Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
2001-09-10
2004-02-03
Milano, Michael J. (Department: 3731)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
C606S200000, C623S001350
Reexamination Certificate
active
06685738
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to endoluminal stents, grafts, and/or prostheses and, more specifically, to braided stents adapted for deployment in branched lumina and processes for their manufacture.
BACKGROUND OF THE INVENTION
A stent is an elongated device used to support an intraluminal wall. In the case of a stenosis, a stent provides an unobstructed conduit for blood in the area of the stenosis. Such a stent may also have a prosthetic graft layer of fabric or covering lining the inside or outside thereof, such a covered stent being commonly referred to in the art as an intraluminal prosthesis, an endoluminal or endovascular graft (EVG), or a stent-graft.
A prosthesis may be used, for example, to treat a vascular aneurysm by removing the pressure on a weakened part of an artery so as to reduce the risk of rupture. Typically, a prosthesis is implanted in a blood vessel at the site of a stenosis or aneurysm endoluminally, i.e. by so-called “minimally invasive techniques” in which the prosthesis, restrained in a radially compressed configuration by a sheath or catheter, is delivered by a deployment system or “introducer” to the site where it is required. The introducer may enter the body through the patient's skin, or by a “cut down” technique in which the entry blood vessel is exposed by minor surgical means. When the introducer has been threaded into the body lumen to the prosthesis deployment location, the introducer is manipulated to cause the prosthesis to be ejected from the surrounding sheath or catheter in which it is restrained (or alternatively the surrounding sheath or catheter is retracted from the prosthesis), whereupon the prosthesis expands to a predetermined diameter at the deployment location, and the introducer is withdrawn. Stent expansion may be effected by spring elasticity, balloon expansion, or by the self-expansion of a thermally or stress-induced return of a memory material to a pre-conditioned expanded configuration.
Various types of stent architectures are known in the art, including many designs comprising a filament or number of filaments, such as a wire or wires, wound or braided into a particular configuration. Included among these wire stent configurations are braided stents, such as is described in U.S. Pat. No. 4,655,771 to Hans I. Wallsten and incorporated herein by reference, the '771 Wallsten patent being only one example of many variations of braided stents known in the art and thus not intended as a limitation of the invention described herein later. Braided stents tend to be very flexible, having the ability to be placed in tortuous anatomy and still maintain patency. The flexibility of braided stents make them particularly well-suited for treating aneurysms in the aorta, where the lumen of the vessel often becomes contorted and irregular both before and after placement of the stent. As noted in the '771 application, devices having braided architecture “may also be designed to act as a filter for thrombosis, for example by application in Vena Cava Interior to prevent the formation of lung emboliae.” The '771 application further includes as
FIG. 8
to that application (reproduced as
FIG. 18
in this application), a vena cava filter which is described in that application as follows (with the term “FIG.
18
” substituted for “FIG.
8
” in the original text, and elements “
853
” and “
854
” substituted for “
53
” and “
54
,” respectively, to avoid duplication of element numbers within this specification):
In [FIG.
18
] there is shown a modified embodiment of the flexible tubular body. In this embodiment the body consists of a cylindrical circular part [
853
] which at one end thereof changes to a diminishing part or end [
854
] also built up from thread elements. This device has been found to be suitable for use as a sieve or filter to prevent thrombosis. The device shown in [FIG.
18
] can be applied at the desired location within a blood vessel, for example Vena Cava Inferior, for the purpose of preventing lung emboly. Previously known filter means intended for application within blood vessels for the purpose of catching thrombosis are associated with the disadvantage that they are permanently attached in the blood vessel by pointed ends or latches or the like, positional correction or removal of the filter not being possible. An example of such device is described in U.S. Pat. No. 3,540,413. The device according to the present invention can be inserted into Vena Cava with great precision and it does not involve any risk for damages on surrounding vascular walls which is the case with known devices used today in surgery for the same purposes.
Among the many applications for stent-grafts is for deployment in bifurcated lumen, such as for repair of abdominal aortic aneurysms (AAA). Various stent-graft configurations are known in the art for bifurcated applications, including single-piece and modular designs, graft designs fully supported by stents, and graft designs only partially supported by stents. Referring now to
FIGS. 1A and 1B
, there are shown the components of a modular, non-braided, bifurcated, stent
10
for use with a fully-supported graft as is fully described in U.S. Pat. No. 5,609,627 to Goicoechea et al and adapted for implantation within the aorta of a human. By “fully-supported” it is meant that the graft is adapted to have stent structure underlying the graft throughout the entire length of the graft, as opposed to having extensive lengths of unsupported graft between anchoring stent portions, as will be described herein later.
As shown in
FIG. 1A
, stent
10
comprises a main body
12
which bifurcates into a first frustoconical leg transition
14
with a dependent first leg
16
, and a second frustoconical leg transition
18
. Second leg
20
is a modular component comprising a frustoconical part
22
adapted to interlock within second leg transition
18
, and a depending portion
24
. Frustoconical part
22
may have barbs
23
to help firmly connect second leg
20
to leg transition
18
. As shown in
FIG. 2
, such a bifurcated stent
10
is typically implanted within the vasculature such that the main body
12
and leg transitions
14
and
18
are positioned within the aorta main portion
26
and with the dependent first leg
16
and depending portion
24
of second leg
20
each positioned within respective iliac arteries
28
and
30
. Modular designs are also available wherein both legs are modular components. All of the bifurcated stents described herein, regardless of underlying structure, generally resemble the configuration shown in
FIG. 2
when fully implanted.
As shown in
FIGS. 1A and 1B
and as fully described in the '627 patent, the structure of stent
10
is a continuous wire zig-zag structure comprising a series of struts
32
joined at apices
34
and wound into hoops
36
, with abutting hoops joined together in some manner, such as with sutures, at abutting apices. One potential disadvantage of zig-zag stent architecture is that the apices of the zig-zag structure can rub against the graft, causing wear in the graft.
Modular, fully-supported, bifurcated stent-graft designs using braided architecture are also known. Such designs typically comprise a tubular stent that is crimped or pinched together in the middle or at one end to form a septum and two smaller lumina. These two lumina can then be used as sockets for the iliac sections. The braided stents have the advantage of being very adaptable to tortuous anatomy as compared to other stent architectures. The formation of the crimp, however, can cause metal cold-work and embrittlement in the stent wires and can result in bulkiness in the bifurcation region, requiring a relatively larger deployment profile than other designs.
To overcome the potential disadvantages of modular designs, it is also known to provide one-piece or “unitary” stent designs. Such known designs may be fully supported or only partially supported, such as by having anchoring stent portions o
Chouinard Paul F.
Haverkost Patrick A.
Peiffer Dennis A.
Roberts George T.
Ho Tan-Uyen T.
Milano Michael J.
RatnerPrestia
Sci-Med Life Systems, Inc.
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