WO2007088375A1

WO2007088375A1 - Bifurcation stent

Info

Publication number: WO2007088375A1
Application number: PCT/GB2007/000361
Authority: WO
Inventors: Ever Daniel Grech
Original assignee: Ever Daniel Grech
Priority date: 2006-02-03
Filing date: 2007-02-02
Publication date: 2007-08-09
Also published as: CA2535552A1

Abstract

A bifurcation stent comprising a substantially cylindrical body; at least two substantially cylindrical arms in fluid, connection with the body and extending outwardly from the body; a body cuff extending around an end of the body, said body cuff being distal to the arms; an arm cuff extending around each arm at an end of the arm distal to the body; a first body rib extending continuously along the length of the stent from the arm cuff to the body cuff; a second body rib extending continuously along the length of the stent from the arm cuff to the body cuff, said second body rib extending along an opposite side of the stent relative to the first body rib; a first arm rib extending continuously along the length of one arm from the arm cuff to a junction point of the two arms; and a second arm rib extending continuously along the length of one arm from the arm cuff to the junction point of the two arms, said second arm rib extending along an opposite arm relative to the first arm rib.

Description

BIFURCATION STENT

FIELD OF THE INVENTION

The present invention relates generally to the field of medical devices. More specifically, the present invention relates to a bifurcation stent.

BACKGROUND OF THE INVENTION

The normal arterial vessel wall consists of a regular arrangement of endothelial, smooth muscle and fibroblast cells, present in three distinct layers of endothelium, media and adventitia. A single layer of endothelial cells forms the luminal barrier to blood- borne signals that modulate vascular function. The adventitia, which forms the outer layer around the artery, consists primarily of extracellular matrix as well as some fibroblasts, nerve fibres and microvessels. The media consists of numerous layers of smooth muscle cells (SMCs) intermixed with extracellular matrix that is bound by the internal and external elastic lamina.

A vessel having a stenosis essentially has an inwardly protruding arcuate addition, of hardened material. The stenosis presents resistance to any expansion of the vessel in the region bridged by the stenosis and a significant radial force may need to be applied to expand the lumen against the stenosis. Stenoses vary in composition, for example, in the degree of calcification, and therefore vary in properties as well.

Atheromatous plaques are often responsible for narrowed arteries and may significantly impede adequate blood flow to tissue beyond the stenosed arterial segments. One method of alleviation of such stenosis is by means of balloon angioplasty, which may be carried out with or without the use of an additional stent for providing arterial support. Such a method is often used to treat lesions within coronary and peripheral arteries and is often carried out using catheters introduced percutaneously. A stent effectively provides a prosthetic intraluminal wall.

A bifurcation is an area of the vasculature or other bodily conduit where a first vessel or conduit is bifurcated into two or more branch vessels or conduits.

Mono-tubular stents are best suited to be implanted in-line in a body passageway, but are not suited for use in a bifurcated passageway. Specifically, particularly in situations wherein the atherosclerotic lesion is located at a bifurcation of the vessel (known as "the carina"), pose certain problems. For example, the prior art stents do not offer complete coverage of the lesion site. In addition to a lesion at the carina, it is possible that there may be one or more lesions at the "waist" of the bifurcated passageway (i.e. in the main passageway, just before the bifurcation), making it difficult for a stent to simultaneously adequately cover all of the lesion sites. Furthermore, other technical details may arise meaning that a satisfactory treatment may not be possible.

PCT Application IL 98/00275 teaches a Y-shaped stent wherein each of the common stent legs includes two relatively rigid bands executed as a chain of consecutively attached pockets, formed by the bending of saw-shaped profile protrusions.

PCT Application WO 00/27307 teaches a modified version of the device described in PCT Application IL 98/00275 wherein the stent has a Y-shape and each of the three legs include oppositely located relatively rigid bands with a possibility of forming chains of consecutively attached pockets, and closed loops, fastened to the said bands, forming strutted rings upon the stent's expansion.

