Flexible Expandable Stent
A stent for implanting in the body to hold open a blood vessel includes cells with facing loops and the curved flexible links disposed and adapted to cooperate so that, when unexpanded, the stent can flex as it is moved through curved blood vessels to a site where it is to be expanded and so that, when the stent is expanded in a curved vessel, at that site, as compared to each other, cells on the outside of the curve are open in length, but narrow in width as compared to cells on the inside of the curve which are short in length but increased in width to result in a more constant stent cell area between the inside and the outside of the curve than would otherwise occur causing the stent, when coated with a medicine, to apply a more even dose to the inside wall of the lumen, avoiding the possibility that a toxic dose is supplied at one area while a less than effective dose is applied to another area.
This application is a continuation of Ser. No. 10/644,465 filed Aug. 20, 2003, which is a continuation of Ser. No. 09/337,629 filed Jun. 21, 1999, which is a continuation of Ser. No. 09/026,099 filed Feb. 19, 1998 (now U.S. Pat. No. 5,972,018), which is a continuation of Ser. No. 08/881,594 filed Jun. 24, 1997 (now U.S. Pat. No. 5,843,120), which is a continuation of Ser. No. 08/782,467 filed Jan. 10, 1997, now abandoned, which is a continuation of Ser. No. 08/457,354, filed May 31, 1995 (now U.S. Pat. No. 5,733,303), which is a continuation of Ser. No. 08/282,181 filed Jul. 28, 1994 (now abandoned) and a continuation-in-part of Ser. No. 08/213,272, filed Mar. 17, 1994 (now U.S. Pat. No. 5,449,373).
FIELD OF THE INVENTIONThe present invention relates generally to stents for implanting into a living body.
BACKGROUND OF THE INVENTIONVarious stents are known in the art wherein, for the present application, the term “stent” indicates a device, made of body-compatible material, which is utilized to widen a blood vessel, or other orifice in the body, and to maintain the resultant size of the lumen. Typically, the stent is delivered to the desired location in the body with an inflatable balloon and, when the balloon is inflated, the stem expands, thereby widening the orifice. Other mechanical devices which cause expansion of the stent are also utilized.
Exemplary patents in the field of stents formed of wire are: U.S. Pat. No. 5,019,090 to Pinchuk, U.S. Pat. No. 5,161,547 to Tower, U.S. Pat. No. 4,950,227 to Savin, et al, U.S. Pat. No. 5,314,472 to Fontaine, U.S. Pat No. 4,886,062 and U.S. Pat. No. 4,969,458 to Wiktor and U.S. Pat. No. 4,856,516 to Hillstead. Stems formed of cut stock metal are described in U.S. Pat. No. 4,733,665 to Palmaz, U.S. Pat. No. 4,762,128 to Rosenbluth, U.S. Pat. No. 5,102,417 to Palmaz and Schatz, U.S. Pat. No. 5,195,984 to Schatz and WO 91 FRO13820 to Meadox.
The stents described in U.S. Pat. No. 5,102,417 to Palmaz and Schatz have expandable tubular grafts connected together with a flexible connector. The grafts are formed of a plurality of slots disposed parallel to the longitudinal axis of the tube. The flexible connectors are helical connectors. Since the tubular grafts are relatively rigid, the flexible connectors are needed so that the stents can bend when being fed through a curved blood vessel. When the stents of U.S. Pat. No. 5,102,417 expand, the grafts expand radially and, consequently, shrink longitudinally. However, at the same time, the helical connectors twist. The twisting motion is most probably harmful to the blood vessel.
U.S. Pat. No. 5,195,984 to Schatz describes a similar stent but with one straight connector, parallel to the longitudinal axis of the tubular grafts, between tubular grafts. The straight member removes the twisting motion; however, it is not a very strong connector.
SUMMARY OF THE PRESENT INVENTIONIn accordance with embodiments of the present invention, a stent for implanting in the body to hold open a blood vessel, includes a body-compatible metal mesh defining a tube having adjacent contiguous cells, the cells having walls which are also the walls of adjacent cells. Each of the plurality of cells includes a pair of facing loops, each facing loop having a curved apex generally aligned along the longitudinal axis. Each facing loop has a first end and a second end that are generally aligned along the circumferential axis, each of the facing loops adapted to open further upon radial expansion of the stent which tends to foreshorten the stent longitudinally. Each of the plurality of cells further includes a pair of curved flexible links which connect the adjacent ends of the pair of facing loops to complete each of the plurality of cells, the pair of curved flexible links made of a metal which, upon expansion of the stent, bend to substantially offset foreshortening along the longitudinal axis.
The pair of facing loops and the curved flexible links are disposed and adapted to cooperate so that the tube, when unexpended, can flex as it is moved through curved blood vessels to a site where it is to be expanded and so that, when the stent is expanded in a curved vessel, at that site, as compared to each other, cells on the outside of the curve are open in length, but narrow in width as compared to cells on the inside of the curve which are short in length but increased in width. This results in a more constant stent cell area between the inside and the outside of the curve than would otherwise occur. Consequently, when the stent is coated with a medicine the compensation results in a more even dose being applied to the inside wall of the lumen, avoiding the possibility that a toxic dose is supplied at one area while a less than effective dose is applied to another area.
