with extensions, into a body lumen. An aortic graft is provided
with a unique combination of self-expanding a balloon expandable
wires. The aortic graft is bifurcated and includes ipsilateral and
contralateral legs. Two extension grafts are provided for
frictional engagement with the legs of the aortic graft. For
placement of the bifurcated aortic graft with extensions, an
introducer assembly including a dilator and a sheath assembly
provides access for the introduction of a main catheter and a
directional catheter. The main catheter is provided for deployment
of the bifurcated aortic graft within the lumen of a vessel. A
balloon is provided on the main catheter for expanding the
balloon-expandable wires of the aortic graft. The directional
catheter, which includes a deflecting spring portion, permits
placement of a guidewire through the ipsilateral leg and into the
contralateral leg of the aortic graft. In turn, a second introducer
sheath and a second catheter assembly are provided contralaterally
for introduction of a graft extension. Upon balloon-expansion, the
graft extension is frictionally engaged with the contralateral leg
of the aortic graft. A third catheter assembly including a second
extension graft is provided for introduction of the extension graft
and balloon-expansion thereof for frictional engagement with the
ipsilateral leg of the graft.
Inventors: |
Dehdashtian, Mark; (Costa
Mesa, CA) ; White, Geoffrey H.; (New South Wales,
AU) ; Yu, Weiyun; (New South Wales, AU) |
Correspondence
Address: |
Edwards Lifesciences LLC
Law Dept.
One Edwards Way
Irvine
CA
92614
US
|
Family ID: |
22759059 |
Appl. No.: |
09/819454 |
Filed: |
March 27, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09819454 |
Mar 27, 2001 |
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09204699 |
Dec 3, 1998 |
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09204699 |
Dec 3, 1998 |
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09163580 |
Sep 30, 1998 |
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Current U.S.
Class: |
623/1.35 ;
623/1.11; 623/1.13 |
Current CPC
Class: |
A61F 2/95 20130101; A61F
2/958 20130101; A61F 2002/075 20130101; A61F 2/954 20130101; A61F
2002/826 20130101; A61F 2/07 20130101; A61F 2/89 20130101; A61F
2250/0048 20130101; A61F 2220/0033 20130101; A61F 2250/0098
20130101; A61F 2002/065 20130101 |
Class at
Publication: |
623/1.35 ;
623/1.11; 623/1.13 |
International
Class: |
A61F 002/06 |
Claims
What is claimed is:
1. An intraluminal prosthesis comprising: a trouser graft having a
trunk and two legs diverging in a downstream direction from the
trunk at a septum region, the graft being formed of a graft body
having an external surface and an internal surface; at least one
balloon-expandable wireform connected to the graft body at the
trunk; at least one self-expanding wireform connected to the graft
body at the septum region; at least one self-expanding wireform
connected to the graft body in each of the two legs.
2. The prosthesis of claim 1, wherein there are at least two
balloon-expandable wireforms connected to the graft body at the
trunk, one of the balloon expandable wireforms being positioned
external to the graft body.
3. The prosthesis of claim 1, further including a tubular extension
connected to a downstream end of each of the two legs.
4. The prosthesis of claim 3, wherein the tubular extensions each
include balloon-expandable wireforms and are connected to the
downstream end of the legs in such a manner that the self-expanding
wireform in each leg exerts a radially inward force on the
balloon-expandable wireform in the associated tubular
extension.
5. An assembly of tubular prostheses, comprising: a first tubular
prosthesis including a graft body and least one self-expanding
wireform, the first tubular prosthesis terminating at a downstream
end in an open mouth; a second tubular prosthesis including a graft
body and at least one balloon-expanding wireform, the second
tubular prosthesis terminating at an upstream end positioned within
the open mouth of the first tubular prosthesis, the second tubular
prosthesis being expanded into contact with the first tubular
prosthesis and sufficiently farther to outwardly stress the
self-expanding wireform in the first tubular prosthesis and produce
an inward compressive force on the upstream end of the second
tubular prosthesis.
6. A method of deploying a bifurcated intraluminal prosthesis to a
site of implantation defined by a main vessel branching to two
smaller vessels, comprising: endoluminally delivering a bifurcated
graft having a trunk and two legs to the site of implantation, the
trunk being positioned within the main vessel; expanding the trunk
with a balloon catheter into contact with the main vessel;
delivering a first tubular extension into position with one end
within one of the two legs and with the other end within one of the
two smaller vessels; expanding the first tubular extension with a
balloon catheter into contact with said one of the two legs and
into contact with said one of the two smaller vessels, the first
leg being expanded beyond a relaxed state so that it imparts an
inward compressive force on the first tubular extension; delivering
a second tubular extension into position with one end within the
other of the two legs and with the other end within the other of
the two smaller vessels; expanding the second tubular extension
with a balloon catheter into contact with said other of the two
legs and into contact with said other of the two smaller vessels,
the second leg being expanded beyond a relaxed state so that it
imparts an inward compressive force on the second tubular
extension.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation-in-part of
co-pending U.S. application Ser. no. 09/163,580, filed Sep. 30,
1998 under the same title.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed generally to methods and
apparatus for positioning an intraluminal graft. More specifically
the present invention is related to methods and apparatus for
positioning an intraluminal graft into a bifurcating vessel such as
an artery.
[0004] 2. Discussion of Related Technology
[0005] An artery or other vessel that is weakened by disease,
injury, or congenital defect, can become distended due to the
pressure of blood or other fluid flowing through the weakened area.
In the vasculature, this distended weakening is called an aneurysm.
An aneurysm typically occurs in the arterial vessels of the head,
chest, or abdomen. The distension may cause the vessel to rupture,
which can have serious, even life-threatening consequences.
[0006] Aneurysms in the abdominal aorta are typically distended
around the circumference of the aorta and tapered at both ends.
Most aneurysms of the abdominal aorta are caused by atherosclerotic
weakening of a segment of the wall. Abdominal aneurysms may cause
backache and severe pain, and may be visible as a throbbing
swelling. If an abdominal aorta ruptures, it is seriously life
threatening.
[0007] Traditionally, aneurysms have been treated by radical
surgical graft replacement. This approach is risky for the patient
and is sometimes not feasible due to other pre-existing disease
states of the patient. More recently, aneurysms have been treated
by placement of an intraluminal or endovascular graft. These
intraluminal or endovascular grafts may be of various types,
including grafts having stents, wireforms, or other attachment
means attached to or integrated into the graft structure.
[0008] In general, intraluminal grafts and their respective support
and/or attachment means fall into two major categories,
self-expanding and pressure expandable. Self-expanding intraluminal
grafts, are supported and/or attached via resilient or shape-memory
material such as spring steel or Nitinol.TM.. Self-expanding
material is capable of being formed in a configuration from which
it may be compressed to a radially compact diameter for placement
within a damaged vessel. At the time of use, the memory feature of
these materials causes them to self-expand from the radially
compact diameter to the expanded operative diameter.
[0009] Pressure-expandable intraluminal grafts are supported and/or
attached via plastically deformable material such as stainless
steel that is initially formed in its radially compact diameter.
This type of material does not have memory, and will remain in the
radially compact diameter until manually expanded. Typically,
outwardly directed pressure is exerted upon the graft through use
of a balloon so as to cause radial expansion and resultant plastic
deformation of the material to its operative diameter.
[0010] Careful positioning and firm implantation of the
intraluminal graft is critical to the successful treatment of the
underlying medical condition. This is particularly difficult to
accomplish when the aneurysm extends from an artery into one or
more divergent arteries. A "trouser graft" has been suggested for
use in a first main artery and a pair of divergent arteries by
White et al. in PCT Application Nos. WO 97/17910; WO 97/17911; WO
97/18006; WO 97/26936; and WO 97/26938; all of which are hereby
incorporated herein by reference in their entireties. A trouser
graft comprises a first tubular body that bifurcates into two
smaller tubular bodies. In the referenced disclosures, the first
tubular body is placed in first artery and the two smaller tubular
bodies are placed so as to extend within the two divergent
arteries.
[0011] Notwithstanding the important teachings of the foregoing
references, features of the aforementioned device have recognized
shortcomings that make them less than complete solutions to the
treatment of aneurysms in the vasculature, or to the treatment of
similar damage to other vessels. The present invention provides
substantial improvements to the methods and apparatus of the prior
art.
SUMMARY OF THE INVENTION
[0012] It is an object of the present invention to provide an
improved intraluminal graft and method for placement of same that
diminishes deleterious kinking and twisting of the graft during and
after placement thereof in a vessel.
[0013] It is another object of the present invention to provide an
improved intraluminal graft and method for placement of same that
provides control over inadvertent longitudinal movement within a
vessel.
[0014] Another object of the present invention is to provide an
improved intraluminal "trouser" graft and method for placement of
same that precludes inadvertent separation of the legs of the
trouser.
[0015] These and other objects and features of the present
invention will become more fully apparent from the following
description and appended claims, or may be learned by the practice
of the invention as set forth hereinafter.
[0016] To achieve the forgoing objects, and in accordance with the
invention as embodied and broadly described herein, the present
invention relates to new and useful apparatus and methods for
placing a bifurcated graft at the site of a damaged vessel. In a
preferred embodiment, the methods and apparatus of the present
invention are directed to placement of a bifurcated graft within an
aneurysm located in the abdominal aorta downstream of the renal
arteries. Preferably, placement of the graft is through the right
femoral artery of a patient.
[0017] An introducer assembly is provided which is configured for
placement over a guidewire and for facilitating the advancement of
various catheter assemblies required in connection with the
practice of the invention. The introducer assembly includes a
sheath, valve head, and a dilator. The sheath is preferably
cylindrical in shape and is formed so as to have an appropriate
flexibility and an outer diameter suitable for placement at the
location of an aneurysm to be repaired. The valve head permits
insertion and removal of various catheters during the method of the
present invention without significant loss of blood from the
femoral artery. The proximal end of the valve head is provided with
a threaded connector which facilitates connection of the valve head
to other catheters. The dilator, which includes a tapered tip, is
placed during use through the valve head and the sheath so that the
tapered tip portion protrudes from the sheath. The dilator tip
portion is capable of being advanced gently through the tortuous
pathway of the vasculature without causing undue trauma or a
perforation, yet is also sufficiently stiff to cause the blood
vessels to assume a less tortuous path.
[0018] Another component of the present invention is a bifurcated
aortic graft. The preferred bifurcated aortic graft includes both
self-expanding and balloon-expandable wireforms along its length.
The balloon-expandable wires permit precision in placement of the
aortic graft. The self-expanding wires open within the vessel
immediately upon deployment from the main catheter assembly, which
allows insertion of other modular components, opens a removal path
for the inflatable balloons, and reduces kinking. The
self-expanding wires also increase the anchoring force between the
bifurcated graft and modular extension grafts used to extend the
bifurcated graft into communication with non-distended vessel
walls.
[0019] One of the self-expanding wireforms is located at a septum
region of the bifurcated graft. The septum region separates an
ipsilateral leg from a contralateral leg ("ipsilateral" and
"contralateral" referring to opposite lateral sides of the patient
depending on the surgical approach). This septum wire prevents and
helps eliminate the kinks that are typically encountered with
conventional bifurcated grafts. In addition, the self-expanding
wireform at the septum region includes crimps functioning as
radiopaque markers generally pointing to the septum region, which
aids in identifying the location of the septum under fluoroscopy.
