WO1999017682A1

WO1999017682A1 - Desirable expandable stent and technology of its manufacturing

Info

Publication number: WO1999017682A1
Application number: PCT/IL1998/000160
Authority: WO
Inventors: Valerian Voinov; Robert Golub
Original assignee: The Israeli-Usa Foundation, Ltd.; Inter-Med, Ltd.
Priority date: 1997-10-05
Filing date: 1998-04-02
Publication date: 1999-04-15
Also published as: AU6745098A; IL121882A0

Abstract

This invention is a thrombo-resistant expandable stent (15) including a coiled tube (16), the tube (16) formed from a thin profiled metallic strip (10) having flanged opposite edges (11, 12) forming a kinematic link (17) with a small hollow bore (18), and the bore (18) accommodating a bio-absorbable local drug delivery constructive element (19). Constructive element (19) can be loaded with regulated concentrations of anti-thrombotic, anti-proliferative or other therapeutic agents for sustained local drug delivery. Upon rolling up of the tube (16) a hollow is marked in a shape of a helical groove along the geometrical axis of the stent (15). Upon expansion of the stent (15) the preliminary geometrical contour (13) of the rigid elements executed on the coiled tube (16) outward surface (21), is transformed into honeycomb cells (24) providing for the development of force according to vessel shape.

Description

DESIRABLE EXPANDABLE STENT and TECHNOLOGY of its MANUFACTURING Field and Background of the Invention The present invention relates to medical technology, particularly to expandable cardiovascular stents, which are intended for the radical arterial lumen recovery with

subsequent restoring of the normal blood flow. In the present application the term

"stent" refers to the device designed to expand the blood vessel and to maintain the achieved size of lumen. Traditionally, stents are delivered to the target area in the

cardiovascular system on the inflatable balloon located on the tip of a transluminal

catheter. Then, the balloon is inflated leading to the expansion of the stent thereby widening the lumen of the vessel. Other less common systems for stent delivery also

exist.

Most of the existent stents are made from metals. The examples of common designs described in patents are: US 4.733.665, US 4.969.458, US 5.102.417, US 5.195.994,

US 5.513.444, WO 91FRO13820. Certain properties of any metallic surface lead to

thrombogenicity of the stent once it is implanted within the human cardiovascular system. Therefore, one of the important direction the stent development is the

improvement of the stent thromboresistance because this would reduce the need in systematic anticoagulation therapy thereby reducing complication rate after stent

implantation. In the present, none of the metallic stents designs have achieved the

delicate balance between the desired durability to sufficiently support the vessel wall

and flexibility to reduce the thrombogenicity and intimal hyperplasia. Thus, there is

a substantial need for anticoagulation and thrombolitic therapy following stent implantation. Another common flaw of metallic stents is an unequal distribution of forces along the surface of a stent upon its expansion due to the complexity of geometrical shapes of

stent's rigid elements. This lead to the unpredictable redistribution of the pressure to the vessel wall with subsequent additional damage to it. In an attempt to overcome this

unwanted effect higher pressures are used for the inflation of the balloon which leads to

a certain alteration of the stent geometry upon the inflation which affects the shape of

the vessel through activation of processes of intimal hyperplasia and thrombosis.

The next substantial disadvantage of existent metallic stent models is the presence of the

rigid common element between the longitudinal and diametrical components of a stent.

This significantly reduces the flexibility of a stent, limiting its biocompatability with the

adjacent vessel wall. This limitation becomes particularly prominent in coronary

arteries where blood flow parameters are constantly changing due to their state of

continuous motion together with beating heart. As a result of the limited biocompatabi -

lity the clinical outcome of stenting worsens. More recent stent designs try to address

the above-mentioned flaws by proposing metallic stents, coated with various polymers.

Some of these stents include coating, which contains allegedly antiproliferative and

antithrombotic drugs to be released locally into the vessel wall.

Another models have bioabsorbable coatings. However, presently used polymers elicit

some inflammatory reaction, which narrows the lumen.

Another attempt to widen the clinical applications of stents is lowering the profile of

stents and the minimal size of the implanted stent.

