U.S. patent application number 10/071635 was filed with the patent office on 2005-10-13 for apparatus and methods for conduits and materials.
Invention is credited to Laguna, Alvaro.
Application Number | 20050228474 10/071635 |
Document ID | / |
Family ID | 27732284 |
Filed Date | 2005-10-13 |
United States Patent
Application |
20050228474 |
Kind Code |
A1 |
Laguna, Alvaro |
October 13, 2005 |
APPARATUS AND METHODS FOR CONDUITS AND MATERIALS
Abstract
The present invention provides apparatus and methods for a
conduit, such as an implantable conduit for a vessel. The conduit
may comprise a main member and a side-branch member. The conduit
may be implanted with the side-branch member initially disposed
within the main member. When positioned, the side-branch member may
then be extended from within the main member and into a vessel
side-branch. The materials for the conduit may include
circumferentially distensible and/or low recoil materials.
Inventors: |
Laguna, Alvaro; (Flagstaff,
AZ) |
Correspondence
Address: |
GREENBERG TRAURIG, LLP
77 WEST WACKER DRIVE
SUITE 2500
CHICAGO
IL
60601-1732
US
|
Family ID: |
27732284 |
Appl. No.: |
10/071635 |
Filed: |
February 7, 2002 |
Current U.S.
Class: |
623/1.11 |
Current CPC
Class: |
A61F 2002/075 20130101;
A61F 2/07 20130101; A61F 2220/0016 20130101; A61F 2/856 20130101;
A61F 2002/828 20130101; A61F 2230/0067 20130101; A61F 2220/0008
20130101; A61F 2220/0058 20130101; A61F 2002/067 20130101; A61F
2002/061 20130101; A61F 2002/826 20130101; A61F 2/90 20130101; A61F
2220/0075 20130101; A61F 2220/005 20130101 |
Class at
Publication: |
623/001.11 |
International
Class: |
A61F 002/06 |
Claims
1-23. (canceled)
24. A system for implanting a conduit with at least one side-branch
in a vessel, comprising: a main member comprising a wall having an
opening; at least one side-branch member having a proximal end
which is both integrally connected to the main member at the
opening and disposed within the main member at a time prior to
insertion of the main member into the vessel, wherein the at least
one side-branch member is configured and arranged within the main
member at a time prior to insertion of the main member into the
vessel to allow the at least one side-branch member to be extended
from within the main member through the opening; and a delivery
system engaging at least one of the main member and the at least
one side-branch member for implanting the main member and the at
least one side-branch member in the vessel.
25. The system of claim 24, wherein the delivery system includes: a
main guidewire configured to be inserted into the vessel; and a
side-branch guidewire configured to be inserted into a side-branch
of the vessel.
26. The system of claim 25, wherein the delivery system further
comprises: a main balloon catheter releasably attachable to the
main member and slidingly attachable to the main guidewire; and a
side-branch balloon catheter releasably attachable to the at least
one side-branch member and slidingly attachable to the side-branch
guidewire.
27. The system of claim 24, wherein the delivery system includes a
deployment tube configured to engage the at least one side-branch
member.
28. The system of claim 24, wherein the delivery system includes at
least one sheath configured to retain at least one of the main
member and the at least one side-branch member.
29. The system of claim 28, wherein the delivery system further
includes a push element configured to engage at least one of the
main member and the at least one side-branch member and move the at
least one of the main member and the at least one side-branch
member with respect to the sheath.
30. The system of claim 28, wherein the sheath has an aperture
defined through a wall of the sheath, and the sheath aperture is
aligned with the main member opening.
31. The system of claim 30, wherein the delivery system further
comprises: a guidewire inserted into a side-branch of the vessel
through the sheath aperture and the main member opening; and a
balloon catheter adapted to be releasably attached to an end of the
at least one-side branch member and advanced over the
guidewire.
32. The system of claim 24, wherein the delivery system includes at
least one guidewire adapted to be inserted into a vessel.
33. The system of claim 24, further comprising a deployment tube
configured to engage the at least one side-branch member to extend
the at least one side-branch member from within the main member
through the opening.
34-41. (canceled)
42. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member is treated for at least one
of elution of drugs, biocompatibility, radioactivity, and
radiopacity.
43. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member is kink resistant.
44. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member may be distended with at
least one of minimal foreshortening and low recoil.
45. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member is circumferentially
distensible.
46. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member comprises a graft
material.
47. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member includes at least one of
polytetraflourotheylene, polyurethane, polyethylene, polythether
sulfone, and polyester.
48. The system of claim 24, further comprising a flange connected
to the at least one side-branch member and to the wall of the main
member in the vicinity of the opening.
49. The system of claim 24, wherein at least one of the main member
and the at least one side-branch member includes at least one of a
film-tube, extruded tubing, braided tubing, and textile tubing.
50. The system of claim 24, wherein the at least one side-branch
member is integrally connected to the main member using a bonding
process.
Description
FIELD OF INVENTION
[0001] The present invention generally relates to medical devices
and materials.
BACKGROUND OF THE INVENTION
[0002] Vascular disease, the disease of blood vessels, is one of
the leading causes of death in the western world. There are two
main categories of vascular disease, aneurysmal and occlusive.
Aneurysmal disease results in the weakening of blood vessels
causing them to dilate excessively and in some instances ultimately
rupture. Occlusive disease results in blockage of blood vessels,
limiting the conveyance of blood.
[0003] Stents and stent-grafts are commonly used to treat diseased
blood vessels and other tubular structures within the body. Stents
and stent-grafts have been employed successfully to either
reinforce afflicted blood vessels in the case of aneurysmal
disease, or to radially open and support blood vessels for the
purpose of restoring blood flow in the case of occlusive disease.
To such ends, stents and stent-grafts have been implanted in the
coronary as well as peripheral vasculature. Additionally, stents
have been implanted within the neurovasculature, and in other
bodily conduits such as the urinary tract, the bile duct, and the
tracheo-bronchial tree.
[0004] Current stent-grafts intended for the treatment of
aneurysmal disease are generally available in various diameters.
Several devices are available in bifurcated configurations. These
bifurcated devices are typically designed for use within the aortic
bifurcation, where the abdominal aorta branches into the right and
left common iliac arteries. Frequently, this anatomic region is
riddled by aneurysmal disease, causing a potentially
life-threatening situation. In an effort to treat the potentially
life-threatening situation, bifurcated stent-grafts are implanted
within the aneurysmal regions of the afflicted vessels, essentially
forming a new blood flow conduit within the aneurysm, and isolating
the aneurysm from blood flow and the associated blood pressure.
This is referred to as excluding the aneurysm. Similarly, aneurysms
of the aortic arch and the thoracic aorta are also common.
[0005] Conventional stent-grafts, however, do not accommodate
side-branches of the aorta. Once an aneurysm has been excluded, the
entire diseased section of the afflicted vessel is isolated from
normal blood flow. This isolation includes any side-branches
emanating from the aorta within the afflicted region. While this
may be a good outcome from the perspective of managing a
potentially life-threatening situation, such isolation from blood
flow can lead to ischemic complications in certain areas of the
body. For example, emanating from the abdominal aorta distal to the
renal arteries are lumbar arteries, testicular/ovarian arteries,
and the inferior mesenteric artery, which provides blood to the
left transverse colon, descending and sigmoid colons, and rectum.
Many aneurysms of the abdominal aorta include the origin of the
inferior mesenteric artery. After successful exclusion of these
aneurysms, the left transverse colon, descending and sigmoid
colons, and rectum rely on collateral circulation for their blood
supply. For many patients, the collateral circulation is
sufficient, but for others it is not, resulting in complications
involving the various organs.
[0006] Additionally, many aorto-iliac aneurysms involve the
abdominal aorta as well as substantial portions of either (or both)
of the common iliac arteries. In many cases, the disease extends
along the common iliac artery past the bifurcation point where the
common iliac branches into the external and the internal iliac
arteries. In such cases, the endoluminal treatment of the aneurysm
may require extending the stent-graft device into the external
iliac artery, isolating the internal iliac artery from normal blood
supply and leaving large portions of the pelvic area and leg
reliant on collateral circulation for their blood supply. For
example, the hypogastric artery, which supplies blood to the pelvic
area, branches from the internal iliac artery. Isolation of the
hypogastric artery from normal blood flow can result in buttock
claudication, impotence, and colon ischemia.
[0007] Aneurysms of the aortic arch, for example, can be especially
difficult to treat using currently available stent-graft devices.
Three major vessels originate from the aortic arch: the
brachiocephalic, the left common carotid, and the subclavian
artery. These vessels provide critical blood flow to the head, neck
and arms. If a stent-graft device is endoluminally implanted to
treat aortic arch aneurysms, adjunctive measures must be taken to
ensure adequate blood supply to the body parts (especially the
brain) that receive their blood supply from the affected
vessels.
[0008] On the other hand, while in some instances isolation of a
side-branch vessel via aneurysm exclusion results in compromised
blood supply due to inadequate collateral circulation, in
situations of abundant collateral circulation, the presence of a
side-branch vessel can actually hinder aneurysm exclusion.
Retrograde blood flow from side-branches emanating within the
aneurysmal region can maintain blood pressure within the aneurysm,
often resulting in leakage between the stent-graft device and the
afflicted vessel.
[0009] Like stent-grafts intended for the treatment of aneurysmal
disease, stent-grafts intended for the treatment of occlusive
disease are generally tubular and available in various diameters.
Such stent-graft devices offer the advantage of providing a
physical barrier, which impedes reproliferation of the disease
through the wall of the implanted device. The treatment of vessels
afflicted by occlusive disease at points of bifurcations, however,
can be problematic due to the unpredictability of the vascular
remodeling associated with balloon angioplasty and stent-graft
implantation. In many instances, side-branches can be compromised
as a result of plaque redistribution from the main vessel into the
origin of the side-branch, resulting in stenosis of the
side-branch.
SUMMARY OF THE INVENTION
[0010] A prosthetic conduit according to various aspects of the
present invention includes a main member and a side-branch member.
The main member may be configured to reside in a main vessel. For
example, one embodiment comprises at least one stent, at least one
main graft, and at least one opening in its side wall. The
side-branch member is suitably configured to reside in a
side-branch vessel, and may include, for example, at least one
side-branch stent and at least one side-branch graft. The
side-branch member is connected to the main member at the side wall
opening. The side-branch member may be configured to be extendable
through the opening to deploy the stent-graft.
[0011] The side-branch member may be located within the main member
before and during delivery of the stent-graft to a desired location
within a vessel. Once the main member is placed in a desired
location, the side-branch member may be pushed or pulled out of the
main member and into the desired side-branch vessel. The
stent-graft may be inserted into a vessel at one access site and
placed at a desired location within the vessel by any suitable
method, such as using balloon catheters, guidewires, and/or a
constraining sheath with a push tube.
