WO2000064372A1

WO2000064372A1 - The double-sheet stent

Info

Publication number: WO2000064372A1
Application number: PCT/IL1999/000221
Authority: WO
Inventors: Valerian Voinov; Romul Boldyrev
Original assignee: Brainwave Cardio-Vascular Technologies Ltd.
Priority date: 1999-04-25
Filing date: 1999-04-25
Publication date: 2000-11-02
Also published as: EP1176927A4; AU3441899A; EP1176927A1; US6471719B1; CA2368252A1; JP2003500086A

Abstract

This invention is the constructive elements, preliminary formed in a shape of the two mainly similar stencils I and II on the surface of the two thin sheet metallic blanks. The said stencils I and II are preliminary superimposed one on another in order to be shifted for a winding outline width along the stent longitudinal axis and to form the alternating winding outlines pairs. One pair of the said winding outlines is executed by a simple superimposing of the stencil I winding outline (12) on the stencil II winding outline (14), whereas the said winding outlines pair, neighboring to it, is performed by the superimposing of the stencil II winding outline (15) on the stencil I winding outline (13). The stencil II winding outlines are passed through the slots between the stencil I winding outlines as to make the formed semicircles be located in turns in the stent expanded shape.

Description

THE DOUBLE-SHEET STENT Field and Background of the Invention The present invention relates generally to medical technology, particularly, to expandable cardiovascular stents which are intended for the radial arterial lumen recovery with subsequent restoring of the normal blood flow. One of the most perspective tendencies in the development of stents is the design with the improved antithrombotic properties so as to lessen the necessity in the systematic anticoagulation therapy and to reduce the bleeding and vascular complications. However, all the now available stents are executed from metal and in each model there is a compromise between the constructive elements of radial strength and flexibility, in order to support safely the deformed walls of the artery and, with the least resistance, to prevent the normal pulsation of the vessel. The variety of stent designs is determined, on the one hand, by the fact that the metal intravascular scaffolding must perform the dilated influence and, on the other hand, protect safely from penetrating in to the blood of the damaged vessel

part products of decay. The stent should not injure the surrounding tissues that could take place during the leading of the stent to the place of the pathological formation in the vessel, should not crumple upon the effect of blood pressure and the muscular influence, should not deform and slide down from the surface of guiding catheter uninflated balloon during carrying out of the clinical procedure. But the most important thing is that the stent should as little as possible distinguish in its characteristics from the properties of the vessel itself, i.e. the stent should not correct to a considerable extent the vessel hemodynamics, limit the vascular tissues pulsation, violate its blood flow, etc. P. Ruygrok and P. Serruys, generalizing the results of the accumulated observations and the necessity of systematic increase in antithrombotic properties, recommend to provide the optimal stent design with the following properties: flexibility, trackability, low profile, visibility, thromboresistance, biocompatability, reliable expandability (see "Calculation". Vol. 94, # 5, Sept. 1, 1996). It could be supposed that the creation of a stent, meeting the above-mentioned requirements, as well as its equipment by a temporary constructive element for local drug delivery, is an efficient means for the reducing a systematic anticoagulation therapy, bleeding and vascular complications after a significant traumatic influence to which the deforming scaffolding of the vessel belongs.

The enumerated requirements to the stent design are common enough and at the same time generally known ones. These requirements cannot be used since they are devoid of criterion evaluations. It is natural that the clinical practice requires the specification of some stent basic properties evaluation, properties that are to a considerable extent suitable for their use by the creators of new designs. A number of some requirements, adopted from the clinical practice and, in particu lar, formulated by Dr. M. Leon (Cardiology Research Foundation, Washington) could be stated as follows:

1. The metal coverage by the stent of the vessel lesion parts should be sufficient. For the vessels with a diameter of 3 ... 4 mm within the limits of 15% ... 25%, reaching 30% in SVG segments with a diameter about 5 mm.

2. The stent must have zones, different in their qualitative properties, along its longitudinal axis. In particular, along the edges the stent struts should be more

rigid, while in the stent middle part the stent struts should be more flexible. 3. It is necessary to ensure the axis perpendicularity and the sufficient rigidity of the stent end face surfaces.

4. The design seems to behave like a closed stent, while having the flexibility of an open stent.

5. In the stent, after expansion, the relatively small distances between the struts, about 1 mm, should be preserved.

6. The stent should operationally preserve invariable the radial sizes. This is connected with the non-admission of stent metal relaxation after expansion (no recoil).

7. It is desirable to have the stent length within the limits of 8 ... 40 mm. The stent length less than 8 mm makes it difficult to ensure its stable location in a vessel, the stent length more than 40 mm makes it difficult to combine it with the complicated anatomical outlines of the vessel. For example, if a long coverage by the stent of the vessel lesion is needed, it will be better to implant several stents of a shorter length in a consecutive order.

8. It is undesirable to change the stent axial sizes upon its final expansion in a vessel.

9. Upon the stent expansion in a vessel the operational pressure of the guiding catheter balloon should not exceed 8 atm.

