WO1998038946A1 - Expandable and self-expanding stents and methods of making and using the same - Google Patents

Abstract

Expandable and self-expanding stents (30), optionally including control over end to end shortening during expansion, are disclosed. The stents (30) have a plurality of rings (60) in an array, with selecting links between the rings (60) to provide articulation as appropriate. The rings (60) have at least one and preferably a number of expansion cells (66). The cells (66) can be either a complex curve based arrangement, a combination of straight, helical and counter-helical segments, or hybrids of such arrangements. Methods of producing the devices are also disclosed, including various etching methods.

Description

EXPANDABLE AND SELF-EXPANDING STENTS AND

METHODS OF MAKING AND USING THE SAME

BACKGROUND OF THE INVENTION

The present invention relates to stents and, most preferably, to stents which can be

expanded, for example, by expanding an internally positioned balloon, as well as, or

alternatively to self-expanding stents having similar structural aspects. Methods for producing

and using such stents are also disclosed.

Under normal circumstances, the heart functions as a pump to perfuse blood throughout the body through arteries. The arteries of some patients are subject to stenosis, a localized

partial blockage which narrows the passageway and interferes with normal blood flow. This

condition is termed atherosclerotic coronary artery disease. It is a leading cause of morbidity

in adults in the western world. One corrective procedure used to treat this disease is coronary

bypass surgery, which is a highly invasive operation. In recent years a corrective procedure,

percutaneous transluminal coronary angioplasty, and devices known as balloon angioplasty

catheters have been widely used to correct stenotic conditions within arteries, particularly

coronary arteries, in a relatively efficient manner.

An angioplasty procedure generally includes inserting a deflated balloon, mounted on

a catheter, within the affected vessel or artery at the point of a stenosis. The balloon is then

inflated to physically force the dilation of the partially occluded vessel. Roughly 300,000

patients per year in the United States are presently undergoing coronary angioplasty

procedures. However, a substantial percentage of patients who have had balloon angioplasty

redevelop the stenosis in a relative short period of time. The reoccurrence typically becomes evident within less than about 6 months after angioplasty and may affect 30 to 40 percent of patients. The percentage of patients who have reoccurring stenoses is generally reduced by

installing a "scaffolding" device, known as a stent, at the site of the stenosis. The underlying

mechanism for the benefit of stenting may be as simple as preventing immediate elastic recoil

and mamtaining a large luminal cross-section for a few days after angioplasty. The drawbacks

of stenting are thought to relate to an increased potential for thrombus formation and

hyperplasia induced by metallic or other stent materials.

One of the complications of balloon angioplasty is the occurrence of tears in the wall

of the artery leading to intimal dissections which is a principle cause of closure of the artery

due to the procedure and may require emergency surgery. Endovascular stents offer the

potential of tacking these intimal flaps to keep the lumen patent. These tears are of variable

length and often spiral in shape. In addition, following balloon angioplasty patients may have

a suboptimal result due to a markedly irregular lumen. In these situations stenting with stents

offers the advantage of attaining excellent results.

While coronary and other arterial stenosis are common applications for stenting, stents

can be used to treat narrowings in any hollow or tubular organs such as the Esophagus,

urethra, Biliary Tract and the like.

A number of challenges are present in the preparation, deployment and use of stents.

One challenge is to efficiently prepare a stent without compromising the present medical

effectiveness of the stent. Another challenge is to improve the medical effectiveness of stents.

For example, large metal stent surface areas are thought to have a positive correlation with

increased platelet deposition and potentially increase the risk of thrombosis formation and

intimal hypoplasmia. Yet another challenge is to improve technics for delivery and deployment of stents.

For example, jagged edges can result in snagged arteries and other complications during

movement of the stent to the location of a stenosis to be treated. A tear in an artery wall resulting either from a snag or expansion mishap may require emergency corrective surgery

or may lead to a new closure site in the artery. Inadequate radiopacity is also an issue with stents made of materials which are not radiopaque. It will be appreciated that measures for

making the stents radiopaque, and therefore, viewable within the body during procedures using

real-time x-ray viewing techniques, will provide improvements to the art.

The current medical prior art contains a number of insights into stent technology.

Some examples are noted here to provide background. Schepp-Pesch et al. (U.S. Patent No.

5,354,309) disclose a spiral shaped sheet metal part which widens to a cylindrical jacket-

shaped outer contour device at a transition temperature. The device is formed from a memory

alloy metal with parallel elongated slots and web regions between the slots. The slots deform

into diamond-shaped gaps or operation between webs upon expansion of web associated with

an increase in temperature. Another example is Burton et al. , WO 92/11824. Burton discloses

a self-expanding intraluminal prosthesis or stent which is tubular and has opposed ends and

fenestrated walls. The Burton stent is taught to be prepared by molding, or alternatively, laser

or water-jet cutting of a solid tube to form a pattern of apertures and leaving intersecting

thread-like strips therebetween. A third example is Wolff (U.S. Patent No. 5,104,404), which

discloses a number of stent segments formed by welding wire strands in a zig-zag arrangement.

The segments are connected by hinges to allow them to articulate. The Wolff hinges can be

welded straight wire or coiled wire.

One particularly well accepted stent is the stent disclosed by Palmaz (U.S. Patent Nos. 4,733,665 and 4,739,762, each of which are hereby incorporated herein by reference). The

Palmaz stent is in fairly wide use in the U.S. and elsewhere. However, this stent is

particularly rigid and difficult to deliver in through "meandering" coronary arteries due to this

rigidity. Furthermore, the ends at least one of the stents disclosed by Palmaz come together in a series of points which can catch on the inner walls of the vessels through which the stent

is passed occasionally tearing the tissue along the inner walls. It would be a desirable and a

significant advance in the field of Cardiology to provide a stent which can be articulated to

facilitate the delivery of a stent through the often tortuous pathway provided by coronary

arteries to a desired final location within the patient. In particular, the stent should have the

ability to "snake" around complex curves and tight curves encountered in the circulatory

system, especially those associated with the coronary system which supplies critical blood flow

to the heart. The avoidance of any stent structure which tend to snag or catch on the interior

of the various blood vessels is also desirable.

Wiktor (U.S. Patent Nos. 4,969,458; 4,886,062; and 5,133,732) also discloses

articulating expandable stents. These stents generally coexist of one or more low memory

metal wires which are wound in such a way to provide an articulating metal scaffolding

structure which is balloon expandable once it is placed within the stenotic region of the

diseased vessel.

A number of self-expanding stents also show significant ability to articulate once they

are free of the sheath in which they are delivered. These stents include those disclosed by

Gianturco et al. (U.S. Patent No. 5,035,706) and Cragg (U.S. Patent No. 5,405,377).

The control of end-to-end length changes upon expansion is a desirable feature in

stents. It would also be a significant advance if the stent could be manufactured economically. It will also be appreciated that inexpensive quality control would also be desirable.

The following invention discloses stents and methods of producing stents which address

these and other concerns.

SUMMARY OF THE INVENTION

Generally, the present invention is concerned with expandable stents and methods for

producing such stents, although alternative stents of the present invention include self-

expanding stents. The preferred stents of the present invention, however, are expandable,

typically, for example, by enlarging an expandable balloon positioned within the stent. By

way of an overview, the expandable stents of the present invention preferably have a plurality of expandable ring structures, the ring structures are joined end-to-end and feature an absence

of potential tissue snagging structures. The stents and ring structures of the stents are

preferably characterized by relatively low surface area compared to the surface area of a simple

cylinder of similar dimensions and connecting structures which allow the various ring

structures to articulate with respect to one another. The stents of the present invention are

efficiently and easily produced and amenable to good quality control at a relatively low cost.