[0012] Materials according to various aspects of the present
invention that may be used in the main member, the side-branch
member, and/or other elements are distensible. In particular, the
materials may be treated to circumferentially distend without
significant foreshortening and/or recoil.
BRIEF DESCRIPTION OF EXEMPLARY DRAWINGS
[0013] Additional aspects of the present invention are evident upon
reviewing the non-limiting embodiments described in the
specification and the claims, in conjunction with the accompanying
figures, wherein like numerals designate like elements:
[0014] FIG. 1 is a perspective view of an exemplary embodiment of a
prosthetic conduit with a side-branch shown within a cross-section
of a vessel with a side-branch.
[0015] FIG. 2 is a perspective view of an exemplary embodiment of a
main member of a prosthetic conduit.
[0016] FIG. 3 is a perspective view of an exemplary embodiment of a
side-branch member.
[0017] FIG. 4 is a cross-sectional view of an exemplary embodiment
of a prosthetic conduit, shown with an apparatus for delivery,
including a main guidewire, a main balloon catheter, a side-branch
guidewire and a side-branch balloon catheter.
[0018] FIG. 5 is a flow chart illustrating an exemplary delivery
and deployment process.
[0019] FIG. 6 is a perspective view of an exemplary embodiment of a
prosthetic conduit, with the distal end of the main member inflated
by a balloon catheter and the side-branch retracted, shown within a
cross-section of a vessel with a side-branch.
[0020] FIG. 7 is a cross-sectional view of an exemplary embodiment
of a prosthetic conduit, with the distal end of the main member
inflated with a balloon catheter and the side-branch member
partially pushed out from within the main member.
[0021] FIG. 8 is a perspective view of an exemplary embodiment of a
prosthetic conduit, shown within a cross-section of a vessel with a
side-branch, with the main member fully expanded and the
side-branch member not fully expanded.
[0022] FIG. 9 is a cross-sectional view of an exemplary embodiment
of a prosthetic conduit with a deployment tube.
[0023] FIG. 10 is a cross-sectional view of an exemplary embodiment
of a prosthetic conduit wherein the main member is self-expanding,
shown with an apparatus for delivery including a constraining
sheath, a push tube, a side-branch balloon catheter, and a
side-branch guidewire.
[0024] FIG. 11 is a cross-sectional view of an exemplary embodiment
of the distal end of a constraining sheath configured to deliver a
prosthetic conduit with a self-expanding main member within a
vessel.
[0025] FIG. 12 is an end-on view of the distal end of an exemplary
embodiment of the constraining sheath used to deliver a prosthetic
conduit with a self-expanding main member within a vessel.
[0026] FIG. 13 is a cross-sectional, end-on view of an exemplary
embodiment of a push tube device configured to deliver a prosthetic
conduit with a self-expanding main member within a vessel.
[0027] FIGS. 14A-B are a flow chart illustrating an exemplary
preparation process for a prosthetic conduit.
[0028] FIG. 15 is a graph illustrating distensibility data for a
distensible tube and a non-distensible tube.
[0029] Elements in the figures are illustrated for simplicity and
clarity and have not necessarily been drawn to scale. For example,
the dimensions of some of the elements in the figures may be
exaggerated relative to other elements to help to improve
understanding of embodiments of the present invention.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0030] Various aspects and features of the present invention may be
described in terms of functional components and steps. Such
functional components and steps may be realized by any number of
elements and/or steps configured to perform the specified
functions. For example, the present methods and apparatus may
employ conduits and supports, like grafts and stents, which may
carry out a variety of functions in various embodiments,
applications, and environments. In addition, the present methods
and apparatus may be practiced in conjunction with any number of
procedures and systems, and the apparatus and methods described are
merely exemplary applications for the invention. Further, the
present methods and apparatus may employ any number of techniques,
conventional or otherwise, for placement, use, manufacturing, and
the like. Such general techniques that may be referred to are not
described in detail.
[0031] A prosthetic conduit system according to various aspects of
the present embodiment is implantable within an organism, such as a
human being or animal. The prosthetic conduit may comprise any
conduit, for example for use in blood vessels, bile ducts, the
urinary tracts, or any other conduit in the organism. For example,
a prosthetic blood vessel structure may comprise a stent, a graft,
a stent-graft, or other implantable structure. The prosthetic blood
vessel may be configured, however, in any manner according to the
particular application or environment, including variations in
dimensions, shape, materials, flexibility, and the like. Various
aspects of the present invention may also be applicable to other
devices, such as other medical devices and other conduits.
[0032] Referring to FIG. 1, a prosthetic conduit system 100
according to various aspects of the present invention includes a
prosthetic conduit 102, such as a stent-graft. In various
embodiments, the prosthetic conduit 102 includes a side-branch, and
is suitable for placement in a main vessel 108 with a side-branch
vessel 110. For example, the prosthetic conduit 102 may include a
main member 104 and a side-branch member 106. Each of the main
member 104 and the side-branch member 106 may include one or more
stents and one or more sections of graft material.
[0033] Although the present exemplary embodiment comprises the
stent-graft having one main member 104 with one side-branch member
106, the various configurations of a prosthetic conduit are not so
limited, and may be configured in any suitable manner for the
particular application and/or environment. For example, the main
member 104 may have a bifurcation at one or both ends, two or more
side-branch members 106 may be included, and the like. The
prosthetic conduit 102 may include one continuous piece of graft
material and multiple stents, one continuous stent-graft, or any
suitable combination of one or more stents and/or one or more
pieces of graft material. Furthermore, the side-branch member 106
may be configured to branch from the main member at any suitable
angle. The side-branch member 106 may be further configured to
adapt to a range of angles to allow for placement into multiple
different configurations of main vessel 108 and side-branch vessel
110.
[0034] Similarly, the prosthetic conduit 102 may have any suitable
size or combination of sizes. For example, the main member 104 may
be configured for placement within a relatively large main vessel
108, such as the abdominal aorta, while side-branch member 106 may
be configured for placement within a relatively small side-branch
vessel 110, such as a renal artery. In another embodiment, both the
main member 104 and side-branch member 106 may be relatively small,
for example if the prosthetic conduit is configured to be placed in
human coronary arteries. Thus, the prosthetic conduit 102,
including the main member 104 and side-branch member 106, may have
any suitable dimensions.
[0035] In a first exemplary embodiment, the entire length of the
main member 104 comprises a combination of stent and graft
material, while the side-branch member 106 includes a graft
material along its entire length with a side-branch stent 112
located at its distal end. In another embodiment, each of the main
member 104 and the side-branch member 106 comprises a single
continuous piece of graft material and multiple stents.
Alternatively, the prosthetic conduit 102 may comprise one
continuous stent-graft comprised of a single graft and a single
stent. Further, the prosthetic conduit 102 may comprise one or more
grafts with no stents or one or more stents with no graft sections.
Thus, the prosthetic conduit 102 may comprise various combinations
of one or more stents and one or more pieces of graft material.
[0036] Referring now to FIG. 2, the main member 104 may be
configured to provide a main blood flow conduit and may include a
support for the conduit to keep it open. Further, the main member
104 may be configured to provide flow to and/or from the
side-branch member 106. In the present embodiment, the main member
suitably has a generally tubular configuration with open ends, and
comprises a main stent 200, a main graft 202, and at least one side
opening 204. The main stent 200 provides support to maintain the
desired position and/or configuration of the prosthetic conduit
102. The main stent 200 may be a single stent or a plurality of
stents, and may be present along the entire length of the main
member 104, or only in sections, and may extend beyond the length
of the main graft 202. The main stent 200 may be incorporated into
the main member 104 in any location by any suitable method, or may
be installed separately. The main stent 200 may be deployed in any
appropriate manner, such as balloon expansion, self-expansion, or
any suitable combination of both, and may be constructed of a
variety of materials or combinations, such as, but not limited to,
metals or alloys (stainless steel, titanium, tantalum, nitinol and
the like), polymers, carbon, ceramics and the like.
[0037] Alternative embodiments of the main member 104 may also
include other or additional mechanisms for supporting and/or
securing the main member 104 to a surrounding organism vessel 108.
Stents or other suitable devices, for example, may be utilized to
provide additional support and/or strength to the main member 104,
such that the main stent 200 may be supplemented, replaced, or
omitted altogether. Further, the main member 104 may be secured in
position by an adhesive on at least a portion of the main member
104 outer surface (or the inner surface of the attachment site), a
set of barbs or pins attached to the main member 104 and engaging
the surrounding tissue, and the like.
[0038] The main graft 202 provides a conduit for fluid flow through
the main member 104. The main graft 202 may be comprised of any
suitable material, such as a biocompatible material, or combination
of materials, such as, but not limited to, polyester, polyether
sulfone, polyethylene, polytetrafluoroethylene (PTFE), polyurethane
and the like. Further, the materials may be configured or treated
in any manner to achieve selected characteristics. For example, the
material may be treated in accordance with the disclosure of U.S.
Pat. No. 5,800,522, issued Sep. 1, 1998, to Campbell, et al.
Moreover, the main graft 202 may be comprised of various forms or
combinations of forms, such as, but not limited to, extruded
tubing, braided tubing, textile tubing, tubing created from the
wrapping and bonding of thin films, and the like. The main graft
202 may be of any suitable porosity.
[0039] In the present embodiment, the main graft 202 includes a
thin, flexible material, such as polyethylene. In the present
embodiment, the main graft 202 is not treated, as described below,
to be circumferentially distensible. The main graft 202 may,
however, comprise any suitable material, including a material that
may be distended with minimal foreshortening and recoil to conform
to the organism vessel 108, 110, the stents 112, 200, or other
characteristic. If the main graft 202 material is distensible (for
example, as described and defined in U.S. Pat. No. 5,800,522,
issued Sep. 1, 1998, to Campbell, et al.), the graft material may
be circumferentially distended along its entire length, or in
selected portions. Various coatings or treatments can be applied to
either the main stent 200, the main graft 202, or both, to render
the main member 104 more biocompatible (pyrolytic carbon, hydrogels
and the like) and/or to provide for the elution of drugs (heparin,
anti-platelet agents, platelet derived growth factors, antibiotics,
steroids and the like). Additionally, various coatings or
treatments may be applied to either the main stent 200, the main
graft 202, or both, to render the main member 104 radioactive.
