IL141860A

IL141860A - Stent with variable features

Info

Publication number: IL141860A
Application number: IL141860A
Authority: IL
Original assignee: Medinol Ltd
Priority date: 1996-09-19
Filing date: 1997-07-20
Publication date: 2008-03-20
Also published as: JP3676549B2; AR012274A2; UA49821C2; CA2211097A1; CN1160026C; SK126197A3; EP0830853A1; MX9706013A; UA59435C2; AU2873397A; CN1178664A; NO20025480D0; EP0830853B1; AU739287B2; US7044963B1; ATE292937T1; PL321724A1; US5807404A; US20100280593A1; US7976576B2

Description

STENT WITH VARIABLE FEATURES Eitan, Pearl, Latzer & Cohen-Zedek Advocates, Patent Attorneys & Notaries P-1303-IL1 STENT WITH VARIABLE FEATURES TO OPTIMIZE SUPPORT Related Applications The present patent application has been divided out from copending patent Application Number 121345.

BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates generally to stents for implanting into a living body. In particular, the present invention relates to intraluminal stents especially suited for implanting in a variety of lumens having variable characteristics, such as variable curvature, side branching, variable diameter, variable wall compliance or "end effects" of either the lumen, as found, e.g., in ostia, or the stent as the parameters may change at its ends.

DESCRIPTION OF THE PRIOR ART It is well known to use a stent to expand and impar support to different bodily conduits, such as blood vessels, by expanding a tube-like structure inside the vessel requiring support against collapse or closure. U.S. Patent No. 5,449,373 shows a stent preferably used for vascular implantation as part of a balloon angioplasty procedure. The stent of U.S. Patent No. 5,449,37 may be delivered through, or implanted in, a curved vessel . One shortcoming of conventional stents is that they may have deficiencies due to "end effects" where th ends of the stent tend to "flare out" during insertion o after expansion or have a decreased radial force at the end. Still another shortcoming of conventional stents i they do not have different characteristics, (e.g., flexi bility and rigidity) , to accommodate any changing characteristics of the section of the lumen requiri different stent characteristics.

WO 96/26689 discloses a segmented articulated stent of open structure comprised of end-connected struts making up the segments with angular mterconnects between segments. The open structure of this stent embodiment does not provide desirable coverage or support of the body lumen in which it is implanted. Further, the angular interconnects between segments do not contribute any flexibility to the stent as they do not flex or. bend during normal use. i EP 541 443 discloses -a stent for implanting in a body lumen having a mesh of unconnected criss-crossing wires disposed « . j between axial ly rigid graft sections. One shortcoming of this stent is the lack of radial support to the body lumen: in the meshed wire * section. In addition, like other conventional stents, the rigid graft end sections are susceptible to "flare out" during insertion or after expansion.

SUMMARY AND OBJECTS OF THE INVENTION The present invention provides for various embodiments of an intraluminal stent which includes varied or different mechanical properties along the axial length of the stent in order to improve stent end effects, or to accommodate variable vessel features. As a result, the various embodiments of the present invention allow for variable porperties such as flexibility or radial support between, axial regions of the stent. These varied, properties can be accomplished- in a number of different ways.

It is an object of this -invention to provide an expandable stent for treating, a lumen having a unique characteristic along a portion of the lumen, comprising: a plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the unique characteristic of that portion of the lumen in contact with, the .adapted row or rows.

In one embodiment, one of the plurality- of -rows disposed between the proximal end and the distal end is provided with a cell size that is larger than the cells in the remaining rows.

It is a further object of this" invention to provide an expandable stent for treating a lumen having a non-uniform diameter, comprising: a. plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one. of the rows is adapted to accommodate the non-uniform diameter of the portion of the lumen in contact with the adapted row. 2a expandable stent for treating a lumen having a non-uniform radial force, comprising: a plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the non-uniform radial force of the portion of the lumen in contact with the adapted row.

It is a further object of this invention to provide an expandable stent for treating a lumen having a non-uniform longitudinal flexibility, comprising: a plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the non-uniform longitudinal flexibility of the portion of the lumen in contact with the adapted row.