Two additional self-expanding wireforms are located at the ends of
each leg of the bifurcated graft. These wireforms facilitate
opening the legs immediately upon deployment from the main catheter
assembly to allow for the insertion of modular components. These
leg wireforms also contain crimps as radiopaque markers which aid
in identifying the ends of the bifurcated graft legs. All crimps on
the self-expanding wireforms are placed on the anterior side of the
graft, thus aiding in orientation of the graft under
fluoroscopy.
[0020] The main catheter assembly is utilized to place the aortic
graft described above, which is compressed and loaded onto the
distal end of the main catheter assembly. The main catheter
assembly is sized such that it will fit inside the introducer
sheath.
[0021] The components of the main catheter assembly include the
following: a rigid loader configured for connection to the valve
head of the sheath assembly; a proximal connector assembly
including a distal pusher connector; an elongate, tubular pusher
body; an elongate catheter with a coaxial tube construction; and an
inflatable catheter balloon.
[0022] In addition to the aortic graft, two additional graft
portions are adapted to extend into the respective iliac arteries
to form a frictional engagement with the ipsilateral and
contralateral legs of the aortic graft. These extension grafts
typically comprise straight cylindrical tubes, with an upstream end
having a common diameter. The upstream ends interlock with the
respective downstream portions of the aortic graft.
[0023] The present invention may further include a directional
catheter which permits placement of the graft extensions. The
directional catheter includes a deflecting spring portion, a knob
used to deflect the spring portion, and a connector nut for
connection with the sheath assembly.
[0024] The preferred method for using the aforementioned components
of the present invention includes the following steps. An incision
is made and a primary guidewire is placed in conventional fashion
in the ipsilateral side, that is, for example, through the right
femoral artery and the right common iliac artery so as to extend
well upstream of the aneurysm. The introducer assembly is advanced
over and along the primary guidewire into a position upstream of
the renal arteries. Once the sheath of the introducer assembly has
been properly placed, the dilator is retracted along the guidewire
and then completely removed from within the sheath assembly and
from primary guidewire. The main catheter assembly is inserted over
the primary guidewire and into the sheath assembly, and then
connected thereto. The pusher body is distally advanced to push the
aortic graft and main catheter through to the end of the introducer
sheath. The sheath containing the aortic graft is then retracted
slowly to approximately a desired deployment position in the
abdominal aorta. The introducer sheath is then retracted to a
position just below the septum region, freeing the aortic graft and
exposing it to blood flow.
[0025] The balloon-expandable, upstream portion of the aortic graft
remains in a substantially compressed configuration. The catheter
balloon is inflated which facilitates the concurrent radial
expansion of the balloon-expandable portions of the graft from the
initial, collapsed orientation, to the second, expanded
orientation. In one embodiment of the present invention, the graft
is slightly over-sized to optimize engagement of the aortic graft
with the aortic wall. When the graft is fully expanded, the
upstream end thereof frictionally engages the luminal surfaces of
unaffected regions of the aorta just below the renal arteries.
After the graft has been radially expanded in the aforementioned
manner, the balloon is deflated, longitudinally stretched to
prevent snagging on the graft, and then removed. The main catheter
is then withdrawn slowly and carefully, with the introducer sheath
and the primary guidewire remaining in place.
[0026] For placement of the graft extensions, the directional
catheter is first inserted over the primary guidewire. The spring
portion of the directional catheter is positioned such that it is
above the septum region of the aortic graft. The spring portion is
deflected by pulling proximally on the knob. A supplemental
guidewire is then advanced through the directional catheter and out
the deflected spring portion such that the supplemental guidewire
extends down the contralateral leg and through the left common
iliac artery. The supplemental guidewire is extended until it is in
the left femoral artery, at which time the left femoral artery is
cross-clamped and a cut-down or percutaneous incision is performed
to retrieve the supplemental guidewire. Once the guidewire is
retrieved, a stiffer guidewire is exchange through the left femoral
artery until it is within the first graft and reaches the
contralateral side of the aortic graft. A second introducer
assembly is then introduced over the stiff guidewire.
[0027] A second catheter assembly on which is packaged a tubular
graft extension is then introduced through the second sheath
assembly until the introducer sheath extends through the left iliac
artery and terminates at the bifurcation point of the aortic graft.
The sheath followed by the pusher of the second catheter assembly
are then pulled back proximally to release the tubular graft
extension. The balloon on the second catheter assembly is then
inflated such that the upstream end of the extension graft is
frictionally engaged with the downstream contralateral leg of the
aortic graft. In one embodiment of the present invention, the
extension graft is slightly over-sized such that it optimally
engages with the self-expanding downstream contralateral leg. The
balloon is then deflated and the second catheter assembly is
removed in the manner previously described hereinabove with respect
to the main catheter.
[0028] The directional catheter is also removed such that a third
catheter assembly, on which is packaged a tubular graft extension,
and which may be identical to the second catheter assembly, can be
introduced over the primary guidewire and through the first
introducer sheath assembly. This third catheter assembly is
advanced until the distal end of the extension graft is at the
bifurcation point of the aortic graft. In like manner to that
previously described, a third graft extension positioned on the
third catheter assembly is deployed such that its upstream end is
in contact with the ipsilateral leg of the aortic graft, and its
downstream end is in contact with the right iliac artery. Also as
previously described, the balloon on third catheter assembly is
inflated to expand the balloon expandable extension graft in the
ipsilateral side. In one embodiment of the present invention, the
extension graft is slightly over-sized such that it optimally
engages with the self-expanding downstream ipsilateral leg.
Finally, the balloon is deflated and stretched, and the third
catheter assembly is withdrawn.
[0029] In an alternate embodiment both the ipsilateral and
contralateral balloon catheters could be positioned simultaneously
and inflated sequentially. While maintaining the position of the
third catheter balloon the second catheter balloon is deflated and
stretched and the second catheter is removed. The third catheter
balloon is subsequently deflated, stretched, and removed.
[0030] The second sheath assembly and the stiff guidewires are
withdrawn and the contralateral incision or puncture is sutured. An
angiographic examination may take place to determine if the grafts
are correctly placed and functioning. The first introducer sheath
assembly is withdrawn and the right femoral incision is sutured.
The result is a functioning trouser graft bridging an aneurysm.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] To more fully understand the manner in which the
above-recited and other advantages and objects of the invention are
obtained, a more particular description of the invention will be
rendered by reference to a specific embodiment thereof which is
illustrated in the appended drawings. Understanding that these
drawings depict only a typical embodiment of the invention and are
not therefore to be considered to be limiting of its scope, the
invention in its presently understood best mode for making and
using the same will be described and explained with additional
specificity and detail through the use of the accompanying drawings
in which:
[0032] FIG. 1 is a front view of an aortic graft in accordance with
the present invention;
[0033] FIG. 1A is a perspective view of a cylindrical mandrel for
forming the self-expanding wires of FIG. 1;
[0034] FIG. 1B is a partial plan view of an alternate configuration
for a balloon-expandable wireform in accordance with the present
invention;
[0035] FIG. 2 is front view of a graft extension in accordance with
the present invention;
[0036] FIG. 2A is an internal cross-sectional view of the graft
extension from FIG. 2;
[0037] FIG. 3 is an exploded perspective view of an introducer
assembly of the present invention;
[0038] FIG. 4 is a perspective view of a main catheter assembly of
the present invention;
[0039] FIG. 5 is a front perspective view of a directional catheter
assembly of the present invention;
[0040] FIG. 6 is a side view of the main catheter assembly of FIG.
4 with the expandable balloon shown exposed and in an expanded
configuration;
[0041] FIG. 7A is a partial perspective view of the main catheter
assembly being inserted into the introducer assembly;
[0042] FIG. 7B is a partial perspective view of the main catheter
assembly connected to the introducer assembly;
[0043] FIG. 8A is a schematic cutaway view of the abdominal region
of the human body ("schematic abdominal view") having a guidewire
positioned therein;
[0044] FIG. 8B is a sectional view of an abdominal aorta and
aneurysm ("sectional aneurysmic view") having a guidewire
positioned therethrough;
[0045] FIG. 9A is a schematic abdominal view having an introducer
assembly positioned therein;
[0046] FIG. 9B is a sectional aneurysmic view having an introducer
assembly positioned therethrough;
[0047] FIG. 9C is a schematic abdominal view with an introducer
sheath positioned above the renal arteries and the dilator removed
therefrom;
[0048] FIG. 10A is a schematic abdominal view with the balloon of
the main catheter assembly and aortic graft advanced within the
introducer sheath to the renal arteries;
[0049] FIG. 10B is a sectional aneurysmic view similar to FIG.
10A;
[0050] FIG. 10C is a detailed view of the introducer sheath being
withdrawn to expose the aortic graft therein;
[0051] FIG. 10D is a sectional aneurysmic view with the introducer
sheath withdrawn to a position downstream of the aortic graft;
[0052] FIG. 11A is a schematic abdominal view with the balloon of
the main catheter assembly expanded within a trunk portion of the
aortic graft;
[0053] FIG. 11B is a schematic abdominal view with the balloon of
the main catheter assembly over-expanded within the aortic graft
trunk portion;
[0054] FIG. 12A is a schematic abdominal view with the balloon of
the main catheter assembly deflated within the aortic graft;
[0055] FIG. 12B is a sectional aneurysmic view with the deflated
balloon on the main catheter assembly being stretched to facilitate
removal from inside the aortic graft;
[0056] FIG. 12C is a schematic abdominal view with the main
catheter assembly being withdrawn therefrom and only the main
guidewire extending through the aortic graft;
[0057] FIG. 13A is a schematic abdominal view with the directional
catheter connected to the sheath assembly and positioned within the
aortic graft;
[0058] FIG. 13B is a detailed view of the directional catheter
being deflected around the septum region of the aortic graft;
[0059] FIG. 13C is a sectional aneurysmic view with the directional
catheter advanced to a position above the renal arteries and a
second guidewire positioned within the contralateral side;
[0060] FIG. 14A is a schematic abdominal view with a second
catheter assembly positioned within the contralateral side;
[0061] FIG. 14B is a sectional aneurysmic view with a second
introducer sheath positioned at the septum region and the dilator
removed therefrom;
[0062] FIG. 15A is a sectional aneurysmic view of a balloon of the
second catheter assembly and an associated first extension graft
advanced within the second introducer sheath to the septum
region;
[0063] FIG. 15B is a sectional aneurysmic view with the second
introducer sheath withdrawn to a position downstream of the now
exposed first extension graft;
[0064] FIG. 15C is a sectional aneurysmic view with the first
extension graft from FIG. 15B being expanded from inflation of the
balloon on the second catheter assembly;
[0065] FIG. 16A is a sectional aneurysmic view with a balloon of a
third catheter assembly and an associated second extension graft
advanced within the first introducer sheath on the ipsilateral side
to the septum region of the aortic graft;
[0066] FIG. 16B is a sectional aneurysmic view with the first
introducer sheath withdrawn to a position downstream of the now
exposed second extension graft;
[0067] FIG. 16C is a cross-section along line 16C-16C of FIG. 16B;
and
[0068] FIG. 16D is a sectional aneurysmic view with a fully
deployed aortic graft and first and second graft extensions.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0069] The present invention enables placement of a bifurcated
graft at a site of a damaged vessel, such as an artery, by
minimally invasive techniques rather than an open surgical access
route. Although the methods and apparatus of the present invention
are applicable for various types of body lumens, the description
herein will be directed to placement of a bifurcated graft within
an aneurysm located in the abdominal aorta downstream of the renal
arteries for purposes of brevity and simplicity.