Nevertheless, all stents have the lowest diameter of ~ 2 mm upon expansion due to

limitations of the existent manufacturing technology. The latter, based mainly on laser

technology, remains "the Achilles heel" of stenting due to its high cost, and resulting in the relatively rough surface of the stent leading to the vessel wall damage. In summary, the "ideal" stent should possess the following high quality properties:

flexibility, trackability, low profile, visibility in the X-ray, thromboresistance,

biocompatability, reliable expandability, wide range of available sizes, optional capability of the local drug delivery, and biodegradable coating (see, P.Ruygrok and

P.Serruys Intracoronary stenting. "Circulation". 1996; 94; 882-890). These features

will widen clinical applications of stenting, enable the reduction of unwanted effects,

and ultimately improve the clinical outcome.

The Prior Art

The most effective technical solution for the slotted tube stents, combining both

flexibility and radial durability is proposed in the patent application PCT/IL

96/00148 filed on 12.11.1996.

In the above mentioned invention the constructive element, which provides the radial

strength of the stent, is constructed in a form of a series of circular bands (2, Fig. 1),

disposed over a common longitudinal axis with a number of curvilinear components (3),

which plays a role of compensators of the diametrical deformation (CDDs). CDD

comprises of at least two rods (4), conjugated in the apex (5) by a V-shaped connection.

The loose ends of the rods (4) are closed by the undeformable segments (6) of the

circular bands (2).

Upon the expansion of the stent (1), resulting from the outward forces from the inflating

balloon, CDDs enable the increase of the diameter of each circular bands (2) up to

a certain predetermined size where the degree of the diameter increase is proportional

to the number of the CDDs. The maximal diameter of the circular band (2) corresponds

to the inner diameter of the vessel wall, and the circular band (2) in this position takes shape of almost ideal circle with width of one CDD rod. The number of circular bands varies from 2 to 40 depending on the length of the stent.

The longitudinal flexibility of the stent is based on the separation of the static and dynamic functions between the circular bands (2) and the constructive elements of

flexibility (7) of the stent, which connect the CDDs. Where the circular band (2) with

CDD performs only static function of preventing the vessel wall from collapsing, the

constructive element of flexibility (7) of interconnecting zone possesses the significant

dynamic function as well, because it needs to reflect the differences in the various

segments of the vessel. On another hand, the latter element (7) does not transfer

the deformation to the circular bands (2). Therefore, it plays a role of the compensator

of the longitudinal deformation (CLD).

CLD (7) comprises of two rods (8), conjugated at the apex (9) by V-shaped 90 degree

oriented connection. All the rods (8) have the same length and their loose ends are

closed by the undeformable segments (6) of the circular bands (2). The degree of

flexibility of the stent depends on the sum of lengths of all CLD rods. Therefore, the

optimal positioning of the CLDs between CDDs during manufacturing becomes very

important to achieve the maximum possible number of CLDs on each stent.

Fig. 2 shows that upon the expansion of the stent only CDDs change their geometrical

forms, whereas CLDs, connected to the undeformable segments (6), do not receive

the deformation force from the expansion. On another hand, since all junctions (4) of

the CDDs have the same size, the stent maintains the cylindrical shape after the expansion.

The discussed invention also describes the effective approach to increase the

longitudinal flexibility of a stent to match the changes of the shape of the pulsating vessel. This can be accomplished by producing CLDs from the bioabsorbable polymer material. However, that patent application does not describe any particular engineering

solution to this idea, probably, because the described model is a slotted tube stent, which

almost excludes the possibility of incorporating biodegradable materials. Another limitation of the slotted tube stent design comes from certain short-comings of

manufacturing process, which is most of cases is a laser technology. Particularly, this

technology limits the accuracy of the length of CDD rods, the radius of the curve in

the V-shaped structures, and the optimal position of the CDDs and CLDs in the original

shape of the stent. This may potentially lead upon the expansion of the stent in the

moving vessel to the deformation of the stent with subsequent activation of the processes

of intimal hyperplasia and thrombosis.

Taking into consideration that the discussed model of the stent is the closest one

the "ideal" stent among slotted tube stents, this design nevertheless contains some

unresolved flaws, which need to addressed to improve the clinical outcome and minimize

such unwanted effects of stenting as thrombosis and restenosis. Therefore, the future

"ideal", or desirable expandable stent must possess the following characteristics:

1. Maximal radial strength.

2. Correspondence with the shape of the vessel.

3. Compliance to the pulsating vessel.

4. Low profile.

5. Accommodation of additional angioplasty.

6. Visibility in X-rays.

7. Capability of local drug delivery.

8. Low manufacturing costs with a high quality easily reproducible manufacturing technology, thus meeting the modern requirements of a cost-effective medical device.