10. The stents of the considered class have the necessary diameters from 2.5 mm to 5 mm.

11. Upon the designing of stents, a necessity in creating specialized models might appear. For example, V - shaped stent with a special protection of pair vessels carina area, etc. It is supposed that in the near future the number of various stent designs will become unlimited, though the expediency of the problem solution requires the creation of no more than ten different modifications, sufficiently universal and efficient models according to the generalized operational characteristics.

Prior Art The Balloon Expandable Sheet Stent, in which the constructive elements are preliminary formed in a shape of a stencil (1) on the thin sheet metallic blank surface, is known (see the patent request PCT/TL 98/ 00189 from 21.04.1998). The said stencil (Fig. 1, pos. 1) represents two relatively rigid bands (2, 3) whose branches form the periodically repeating winding outlines (4) which in the stent expandable shape take the form of the semicircles, placed one after another oppositively in relation to the relatively rigid bands (2, 3) in an alternative sequence along the stent longitudinal axis.

Such a location of the stent semicircles (5, 7) with a side view on the relatively rigid bands (6) location plane is schematically shown in Fig. 2. The prototype-stent has high functional properties and, in general, corresponds to the requirements demanded from such a kind of designs. The stent constructive elements, circular in the light, allow to register its diameter with precision. Besides, the semicircles arch- -shape possesses a heightened stability that makes it possible to use thin blanks in a stent metal cover that can stand pressures, including extreme ones, from the side of the pulsating vessel, and at the same time the semicircles arch-shape has a good capacity of preservation after the removal of the guiding catheter balloon pressure (no recoil). The relatively rigid bands (2, 3) reliably ensure the stent axial sizes. Besides, such a stent design has a high technological possibilities that are determined by the capacities of creating a volumetric device from the thin sheet metallic blank without applying the known connecting means (welding, soldering, lock connections, etc.). However, the prototype-stent has some essential drawbacks.

- To create a stent tube form the neighboring semicircles are folded into opposite sides, thus making the clearance between the neighboring semicircles (5, 7), but folded into one side, an increased one. For a number of cases this fact limits the use of a stent in the clinical practice. Moreover, the semicircles alternation along the longitudinal axis, shown in Fig. 2, creates on the stent end faces some "steps", excluding the notion about the stent axis end faces perpendicularity.

- The stent design, as well as the majority of the known clinical models, possesses the same monotonous properties along its entire extent. This does not always correspond in its extent to the anatomical properties of a vessel, especially to that with the pathological changes, requiring the correction of the angioplasty. In addition there are some definite differences in the hemodynamics inside the stenting and those sections of the vessel that adjoin it. The consequences of such differences may turn out to be a reason for restenosis. It is obvious, that when designing the stent end faces a special approach should be used.

The attention should be drawn to the fact that the perpendicularity of stent axis end faces is very important for all stents without exception. That is why the whole complex of end face problem is one and the same for all the stents, irrespective of the variety of different designs.

- The area of vessel metal coverage in the prototype-stent does not fully meet the requirements of clinical practice since it makes up less than 13% for the arteries with a diameter of about 3 ... 4 mm.

Summary of the Invention The purpose of the invention is to create a stent with a common circular structure of constructive elements, that allows to get it not as a "alternating semicircles" system, but in a shape of alternating circles, and thus to realize more efficiently the attainment of end faces perpendicularity and the increase in the percentage of metal coverage of a vessel by the stent.

The purpose of the invention is also the conditioned stent functional properties change along its entire extent, such as the attainment of the local increased metal coverage of the vessel wall precisely in places where this is dictated by the intra- vascular diagnostics results, and the improvement of hemodynamics on the stent end faces sections with the help of the preconditioned change in these sections geometry.

Both the first and the second purposes of the invention must be achieved with the

use of the simple thin sheet metallic blanks, chiefly with the monotonous geometrical parameters along the entire extent of the said blanks. The set purposes are achieved by the fact that in the Double-Sheet Stent the constructive elements, preliminary formed in a shape of two mainly similar stencils

I and II, on the two sheet metallic blank surfaces, each of which is represented by the two relatively rigid bands, with branches forming periodically repeating winding outlines of a preconditioned width and which in the stent expanded shape take up the form of semicircles, located one after another and oppositely in relation to the said relatively rigid bands in a consecutive alternation along the stent longitudinal axis, whereas the distance between the neighboring branches is greater than the said width of the said winding outlines.

In the Double-Sheet Stent the said constructive elements stencils I and II are preliminary superimposed one on another in such a way that they turn out to be shifted for a said winding outline width along the stent longitudinal axis and form the alternating parts of the winding outlines, whereas one pair of the said winding outlines is executed by the simple superimposing of stencil I winding outlines on

stencil II winding outlines, while the neighboring pair of the said winding outlines is executed by the superimposing of stencil II winding outline on stencil I winding

outlines, for which purpose the winding outlines of stencil II are passed through the slots between the winding outlines of stencil I, and in the stent expanded shape the formed semicircles are located by turns, one semicircle belongs to stencil I,

while the neighboring semicircle belongs to stencil II, and this sequence of the said semicircles location along the stent longitudinal axis is preserved from the one side as well as from the opposite side of the said doubled relatively rigid bands.