[0070] In addition, a particular procedure is described herein
showing placement of the graft through the right femoral artery of
a patient. This method is presently preferred for several reasons.
For example, it is contemplated that the bifurcated graft of the
present invention will be placed by a vascular surgeon,
interventional radiologist or a cardiologist. As a practical
matter, physicians are accustomed to placing catheters through a
femoral artery entry point, and are less accustomed to other entry
points. Further, since most physicians are right handed, the
preferred insertion will be in the right femoral artery. By
describing this type of insertion, however, it is not intended to
exclude other insertion locations, such as the left subclavian
artery, or the initiation of the procedure through the left femoral
artery. Those of ordinary skill will be able to take the teachings
herein and apply them to other body lumens, other lumen locations,
and other insertion sites.
[0071] As the terms are used herein with reference to the human
body, "upstream" pertains to the direction towards the heart while
"downstream" pertains to the direction away from the heart. When
referring to catheters, "distal" refers to the tip of catheter that
is inserted into a patient and "proximal" refers to the end of the
catheter outside the body of a patient. The orientation of the
graft of the present invention will be referenced with respect to
whether it is carried by the catheter or implanted at the aneurysm
site, Specifically, upstream and downstream will be used to refer
to the portions of the implanted graft closer and farther from the
heart, respectively. Alternatively, when the graft is still carried
on the catheter, distal and proximal will be used to refer to
portions of the graft in accordance with the aforementioned
catheter orientation. Finally, ipsilateral refers to the side of
the patient in which the primary guidewire and main catheter are
inserted (the right femoral artery in the present embodiment),
while contralateral refers to the opposite side.
[0072] Aneurysms frequently form in the abdominal aorta at a
location between the renal arteries and immediately proximal to the
common iliac arteries. FIG. 8A, for example, illustrates the
anatomy of the abdomen in the location of an aortic aneurysm. The
abdominal aorta 100 can be seen branching distally into the common
iliac arteries, the right common iliac artery 102 and the left
common iliac artery 104. The right and left renal arteries 106, 108
and the right and left kidneys 110, 112 are located proximal from
the common iliacs 102, 104. In between the common iliacs and the
renal arteries, an aortic aneurysm 114 can be seen as a bulging
section of the abdominal aorta 100. Although not depicted in the
present figure, such an aneurysm may even extend down one or both
iliac arteries. The right and left common iliac arteries 102, 104
become the right and left femoral arteries 116, 118 in the region
of the pelvis 98.
[0073] A. Introducer Assembly
[0074] It is important to introduce the bifurcated aortic graft of
the present invention without causing damage to the patient's
vasculature, without undue loss of blood, without dislodging
plaque, and with minimum effort. It is a feature of the present
invention to utilize an "introducer assembly" to achieve these
objectives.
[0075] The "introducer assembly" of the present invention is
preferably configured for placement over a guidewire. Portions of
the introducer assembly are thereafter used to facilitate the
advancement of various catheter assemblies required in connection
with the practice of the invention as described below. An
introducer assembly useful in the practice of the present invention
is described in co-pending U.S. patent application Ser. No.
08/713,070 filed on Sep. 12, 1996, incorporated herein by reference
(the '070 Application).
[0076] The primary components of introducer assembly 130 may be
observed by reference to FIG. 3. FIG. 3 depicts a sheath assembly
132. Sheath assembly 132 is comprised generally of a sheath 134 and
a valve head 136. Sheath 134 is preferably cylindrical in shape
along those portions of its length to be inserted into a patient.
Sheath 134 is formed so as to have an appropriate flexibility and
an outer diameter suitable for placement at the location of an
aneurysm to be repaired. Sheath 134 is provided with a lumen having
a diameter suitable to permit insertion of the graft sections and
the various catheters described below. Tip portion 138 of sheath
134 is preferably curved so as to minimize any trauma to tissue or
tendency to dislodge plaque when the sheath is advanced upstream
into a patient's vasculature. As mentioned in the '070 application,
tip portion 138 is preferably fitted with a radiopaque marker to
assist in proper placement during use.
[0077] The femoral artery is a relatively high-pressure lumen.
Sheath 134 is fitted with valve head 136 in a fluid-tight fashion.
Valve head 136 permits insertion and removal of various catheters
during the method of the present invention without significant loss
of blood from the femoral artery.
[0078] FIG. 3 additionally illustrates a dilator 140 used initially
during the insertion of sheath 134 and during any subsequent
upstream movement of sheath 134. Dilator 140 is placed during use
through valve head 136 and sheath 134 so that tapered dilator tip
portion 142 protrudes from sheath tip portion 138. Dilator tip
portion 142 is formed of a somewhat resilient material that is
capable of being advanced gently through the tortured pathway of
the vasculature without causing undue trauma or a perforation. Yet,
it is desired that the tip portion be sufficiently stiff to cause
the blood vessels to assume a less tortuous path. In other words,
it is intended that the tip portion straighten the vasculature so
as to facilitate placement of the sheath. Dilator 140 is provided
with a lumen therethrough capable of fitting over a guidewire.
[0079] The proximal end of valve head 136 is provided with a
threaded connector 144. This threaded connector facilitates
fluid-tight connection of the valve head to other catheters during
the practice of the method of the invention, as discussed in
greater detail below.
[0080] The method for insertion of the introducer assembly will now
be described. As illustrated in FIGS. 8A and 8B, an incision 120 is
made and a primary guidewire 128 is placed in conventional fashion
in the right femoral artery 116 and right common iliac artery 102
so as to extend well upstream of the aneurysm 114.
[0081] As illustrated in FIGS. 3 and 9A, the introducer assembly
130 (comprising the sheath assembly 132 and the dilator 140) is
advanced over and along the primary guidewire 128. As the
introducer assembly is advanced, dilator tip portion 142 gently
straightens the patient's vasculature in preparation for sheath
134. As seen in FIG. 9B, the introducer assembly is advanced to the
point where tip portion 138 of the sheath 134 is upstream from the
desired site of graft placement. Specifically, the tip portion 138
is advanced upstream of one of the two renal arteries 106 and 108
located most proximal to the heart. Under fluoro-visualization, a
radiopaque marker 139 in sheath tip portion 138 confirms proper
placement with respect to the anatomical landmark of the renal
arteries.
[0082] Once the sheath has been properly placed, the dilator 140
(FIG. 3) is retracted along the guidewire and then completely
removed from within the sheath assembly 132 and from primary
guidewire 128. As illustrated in FIG. 9C, once the dilator 140 has
been removed, the lumen of sheath 134 is available for placement of
other catheters. Valve head 136 (FIG. 7A) prevents substantial
blood loss from sheath assembly 132.
[0083] B. Aortic Graft
[0084] The aortic graft is designed for introduction into the
abdominal aorta with the use of the main loading catheter, which
will be described in more detail below. First, the preferred
structure of the aortic graft will be described with reference to
FIG. 1.
[0085] As illustrated in FIG. 1, one presently preferred embodiment
of the aortic graft is designated generally at 10. Such a
bifurcated graft, sometimes referred to as a "trouser graft," is
adapted for insertion transfemorally to the situs of an aortic
aneurysm in the region where the iliac arteries branch from the
abdominal aorta.
[0086] The aortic graft 10 includes a proximal trunk portion 12 and
is bifurcated to define two proximal legs, a contralateral leg 14
and an ipsilateral leg 16. In this preferred embodiment, the
ipsilateral leg 16 extends longer than the contralateral leg 14 to
facilitate loading of both legs into a smaller diameter loader when
self expanding wireforms are attached to the end of each leg. The
length difference between the two legs corresponds to the height of
the self-expanding wireform, so that the self-expanding wireforms
are not side by side within the loader. This reduces the overall
bulk of the graft and permits loading into a smaller diameter
loader. One of skill in the art will appreciate, however, that the
relative lengths of the two graft legs may be adjusted depending on
the particular application for which the graft is to be used. This
difference in leg lengths also aids in orientation of the
bifurcated graft under fluoroscopy.
[0087] The aortic graft 10 is configured from a flexible tubular
structure 18 which is reinforced by wireforms 20 extending
circumferentially around or woven into the tubular structure 18.
The flexible tubular structure 18 is foldable, and the wireforms 20
are radially compressible and expandable. Thus, the graft is
configured to move between an insertion diameter, in which state
the graft may be inserted intraluminally into the aorta, and a
larger, expanded diameter (illustrated in FIG. 1) in which state
the graft may be secured within the aorta.
[0088] In the expanded state illustrated in FIG. 1, the trunk
portion 12 is generally cylindrical and has a trunk diameter 22
corresponding generally to the diameter of an average aorta. In
this preferred embodiment, the trunk portion 12 may be configured
to be a variety of sizes, one of which is selected according to the
size of the abdominal aorta of the patient into which the graft is
to be implanted. It is presently preferred to make grafts in which
the trunk portion is sized to an expansion diameter of 19, 21, 23,
25, 27, and 29 mm. These sizes, of course, are not limiting of the
sizes which may be utilized in accordance with the teachings of the
present invention.
[0089] As can readily be seen upon inspection of the graft of FIG.
1, the trunk portion 12 defines a cylindrical tube through which
fluid may flow. At a septum region 28, the graft bifurcates into
the two leg portions 14, 16. The cylindrical tubes defined by the
two leg portions are in fluid communication with the trunk portion
12, thereby approximating the internal configuration of the
bifurcated junction of the aortic artery. The legs 14, 16 are
cylindrical and have diameters which, in their expanded state,
correspond to a fixed diameter to insure a constant interface
between the legs and the upstream end of the extension grafts which
will be described later. In this embodiment, the contralateral leg
14 and the ipsilateral leg 16 have expanded diameters of 13 mm.
Again, the magnitude of the expanded diameter of the legs 14, 16
may be varied according to the desired interface between the legs
and the extension grafts. However the diameter of the legs is not
dependent on the diameter of the trunk region. In prior art
bifurcated woven grafts, the leg diameter is one half the diameter
of the trunk. For example, a 26 mm trunk would always bifurcate
into two 13 mm legs, a 28 mm graft would bifurcate into two 14 mm
legs, a 24 mm graft would bifurcate into two 12 mm legs, etc. This
is a function of how bifurcated grafts are typically woven.
[0090] In the present invention, the lower portion of the trunk
region can be tapered either out or in to insure a constant
diameter of the legs regardless of the trunk diameter. For example,
a 28 mm trunk would taper down to 26 mm in its lower region prior
to being bifurcated into two 13 mm legs. Similarly, a 24 mm trunk
would taper out to 26 mm prior to being bifurcated into two 13 mm
legs. This provides for a standard leg diameter regardless of the
trunk diameter and insures a constant interface and interlock
between the bifurcated graft and the extension grafts regardless of
the relative diameters of the trunk and the downstream ends of the
extension grafts.
[0091] An alternative embodiment of this invention would be to
maintain a straight trunk through the bifurcation region and then
taper the legs either out or in to maintain a constant downstream
diameter.
[0092] The flexible tubular structure 18 is preferably made of a
tube of woven polyester fabric. Although polyester is presently
preferred, other materials may be utilized for the flexible tubular
structure 18. Such materials include but are not limited to
expanded polytetrafluoroethylene (ePTFE), coated polyester, porous
polyurethane, silicone, and spun or woven polymeric fibers. One of
skill in the art of biocompatible grafts will readily identify
other materials suitable for application in the construction of the
flexible tubular structure 18. It is preferred that the tubular
structure be made of a material which is porous, thereby allowing
tissue ingrowth into the graft material and/or formation of an
intimal layer, although for some applications it may be desirable
to make the tubular structure of a fluid impervious material.
