Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent structure
Reexamination Certificate
1999-07-06
2001-07-24
O'Connor, Cary E. (Department: 3732)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent structure
Reexamination Certificate
active
06264685
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to prosthetic devices for use within a body passageway or duct and, more particularly, to an intraluminal stent for repairing blood vessels. Still more particularly, the present invention relates to flexible intraluminal stents having high radial strength.
BACKGROUND OF THE INVENTION
As its name implies, intraluminal stents are devices which are implantable within a body lumen for treating abnormal conditions within the lumen. For example, these devices have found use in maintaining the patency of collapsing and partially occluded blood vessels, particularly to prevent acute closure and restenosis after a vessel has been enlarged by a percutaneous transluminal coronary angioplasty procedure. These devices have also been used to reinforce other body lumens, such as the urinary tract, the bile tract, the intestinal tract and the like. They have found further use as fixation devices for holding intraluminal prosthetic grafts open and in place in the repair of weakened or abnormally dilated portions of a blood vessel.
Conventional stents are formed from a wire or the like which has been bent back and forth in a generally zig-zag pattern in a longitudinal direction and then wound in a circumferential direction transverse to the longitudinal direction to form one or more loops of a predetermined circumference. Typically, the stent is radially expandable from a collapsed condition in which the circumference of the stent is minimized so that the stent can be delivered intraluminally, to an expanded condition in which the circumference of the stent approaches the predetermined circumference to support and reinforce the lumen. The stent is normally held in the collapsed condition by a catheter during intraluminal delivery to the repair site. Once properly located, the stent is removed from the catheter and radially expanded until its circumference firmly contacts the interior wall of the lumen to hold the stent in this implanted location. This radial expansion of the stent may be effected by the dilation of an angioplasty balloon placed axially within the stent. Alternatively, the stent may be made from a shape memory metal, whereby the stent will automatically assume its expanded circumference as its temperature increases upon implantation at the desired location.
Regardless of the mechanism by which the stent is placed in its expanded condition, an important attribute of the stent is its ability to provide radial support. This capability is a concern not only where the stent is being used to maintain the patency of the lumen in which it is located, but also where the stent is being used in conjunction with a prosthetic graft to keep the graft open and to hold it at the location at which it was implanted. The ability of the stent to provide this radial support, particularly over long periods of time, is directly related to the hoop or radial strength which the stent exhibits. For conventional stents having a generally zig-zag configuration, the hoop strength depends primarily upon the number of bends along the circumference of the stent, the elastic properties of the wire from which the stent is formed, and the diameter of the wire. Currently available stents generally have a sufficient hoop strength for use in small caliber vessels and the like because they require a relatively small number of bends along their circumference. However, where the stents have a larger circumference for use in larger caliber vessels, such as the aorta, they include a much larger number of bends and thus exhibit a lower hoop strength which is generally insufficient to maintain the patency of these larger lumens and to fix larger circumference grafts in place therein. A simple approach to increasing the hoop strength of these stents without changing the material from which they are formed is to form the stent from a larger diameter wire. Although this approach may produce satisfactory hoop strengths, it has the negative affect of increasing the bulk of the stent and thus contributes to delivery problems.
U.S. Pat. No. 5,630,829, issued to Lauterjung, discloses a stent having sufficient hoop strength to provide long term radial support and graft fixation in large caliber arteries and other body lumens. More particularly, the stent therein disclosed exhibits high hoop strength with little to no increase in bulk over conventional stents and which, therefore, does not contribute to difficulties in intraluminal delivery.
There exists a need however, for a high hoop strength stent, as described above, that is highly flexible, and thus capable of matching the anatomical geometry of the patient.
SUMMARY OF THE INVENTION
Accordingly, the present invention comprises an intraluminal stent, as disclosed in U.S. Pat. No. 5,630,829, said reference being herein incorporated by reference, further including the incorporation of one or more flex cells for enhancing the flexibility of the stent. The stent includes a plurality of elongated members having first and second ends and extending in a circumferential direction around an axis and curving in two opposite directions transverse to the circumferential direction. Each of the elongated members may be curved over substantially its entire extent, preferably so that the curved portions define an arc of a circle. The elongated members are joined to one another on their first ends forming cusps pointing in opposite axial directions. The cusps are movable in opposite axial directions between an expanded condition, in which the opposed cusps are relatively close to one another and the elongated members define an expanded circumference, and a collapsed condition, in which the opposed cusps are relatively distant to one another and the elongated members define a collapsed circumference which is smaller than the expanded circumference. The stent may be formed as a single loop, as a plurality of loops extending in an axial direction, or as a helix. The flex cell may comprise a member in the shape of a U, V, a parallelogram, or a similar shape. Said flex cell has two ends, or in the case of the parallelogram two vertices, each of which is attached to the adjacent second end of a neighboring elongated member.
REFERENCES:
patent: 5449373 (1995-09-01), Pinchasik et al.
patent: 5733303 (1998-03-01), Israel et al.
patent: 5755781 (1998-05-01), Jayaraman
patent: 5824036 (1998-10-01), Lautherjung
Datascope Investment Corp.
O'Connor Cary E.
Ronai Abraham P.
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