Summary of the Invention

The present invention consists of a stent design with improved thromboresistant

properties, which alleviates the need for systematic anticoagulation therapy, and

thereby also reduces bleeding and vascular complications. This aim is achieved by the fact that the Desirable Expandable Stent is made as

a coiled tube with the possibility of changing in space the geometrical axis form.

The coiled tube is rolled up from a thin profiled strip in such a way that the flanged

opposite edges of the said strip sides form a kinematic link with a small hollow bore,

the shape and geometrical sizes of which are preliminary regulated.

On the outward surface of the said coiled tube a plurality of rigid elements in a shape

of honeycomb cells is formed. Upon the expansion of the stent, the transformation of

preliminary geometrical contour of the rigid elements into the honeycomb cell along

the said coiled tube surface occurs corresponding to a vessel shape with the even

distribution of the applied force along the stent perimeter, while the radial supporting

ability of the stent becomes maximal.

Upon the rolling up of the said coiled tube in the said kinematic link a geometric hollow

in a shape of a helical groove deployed on the inner surface along the said stent

geometrical axis.

The said stent is provided with a bioabsorbable constructive element, which could be

loaded with antithrombotic or antiproliferative agents in regulated concentration for

sustained local delivery. The said bioabsorbable local drug delivery constructive element

is accommodated in the small hollow bore of the said kinematic link upon the rolling up

of the coiled tube. In the beating heart, in each of the systole-diastole dynamic cycle the flanged opposite edges of the said kinematic link are drifting in the small hollow bore against each other.

This facilitates the longitudinal compliance of the said stent body and allows to exert a mechanical influence of the said flanged opposite edges on the said bioabsorbable local drug delivery constructive element accommodated in the small hollow bore. In the said

stent the exterior part of the said kinematic link is made over the said coiled tube's

outward surface generating line. It makes possible for the said kinematic link's

projected exterior part to locally integrate into the vessel wall upon the expansion of

the stent.

Before the expansion, the said stent has a diameter, which corresponds to the one of

the non-inflated balloon placed on the tip of the catheter. In this case the width of the preliminary contour of the said rigid elements is a function of the vessel inner surface

diameter.

The said stent is visible in X-rays due to the corresponding marks made on the surface

of the said bioabsorbable local drug delivery constructive element.

Technological process of the said stent's manufacturing includes the following

operations:

- cold plastic stamping of rigid elements with preliminary geometric contour on the

outward surface of a thin metallic strip;

- profiling a shaped cross-section of a flanged opposite edges on the sides of the said

metallic strip with the simultaneous smoothing of metal surpluses on its outward

surface after the cold plastic stamping operation;

- rolling up of a coiled tube from the said profiled metallic strip with a simultaneous

accommodation of a bioabsorbable local drug delivery constructive element in a small hollow bore of a formed kinematic link of the said coiled tube;

- fixing of a first end face surface of the said coiled tube and a first end of the said bioabsorbable local drug delivery constructive element;

- separation of the ready device;

- fixing a second end face surface of the said coiled tube and a second end of the

bioabsorbable local drug delivery constructive element.

It is possible to manufacture the said stent in an automatic cycle of the said

technological operations.

The proposed Desirable Expandable Stent possesses the following characteristics:

1. Maximal radial supporting ability.

2. The unique transformation of the stent geometrical design according to the concept

of the uniform force development corresponding to the vessel shape with the guaranteed

even distribution of the applied force along the stent perimeter.

3. Compliance to the pulsating vessel.

4. Low profile.

5. Accommodation of additional angioplasty.

6. Visibility in X-rays.

7. Capability of bioabsorbable local drug delivery.

8. Manufacturing of the samples with a diameter from 2.0 to 5.5 mm.

9. Manufacturing of the samples with a length from 10 to 80 mm.

10. Manufacturing of the devices with a highly productive industrial technology,

meeting the modern requirements of the automated serial production.

11. High surface purity and quality of the devices.

12. Low manufacturing costs. The proposed stent design represents medical device executed by joining metallic, scaffolding, and bioabsorbable, therapeutic, parts with a possibility for each of these

parts to fulfill an independent functional load.

The proposed stent design possesses a complex of the desirable thromboresistant

properties, and therefore, more fully meets the requirements of interventional cardiology. The proposed stent design allows using in practice the scientific

achievements on the effective healing of the traumatized vessel wall after angioplasty.