[0093] Preferably, the fabric is woven into the tubular
configuration, thereby eliminating seams or other internal
protrusions which could interfere with blood flow or form locations
for thrombi to occur. By employing a flexible fabric for the
tubular structure 18, the fabric will readily fold to accommodate
radial contraction of the graft, such as is necessary for
intraluminal introduction of the graft.
[0094] In a preferred embodiment of the present invention, the
fabric tubing of the graft and the wireforms therein can be
over-sized with respect to the first balloon used to expand the
balloon-expandable wireforms. Due to the fact that there is a small
amount of recoil that occurs in the balloon-expandable wireforms
after expansion, it may be desirable to re-expand these wireforms
to more accurately retain the graft within the vessel. If the
fabric tubing of the graft and the wireforms have a diameter which
is larger than the post-recoil diameter of the wireforms after
their first expansion, the physician can use a second, larger
balloon to re-expand or over-expand the balloon-expandable
wireforms such that upon recoil of the wireforms their diameters
are of the proper size for optimum retention of the graft within
the vessel.
[0095] This feature enables a surgeon to optimize the fit of a
graft within a vessel without having to remove it and replace it
with another. That is, a graft which upon first balloon-expansion
may not sufficiently engage with the wall of the vessel, may be
subsequently over-expanded to optimize the fit therein. For
example, the fabric tubing of the graft may have a diameter of 24
mm, while the balloon-expandable wireforms have a diameter of 24
mm. The graft is first inflated to 23 mm and the wireforms will
recoil to 22 mm. If the physician chooses to further expand the
wireforms and more optimally retain the graft in the vessel, the
physician will bring in a larger balloon which inflates to 25 mm.
After recoil, the final wireform diameter will be 24 mm and the
graft will be in its fully opened state.
[0096] In accordance with a presently preferred embodiment of the
invention, a number of wireforms 20 are provided to furnish
structural rigidity to the graft and to secure the graft within the
body lumen. As illustrated in FIG. 1, aortic graft 10 includes two
different types of wireforms: balloon-expandable wireforms 30 and
self-expanding wireforms 32. This preferred embodiment includes
three balloon expandable wireforms 34, 36, and 38, which are woven
into the fabric but positioned primarily on the interior of the
fabric in the trunk region 12 and a single balloon-expandable
wireform 40 positioned on the exterior of the fabric at the distal
end of the trunk region 12. A self-expanding wireform 42 is
attached to the outside of the fabric at the septum region 28 with
a self-expanding wireform 44 positioned on the distal end of the
contralateral leg 14 and another self-expanding wireform 46 at the
distal end of the ipsilateral leg 16.
[0097] The balloon-expandable wireforms 30 of the present invention
are preferably made of an alloy of carbon, silicon, phosphorus,
sulphur, chromium, nickel, beryllium, cobalt, iron, manganese and
molybdenum which is sold under the ELGILOY trade name by Elgiloy,
L.P. of Elgin, Ill., U.S.A. Other materials which may be utilized
in making the wireforms 30 include a nickel and titanium alloy sold
under the NITINOL trade name, stainless steel, and other
biocompatible, implantable metals. The wires used in manufacturing
the balloon-expandable wireforms 30 of the present invention are
preferably about 0.012 inches in diameter.
[0098] Preferably, each of the balloon-expandable wireforms 30 is
similarly configured with a curvilinear geometry such as the closed
sinusoidal-like wave geometry illustrated in FIG. 1, with
alternating crests 50 and valleys 52 which define an amplitude 54.
The amplitude 54 of a wireform is thus defined as the longitudinal
distance between a crest 50 and an adjacent valley 52. In this
preferred embodiment, the amplitude 54 of the proximal wireform 34
in its expanded state is approximately 0.103 inches.
[0099] The balloon-expandable wireforms 30 are preferably
configured with a plurality of intermediate segments 56 which are
connected by corresponding crests 50 and valleys 52. The crests 50
and valleys 52 are formed with a radius which, in this preferred
embodiment, is about 0.025 inches.
[0100] Preferably, the intermediate segments are positioned at an
angle with respect to each other of greater than about 90 degrees
in order to provide greater wireform rigidity, reduced wireform
recoil and increased anchoring force. To those ends the
intermediate segments are more preferably positioned at an angle
with respect to each other from a range of about 100 degrees to
about 135 degrees. Most preferably, the intermediate segments are
positioned at an angle with respect to each other from a range of
about 120 degrees to about 125 degrees.
[0101] For example, in the most preferred embodiment, the crests 50
and valleys 52 of the balloon-expandable wireforms 30 are
configured by obtaining annealed ELGILOY wire having a diameter of
preferably about 0.012 inches and wrapping the wire around a pin
having a diameter of 0.050 inches, thereby defining a plurality of
adjacent, intermediate segments 56 positioned at an angle with
respect to each other of from about 120 to 125 degrees. Thus, the
amplitude of the intermediate segments 56 of the proximal wireform
34 in its expanded state (i.e., excluding the radius which defines
the crests and valleys) is about 0.103 inches. In this presently
preferred embodiment, each balloon-expandable wireform 40 has eight
crests 50.
[0102] An alternative method for constructing the
balloon-expandable wireforms 30 is to configure the wireforms in a
true sinusoidal-like pattern. By constructing the wireforms 30
according to this alternative method, the angle between adjacent
intermediate portions is about 120 to 125 degrees, thereby
maintaining the number of crests on the wireform to eight.
Alternatively, the balloon-expandable wireforms are configured such
that they are continuously curvilinear as illustrated by FIG. 1B.
This continuously curvilinear shape 48 primarily serves to reduce
stress on the wireforms when the aortic graft is in its first,
compressed state. One of skill in the art will be familiar with
other methods for manufacturing balloon-expandable wireforms
without departing from the teachings of the present invention.
[0103] Because the wire has been annealed, it will readily
plastically deform to maintain its configuration. Thus, the
wireform may be plastically deformed between the radially collapsed
position and the radially expanded position of FIG. 1. The
wireforms are, therefore, not resilient to any substantial extent,
requiring them to be physically expanded into contact with the
internal wall of the aorta via a force other than their own
resilience. Further, there is some amount of recoil after
balloon-expansion of the wireforms, which will be discussed in more
detail below.
[0104] The balloon-expandable wireforms 34, 36, and 38 which are
positioned along the proximal portion of the trunk 12 of the graft
are preferably secured to the fabric graft material by weaving the
wireform through the fabric material. The wire is woven through the
fabric such that the distal tip of the valley of each wireform
extends through the graft and is positioned on the outside of the
fabric structure 18. The weaving is accomplished by initially
configuring an elongated piece of wire into the predetermined
curvilinear configuration. With the wire so configured, it may be
manually woven through the fabric structure 18 until the wire
extends around the entire circumference of the fabric structure 18.
The wire is woven such that it is primarily positioned along the
interior of the fabric tube, with only small segments of wire
exposed to the outside of the tube.
[0105] The wireform is woven into the fabric tube such that when
the wire extends around the entire periphery of the fabric tube,
the free ends of the wire protrude from the tube at positions
adjacent to each other, thereby enabling a tail segment 62 to be
defined by the free ends. The loose ends are preferably held
together with a crimping sleeve 64 positioned over them. After
crimping the sleeve to secure the ends to each other and thereby
complete the circular configuration of the wireform, any portion of
the wires extending beyond the ends of the sleeve may be trimmed to
cleanly finish the tail segment 62. It is preferable that no
portion of the wire extend beyond the edge of the crimping sleeve
to eliminate the possibility of the wire cutting or piercing the
lumen wall.
[0106] As illustrated in FIG. 1, the tail segments are positioned
on the outside of the fabric layer 18 and extend below the
longitudinal position of the other valleys 52 of the wireform.
Thus, the most proximal wireform 34 of FIG. 1 includes a tail
segment 62 extending in the distal direction below the level of
adjacent valleys 52. Although this configuration is preferred, one
of skill in the art will appreciate that the wireforms 30 may be
formed in two parts with two tails positioned on opposite sides of
the graft.
[0107] The tail segments 62 of the balloon-expandable wireforms 30
are preferably configured to extend substantially flat against the
fabric layer 18, i.e., substantially parallel to the longitudinal
axis 60 of the graft. With the tail segments so configured, the
risk that the tail segments will penetrate or damage the wall of a
lumen with which it comes into contact will be substantially
reduced.
[0108] The proximal wireform 34 is positioned with respect to the
upper edge of the fabric layer such that approximately one-third of
the wireform extends beyond the edge of the fabric layer. The
wireform is positioned to extend above the edge of the fabric layer
to prevent any portion of the fabric layer from oscillating, or
"flapping," in response to the flow of blood past the edge of the
graft. As an additional measure to prevent such fabric oscillation
in the blood stream, the edge of the fabric is configured with
V-shaped notches corresponding generally to the valleys 52 of the
proximal wireform 34. Thus, the risk of the existence of any loose
fabric which could potentially be affected by the passing flow of
blood is substantially reduced.
[0109] In an alternate embodiment of the present invention, the
proximal-most balloon-expandable wireform is preferably configured
to have a diameter in its expanded state which is slightly larger
than that of the portion of the fabric tubular structure into which
it is weaved. Thus, in the illustrated embodiment in which the
proximal opening of the fabric portion of the graft has a diameter
of 22 mm, the proximal wireform 34 is configured with a diameter of
24 mm. By configuring the wireform to be slightly larger than the
fabric into which it is woven, the fabric will be maintained in a
constant state of slight tension upon expansion of the wireform,
thereby reducing the possibility of the fabric folding or
oscillating in response to blood flow through the graft.
[0110] Wireforms 36, 38 are positioned adjacent the proximal
wireform 34 and are spaced apart from each other such that the
wireforms do not interfere with each other in either a radially
expanded or contracted state. Thus, for example, in a preferred
embodiment the valleys of wireform 34 are located proximal of the
crests of wireform 36. The wireforms 34, 36, 38 are also aligned
"in phase," with peaks along one longitudinal line and adjacent
valleys aligned along a second longitudinal line, thereby further
reducing the possibility of overlap of adjacent wireforms. (While
there may be some overlapping of the tail segments 62 with an
adjacent wireform, because the tail segments extend on the outside
of the fabric layer and the adjacent wireform is primarily on the
inside of the fabric layer, a small degree of overlap with an
adjacent wireform does not pose a problem.)
[0111] In addition, adjacent balloon-expandable wireforms are not
connected to one another. This coupled with the in-phase
configuration of the wireforms maximizes flexibility of the aortic
graft without permitting deleterious kinking, which is of primary
importance in the often tortuous paths of the abdominal aorta and
iliac arteries.
[0112] The proximal three wireforms 34, 36, 38 are preferably
positioned as close to each other as possible without overlapping.
In this embodiment, the wireforms 34, 36, 38 are positioned along
the length of the graft about every 4.0 mm. By minimizing the space
between the proximal three wireforms 34, 36, 38, the force exerted
against the wall of the body lumen is enhanced. Thus, to the extent
that the lumen surrounding these three wireforms is healthy and not
expanded due to the aneurysm, the wireforms 34, 36, 38 will all
assist in achieving a frictional interface with the proximal end of
the graft in the lumen.
[0113] The distal balloon-expandable wireform 40 is configured
similarly to the other balloon-expandable wireforms 34, 36, and 38
in that all are generally circular in cross section.