Passages which are not in the ambit of the claims do not belong to the invention. The scope of protection is as defined in the claims, and as stipulated in the Patent Law ( 1967). 3 BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows an illustration of the basic pattern of an embodiment of the stent of the present invention, shown in an unexpanded state,- Fig. 2 shows an illustration of the pattern of the stent of Fig. 1, in a partially expanded state,- Fig. 3 is a side view showing a conventional stent and a stent manufactured in accordance with one embodiment of the invention; Fig. 4 shows the stents of Fig. 3 crimped on a balloon catheter and bent prior to expansion- Fig. 5 shows the stents of Fig. 4 after they have been expanded in a curve; Fig. 6 shows the stents of Fig. 3 partially expanded on a substantially straight balloon catheter; Fig. 7 shows an alternative embodiment of the invention provided with a shortened C-shaped loop and in which two rows of cells are provided with thinner gauge U-shaped loops; Fig. 8 shows the stent of Fig. 7 partially expanded on a substantially straight balloon catheter; Fig. 9 shows the stent of Fig. 7 after it has been expanded on a curved catheter as it would be when inserted around a bend in a vessel ; Fig. 10 shows an alternative embodiment of a stent constructed in accordance with the invention and Fig. 11 shows the "S" or "Z" shaped loops constructed in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION Fig. 1 shows the general configuration of one embodiment of a stent 1 fabricated in accordance with th present invention. The stent 1 may be fabricated of bio ' compatible materials such as stainless steel 316L, gold, tantalum, nitinol or other materials well known to those skilled in the art as suitable for this purpose. The dimensions and gauge of material utilized may be varied as specific applications dictate. The stents of the present invention generally may be constructed in a manner in accordance with the stent described in U.S. Patent No. 5,733,303 , the disclosure of which is incorporated herein by reference .

Fig. 1 is a side view of the distal end 2 of stent : of the present invention, showing the general pattern of the stent. As shown in Figs. 1 and 2 the pattern may be described as a plurality of cells 3 and 3'. Each cell 3 is provided with a first member 4, a second member 5, a third member 6, and a fourth member 7. A first C-shaped loop 10 is disposed between the first member 4 and the third member 6 and a second C-shaped loop 11 is disposed between the second member 5 and the fourth member 7. In each of the cells 3, first member 4, second—member-—5-,— third member 6, and fourth member 7 are substantially equal. Thus, first C-shaped loop 10 is displaced a distance Dl and second C-shaped loop 11 is displaced a distance D2 from the center of cell 3. In a preferred embodiment, Dl is substantially equal to D2. A first flexible connector 8 is disposed between the first member 4 and the second member 5 and a second flexible connector 9 is disposed between third member 6 and fourth member 7. The flexible connectors 8 and 9 may be made in a variety of shapes, e.g., an "S" or a "Z" shape as shown in FIG. 11. In a preferred embodiment, a "U" .shape is utilized as shown in Figs. 1 to 10.

Fig. 1 shows the pattern of stent 1 in an unexpanded state, i.e. , that state in which the stent 1 is first inserted in a particular vessel in which a balloon angioplasty procedure is to be performed, but before balloon inflation. Fig. 2 shows the pattern of stent 1 in a partially expanded state, i.e., that state after the balloon has been expanded, e.g. by a balloon, and the state in which the stent 1 remains in the vessel which it supports. The plurality of interconnected cells 3 and 3' form a plurality of interconnected rows 25, 26, 27, and 28 of cells disposed along the longitudinal axis of the stent 1. Figs. 1 and 2 show a distal row 25 disposed at the distal end 2, a row 26 adjacent to and proximal to distal row 25, a row 27 adjacent to and proximal to row 26, and a row 28 adjacent to and proximal to row 27. It will be appreciated that the number of rows, and the number of cells per row, and the shape of each cell, may be varied as specific applications require .