In the Double-Sheet Stent the said constructive elements stencils I and II are preliminary superimposed one on another so as to shift for the said width of the said winding outlines along the stent longitudinal axis and to form the winding outlines alternating parts, whereas each of the said stencil I winding outlines is

passed through the slots between the stencil II winding outlines against the stop

of the said stencil I winding outlines branches into the branches of the stencil II winding outlines, while in the stent expanded shape all formed semicircles of stencil

II are located on one side over the stencil I relatively rigid band, and all formed semicircles of stencil I are located oppositively on the other side over the relatively

rigid band of stencil IL

In the Double-Sheet Stent the said constructive elements stencils I and II, oriented definitely along the winding outlines, are spread one in relation to another for 180°

after which stencil I is superimposed on stencil II, then the said stencil I winding

outlines are passed through the slots between the said stencil II winding outlines against the stop of the said winding outlines branches of stencil I into the said

branches of the said stencil II winding outlines, while in the stent expanded shape

all formed semicircles of stencil II are located on one side over the relatively rigid band of stencil I, and all formed semicircles of stencil I are located oppositively on

the other side over the relatively rigid band of stencil II.

In the Double-Sheet Stent the distance between the said semicircles along the

stent longitudinal axis for the SVG segments with a diameter of about 5 mm is adjusted within the limits of the said values difference, the distance between the neighboring semicircles and the preconditioned winding outlines width, while for the arteries with a diameter of about 3 ... 4 mm, that require a greater distance between the said semicircles, the said distance between the neighboring semicircles is increased.

In the Double-Sheet Stent for the relatively large vessels the constructive elements

of the said stencils I and II, the outlines of the future stent semicircles are executed as rectilinear ones.

In the Double-Sheet Stent one of the said constructive elements stencils is executed in a shape of the fragments of another stencil, taken for a basic one, the total length of the said fragments is less than the length of the said basic stencil, while the said fragments are located in the preconditioned places along the stent longitudinal axis on the said basic stencil.

In the Double-Sheet Stent on the end faces of the said basic stencil the said constructive elements fragments are set up so that in the stent expanded shape the bardering with the end faces winding outlines of the said basic stencil and those of the said fragments each form a closed circle, whereas the perimeters of the said bardering winding outlines, not less than two, are increased in relation to the other winding outlines perimeters that are executed equal. Thus, as result of using two sheet metallic stencils, connected by the proposed way without the use of any known connecting means (lock connections, etc.), it was possible to create a stent design consisting practically of alternating circles. Therefore, in the stent area, falling at a unit of its length, there is a twice greater number of semicircles, comprising circles, i.e. twice as much of a metal area covering the wall of a vessel. Then, if in the prototype-stent the percentage of the said metal area totaled about 13%, in the proposed stent it makes up about 26%, that meets the requirements of the clinical practice. In this case, the stent circular structures automatically ensure the perpendicularity of its axis end faces that also meets the requirements of the clinical practice made to the stents since they improve hemodynamics and lower the risk of restenosis. In the volume of the proposed stent design it is possible to increase locally the area of the vessel wall metal coverage with the help of the constructive elements fragments connected with the stent basic part. For example, if plaques in a vessel are remote one from another along its entire extent, then the said constructive elements fragments are set up in accordance with the location of plaques and in these places the vessel wall is protected safely enough. And in the intervals, where the plaques are absent, i.e. there where the fragments are not set up on the stent basic part, the area of the vessel wall metal coverage is twice as less and, consequently, the vessel wall section, washed by the blood, is twice greater, the fact that to a considerable extent contributes to increasing the viability of the artificial vessel in the indicated place.

In the proposed stent there are sections, where, irrespective of the place of pathological formation location in a vessel, the constructive changes are obligatory. Such places in the stent are the sections adjoining its end faces. Here is the boundary of hemodynamics change upon passing from the artificial part to the natural part of the vessel (or from the natural part to the artificial one). In the proposed stent design, by using the fragments connected with the stent basic part, the measures are taken to lessen the hemodynamics edge effect consequences on the indicated parts of the vessel (boundaries of blood flow change), as a result of which a peculiar infuser is formed at the inlet to an artificial vessel part, while at the outlet from the artificial vessel part a peculiar confusor for the blood flow. The lessening of the hemodynamics edge effects consequences decreases, by the indicated means, the risk of restenosis both on the artificial vessel sections and in the sections adjoining it. In this case, the stent end faces are perpendicular to its axis and preserve this property due to the heightened rigidity.

Brief Description of the Drawings This invention is herein described with the help of examples and references to the accompanying drawings, wherein: Fig. 1 shows the prototype-stent constructive elements stencil, preliminary formed on the thin sheet metallic blank surface.

Fig. 2 shows schematically the consecutive alternation of the semicircles along the prototype-stent longitudinal axis upon the side view on the location plane of the relatively rigid bands.