[0114] The distal balloon-expandable wireform 40 is attached to the
fabric structure 18 in a different manner from the other
balloon-expandable wireforms. Instead of being woven into the
fabric structure 18, distal wireform 40 is attached to the fabric
by tying it to the fabric with polyester thread. Other
biocompatible threads may also be employed for securing the distal
wireform 40 to the fabric tubular structure 18. In this preferred
embodiment, each crest 50 of distal wireform 40 is secured to the
fabric. Each intermediate segment 56 of distal wireform 40 is also
preferably tied to the fabric at a point approximately midway
between the crest 50 and an adjacent valley 52. Although in this
preferred embodiment, wireform 40 is tied to the fabric structure
with a thread, one of skill in the art will readily identify other
attachment methods. Adhesives, for example, may be successfully
employed in accordance with the teachings of the present
invention.
[0115] Distal wireform 40 is preferably positioned in the
transition region 66 to aid in keeping the graft open. In this
preferred embodiment, the distal wireform 40 is located
approximately 15 mm below the proximally adjacent wireform 38. By
positioning the distal wireform 40 in the transition region 66, it
will generally be located within the aneurysmic sack when the graft
is properly implanted within the lumen of a patient. Consequently,
the distal wireform 40 will not engage the wall of the lumen and
serves only to provide structural rigidity to maintain the graft
open at the transition region 66. Thus, it is preferable that the
distal wireform 40 be positioned along the outside of the fabric
structure whereas the other balloon-expandable wireforms are
primarily located inside of the fabric structure. With the wireform
40 on the outside of the fabric structure, the wireform does not
interfere with blood flow through the graft. In addition, it can
not be inadvertently snagged from the inside as modular components
are introduced into the lumen of the bifurcated graft.
[0116] In addition to the balloon-expandable wireforms 30 discussed
above, the graft 10 of the present invention also includes a number
of self-expanding wireforms 32. The configuration of each of the
self-expanding wireforms 32 is naturally biased towards an expanded
state, such as that illustrated in FIG. 1. The self-expanding
wireforms 32 may be made of the same base material used in the
construction of the balloon-expandable wireforms 30, although the
method of manufacturing may differ. Thus, ELGILOY wire is
preferred, with a number of other materials acceptable for such
use. As illustrated in FIG. 1, the self-expanding wireforms 32
employed in the graft 10 of the present invention have a generally
curvilinear configuration having loops which define crests 70 and
valleys 72. Further, the intermediate sections 74 are not straight,
but have an "S" shape along their length.
[0117] The self-expanding wireforms 32 are constructed by obtaining
cold worked ELGILOY wire having a diameter of preferably about
0.012 inches and wrapping it around a cylindrical form 78, such as
that illustrated in FIG. 1A, having primary pins 80 positioned to
form the loops which define the crests 70 and valleys 72 of the
wireform. Two secondary pins 82 are positioned adjacent each
primary pin 80 to aid in defining the loops and configuring the "S"
shape in the intermediate region 74 of the wireform.
[0118] The wireform is thus positioned about the entire
circumference of the form 78 and the ends may be fitted with a
crimping sleeve while positioned in an overlapping configuration.
With the wireform thus configured on the form 78, the wireform and
form are placed in an oven heated to about 500 degrees centigrade
for about 3.5 to about 5.0 hours. By thus heat treating the
self-expanding wireform 32, the wireform will develop a memory
corresponding to the shape in which it is positioned on the form.
Thus, the wireform may be elastically deformed, such as by radially
compressing the wireform for intraluminal insertion into a patient,
and, when released, will resiliently return to the shape it had
during the heat treatment.
[0119] As an alternative method for constructing the self-expanding
wireforms 32 of the present invention. a form comprising a flat
surface (not illustrated) with a similar pin configuration may be
utilized. After heat treating the wireform, the ends of the
wireform may be attached, thereby forming the wireform into its
cylindrical configuration, according to any of those methods
described above.
[0120] As the self-expanding wireforms resiliently move between
their expanded and contracted positions, tension is applied to the
outer portion of the resulting wireform loop and a corresponding
compression results on the inner portion of the wireform loop.
Thus, the pins 80, 82 of the form 78 are selected to have a radius
such that the resulting tension and compression on the loop stay
below the yield point of the wire. It has been found that for the
preferred embodiment of the self-expanding wireforms 32 illustrated
in FIG. 1, a pin diameter of about 0.070 inches is satisfactory and
presently preferred.
[0121] The self-expanding wireforms 32 are advantageously
configured such that the intermediate regions 74 of the wireforms
are in an "S" shape. As the wireform moves between its expanded and
contracted positions, the elastic deformation which occurs to
accommodate such movement is spread substantially evenly throughout
the entire length of the wireform. Consequently, the entire length
of the wireform acts as a spring to help restore the wireform to
its original configuration after radial compression. Thus, the
elastic deformation is not concentrated solely in the loops
defining the crests and valleys of the wireform, but is also
absorbed by the intermediate segments. This reduces the potential
for exceeding the yield point of the wire at the crest and valleys
of the wireform, which would cause plastic deformation and prevent
the wireform from functioning as intended.
[0122] With the self-expanding wireforms 32 formed according to one
of the methods described above, they may be attached to the fabric
tubular structure 18 of the graft 11. Attachment of the
self-expanding wireforms 32 is preferably accomplished by tying the
crests 70 and valleys 72 to the fabric, as illustrated in FIG. 1.
It is presently preferred that each crest and valley be tied in
five separate locations around the perimeter of the loop defining
the respective crest or valley.
[0123] The self-expanding wireforms 32 are designed to have an
initial expanded diameter which is slightly larger than the
diameter of that portion of the graft where they are to be
positioned. It is presently preferred that the wireform be about
2.0 mm larger in diameter than the cross section of fabric to which
it is attached. By configuring the wireform with such a relative
diameter, the self-expanding wireforms 32, when fully expanded,
maintain the fabric structure to which they are attached in a state
of slight tension, thereby ensuring that the fabric structure
(defining the artificial lumen) is fully open.
[0124] Further, the distal self-expandable wireforms exert a
radially inward force against the balloon-expandable portions of
the graft extensions engaged therewith, as will be described in
more detail below with respect to the discussion of placement of
the graft extensions.
[0125] When designing the wireform, it must also be recognized that
the wireform will lose about five percent of its recoil ability
after being radially compressed into its state of reduced diameter
and subsequently expanded. Thus, for a wireform which is to be
positioned at the distal end of either the 13 mm diameter
contralateral leg 14 or ipsilateral leg 16, the wireform will
initially be designed to have a diameter of about 15.7 mm. After
the wireform has been radially compressed and subsequently expanded
in a body lumen, it will expand to a diameter of about 14.5
mm--slightly larger than the 13 mm fabric lumen provided at the
leg, as desired.
[0126] The most proximal self-expanding wireform 42 is positioned
at the septum region 28 of the graft. Wireform 42 thus acts to
maintain the septum region 28 of the graft open as blood flows
through the graft. In this preferred embodiment, the proximal
self-expanding wireform 42 is located about 6 to 10 mm distal of
the adjacent balloon-expandable wireform 40.
[0127] As illustrated in FIG. 1, at the septum region 28 of the
aortic graft, the ends of self-expanding septum wireform 42 are
secured in crimping sleeves 84, 85. These crimping sleeves are of
an outer diameter such that they provide a second function as
radiopaque markers. It has been found that for the preferred
embodiment of the crimps 84, 85 illustrated in FIG. 1, an outer
diameter of at least 0.036 inches is satisfactory and presently
preferred. The configuration of these crimping sleeves aids in
proper orientation of the aortic graft and confirmation of the
location of the septum within the abdominal aorta. The wireform 44
on contralateral leg 14 and wireform 46 on ipsilateral leg 16,
similarly include crimping sleeve 86.
[0128] Each of the self-expanding wireforms 32 is positioned
exteriorly of the fabric tubular structure 18, thereby avoiding
interference with blood flow within the graft, and preventing the
wireforms from being inadvertently snagged from the inside as
modular components are introduced into the lumen of the bifurcated
graft. Additionally, the attachment of graft extensions to
contralateral leg 14 and ipsilateral leg 16 (explained below) is
facilitated by having the wireform positioned on the outside
portion of the fabric leg.
[0129] The graft 10 is further configured with laterally extending
reinforcement wires 90, disposed on each leg 14, 16. The wires 90
are preferably made of the same base material as the wireforms. The
wires 90 are positioned on each leg 14, 16 and extend generally
from a valley 72 on wireform 42 to a corresponding crest 70 on a
respective one of wireforms 44 and 46. As illustrated in FIG. 1,
the reinforcement wires 90 are tied onto the fabric structure 18 in
a similar manner as are wireforms 32, taking care that the wire 90
does not longitudinally cross into any of the wireforms. The
reinforcement wire 90 keeps the legs of the wireform from folding
or buckling.
[0130] These two longitudinal wireforms 90 are also provided with
radiopaque crimps 91 which assist in the placement of the extension
grafts within legs 14 and 16.
[0131] C. Main Catheter Assembly
[0132] The main catheter assembly is utilized to place the aortic
graft described above, which is compressed and loaded onto the
distal end of the main catheter assembly as will be described in
more detail below. A main catheter assembly useful in the practice
of the present invention is described in co-pending U.S. patent
application Ser. No. 08/713,070 filed on Sep. 12, 1996, previously
incorporated herein by reference hereinabove (the '070
Application).
[0133] The sheath assembly 132 is utilized to facilitate the
operative placement of the main catheter assembly. As such, the
main catheter assembly is sized such that it will fit inside the
introducer sheath 134.
[0134] The primary components of the main catheter assembly 180 may
be observed by reference to FIGS. 4 and 6. The catheter assembly of
the present invention comprises a rigid loader 200 which is used to
facilitate the operative coupling of the catheter assembly to the
introducer assembly during use of the present endovascular delivery
system, as will be described in more detail with reference to FIGS.
9B and 9C. The loader comprises an elongate tube 202 including a
lumen, a proximal end, and a distal end which is defined by a
reduced diameter distal section. An internally threaded connector
nut 204 is attached to the distal portion of the elongate tube.
[0135] The catheter assembly is cooperatively engaged and secured
to the head of the introducer sheath assembly by initially
inserting the distal section of the loader into the valve head of
the sheath assembly subsequent to the removal of the dilator from
therewithin. FIG. 7A illustrates insertion of the main catheter
assembly into the valve head of the sheath assembly. More
particularly, the distal section of the loader 200 is extended into
the threaded connector 144 of the valve head 136 with the connector
nut being threadably engaged to the externally threaded proximal
portion of the threaded connector 144. FIG. 7B illustrates the
connector nut 204 connected to the valve head 136 of the sheath
assembly 132.
[0136] The loader and corresponding receiving portion of the valve
head are preferably formed of rigid material such that the loader
will seat correctly within the interfacing portion of the valve
head without flexing or distortion thereof. This ensures proper
positioning and registry of the loader and the valve head relative
to each other. Furthermore. the ability of the loader to be
positively engaged, that is, locked by threadable engagement of the
nut to the valve head of the introducer assembly, also facilitates
and maintains proper registry and positioning of the loader
relative to the introducer assembly.
[0137] The catheter assembly of the present invention further
includes a proximal connector assembly 206 (FIGS. 4 and 6). The
proximal connector assembly includes a pusher connector 182, which
is preferably a Y-connector. The proximal connector assembly 206
further includes a tubular body 210 having a lumen extending
longitudinally therethrough that is ultimately in fluid
communication with the interior of the balloon 194. A tubular side
arm 214, which communicates with the lumen of the tubular body, is
connected to the tubular body and extends angularly therefrom. A
stopcock 218 on the end of the tubular side arm 214 permits valving
of the balloon inflation lumen. The proximal connector additionally
comprises a Y-connector 208 and a contrast connector 212.