Moreover, the stents of the present invention, in certain embodiments which may be desirable

during certain procedures, can provide no end-to-end shortening, low end-to-end shortening,

or high end-to-end shortening upon expansion. These various attributes, advantages, and

features will become apparent from the following disclosure.

In a first embodiment, the present invention is a stent expandable by enlarging an

expandable balloon positioned within the stent. The expandable stent includes a plurality of

modules. Each of the modules have a plurality of individual cells radially interconnected to

form a ring of individual cells interconnected to each other in series. Each of the individual cells include a continuous strand of a material, the continuous strand of material in each cell being interconnected with itself so as to surround a space central to the interconnected strand

and define a plurality of sides. The portions of any of the plurality of sides can be shared by adjacent cells in the ring. The material employed is deformable, such that the ring can be

deformed from a first configuration, wherein the ring has a first circumference, to a second

configuration wherein the ring has a second circumference greater than the first circumference.

Each cell of the rings has an upper half and a lower half. The upper and lower halves are

joined together at respective first and second ends. The plurality of modules includes at least

first and second modules, where the individual cells of the first module are defined as first

module cells and the individual cells of the second module are defined as second module cells.

The modules are oriented side by side such that the second ends of the first module are located

proximate the first ends of the second module and at least one of the plurality of second ends

is interconnected with at least one of the plurality of the first ends. Further, at least one cell

of the first module is interconnected with at least one cell of the adjacent second module.

Moreover, the modules can articulate relative to one another such that the modules of the

expandable stent can pass through an otherwise tortuous passageway with many "sharp" turns

or twists. Preferably, in this embodiment, the expandable stent is such that one of the sides

of each cell is a longitudinally oriented straight side. Other sides may be helical or curved.

Preferably, the stent is such that the upper half and lower half of each cell are mirror

images. The material of the continuous strand of the preferred expandable stents of the present

invention will be selected from amongst low memory metals such as tantalum, palladium,

silver, gold, stainless steel and the like. A radiopaque marker may be present also, for example in the form of one or more tantalum rivets. In alternative embodiments of the present stents which are self-expanding the material of the continuous strand of the stent is selected

from the group consisting of high memory elastic materials such as superelastic metal alloys, such as for example superelastic Nitinol (a mckel-titanium alloy), superelastic plastics, silastic

rubber, other elastic polymers, spring steel, and the like. In another embodiment, the present invention is an expandable stent. The stent again being expandable by enlarging an expandable balloon positioned within the stent. The stent

includes a plurality of individual cells radially interconnected to form a ring of individual cells

interconnected to each other in series, each of the individual cells including a continuous strand

of a material. The continuous strand of material in each cell is interconnected with itself so

as to surround a space central to the interconnected strand and define a plurality of segments.

Portions of any of the plurality of segments can be shared by adjacent cells in the ring and the

material is deformable. That is, the ring can be deformed from a first configuration, wherein

the ring has a first circumference, to a second configuration wherein the ring has a second

circumference greater than the first circumference. Each cell has an upper half and a lower half, the upper half being a mirror image of the lower half, the upper and lower halves being

joined together at respective first and second ends. Again, preferably, the cells have a greater

longitudinal extent than "circumferential" extent in the first configuration. Also it is preferred

that one of the segments of the cells include at least one longitudinally oriented straight

segment. Most preferably, the longitudinal ends of the cells are curved, with the inside of the curve facing into the center of the cell.

In another embodiment, the present invention is a prosthesis. The embodiment includes

a sequential array of a plurality of independent rings, each of the independent rings has a first

generally "circumferential" configuration defining a longitudinal axis and has distal and proximal ends. Each of the rings includes at least one deformation component allowing the

ring to be deformed to a second generally "circumferential" configuration when radial force

is applied to the ring. The deformation component includes a frame defining an aperture

surrounded by the frame, the frame and aperture having a greater longitudinal extent than "circumferential" extent in the first generally "circumferential" configuration. Physical

connections between rings of the plurality link the distal end of at least one ring to the

proximal end of an adjacent ring of the sequential array. Each of the rings are interconnected

in series with at least one adjacent ring within the sequential array. Further, at least two

adjacent rings can articulate relative to one another such that the longitudinal axes of the

respective adjacent rings are non-coincident when said adjacent rings are articulated relative to one another.

Preferably, in the prosthesis, the first "circumferential" structure is bounded by a

region defined by a first cylinder, with a first radius, and a second cylinder, with a second

radius different that first radius. The difference between the radii being the radial thickness

of the prosthesis. The prosthesis is characterized by a substantially uniform radial thickness.

Preferably, each of the deformation components is identical. Preferably, each ring is

composed only of a plurality of identical deformation components. Preferably, the frame

includes a longitudinally oriented straight segment. The longitudinally oriented straight

segment may be shared with an adjacent frame. The frame may include a helical segment, if

so, then preferably, the helical segment is connected to the longitudinally oriented straight

segment. Again, preferably the frame is curved at its greatest longitudinal extent.

The present invention also is a method of making a prosthesis. The method first

requires providing a cylindrical walled tube, the tube defining an axis. Second, the method includes the step of ehminating non-contiguous portions of material from the cylindrical walled tube to leave a desired structure. The desired structure includes a plurality of individual cells

radially interconnected to form a ring of individual cells interconnected to each other in series,

each of the individual cells having a continuous strand of a material. The continuous strand

of material in each cell is interconnected with itself so as to surround a space central to the

interconnected strand and define a plurality of segments. Portions of any of the plurality of

segments can be shared by adjacent cells in the ring. The material from the tube is deformable

such that the ring can be deformed from a first configuration, wherein the ring has a first circumference, to a second configuration wherein the ring has a second circumference greater

than the first circumference. Each cell of the structure has an upper half and a lower half,

which are joined together at respective first and second ends. Preferably, the rings are

interconnected by selected remaining portions of cylindrical walled tube. Preferably, the

interconnected rings are linked such that the rings modules can be articulated relative to each

other and allowing at least one of the rings to be moved relative to the original axis of the

tube. One preferred method to accomplish the elimination of material is chemical etching.

Preferably, an etch resistant protective coating is present upon desired structure to be retained in the resulting prosthesis.

In another embodiment, the present invention is a prosthesis. The prosthesis includes

a proximal to distal array of rings, each of the rings having a proximal end and a distal end,

and each physically linked to the adjacent proximal and distal ring, if any, of the array. The

array initially shares a common axis and is disposed within a region defined as common

cylindrical wall about the common axis. Each of the rings is a repeating series of frames, each

of the frames defining a cell, and each cell having a greater extent parallel to the common axis than "circumferential" to the common axis. Each of the frames has a first, generally linear

longitudinally oriented segment, and a second, generally linear longitudinally oriented

segment, parallel to and spaced circumferentially apart from the first segment. The frames

also have a first helical segment, connected at a distal end to the proximal end of the first generally linear longitudinal segment and a second helical segment parallel to and displaced

longitudinally and radially apart from the first helical segment, connected at a proximal end to the distal end of the second generally linear segment. Also present in the frame are a first

counter helical segment, connected at a distal end to the proximal end of the second generally

linear segment, and a second counter helical segment parallel to and displaced longitudinally

and radially from the first counter helical segment, the proximal end connected to the distal

end of the first generally linear segment. The first generally linear segment serves as a second

generally linear segment for an adjacent frame and the second generally linear segment serves

as a first generally linear segment for a different adjacent frame.