[0040] The main graft 202 may be configured to be placed on either
the inner surface or the outer surface of the main stent 200, or in
any suitable position relative to the inner or outer surface of the
main stent 200. The main stent 200 and main graft 202 may be
connected before placement into a vessel, or the main stent 200 and
main graft 202 may be inserted into a vessel separately and
connected within the vessel. In either case, the main graft 202 may
be attached to the main stent 200 by any suitable mechanism.
[0041] The main member 104 may include a radiopaque material to
enhance the visibility of the main member 104. For example, the
main stent 200 or the main graft 202 may be wholly or partially
comprised of radiopaque materials. Alternatively, radiopaque
markers 206 may be incorporated into the main graft 202 or the main
stent 200, either throughout the structure or at one or more
locations.
[0042] The side-branch member 106 facilitates flow between the main
member 104 and a side-branch vessel 110. For example, referring to
FIG. 3, the side-branch member 106 may have a generally tubular
configuration with an open proximal end 308 and an open distal end
306. The side-branch member 106 suitably comprises a side-branch
graft 310 for facilitating fluid flow between the main member 104
and the open distal end 306. The side-branch member 106 may also
include a side-branch stent 112, for example to support the distal
end 306. In the present exemplary embodiment, the side-branch
member 106 includes a straight section 300, a conical section 302,
and an attachment area, such as a flange 304.
[0043] Similar to the main member 104, the side-branch member 106
may suitably comprise a combination of one or more stents, such as
the side-branch stent 112, and one or more sections of graft
material, such as the side-branch graft 310. The side-branch member
106 may include any suitable combination of stents (if desired) and
graft material. For example, one or more stents may be used in one
side-branch member 106, and/or stents may be placed entirely within
the length of the side-branch graft 310 or may extend beyond the
length of the side-branch graft 310, protruding further into the
side-branch vessel 110.
[0044] The side-branch stent retains the side-branch graft 310 in
an open position and/or secures the position of the side-branch
graft 310. The side-branch stent 112 may be positioned in any
suitable manner, such as by placing the stent in a desired position
and expanding the stent within the organism vessel 110. The
side-branch stent 112 may be balloon expandable, self-expanding, or
any combination, and may be constructed from one or more of a
variety of suitable materials, such as, but not limited to, metal
or alloys (stainless steel, titanium, tantalum, nitinol and the
like), polymers possessing varying degrees of bioabsorbtion and
biodegradation, carbon, ceramics, and the like.
[0045] The side-branch stent 112 may be configured such that it is
in contact with the inner or outer surface of the side-branch graft
310 or a combination of both. The side-branch stent 112 may engage
or be attached to the side-branch graft 310 in any appropriate
manner. For example, in one embodiment, the side-branch stent 112
may be inserted into a vessel as a separate piece and may be
attached to the side-branch graft 310 within the side-branch vessel
110. In other embodiments, the side-branch stent 112 is configured
to be implanted at the same time as the side-branch graft 310.
[0046] The side-branch graft 310 may be constructed from one or
more of a variety of suitable materials, such as, but not limited
to, polyester, polyether sulfone, polyethylene,
polytetrafluoroethylene, polyurethane and the like. The side-branch
graft 310 may be of any suitable porosity. In the present
embodiment, the side-branch graft 310 includes a thin, strong,
flexible, and/or kink resistant material. For example, the
side-branch graft 310 suitably includes a material, such as treated
polyethylene, that may be circumferentially distended without
significant foreshortening and/or recoil. The graft material may be
circumferentially distensible along its entire length, or in
selected portions. Further, the materials may be configured or
treated in any manner to achieve selected characteristics. For
example, the material may be treated in accordance with the
disclosure of U.S. Pat. No. 5,800,522, issued Sep. 1, 1998, to
Campbell, et al. Furthermore, side-branch graft 310 may be
comprised of various forms or combinations of forms, such as, but
not limited to, extruded tubing, braided tubing, textile tubing,
tubing created from the wrapping and bonding of thin films, and the
like.
[0047] Various coatings or treatments may be applied to render the
side-branch stent 112 and/or the side-branch graft 310 more
biocompatible (pyrolytic carbon, hydrogels and the like) and to
provide for the elution of drugs (heparin, anti-platelet agents,
platelet derived growth factors, antibiotics, steroids and the
like). Various coatings or treatments may be applied to render the
side-branch stent 112 and/or the side-branch graft 310 radioactive.
Further, the side-branch member 106 may include one or more areas,
such as portions of the graft 310 and/or the side-branch stent 112,
that are radiopaque. For example, the side-branch stent 112 may be
constructed from one or more radiopaque materials and/or one or
more radiopaque markers (not shown) may be placed on the graft 310
or the side-branch stent 112 materials at one or more locations
along the side-branch member 106.
[0048] The side-branch member 106 is connected to the main member
104 to allow fluid flow between the two components. The side-branch
member 106 is suitably connected via its proximal end 308 to the
side opening 204 of the main member 104. In the present embodiment,
the conical section 302 has a diameter that is larger at the
proximal end 308 and tapers as it approaches the straight section
300. The proximal end 308 may be configured to fit within, around,
or in any other suitable configuration with the side opening 204 of
the main member 104.
[0049] The proximal end 308 may further include a mechanism, such
as the attachment area including the flange 304, for facilitating
attachment of the side-branch member 106 to the side opening 204 of
the main member 104. The flange 304 may be bonded in any
appropriate manner to the outer surface, the inner surface, or any
other appropriate portion of the main member 104. The flange 304
may be incorporated into the proximal end 308 to provide a surface
that may be easily positioned against and bonded to the perimeter
of the side opening 204, for example to effect a liquid-tight and
strong connection.
[0050] The side-branch member 106 may be configured for attachment
to the main member 104 at any suitable angle. The prosthetic
conduit 102 may be provided in multiple angular and structural
combinations, enabling a variety of configurations. Furthermore,
the side-branch member 106, or a portion thereof, may be configured
to allow flexibility, such that prosthetic conduit 102 may be used
in a variety of different angles between the main vessel 108 and
the side-branch vessel 110. For example, in one embodiment, a
particular prosthetic conduit 102 may be placed or used in vessels
having anywhere from a 25-degree angle to a 45-degree angle. Other
embodiments may accommodate other angles and/or greater or lesser
ranges of angles.
[0051] The prosthetic conduit system 100 according to various
aspects of the present invention may be placed directly at a
selected site. Alternatively, the prosthetic conduit system 100 may
be introduced at a first site and delivered to the desired location
using a delivery system. The prosthetic conduit system 100 may also
include a deployment system for deploying the prosthetic conduit
102 at the selected site. The delivery system and/or the deployment
system may be integrated into or independent from the prosthetic
conduit 102. The delivery system suitably places and stabilizes the
prosthetic conduit 102 at a desired location. The deployment system
suitably configures and secures the prosthetic conduit 102 for
operation following delivery.
[0052] The delivery system for positioning the prosthetic conduit
102 in the desired position may comprise any suitable delivery
system, such as, but not limited to, one or more balloon catheters,
guidewires, introducer sheaths, guiding catheters, push tubes,
and/or constraining sheaths. Referring to FIG. 4, an exemplary
integrated delivery and deployment system according to various
aspects of the present invention comprises a main guidewire 408, a
main balloon catheter 400, a side-branch guidewire 410, and a
side-branch balloon catheter 406. The main guidewire 408 and the
side-branch guidewire 410 may comprise any suitable guides to
facilitate navigation of the prosthetic conduit 102 to a desired
location and extension of the side-branch member 106. The
guidewires 408, 410 are advanced through the organism vessels to
guide the prosthetic conduit 102 to the desired location.
[0053] The balloon catheters 400, 406 move the prosthetic conduit
102, secure the prosthetic conduit 102 in position, and/or deploy
the prosthetic conduit 102. The main balloon catheter 400 and
side-branch balloon catheter 406 may be conventional balloon
catheters, and may possess varying degrees of compliance. For
example, in some embodiments the balloon catheters 400, 406 may be
highly compliant, such as embolectomy balloon catheters, while in
other embodiments the balloon catheters 400, 406 may be
non-compliant or semi-compliant high-pressure balloon dilation
catheters. Additionally, the balloon catheters 400, 406 may be
either over-the-wire or rapid-exchange balloon catheters.
[0054] The balloon catheters 400, 406 are configured to engage the
guidewires 408, 410 so that the balloon catheters 400, 406 may move
along the guidewires. The balloon catheters 400, 406 are also
configured to engage the prosthetic conduit 102 to facilitate
movement and deployment of the prosthetic conduit 102. For example,
in the present embodiment, the distal end 402 of the main member
104 may be releasably attached, by any suitable mechanism, to the
main balloon catheter 400, and the distal end 306 of the
side-branch member 106 may be releasably attached to the
side-branch balloon catheter 406.
[0055] The prosthetic conduit 102 may be equipped with the delivery
system and/or deployment system prior to implantation.
Alternatively, the delivery system may be provided at the time of
implantation. For example, the main balloon catheter 400 may be
integrated into the prosthetic conduit 102 at the time of
manufacture, or may be connected to the prosthetic conduit 102 at
the time of implantation. Similarly, the side-branch balloon
catheter 406 may be omitted during the initial introduction of the
prosthetic conduit 102 into the vasculature. The relatively small
profile of the side-branch guidewire 410 may be advantageous in
certain situations compared to the side-branch balloon catheter 406
or a tube. Thus, installation techniques and conduits may be
selected according to the particular configuration, application, or
situation.
[0056] Referring to FIG. 5, to place the prosthetic conduit 102 at
a desired location, the main guidewire 408 may be introduced into
the vasculature and navigated into the main vessel 108 (step 510).
The main balloon catheter 400, releasably attached to the distal
end 402 of the main member, may be advanced along the main
guidewire 408, advancing with it the prosthetic conduit 102 (step
512). To enhance accuracy of placement of the prosthetic conduit
102, the side-branch guidewire 410 may be used to align the side
opening 204 of the main member 104 with the origin of the
side-branch vessel 110 (step 514).
[0057] When the prosthetic conduit 102 is placed at a desired
location, it may be secured in the desired position (step 516), for
example using the balloon catheters 400, 406. For example,
referring to FIG. 6, upon properly positioning the prosthetic
conduit 102, the main member distal end 402 may be secured in
position, for example by inflating the main balloon catheter 400
while the side-branch member 106 remains retracted. The main member
distal end 402 may be expanded by the main balloon catheter 400
until the distal end 402 contacts the inner surface of main vessel
108. Expansion of the main member distal end 402 tends to stabilize
the prosthetic conduit 102 so that the side-branch member 106 may
be extended from the main member 104 and into the side-branch
vessel 110. The remainder of the main member 104 may also be fully
expanded along its entire length, either by one or more balloon
catheters, by self-expansion, or by other suitable methods or
apparatus.