[0138] The main catheter assembly 180 further comprises an
elongate, tubular pusher body 184. The pusher body 184 includes a
distal end 186, a proximal end 188, and a lumen extending
longitudinally therethrough. The outer diameter of the distal
section slightly exceeds that of the remainder of the pusher body.
The proximal end 188 is operatively connected to the pusher
connector 182, which along with the pusher body, will expel the
loaded aortic graft to leave it in place within the aorta as will
be described in more detail below with respect to the preferred
method of the present invention.
[0139] The main catheter assembly of the present invention further
comprises an elongate catheter with a coaxial tube construction. As
illustrated in FIG. 6, the elongate coaxial tube catheter comprises
an elongate outer tube 190 and an elongate inner tube 192. The
outer catheter defines a distal end, a proximal end, and hollow
lumen extending longitudinally therethrough. The inner tube is
smaller in diameter than the outer tube and extends through the
lumen thereof. The inner tube defines a distal end, a proximal end,
and hollow lumen extending longitudinally therethrough. The inner
tube is slidably extensible distally and retractable proximally
relative to the outer tube.
[0140] The main catheter assembly further comprises an elongate,
inflatable catheter balloon 194, illustrated in its inflated
configuration in FIG. 6. This inflatable balloon serves to expand
the balloon-expandable reinforcement wires of the aortic graft.
When fully inflated, the balloon of the catheter assembly has a
generally uniform, cylindrical configuration.
[0141] The balloon includes a distal end which is attached to a
tubular sleeve portion 196 of the inner tube 192, and a proximal
end which is attached to the outer tube 190. In turn, the extension
of the inner tube distally relative to the outer tube facilitates
the longitudinal stretching of the balloon. The catheter also
includes a spacer clip 198 which allows the balloon to be extended
or lengthened after deflation thereof to facilitate withdrawal of
the balloon and catheter from the expanded aortic graft. The inner
tube is initially oriented in a first retracted position relative
to the outer tube. The balloon is inflated only when the inner tube
is in its retracted orientation.
[0142] Subsequent to being deflated, the balloon is preferably
stretched longitudinally by the distal advancement of the inner
tube of the catheter relative to the outer tube thereof. More
particularly, the inner tube is moved from its first, retracted
position to its second extended position. The movement of the inner
tube from its retracted position to its extended position to
stretch the balloon is facilitated by tightly grasping the balloon
and contrast connectors of the proximal connector assembly, and
subsequently pushing the contrast connector distally toward the
balloon connector. Since the outer tube is rigidly attached to the
balloon connector and the inner tube is rigidly attached to the
contrast connector via the sheath, movement of the contrast
connector toward the balloon connector results in a slideable
advancement of the inner tube distally within the outer tube. As a
result, the attachment of the spacer clip to the exposed portion of
the sheath prevents the contrast connector from being moved
distally toward the balloon connector. While the spacer clip is in
its operative position upon the sheath, the balloon cannot be
longitudinally stretched in that the inner tube is prevented from
moving from its first, retracted position to its second, extended
position. Once the spacer clip is detached from the sheath, the
balloon and contrast connectors are no longer maintained in spaced
relation to each other so that the contrast connector can be pushed
distally toward the balloon connector, thereby facilitating the
distal advancement of the inner tube to its extended position and
the resultant stretching of the deflated balloon.
[0143] The downstream end of the graft ipsilateral leg is trapped
between the distal section of the pusher body and the balloon
catheter shaft. This facilitates reorientation of the graft during
deployment, if desired.
[0144] D. Main Graft Deployment
[0145] The method for using the main catheter assembly following
the withdrawal of the dilator from within the sheath assembly will
now be described. Initially, with reference to FIG. 10A, the main
catheter assembly 180 is inserted over the primary guidewire 128
and into the sheath assembly 132. The distal connector nut 204 is
connected to the threaded sleeve portion of the valve head 136.
[0146] With reference to FIGS. 10A and 10B, the main catheter is
then advanced over the guidewire 128 and within the sheath 134 such
that the distal-most portion extends from the sheath tip portion
138, and above the renal arteries 106, 108. To accomplish this, the
pusher body 184 (FIG. 4) is distally advanced through the lumen of
the introducer sheath 134 until such time as the collapsed graft 10
protrudes from the distal end of the sheath 138. More specifically,
as seen in FIG. 10B, the distal end 194a of balloon 194 and the
inner catheter 192 protrude from the sheath 134. The precise
positioning of the main catheter in this manner is facilitated by
observing under fluoroscopy the relative positions of a contrast
marker associated with the balloon distal end 194a and the
radiopaque marker 139 in sheath tip portion 138. The two radiopaque
markers 139, 194a are brought together, with the combination being
relatively located with respect to the renal arteries.
[0147] The position of the sheath 134 across the aneurysm 114
permits the shielded introduction of the main catheter with balloon
194 and graft 10 thereon into the proper implantation position. In
other words, the surrounding sheath 134 shields the advancing
catheter and the otherwise expanded and irregularly shaped graft 10
from blood flow resistance. Moreover, the sheath 134 protects the
graft assembly from contacting the vessel walls to prevent
potential snags. In short, the initial positioning of the sheath
upstream of the location at which the graft will be finally
implanted ensures that the expanded graft will only have to be
displaced downstream into its final location, which is in the
direction of blood flow and thus this operation is substantially
easier to effectuate and is also less prone to inflict damage on
the vessel walls.
[0148] Once the graft 10, still within the sheath 134, is
positioned upstream from its final location the sheath is removed.
FIGS. 10C and 10D illustrate this operation. To accomplish this,
the pusher body 184 (FIG. 4) is held stationary as the sheath 134
is withdrawn from the main catheter to a position just downstream
from the graft 10. Desirably, as seen in FIG. 10D, the sheath 134
is withdrawn so that the tip portion 138 is just downstream from
the longer of the contralateral leg 14 or ipsalateral leg 16. In
the case of an enlarged aneurysm 114 as shown, the tip portion 138
will still be within the aneurysm. As the introducer sheath
assembly is withdrawn, the self-expanding wireforms 42, 44, &
46 (FIG. 1) in the aortic graft expand within the aneurysm sack,
while the balloon-expandable wireforms 30 maintain a substantially
compressed configuration.
[0149] A final step of positioning of the graft 10 may be required.
That is, removal of the sheath 134 from over the graft 10, as seen
in FIG. 10C, may leave the distal end of the graft (and distal end
of balloon 194a) upstream of the renal arteries 106, 108. (In some
instances, removal of the sheath 134 will, by friction, pull the
main catheter and graft 10 along with it, though the surgeon is
instructed to maintain the catheter position with the pusher body
184. In this respect, the initial positioning of the distal end of
the entire assembly upstream of the renal arteries is intended to
provide some margin for downstream movement of the catheter). If
the contrast marker at the balloon distal end 194a remains upstream
of or adjacent to the renal arteries 106, 108, the main catheter is
then withdrawn further downstream to reposition the balloon distal
end just downstream of the renal arteries. This final position is
seen in FIG. 10D. The inflation balloon 194 can be seen in outline
inside of the aortic graft 10. The final displacement of the
expanded graft 10 downstream is with the blood flow and thus does
not require much force.
[0150] As seen in FIG. 10D, the graft 10 is sized such that the
distal end (as carried on the catheter) thereof protrudes beyond
the upstream boundary of the aortic aneurysm and into unaffected
region of the abdominal aorta 100. Locating the distal end of the
graft 10 just below (downstream from) the renal arteries 106, 108
ensures the maximum length of contact between the eventually
expanded graft 10 and the unaffected abdominal aortic wall. The
contralateral leg 14 and ipsalateral leg 16 of the graft 10 extend
into the aneurysm 114, and, as will be detailed below, extensions
thereto are used to continue their respective lumens at least to
the unaffected regions of the iliac arteries 102, 104.
[0151] As seen in FIGS. 11A and 11B, the balloon 194 is then
inflated via the balloon connector. The inflation/pressurization of
the balloon causes radial expansion of the trunk portion 12 of the
graft 10 from its initial, collapsed orientation, to its second,
expanded orientation. Due to the configuration of the balloon when
fully inflated, the radial expansion of the trunk portion 12 to its
second, expanded orientation is uniform. In this respect, the
expansion forces applied to the opposed ends of the trunk portion
12 by the balloon are equal to those applied to the remainder
thereof. This uniform application of expansion forces to the trunk
portion 12 facilitates the tight engagement of the opposed ends
thereof to the luminal surface of the aorta. Preferably, the
balloon is inflated for 30 seconds to a pressure of about 2
atmospheres. FIG. 11A, for example, illustrates inflated balloon
194 within the expanded aortic graft 10 (in outline). Further, as
illustrated in more detail in FIG. 11B, balloon 194 may be slightly
over-sized (represented by the arrows pointing outwardly from the
balloon) to force aortic graft 10 into optimal engagement with the
aortic wall, especially given the tendency of the wireforms to
recoil inwardly slightly after expansion. When the graft is fully
expanded, the opposed ends thereof frictionally engage the luminal
surfaces of unaffected regions of the aorta.
[0152] After the graft has been radially expanded in the
aforementioned manner the balloon is deflated and removed from
within the sheath 134. As illustrated in FIG. 12A, the balloon 194
is deflated and the stopcock 218 is left open to room air to
equalize negative pressure. When the balloon 194 is deflated it may
not return to its initial, uninflated orientation due to rigidity
of the balloon material. Rather, the diameter of the main body
portion of the deflated balloon may remain substantially the same
as when the balloon is fully inflated, or may otherwise continue to
protrude in a manner that could complicate subsequent retraction
and removal of the delivery catheter.
[0153] To prevent the deflated balloon 194 from inadvertently
catching on or interfering with the radially expanded graft 10
during the withdrawal of the balloon from within, the balloon is
longitudinally stretched prior to the withdrawal of the main
catheter from within the graft as seen in FIG. 12B. As previously
explained, such stretching of the deflated balloon is accomplished
by distally advancing the inner tube 192 of the main catheter
relative to the outer tube 190 thereof Such movement of the inner
tube is facilitated by tightly grasping the balloon and contrast
connectors of the proximal connector assembly with the spacer clip
removed, and subsequently pushing the contrast connector distally
toward the balloon connector, which pushes the distal end of the
balloon in the direction indicated by the arrow 216 in FIG. 12B. A
vacuum may be pulled through stopcock 218 to completely deflate the
balloon 194.
[0154] The main catheter with the now deflated and stretched
balloon 194 is then withdrawn slowly and carefully from the aortic
graft and into the introducer sheath as illustrated in FIG. 12C.
Once the main catheter assembly has been proximally retracted into
the introducer sheath 134, it is withdrawn from within the
patient's body as indicated by arrow 217. The aortic graft 10
remains in place within the abdominal aorta with the introducer
sheath 134 still in position just downstream thereof, and the
primary guidewire 128 extending therethrough. It should be noted
that the blood flow down the abdominal artery 100 now flows
completely through the graft 10; that is, through the trunk 12 and
two legs 14 and 16. Attachment of the extensions inside the legs
must adapt to this flow, as will be described below.
