DE102022113422A1 - Stent and treatment system with such a stent - Google Patents

Abstract

The invention relates to a stent with a compressible and expandable lattice structure (10) made of webs (11), which are connected to one another in one piece by web connectors (14) and delimit diamond-shaped cells (12), each cell (12) being defined by two straight webs (11a ) and two S-shaped curved webs (11b), which connect the straight webs (11a) to one another, and wherein - the lattice structure (10) in a resting state has a fully expanded resting diameter Dexp, which is between 3.0 mm and 5 .0 mm, - a ratio between a fully compressed diameter Dkomp of the lattice structure (10) and the rest diameter Dexp of the lattice structure (10) is between 1:7 and 1:12, - the webs (11) have a web height that is measured in the radial direction will have, which is at least 0.05 mm and at most 0.09 mm, so that the lattice structure (10) has a radial force of at least 0.5 N between the fully compressed diameter Dkomp and an insert diameter which is at most 90% of the rest diameter Dexp , in particular at least 0.6 N.

Description

The invention relates to a stent and a treatment system.

The treatment of atherosclerotic intracranial arterial stenosis (ICAS) usually involves two treatment steps. In a first treatment step, the stenosis is expanded using a balloon catheter and in a second treatment step, a stent is placed in the area of the stenosis. This treatment method is extremely complex, especially since it requires the use of a balloon catheter and a delivery catheter for the stent. This requires a long operation time with increased risks for the patient.

A particular difficulty lies in treating stenoses that have formed in small vessels, particularly in the neurovascular area. This requires stents that have a very small delivery profile in order to be able to be guided through the small blood vessels to the treatment site. Such stents must therefore be able to be compressed to a very small cross-sectional diameter. However, in practice, stents that can be compressed to such a small cross-sectional diameter have a lower radial force, meaning that they have not yet been able to be used to treat stenoses. Rather, such stents are known, but are used for the treatment of aneurysms.

The object of the invention is to provide a stent that is improved based on the known prior art and which enables particularly good treatment of stenoses, especially in very small blood vessels. In particular, the stent should exhibit a high radial force with a small compressed cross-sectional diameter. A further object of the invention is to provide a treatment system with such a stent.

• - die Gitterstruktur in einem Ruhezustand einen vollständig expandierten Ruhedurchmesser aufweist, der zwischen 3,0 mm und 5,0 mm beträgt,
• - ein Verhältnis zwischen einem vollständig komprimierten Durchmesser der Gitterstruktur und dem Ruhedurchmesser der Gitterstruktur zwischen 1:7 und 1:12 beträgt,
• - die Stege eine Steghöhe, die in radialer Richtung gemessen wird, aufweisen, die wenigstens 0,05 mm und höchstens 0,09 mm beträgt, so dass die Gitterstruktur zwischen dem vollständig komprimierten Durchmesser und einem Einsatzdurchmesser, der höchstens 90% des Ruhedurchmessers beträgt, eine Radialkraft von wenigstens 0,5 N, insbesondere wenigstens 0,6 N, aufweist.

The invention is based on the idea of specifying a stent with a compressible and expandable lattice structure made of webs, which are connected to one another in one piece by web connectors and delimit diamond-shaped cells, each cell being formed by two straight webs and two S-shaped webs which are curved in an S shape and which define the straight ones Connect webs to each other, is limited, and where

• - the lattice structure in a resting state has a fully expanded resting diameter of between 3.0 mm and 5.0 mm,
• - a ratio between a fully compressed diameter of the lattice structure and the rest diameter of the lattice structure is between 1:7 and 1:12,
• - the webs have a web height, measured in the radial direction, which is at least 0.05 mm and at most 0.09 mm, so that the lattice structure is between the fully compressed diameter and an insert diameter which is at most 90% of the rest diameter, has a radial force of at least 0.5 N, in particular at least 0.6 N.

The invention provides a stent that can be easily inserted into small blood vessels because of the large ratio between the fully compressed diameter and the resting diameter of the lattice structure and at the same time, because of its increased web height, applies sufficient radial force to sustainably treat stenosis. In this context, it should be noted that the stent is dimensioned such that the lattice structure in a fully expanded state has a rest diameter that is between 3.0 mm and 5.0 mm. The rest diameter corresponds to the diameter of the lattice structure in the fully expanded state without external force influences.

In general, the lattice structure can be expanded from a compressed diameter to an expanded diameter and vice versa. In this context, the compressed diameter is the diameter at which the lattice structure has its smallest cross-sectional diameter. The lattice structure is preferably self-expandable.