In this embodiment, there are two preferred structures. The distal end of the first counter helical segment and the second helical segment are connected to form a distal end of

the frame, and the proximal ends of the first helical and first counter helical segments are

connected to form a proximal end of the frame. Alternatively, the distal end of the first

counter helical segment and the second helical segment are each connected to a curved

segment, the inside of the curve facing into the cell of the frame and forming a distal end of

the frame, and the proximal ends of the first helical and first counter helical segments are each

connected to a curved segment, the inside of the curve facing into the cell of frame and

forming a proximal end of the frame. Also , the second helical segment of a first frame may

serve as the first helical segment of an adjacent frame longitudinally displaced from the first frame and forming one of a second "circumferential" array of frames.

Preferably, the physical link connecting a ring to an adjacent ring of the array connects

a selected portion of a frame of one ring with a selected portion of a frame of the adjacent ring. This may be a physical link connecting a ring to an adjacent ring of the array connects

for example between the distal end of a frame the ring and a proximal end of a frame of the adjacent ring. Alternatively, the physical link connecting a ring to an adjacent ring of the

array may connect between the distal end of a frame the ring and a proximal end of a linear

segment of a frame of the adjacent ring.

In alternate embodiments, self-expanding stents are provided. These alternative stents

can have the identical structural features of the expandable stents of the present invention but

are made from different materials which have strong "shape" memory which enable them to

be constrained into a lower profile and subsequently released from the constrained

circumstance, in which case the stent expands to an unconstrained orientation wherein the stent

has expanded. In this unconstrained expanded orientation the stent will provide appropriate

"scaffolding" to treat the stenosis. It will be appreciated that, it is somewhat less critical that

self-expanding stents of the present invention articulate in order to pass through torturous

coronary arteries when they are constrained within sheaths to deliver the self-expanding stents

to the stenosis, unless the sheath itself is pliable and can articulate through such passageways.

The present invention includes such sheaths which bend easily through coronary arteries while

constraining the articulating self-expandable stents of the present invention.

A wide range of potential applications are possible for the stents of the present

invention, for example therosclerotic peripheral vascular disease; congenital stenosis of the

branches of the pulmonary arteries; acquired stenoses or extrinsic compressions of the superior and inferior vena cava; renal artery stenoses (which is often due to fibromuscular hyperplasia

rather than atherosclerotic disease); congenital coarctations of the aorta and recoarctations which appear following surgery for coarctations of the aorta; benign hypertrophy of the

prostate; stenotic lesions of the Biliary Tract and esophagus etc. It will be appreciated that

stent grafts can be used in conjunction with the respective stents of the present invention to

repair aneurysms in the aorta or large arteries and/or other abnormalities in the various tubular

organs throughout the body.

These and other various other advantages and features of novelty which characterize

the present invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the present invention, its

advantages and other objects obtained by its use, reference should be made to the drawings,

which form a further part hereof, and to the accompanying descriptive matter, in which there

is illustrated and described preferred embodiments of the present invention.

BRJTEF DESCRIPTION OF THE DRAWINGS

In the drawings, in which like reference numbers indicate corresponding parts

throughout the several views;

FIG. 1 is a schematic representation of a side view of a first embodiment of the present

invention as temporarily mounted upon a balloon catheter (shown in ghost outline) and shown

in close association with a longitudinal section of a stenosis in an artery about to be treated;

FIG. 2 is a subsequent schematic representation of a side view of the embodiment

depicted in Figure 1 with the balloon catheter (shown in ghost outline) inflated to deform and

expand the expandable stent and treat the stenotic condition shown in longitudinal section;

FIG. 3 is a schematic representation cross-sectional view of the schematic representation of Figure 1 ;

FIG. 4 is a schematic representation cross- sectional view of the schematic representation of Figure 2 as seen from the line 4-4;

FIG. 5 is a schematic view of an enlarged portion of the embodiment of Figure 1 as seen from the line 5-5 of Figure 3;

FIG. 6 is a schematic view of an enlarged portion of the expanded embodiment shown

in Figure 2 as seen from the line 6-6 of Figure 4;

FIG. 7 is a schematic view of an enlarged portion of another embodiment of the

present invention similar to that shown in Figure 5;

FIG. 8 is a schematic view of an enlarged portion of the embodiment shown in Figure

7 after expansion shown in a manner similar to that shown in Figure 6;

FIG. 9 A is a schematic view similar to that shown in Figures 5 and 7 of an enlarged

portion of yet another embodiment of the present invention similar to those shown in Figures

5 and 7;

FIG. 9B is a schematic view of further embodiment of the expandable stent of the

present similar to that shown in invention Figure 9A, except that each of the respective

adjacent ring pairs are interconnected by only a single link between just two cells, one in each

of the respective rings;

FIG. 10 is a greatly enlarged detailed view of the portion of the embodiment shown in

Figure 9 within the broken line circle 10;

FIG. 11 is a greatly enlarged detailed view of the portion of the embodiment shown in

Figure 9 within the dashed line circle 11 ;

FIG. 12 is a greatly enlarged detailed view of the portion of the embodiment shown in Figure 9 within the solid line circle 12;

FIG. 13 is a schematic view similar to that shown in Figure 5 of an enlarged portion

of still another embodiment of the present invention;

FIG. 14 is a schematic view similar to that shown in Figure 6 of an enlarged portion

of the embodiment shown in Figure 13 after expansion;

FIG. 15 is a schematic view similar to that shown in Figure 6 of an enlarged portion

of yet another embodiment of the present invention having structural components or "cells"

which are similar to those in the embodiment shown in Figure 14, but having different

structural connections;

FIG. 16 is a schematic view similar to that shown in Figure 6 of an enlarged portion

of yet another embodiment of the present invention having structural components or "cells"

which are similar to those in the embodiment shown in Figure 14, but having different

structural connections;

FIG. 17A is a schematic view similar to that shown in Figure 5 of an enlarged portion

of a yet another embodiment of the present invention;

FIG. 17B is a schematic view similar to that shown in Figure 17A, but showing a

different embodiment of a stent having cells similar to those in Figure 17A, but only a single

independent ring;

FIG. 18 is a schematic view similar to that shown in Figure 6 of an enlarged portion

of the embodiment shown in Figure 17A after expansion thereof;

FIG. 19 is a greatly enlarged detailed view of the portion of the embodiment shown in Figure 17 within the solid line circle 19;

FIG. 20 is a greatly enlarged detailed view of the portion of the embodiment shown in Figure 17 within the dashed line circle 20;

FIG. 21 is an enlarged detailed sectional view of the embodiment shown in Figure 20

as seen form the line 21-21 of Figure 20;

FIG. 22 is a schematic representation of a self-expanding stent of the present invention

constrained within a dehvery catheter having a sheath and positioned in a stenotic region within

a coronary artery;

FIG. 23 is a schematic representation of the stent shown in Figure 22 and 23, but after

the sheath is fully withdrawn to allow the self-expanding stent to expand within the diseased

artery, thereby compressing the obstruction shown in the prior figures against the artery's inner

wall; and

FIG. 24 is a further schematic representation of an alternate self-expanding stent,

similar to that shown in Figures 22 and 23, but including graft material on the inside of the

alternate stent, and where the delivery catheter and the guide wire have been removed from

the diseased artery and the alternate self-expanding stent is fully deployed restoring the patency

of the affected vessel.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An expandable stent of the present invention is schematically represented in Figure 1

at 30. The device 30 includes a proximal end 32 and a distal end 34. The device 30 is

depicted as temporarily fitted upon or generally coaxial with a balloon catheter 40 (shown in

ghost outline), having a distal end 42, an expandable balloon 44 and a catheter shaft 46 under

control of a surgeon. The device 30 is also shown closely associated within a portion of an

artery 50 which is partially occluded by a stenosis 52. The surgeon is able to observe the

position of the device 30 using real-time x-ray detection of proximal and distal radiopaque markers 36 and 38 associated with the device 30, and in particular, adjacent the proximal and distal ends 32 and 34, respectively.