[0058] After the position of the prosthetic conduit 102 has been
secured, it may be deployed for operation. Any suitable deployment
system may be employed to deploy the prosthetic conduit 102, and
the deployment system may be configured in any suitable manner to
configure the prosthetic conduit 102 for operation. The prosthetic
conduit 102 may be equipped with the deployment system prior to
implantation or at the time of implantation.
[0059] In the present embodiment, the prosthetic conduit 102 is
configured so that the side-branch member 106 is initially located
within the main member 104 for delivery into a vessel. Such a
configuration may ease delivery of the prosthetic conduit 102 into
one or more vessels. Thus, the deployment system is suitably
configured to extend the side-branch member 106 from within the
main member 104 and into the side-branch vessel 110, and expand the
main member 104 and side-branch member 106 to facilitate fluid
flow. In particular, the deployment system includes the main
guidewire 408, the side-branch guidewire 410, the main balloon
catheter 400, and the side-branch balloon catheter 406. When the
prosthetic conduit 102 is properly positioned within the
vasculature by the delivery system, the side-branch balloon
catheter 406 may be moved along the side-branch guidewire 410 to
the distal end 306 of side-branch member 106, unless the
side-branch balloon catheter 406 was placed simultaneously with the
prosthetic conduit 102. The side-branch member 106 may be deployed
by releasably attaching the side-branch balloon catheter 406 to the
side-branch member 106 to extend the side-branch member 106 into
the side-branch vessel 110. The side-branch member 106 is then
suitably extended along the side-branch guidewire 410 and secured
using the side-branch balloon catheter 406.
[0060] The side-branch balloon catheter 406 may be attached to the
side-branch member 106 in any suitable manner, such as by crimping
side-branch stent 112 and the surrounding graft material onto
side-branch balloon catheter 406 to releasably attach side-branch
balloon catheter 406 to the side-branch member 106. In the present
embodiment, the side-branch balloon catheter 406 may be positioned
within the side-branch stent 112 and inflated to a pressure high
enough to engage the side-branch stent 112, but low enough to avoid
substantial expansion of the side-branch stent 112.
[0061] Referring to FIG. 7, after releasably attaching the distal
end 306 of the side-branch member 106 to the side-branch balloon
catheter 406, the side-branch balloon catheter 406 and the
side-branch member 106 may be advanced along the side-branch
guidewire 410 to a desired location, thus extending the side-branch
member 106 into the side-branch vessel 110 (step 520). After
extending the side-branch member 106, the side-branch stent 112 is
in a position to be expanded to secure the side-branch member 106
in position and facilitate flow. In an alternative embodiment, the
side-branch stent 112 may be installed separately, after the
side-branch member 106 has been otherwise pushed or pulled from
inside the main member 104.
[0062] Referring to FIG. 8, the side-branch stent 112 may then be
expanded to contact or adhere to the inner surface of the
side-branch vessel 110 (step 522). For example, the side-branch
balloon catheter 406 is inflated to a selected pressure and for a
selected duration, causing the distal end of side-branch member 106
encompassing side-branch stent 112 to circumferentially distend.
The pressure is then suitably released and side-branch balloon
catheter 406 may be moved toward the proximal end of the
side-branch member 106. The side-branch balloon 406 is inflated
again, causing the adjacent region of the side-branch member 106 to
distend. This process of circumferential distention may be repeated
until the side-branch balloon catheter 406 distends the entire
length of the side-branch member 106 (step 524). When the main
member 104 is placed and fully dilated and the side-branch member
106 is fully extended and distended, the prosthetic conduit 102 is
fully deployed and operational.
[0063] The balloon catheters 400, 406 facilitate delivery of the
prosthetic conduit 102 and extension of the side-branch member. Any
suitable system, however, may be used to deliver and deploy the
prosthetic conduit 102 and side-branch member 106. For example, a
snare may be used to grasp the distal end 306 of side-branch member
106 and unfold it, either by pushing or pulling. Alternatively,
referring to FIG. 9, the deployment system may include a deployment
tube 906, which may be similar in outer diameter to the side-branch
balloon 406 and positioned to provide a passageway into the distal
end 306 of side-branch member 106. The lumen of the deployment tube
906 may accommodate other deployment elements for deploying the
prosthetic conduit 102, such as guidewires, balloon devices,
snares, or other selected devices or materials. The deployment tube
906 may comprise, for example, a guiding catheter and may have
specific bends incorporated into its distal end to facilitate the
deployment of the side-branch member 106. Any suitable embodiment
of a deployment tube may be utilized. During installation, once the
side-branch balloon catheter 406 is inserted into the distal end
306 of side-branch member 106, the deployment tube 906 may be
removed or may be used as a support to stiffen and/or guide the
side-branch balloon catheter 406, thus aiding in the deployment of
the side-branch member 106. Thus, installation techniques and
devices may be selected according to the particular configuration,
application, or situation.
[0064] Another embodiment of a delivery and deployment system
according to various aspects of the present may be adapted to
function with one or more self-expanding stents. For example,
referring to FIGS. 9 and 10, the delivery system may include a push
tube 900 and a constraining sheath 902 configured for maintaining
the prosthetic conduit 102 in a compact configuration until
delivery and deployment and delivering the prosthetic conduit 102
into the main vessel 108. Any suitable embodiment of a constraining
sheath or structure to maintain the prosthetic conduit 102 in a
compact configuration may be utilized.
[0065] The prosthetic conduit 102 and push tube 900 may be
positioned within the constraining sheath 902 such that the
proximal end 412 of the main member 104 is in contact with the
distal end of the push tube 900. The constraining sheath 902
suitably contains the prosthetic conduit 102 and the push tube 900,
and may be introduced into a vessel or other bodily conduit, for
example as a catheter may be introduced, and may be advanced to a
desired position within a vessel. When the prosthetic conduit 102
is advanced to a desired location, the constraining sheath 902 may
be pulled back proximally, the push tube 900 may be pushed
distally, or both, to release the prosthetic conduit 102 from the
constraining sheath 902. Because the main member 104 may be
self-expanding, once released from constraining sheath 902, the
main member 104 may expand to contact the inner wall of main
organism vessel 108.
[0066] The constraining sheath 902 may suitably include an aperture
for allowing the side-branch guidewire 410 to protrude through the
constraining sheath 902, which allows the side-branch guidewire 410
to help align the side opening 204 with the origin of the
side-branch vessel 110. The side-branch guidewire 410 may be
extended laterally from the constraining sheath 902 and into the
side-branch vessel 110 to facilitate the correct positioning of the
prosthetic conduit 102. When the prosthetic conduit 102 is
correctly positioned, the side-branch guidewire 410 may be
retracted, allowing the constraining sheath 902 to be moved axially
with respect to the prosthetic conduit 102.
[0067] The constraining sheath 902 may be configured to the
particular application and environment. For example, referring to
FIGS. 11 and 12, the constraining sheath 902 may include a distal
tip 904, configured to enhance navigability of the constraining
sheath 902 within bodily conduits. The distal tip 904 may be
configured to have a tapered profile that reduces resistance during
movement within bodily conduits and may suitably include multiple
wedge-shaped segments 1100. The tapered profile and wedge-shaped
segments 1100 may enhance navigability within bodily conduits by
providing a more hydro-dynamic distal tip 904 for the constraining
sheath 902. The distal tip 904 may also be configured as a
substantially closed structure to inhibit bodily fluids from
entering the constraining sheath 902. Furthermore, the wedge-shaped
segments 1100 may be configured to be flexible, allowing the
constraining sheath 902 to be easily moved relative to the
prosthetic conduit 102.
[0068] The push tube may be configured in any suitable manner to
facilitate delivery of the prosthetic conduit 102. For example,
referring to FIG. 13, an exemplary embodiment of a push tube 900
configured to deliver the prosthetic conduit 102 with the
self-expanding main member 104 within an organism vessel may
include a cross-section shaped as an incomplete annulus with a gap
1300. The push tube 900 with the gap 1300 may be configured to
enable the push tube 900 to be easily removed from the organism
vessel after deployment of the prosthetic conduit 102 without
removing or otherwise disturbing the side-branch balloon catheter
406 or the side-branch guidewire 410.
[0069] The push tube 900 may also include a section that extends
within the lumen of the main member 104, providing additional
stiffness during installation. The push tube 900 may also include a
section extending along the entire length of the main member 104,
and abutting the distal end 402 of the main member 104, which tends
to offer further control during installation of the prosthetic
conduit 102.
[0070] The side-branch member 106 may be pushed or pulled out of
the interior of the main member 104 in any suitable manner, for
example by pushing it out with the releasably attachable
side-branch balloon catheter 406. Thus, in this embodiment, the
main member 104 is self-expanding while the side-branch member 106
is balloon expandable. Any 7, suitable deployment system, however,
may be used to extend the side-branch member 106 from within the
main member 104.
[0071] The prosthetic conduit 102 according to various aspects of
the present invention may be manufactured from many different
materials or combinations of materials and may be constructed by
any suitable method. A prosthetic conduit 102 according to various
aspects of the present invention, however, is formed using material
that may be circumferentially distended with minimal foreshortening
and recoil. Accordingly, the material(s) for the prosthetic conduit
102 may be treated to facilitate such distention
characteristics.
[0072] For example, referring to FIG. 14A-B, the main member 104
may be constructed by initially forming a film-tube (step 1410) of
a thin, flexible material, such as a microporous polyethylene film,
for example a segment of Solupor.RTM. 7P03A microporous
polyethylene film manufactured by DSM Solutech. In the present
embodiment, the film has a nominal thickness of about 50.mu., a
nominal porosity of about 85%, and a nominal weight per surface
area of 7 g/m.sup.2, though any of these characteristics may vary
according to the particular application. Various alternative
film-tubes may be employed. For example, films of any suitable
material, both porous and non-porous may be used. The diameter and
wall thickness of the graft component of main member 104 may be
constant or may vary to create graft components with different
properties and different geometries, such as but not limited to
tapers and the like.
[0073] To form the main film-tube, the film is cut to a selected
size, such as an approximately 230.times.155 mm rectangular piece,
and wrapped around the circumference of a mandrel, suitably
comprising stainless steel, and having a desired diameter, such as
about 16 mm, to form a film-tube. Various tooling (mandrels, rods,
etc) may be used. The tooling onto which the film is applied may be
of a constant outer diameter, or may have a variable outer diameter
to create tubes of various geometries such as tapers and the like.
Any suitable tooling having any suitable shape may be employed.