The proposed stent design could be executed taking into account the essential

improvement of technological and quality level of the manufactured device, meeting

the market requirements, i.e. reduction of the device cost.

Brief Description of the Drawings

The invention is herein described with the help of an example and references to

the accompanying drawings, wherein:

Fig. 1 shows the stent-prototype design before the expansion.

Fig. 2 shows the stent-prototype design after the expansion.

Fig. 3 shows the profiled metallic strip with the stamped rigid elements' preliminary

geometrical contour along its the outward surface.

Fig. 4 shows the shape of the cross-section of the profiled metallic strip in accordance

with Fig. 3.

Fig. 5 shows the rigid element' preliminary geometrical contour as hexahedrons of

an irregular shape, which form the profiled metallic strip width in accordance with

Fig. 3. Where b - the width of the irregularly shaped hexahedrons.

Fig. 6 shows the proposed stent design before expansion.

Fig. 7 shows the kinematic link cross-section before the expansion of the stent. Fig. 8 shows the proposed stent design after the expansion. Fig. 9 shows the kinematic link cross-section after the expansion of the stent.

Fig. 10 shows the honeycomb-shaped rigid elements on the outward surface of the coiled tube after the expansion. Where B - the width of the uniformly shaped hexahedrons.

Specific Description

Fig. 3 shows a thin metallic strip (10) with a shaped flanged opposite edges (11) and

(12), which are diametrically curved and are 90 degree oriented on the sides.

Fig. 4 shows a cross-section of the said strip.

Outward surface rigid element' geometrical contour is stamped on the profiled metallic

strip (10), forming irregularly shaped hexahedrons (13). On the shown example (fig. 5)

the strip's width is formed by two hexahedrons (13), located in a staggered order along

the length of the strip (10).

Upon the rolling up of the coiled tube, the end surface (14) are being fixed and cut off, while preserving the integrity of the hexahedrons' outward geometrical contour.

On Fig. 6 and 7 the stent 15 is shown before the expansion and is made up of the

profiled metallic strip (10) in a form of a coiled tube (16).

The coiled tube, being an elastic helical spring, has a high longitudinal compliance to the

deformation force and upon the curve can change the geometrical axis form.

Upon the rolling up of the coiled tube (16), the flanged opposite edges (11 and 12) of the

profiled metallic strip (10) sides form the kinematic link (17) with small hollow bore

(18). The kinematic link (17) and the hollow bore dimensions can be specifically

calculated to allow one or several bioabsorbable local drug delivery constructive

element (19) be located in it, while at the same time the flanged opposite edges (11 and

12), that form the kinematic link (17), could shift against each other upon the bending force action. This is predetermined by way of changing the metallic strip's (10) geometrical sizes and shapes (Fig. 4) before performing the technological operation of profiling.

The exterior part (20) of kinematic link (17) is made on the outward surface (21) of the generating line of the coiled tube (16). The constructive element (19) of bioabsor¬

bable drug delivery (Fig. 6,7), accommodated in the kinematic link's small hollow

bore (18), is made of the polymer thread, which could be loaded with antithrombotic,

antiproliferative, or other therapeutic agents in high concentration for sustained local

delivery into the vessel wall. On the outward surface of the polymer thread (19)

the marks (22) are made, which are visible in X-rays. Upon the rolling up of the coiled

tube (16) in the kinematic link (17) a geometrical hollow in a a form of the helical

groove (23) is marked (Fig. 7), which is located on the inner surface along the geometri¬

cal axis of the stent (15).

The stent diameter before the expansion is determined taking into account the require¬

ment of its dense planting on the non-inflated balloon. The assembly corresponding of

the stent and non-inflated balloon is established by the following simple formulas:

d = bn/π and D = Bn/π ,

where d - stent diameter before the expansion; D - stent diameter after the expansion,

corresponding to the diameter of the inner vessel surface; b - width of the irregular

shape hexahedron (Fig. 5, 13); B - width of the regular shape hexahedron (Fig. 10, 24);

n - number of the hexahedrons (13) or (24) in a coil (25) of the coiled tube (16).

Fig. 8 and 9 shows the stent (15), which is expanded in the vessel according to the

commonly accepted method used in the balloon expandable stents.

