Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Arterial prosthesis – Stent combined with surgical delivery system
Reexamination Certificate
1999-01-13
2001-02-13
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Arterial prosthesis
Stent combined with surgical delivery system
C623S001150
Reexamination Certificate
active
06187034
ABSTRACT:
FIELD OF THE INVENTION
The following invention relates to surgical stents for implantation into a body lumen such as an artery to support the lumen. More particularly, this invention relates to surgical stents which are highly flexible and can be readily adjusted and customized to match particular contour characteristics of the body lumen and the particular treatment needs for the body lumen at the implantation site.
BACKGROUND OF THE INVENTION
Surgical stents have long been known which can be surgically implanted into a body lumen, such as an artery, to reinforce, support, repair or otherwise enhance the performance of the lumen. For instance, in cardiovascular surgery it is often desirable to place a stent in the coronary artery at a location where the artery is damaged or is susceptible to collapse. The stent, once in place, reinforces that portion of the artery allowing normal blood flow to occur through the artery. One form of stent which is particularly desirable for implantation in arteries and other body lumens is a cylindrical stent which can be radially expanded from a first smaller diameter to a second larger diameter. Such radially expandable stents can be inserted into the artery by being located on a catheter and fed internally through the arterial pathways of the patient until the unexpanded stent is located where desired. The catheter is fitted with a balloon or other expansion mechanism which exerts a radial pressure outward on the stent causing the stent to expand radially to a larger diameter. Such expandable stents exhibit sufficient rigidity after being expanded that they will remain expanded after the balloon has been removed.
Radially expandable stents come in a variety of different configurations to provide optimal performance in various different particular circumstances. For instance, the patents to Lau (U.S. Pat. Nos. 5,514,154, 5,421,955, and 5,242,399), Baracci (U.S. Pat. No. 5,531,741), Frantzen (U.S. Pat. Nos. 5,718,713, 5,741,327, 5,746,691), Gaterud (U.S. Pat. No. 5,522,882), Gianturco (U.S. Pat. Nos. 5,507,771 and 5,314,444), Termin (U.S. Pat. No. 5,496,277), Lane (U.S. Pat. No. 5,494,029), Maeda (U.S. Pat. No. 5,507,767), Marin (U.S. Pat. No. 5,443,477), Khosravi (U.S. Pat. No. 5,441,515), Jessen (U.S. Pat. No. 5,425,739), Hickle (U.S. Pat. No. 5,139,480), Schatz (U.S. Pat. No. 5,195,984), Fordenbacher (U.S. Pat. No. 5,549,662), and Wiktor (U.S. Pat. No. 5,133,732), each include some form of radially expandable stent for implantation into a body lumen. Other prior art stents are compiled in the Handbook of Coronary Stents, Second Edition, produced by the Rotterdam Thoraxcenter Interventional Cardiology Group.
Most of these prior art stents suffer from undesirable axial contraction when radially expanded. Stents can be made to resist axial contraction upon radial expansion by including axial elements therein extending continuously from a first end of the stent to a second end of the stent. However, such continuous axial elements tend to make the stent stiff and exhibit less flexibility characteristics than needed to allow the stent to be easily passed through tortuous arterial pathways or other tightly curving body lumens effectively. Some of these prior art stents, such as the stents described in the patents to Frantzen resist axial contraction upon radial expansion by locating axial elements offset from each other and within troughs of adjacent circumferential elements. While flexibility does improve somewhat by offsetting such axial elements, additional flexibility is often needed.
In addition to flexibility drawbacks, known prior art stents typically are provided with a pre-configured contour having various different pre-radial expansion and post radial expansion diameters. These prior art stents have other non-variable predetermined characteristics such as strength characteristics, radiopacity characteristics, biocompatibility characteristics, flexibility characteristics and axial length characteristics. Body lumens in which stent implantation is indicated can vary in a variety of different ways. Hence, pre-configured stents are not always provided with a contour and other characteristics which optimally match the needs of the body lumen where implantation is desired. Accordingly, a need exists for a stent which can be custom configured by the surgeon or custom ordered by the surgeon for ready assembly by a qualified technician to the surgeon's specifications to provide the treatment desired within the body lumen where implantation of the stent is to occur.
Also, stent flexibility of known prior art stents is not well matched with flexibility of stent delivery and expansion balloons. Rather, known stent delivery and expansion balloons typically are provided with a cylindrical contour which can be inflated and radially expanded to just a few different radial sizes. Accordingly, a need exists for a balloon which can be configured to have flexibility and radial expansion characteristics which more closely match the flexibility and radial expansion characteristics of stents with which the balloon is mated.
SUMMARY OF THE INVENTION
The segmented stent of this invention includes a series of circumferential elements axially spaced from each other along a central axis of the stent. Each circumferential element is configured so that it can be expanded radially from a first collapsed diameter to a second expanded diameter. This expanded diameter can either be a diameter of maximum radial expansion where the circumferential element is expanded nearly to the point where it is circular in form or can be limited to an intermediate amount where the circumferential elements still include an undulating form as the circumferential elements circumscribe the central axis.
Gaps are located between adjacent circumferential elements which space the circumferential elements axially away from each other. Some of the gaps are spanned gaps that include axial elements joining a pair of circumferential elements adjacent the spanned gaps. Other gaps are unspanned gaps with no axial elements provided between the pair of circumferential elements adjacent the unspanned gaps. Hence, the stent is segmented into separate segments with unspanned gaps located between each of the segments and spacing the segments axially away from each other. The unspanned gaps in the segmented stent provide areas where the stent can be flexed to cause the central axis of the stent to bend without resistance. The segments maintain their form both before and after radial expansion without any appreciable flexing or axial length adjustment.
Because the individual segments of the stent are not actually connected together, the stent can be made up of a customizable different number of segments to increase or decrease an overall axial length of the stent. Also, segments of differing maximum diameters of radial expansion, differing radiopacity, differing strength or other differing characteristics can be matched together as segments in a common segmented stent which will have the contour and performance characteristics desired by the surgeon for implantation into the body lumen.
The segmented stent is preferably part of a flexible stent delivery system which additionally includes a flexible balloon particularly configured to support the segments of the stent before and during radial expansion of the stent. The balloon includes cylindrical sections spaced axially from each other by notches. The notches define regions on the balloon where flexing of the balloon is more readily facilitated than at the cylindrical sections. The segments of the segmented stent are oriented so that one segment is adjacent each cylindrical section and so that the unspanned gaps are aligned with the notches. Hence, regions on the stent where flexibility is provided are aligned with regions on the flexible balloon where flexibility is provided.
OBJECTS OF THE INVENTION
Accordingly, a primary object of the present invention is to provide a stent of high flexibility which includes separate segments spaced axially from ad
Heisler & Associates
Jackson Suzette J.
Willse David H.
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