As shown schematically in Figure 2, once the surgeon has assured that the device 30

is appropriately located in the lumen of the artery 50, preferably spanning the stenosis 52, the

device 30 can be expanded radially outwardly expanded by inflating the balloon 44 of the

balloon catheter 40. The inflation of balloon 44 is accomplished by application of fluid

pressure to its interior by the surgeon, acting at the proximal end (not shown) of catheter 40

in a manner wich is well known in the art. As balloon 44 expands, device 30 is also expanded

radially outwardly expanded. As the expansion continues, the device 30 and balloon 44

contact and begin to alter the shape of the stenosis 52 of the artery 50. Such expansion is

continued until the stenosis 52 is reformed to a more desirable shape and size, i.e. more nearly

cylindrical, such that patency is restored in the artery.

The relatively narrow, initial radius of the device 30 positioned coaxially, about axis

45 of the balloon 44 and not yet expanded into contact with stenosis 52 of artery 50 is also

schematically shown in cross section in Figure 3. The subsequent situation is schematically

shown in Figure 4, in which the balloon 44 has been inflated and thereby expanded the device

30 and forced the stenosis 52 back against the wall of artery 50. Next, the fluid pressure on

the balloon 44 will be relieved and reduced. The balloon 44 will contract radially toward axis

45. The expandable stent 30, however, generally retains the expanded radius and does not

contract. In turn, the retained expanded condition of the device 30 serves to hold the stenosis

52 out of the channel of the artery 50 and restore patency to the artery 50. Because the device

30 remains expanded but the balloon 44 contracts, withdrawal of the balloon 44 and the

balloon catheter 40 is now possible. Even after the balloon catheter 40 is withdrawn from the patient, patency remains in the artery 50 and more appropriate circulation is possible for the tissues served by the treated artery 50. The device 30 remains as a support or scaffolding for

the artery 50 and may also inhibit reformation of the stenosis 52.

The following definitions are provided to facilitate understanding of the invention and disclosure. As used herein, the term "interconnected" means a physical connection,

particularly as it relates to an interconnection or interconnections between a first structure and

a second structure in which a constant radial thickness is maintained and no change in material occurs. As used herein, the term "radial thickness" means the difference in the distance

between the radius from the axis to an inside facing surface and an outside facing surface. As

used herein, the term "cells" means the structure defining an aperture or a frame about an

aperture. The cells under discussion in this disclosure have frames with a constant radial

thickness and deform in response to radial force, in the case of expandable stents, and in

response to compression or normal expansion to assume an expanded configuration when

expanding from a previously constrained position, in the case of a self-expanding stent. The

frames may have curved sides, many straight sides or combinations of curved and straight

sides. In this particular regard, "straight" means having flat surfaces which reside within a

single plane. As these cells deform, the apertures defined within each respective cell may

increase or decrease in size as the shape of the aperture changes. As used herein, the terms

"helical" and "counter helical" mean paths having many points, each of which is spaced an

equal distance apart from a common axis, such that the path curves in an arc as it traverses an

incomplete external surface residing around the stents of the present invention in any

configuration. As used herein, the terms "ring" and "module" mean a plurality of cells

interconnected around the axis, preferably in series, such that paths generally created by the interconnected cells are generally spaced an equal distance apart from and proceed around the axis. As used herein, the term "shared side" means a structural component which is a member

of two adjacent cells and functions as portion of the frame of each of the cells. As used

herein, the terms "independent rings" or "independent modules" means rings which can deform, for example by expanding on the order of, for example but without limit, a 10% increase in radius, without an adjacent ring or module be expanded. As used herein, the term

"articulating" means that two adjacent rings or modules can "articulate" so as to shift their

respective axes from an orientation where the respective axes have a coincident orientation to

an orientation where the respective axes have a non-coincident orientation thereby establishing

an angle between the respective axes of at least about 5 degrees, preferably about 10 degrees,

more preferably about 20 degrees.

As shown schematically in Figure 5, the device 30 is made up of a plurality of modules

or rings 60 which are closed loops and circumferentially extend about a central axis 45. Each

of the rings 60 has a proximal end 62 and a distal end 64. Each of the rings 60 has at least one

deformation component or expansion cell 66. A cell 66 has a frame defining an aperture

within the frame. The cell 66 in the expandable stent 30 deforms when radial force is applied

Preferably, each ring 60 has a plurality of expansion cells and, most preferably, each

ring consists of a plurality of identical or nearly identical expansion cells, lined in series in the

most preferred embodiments. In the unexpanded condition, as shown in Figure 5, each

expansion cell 66 is characterized by a greater longitudinal extent "L" (71) than

"circumferential" extent "C" (73). In the present embodiment, the longitudinal extent "L" of

the cell 66 generally corresponds to the distance between the proximal and distal ends 62 and 64 of the ring 60.

In preferred embodiments, each of the cells 66 have an upper half or first portion 67a and a lower half or second portion 67b. The first portion 67a, which may be a complex curve

or other form, extending from the distal most extent or point 68 of the cell 66 to the proximal

most extent or point 69 of the cell 66. The first portion 67a and the remainder of the device

30 may be positioned between a first radius and a second, slightly larger radius, from an axis

45a of the ring 60. Initially, the axis 45a (not shown) of each respective ring or module 60

is coincident with the common axis 45 of the device 30. However, is subsequent

embodiments, where the respective rings or modules 60 are only interconnected once, twice,

three times or four times in limited portions of the respective rings 60, the respective rings can articulate with respect to one another, such that respective axes of each adjacent module do not

coincide with one another. The difference between the first and second radii is the thickness

of the wall of device 30. An exception to the constant wall thickness of the device 30,

however, is the thickness of the radiopaque markers 36 and 38 which will be discussed below.

The cell 66 second portion 67b of the cell 66, which is preferably a mirror image of the first

portion 67a and is joined to first portion 67a at its longitudinal extremes, namely the distal

most point 68 and proximal most point 69.

As shown in Figure 6, when the device 30 is expanded radially and outwardly from axis 45, the expansion cells 66 of each ring 60 expand and increase in along its

"circumferential" extent "C". Simultaneously, the cells 66 decrease in their longitudinal extent

"L" and the proximal and distal ends 62 and 64 move longitudinally toward each other and the

upper half 67a moves further away from the lower half 67b.

In this embodiment, the rings 60 of the device 30 are linked at the proximal end 62 to the distal end of an adjoining or adjacent proximally located ring, if any. The link is a small common region, shared by the most proximal extent of each expansion cell 66 of a ring 60 and the most distal extent of each expansion cell 66 of an adjoining proximally located ring 60.