It could be seen that the transformation of the rigid elements' geometrical contour takes place upon the inflation of the balloon. Now on the outward surface (21) of the stent (15) the regularly shaped hexahedrons or honeycomb cells (Fig. 10, 24), which are the unique

natural rigid structures, are formed from the irregularly shaped hexahedrons (13). At the same time the transformation of the rigid elements' preliminary geometrical

contour into the honeycomb on the outward surface (21) of the stent (15) is performed

according to the design, containing the concept of the uniform development of the force

corresponding to the vessel shape.

If the outward force is applied to any point of the expandable stent outward surface (21)

it is evenly distributed along the honeycomb cells (24), perimeter in accordance with the

known principles of mechanics, then parted along the perimeters of the contiguous

honeycomb cells and further along the uniform cellular design of the stent body.

Therefore, the stent, after the expansion and with the honeycomb cells (24) formed on

its outward surface (21), possesses the maximal radial supporting ability. The possibility of obtaining relatively small cells decreases the chance of tissue prolapse and plaque protrusion into the lumen. These smaller units account also for

a higher radial resistance and decreased wall trauma by decreasing the local pressure

on the vessel wall. Since the transformation of the rigid elements' preliminary contour

into honeycomb cells (24) is executed from the hexahedrons (13), the stent does not

need to use high pressures for the expansion of the balloon.

Upon the expansion of the stent, the exterior part part (20) of the kinematic link (17),

made over the generating line of the stent outward surface (21), is introduced into

the vessel wall, thus performing an additional angioplasty. Since the elevation of

the exterior part of the kinematic link (20) over the generating line of the stent outward

surface (21) has a sufficiently small value, the insignificant concentration of stresses caused by the applied force action could be neglected. At the same time, the presence of the exterior part (20) of the kinematic link (17), that interrupts continuity of the stent outward surface (21) and its helical development along the geometrical axis, increases

the maneuverability of the transluminal catheter and facilitates the placement of

the stent precisely into the site.

In the beating heart the flanged opposite edges (11 and 12) can shift against each other

in the small hollow bore (18) of the kinematic link (17). This facilitates the general

longitudinal compliance of the stent body.

The kinematical structure of the coiled tube (16) is determined by the closed coils (25),

which have no rigid mechanical connection between them, and, therefore, upon the

applied deformation force are able to change the radius of the curve of the stent. Upon

the bending of the stent, the contiguous coils (25) curve and, in addition, shift

longitudinally in the small hollow bore (18) of the kinematic link (17) against each other

in such a way, that the radius of the curve along the stent's outward surface (21) exceeds

radius of the curve along its inner surface. At the same time, the difference in the values

of the compared radii of the curve corresponds to the tortuous anatomy of diseased

vessel. As a result, the stent bends and changes the form of the geometrical axis in

accordance with the spatial displacements of the pulsating vessel.

Thus, the proposed stent design , possessing the combination of flexibility and radial

strength factor, is executed according to such kinematic scheme, where the stent does

not shrink radially upon the applied force and, at the same time, preserves the natural

curve of the vessel. Also, the force, which is evenly distributed along the stent perimeter,

and decreased local pressure at its ends substantially reduce the possibility of restenosis,

while the correspondence to the curvilinear shape of the vessel and the close fitting against the vessel wall make it possible to perform stenting of complicated long segments and to decrease turbulence.

Besides, in every systole-diastole dynamic cycle of the beating heart the flanged

opposite edges (11 and 12) in the kinematic link's small hollow bore (18) have

the possibility to mechanically influence the polymer thread (19). This can help the

point distribution and the gradual unloading of therapeutic fragments from the polymer

thread (19) to the lumen vessel.

When the small hollow bore (18) of the kinematic link (17) is packed with the polymer

thread (19), the flexibility of the stent (15) does not change, and the junction made

of the flanged opposite edges (11 and 12) in the small hollow bore (18) of the kinematic

link (17) works as the elastic hinge. In this case the polymer thread places in the vessel

wall and does not nave any functional constructive load and is implanted exclusively

for the local drug delivery into the traumatized sections of the vessel.

The marks (22), which are located on the polymer thread (19) and are visible in X-rays

on the stent body, increase the efficiency of the interventional procedure since

the physician can easily visualize the stent.