US Patent 6,099,560 teaches a stent having a substantially "Y"-like shape, having a primary passageway and two secondary passageways. PCT Application WO99/15103 teaches a bifurcated stent comprising a main stent portion and a smaller flexible side portion. US Patent 6,540,779 teaches a bifurcated stent having a first and second sheet each formed into legs and a third sheet formed into a stem. In other embodiments, there is a first sheet which forms one leg and half a stem and a second sheet which forms another leg and half a stem. The parts are assembled within the vessel at the site of the bifurcation to be treated.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, there is provided a bifurcation stent comprising a substantially cylindrical body; at least two substantially cylindrical arms in fluid connection with the body and extending outwardly from the body a body cuff extending around an end of the body, said body cuff being distal to the arms; an arm cuff extending around each arm at an end of the arm distal to the body; a first body rib extending continuously along the length of the stent from the arm cuff to the body cuff; a second body rib extending continuously along the length of the stent from the arm cuff to the body cuff, said second body rib extending along an opposite side of the stent relative to the first body rib; a first ami rib extending along the length of one arm from the arm cuff to a junction point of the two arms; and a second arm rib extending along the length of one arm from the arm cuff to the junction point of the two arms, said second arm rib extending along an opposite arm relative to the first arm rib. The reinforcing body ribs and arm ribs provide improved radial strength to the stent which enable it to better expand and maintain its position against a stenosis. The axiaily continuous configuration of the ribs provides improved strength compared with the axialiy discontinuous mesh of conventional stents. In particular, the axial location of the ribs provides improved radial strength at the specific places (i.e. at the waist and carina) where weakness of the stent might undesirably result in partial collapse of the stent and/or restenosis.

According to a second aspect of the invention there is provided a kit comprising: a bifurcation stent as described in any of the preceding paragraphs; a catheter; at least two guide wires; an expandable balloon for expanding said stent.

According to a third aspect of the invention, there is provided a method of inserting a bifurcation stent into a bifurcated artery comprising: passaging a guidewire into the artery, across the lesion and down the main branch into a distal branch vessel; passaging a double-lumen catheter over the wire up to the level of the bifurcation; passaging a second guidewire down the second lumen of the double-lumen catheter until the tip emerges from the distal lumen of the doubie-lumen catheter; passing the guidewire down the side-branch vessel into a distal branch vessel; withdrawing the double-lumen catheter from the artery; passaging a bifurcation stent over both guidewires down to the level of the bifurcation lesion; inflating a bifurcation balloon, thereby expanding the stent; and removing the bifurcation balloon from the coronary artery.

Further features of the invention are defined in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments will now be more particularly described, by way of example only, with reference to the accompanying figures in which:

FIGURE 1 shows a top view of the bifurcation stent; FIGURE 2 shows a side view of the bifurcation stent of Figure 1 ;

FIGURE 3 shows a top view of an alternative embodiment of the bifurcation stent wherein the stent includes a second set of ribs;

FIGURE 4 shows a side view of the bifurcation stent of Figure 3; FIGURE 5 shows a side view of part of a further embodiment of the stent; and

FIGURE 6 shows a view of the stent of Figure 5 from the underside looking towards the carina.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned hereunder are incorporated herein by reference. As used herein, "stent" is intended to have broad meaning and encompasses any expandable prosthetic device for implantation in a body passageway.