[0074] In the present embodiment, the tube is wrapped in a
direction perpendicular to the major axis of the tube. The film may
be wrapped in any suitable manner, for example, helically with
respect to the major axis of the tube, or in any other appropriate
manner. The wrapping is completed with the 230 mm long edges of the
rectangular piece parallel to the major axis of the mandrel such
that a desired thickness is achieved. In the present embodiment,
approximately three layers of the film cover the mandrel. The
circumference of the 16 mm mandrel is approximately 50.3 mm, so to
achieve a film thickness of approximately three layers after
wrapping, one side of the rectangular piece is cut to a dimension
of about 155 mm, providing a selected overlap length, such as
approximately 4 mm. During wrapping, the film may be treated, such
as wet with isopropyl alcohol, to enable the film to better lay
smoothly.
[0075] With the wrapping complete, both ends of the wrapped film
section are secured to the mandrel, such as with wire. Next, the
polyethylene film may be secured along its length to the mandrel.
For example, the polyethylene section may be helically wrapped with
porous polytetrafluoroethylene film, suitably covering the
film-tube entirely, ensuring that the layers of the polyethylene
film contact each other.
[0076] The layers of the wrapped film are bonded together to form a
single tube (step 1412). Bonding of the layers may be achieved by
any suitable method. For example, the 16 mm mandrel may be placed
in an air convection oven set at 150.degree. C. for 10 minutes and
subsequently removed and allowed to cool. Once cool, the helically
wrapped porous PTFE film as well as the securing wire are removed
and discarded. The resulting 16 mm inner diameter polyethylene tube
is then removed from the 16 mm outer diameter mandrel. The
150.degree. C. temperature and 10 minute time combination is chosen
to bond the film layers to each other, forming a robust tube, but
leaving the porous nature of the polyethylene film substantially
unchanged, and avoiding thermal degradation of the film. Any
suitable temperature and time combination, however, may be used.
Alternatively, heated dies that contact the film either partially
or wholly may also be used. Further, various adhesives or coatings
may be applied to the film to effect bonding. The use of such
adhesives or coatings may result in tubes that are composite in
nature, having the combined characteristics of the adhesive or
coating as well as the characteristics of the film material.
[0077] The film-tube may then be cut, if desired, to a particular
length, such as approximately 70 mm. The side opening 204 may then
be formed in the tube, such as using a 4 mm diameter biopsy punch
(step 1414). Any suitable geometry and tooling may be employed to
create the side opening 204. Additionally, alternative embodiments
of the side opening 204 may include sections of material protruding
laterally from the main member 104, to which the side-branch member
106 may be attached.
[0078] The side-branch member 106, such as an approximately 4 mm
inner diameter polyethylene film-tube, may be formed in the same
manner as the approximately 16 mm inner diameter polyethylene
film-tube described above (step 1416). In particular, a graft
material, such as 7P03A microporous polyethylene film, is cut to a
selected size and shape, such as an approximately 230.times.42 mm
rectangle, and wrapped around the circumference of a mandrel having
the desired outer diameter, such as about 4 mm. In this instance,
the circumference of the 4 mm mandrel is approximately 12.6 mm, so
to achieve a film thickness of three layers after wrapping, one
side of the rectangular piece is cut to a dimension of 42 mm,
providing approximately 4 mm extra film length for overlap. During
wrapping, the film may be wet with isopropyl alcohol to facilitate
smooth layers.
[0079] With the wrapping complete, both ends of the 230 mm long
wrapped film section may be secured to the mandrel, for example
with wire. Next, the film is secured in position, such as by
helically wrapping a porous PTFE film over the 230 mm long wrapped
film section, covering the section substantially entirely. The PTFE
film tends to secure the polyethylene film about the mandrel so
that the layers of the polyethylene film contact each other.
[0080] The layers of the side-branch tube are then suitably bonded
together to form the side-branch tube (step 1418). For example, the
4 mm mandrel may be placed in an air convection oven set at
150.degree. C. for 5 minutes and subsequently removed and allowed
to cool. Once cool, the helically wrapped porous
polytetrafluoroethylene film as well as the securing wire are
suitably removed and discarded. The temperature and duration may be
selected according to any suitable criteria to bond the film layers
to each other and form a robust tube, but substantially maintaining
the porous nature of the polyethylene film and avoiding any
significant thermal degradation or weakening of the film. The
resulting 4 mm inner diameter polyethylene tube is then removed
from the 4 mm outer diameter mandrel and suitably cut to a desired
size, such as into two equal lengths.
[0081] In accordance with various aspects of the present invention,
the side-branch tube and/or the main member 104 may be treated in
any suitable manner to provide selected characteristics, such as
circumferential distention and/or extension capabilities. In the
present embodiment, the side-branch tube is treated to facilitate
distention of at least a portion of the side-branch tube with
relatively low foreshortening and/or recoil. The side-branch tube
is also treated to facilitate kink resistance.
[0082] For example, the side-branch tube may be processed with
cycles of heat, stretching, and/or compressing. The side-branch
tube may be heated and stretched to a desired length and/or
diameter. In the present embodiment, the side-branch tube may be
initially marked at a known interval (step 1420), such as two marks
at a 70 mm interval centered along the length of the side-branch
tube. The film-tube is then secured to a mechanism configured to
stretch the side-branch tube. Any suitable stretching apparatus may
be used, and may include any suitable mechanism for securing the
tube, stretching the tube, heating the tube, measuring, and/or
controlling the amount and rate of stretching. For example, a
sliding mandrel mechanism may comprise two lengths of 3 mm outer
diameter stainless steel tubing and a length of 1.6 mm outer
diameter stainless steel rod. One end of the rod is bent and
inserted into one of the 3 mm outer diameter tubing lengths such
that it is substantially immobile. Both lengths of the 3 mm outer
diameter tubing have a 360.degree. groove cut into the wall
approximately 3 mm away from one end. The film-tube is fitted
coaxially over the 1.6 mm rod and attached to the 3 mm outer
diameter tubing by manually tying a wire over the film-tube and
into the groove at the end of the 3 mm outer diameter tubing. The
other length of 3 mm outer diameter tubing is then fitted coaxially
over the 1.6 mm rod and the same manual wire tying process is used
to secure the other end of the film-tube to the 3 mm outer diameter
tubing.
[0083] When the side-branch tube is secured to the sliding mandrel
mechanism, the assembly is exposed to heat (step 1422), such as via
an air convection oven set at a selected temperature, such as
150.degree. C. The oven is configured with holes at each end so
that the sliding mandrel mechanism and the attached film-tube can
be inserted such that the film-tube is approximately centered
within the oven chamber and each of the 3 mm outer diameter tubing
lengths extend out of each end of the oven. The side-branch tube is
heated for a selected duration, such as one minute, and then slowly
stretched by manually pulling the ends of the 3 mm outer diameter
tubing lengths extending out of each end of the oven (step 1424).
The film-tube is stretched in this manner to a desired length
and/or diameter. Other parameters, such as the tensile force
experienced by the tube, or the outer diameter of the tube during
stretching may also be monitored and/or controlled.
[0084] In the present embodiment, the side-branch tube is stretched
until the marks are approximately 130 mm apart. The lengthening
causes the film-tube to reduce in diameter such that it
substantially contacts the 1.6 mm rod. Tension is maintained on the
film-tube, now stretched and reduced in diameter, ensuring that no
significant change in length occurs while the sliding mandrel
mechanism is removed from the oven. The film-tube is next allowed
to cool and subsequently removed from the sliding mandrel
mechanism.
[0085] At this point, the side-branch tube may be circumferentially
distended. The side-branch tube may be further processed, however,
to achieve additional characteristics. For example, the side-branch
tube may be distended to facilitate later distention with reduced
force up to a selected limit. For example, the side-branch tube may
be initially distended to a first selected diameter (step 1426),
such as by manually fitting the tube over a tapered stainless steel
mandrel having a 2 mm outer diameter section approximately 200 mm
in length, and tapering up to an outer diameter of 3.8 mm over a
length of approximately 40 mm. When fitted entirely over the 3.8 mm
outer diameter section of the mandrel and pulled taut, a distance
of approximately 81 mm separates the two pen marks on the
film-tube. Next, the tube is removed from the 3.8 mm tapered
mandrel, and then further distended over a 4 mm tapered mandrel
(step 1428). When fitted entirely over the 4 mm outer diameter
section of the mandrel and pulled taut, a distance of approximately
75 mm separates the two pen marks on the film-tube. In the present
embodiment, the distention is completed in two steps to make the
process easier, though the distention may be performed in greater
or fewer steps.
[0086] Varying amounts of distention may be performed to achieve
varying final distensibility characteristics. The film-tube may be
distended anywhere from zero to near the circumference at which it
breaks, and the distention may be accomplished in any number of
steps. The distention of the exemplary film-tube is suitably
performed at ambient temperature conditions. Various temperature
conditions, however, may be employed during the distention. The use
of elevated temperature may be required for film-tubes of different
materials, or for film-tubes of greater thickness. Moreover, any
suitable mechanism and method may be employed to complete the
distention. For example, as an alternative to the use of tapered
mandrels, a balloon or bladder may be utilized to pressurize the
film-tube and cause distention.
[0087] The side-branch tube may be further processed, such as to
add features like flexibility and/or kink resistance. In the
present embodiment, the side-branch tube is processed for kink
resistance by sequentially stretching the tube to achieve a desired
diameter and compressing the side-branch tube to form small
corrugations. The corrugations may be formed in any suitable
manner, and facilitate bending of the side-branch member 106
without kinks.
[0088] For example, the side-branch tube may be initially stretched
(step 1430) using any suitable mechanism, such as a linear slide
with a manually driven lead screw. Each end of the side-branch tube
is secured onto the linear slide mechanism, for example using
clamps. Heated air, such as from a hair drying gun set on low, may
be applied to warm the side-branch tube and soften the graft
material. Turning a hand crank connected to a lead screw actuates
the linear slide. The film-tube may thus be slowly stretched.
Periodically, the stretching of the film-tube may be halted,
allowing the stress within the tube to diminish, thereby avoiding
breaking of the tube. The film-tube is stretched until a desired
distance, such as approximately 144 mm, separates the two marks on
the side-branch tube. The film-tube may also be stretched until a
desired diameter is achieved. The side-branch tube may then be
allowed to cool and/or relieve stress for a selected time and
temperature, such as at least five minutes at ambient temperature.
The tube is then removed from the linear slide mechanism. The
processes of distending the tube and subsequently stretching it to
reduce its diameter may be repeated any number of times if
desired.