Similarly a small common and shared portion, at the greatest "circumferential" extent, links

each expansion cell 66 of a ring 60 to the adjoining expansion cell 66 of the same ring 60. For

purposes of explanation, the embodiment depicted in Figures 1,2,5, and 6 depicts five rings

60, each with a single row of expansion cells 66 joined circumferentially in series. In this

embodiment, each of the respective circumferentially adjacent cells are joined together at the

adjacent sides in a manner similar to that shown in Figures 12, and the adjacent cells of the

respective adjacent rows are joined together in a manner similar to that shown in Figure 10.

As shown in Figures 7 and 8, it is also possible to form addition expandable stents such

as the device 160 have fewer rings or rows of cells, e.g. the device 160 with three rows 161a,

161b, and 161c of expansion cells 166. Prior to radial expansion, the cells 166 have a greater

longitudinal extent than "circumferential" extent, as represented in Figure 7. When expanded

radially, the device 160 undergoes a change in the cells 166 such that the longitudinal extent

of each cell is reduced but the "circumferential" extent is greatly increased, as represented in

Figure 8.

In other alternative embodiments (not shown), it should be appreciated that stents of

the present invention include as few as one module or ring and as many as 2, 3, 4, 5, 6, 7, 8,

9, 10 or even more rings if practical to provide greater length to the stent. Furthermore, each

ring or module may include any practical number of cells.

In another preferred embodiment, schematically represented in Figure 9A, an

expandable stent 200 of the present invention has multiple rings 260. Each of the rings 260 is a "circumferential" array of expansion cells 266 linked to each of two circumferentially

adjacent cells at their greatest "circumferential" extent. This interconnection or attachment

arrangement is shown in greatly expanded detail in Figure 12. The area joining the two cells

in called an isthmus 267 and may in other embodiments have greater width or height. In this

embodiment, the rings 260 are not linked at the ends or the greatest longitudinal extent of each expansion cell 266. Rather, the links between the respective rings 260 are selective. The

respective ends a some adjacent cells are interconnected and others are not. These two distinct possibilities are shown in greatly expanded detail in Figures 10, which depicts a link or

interconnection between the greatest proximal extent of an expansion cell of one ring and the

greatest distal extent of an expansion cell in the adjacent or adjoining ring, and in Figure 11

which depicts the absence of a link between two expansion cells of adjoining rings, there is no

interconnection between the adjacent cells.

It should be noted that a significant feature of each of the cells of embodiments

discussed herein above, 66, 166 and 266, is the presence of a significant longitudinally oriented strand or portion at some point along the first and second portions (for example 67a

and 67b). Although curvature may be present, the area where a tangent to the inward face

of the frame passes relatively gradually through a longitudinal orientation is quite significant.

This area is perhaps best observed by reference to Figure 12 and in contrast to Figures 10 and

11. Extensive portions of longitudinally oriented strands facilitate reduction of end-to-end

shortening during radial expansion. For that reason, it is believed to be desirable that the cells

or frames have a greater longitudinal length or extend than "circumferential" height or extent.

In certain embodiments it is envisioned that for an expandable stent similar to the device 200 shown in Figure 9, with an overall initial end-to-end length or extent of approximately 16 millimeters and an initial diameter of approximately 1.4 millimeters or about

0.055 inches, cells 266 would have a longitudinal length or extent, proximal to distal, of about 2 niillimeters (which would correspond to about 7 or 8 rings) and a "circumferential" distance

or extent, as measured along the exterior perimeter, or a cylinder wall of the stent, of about

0.7 millimeters to about 0.35 millimeters. A typical row can have from about 4 to about 16

cells, preferably about 6 to about 12 cells. Links between rings might be on the order of 0.033 millimeters or even smaller, in such an embodiment. Longer or shorter, or wider or narrower

links can be useful in alternative embodiments, however, depending on a number of factors

including without limit, the degree to which it is desirable to allow the cells to expand or

compress independent of adjacent cells, or other cells within the same ring or module, an

adjacent module, or within the stent itself.

The expandable stent 200 shown in Figure 9A has seven rings or modules 260, all of

which are not shown in their entirety. Each ring or row 260 has 12 cells and is interconnected

with its immediately adjacent ring or row by links between the respective ends of four cells

in each ring, or two immediately circumferentially adjacent cells on both sides of each

particular ring. The succeeding ring is interconnected or linked to the second of the two first

rings by links between tow subsequent cells on each side. Similarly, the adjacent cells

interconnecting the next ring or row over, are the two cells below that. This pattern of

attachment allows the stent 200 to bend slightly with each ring or row of expansion cells

articulating slightly with respect to each of its immediately adjacent rings, assuming it is not

on either end of the stent, as if each pair of adjacent rings were "hinged" together on opposite

sides. As mentioned, this permits the stent to bend slightly as it passes through twists and

turns in the vessels through which the stent must pass in order to be delivered in a particular procedure. It will be appreciated that the flexibility and strength of the material used to make

the various alternate embodiments can be selected to lend different qualities to the stents of the present invention, among the qualities are strength to provide appropriate "scaffolding"

strength, flexibility to allow for articulation of the stent and, perhaps easy deformation,

expansion or compression, and the like.

Referring now also to Figure 9B, other embodiments of the expandable stents of the

present invention may have similar ring to ring interconnections as previously described, but

hinge on only one side of the stent so that the stent can articulate more fully on the single

hinge. For example, each ring could be joined to each adjacent ring by one, two, three, four

or more links between one, two, three, four or more adjacent cell pairs in each of the

respective adjacent ring pairs. These links may align perfectly on one side of the stent, or they

may rotate spirally around the stent by jumping down one, two, three, four or even more cells,

in interconnections between each successive pair of adjacent rings. The stent 280 shown in

Figure 9B has one link 282 between adjacent cells in each pair of adjacent rings 290, and all

on one side with no rotation. This stent 280 has perhaps the most flexibility to pass through

tortuous twists and turns in coronary arteries, but the independence of the various rings 290, joining together by only a single link, means that the stent will not have strong side to side

integrity between the adjacent rings. Greater side to side integrity will be obtained by placing additional links on the other side of the stent or by increasing the number of links between each

ring on a single side. By adding links, however, especially if they are on opposite sides, the

ability or the rings in the stent to articulate will be reduced. By rotating the links, between the

respective cells in the respective successive adjacent ring pairs, in a spiral fashion around the

stent, the stents will articulate in spiral fashion which may be desirable to deliver a stent through a particularly torturous arterial passageway. By placing radiopaque markers 36' " and 38' " at either end of the stent 280 in the line cells which are joined in series by the links or

interconnections 282 between the respective rings 290, it will be possible for the health care

professional delivering the stent 280 to visualize the rotation of the stent 280, even if it is made

of materials which are not radiopaque, so that the stent 280 can be rotated to accommodate

various turns or twists in the coronary arteries or other vessels through which the stent 280 is

delivered.

As stent 280 articulates, the rings 290 articulate or pivot on the hinge provided by the interconnection between adjacent cells of the respective adjacent ring pairs. Each ring 290 has

a axis 291 a-g. As each of the rings 290 articulate, the axes of the respective rings are no

longer coincident with each other as shown in Figure 9B. (See for example axes 291c and

291d, for rings 290c and 290d, respectively, which in not coincident lines).