The technology of manufacturing of the proposed stent design is a sum of already

developed industrial operations, the sequence of which is described in the Summary

of the Invention. The mentioned technological processes can be executed within the

one assembly unit with high design productivity. The operation of profiling of the

flanged opposite edges on the metallic strip sides is being done by simultaneously

smoothing of the metallic strip outward surface, which is a positive factor for the

improvement in the surface quality and, consequently, in stent functioning. Besides,

there is a possibility of manufacturing the preliminary geometrical contour of rigid elements on the surface of the thin metallic strip, using one of the conventional methods of Photo-Chemical Machining.

In accordance with clinical requirement, the rolling up of the coiled tube from the shaped metallic strip can be done together with simultaneous deployment of one or

several bioabsorbable local drug delivery constructive element in the small hollow bore

of the kinematic link, that will stimulate improvement in drug therapy of the vessel.

The possibility of creating universal equipment is assumed, where any established

stent diameter standard size from 2.0 to 5.5 mm could be manufactured from the same

metallic strip blank. On the contrary, the aggregate equipment can be a specialized one.

Thus, the proposed stent design possesses a set of improved thromboresistant

properties and could be considered more desirable for the wide clinical practice.

The proposed stent design, being a sum of the accumulated scientific and experimental

knowledge, can result in an essential improvement in the coronary interventions due

to its features, including the possibility of local drug delivery for different clinical

purposes. The proposed stent design also makes it possible to satisfy the needs of the great number of patients undergoing coronary stenting due to the possibility of

producing a wide variety of relatively inexpensive medical devices.

The proposed stent design could also be manufactured and used without the introduc¬

tion of the bioabsorbable local drug delivery constructive element. In this case

the stent design preserves all the positive properties of the Optimum Expandable

Stent Mechanical Model (slotted tube, wire), and still exceeds it in a number of other

important technical and clinical characteristics.

Industrial Applicability

The offered desirable expandable stent is a basis for design, production and application of a wide spectrum of cardiovascular samples. The stent is recommended for bulk serial and massive production. A preferred mode of the desirable expandable stent production

is described above. Still, the construction equivalent element can be improved without losing the invention advantages, formulated as follows.

Claims

CLAIMS:

1. Desirable Expandable Stent for insertion a lumen of in a vessel of a living being, comprising:

a) a coiled tube, executed with the possibility to change the geometrical axis form, the coiled tube rolled up from the thin profiled metallic strip in such a way,

that the flanged opposite edges of the said profiled metallic strip form a kinematic link

with a small hollow bore, the shape and geometrical sizes of which are predetermined;

b) rigid elements formed in a shape of honeycomb cells on the said coiled tube outward

surface, whereas upon the expansion of the stent, the transformation of the preliminary

geometrical contour of the said rigid elements into the honeycomb cell on the outward

surface of the said coiled tube is done according to the concept of the uniform force

distribution according to a vessel shape with an even distribution of the applied force

along the perimeter of the said stent, and the said stent radial supporting ability

becomes maximal;

c) a geometrical hollow in a shape of a helical groove is marked in the said kinematic

link from the side of the said coiled tube inner surface and located along the said

geometrical axis;

d) a constructive element of bioabsorbable local drug delivery, loaded with

antithrombotic, antiproliferative or other therapeutic agents in regulated concentration

for sustained local delivery, and accommodated in the small hollow bore of the said

kinematic link.

2. Desirable Expandable Stent, wherein every systole-diastole of the beating heart

the said flanged opposite edges in the said kinematic link's small hollow bore have

the possibility of relative shifting, thus facilitating longitudinal compliance of the said stent body and mechanically influence by the said flanged opposite edges on the said bioabsorbable local drug delivery constructive element, accommodated in the said kinematic link's small hollow bore.

3. Desirable Expandable Stent, wherein, upon the expansion of the said stent, an

exterior part of the kinematic link is executed over the said coiled tube outward surface generating line, thus supporting the local introduction of the said exterior part

of the said kinematic link into the vessel wall.

4. Desirable Expandable Stent, wherein the diameter of the said stent before the

expansion is executed taking into account its dense fitting on the non-inflated balloon

of the transluminal catheter, whereas the width of the rigid element' preliminary

geometrical contour is being established proportionally to the inner surface diameter of

the vessel.

5. Desirable Expandable Stent as claim 1, wherein the said constructive element of bioabsorbable local drug delivery contains marks that are visible in X-rays of the said

stent body.