In a preferred embodiment, the straight webs have a first web width and the S-shaped curved webs have a second web width, the first web width being at least 25% and at most 33% larger than the second web width. The different web width offers a particularly high flexibility of the lattice structure, which makes the lattice structure predestined to be inserted into small, especially very tortuous, blood vessels. Such blood vessels are particularly present in the area of the cerebral vessels. In this respect, the invention is particularly suitable for the treatment of stenosis in the intracerebral area.

The web connectors of a cell, which are aligned one after the other in the longitudinal direction of the lattice structure, can have a distance in the idle state that defines a cell length, the cell length being between 2.0 mm and 3.6 mm. The limited cell length of the cells of the lattice structure has a positive effect on so-called foreshortening. Foreshortening is the process in which the lattice structure changes axially shortened due to their radial expansion. This shortening makes it more difficult to position the lattice structure in the blood vessel and should therefore be as small as possible. This is achieved with the cell lengths specified here.

It is possible for the web connectors of a cell, which are aligned one after the other in the circumferential direction of the lattice structure, to have a distance in the idle state that defines a cell height, the cell height being between 1.5 mm and 2.7 mm. It has been shown that such a cell height offers a good compromise between a grid structure that is as flexible as possible and good coverage of the vessel surface covered by the grid structure. Good coverage is particularly beneficial in terms of radial force and the associated treatment of stenosis. At the same time, the lattice structure should remain flexible in its compressed state in order to be able to navigate easily through blood vessels. The cell heights described here make a significant contribution to enabling this dual function.

In connection with the cell length described here, the cell height is of particular importance. Depending on the respective resting diameter of the lattice structure, the ratio between cell length and cell height contributes to improved handling of the stent. In particular, the foreshortening on the one hand and the radial force on the other hand as well as the flexibility of the grid structure during feeding are positively influenced by a predetermined ratio between cell height and cell length. In this respect, it is preferred if the ratio between the cell length and the cell height is between 1.3 and 1.41.

The treatment of intracerebral stenoses is simplified in particular by combining the prescribed stent with a catheter as part of a treatment system, which is described below. The treatment system according to the invention makes it possible to expand the stenosis using a balloon catheter and to deliver the stent to subsequently support the stenosis using a single catheter. This saves additional treatment steps. This leads to a reduction in operating time and a lower risk for the patient.

Specifically, a secondary aspect of the invention relates to a treatment system for the medical treatment of intracranial stenoses with a previously described stent and with a catheter for feeding the stent into a hollow body organ, the catheter having at least two working channels and a balloon which is arranged in the distal region of the working channels , wherein a first working channel is fluidly connected to the balloon and a second working channel extends through the balloon, the second working channel being a through-channel with an inner diameter of at most 0.44 mm.

The second working channel with an inner diameter of at most 0.44 mm (0.17 inches or 2.0 French), in particular at most 0.42 mm (0.165 inches or 1.9 French), enables the delivery of small stents, such as they are described in the present application. This makes the catheter particularly suitable for treating stenoses in intracerebral vessels. The combination with the stent described here is particularly advantageous because the stent, despite its small size, offers a relatively high radial force, which is a prerequisite for the suitability of the stent for the treatment of stenoses.

A particular innovation of the treatment system is that the second working channel of the catheter has a wall that is made up of four layers, at least in sections. A first, innermost layer preferably has polytetrafluoroethylene (PTFE). The first, innermost layer is preferred and covered by a second layer made of a stabilizing braid. The stabilizing mesh can be formed by a network structure made of a superelastic material, for example a nickel-titanium alloy, or made of stainless steel. The second layer can further be surrounded by a third layer made of a polyimide (PI). Finally, a fourth, outermost layer can also be provided, which is formed from a polyether block amide (PEBA) and surrounds the third layer. In particular, the innermost layer made of polytetrafluoroethylene has particularly friction-reducing properties, making it easier to feed the stent, which offers increased radial force. The second layer made of a stabilizing braid supports the catheter and in particular prevents the catheter from ovalizing. At the same time, the second layer provides support in the axial direction so that the catheter can be advanced easily.

• 1 eine abgewickelte Ansicht einer Gitterstruktur des erfindungsgemäßen Stents nach einem bevorzugten Ausführungsbeispiel;
• 2 eine Querschnittsansicht des Stents gemäß 1 in vollständig komprimiertem Zustand;
• 3 eine Querschnittsansicht des Stents gemäß 1 in einem vollständig expandierten Zustand;
• 4 eine Draufsicht auf einen Ausschnitt der abgewickelten Gitterstruktur gemäß 1, wobei Dimensionen der Stege und Zellen dargestellt sind;
• 5 eine Längsschnittansicht durch einen Katheter des erfindungsgemäßen Behandlungssystems nach einem bevorzugten Ausführungsbeispiel; und
• 6 eine Querschnittsansicht durch den ersten Arbeitskanal des Katheters gemäß 5.