Stent 280 also includes a graft material 327 which is shown partially in phantom. The

graft material 327 is secured the stent 280 on the inside of the stent 280 using a threading

technique similar to those which are known in the art (not shown). The preferred graft

materials are Gortex^® or Dacron^® polyester, however, any biologically acceptable materials

known to be suitable graft materials may be used.

Having disclosed the underlying invention, it is believed to be within the skill of the

art to modify dimensions to accomplish an effective practicing of the invention, provided one

considers the factors of ultimate location, the nature and configuration of the pathway to be

used to achieve the ultimate location, the particular material selected for the device, the force

available to deform the device, in the case of expandable stents, and the recoil force which the

device must support in its scaffolding function. It should also be appreciated that the radial thickness as well as the cylindrical surface thickness may be modified within the spirit of the

invention. As will be subsequently understood, at least one method of producing the devices

of this invention provide substantial control over the surface thickness and thereby control over

the stiffness of the device.

In another embodiment shown in Figures 13 and 14, the expandable stent 330 has three

rows 361a, 361b, and 361c of cells 366. The cells or frames 366, differ from the cells of earlier described embodiments in that each cell 366 has a first portion or upper half 372 having

at least three segments instead of a single curve 67a. Specifically, the first portion 372 has a

longitudinally oriented linear or straight segment 374 having a distal end 376 and a proximal

end 378. Extending distally from distal end 378 is a helical segment 382 which has a proximal

end 384 and a distal end 386. Extending proximally from the proximal end of straight segment

374 is a counter helical portion 392, generally a mirror image of helical segment 382 and

having a distal end 394 and a proximal end 396. The longitudinal extent of the cell 366 occurs

between the proximal end 396 of counter helical segment 392 and the distal end 386 of helical

segment 382. The cell 366 also includes a lower half which is a mirror image of the upper half or first portion 372 to complete the frame or cell 366. When the device 330 is expanded

radially from an initial lower profile condition or configuration, as represented in Figure 13,

to that represented in Figure 14, the helical segments 382 and 392 of the first portion 372 and

their mirror images of the second portion are deformed, shortening the longitudinal extent of

the cell 366 and increasing the "circumferential" extent of the cell 366. However, the straight

segments 374 remain substantially undeformed and maintain a generally constant longitudinal

extent or length between their distal ends 376 and proximal ends 378. Note also that the

straight segments 374 also serve a second function as a portion of the circumferentially adjoining or adjacent cell. This is a distinction from the structure schematically represented

in Figure 12 and is further emphasized for the advantages of reducing the amount of material

physically present in the device, and, perhaps, reducing the end-to-end "shrinkage" or reduction in length, when the expandable stent 330 is expanded, thereby increasing the availability of end-to-end stability length consistency. As will be explained subsequently, this

generally constant longitudinal relationship can be exploited to provide improved control over

the end-to-end changes in length occurring in the stents of the present invention during radial

expansion.

As shown in a further embodiment illustrated in Figure 15 in an expanded

configuration, the illustrated portion of a stent 430 has a plurality of rings 460n, 460n+ l,

460n+2 formed of cells 466 having straight segments 474 similar to those 374 in cells 366

shown in Figures 13 and 14. The straight segments 474 have distal and proximal ends 476 and

478, respectively. The cells 466 also have helical segments 482, with proximal and distal ends

484 and 486, respectively, and counter helical segments 492, with distal and proximal ends

494 and 496, respectively. The stent 430 has a limited number of links 498 interconnecting

the distal most extent of a few select cells, at distal end 486 of a helical segment 482, at the

proximal end 496 of opposite helical segment 492, of a cell 466 of the adjacent ring. This

arrangement has substantially double the end-to-end longitudinal shortening, on a per ring

basis, as the embodiment of Figure 14 which can be desirable in certain circumstances.

However, that there are fewer links between the respective adjacent ring pairs allows existing

links 498 to provide a hinge for articulation between the adjacent rings because the links 498

are only present between a limited number of cells of each ring. The number and placement

of links 498 in this embodiment, and the number of cells 466 and rings are the same as those of the stent 200 shown in Figure 9A. It will be appreciated that the placement and the numbers may change, however, just as they may for all other embodiments of the present invention.

Figure 16 shows an another alternate embodiment similar to that shown in Figure 15, but with links 598 connecting distally located longitudinal extremes 586 of cells 596 of ring

560n to an end 578 of a straight segment 574 of a cell 597 of an adjacent double ring

consisting of side by side rings 560n+ 1 and 560n+2. An further line 599 also interconnects

the respective rings, strengthening the hinge upon which the respective rigs may articulate.

This arrangement has somewhat less end-to-end longitudinal shortening, on a per ring basis,

as the embodiment of Figure 14. Again, however, the links 598 provide articulation between the rings 560n and 560n+l because the links 598 and 599 are only present between a limited

number of cells of each ring 560n and 560n+ 1. As with each of the other embodiments, of

this invention the number of cells, rings and links, and the arrangement of cells rings and links

may be varied to accomplish various goals in flexibility, producing stents having strength and

other parameters which may be considered to be desirable for a certain purpose.

As schematically shown in Figure 17A, in another embodiment 500, cells 506 of a ring

510n and an adjacent distal ring 560n+l can also be a hybred between the cells of the prior

embodiments, by including both segments 504, intermediate helical segments 507, and curved

ends 509 at the longitudinal ends. In each mirror image portions halves (upper and lower)

of cells 506, the curved ends form a continuous curve. In this embodiment, the leading and

trailing ends of each of the cells of the rings are blunted and have a reduced tendency to snag

arterial or other tissues as the device is moved through a vessel within a patient. As shown

in Figure 18 which shows a portion of the stent 500 when the cells 506 are expanded from the lower profile configuration shown in Figure 17, the rounded or blunted end structure is

retained after radial expansion and thereby continues to provide a measure of protection for

the innerwalls of the vessels of the patient. Additionally radiopaque markers 536 are added,

as appropriate. Referring now also to Figures 19, 20 and 21 the preferred radiopaque markers 536 of the present invention include rivets 537, installed in receivers 538 having radially

oriented holes to accept a shaft 539 between two rivet head portions 540 of the rivet 537. Links 598 can be extremely short, or in the alternative lengthened. Because the links 508

between rings are present in limited numbers, less than one per cell, the device 500 can articulate between two adjoining rings.

Another embodiment 500' is schematically shown in Figure 17B. In this embodiment,

the device 500' is a single ring with cells 506' similar analogous to those of Figure 17 A. The

cells 506' , in each upper and lower half have a straight, longitudinally oriented segment 504' ,

a helical segment 507' , a counter helical segment 508' blunt curved ends 509' and 511 ' at the

longitudinal ends of the cell. The upper and lower halves are mirror images. The straight

segment 504' is a shared segment between circumferentially adjacent cells 506'.

The present invention also includes a method of preparing a stent. The method includes

providing a segment of cylindral walled material from which the stent will be made.