[0155] E. Extension Grafts
[0156] As previously described hereinabove, the downstream end of
the aortic graft 10 is bifurcated with a septum region 28
separating the ipsilateral leg 16 from the contralateral leg 14.
Two additional graft portions are adapted to extend into the
respective iliac arteries and to form a frictional engagement with
the ipsilateral and contralateral legs of the aortic graft.
[0157] These extension grafts typically comprise straight or
tapered cylindrical tubes, with an upstream end having a common
diameter, while the diameter of the downstream ends can vary
depending on the anatomy of the patient. The upstream ends
interlock with the respective downstream portions of the aortic
graft. By fixing the diameter of the upstream ends of the extension
graft and the downstream ends of the bifurcated aortic graft, a
consistent interface and interlock can be achieved regardless of
the patients anatomy. The diameter of the downstream end of the
graft extensions can be provided in varying diameters so as to suit
the diameter of the iliac artery into which graft portions are
being implanted. The change in diameter can be provided by a short
step-down portion or a step-up portion or by a region of taper
extending along a length of the graft portion.
[0158] Turning now to FIG. 2, one preferred embodiment of a graft
extension 170 is depicted. The graft extension comprises an
upstream portion 172, a downstream portion 174, and a lumen running
the length thereof.
[0159] In a preferred embodiment the graft extension 170 is
configured from a flexible tubular 175 structure which is
reinforced by wireforms 176 extending circumferentially around the
tubular structure. The flexible tubular structure is foldable and
the wireforms are radially compressible and expandable. Thus, the
extension graft is configured to move between an insertion
diameter, in which state the graft may be inserted through a
femoral and iliac artery and into one of the bifurcated legs of the
aortic graft, and a larger, expanded diameter (illustrated in FIG.
2) in which state the graft may be secured within the aortic
graft.
[0160] In the expanded state illustrated in FIG. 2, the extension
graft 170 is generally cylindrical and may be configured to be a
variety of sizes, one of which is selected according to the size of
the iliac artery of the patient into which the extension graft is
to be implanted.
[0161] The flexible tubular structure 175 is preferably made of a
tube of woven polyester fabric. Although polyester is presently
preferred, other materials may be utilized for the flexible tubular
structure 175. Such materials include but are not limited to
expanded polytetrafluoroethylene (ePTFE), coated polyester, porous
polyurethane, silicone, and spun or woven polymeric fibers. One of
skill in the art of biocompatible grafts will readily identify
other materials suitable for application in the construction of the
flexible tubular structure 175. It is preferred that the tubular
structure be made of a material which is porous, thereby allowing
tissue ingrowth into the graft material and/or formation of an
intimal layer, although for some applications it may be desirable
to make the tubular structure of a fluid impervious material.
[0162] Preferably, the fabric is woven into the tubular
configuration, thereby eliminating seams or other internal
protrusions which could interfere with blood flow or form locations
for thrombi to occur. By employing a flexible fabric for the
tubular structure, the fabric will readily fold to accommodate
radial contraction of the graft, such as is necessary for
intraluminal introduction of the graft.
[0163] In one preferred embodiment of the present invention, the
diameter of the fabric tubing of the graft is over-sized with
respect to the wire-forms therewithin. Upon balloon-expansion of
the balloon-expandable wireforms, there is a small amount of recoil
that occurs in the wireforms. The fabric tubing of the graft
therefore can have a diameter which is larger than the post-recoil
diameter of the wireforms. In turn, the wireforms can be
over-expanded with a second balloon of a different size such that
upon recoil, the diameter of the wireforms is of the proper size
for optimum retention of the graft within the vessel. This feature
enables a surgeon to optimize the fit of a graft within a vessel
without having to remove a too-small graft and replace it with
another. That is, a graft which upon first balloon-expansion may
not sufficiently engage with wall of vessel, may be subsequently
over-expanded by a second balloon of a larger size to optimize the
fit therein.
[0164] In accordance with a presently preferred embodiment of the
invention, a number of balloon-expandable wireforms 176 are
provided to furnish structural rigidity to the graft and to secure
the graft within the body lumen. Each of the balloon-expandable
wireforms is similarly configured with a curvilinear geometry such
as the closed sinusoidal-like wave geometry illustrated in FIG. 2A,
with alternating crests 150 and valleys 152 which define an
amplitude 154. The amplitude 154 of a wireform is thus defined as
the longitudinal distance between a crest 150 and an adjacent
valley 152.
[0165] Alternatively, the balloon-expandable wireforms are
configured such that they are continuously curvilinear, such as the
configuration of the wireform illustrated by FIG. 1B. As noted
above, this continuously curvilinear shape 48 reduces stress on the
wireforms when the graft is in its first, compressed state.
[0166] An alternative method for constructing the
balloon-expandable wireforms is to configure the wireforms in a
true sinusoidal pattern. One of skill in the art will be familiar
with other methods for manufacturing balloon-expandable wireforms
without departing from the teachings of the present invention.
[0167] The balloon-expandable wireforms 176 are preferably
configured with a plurality of intermediate segments 156 which are
connected by corresponding crests 150 and valleys 152. The crests
150 and valleys 152 are formed with a radius which, in this
preferred embodiment, is about 0.025 inches.
[0168] Preferably, the intermediate segments are positioned at an
angle with respect to each other of greater than about 90 degrees
in order to provide greater wireform rigidity, reduced wireform
recoil, and increased anchoring force. To those ends the
intermediate segments are more preferably positioned at an angle
with respect to each other from a range of about 100 degrees to
about 135 degrees. Most preferably, the intermediate segments are
positioned at an angle with respect to each other from a range of
about 120 degrees to about 125 degrees.
[0169] The balloon-expandable wireforms 176 of the present
invention are preferably made of an alloy of carbon, silicon,
phosphorus, sulphur, chromium, nickel, beryllium, cobalt, iron,
manganese and molybdenum which is sold under the ELGILOY trade name
by Elgiloy, L.P. of Elgin, Ill., U.S.A. Other materials which may
be utilized in making the wireforms include a nickel-titanium shape
memory alloy sold under the NITINOL trade name, stainless steel,
and other biocompatible, implantable metals. The wires used in
manufacturing the balloon-expandable wireforms of the present
invention are preferably about 0.012 inches in diameter.
[0170] Because the wire has been annealed, it will readily
plastically deform to maintain its configuration. Thus, the
wireform may be plastically deformed between the radially collapsed
position and the radially expanded position of FIG. 2. The
wireforms are, therefore, not resilient to any substantial extent,
requiring them to be physically expanded into contact with the
internal wall of the iliac artery and downstream legs of the aortic
graft via an external force rather than expanding by virtue of
their own resilience.
[0171] The balloon-expandable wireforms which are positioned along
the graft extension are preferably secured to the fabric graft
material by weaving the wireform through the fabric material. The
wire is weaved through the fabric such that the distal tip of the
valley of each wireform extends through the graft and is positioned
on the outside of the fabric structure. The weaving is accomplished
by initially configuring an elongated piece of wire into the
predetermined curvilinear configuration. With the wire so
configured, it may be manually woven through the fabric structure
until the wire extends around the entire circumference of the
fabric structure. The wire is woven such that it is primarily
positioned along the interior of the fabric tube, with only small
segments of wire exposed to the outside of the tube.
[0172] The wireform is woven into the fabric tube such that when
the wire extends around the entire periphery of the fabric tube,
the free ends of the wire protrude from the tube at positions
adjacent to each other, thereby enabling a tail segment 177 to be
defined by the free ends. The loose ends are preferably held
together with a crimping sleeve 178 positioned over them. After
crimping the sleeve to secure the ends to each other and thereby
complete the circular configuration of the wireform, any portion of
the wires extending beyond the ends of the sleeve may be trimmed to
cleanly finish the tail segment.
[0173] As illustrated in FIG. 2, the crimping sleeves extend
outwardly along the external surface of the extension graft and are
radially spaced apart. Preferably, the crimping sleeves on the
upstream portion 172 of the extension graft face in a downstream
direction, thus frictionally engaging with the wall of the aortic
graft body which helps to hold the extension into place. In fact,
these upstream crimping sleeves can actually hook on the interior
surface of the primary bifurcated graft, thus ensuring no
longitudinal movement or separation of the extension graft from the
primary aortic graft. The crimping sleeves on the downstream
portion 174 face upstream and may frictionally engage, but not
penetrate, the wall of the vessel lumen within which the device is
placed. The crimping sleeves act as radiopaque markers,
particularly for aiding in the placement and positioning of the
graft extensions.
[0174] The most proximal wireform 168 and the most distal wireform
166 are positioned with respect to the upper and lower edge of the
fabric layer such that approximately one-third of the wireform
extends beyond the respective edge of the fabric layer In
particular, the proximal-most wireform is positioned to extend
above the edge of the fabric layer to prevent any portion of the
fabric layer from oscillating, or "flapping," in response to the
flow of blood past the edge of the graft. As an additional measure
to prevent such fabric oscillation in the blood stream, the
proximal and distal edges of the fabric are configured with
V-shaped notches corresponding generally to the valleys 152 of the
proximal and distal wireforms. Thus, the risk of the existence of
any loose fabric which could potentially be affected by the passing
flow of blood is substantially reduced.
[0175] In an alternate embodiment of the present invention, the
proximal-most balloon-expandable wireform is preferably configured
to have a diameter in its expanded state which is slightly larger
than that of the portion of the fabric tubular structure into which
it is weaved. By configuring the wireform to be slightly larger
than the fabric into which it is woven, the fabric will be
maintained in a constant state of slight tension upon expansion of
the wireform, thereby reducing the possibility of the fabric
folding or oscillating in response to blood flow through the
graft.
[0176] Additionally, the proximal balloon-expandable wireforms on
the graft extension work in concert with the distal self-expandable
wireforms on the aortic graft to hold the graft extensions in
place. The balloon-expandable wires can be expanded slightly beyond
the diameter of the distal self-expandable wireforms. This will
cause the distal self-expandable wireforms to exert a radially
inward pressure against the balloon-expandable portions of the
graft extensions, thereby enhancing the frictional interface
between them and providing a tighter seal.
[0177] In a preferred embodiment of the present invention, the
wireforms are positioned adjacent one another and are spaced apart
from each other such that the wireforms do not interfere with each
other in either a radially expanded or contracted state. Thus, for
example, the valleys of one wireform are located proximal of the
crests of the next adjacent wireform. Preferably, the wireforms are
also aligned "in phase," with peaks along one longitudinal line and
adjacent valleys aligned along a second longitudinal line, thereby
further reducing the possibility of overlap of adjacent wireforms.
(While there may be some overlapping of the tail segments with an
adjacent wireform, because the tail segments extend on the outside
of the fabric layer and the adjacent wireform is primarily on the
inside of the fabric layer, a small degree of overlap with an
adjacent wireform does not pose a problem.)
[0178] In addition, adjacent balloon-expandable wireforms are not
connected to one another. This coupled with the in-phase
configuration of the wireforms maximizes flexibility of the aortic
graft without permitting deleterious kinking, which is of primary
importance in the often tortuous paths of the abdominal aorta and
iliac arteries.
[0179] An important feature of the extension grafts of the present
invention is the spacing distance between adjacent wireforms. It
has been discovered in accordance with the investigations of the
present invention that optimizing the spacing distance between the
wireforms improves the balance between kink resistance and
flexibility in the graft extensions. Too much space promotes
kinking, while too little space detracts from flexibility. These
are important features in the often tortuous path of the iliac
arteries and abdominal aorta in which the graft extensions are to
be placed.