Fig. 3 shows two similar stent constructive elements stencils I and II, prepared for unification in the Double-Sheet Stent, according to the invention. Fig. 4 shows schematically the beginning of the assembly of the Double-Sheet Stent in which the distance between the relatively rigid bands planes location is conditionally increased. The side view on the plane of relatively rigid bands location.

The broken lines correspond to stencil II of the stent constructive elements.

Fig. 5 shows a fragment of the stent constructive elements stencils I and II assembly, according to the invention. This is a view along the arrow A in Fig. 4, sections B and C in Fig. 3, superimposed one on another by the preconditioned way. "a" - distance between the winding outlines branches; "b" - width of the winding outline.

Fig. 6 shows schematically the stent semicircles location, according to the invention, upon a side view on the relatively rigid bands location plane. Variant by Fig. 5. The broken lines correspond to the constructive elements

stencil II.

Fig. 7 shows a fragment of the stent constructive elements stencil I and II assembly, according to the invention. This is a view along the arrow A in Fig. 4, sections B and C in Fig. 3, superimposed one on another by a preconditioned way. Fig. 8 shows schematically the stent semicircles location, according to the invention upon the side view on the relatively rigid bands plane location. Variant by Fig. 7.

The broken lines correspond to the stent constructive elements stencil II. Fig. 9 shows the basic stencil and fragments of the stent constructive elements, according to the invention, prepared for unification in the Double-Sheet Stent. Fig. 10 shows schematically a fragment of the Double-Sheet Stent after expansion, according to the invention.

Fig. 11 shows schematically the stent overall diameter reduction on the mandrel to the sizes necessary for the location on the guiding catheter uninflated balloon.

Specific Description

Fig. 3 shows two similar stent constructive elements stencils I and II, formed on the two thin sheet metallic blanks surface. To obtain the Double-Sheet Stent the

stencil I constructive elements are superimposed on the stencil II constructive elements, matching the winding outlines (8, 9) with winding outlines (10, 11). It is illustrated as an example of matching the outlines. The other stencils I

and II winding outlines are located by the same way (the stencils I and II matching

operation itself is not shown in Fig. 3). Then stencil I is shifted along stencil II longitudinal axis to the right for the winding outline width by Fig. 3. Fig. 4 shows schematically the shifting to the right of stencil I in relation to

stencil II. The stencil I winding outlines (12, 13) corresponding to positions (8, 9)

by Fig. 3 and the stencil II winding outlines (14, 15) corresponding to positions (10,

11) by Fig. 3 interact, thus uniting the stencil I and stencil II constructive elements into the Double-Sheet Stent configuration. The winding outlines (12) and (14) are simply superimposed one on another (with the above-mentioned shifting), while the winding outline (15), belonging to stencil II, is passed through the slot between stencil I winding outlines. As a result, in the first described pair the stencil I wind¬

ing outline, i.e. (12), is superimposed on the stencil II winding outline, i.e. (14),

and in the second described pair the stencil II winding outline, i.e. (15), is superimposed on the stencil I winding outline, i.e. (13). All the other winding outlines are interacting by the same way. If to look from above along the arrow A, then the

stencils I and II visible winding outlines follow one another, alternate (pos. 12, 15, etc.). At the same time, if to let the gauge pass through the winding outlines lying above (pos. 12, 15, etc.) and start folding them into one side, upwards, while all the other winding outlines fold downwards, thus increasing simultaneously the diameter of the gauges, then a stent from the constructive elements stencils I

and II is formed.

Fig. 5 shows the fragments of stencils I and II winding outlines in a situation, corresponding to that described by Fig. 4. Here, only the winding outlines initial parts, with the connection on the two relatively rigid bands, are depicted, the fact

that corresponds to the fragment B of stencil I and the fragment C of stencil II by Fig. 3. Positions (16, 17) by Fig. 5, belonging to the stencil I winding outlines, correspond to positions (12, 13) by Fig. 4, belonging to the same stencil I winding

outlines. Positions (18, 19) by Fig. 5, belonging to the stencil II winding outlines,

correspond to positions (14, 15) by Fig. 4, belonging to the same stencil II winding outlines.

In Fig. 5 the situation, described by Fig. 4, is better illustrated. Here, it is seen

the alternation of stencils I and II winding outlines, i.e. positions (16, 19, etc.). In Fig. 5 the indicated winding outlines are turned to the observer of this Figure, while the winding outlines (18, 17) are located under them. The winding outline (16) is simply superimposed on the winding outline (18), and the winding outline (17), passing through the slot between stencil II winding outlines, turned out to be under the winding outline (19). Then, if the winding outlines (16, 19) are to be folded towards the observer of Fig. 5, and the winding outlines (18, 17) towards the opposite side, the indicated winding outlines will form practically two circles after the calibration.The winding outlines (16, 18) form one circle, while the winding outlines outlines (17, 19) - another one. In this case, the semicircles, obtained from the winding outlines (16, 19), are directed towards one side, i.e. to that of the observer of Fig. 5, while the semicircles, from the winding outlines (18, 17), are directed towards the opposite side, i.e. from the observer of Fig. 5. Fig. 6 shows schematically the stent semicircles location after expansion upon a side view on the relatively rigid bands location plane. By positions (21, 22) are