[0089] The side-branch tube may also be processed to provide other
characteristics, such as resistance to kinking and/or
foreshortening. For example, to add kink resistance and reduce
foreshortening upon distention, the side-branch tube may be
processed to form corrugations. For example, the side-branch tube
may be fitted coaxially over a 1.2 mm diameter stainless steel rod
and again marked for reference (step 1432). The marks are separated
by a selected interval, such as 50 mm, and the marks may be
centered along the length of the side-branch tube. The side-branch
tube is also suitably constrained against the rod, for example
using a thin, strong, porous PTFE film helically wrapped over the
side-branch tube.
[0090] The overwrapped side-branch tube on the 1.2 mm diameter rod
may then be compressed. To facilitate compression, the side-branch
tube is suitably heated (step 1434), such as in an air convection
oven set at a selected temperature and duration, such as 70.degree.
C. for at least about 10 minutes. The side-branch tube may then be
removed from the oven and compressed longitudinally (step 1436),
tending to cause a reduction in length. The PTFE film overwrap
tends to inhibit formation of gross corrugations along the surface
of the film-tube during compression. Any suitable method may be
used to control the size of the corrugations formed along the
surface of the film-tube. For example, the film-tube while on the
1.2 mm diameter rod may be placed within a tube having an inner
diameter slightly larger than the outer diameter of the film-tube
prior to being overwrapped, and may then be longitudinally
compressed within the tube.
[0091] The film-tube is longitudinally compressed a desired amount,
for example so that a distance of approximately 28.5 mm separates
the two pen marks originally separated by a distance of 50 mm. The
side-branch tube may then cool to ambient temperature, the
polytetrafluoroethylene film overwrap is removed, and the film-tube
is removed from the 1.2 mm diameter rod. The resulting 1.2 mm inner
diameter polyethylene film-tube may then be gently pulled (step
1438) or otherwise smoothed to remove any inconsistently large
corrugations, leaving a substantially uniform tube surface.
[0092] The longitudinal compression tends to impart corrugations
along the surface of the film-tube or otherwise shorten the
film-tube. In some materials, like polyethylene, the compression
may cause the tube surface to exhibit small corrugations or
wrinkles. For other materials, the compression may cause
compression of the material itself, such that the material
condenses without forming corrugations in the surface. The porosity
of the material and the temperature may also affect the formation
of corrugations or other shortening of the a film-tube. The
wrinkles or other compression serve to enhance the flexibility of
the tube, tending to allow the tube to undergo substantial bending
without kinking, and also serve to inhibit any change in length of
the film-tube during distention. The processes for achieving the
various characteristics, including kink resistance and
foreshortening minimization, may be applied to other materials as
well, such as material treated in accordance with the disclosure of
U.S. Pat. No. 5,800,522, issued Sep. 1, 1998, to Campbell, et al.
Moreover, other methods may be applied to form corrugations or
compress the tube, such as tying thin wires spaced at regular
intervals around the circumference of the film-tube while the tube
is on the 1.2 mm diameter rod. With the wires in place, the tube
may be longitudinally compressed. The presence of the wires during
the compression results in the formation of wrinkles of a
pre-determined size.
[0093] Although the graft component 310 described above is
circumferentially distensible with low recoil and foreshortening,
the use of non-distensible tubes as the graft component is
possible. The graft component, distensible or not, may be of any
suitable material known in the prior art, or any suitable material
that may become available in the future. Additionally, graft
component 310, may be constructed from any suitable form or
combination of forms such as but not limited to extruded tubing,
braided tubing, textile tubing, and as discussed tubing created
from films or membranes. The graft component may be processed by
any suitable methods. The wall thickness of the graft component 310
of the side-branch member 106 may be constant or may vary to create
graft components with different properties. For example a graft
component may have a thinner wall at the distal end, and a thicker
wall at the proximal end, or vice versa. The graft component may
further have any suitable degree of porosity. Further, all of the
techniques and materials may be applied to other components of the
prosthetic conduit 102, such as the main member 104, or other
devices and materials.
[0094] In an alternative embodiment, a graft component may be
created from a woven textile tube. Woven textile tubes, such as
braided tubes formed generally of helically wound strands, may be
constructed from various suitable materials, such as but not
limited to polyester, polypropylene, and polytetrafluoroethylene.
Braided tubes may exhibit distensible behavior. Typically,
distention of braided tubes is accompanied by pronounced
foreshortening. The relationship between the amount of distention
and the amount of foreshortening can be varied according to the
parameters utilized in the manufacture of the tube.
[0095] A braided tube according to various aspects of the present
invention is circumferentially distensible. A braided tube may be
initially elongated in the direction of the major axis until the
ensuing reduction in diameter is complete. Next, the tube may be
cut to a selected length and fitted coaxially over a rod or mandrel
of appropriate outer diameter. The ends of the tube are then
secured to the rod or mandrel using wire, and the elongated braided
tube is then overwrapped with porous polytetrafluoroethylene film
and longitudinally compressed. The tube, prior to or during the
longitudinal compression, may be heated.
[0096] The porous polytetrafluoroethylene film tends to control the
size of corrugations along the surface of the tube. Next, for
example, the tube is suitably placed in an oven and heated. The
time and temperature parameters are suitably chosen such that the
tube, after removal from the mandrel, substantially maintains the
longitudinally compressed length, but the strands that form the
tube are not permanently bonded to each other. In this fashion, the
tube may be distended, but having been longitudinally compressed,
foreshortens minimally. The braided tube may be gently pulled to
remove any inconsistently large corrugations that may have been
formed during the longitudinal compression process.
[0097] Any suitable degree of longitudinal compression may be
performed to the braided tube. For example, in one embodiment two
marks separated by a known distance may be placed on the braided
tube prior to the tube being elongated, and the marks may be
returned to their original spacing during the longitudinal
compression process. Any suitable method may be employed to
maintain the tube in its longitudinally compressed state but still
allow distention. For example, a mild adhesive may be applied to
the surface of the tube either partially or wholly. Alternatively,
heated dies that contact the surface of the tube either partially
or wholly may be used.
[0098] In accordance with various aspects of the present invention,
the side-branch tube may be equipped with a support (step 1440),
such as the side-branch stent 112 at the distal end of the
side-branch member 106. The stent may be added to the side-branch
tube in any appropriate manner. For example, one end of the 1.2 mm
inner diameter polyethylene graft component may be slightly flared,
such as by using a pair of small hemostats. The graft component may
then be fitted coaxially onto a 1.2 mm diameter stainless steel rod
and constrained against the rod, for example using a helical
overwrap of thin, strong, porous PTFE film. The overwrapping
suitably begins on the rod adjacent to the non-flared end of the
graft component and ends at the base of the small flare at the end
of the graft. The flared end of the graft may then be everted, for
example manually using small hemostats. The PTFE overwrap film may
be removed as necessary as the graft is everted until an everted
section of a desired length, such as approximately 22 mm long, is
obtained.
[0099] The stent may then be placed within the folded over portion
of the graft. For example, a 0.64 mm diameter wire is suitably
pushed underneath the everted section of the graft component,
slightly distending the everted section, creating a small annular
space between the everted section and the underlying graft
component. A selected stent, such as an 18 mm long
balloon-expandable side-branch stent 112, is then placed within the
annular space between the everted section and the underlying graft
component, the end of the side-branch stent 112 abutting the fold
at the end of the everted section of the graft component.
[0100] The approximately 4 mm long length of everted graft
component extending beyond the stent is then suitably bonded to the
underlying graft component, for example using a conventional
soldering iron, to maintain the position of the side-branch stent
112. The bonding process suitably controls the application of heat
to ensure that the graft component is not overly heated,
substantially changing the graft properties, or damaged during the
bonding process. At this point, the everted section of graft
component over the side-branch stent 112 may be radially
compressed, reducing the outer diameter of the end of the graft
component encompassing the stent. The remaining PTFE overwrap film
may be removed and the graft component and stent are suitably
removed from the 1.2 mm diameter rod.
[0101] Alternative embodiments of the side-branch tube may omit the
side-branch stent 112 or replace it, for example with another type
of stent. For example, the side-branch stent 112 may be a
self-expanding stent. A suitable self-expanding stent may be placed
within the annular space created between the everted section and
the underlying film-tube as described. In such an embodiment the
self-expanding stent may be maintained in a compact configuration
by the graft component covering it, and thus the combination of the
self-expanding stent and the graft component is functionally
balloon expandable. One or more stents may be used at any location
along the graft component. In some embodiments the use of both
balloon expandable and self-expanding stents may be preferred.
Further, any suitable method may be employed to attach or
incorporate stents to the graft component. For example stents may
sutured to the graft component, or may be attached by an adhesive.
In some embodiments it may be possible to bond the stent to the
graft component using heat.
[0102] In an exemplary embodiment according to various aspects of
the present invention, an attachment area for attaching the main
member 104 to the side-branch member 106 is provided (step 1442).
For example, the side-branch member 106 suitably includes the
conical section 302 and/or the flange 304. The conical section 302
may be formed in or attached to the side-branch member 106 in any
suitable manner. For example, the portion of the graft component
from the bond site 404 to the proximal end 308 is initially
distended by coaxially fitting it over a 2 mm diameter steel rod,
suitably such that the graft component does not compress
longitudinally and become grossly corrugated, or substantially
elongate. Once distended, the graft component and incorporated
stent are suitably removed from the 2 mm diameter rod. In the
present embodiment, the length of the graft component from the bond
site 404 to the proximal end 308 is approximately 50 mm.
[0103] To form the conical section 302 and flange 304, the graft
component, starting at the proximal end 308, is distended in a
conical configuration, such as by fitting it over a 4 mm tapered
mandrel. The tapered mandrel increases from an outer diameter of
approximately 1.3 mm to an outer diameter of 4 mm over a length of
approximately 30 mm. In the present embodiment, the graft component
is fitted over the 4 mm tapered mandrel such that the proximal end
extends approximately 6 mm onto the 4 mm outer diameter section of
the mandrel.
[0104] Thus, in this particular embodiment, distending the proximal
end 308 over a tapered or conically shaped mandrel at ambient
temperature forms the conical section 302 of the side-branch
member. The conical section may have any suitable geometry,
provided that the proximal end of the side-branch member is able to
be attached to the side opening 204 of the main member 104.
Additionally, the conical section may be formed by any suitable
method at any suitable temperature, such as for example distention
via a balloon, or the use of any other tube flaring equipment. The
method and temperature employed are dependent on the embodiment of
the graft component. In an alternative embodiment, the conical
section may be a separate piece, attached to the side-branch member
by any suitable method.