Referring to the drawings, in the embodiment shown in Figures 1 and 2, a bifurcation stent 1 has a substantially Y-like shape. The bifurcation stent 1 comprises a body 10 having a substantially cylindrical shape, two or more substantially cylindrical arms 12, 14 extending from the main body 10 and in fluid communication with the body, a body cuff 16 at the distal end of the body relative to the arms 12, 14 and arm cuffs 18, 20 at the distal ends of the arms 12, 14 relative to the body 10. As can be seen in Figures 1 and 2, a pair of reinforcing ribs 20, 22 extend between the body cuff 16 and each of the arm cuffs 18, 20 along the body of the stent 1 on diametrically opposed sides thereof. In addition, there is a third pair of ribs 24, 26 which extend from one arm cuff 18 toward the point of the "V" 28 formed by the arms 12, 14 and extends from there to the other arm cuff 20. As can be seen in the drawings, the ribs 24, 26 are diametrically opposed to those portions of the ribs 20, 22 extending along the arms 12, 14. The ribs 20 and 22 and ribs 24, 26 are connected respectively by a plurality of expandable connectors 30. In the embodiment shown in Figures 1 and 2, the expandable connectors 30 are S-shaped connectors that connect the ribs 20, 22 and ribs 24, 26 together in a first position wherein the ribs 24, 26 and the ribs 20, 22 are proximal to one another and a second, expanded position wherein the ribs 24, 26 and the ribs 20, 22 are distal, to one another, as discussed below. It is further of note that the body 10 and the arms 12 and 14 are substantially composed of mesh 32 which also expands, as discussed below.

As will be appreciated by one of skill in the art, there are various connector designs which may be used within the invention. For example, the commonly used types are either S-shaped, V-shaped, Z-shaped or a combination of these. It is also of note that in some embodiments, the ribs may be connected at the point of the "V" 28 by connectors having a different shape and arranged to connect one portion to two other . portions while maintaining expandability.

In an alternative embodiment, shown in Figures 3 and 4, the stent 1 includes "north-south" ribs 40, 42 which are constructed in the same manner as the ribs 20, 22 and the ribs 24, 26, that is, are connected by expandable connectors as discussed above. It is of note that for purposes of clarity, the ribs 20, 22 may be referred to as "east-west" ribs. As with the "east-west" ribs discussed above, the "north-south" ribs are substantially diametrically opposed one another and thereby provide additional strength to the stent 1.

As can be seen in the drawings, the cuffs 16, 18 and 20 are connected to the mesh 32 and the ribs 20, 22, 24 and 26. As will be appreciated by one of skill in the art, the cuffs 16, 18 and 20 are arranged to expand as discussed below and may be composed of any suitable material. It is of note that the malleability of the metal and the mesh design allows good angle variation of the arms for inserting the stent, as discussed below.

Referring now to Figures 5 and 6, an alternative embodiment is illustrated in which each of the pairs of body ribs 20, 22 and arm ribs 24, 26 are replaced by a single body rib 20^J and arm rib 24'. In all embodiments, the body ribs 20, 22; 20' extend continuously along the length of the stent from one of the arm cuffs 18, 20 to the body cuff 16. As will be appreciated by one of skill in the art, many suitable shapes for the body rib(s) are possible (for example the substantially linear ribs of Figures 1 and 2, or the more irregular ribs of Figures 5 and 6), so long as the rib(s) are continuous in the longitudinal or axial direction of the stent. It is possible for the rib(s) to generally follow the pattern of the mesh 32 of the main part of the stent, so long as they are axially continuous. The ribs provide reinforcement to the stent. The ribs may be made from a different and stronger material than the mesh 32 of the stent. Alternatively, the ribs may be made of the same material as the mesh 32, but having a larger diameter in order to provide extra strength. Other configurations can be envisaged. The body ribs and arm ribs are specifically located so that they can provide reinforcement for the stent in the radial direction particularly in the areas of the waist and carina respectively of the bifurcation. It is advantageous for the stent to have reinforcement in the radial direction so that the stent can properly expand against the radially-inward force of the hardened material of a stenosis. In the illustrated embodiments, the stent 1 has two arms 12, 14. In other embodiments, the stent may include more than two arms, for example three arms for use in a trifurcation. It is of note that in these embodiments, the additional arms contain reinforcing ribs similar in structure and location (i.e. - diametrically opposed to ribs on other arms) as those discussed above. It is possible that the arms may be of different lengths and/or diameters and the arm and body ribs can be adapted in their dimensions accordingly.