As shown in Figs. 1 and 2, the cells 3' in distal row 25 differ from the cells 3 in rows 26, 27, and 28. The first member 4' and the third member 6' of the cells 3' in row 25 are shorter than the first member 4 and the third member 6 of the cells 3 in rows 26, 27 and 28. In cell 3', first member 4' is substantially equal to third member 6' , however, first member 4' and third member 6' are shorter than second member 5' and fourth member 7' . The shorter members 4' and 6' result in a first C-shaped loop 10' that is not disposed as far away from the center of the cell 3' as second C-shaped loop 11' . Thus, first C-shaped loop 10' may be thought of as being "shorter" than second C-shaped loop 11' . As shown in FIG. 2, first C-shaped loop 10' is disposed a distance Dl' that is less than the distance D2 ' that second C-shaped loop 11' is disposed from the center of the cell 3' . In an especially preferred embodiment:, Dl ' is about: 15% less than D2 ' .

Figs. 1 and 2 also show that the distal row 25 of the stent 1 is provided with a first U-shaped loop 8' and a second U-shaped loop 9' that are more flexible than the first U-shaped loop 8 and second U-shaped loop 9 of cells 3 in rows 26, 27, and 28 of the stent 1. This greater flexibility in the U-shaped loops 8' and 9' may be accomplished in a variety of ways, for example, by utilizing a different material, by treating the material e.g., by utilizing stainless steel annealing to impart selective degrees of hardness to the different portions of the stent. Alternat ively, if, s.g. , NiTi (Nitinol) is utilized, selected portions of the stent may be selectively thermo-mechanically treated so that portions of the stent, e.g. , the U-shaped members, will remain in a martensitic phase while other portions of the stent will be transformed into austenitic phase in this section to yield different properties. Greater flexibility may also be achieved by changing the shape of the "U", for example to a "Z" or an "S" (as shown in FIG. 11) , or by reducing the amount of material utilized to make the U-shaped loops 8' and 9' . In the embodiment shown in Figs. 1 and 2, the U-shaped loops 8' and 9' of row 25 are provided with the same thickness of material as the U-shaped loops 8 and 9 of the cells 3 in rows 26, 27, and 28, however, U-shaped loops 8' and 9' are not as wide. As shown in Figs. 1 and 2, U-shaped loops 8' and 9' have a width Wl that is less than the width W2 of U-shaped loops 8 and 9 in the cells 3 of rows 26, 27, and 28. In a preferred embodiment, Wl is about 50% narrower than W2. In an especially preferred embodiment, Wl is about 40% narrower than W2.

Fig. 3 is a side-by-side comparison of two stent sections and shows a conventional stent 12 compared to the stent 1, shown in Figs. 1 and 2. Fig. 4 shows stents 1 and 12 shown in Fig. .3 as they appear when they are crimped on a balloon and bent as they would be during insertion around a curve in a vessel. As shown "in Fig. 4, conventional stent 12 flares at its leading edge 13 in contrast to stent 1 which does not. Fig. 5 shows the stents of Fig. 4 after the stents have been expanded in a curve. The tip of conventional stent 12 produces a protrusion or sharp point 13 which could cause local pressure and possible trauma to the vessel wall . In contrast, the stent 1 constructed in accordance with the invention bends gently at its end 2 without forming a protrusion or sharp point because the deformation of the of U-shaped loops 8' and 9' in distal row 25 make the end 2 softer.

Fig. 6 shows the stents 1 and 12 of Fig. 3 at partial expansion (before reaching maximum pressure) disposed on a substantially straight catheter. As shown, although the two stents 1 and 12 are subjected to the same outward force, the end 2 of stent 1 is less expanded than the end 13 of conventional stent 12 demonstrating the increased radial force of the end 2 of stent 1 constructed in accordance with the invention. At full pressure the radii of the stents 1 and 12 will be equal, however, the end 2 of stent 1 will have greater radial resistance to collapse than the end 13 of stent 12.

Fig. 7 shows an alternative embodiment of the invention. As shown in Fig. 7, the cells 3' in row 25 are provided with a first member 4' and third member 6' that are shorter than second member 5' and fourth member 7' . The cells 3' in row 25 are provided with a first U-shaped loop 8' and a second U-shaped loop 9' that are thinner than the U-shaped loops 8 and 9 in the cells 3 in rows 27 and 28. The cells 3" in row 26 are provided with first U-shaped loops 8" and second U-shaped loops 9" that are narrower than the U-shaped loops 8 and 9 in the cells 3 in rows 27 and 28.