depicted the upper neighboring semicircles of stencils I and II that correspond to positions (16, 19) of the winding outlines by Fig. 5. By positions (23, 24) are

depicted the lower neighboring semicircles of stencils I and II that correspond to positions (18, 17) of the winding outlines by Fig. 5. Fig. 6 shows conditionally that semicircle (24) passed through semicircle (22). This was done in accordance with the previously described explanation by Fig. 5 of the fact that the stencil I winding

outline (17) passes into the slot between the stencil II winding outlines, locating

under the stencil II winding outline (19) and forming, upon the stent expansion, the lower semicircle (pos. 24 by Fig. 6). The depicted operation is repeated along the stent entire axial length. Fig. 6 shows a variant of the Double-Sheet Stent when the semicircles actually form the closed circles. It is seen, as a result, that the stent end faces surfaces do not have steps and turn out to be perpendicular to the stent longitudinal axis, while vessel wall metal coverage increases twice as much in comparison with the prototype-stent (see Fig. 2).

Fig. 7 shows the same as Fig. 5, only with the different relative location of the

stencils I and II winding outlines. Positions (25, 26, 27) by Fig. 7, belonging to the stencil I winding outlines, correspond to positions (16, 17, 20) by Fig. 5, belonging to the same stencil I winding outlines. Positions (28, 29) by Fig. 7, belonging to the

stencil II winding outlines, correspond to positions (18, 19) by Fig. 5, belonging to

the same stencil II winding outlines. The different location of stencils in Fig. 7 is

determined by the shifting of stencil II in relation to stencil I by Fig. 5 to the left for a value of (a - b), where "a" - is a distance between the winding outline branches; "b" - is a winding outline width. The sizes "a" and "b" are shown in

Fig. 5 since there it is easier to present the stencils I and II shifting, leading to the constructive elements location, illustrated in Fig. 7. In this case, the uniting of

stencils I and II constructive elements, described in connection with Fig. 5, leads to the forming by winding outlines (26, 28), corresponding to positions (17, 18) by Fig. 5 of two lower semicircles upon the stent expansion. The winding outlines (27, 29), corresponding to positions (20, 19) by Fig. 5, form two upper semicircles upon the stent expansion. As a result, the stent would consist of as though alternating double semicircles.

Fig. 8 shows schematically the stent semicircles location upon a side view on relatively rigid bands location plane. By positions (30, 31) the lower neighboring

semicircles are designated, representing as though one lower double semicircle of the stent. Positions (30, 31) of the semicircles correspond to positions (26, 28) of the winding outlines by Fig. 7. By positions (32, 33) are designated the upper neighboring semicircles, representing as though one upper stent double semicircles. Positions (32, 33) of the semicircles correspond to positions (27, 29) of the winding outlines by Fig. 7.

From Fig. 8 it follows that the stent consists of double semicircles, i.e. the closing of the semicircles into closed circles as in the prototype-stent, however, the quantity of metal and, consequently, the vessel wall metal coverage is preserved twice as much. It should be noted that to achieve such an effect in the prototype- -stent by a technologically simple increase in the winding outline width is rather difficult. The transition from the stent configuration by Fig. 6 to the stent configuration by Fig. 8 is determined by the necessity to obtain, in some cases, the increased clearances between the semicircles (let it be double ones). Upon the necessity the clearance between the semicircles for the stents both by Fig. 6 and by Fig. 8 could also be conditionally widened at the expense of increasing the distance "a" between the branches (see Fig. 5). In this case, the width of slots between the stencils winding outlines increases correspondingly. Fig. 9 shows the basic stencil (34) and fragments (35, 36, 37) of the stent constructive elements, prepared for unification in the Double-Sheet Stent. Here, apart from the end faces, practically obligatory fragments (35, 36), the number and the axial sizes of the intermediary fragments (37) can be different depending on the clinical practice requirements. This emphasizes once more the individuality of the Double- -Sheet Stent design, though the stent is formed from the relatively simple (monoton ous) components. Irrespective from the quantity and peculiarities of uniting the intermediary fragments (37) with the constructive elements basic stencil (34), the edge fragments (35, 36) must always be taken into account for strengthening the stent end faces and ensuring the end faces perpendicularity to its axis. Therefore, the fragments (35, 36) are united with the constructive elements basic stencil (34) according to the schemes, corresponding to Figs. 5, 6. The number of winding outlines in each of the fragments (35, 36) should not be less than two, while, practically, given the sufficient stent axial length, the number of the winding outlines in each of the fragments (35, 36) could be increased to seven. Taking into account the importance of calculating the hemodynamics peculiarities in the stent end faces area, it is desirable to form something like a "bell-mouthed" effect at the inlet and outlet of the blood flow. For this purpose on fragments (35, 36), as well as along the basic stencil constructive element sections, corresponding to the length of these fragments, the stent circles diameters are increased gradually up to the very end face. It is obvious, that the most reasonable is the maximum increase of the diameter, i.e. at the very end face for 2 ... 4 widths of the circle wall. As is seen, the very insignificant increase in the diameter at the stent end faces is regulated. However, in this case the end faces, widening for the indicated value by the free end part of the guiding catheter balloon, install the end faces circles walls flash with the wall of a partially crashed through vessel. This ensures the creation of the peculiar infusor and confusor respectively at the stent inlet and outlet which