Depending upon the type of stent to be made, any of the materials herein discussed or other

well known materials may be used depending upon the particular characteristics desired in the

stent to be made. The stent is prepared by removal of material from the cylindrical wall which

will not be part of the stent to be formed. This may occur by mechanically cutting away

material. Preferably, however, the cutting or material removal is more automated. A

computer aided laser cutting device is one option. A computer aided water-jet cutting device is another option. In each case, software which guides the cutting tool will assure that only

the material which is intended to be removed, will be removed. A removal technique is

chemical etching of the cylinder wall. The portion of the cylinder to be retained as a part of the stent is protected from exposure to the chemical etching process. For example, in the case

of a metallic stent, an etching agent might be one of a number of acids which are well known

in the art. A chemically protective agent, for example, a hydrophobic coating, such as a

wax, may be applied over the entire exterior surface of the cylinder. Next the protective

coating is removed mechanically using a computer aided water jet cutting device, or the like,

where etcliirig is desired. If greater surface thickness is desired, wider areas need to be

protected, if thinner, then narrower areas are protected. Alternatively, other means of

selectively applying protective coatings, for example photographically based methods, which

are well known in the etching arts, may be used. Finally, the partially protected cylinder is

immersed in an acid bath. Etching occurs throughout the interior cylinder surface but only at

selected portions of the exterior. When the etching has proceeded to the extent that the etching

from exterior and interior have fully removed appropriate portions of the cylinder, the piece

is removed from the acid. Next, the protective coating is removed. If the coating is wax, the

wax may be removed by heating or by a wax solvent which does not further affect the metal.

Chemical etching is a suitable production method for low volume production. Higher volume

production is thought to be more suitably achieved through the use of computer aided laser

etching. The availability of using wider or narrower surface thickness, as well as different

tubing wall thickness is considered an important means of obtaining stiffness or easier

deformability in the desired devices of the present invention. Generally, thin wall tubing is

believed to be preferable, but not absolutely required. Provision for accepting radiopaque markers, preferable in the form of rivets can also occur in the etching or material removal method. For example, the generation of a hole 535 for accepting a radiopaque marker rivet 537 might occur by etching or cutting, or by a separate drilling or punching operation. A preferred material from which expandable stents of this invention may be prepared

is without limit stainless steel, particularly type 316 stainless steel, but gold, platinum,

tantalum, silver and the like are also believed to be suitable. Desirable features of the

material selected are deformability and the ability to hold the shape once deformed.

The radiopaque markers may be of tantalum or other well known radiopaque materials

such as gold, platinum or the like. Even though the main stent or other prosthesis is formed

from a radiopaque material, the small quantity of such material present may indicate the need

for the more massive markers to enhance delectability. Preferably such markers are placed

on first and last rings of a stent according to this invention in the manner illustrated in Figures

1-2. In this way, the respective ends of stents made of materials which are not radiopaque will

be visually identifiable in the cath lob during normal procedures.

It will be appreciated that cells of the type disclosed herein above, may be

interconnected in rings of any number of cells and that the manner of interconnection between

such cells may vary. It will also be appreciated that the present invention also includes self-

expanding stents. These stents can have all of the structural characteristics of any of the

expandable stents herein described, except that the materials used will be high memory

materials generally known to be suitable for self -expandable stents, and these stents will

expand from their lower profile configuration when constrained, and will not require the

application of outward force applied radially from within the stent, for the stent to expand to a larger profile having a greater radius, diameter and circumference. Self -expanding stents of

the present invention may be made in the larger configuration out of materials which have high memory characteristics such as superelastic polymers or alloys, spring steel and the like, using

the aforementioned etching methods and devices. In this case, however, the stents must be compressed and then constrained in a lower profile configuration for delivery into the diseased

vessel. In the case of nitinol alloys, however, a small cylinder of nitinol may be etched to

provide an expandable device which may be expanded and then annealed at a sufficiently high

temperature to create a memory within the nitinol stent in the expanded configuration.

Referring now to Figures 22-23, a general description of the method of delivery of

these self-expanding stents is provided. A representative expanding stent 30' having the same

general structural characteristics as the expandable stent 30 illustrates in Figures 1-4, but being

made from different materials which have different characteristics is shown schematically in

Figure 22 within a delivery catheter 110. The catheter 110 includes a delivery sheath 115

secured upon a guide wire 120. The sheath 115 acts to constrain the self-expanding stent 30'

until the sheath 115 is positioned within the stenotic region 52' of the vessel 50' so that the

self-expanding stent 30' can be released to reduce the obstruction 53' within the vessel 50' and

restore the patentcy of the vessel 50' . Once properly positioned, the sheath 115 is opened as

shown in Figure 23. The stent 30' is then released from the delivery catheter 110 and is no

longer constrained. Once released, the self-expanding stent 30' expands as much as possible

within the limits defined by the vessel 50' and the force applied by the expanding stent 30' on

the inner walls of the vessel 50' . Once the stent 30' is released, the delivery catheter 110 can

be removed from the vessel 50' by the health care professional conducting the procedure. The

self-expanding stent 30' also includes proximal and distal radiopaque markers 636 and 638. In preferred embodiments, the self -expanding stent will be flexible, perhaps at least partially because of the inclusion of the structural characteristics which lend themselves to easy

articulation between the respective rings of the stent 30' , or perhaps the materials in use. In

the two cases, it is likely that the stent 30' will be at least as likely as not to be more flexible

than the delivery sheath 115 and the delivery catheter 110, so as to enable the health care

professional to deliver the stent 30' to vessels 50' which are remote and require passage

through torturous passageways in the various arteries of various idiosyncratic patients.

Further embodiments of the present stents may include a graft material (similar to that

shown in Figure 9b) which is secured either the inside or the outside of the stent in various manners which are well known in the art. As used herein, the term "graft material" means a

biologically compatible material through which living tissues can grow so as to incorporate the

graft material into adjacent living tissue. The material can be linen, Gortex^® or PTFE,

Dacron^® polyester, other suitable biologically compatible materials, or the like.

Referring now to Figure 24, a self-expanding stent 30" having graft material 327'

attached to the stent 30" within its inner lumen, is shown schematically deployed within a

coronary blood vessel 50". The graft material 327' is secured the stent 30" on the inside of

the stent 30" using a threading technique similar to those which are known in the art. It will

be appreciated that the graft material may also be secured to, or even loosely associated with,

the outside of alternate stents (not shown) of the present invention. The preferred graft

materials, as discussed above, are Gortex^® or Dacron^® polyester, however, any biologically

acceptable materials known to be suitable graft materials may be used. The alternate self-

expanding stent 30" also includes proximal and distal radiopaque markers 636' and 638' . It is understood that even though numerous characteristics and advantages of various embodiments of the present invention have been set forth in the foregoing description, together

with details of the structure and function of various embodiments of the invention, this

disclosure is illustrative only and changes may be made in detail, especially in matters of shape, size and arrangement of parts, within the principles of the present invention, to the full extent indicated by the broad general meaning of the terms in which the appended claims are

expressed.

Claims

WHAT IS CLAIMED IS:

1. An expandable stent, the stent being expandable by enlarging an expandable balloon positioned within the stent, the expandable stent comprising:

a plurality of modules, each of the modules having a plurality of individual cells radially interconnected to form a ring of individual cells interconnected to each other in series,

each of the individual cells including a continuous strand of a material, the continuous strand

of material in each cell being interconnected with itself so as to surround a space central to the

interconnected strand and define a plurality of sides, wherein portions of any of the plurality

of sides can be shared by adjacent cells in the ring, the material being deformable such that the

ring can be deformed from a first configuration, wherein the ring has a first circumference,

to a second configuration wherein the ring has a second circumference greater than the first

circumference;

each cell having an upper half and a lower half, the upper and lower halves being

joined together at respective first and second ends, wherein the plurality of modules includes

at least first and second modules, the individual cells of the first module are first module cells

and the individual cells of the second module are second module cells, the modules being

oriented side by side such that the second ends of the first module cells are located proximate

the first ends of the second module cells and at least one of the plurality of second ends of the

first module cells is interconnected with at least one of the plurality of the first ends of the

second module cells, such that at least one cell of the first module is interconnected with at

least one cell of the adjacent second module, and wherein the respective modules can articulate

relative to one another.