The invention is explained in more detail below using an exemplary embodiment with reference to the attached schematic drawings. Show in it

• 1 a developed view of a lattice structure of the stent according to the invention according to a preferred embodiment;
• 2 a cross-sectional view of the stent according to 1 in fully compressed state;
• 3 a cross-sectional view of the stent according to 1 in a fully expanded state;
• 4 a top view of a section of the unrolled lattice structure 1 , where dimensions of the bars and cells are shown;
• 5 a longitudinal sectional view through a catheter of the treatment system according to the invention according to a preferred embodiment; and
• 6 a cross-sectional view through the first working channel of the catheter 5 .

The stent according to the invention has a lattice structure 10 which is formed from several webs 11. The webs 11 are connected to one another in one piece by web connectors 14. Specifically, the lattice structure 10 can be cut from a tube.

1 shows the lattice structure 10 in the unfolded state, with the lattice structure 10 being cut open and spread out along its long side. The webs 11, which delimit the cells 12, are, like the cells 12, in a resting state, i.e. unaffected by external forces. This state is also known as a fully expanded state.

As in 1 can also be seen, the shape of the cells 12, which essentially have a diamond-shaped basic shape, deviates in the edge regions of the grid structure 10. Specifically, at the axial ends of the lattice structure 10 end cells 13 are provided, which have a slightly different geometry than the cells 12. Every second end cell 13 also carries an X-ray marker 30. The X-ray marker 30 can have an X-ray visible material, for example platinum, in particular platinum-iridium, or gold. The X-ray marker 30 is preferably designed as a sleeve which is crimped onto a web extension of the end cell 13.

The lattice structure 10 is preferably formed from a self-expanding material. Such a self-expanding or superelastic material is, for example, a shape memory material. A nickel-titanium alloy is preferably used for this.

The geometry of the stent according to the invention combines two essential advantages. On the one hand, the stent according to the invention provides a good radial force, which is particularly sufficient to treat stenoses in blood vessels. At the same time, the lattice structure 10 is so flexible that it can be expanded from a very small compressed diameter to a comparatively large, preferably 12 times larger, expanded rest diameter.

The ratio between the compressed diameter D _comp and the expanded rest diameter D _exp is in the 2 and 3 good to see. 2 shows the lattice structure 10 in a fully compressed state, the lattice structure 10 having the compressed diameter D _comp . 3 shows, however, the fully expanded state of the lattice structure 10, with no external forces acting on the lattice structure 10. The fully expanded state corresponds to a resting state. The lattice structure 10 has a rest diameter D _exp . The ratio between the fully compressed diameter D _comp and the rest diameter D _exp is preferably between 1:7 and 1:12. It is envisaged that the lattice structure has a rest diameter D _exp which is between 3.0 mm and 5.0 mm.

A distinction must be made between the resting diameter (nominal diameter) and the insert diameter of the lattice structure 10. The geometry of the stent means that the radial force to support a stenosis is particularly sufficient when the lattice structure 10 is expanded to a diameter that is at most 90% of that Rest diameter D _exp is. It is particularly preferred if the insert diameter is at most 90% of the rest diameter D _exp . With such an insert diameter, the radial force of the stent or the lattice structure is preferably at least 0.5 Newton, in particular at least 0.6 Newton. Such radial force values have proven to be particularly efficient for the treatment of stenoses.

In order to achieve such radial force values, the stent according to the invention provides that the web height, which is in the radial direction, i.e. along the in 2 and 3 Cross-sectional diameter shown is measured between 0.05 mm and 0.09 mm. Such a web height, on the one hand, enables good compression of the lattice structure 10 to a very small compressed diameter D _comp and, on the other hand, provides a sufficiently large radial force to keep a stenosis in a blood vessel permanently open.

The geometry of the stent according to the invention according to the exemplary embodiments shown here is in 4 clarified. 4 specifically shows a section of a grid structure 10, with a cell 12 being shown completely. Cell 12 is in 4 a state after cutting the lattice structure 10 from a raw material (“as-cut”). The raw material is preferably a tube with a diameter of 1.5 mm, ie the lattice structure 10 is in the state according to 4 a diameter ser of 1.5 mm. The lattice structure 10 is then expanded to the rest diameter and the shape memory material is conditioned at the rest diameter. Different grid structures 10 with different rest diameters can be formed from the raw material with a diameter of 1.5 mm.