improve the hemodynamics in the transitional regions of the "vessel-stent" system and in this way decrease the risk of restenosis. The recommended increase in the semicircles diameters at stent end faces is achieved by the increase in the corresponding winding outlines perimeters. Fig. 10 shows a fragment of the stent exterior , according to the invention, widened in accordance with Fig. 6, where the semicircles actually form the closed circles. Fig. 11 shows schematically the stent overall diameter reduction on the mandrel to the sizes necessary for the location on the guiding catheter uninflated balloon and implantation in a vessel.

The reduction is done with the help of rollers (40, 41) and a tension reel (42) with an elastic ribbon (43), the width of which corresponds to the regulated stent length. The rigidity of the elastic ribbon (43) should be less than the rigidity of the stent material. For example, the nylon ribbon could be used. The elastic ribbon (43) densely envelops the stent (38) on the mandrel (39), pressing it partially to the rollers (40, 41). The tension reel (42) effort should be sufficient for stent volume reduction, but not too great, as not to damage the ribbon (43) and the stent (38) at the place of their compression to the rollers (40, 41). Upon the rollers (40, 41) rotation the secure stent volume reduction up to the minimum sizes is performed, the sizes that depend on the rigid metallic mandrel (39) diameter. Thus, as follows from the description and the presented Figures, the proposed stent design is formed by a circular structure, i.e. the stent consists of a row of closed circles connected with each other. The presence of the closed circles on the stent end faces make it possible to speak about the ensuring of end faces perpendi- clarity to its axis. It is shown that the metal coverage of the vessel wall, as compared with the prototype-stent, increases two times more, i.e. actually grows from 13 to 26%. In this case, a lumen between the stent circles could be established beforehand in accordance with the clinical practice requirements. Due to the use of constructive elements fragments, connected with the basic stencil, the stent functional possibilities are widened. In the proposed design the local metal coverage of the vessel wall is possible only in the places preliminary determined by the intravascular diagnostics. As a consequence of this, the relatively healthy vessel wall sections are more intensively washed by the blood, thus contributing to the increase in their viability. The fragments, set up on the stent end faces, increase their rigidity, while a special proposal on the stent circles geometry ensures the obtaining of "bell-mouthed" effect at the stent edge sections, thus contributing to the hemodynamics improvement and, as a consequence, decreasing the risk of restenosis.

The technology of the proposed stent design is preserved at the level of the prototype-stent with a certain increase in the assembly operations cycle. A possibility of the confident obtaining of the stent minimal diameter, necessary for its normal guidance and implantation in the vessel, is shown with a help of a relatively simple device.

Claims

What is claimed is: 1. The Double-Sheet Stent for insertion in a lumen of a vessel of living being, comprising:

- constructive elements, preliminary formed in a shape of the two mainly similar stencils I and II on the surfaces of the two thin sheet metallic blanks, each of which is represented by the the two relatively rigid bands, the branches of which form a periodically repeating winding outlines of a preconditioned width and which in a stent expanded shape take the form of semicircles, located one after the other oppositively in relation to the said relatively rigid bands in a consecutive alternation along the stent longitudinal axis, whereas the distance between the neighboring branches is greater than the said winding outlines width;

- the said constructive elements stencils I and II are preliminary superimposed one on another so as to be shifted for a said winding outline width along the stent longitudinal axis and form the alternating winding outlines pairs, whereas one pair of the said winding outlines is executed by the simple superimposing of stencil I

winding outline on stencil II winding outline, while the neighboring pair of the

said winding outlines is executed by the superimposing of stencil II winding outline on the winding outline of stencil I, for which purpose the winding outlines of

stencil II are passed through the slots between winding outlines of stencil I, and in the stent expanded shape the formed semicircles are located by turns, one

semicircle belongs to stencil I, while the neighboring semicircle belongs to stencil II, and this sequence of the said semicircles location along the stent longitudinal axis is preserved both from the one side, as well as from the opposite side of the said

doubled relatively rigid bands; - the said constructive elements stencils I and II are preliminary superimposed one on another so as to shift for a said width of the said winding outlines along the stent longitudinal axis and to form the winding outlines alternating parts, whereas each of the said winding outlines of stencil I is passed through the slots between the said winding outlines of stencil II against the stop of the said winding outlines

branches of stencil I into the branches of the said winding outlines of stencil II, while in the stent expanded shape all the formed semicircles of stencil II are located on one side over the the relatively rigid band of stencil I, and all formed semicircles of stencil I are located oppositively on the other side over the relatively rigid band

of stencil II;