In the illustrated embodiment, the majority of the body 10 and arms 12, 14 are composed of mesh in addition to the ribs and connectors.

The bifurcation stent 1 may be composed of any suitable material, for example but by no means limited to stainless steel, stainless steel alloy, other alloy such as nickel or titanium, Elgiloy, nitinol, shape memory polymers, or other biocompatible materials and the like. Part or all of the stent may be made from a radioactive material.

The typical dimensions of the stent are as follows. It is to be understood that these dimensions are for illustrative purposes only. The length of the stent may vary between 8 to 25 mm (or more depending on the length of the lesion). The unexpanded and expanded diameters of the stent could be approximately 1.5 and 6.0 mm respectively. The radial thickness of the main body ribs may be larger (0.25 - 0.75mm) as they need to provide more radial support, than the stent mesh in between (0.2mm).

For use, the bifurcation stent 1 is assembled as follows. First, the stent 1 is manufactured in two parts, a top half 40 and a bottom half 42. The top half 40 includes the rib 20 and the rib 24 whereas the bottom half 42 includes the rib 22 and the rib 26. The ribs 20 and 22 and the ribs 24 and 26 respectively are connected by expandable connectors 30, as discussed above. The assembled stent 1 is now ready for use.

In another aspect of the invention, there is also provided a double-lumen catheter for use with the bifurcation stent as described below. As will be appreciated by one of skill in the art, the catheter comprises a main body and two lumens extending outwardly therefrom and has a general shape substantially similar to the bifurcation stent. As discussed below, in use, the bifurcation catheter is used for positioning guidewires through the two lumen such that the bifurcation stent can be inserted into an artery or passageway, as described below. Insertion of the stent involves the following steps: (1) The passage of a full-length

(at least 175 cm) soft tipped guidewire into the coronary artery, across the lesion and down the main branch into a distal branch vessel. (2) The passage of the double-lumen catheter over the wire up to the level of the bifurcation. (3) The passage of a second guidewire down the second (unoccupied) lumen of the double-lumen catheter until the guidewire tip emerges from the distal lumen of the double-lumen catheter. The guidewire is then passed down the side-branch vessel into a distal branch vessel. (4) The double- lumen catheter is then gently withdrawn from the coronary artery and completely removed out of the patient. The purpose of the double-lumen catheter is to avoid entanglement of the two guidewires that would otherwise occur, which may impede the passage of the bifurcation stent across the lesion. (5) The passage of the bifurcation stent over both guidewires down to the level of the bifurcation lesion. (6) Once satisfactory positioning of the stent has been obtained, the bifurcation balloon can be expanded by way of an indeflator controlled by the operator, to allow expansion of the stent. (7) The bifurcation balloon is then deflated which can be then be removed from the coronary artery and the patient. (8) Both guidewires can also be removed if a satisfactory result is obtained. As will be appreciated by one of skill in the art, the bifurcation stent is initially inserted in an unexpanded conformation. Following expansion of the balloon, the mesh of the body and arms of the stent and the pairs of ribs (and the connectors therebetween) expand, resulting in the expansion of the stent to fill the artery.

It is of note that the stentcould also be successfully implanted in other non- vascular areas, such as the urinary tract or bile duct.

In yet other embodiments, the bifurcation stent 1 may be coated with or have embedded therein an effective amount of an anti-stenotic compound, an anti-thrombotic compound, another compound or mixture thereof. As used herein, "an effective amount" refers to an amount of the anti-stenotic compounds that is sufficient to reduce or slow artery narrowing. For example, the anti-stenotic compounds may be incorporated into nylon microcapsules and applied to the surface of the stent. Alternatively, the device may be coated with a film composed of, for example, cellulose, hyaluronic acid, chitosan, ethylene vinyl acetate, or poly lactic acid, impregnated with the anti-stenotic compound. Yet further, the stent may be coated with a thermo-sensitive gel such that the anti-stenotic compound is released when the stent is implanted.