[0180] FIG. 2A, for example, illustrates in cross-section
balloon-expandable wireforms 176. Preferably the length "L" or
separation distance between adjacent wireforms is measured from the
closest point on each neighboring wire. For example, in FIG. 2A, L
is the distance between crest 150 and valley 152.
[0181] Further, the graft extensions have a diameter "D" which
varies according to the differently sized extensions. In one
embodiment the length L between adjacent wireforms is preferably
less than 2D. In a preferred embodiment the length L between
adjacent wireforms will be less than D. In another preferred
embodiment the length between adjacent wireforms will be less than
D and greater than zero. Therefore, the preferred separation
distance depends on the diameter of the graft.
[0182] In a 14 mm graft a preferred separation distance between
adjacent wireforms that has been found to be acceptable during use
is 2.4 to 2.5 mm.
[0183] Further, as discussed above, the interface between the
upstream portion of the extension graft and the downstream leg of
the aortic graft is preferably standardized such that the
downstream legs and the upstream extensions have the same dimension
at their interface, regardless of the diameter of the aorta above
the aneurysm and the diameters of the iliac arteries below the
aneurysm.
[0184] F. Directional Catheter
[0185] The present invention further includes a directional
catheter. The structure of this catheter is substantially disclosed
in WO 97/26936, which was previously incorporated by reference
hereinabove. Specifically, the directional catheter facilitates
guidewire access to the contralateral leg of the bifurcated graft
to allow placement of a contralateral extension graft into the
bifurcated graft.
[0186] The primary components of directional catheter 220 may be
observed by reference to FIG. 5. The directional catheter includes
a deflecting spring portion 222, (illustrated substantially
deflected). Knob 224 is used to deflect the spring portion.
Connector nut 226 is provided such that the directional catheter
can be operatively connected with the sheath assembly.
[0187] G. Extension Graft Deployment
[0188] The procedure for attaching the extension tubes will now be
described. With reference to FIGS. 13A and 13B, the sheath 134
stiffened by a dilator (not shown) is advanced over the guidewire
128 until the distal tip 138 is located approximately at the septum
region 28. The location of the distal tip 138 is again facilitated
by fluoro-visualization of the marker 139 with respect to the
radiopaque crimping sleeves 84, 85 (FIG. 1) on the graft 10. The
dilator is then proximally withdrawn from within the sheath 134,
and the directional catheter 220 advanced distally over the
guidewire 128 and within the sheath 134 to project a short distance
from the distal tip 138 (FIG. 13B).
[0189] More particularly, the directional catheter 220 is first
inserted over the primary guidewire through the ipsilateral side,
for example, through the right femoral artery 116 and the right
common iliac artery 102 in the present case. FIG. 13A illustrates
the directional catheter 220 operatively connected to the sheath
assembly 132. The spring portion 222 of the directional catheter
220 is positioned such that it is above the septal region 28 of the
aortic graft 10. Proper positioning of the spring portion to the
contralateral side is adjusted by rotating or advancing forwards or
backwards the whole directional catheter 220 while under
fluoro-visualization. The spring portion 222 is deflected by
pulling knob 224 in the direction of the arrow in FIG. 13A. FIG.
13B illustrates the deflected spring portion 222 positioned within
the contralateral leg 14.
[0190] A supplemental guidewire 228 is then advanced through the
directional catheter 220 and out the deflected spring portion 222
to extend down the contralateral leg 14 and through the left common
iliac artery 104. The supplemental guidewire 228 is extended until
it is in the left femoral artery 118, at which time the left
femoral artery is cross-clamped and a cut-down or percutaneous
incision is performed to retrieve the supplemental guidewire. If
the guidewire has not been guided fully along the femoral artery a
snare or similar device can be introduced through the left femoral
artery to grab the guidewire and draw it back to the puncture or
incision site for retrieval.
[0191] As seen in FIG. 13C, once the supplemental guidewire 228 is
in place through the left common iliac artery 104 the directional
catheter 220 is advanced distally through the bifurcated graft 10
and into a position above the renal arteries 106, 108. The spring
portion 222 remains deflected to present a curvilinear upstream
profile. This curved profile enables advancement of the directional
catheter 220 without risk of the distal end of the spring portion
222 snagging on the openings to the renal arteries 106, 108. The
directional catheter 220 remains in this position while the tubular
graft extension 170 is attached to the contralateral leg 14. A
stiffer guidewire 228a is then exchanged with the supplemental
guidewire 228 by conventional methods to extend through the left
iliac artery 104 and within the contralateral leg 14 of the aortic
graft.
[0192] As illustrated in FIGS. 14A and 14B, a second introducer
assembly 230 is introduced with the help of a dilator 240 over the
stiff guidewire 228a in the manner previously described for the
first introducer assembly 130. The dilator 240 is removed leaving a
second sheath 270 in position with its distal tip 272 adjacent the
graft septum region 28. Again, a radiopaque marker 274 on the
distal tip 272 aligns with the septum region 28 and its radiopaque
markers 84, 85 (FIG. 1).
[0193] As seen in FIG. 15A, a second catheter assembly, on which is
packaged the tubular graft extension 170 is then introduced through
the sheath 270. A pusher body, (not shown but similar to that
described above) pushes the tubular graft extension 170 distally
within the sheath 270. Again, this procedure for advancing a graft
upstream with respect to the aneurysm 114 while housed within the
sheath 270 is necessary to avoid difficulties associated with
displacing an irregularly shaped object against the blood flow. It
is especially significant given that the trunk portion 12 has been
expanded into contact with the abdominal aorta 100, and thus the
entire blood flow through the abdominal aorta continues through the
graft legs 14, 16. Ultimately, a distal portion 286 of the
inflation balloon extends from the distal tip 272 of sheath
270.
[0194] Once the tubular graft extension 170 is in place, the second
introducer sheath 270 is withdrawn (as seen by the arrow 276 in
FIG. 15B) to a position within the left common iliac artery 104.
After displacing the second introducer sheath 270, the pusher body
is retracted slightly to release the proximal end of the graft
extension 170. FIG. 15B illustrates the compressed
balloon-expandable tubular graft extension 170 in proper position
for expansion and implantation.
[0195] As illustrated in FIG. 15C, the balloon on the second
catheter assembly is then inflated forcing the upstream portion of
the graft extension 170 into contact with the inner surface of the
contralateral leg 14, and downstream portion of the graft extension
into contact with the inner surface of the left common iliac artery
104. As with the inflation balloon 194 for the trunk portion 12 the
inflation balloon for the tubular graft extension 170 is first
deflated and then stretched to remove it from within graft without
snagging.
[0196] After the tubular graft extension 170 on the contralateral
side has been expanded, the directional catheter 220 in the first
introducer sheath 134 is withdrawn. First, however, the spring
portion 222 is straightened to its home position (FIG. 15C) to
enable the catheter 220 to be retracted within the sheath 134.
[0197] As seen in FIG. 16A, a third catheter assembly on which is
packaged another tubular graft extension 170' is then advanced over
the primary guidewire 128 and through the lumen of the sheath 134
until a distal end 296 of the inflation balloon projects slightly
from the distal tip 138. Again, a radiopaque marker on the distal
end of the balloon catheter is used to place it in registry with
the marker 139 on the distal tip 138, which was previously
registered with the marker at the graft septum region 28.
[0198] The first introducer sheath 134 is slightly larger than the
second sheath 270 because it is sized for passage of the balloon
194 of the first catheter assembly on which the trunk portion 12 is
wrapped. For example, the inner diameter of the introducer sheath
134 may be 19 French, while the inner diameter of the second sheath
270 may be 16 French. As a result, there is some acceptable
clearance between passage of the third catheter assembly and
tubular graft extension 170' thereon and the inner lumen of the
introducer sheath 134. In this manner the introducer sheath 134
need not be removed and replaced with a smaller one.
[0199] In the same manner as on the contralateral side, and as
illustrated in FIG. 16B, first the sheath 134 and then the pusher
body (not shown) are withdrawn proximally to release the tubular
graft extension 170' such that its upstream end is inside the
ipsilateral leg 16 of the aortic graft 10 and its downstream end is
within the right common iliac artery 102. The catheter balloon is
inflated to force the upstream end of the graft extension 170' into
contact with the inner surface of the ipsalateral leg 16. At the
same time, the balloon forces the downstream end of the graft
extension 170' into contact with the inner surface of the right
common iliac artery 102. The final expanded position of the tubular
graft extension 170' is seen in FIG. 16D.
[0200] FIG. 16C illustrates a cross-section of the left common
iliac artery 104 with the first tubular graft extension 170
expanded into contact therewith. As was described with respect to
FIG. 2A, the wireforms 176 terminate in ends which are secured
outside the extension wall 175 with crimps 178. The crimps 178 as
shown project outward from the wall 175 at a slight angle and
provide additional friction to locate the extension 170 within the
artery 104. Advantageously, the crimps 178 are not sharp and do not
penetrate the vessel wall, as with some prior art grafts. Instead,
the irregular surface formed by the multiple crimps 178 prevents
migration of the tubular graft extension 170 without damage to the
wall of the artery 104.
[0201] Subsequently, the inflation balloon is deflated and then
stretched before removing it along with the third catheter assembly
from within the graft extension 170'.
[0202] In one embodiment of the present invention, the upstream
portions of either of the graft extensions 170, 170' may be
slightly over-sized to maximize the frictional engagement with the
downstream portions of the respective contralateral or ipsilateral
legs 14, 16. In particular, the over-expansion of the
balloon-expandable wireforms slightly beyond the diameter of the
distal self-expandable wireforms causes the distal self-expandable
wireforms of the contralateral or ipsilateral legs to exert a
radially inward force against the balloon-expandable portions of
the graft extension. This resistance serves to improve the
frictional engagement between the contralateral downstream leg and
the graft extension. Furthermore, the respective wireforms and
associated crimps' tend to hook together to more securely couple
the graft extensions 170, 170' to the respective contralateral or
ipsilateral legs 14, 16.
[0203] In an alternate embodiment, colloquially known as the
"kissing" technique, both the ipsilateral and contralateral balloon
catheters could remain in place during implantation of both leg
extensions 170, 170'. In this technique, the third catheter balloon
for the ipsalateral leg extension 170' is inflated while the second
catheter balloon remains within the contralateral leg extension
170. In other words, while the third catheter balloon inflates, the
second catheter balloon remains in place in the contralateral leg
extension 170, and is preferably deflated to ambient pressure but
is not stretched or reduced by a vacuum. The third catheter balloon
is subsequently deflated, stretched and removed, followed by
deflation, stretching and removal of the second catheter balloon.
The use of the kissing technique or the more common sequential
contralateral-ipsalateral extension implantation technique is up to
the preference of the surgeon.
[0204] An angiographic examination may take place to determine if
the grafts are correctly placed and functioning. The second sheath
assembly and the stiff guidewires are withdrawn and the
contralateral incision or puncture is sutured. The first introducer
sheath assembly is then withdrawn and the right femoral incision is
sutured. The result is a functioning trouser graft bridging an
aneurysm as illustrated in FIG. 16D.
[0205] The operation may be carried out using a general
anaesthetic, an epidural anaesthetic, or in suitable cases, using
only a local anaesthetic.
[0206] The present invention may be embodied in other specific
forms without departing from its spirit or essential
characteristics. The described embodiments are to be considered in
all respects only as illustrative and not restrictive. The scope of
the invention is, therefore, indicated by the appended claims
rather than by the foregoing description. All changes which come
within the meaning and range of equivalency of the claims are to be
embraced within their scope.
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