- the said constructive elements stencil I and II, definitely oriented along winding outlines and are spread one in relation to another for 180°, then stencil I is super¬

imposed on stencil π, then pass the said stencil I winding outlines into the slots

between the said stencil II winding outlines against the stop of the said winding outlines branches of stencil I into the branches of the said winding outlines

of stencil II, while in the stent expanded shape all formed semicircles of stencil II are located on one side over the relatively rigid band of stencil I, and all formed semicircles of stencil I are located oppositively on the other side over the relatively

rigid band of stencil II;

- for the SVG segments with a diameter of about 5 mm the distance between the said semicircles along the stent longitudinal axis is adjusted within the limits of the said values difference, the distance between the neighboring semicircles and preconditioned winding outlines width, while for the arteries with a diameter of about 3 .. 4 mm, that require a greater distance between the said semicircles, the said distance between the neighboring semicircles is increased;

- for the relatively large vessels in the said stencil I and II the constructive elements, the winding outlines of the stent future semicircles, are executed as rectilinear ones.

2. The Double-Sheet Stent as in claim 1, in which one of the said constructive elements stencils is executed in a shape of the fragments of another stencil, taken for a basic one, the said fragments total length is less than that of the said basic stencil, and the said fragments are located in the preconditioned places on the said basic stencil along its longitudinal axis.

3. The Double-Sheet stent as in claims 1, 2, in which the said constructive elements fragments are set up on the said basic stencil end faces in such a way that in the stent expanded shape the said basic stencil winding outlines, the ones bardering with the end faces, each form a closed circle, whereas the perimeters of the said bardering winding outlines, not less than two, are increased in relation to the other winding outlines perimeters that are executed equal.

AMENDED CLAIMS

[received by the International Bureau on 14 December 1999 (14 12 99) original claims 1 - 3 replaced by new claims 1 - 17 (6 pages)]

W hat is claimed is: 1. The Double-Sheet Stent for insertion in a lumen of a vessel of living being, comprising:

- constructive elements, preliminary formed in a shape of the two mainly similar stencils 1 and n on the surfaces of the two thin sheet metallic blanks, each of which is represented by the the tw o relative!) rigid bands, the branches of which form a periodically repeating winding outlines of a preconditioned width and which in a stent expanded shape take the form of semicircles, located one after the other oppositively in relation to the said relatively rigid bands in a consecutive alternation along the stent longitudinal axis, whereas the distance between the neighboring branches is greater than the said winding outlines width;

- the said constructive elements stencils 1 and II are preliminary superimposed one on another so as to be shifted for a said winding outline width along the stent longitudinal axis and form the alternating winding outlines pairs, whereas one pair of the said w inding outlines is executed by the simple superimposing of stencil I w inding outline on stencil H w inding outline, while the neighboring pair of the said winding outlines is executed by the superimposin^g of stencil n w lndmg outline on the w inding outline of stencil 1. for v» Inch purpose the \\ Hiding outlines o! stencil π are passed tnrough the slots betw een w inding outlines of stencil 1. and in the stem expanded shape the formed semicircles are located

turns, one semicircle belongs to stencil 1. ile the neighboring semicircle belongs to stencil

Ii. and this sequence of the said semicircles location along the stent longitudinal axis is

ed both from the one side, a w ell a f roβi the opposite side of the said doubled

rigid bands. - the said constructive elements stencils I and II are preliminary superimposed one

on another so as to shift for a said width of the said winding outlines along the stent longitudinal axis and to form the winding outlines alternating parts, whereas each of the said winding outlines of stencil I is passed through the slots between the

said winding outlines of stencil II against the stop of the said winding outlines

branches of stencil I into the branches of the said winding outlines of stencil II,

while in the stent expanded shape all the formed semicircles of stencil TJ are located on one side over the the relatively rigid band of stencil I, and all formed

semicircles of stencil I are located oppositively on the other side over the relatively

rigid band of stencil II;

imposed on stencil II, then pass the said stencil I winding outlines into the slots

of stencil II, while in the stent expanded shape all formed semicircles of stencil II are located on one side over the relatively rigid band of stencil I, and all formed

rigid band of stencil II;

- for the SVG segments with a diameter of about 5 mm the distance between the

said semicircles along the stent longitudinal axis is adjusted within the limits of

the said values difference, the distance between the neighboring semicircles and

preconditioned winding outlines width, while for the arteries with a diameter of about 3 .. 4 mm, that require a greater distance between the said semicircles, the said distance between the neighboring semicircles is increased;

- for the relatively large vessels in the said stencil I and π the constructive elements, the winding outlines of the stent future semicircles, are executed as rectilinear ones.

2. The Double-Sheet Stent as in claim 1, in which one of the said constructive

elements stencils is executed in a shape of the fragments of another stencil, taken for a basic one, the said fragments total length is less than that of the said basic stencil, and the said fragments are located in the preconditioned places on the said

basic stencil along its longitudinal axis.