2. The stent of claim 1 , wherein the upper half and lower half of each cell are mirror images of each other.

3. The stent of claim 1 , wherein the material of the continuous strand of each cell of the

stent is selected from the group consisting of tantalum, palladium, silver, gold, and stainless

steel.

4. The stent of claim 1, wherein each cell has a greater longitudinal extent than

circumferential extent in the first configuration.

5. The stent of claim 1, further comprising at least one radiopaque marker.

6. The stent of claim 1, further comprising a graft material.

7. A prosthesis comprising:

a sequential array of a plurality of independent rings, each of the independent rings

having a first generally circumferential configuration defining a longitudinal axis and having distal and proximal ends, and each of the rings including at least one deformation component

allowing the ring to be deformed to a second generally circumferential configuration when

radial force is applied to the ring, wherein the deformation component includes a frame

defining an aperture surrounded by the frame, the frame and aperture having a greater

longitudinal extent than circumferential extent in the first generally circumferential

configuration; and physical connections between rings of the plurality linking the distal end of at least one ring to the proximal end of an adjacent ring of the sequential array, each of the rings being interconnected in series with at least one adjacent ring within the sequential array,

wherein at least two adjacent rings can articulate relative to one another such that the

longitudinal axes of the respective adjacent rings are non-coincident when said adjacent rings

are articulated relative to one another.

8. The prosthesis of claim 7, wherein the first circumferential structure is bounded by a region defined by a first cylinder, having a first radius, and a second cylinder, having a second

radius different that first radius, the difference between the radii being the radial thickness of

the prosthesis, wherein the prosthesis is characterized by a substantially uniform radial

thickness.

9. The prosthesis of claim 8, wherein each of the deformation components are identical.

10. A method of making a prosthesis comprising the steps of:

(a) providing a cylindrical walled tube, the tube defining an axis; and

(b) eliminating non-contiguous portions of material from the cylindrical walled tube

to leave a desired structure, the desired structure including:

a plurality of individual cells radially interconnected to form a ring of individual

cells interconnected to each other in series, each of the individual cells including a

continuous strand of a material, the continuous strand of material in each cell being

interconnected with itself so as to surround a space central to the interconnected strand

and define a plurality of segments, wherein portions of any of the plurality of segments can be shared by adjacent cells in the ring, the material being deformable such that the ring can be deformed from a first configuration, wherein the ring has a first

circumference, to a second configuration wherein the ring has a second circumference

greater than the first circumference; each cell having an upper half and a lower half, the upper and lower halves

being joined together at respective first and second ends.

11. The method of claim 10, wherein the step of eliminating material includes computer

aided laser etching.

12. The method of claim 10, wherein the step of eliminating material includes chemical

etching and providing an etch resistant protective coating upon desired structure to be retained

in the resulting prosthesis.

13. A self-expanding stent, the stent being compressible to a lower profile having a smaller

longitudinal diameter from a higher profile having a larger longitudmal diameter, such that the

stent will assume the larger profile when unconstrained, the stent comprising:

a plurality of modules, each of the modules having a plurality of individual cells

radially interconnected to form a ring of individual cells interconnected to each other in series,

each of the individual cells including a continuous strand of a material, the continuous strand

of material in each cell being interconnected with itself so as to surround a space central to the

interconnected strand and define a plurality of sides, wherein portions of any of the plurality

of sides can be shared by adjacent cells in the ring, the material being a high memory material such that the ring can be compressed from a first configuration, wherein the ring has a first circumference, to a second configuration wherein the ring has a second circumference less than

the first circumference; each cell having an upper half and a lower half, the upper and lower halves being

joined together at respective first and second ends, wherein the plurality of modules includes

at least first and second modules, the individual cells of the first module are first module cells

and the individual cells of the second module are second module cells, the modules being

oriented side by side such that the second ends of the first module are located proximate the

first ends of the second module and at least one of the plurality of second ends is interconnected with at least one of the plurality of the first ends; wherein at least one cell of

the first module is interconnected with at least one cell of the adjacent second module, and

wherein the modules can articulate relative to one another.

14. The stent of claim 13, wherein the upper half and lower half of each cell are mirror

images of each other.

15. The stent of claim 13, wherein the material of the continuous strand is a superelastic nitinol alloy.

16. The stent of claim 13, wherein the cells have a greater longitudinal extent than

circumferential extent in the first configuration.

17. The stent of claim 13, further comprising a graft material.

18. The stent of claim 13, further comprising at least one radiopaque marker.

19. A self-expanding stent, the stent being expandable from a second smaller profile to a

first larger, the stent comprising: a plurality of individual cells radially interconnected to form a ring of individual cells

interconnected to each other in series, each of the individual cells including a continuous strand

of a material, the continuous strand of material in each cell being interconnected with itself so as to sunound a space central to the interconnected strand and define a plurality of segments,

wherein portions of any of the plurality of segments can be shared by adjacent cells in the ring,

the material being compressible such that the ring can be compressed from a first

configuration, wherein the ring has a first circumference, to a second configuration wherein

the ring has a second circumference less than the first circumference, wherein the ring will

expand to the first configuration when the stent is unconstrained;

each cell having an upper half and a lower half, the upper half being a mirror image

of the lower half, the upper and lower halves being joined together at respective first and

second ends.

20. The stent of claim 19, wherein the upper half and lower half of each cell are mirror

images of each other.

21. The stent of claim 19, wherein the material of the continuous strand is a superelastic

nitinol alloy.

22. The stent of claim 19, wherein the cells have a greater longitudinal extent than

circumferential extent in the first configuration.

23. The stent of claim 19, further comprising a graft material.

24. The stent of claim 19, further comprising at least one radiopaque marker.

25. A method of making a prosthesis comprising the steps of:

(a) providing a cylindrical walled tube made of a superelastic nitinol alloy, the tube

defining an axis;

(b) eliminating non-contiguous portions of material from the cylindrical walled tube

to leave a desired structure, the desired structure including: a plurality of individual cells radially interconnected to form a ring of individual

cells interconnected to each other in series, each of the individual cells including a

continuous strand of a material, the continuous strand of material in each cell being

interconnected with itself so as to surround a space central to the interconnected strand

and define a plurality of segments, wherein portions of any of the plurality of segments

can be shared by adjacent cells in the ring, the material being deformable such that the

ring can be deformed from a first configuration, wherein the ring has a first

circumference, to a second configuration wherein the ring has a second circumference greater than the first circumference; each cell having an upper half and a lower half, the upper and lower halves

being joined together at respective first and second ends;

(c) expanding the ring from the first configuration to the second configuration; and (d) heat treating the ring sufficiently to anneal the nitinol alloy so that it will

assume the second configuration when it is unconstrained.

26. The method of claim 25, wherein the ring is one of a plurality of rings, the rings of the

plurality being interconnected by selected remaining portions of cylindrical walled tube, and

the interconnected rings are linked such that the rings modules can be articulated relative to

each other and allowing at least one of the rings to be moved relative to the original axis.

27. The method of claim 25, wherein the step of eliminating material includes computer aided laser etching.

28. The method of claim 25, wherein the step of eliminating material includes chemical

etching and providing an etch resistant protective coating upon desired structure to be retained

in the resulting prosthesis.