While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein, and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.

Claims

1. A bifurcation stent comprising a substantially cylindrical body; at least two substantially cylindrical arms in fluid connection with the body and extending outwardly from the body; a body cuff extending around an end of the body, said body cuff being distal to the arms; an arm cuff extending around each arm at an end of the arm distal to the body; a first body rib extending continuously along the length of the stent from the arm cuff to the body cuff; a second body rib extending continuously along the length of the stent from the arm cuff to the body cuff, said second body rib extending along an opposite side of the stent relative to the first body rib; a first arm rib extending continuously along the length of one arm from the arm cuff to a junction point of the two arms; and a second arm rib extending continuously along the length of one arm from the arm cuff to the junction point of the two arms, said second arm rib extending along an opposite arm relative to the first arm rib.

2. Bifurcation stent as claimed in claim 1 wherein one or more of said first body rib, said second body rib, said first arm rib and said second arm rib comprises a pair of ribs being interconnected by a plurality of connectors.

3. Bifurcation stent as claimed in claim 2 wherein said connectors are expandable.

4. Bifurcation stent as claimed in claim 2 or claim 3 wherein said connectors have a generally S-shape, Z-shape or V-shape.

5. Bifurcation stent as claimed in any of the preceding claims wherein one or more of said first body rib, said second body rib, said first arm rib and said second arm rib are substantially linear.

6. Bifurcation stent as claimed in any of claims 1-4 wherein one or more of said first body rib, said second body rib, said first arm rib and said second arm rib have a generally square-wave shape, or other continuous shape which generally follows the pattern of the stent mesh.

7. Bifurcation stent as claimed in any of the preceding claims wherein said first and second body ribs are located diametrically opposite one another on the stent.

8. Bifurcation stent as claimed in any of the preceding claims further comprising a third body rib or a third pair of body ribs.

9. Bifurcation stent as claimed in any of the preceding claims wherein said stent is balloon-expandable.

10. Bifurcation stent as claimed in any of claims 1-8 wherein said stent is self- expanding.

11. Bifurcation stent as claimed in any of the preceding claims further comprising a coating of a drug or having a drug embedded therein, the drug being for example an anti-stenotic or antithrombotic drug.

12. Bifurcation stent as claimed in any of the preceding claims wherein each of said at least two arms differs in length and/or diameter from the other.

13. Bifurcation stent as claimed in any of the preceding claims comprising three of said substantially cylindrical arms.

14. Bifurcation stent substantially as described herein with reference to and as illustrated by any appropriate combination of the accompanying drawings.

15. A kit comprising: a bifurcation stent as claimed in any of the preceding claims; a catheter; at least two guide wires; an expandable balloon for expanding said stent.

16. A kit as claimed in claim 15 wherein said catheter is a double-lumen catheter.

17. A kit as claimed in claim 15 or claim 16 wherein said balloon is a bifurcation balloon having a generally Y-shape.

18. A kit as claimed in claim 15 or claim 16 wherein said balloon comprises two single balloons, preferably attached to one another.

19. A method of inserting a bifurcation stent into a bifurcated artery comprising: passaging a guidewire into the artery, across the lesion and down the main branch into a distal branch vessel; passaging a double-lumen catheter over the wire up to the level of the bifurcation; passaging a second guidewire down the second lumen of the double-lumen catheter until the tip emerges from the distal lumen of the double-lumen catheter; passing the guidewire down the side-branch vessel into a distal branch vessel; withdrawing the double-lumen catheter from the artery; passaging a bifurcation stent over both guidewires down to the level of the bifurcation lesion; inflating a bifurcation balloon, thereby expanding the stent; and removing the bifurcation balloon from the coronary artery.