[0105] Similarly, the flange may be formed in or attached to the
side-branch member 106 in any suitable manner. For example, while
side-branch member 106 remains situated on the 4 mm tapered
mandrel, four cuts may be made at the proximal end of the graft
component, for example using a razor blade. The cuts are suitably
substantially parallel to the major axis of the graft component,
extending approximately 3 mm from the proximal end of the graft
component at selected intervals, such as 0, 90, 180, and 270
degrees around the circumference of the proximal end 308 of the
graft component. The four 3 mm long cuts form four substantially
equal sections around the circumference of the proximal end 308 of
the graft component. The four sections may then be bent to a
position extending laterally, perpendicular to the major axis of
the graft component, to form the flange 304. With the embodiment of
the conical section 302 formed via the 4 mm tapered mandrel, and
the embodiment of the flange created by the four equal sections
around the circumference of the proximal end of the graft
component, the graft component may then be removed from the 4 mm
tapered mandrel.
[0106] The flange 304 may be of any suitable geometry to facilitate
and/or strengthen the connection of the side-branch member to the
main member. The flange 304 may be formed by any suitable
mechanism, such as, but not limited to, flaring the proximal end
308 of the side-branch member 106 and then everting the flared
section, or using any other suitable tube flanging equipment or
process. Alternatively, the flange 304 may be a separate piece,
attached to the side-branch member 106 by any suitable method, or
attached to the side opening 204, or formed from the material
surrounding the side opening 204. Any adaptation of the proximal
end 308 of the side-branch member 106, or the side opening 204 in
the main member 104, either alone or in combination, may be
utilized.
[0107] The main member 104 and side-branch member 106 may be
connected according to any suitable technique or process (step
1444). In the present embodiment, for example, the main member 104
is partially fitted coaxially onto a 16 mm outer diameter mandrel,
leaving the lumen of the main member 104 and the side opening 204
accessible. The side-branch member 106 may be inserted, distal end
first, into the lumen of the main member 104 and through the side
opening 204 until the flange 304 abuts the inner surface of side
opening 204.
[0108] When the flange 304 abuts the inner surface of the main
member at the side opening 204, the flange 304 may be secured to
the main member 104 in any suitable manner. For example, the main
member 104 may be advanced down the length of the 16 mm outer
diameter mandrel, trapping the four equal sections comprising the
flange 304 between the mandrel and the main member 104. The main
member 104 and the side-branch member 106, via flange 304, are then
bonded together, for example thermally, at the side opening 204,
such as via a soldering iron. The bonding, however, may be
performed using any suitable mechanism or techniques, such as, but
not limited to, sutures or adhesives.
[0109] The prosthetic conduit 102 may be configured in any suitable
manner for delivery. In the present embodiment, the side-branch
member 106 and the main member 104 are connected and placed in a
compact configuration for delivery, for example with the
side-branch member 106 inside of the main member 104. A delivery
and/or a deployment system, either wholly or in part, may also be
added to the assembled prosthetic conduit 102.
[0110] The prosthetic conduit 102 may be configured for delivery
and deployment in any appropriate manner. For example, the
side-branch member 106 may be disposed inside the w main member 104
to facilitate placement (step 1446). In the present embodiment, a
1.2 mm diameter stainless steel rod is inserted coaxially within
the side-branch member 106. To enable eversion of the side-branch
member 106, the side-branch member is suitably constrained from
dilation or longitudinal compression, such as by helically
overwrapping the side-branch member 106 to the rod using porous
polytetrafluoroethylene film. The overwrap suitably begins on the
1.2 mm diameter rod adjacent to the distal end 306 of the
side-branch member 106 and ends adjacent to the proximal end 308 of
the side-branch member 106. In the present embodiment, since all
regions of the side-branch member 106 with exception to the region
encompassing side-branch stent 112 have an inner diameter larger
than 1.2 mm, care is taken during the application of the overwrap
film, creating lengthwise folds and avoiding twisting of the
side-branch member 106. Alternatively, to enable folding, the
side-branch member 106 may be covered with an elastomeric tube of
appropriate inner diameter and thickness.
[0111] The 1.2 mm diameter rod is then suitably used to push the
side-branch member 106 into the lumen of the main member 104,
causing the side-branch member to evert onto itself until a desired
portion, such as the entire length of side-branch member 106,
resides within the lumen of the main member 104. During the
eversion process, the porous polytetrafluoroethylene film may be
removed as necessary. Alternatively, if an elastomeric tube is
used, the tube may be of sufficient length to evert over itself,
leaving a free end extending beyond the distal end of the
side-branch member 106. During the eversion of the side-branch
member 106 into the main member 104, the elastomeric tube could be
removed via eversion in the opposite direction. Once the
side-branch member 106 is completely everted, the remaining
overwrap film and the 1.2 mm diameter rod may be removed.
[0112] In the illustrative embodiment, the side-branch balloon
catheter 406 is positioned within the side-branch member after the
eversion process is completed. In an alternative embodiment, a
side-branch guidewire 410 may be positioned within the everted
side-branch member 106. In such an embodiment, the side-branch
balloon catheter 406 may or may not be included within the
side-branch member 106.
[0113] In another alternative embodiment, the side-branch balloon
catheter 406 may be placed coaxially within the side-branch member
106, in lieu of the 1.2 mm diameter rod. The side-branch balloon
catheter 406 may be located at any suitable place along the length
of the side-branch member 106, such as at the distal end, suitably
in registry with the side-branch stent 112. The side-branch balloon
catheter 406 may then be releasably attached to the side-branch
member 106. With the side-branch balloon catheter 406 releasably
attached to the side-branch member 106, the side-branch balloon
catheter 406 in cooperation with polytetrafluoroethylene film or
any suitable mechanism may be used to evert the side-branch member
106 within the main member 104. A side-branch guidewire 410 placed
within the guidewire lumen of the side-branch balloon catheter 406
may also be included.
[0114] In yet another alternative embodiment, a guiding catheter,
or a deployment tube similar to a guiding catheter, may be placed
coaxially within the side-branch member 106 in lieu of the 1.2 mm
diameter rod. If the side-branch member 106 is equipped with the
side-branch stent 112, the guiding catheter or tube may be
positioned such that its distal end abuts the proximal end of the
side-branch stent 112. When so positioned, the side-branch stent
112 may be configured with an inner diameter approximately equal to
that of the guiding catheter or deployment tube. In such an
arrangement, the guiding catheter or deployment tube may provide a
well-defined passageway for other devices and may aid in the
extension of the side-branch member 106. Alternatively, with the
guiding catheter or deployment tube positioned as described, the
distal end may be releasably attached to the graft component, for
example by an adhesive, thermal bond, or other suitable method.
[0115] Regardless of how the guiding catheter or tube is positioned
within the side-branch member 106, once it is in the desired
location, the process of everting the side-branch member into the
main member may be completed by using the guiding catheter or tube
in cooperation with polytetrafluoroethylene film or any suitable
mechanism. If additional support is required during eversion, a rod
for example may be placed within the guiding catheter or tube. Once
the eversion process is completed, other devices may be placed
within the guiding catheter or tube or within the side-branch
member 106.
[0116] The prosthetic conduit 102 may further be equipped with
additional delivery system and/or deployment system components, or
may otherwise be prepared for delivery and deployment. For example,
the side-branch balloon catheter 406 may be inserted coaxially
within the distal end of the side-branch member 106 and releasably
attached to the side-branch member 106. Further, the prosthetic
conduit 102 may receive the main balloon catheter 400 or be placed
within a constraining sheath 902. For example, the prosthetic
conduit 102 may be suitably folded into a compact configuration and
placed in a constraining sheath 902. The push tube 900 may then be
placed within the constraining sheath 902. If required, the
side-branch balloon 406 may be removed during the folding process,
and repositioned when convenient. Any suitable arrangement of a
constraining sheath 902, push tube 900, side-branch balloon 406,
and other components may be employed. In some embodiments,
particularly if the push tube 900 is adapted to extend within the
main member 104, the prosthetic conduit 102 and the push tube 900
may be arranged prior to placement within the constraining sheath
902.
[0117] The various embodiments of the present invention may be
delivered and installed by any known method, using any combination
of devices. For example, the delivery system may comprise any
combination of suitable introducer sheaths, guidewires, balloon
catheters, guiding catheters, deployment tubes, constraining
sleeves, push tubes, and/or any other accessory in any suitable
arrangement.
EXAMPLE
[0118] To demonstrate the characteristics of a preferred embodiment
of a circumferentially distensible tube, a 1.2 mm inner diameter
film-tube was created using essentially the same process as
described above. A 230.times.45 mm rectangular piece was cut from
Solupor 7P03A microporous polyethylene film and wrapped around the
circumference of a 4 mm outer diameter stainless steel mandrel.
With the wrapping complete, both ends of the 230 mm long wrapped
film section were secured to the mandrel with wire. Porous
polytetrafluoroethylene film was helically wrapped over the 230 mm
long wrapped film section, covering the section entirely. The 4 mm
mandrel was then placed in an air convection oven set at
143.degree. C. for 7.5 minutes and subsequently removed and allowed
to cool. Once cool, the helically wrapped porous
polytetrafluoroethylene film as well as the securing wire were
removed and discarded. The resulting 4 mm inner diameter
polyethylene tube was then removed from the 4 mm outer diameter
mandrel and cut into two equal lengths.
[0119] Next, pen marks were placed on one of the 4 mm inner
diameter film-tubes, and the film-tube was secured to a sliding
mandrel mechanism. In this instance, the sliding mandrel mechanism
had a 1.1 mm diameter rod. The entire assembly was heated in an air
convection oven set at 150.degree. C. for one minute, and the
film-tube was then carefully stretched until the interval between
the two pen marks (originally spaced at 70 mm) was approximately
141 mm. The stretching caused the film-tube to reduce in diameter,
substantially contacting the 1.1 mm rod. The film-tube was then
allowed to cool and removed from the sliding mandrel mechanism.
[0120] The film-tube was then manually distended over 3.8 and 4 mm
outer diameter tapered mandrels. The approximate lengths separating
the two pen marks on the film-tube while on the 3.8 and 4 mm outer
diameter tapered mandrels were 85 and 80 mm respectively. With the
distention completed, and the film-tube removed from the 4 mm
tapered mandrel, the film-tube was secured to the linear slide and
stretched until the distance between the two pen marks was
approximately 154 mm. With the stretching complete, the film-tube
was allowed to remain clamped within the linear slide mechanism for
at least of 5 minutes at ambient temperature.
[0121] The film-tube was then manually fitted coaxially over a 1.2
mm diameter stainless steel rod. The processing of the film-tube
was then completed following the steps as previously described. As
previously discussed, the small corrugations were formed within the
finished tube, tending to allow the tube to be bent without
kinking. Additionally, the completed film-tube was readily
circumferentially distensible without significant length change
(foreshortening) and without significant diameter change post
distention (recoil). The 1.2 mm inner diameter film-tube was
capable of circumferential distention to an inner diameter of
approximately 4 mm.