Fig. 8 shows the stent 20 of Fig. 7 during partial expansion of the stent showing the decreased expansion of 8 row 25 at partial expansion because of the higher radial force of the end 2 of the stent which results from construction with shorter C-shaped loops 10' in row 25, construction with narrower, i.e. , more flexible, U-shaped loops 8' and 9' in row 25, and 8" and 9" in row 26.

Fig. 9 shows the stent 20 of Figs. 7 and 8 after it has been expanded in a curved vessel and shows the bends of the U-shaped loops 8' and 9' in row 25 and 8" and 9" in row 26 which allows the end portion 2 of the stent 20 to more readily conform to the curve of the vessel, creating smooth ends with no sharp points or projections projecting into the vessel wall.

The changes can be made on one side only or on both sides of the stent as specific applications dictate.

Additionally, different combinations of embodiments of the invention may be mixed such as using thinner U-shaped loops, longer U-shaped loops or different shaped loops, e.g. , "Z" or "S" .

One example of how this may be achieved is shown in Fig. 10. Fig. 10 shows how the stent shown in Fig. 7 may be modified, if additional flexibility is desired. As shown in Fig. 10, the distal row 25, and the proximal row 29 of stent 30 are provided with first and second U-shaped loops that are more flexible than the U-shaped loops in the other rows of the stent disposed between the distal and proximal rows 25 and 29. In the embodiment of the invention shown in Fig. 10, the distal row 25 is provided with shortened members 4' and 6' and more flexible U-shaped loops 8' and 9' , as previously discussed, and the proximal row 29 is provided with shortened second and fourth members 5'' and 7' ' and more flexible U-shaped loops 8' ' ' and 9' ' ' . This arrangement imparts greater radial strength and greater flexibility to both ends of the sten .

If even greater flexibility at the ends of the stent is desired, the stent shown in FIG. 10 may be modified by replacing the U-shaped loops in rows 26 and 28 with more flexible loops. Thus, the distal row, the row proximal to the distal row, the proximal row, and the row" distal to the proximal row are provided with U-shaped loops that are more flexible than the U-shaped loops in the cells in the remaining rows of the stent.

The present invention contemplates a number of different variations and changes in different properties to achieve other non uniform features such as, but not limited to, cell size, cell shape, radio-opacity, etc. on the above-described preferred embodiments. The specified changes are brought only as an example for the application of the general concept, which is the basis for the present invention that stents with varying mechanical properties between sections along the stent may correct undesired effects at singular points such as stent ends and provide for a better fit to a vessel with properties changing along its axis. It is to be understood that the above description is only of one preferred embodiment, and that the scope of the invention is to be measured by the claims as set forth below.

S: \NY2DOCS\P S\P 12\·; 1663-1

Claims

141860/2 What is claimed is:

1. An expandable stent for treating a lumen having a unique characteristic along a portion of the lumen, comprising: a plurality of interconnected flexible cells, the cells comprising a pair of flexible connectors and arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the unique characteristic of that portion of the lumen in contact with the adapted row.

2. An expandable stent for treating a lumen having a non-uniform diameter, comprising: a plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the non-uniform diameter of the portion of the lumen in contact with the adapted row.

3. An expandable stent for treating a lumen having a non-uniform radial force, comprising: a plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the non-uniform radial force of the portion of the lumen in contact with the adapted row.

4. An expandable stent for treating a lumen having a non-uniform longitudinal flexibility, comprising: a plurality of interconnected flexible cells, the cells arranged in a plurality of interconnected flexible rows defining a stent having a proximal end and a distal end and a longitudinal axis, wherein at least one of the rows is adapted to accommodate the non-uniform longitudinal flexibility of the portion of the lumen in contact with the adapted row. 1 1 141860/2

5. The stent of claim 1 , wherein one of the plurality of rows disposed between the proximal end and the distal end is provided with a cell size that is larger than the cells in the remaining rows.

6. A stent according to any of claims 1-5 substantially as described hereinabove.

7. A stent according to any of claims 1-5 substantially as illustrated in any of the drawings. Eitan, Mehulal, Pappo, Kugler P-1303-IL1 12