BRIEF DESCRIPTION OF THE DRAWINGSThe present invention will be understood and appreciated more fully from the following detailed description taken in conjunction with the drawings in which:
Reference is now made to
The stent of the present invention is a tube whose sides are formed into a plurality of each of two orthogonal meander patterns which patterns are intertwined with each other. The term “meander pattern” is taken herein to describe a periodic pattern about a center line and “orthogonal meander patterns” are patterns whose center lines are orthogonal to each other.
In the stent of
Meander pattern 12 is an horizontal pattern having an horizontal center line 13. Meander pattern 12 also has loops, labeled 18 and 20, but between loops of a period is an extended straight section labeled 22. Loops 18 open downwards and loops 20 open upwards.
Vertical meander pattern 11 is provided in odd and even (o and e) versions which are 180° out of phase with each other. Thus, each left opening loop 16 of meander pattern 11o faces a right opening loop 14 of meander pattern 11e and a right opening loop 14 of meander pattern 11o faces a left opening loop 16 of meander pattern 11e.
Horizontal meander pattern 12 is also provided in odd and even forms. The straight sections 22 of horizontal meander pattern 12e intersect with every third common member 17 of vertical meander pattern 11e. The straight sections 22 of horizontal meander pattern 12o intersect with every third common member 15 of vertical meander pattern 11e, beginning with the common member 15 two after an intersected common member 17. The result is a full loop 14 between meander patterns 12e and 12o and a full loop 16 between meander patterns 12o and 12e.
Returning to
In
During bending, the loops 14-20 to the right of the point A change shape in order to compensate for the differences in length between the inside and outside curves. For example, loops 18i and 20i near the inside of the curve are closer together than loops 18o and 20o on the outside of the curve, which expand. Loops 14i and 16i near the inside I are compressed while the loops 14o and 16o closer to the outside O of the curve are expanded.
As can be seen, both meander patterns 11 and 12 are involved in the bending. Although not shown, it will be appreciated that the stent of
It is noted that, due to the orthogonal meander patterns 11 and 12, the stent of
The vertical meander pattern 11 of
It will be appreciated that the two orthogonal meander patterns 11 and 12 and the compensation they provide to each other provides flexibility to the unexpanded stent of
The stent of the present invention can be manufactured from flat metal which is etched into the pattern of
It will be appreciated that the stent of the present invention can be made from metal and/or wire. Additionally, it can be plated with a protective material, embedded with a medicine, and/or covered with a material which can fill in the spaces 42 and 44.
It will be appreciated that the present invention encompasses all stents manufactured with a pattern formed of two meander patterns, orthogonal or otherwise. Another exemplary pattern, also with orthogonal meander patterns, is provided herein wherein
As can be seen in both
As shown in
A second loop 65 defining a second angle 66 is disposed between the second end 59 of the third member 57 and the second end 62 of the fourth member 60 and is disposed generally opposite to the first loop 63. A first flexible compensating member or flexible link 67 having a first end 68 and a second end 69 is disposed between the first member 51 and the third member 57 with the first end 68 of the first flexible compensating member or flexible link 67 communicating with the second end 53 of the first member 51 and the second end 69 of the first flexible compensating member or flexible link 67 communicating with the first end 58 of the third member 57. The first end 68 and the second end 69 are disposed a variable longitudinal distance 70 from each other.
A second flexible compensating member 71 having a first end 72 and a second end 73 is disposed between the second member 54 and the fourth member 60. The first end 72 of the second flexible compensating member or flexible link 71 communicates with the second end 56 of the second member 54 and the second end 73 of the second flexible compensating member or flexible link 71 communicates with the first end 61 of the fourth member 60. The first end 72 and the second end 73 are disposed a variable longitudinal distance 74 from each other.
In a preferred embodiment, the first and second flexible compensating member or flexible links 67 and 71 are arcuate. The first and second flexible compensating member or flexible links 67 and 71 are differentially extendable or compressible when the stent is bent in a curved direction away from the longitudinal axis 79 of the aperture 80 (Shown in
In a preferred embodiment, and as shown in
As shown in
It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined by the claims which follow:
Claims
1. A stent comprising a mesh of adjacent, connected cells, each cell comprising:
- an even number of fixed length, alternating, first and second loops, connected together in a closed cell, each loop having at least two portions with an area of inflection there between, said first and second loops defining first and second angles whose bisecting lines are at angles one to another;
- the second angles defined by the second loops being greater than the first angles defined by the first loops.
2. The stent according to claim 1, wherein the second angles defined by the second loops are obtuse.
3. The stent according to claim 1, wherein the second angles defined by the second loops are acute.
4. The stent according to claim 3, wherein the first angles defined by the first loops are acute.
5. A stent comprising a mesh of adjacent, connected cells, each cell comprising:
- an even number of fixed length, alternating, first and second loops, connected together in a closed cell, each loop having at least two portions with an area of inflection there between, said first and second loops defining first and second angles whose bisecting lines are at angles one to another;
- the first angles defined by the first loops being acute;
- the second angles defined by the second loops being obtuse.
6. A stent comprising a mesh of adjacent, connected cells, each cell comprising:
- an even number of fixed length, alternating, first and second loops, connected together in a closed cell, each loop having at least two portions with an area of inflection there between, said first and second loops defining first and second angles whose bisecting lines are at angles one to another;
- the first angles defined by the first loops being acute;
- the second angles defined by the second loops being right angles.
Type: Application
Filed: Sep 5, 2007
Publication Date: Dec 27, 2007
Inventors: Henry Israel (Bnei Brak), Gregory Pinchasik (Herzeliya)
Application Number: 11/850,078
International Classification: A61F 2/06 (20060101);