[0122] To provide comparative data, a nondistensible film-tube was
created. The nondistensible film-tube was made with approximately
the same number of film layers and the same film used to make the
1.2 mm circumferentially distensible film-tube above, but was not
processed to render it circumferentially distensible or to exhibit
enhanced flexibility.
[0123] More particularly, a 200.times.17 mm rectangular piece of
Solupor 7P03A microporous polyethylene film was cut and wrapped
around the circumference of a 1.5 mm diameter stainless steel rod.
In this case, the circumference of the 1.5 mm rod was approximately
4.7 mm, so to achieve an approximate film thickness of three layers
after wrapping, one side of the rectangular piece was cut to a
dimension of 17 mm, providing approximately 3 mm extra film length
for overlap. With the wrapping complete, both ends of the 200 mm
long wrapped film section were secured to the rod with wire and the
section was helically wrapped with porous polytetrafluoroethylene
film. The 1.5 mm rod was then placed in an air convection oven set
at 143.degree. C. for 3 minutes and subsequently removed and
allowed to cool. Once cool, the helically wrapped porous
polytetrafluoroethylene film as well as the securing wire were
removed and discarded. The 1.5 mm inner diameter polyethylene tube
was then removed from the 1.5 mm diameter rod. The 1.5 mm inner
diameter polyethylene film-tube did not possess any significant
circumferential distensibility, nor did it possess any enhanced
flexibility. If desired, however, enhanced flexibility may be
imparted to such non-distensible tubes by following process steps
similar to those previously described for helically wrapping,
warming, and longitudinal compression.
[0124] The distensibility characteristics for the distensible and
the non-distensible tube were measured for comparison. A 16.5 mm
long section was cut from the 1.2 mm inner diameter
circumferentially distensible film-tube. The section was distended
slightly by fitting it coaxially over a 1.5 mm diameter rod. The
16.5 mm long section of tube was then coaxially fitted over an
angioplasty balloon with a nominal length of 15 mm, and a nominal
diameter of 4 mm. The distention of the tube to a 1.5 mm inner
diameter was required so that the tube could be easily placed onto
the uninflated balloon without any change in length. Also, a length
of 16.5 mm was utilized so as to cover the entire working length of
the balloon such that the balloon edges (shoulders) did not inflate
at a faster rate than the center. Inflation of the shoulders at a
faster rate than the balloon center causes the shoulders at each
end of the balloon to bulge and longitudinally compress the length
of tube. Such longitudinal compression not only changes the length,
but also changes the distensibility characteristics of the tube.
This adverse interaction is caused by a mismatch between the length
of the balloon and the length of the tube being distended by the
balloon. Thus, a length of 16.5 mm successfully matched the tube
length to the balloon length and avoided such adverse
interactions.
[0125] With the tube fitted coaxially onto and centered along the
length of the uninflated balloon, digital calipers were used to
measure the outer diameter of the tube. The balloon was then
inflated at ambient temperature using a hand-held inflation device
in approximately 0.1 MPa (1 atm) increments and the outer diameter
of the tube was measured at each increment until a pressure of 1.6
MPa (16 atm) was achieved. Once the 1.6 MPa inflation pressure was
achieved and the final outer diameter measurement was completed,
the balloon was deflated and the length of the tube was measured
again using digital calipers.
[0126] The difference between the length of the tube prior to
distention and the length of the tube after distention is the
amount of foreshortening undergone by the tube. The balloon was
carefully repacked into the protective packaging sleeve that was
provided by the manufacturer and the same test procedure and data
collection were repeated on the 1.5 mm non-distensible tube. The
recorded outer diameter data were used to create a plot (FIG. 15)
of tube outer diameter as a function of inflation pressure.
[0127] FIG. 15 shows a plot of tube outer diameter as a function of
inflation pressure for both the distensible and the non-distensible
tube. The distensible tube generally increases in diameter with
increasing inflation pressure. The diameter increase tends to
reduce once the tube has reached outer diameters above
approximately 3.75 mm, signifying that the tube is approaching the
maximum amount of distention that can be achieved without the
application of extremely high inflation pressures. The distensible
tube reaches an outer diameter of approximately 4 mm under 1.6 MPa
(16 atm) inflation pressure.
[0128] FIG. 15 includes outer diameter data for the balloon
catheter only. These data are provided within the instructions for
use of the balloon catheter, and are included in FIG. 15 to show
that the outer diameter of the balloon catheter alone (as a
function of inflation pressure) is greater than that of the
distensible tube during distention by the balloon catheter. Thus,
the distensible tube is limiting the outer diameter of the balloon
catheter during inflation. Note that the data provided within the
instructions for use of the balloon catheter range only from 0.2 to
1.6 MPa (2 to 16 atm). FIG. 15 also shows the distensibility
characteristics of the non-distensible tube. The diameter of the
non-distensible tube remains fairly constant and is relatively
unchanged by the inflation pressure imparted to it via the balloon
catheter.
[0129] Prior to distention, as stated above, the length of the
distensible tube was 16.5 mm. The length of the distensible tube
after distention was measured to be approximately 15.7 mm,
resulting in approximately 0.8 mm of foreshortening. Dividing the
0.8 mm foreshortening value by the 16.5 mm length prior to
distention, and converting to a percentage yields a foreshortening
percentage of approximately 4.8 percent. Similarly, the length of
the non-distensible tube after distention (although the tube did
not actually undergo a substantial change in diameter) was measured
to be 16.1 mm, yielding a foreshortening value of 0.4 mm or
approximately 2.4 percent. In the case of the non-distensible tube,
the change in length was apparently due primarily to the shoulders
of the balloon bulging against the ends of the tube and causing the
slight length reduction.
[0130] To determine the recoil characteristics of the distensible
1.2 mm inner diameter tube, the tube was carefully fitted over a
1.5 mm diameter rod, causing a 25% increase in diameter. The tube
was then removed from the rod and left undisturbed for 30 minutes.
After the passing of 30 minutes, the tube was pushed back onto the
1.5 mm rod by carefully grasping one end of the tube and pushing
the other end of the tube onto the rod. An approximately 6 mm
length of tube was pushed onto the 1.5 mm diameter rod before the
tube buckled and could be pushed onto the rod no further. Because
the tube could be fitted onto the 1.5 mm rod at least partially,
there is indication of little to no recoil (or change in
diameter).
[0131] The same tube is then studied for flexibility or kink
resistance. The tube was carefully wrapped around the circumference
of an 11 mm outer diameter mandrel with no indication of gross
buckling of the tube. The tube was then released from the mandrel,
and rather than returning to its original substantially straight
configuration, it remained curved, in a semi-circular shape having
a radius of approximately 15 mm. To provide comparative data, a
length of the 1.5 mm non-distensible tube was wrapped around the
circumference of the same 11 mm outer diameter mandrel. The
non-distensible tube exhibited various points where kinking (gross
buckling) occurred. When released from the mandrel, the
non-distensible tube returned to a substantially straight
configuration.
[0132] To further demonstrate the recoil characteristics of the
distensible 1.2 mm inner diameter tube, a new length of tube was
tested, in a manner similar to that described above. In this case,
rather than distending the tube 25%, a length of the tube was
distended over the 4 mm tapered mandrel. The tube was then removed
from the tapered mandrel and left undisturbed for 30 minutes. After
30 minutes, attempts were made to push the tube onto a 4 mm
(non-tapered) mandrel by carefully grasping the undistended end of
the tube and pushing the distended end of the tube onto the
mandrel. The tube, however, having undergone some recoil, did not
fit onto the 4 mm mandrel.
[0133] Similar attempts were then made to coaxially fit the tube
onto a 3.8 mm (non-tapered) mandrel. The section of the tube, which
was distended to a 4 mm inner diameter, fit over the 3.8 mm mandrel
easily, indicating that the inner diameter of the tube was then
approximately 3.8 mm. Thus, the distended diameter of the tube was
4 mm and the recoil diameter of the tube was approximately 3.8 mm,
resulting in a recoil value of approximately 0.2 mm. Dividing the
approximate recoil value of 0.2 mm by the distended diameter of 4
mm, and converting to a percentage yields a percent recoil value of
approximately 5 percent.
[0134] Accordingly, a prosthetic conduit according to various
aspects of the present invention may be suitable for the treatment
of both aneurysmal and occlusive vascular disease within coronary
and peripheral blood vessels, as well as within the
neurovasculature, and various other bodily conduits. The prosthetic
conduit facilitates endoluminally treating aneurysmal vessels while
maintaining normal blood flow to a side-branch vessel originating
along the length of the aneurysm. Thus, the prosthetic conduit
tends to alleviate the potential for ischemic complications in
other bodily locations, and also tends to inhibit the situation of
retrograde blood flow through the side-branch vessel, facilitating
the aneurysm exclusion process. The prosthetic conduit also
provides, by virtue of the graft material, a physical barrier that
impedes reproliferation of disease into the lumen of the treated
blood vessel. Moreover, the prosthetic conduit provides a preformed
bifurcated junction, obviating highly accurate placement as
required during the formation of a bifurcation using two stents.
The prosthetic conduit including the main member and side-branch
member grafts also tends to control redistribution of plaque at the
side-branch and reduce the chance of inadvertent blockage due to
plaque movement.
[0135] In accordance with various other aspects of the present
invention, the prosthetic conduit provides several advantages and
characteristics. For example, such a prosthetic conduit may allow
relative ease of sizing, and may accommodate a range of main and
side-branch vessel diameters. The prosthetic conduit may also offer
a high degree of flexibility, bending substantially without
kinking, and thus having the ability to conform to a variety of
bifurcation geometries. Additionally, the prosthetic conduit may be
installed through a singular vascular access site. Also, the
prosthetic conduit may include radiopaque markers, or may be at
least partially constructed of materials that are easily visualized
radiographically, facilitating the installation process. The
prosthetic conduit may also be installed utilizing conventional,
non-specialized tools and devices for vascular surgery,
interventional radiology, interventional cardiology, and the
like.
[0136] The present invention has been described above with
reference to various preferred embodiments. However, changes and
modifications may be made to various exemplary embodiments without
departing from the scope of the present invention. For example,
various combinations of the main members 104 and one or more
side-branch members 106 may be provided. Further, various changes
in the configurations of the main member 104 and the side-branch
member 106, for example various combinations of stents and grafts
and various materials, may be provided. These and other changes or
modifications are intended to be included within the scope of the
present invention as set forth in the appended claims.
* * * * *