Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1998-03-31
2001-07-24
Milano, Michael J. (Department: 2165)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
Reexamination Certificate
active
06264689
ABSTRACT:
BACKGROUND OF THE INVENTION
Implantable medical prostheses, such as stents, are placed within the body to maintain and/or treat a body lumen that has been impaired or occluded, for example, by a tumor. The stent can be formed of strands of material formed into a tube and are usually delivered into the body lumen using a catheter. The catheter carries the stent to the desired site and the stent is released from the catheter and expands to engage the inner surface of the lumen.
A self-expanding stent can be made of elastic materials. These are held in a compressed condition during catheter delivery by, for example, a sheath that covers the compressed stent. Upon reaching the desired site, the sheath constraining the stent is pulled proximally, while the stent is held in the desired position such that the stent expands.
There are both self-expanding and non-self-expanding stents. The self-expanding type of device is made with a material having an elastic restoring force, whereas a non-self-expanding stent is often made with elastic, plastically deformable material. It is positioned over a mechanical expander, such as a balloon, which can be inflated to force the prosthesis radially outward once the desired site is reached.
SUMMARY OF THE INVENTION
In a preferred embodiment, the invention features an implantable medical stent having a low profile during delivery. The stent is a tubular body with a body wall structure having a geometric pattern of cells defined by a series of elongated strands extending to regions of intersection. An example of a stent having a cell shape in accordance with the invention can be found in U.S. Ser. No. 08/743,395, filed Nov. 4, 1996, the entire contents of which is incorporated herein by reference. This stent cell structure utilized helically wrapped joints to connect the different strands to form a tubular body.
A limitation on the use of the helically joined stent involved the minimum constrained diameter of the stent during delivery. Because of the helically wrapped joints abutting one another along a given circumference, the minimum constrained diameter of the stent was 9 French (3 mm). For example, the length of the helically wrapped joint for a strand having a diameter of 0.006 inches in the constrained position is 0.045 inches. For a five cell structure having five helically twisted abutting joints, this results in a constrained circumference of 0.228 inches with a diameter of 0.072 inches. However, there are many applications in which it is necessary to achieve a smaller constrained diameter to provide delivery, for example, through smaller lumens within the vascular system, to reduce trauma during percutaneous delivery, or to provide endoscopic delivery through small diameter channels of endoscopes.
To achieve a smaller constrained diameter of 8 French or less, for example, a preferred embodiment of the invention replaces one or more of the helically wrapped joints along any given circumference with a simple crossed joint in which one strand crosses either above or below a second strand. Thus, the strands at a crossed joint can move more freely relative to each other, but this structure reduces the minimum circumference as the length of one or more helically twisted joints has been removed. This can reduce the constrained diameter by 50%.
In another preferred embodiment of the invention, the stent can include a first tubular body made from a first group of strands and a second tubular body surrounding the first tubular body and made from a second group of strands. This type of structure can be used to fabricate a low-profile device having sufficient radial expansion force for a self-expanding stent without a substantial change in foreshortening. This embodiment can include, for example, three or four helically wrapped joints along any circumference of the first and second tubular bodies in which the joints of the two bodies are offset in the constrained state. This embodiment also significantly improves the ratio of the displayed diameter to the constrained diameter.
The strands of the first group can have a different shape, diameter or material from the strands of the second group such that the inner body has a larger radial restoring force than the outer body and can thereby impart the outward force to the outer body.
In one embodiment, the strands of the inner body can be thicker than the strands of the outer body and can be interleaved with the outer body along the entire length of the stent. In another preferred embodiment, the inner and outer bodies can be interlocked at one or both ends. This can permit the use of a cover between the inner and outer bodies along a certain portion of the stent. The use of the cover can enhance epithialization between the wall of the lumen and the outer body, reduce migration of the stent in certain applications and can prevent tumor in-growth. The cover can also provide a supporting matrix for drug delivery.
REFERENCES:
patent: 3868956 (1975-03-01), Alfidi et al.
patent: 4776337 (1988-10-01), Palmaz
patent: 4990151 (1991-02-01), Wallstén
patent: 4994071 (1991-02-01), MacGregor
patent: 5015253 (1991-05-01), MacGregor
patent: 5019090 (1991-05-01), Pinchuk
patent: 5026377 (1991-06-01), Burton et al.
patent: 5061275 (1991-10-01), Wallstén et al.
patent: 5064435 (1991-11-01), Porter
patent: 5133732 (1992-07-01), Wiktor
patent: 5159920 (1992-11-01), Condon et al.
patent: 5171262 (1992-12-01), MacGregor
patent: 5201901 (1993-04-01), Harada et al.
patent: 5211658 (1993-05-01), Clouse
patent: 5256158 (1993-10-01), Tolkoff et al.
patent: 5282823 (1994-02-01), Schwartz et al.
patent: 5304220 (1994-04-01), Maginot
patent: 5366504 (1994-11-01), Anderson
patent: 5382259 (1995-01-01), Phelps et al.
patent: 5405377 (1995-04-01), Cragg
patent: 5405378 (1995-04-01), Strecker
patent: 5411507 (1995-05-01), Heckele
patent: 5484444 (1996-01-01), Braunschweiler et al.
patent: 5534007 (1996-07-01), St. Germain et al.
patent: 5534287 (1996-07-01), Lukic
patent: 5571167 (1996-11-01), Maginot
patent: 5603698 (1997-02-01), Roberts et al.
patent: 5607466 (1997-03-01), Imbert et al.
patent: 5643339 (1997-07-01), Kavteldze
patent: 5645559 (1997-07-01), Hachtman et al.
patent: 5653727 (1997-08-01), Wiktor
patent: 5667523 (1997-09-01), Bynon
patent: 5725571 (1998-03-01), Imbert et al.
patent: 5725572 (1998-03-01), Cam
patent: 5728150 (1998-03-01), McDonald et al.
patent: 5728158 (1998-03-01), Lau et al.
patent: 5800519 (1998-09-01), Sandock
patent: 5843168 (1998-12-01), Dang
patent: 5876432 (1999-03-01), Lau
patent: 5928280 (1999-07-01), Hansen et al.
patent: 0 744 163 A1 (1996-11-01), None
patent: 0 788 012 A2/A3 (1997-06-01), None
patent: 0 788 802 A2 (1997-08-01), None
patent: 0 804 934 A2 (1997-11-01), None
patent: 0 812 579 A1 (1997-12-01), None
patent: 894 505 A2 (1999-02-01), None
patent: 87/04935 (1987-08-01), None
patent: 94/00178 (1994-01-01), None
patent: 95/29646 (1995-11-01), None
patent: 96/32078 (1996-10-01), None
patent: 96/33677 (1996-10-01), None
patent: 96/41589 (1996-12-01), None
patent: 97/32456 (1997-09-01), None
Colgan Darragh
DiCarlo Paul
Hamilton Peter
Hamilton Brook Smith & Reynolds P.C.
Milano Michael J.
Scimed Life Systems Incorporated
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