3. The Double-Sheet Stent as in claims 1, 2, in which the said constructive elements

fragments are set up on the said basic stencil end faces in such a way that in the stent expanded shape the said basic stencil winding outlines, the ones bordering with the end faces, each form a closed circle, whereas the perimeters of the said bordering winding outlines, not less than two, are increased in relation to the other

winding outlines perimeters that are executed equal.

4. The Double-Sheet Stent as in claims 1, 2, 3, in which the volumetric structures

are formed from the said stencils I and II in a shape of alternating semicircles with

a possibility of their axial alignment, where one of the volumetric structure is

introduced into another volumetric structure, while upon the radial expansion of

the said united semicircles the single stent alternating circles are formed.

5. The Double-Sheet Stent as in claims 1, 2, 3, 4, in which the said stencils I and II

are connected into one surface along the common longitudinal axis of the thin sheet blank by a relatively rigid band in such a way that the said stencil I winding outlines are the continuation of the said stencil π winding outlines with a shift of the said winding outlines one in relation to the other along the said relatively rigid band for a width of a winding outline, whereas the winding outlines of the said

thin sheet blank edges are connected along the said common longitudinal axis by two relatively rigid bands, thus forming a double sheet stencil, the said double sheet stencil is bended along the fold line of the said thin sheet blank common

longitudinal axis, the said stencil II winding outlines are passed through the said stencil I winding outlines slots each time over one winding outline, while upon the radial expansion of the united double sheet stencil the single stent alternating

circles are formed.

6. The Double-Sheet Stent as in claims 1, 2, 3, 4, 5, in the said double sheet stencil of which the cross-section of the said relatively rigid bands is executed of another

value, in particular, of a lesser one, in comparison with the cross-section of the

said winding outlines.

7. The Double-Sheet Stent as in claims 1, 2, 3, 4, 5, 6, in which the said stencils I

and II contain a great number of V - shaped winding outlines the angles of which are turned to one side.

8. The Double-Sheet Stent as in claims 1, 2, 3. 4. 5, 6, in which the said stencils 1

and II contain a great number of Z - shaped winding outlines with both angles turned to the opposite sides.

9. The Double-Sheet Stent as in claims 1, 2, 3, 4. 5, 6, 7, 8, in which the said stencils

I and II contain a great number of the said winding outlines and make up a form

that includes more than two angles directed by turns into the opposite sides.

10. The Double-Sheet Stent as in claims 1, 3, 6. 7. 8, 9, in which the said stencils 1 and II are connected into one surface along the common longitudinal axis of the thin sheet blank symmetry by one relatively rigid band in such a way that the

stencil I winding outlines are the continuation of the stencil II winding outlines, but the winding outlines of the said thin sheet blank edges are connected along the said longitudinal axis by the two relatively rigid bands, thus forming a double sheet stencil, the said double sheet stencil is folded, joining the said last relatively

rigid bands and forming an unsplitted joint, whereas in a stent expanded shape all

the stencil I formed semicircles are located on one side from the location surface of

the relatively rigid bands and all the stencil II formed semicircles are located

oppositively on the other side from the location surface of the said relatively rigid

bands.

11. The Double-Sheet Stent as in claims 1, 5, 6, 7, 8, 9, 10, in which the winding

outlines of the said stencils I and II are connected directly between themselves in

the said double sheet stencil.

12. The Double-Sheet Stent as in claims 1, 6, 7, 8, 9, 10, 11, in which the longitudinal axes of the two doubled winding outlines form the "V" pattern of

the future V - shaped stent corresponding two longitudinal axes.

13. The Double-Sheet Stent as in claims 1, 6, 7, 8, 9, 10, I I , in which the longitudinal axes of the three doubled winding outlines form the "Y" pattern of

the future Y - shaped stent corresponding three longitudinal axes.

14. The Double-Sheet Stent as in claims 1, 6, 7, 8, 9, 10, I I , "> which the said double sheet stencil is executed directly on the tubular blank with the wall width

equal to that of the said thin sheet blank.

15. The Double Sheet Stent as in claims 1, 2, 3, 4, 5, 6, 8, 9, l <», 1 1, 12, 13, 14, in which the said winding outline, and in particular, for the stents with the diameter expansion of 3.0 mm more, is executed symmetrically in relation to a line

connecting the fastening places of the said winding outlines, by the shortest possible way, with the said relatively rigid bands, whereas upon the expansion of the future stent this line will be a symmetry line of the forming semicircle.

16. The Double-Sheet Stent as in claims 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15,

in which the stent blank width is calculated in such a way that upon the said stent

expansion by the balloon pressure of 6 atm. the nominal diameter of the expanded

stent is obtained, whereas every winding outline, forming a semicircle, is executed

with a possibility of preserving the outline curvature, determined by the size of the angle between the said outline constructive elements not less than 135° .

17. The Double Sheet Stent as in claims 1, 2, 3, 4, 5, 6, 7, 8, 9 ,10, 11, 12, 13, 14, 15, 16, in which the possibility of increasing the nominal diameter of the already

expanded stent in the limits up to 14% is ensured, for which the pressure in the said balloon is raised from 6 atm. up to 14 atm.