6. Desirable Expandable Stent, technological process of manufacturing of which includes

the following steps:

- cold plastic stamping of the rigid elements' preliminary geometrical contour on the

outward surface of the thin metallic strip;

- profiling of a shaped cross-section of a flanged opposite edges on the sides of the said

metallic strip with a simultaneous smoothing of metal surpluses on its outward surface

after the cold plastic stamping operation;

- rolling up of a coiled tube from the profiled metallic strip with a simultaneous

accommodation of a bioabsorbable local drug delivery constructive element in a small hollow bore of a formed kinematic link of a said coiled tube;

- fixing of a first face surface of the said coiled tube and a first end of the said bioabsorbable local drug delivery constructive element;

- separation of the ready device;

- fixing of a second end face surface of the said coiled tube and a second end of the said

bioabsorbable local drug delivery constructive element.

7. Desirable Expandable Stent as in claim 6, wherein is executed in an automatic cycle of

the said technological operations.

AMENDED CLAIMS

[received by the International Bureau on 18 November 1998 (18.1 1.98); original claim lb amended; remaining claims unchanged (3 pages)]

1. Desirable Expandable Stent for insertion a lumen of a vessel of a living

being, comprising: a) a coiled tube, executed with the possibility to change in space the geometrical

axis form, the coiled tube rolled up from the thin profiled metallic strip in such a

way that the flanged opposite edges of the said profiled metallic strip sides form a

kinematic link with a small hollow bore , the shape and geometrical sizes of which

are preliminary regulated;

b) plurality of the rigid elements formed in a shape of meshy structure on the said

coiled tube outward surface, each cell of which is locked by the sides contour of

different degree curvature, whereas upon the expansion of the stent, the

transformation of the preliminary geometrical contour of the said rigid elements

into a final geometrical shape on the said coiled tube outward surface is done

according to force scheme of the design uniform development according to a vessel

shape with an even distribution of the applied force along the perimeter of the said

stent, and the said stent radial supporting ability becomes maximal;

c) a geometrical hollow in a shape of a helical groove is marked in the said

kinematic link from the side of the said coiled tube inner surface and located

along the said geometrical axis;

d) a constructive element of bioabsorbable local drug delivery loaded with

antithrombotic or antiproliferative agents in reglamented concentration for

sustained local delivery and accommodated in the said kinematic link small

hollow bore.

2. Desirable Expandable Stent as in claim 1, wherein every sistole-diastole dynamic cycle of the beating heart the said flanged opposite edges in the said kinematic link small hollow bore have the possibility of relative shifting,

facilitating the longitudinal compliance of the said stent body and mechanically influencing by the said flanged opposite edges on the said bioabsorbable local

drug delivery constructive element, accommodated in the said kinematic link

small hollow bore.

3. Desirable Expandable Stent as in claims 1, 2, wherein upon the expansion

of the said stent a exterior part of the kinematic link is executed over the said

coiled tube outward surface generating line thus supporting the local introduction

of the said kinematic link exterior part into the vessel wall.

4. Desirable Expandable Stent as in claims 1, 2, 3, wherein the diameter of the

said stent before expansion is executed taking into account the dense fitting on

the transluminal catheter non-inflated balloon, whereas the width of the rigid

elements preliminary geometrical contour being established proportionally to

the inner surface diameter of the vessel.

5. Desirable Expandable Stent as in claims 1, 2 , 3, 4, wherein the said

constructive element of bioabsorbable local drug delivery is supplied by marks

that are visible in X-rays on the said stent body.

6. Desirable Expandable Stent as in claims 1, 2, 3, 4, 5, ready device of which

is done in an automatic cycle of the following technological operations:

- cold plastic stamping of the rigid elements preliminary geometrical contour

along outward surface of a thin metallic strip;

- profiling of a shaped cross-section of a flanged opposite edges on the sides of the

said metallic strip with a simultaneous smoothing of metal surplusses and hardening on its outward surface after the cold plastic stamping operation;

- rolling up of a coiled tube from the profiled metallic strip with a simultaneous accommodation of a bioabsorbable local drug delivery constructive element in

a small hollow bore of a formed kinematic link of the said coiled tube;

- fixing of a first face surface of the said coiled tube and a first end of the said

bioabsorbable local drug delivery constructive element;

- ready device sections;

- fixing of a second end face surface of the said coiled tube and a second end of

the said bioabsorbable local drug delivery constructive element.