The cell 12 is delimited by the webs 11, with two straight webs 11a arranged parallel to one another and connected to one another by S-shaped webs 11b. The connection between the straight webs 11a and the curved webs 11b takes place via web connectors 14. Each web connector 14 couples a total of four webs 11, namely two straight webs 11a and two curved webs 11b, to one another.

For the advantageous properties of the stent according to the invention, it is necessary to coordinate individual parameters of the stent geometry. These parameters are in particular web height, in particular the web widths S1, S2, the cell length 2x, the cell height 2h and the cell angle 2a.

The straight webs 11a have a first web width S1 and the curved webs 11b have a second web width S2. The first web width S1 is larger than the second web width S2. In particular, the first web width S1 can be at least 25% and at most 33% larger than the second web width S2.

The cell length 2x is defined by the distance between two web connectors 14, which follow one another in direct alignment with one another in the longitudinal direction of the grid structure 10. The cell length 2x is preferably between 2.0 mm and 3.6 mm.

The distance between two web connectors 14 which are immediately adjacent in the circumferential direction and are aligned with one another corresponds to the cell height 2h and is preferably between 1.5 mm and 2.7 mm.

Overall, it has proven to be particularly advantageous if the ratio between the cell length 2x and the cell height 2h is between 1.3 and 1.41.

In a variant according to the invention, the stent described here is preferably used with a modified catheter 20 as a treatment system. The treatment system therefore includes the stent and the catheter 20, these two elements being coordinated with one another. In particular, the increased radial force that the stent offers is supported by the structural design of the catheter 20.

The catheter 20 generally has a first working channel 21 and a second working channel 22. The first working channel 21 is fluidly connected to a balloon 23. A fluid, in particular a liquid, can be introduced into the balloon 23 via the first working channel 21 and removed from it again. The balloon 23 can therefore be filled or inflated and expanded or deflated via the first working channel 21.

The second working channel 22 is preferably arranged coaxially in the first working channel 21. The second working channel 22 extends through the balloon 23 and forms a distal tip of the catheter 20. A marker ring 24 is preferably provided at the distal tip of the catheter 20. Two marker rings 24 are also provided on the second working channel 22 within the balloon 23. The marker rings 24 preferably mark the longitudinal ends of the balloon 23, so that the longitudinal extent of the balloon 23 can be seen under X-ray control.

The structure of the wall of the second working channel 22 is particularly crucial for the good delivery of the stent described above with the increased radial force. The second working channel 22 has a wall that is formed from four layers. A first, innermost layer 25 preferably has friction-reducing properties. In particular, the first layer 25 may comprise or be formed from polytetrafluoroethylene (PTFE), which reduces the frictional forces between a stent and the second working channel 22.

The second working channel 22 is designed as a through-channel, so that the stent described above can be advanced from a proximal end of the catheter 20 directly to a distal end of the catheter 20. This allows the stent to be implanted without having to remove the catheter 20 from the blood vessel in advance. The catheter 20 with the distal balloon 23 therefore enables a combined treatment method. In a first step of the treatment, a stenosis can be expanded radially via the catheter 20 and its balloon 23. Without having to remove or change the catheter 20, it is then possible to introduce a stent to the stenosis, which is then expanded in order to keep the stenosis permanently open.

The first layer 25 made of polytetrafluoroethylene is covered by a second layer 26. The second layer 26 of the second working channel 22 preferably comprises a stabilizing braid. The stabilizing braid can be made of a metal or a metal alloy. A nickel-titanium alloy or stainless steel is preferred here. The stabilization mesh In any case, protects the second working channel 22 from ovalizing when winding through differently curved blood vessels, i.e. from leaving the circular cross-sectional shape. In addition, the stabilization braid stabilizes the entire catheter 20 in the longitudinal direction, making it easier to advance the catheter 20 into a blood vessel.

The second layer 26 is covered by a third layer 27, which preferably consists of polyimide. A fourth layer 28, which forms the outer jacket of the second working channel 22, is preferably formed from a polyether block amide (PEBA). How 6 clearly shown in cross section, the first layer 25, the second layer 26 and the third layer 27 have essentially a similar or identical wall thickness. The fourth, outermost layer 28, on the other hand, has a wall thickness that is greater than the wall thickness of the three other layers 25, 26, 27 combined.

Reference symbols

10

Grid structure

11

web

11a

straight bridge

11b

curved bridge

12

cell

13

End cell

14

Bridge connector

20

catheter

21

first working channel

22

second working channel

23

balloon

24

Marker ring

25

first, innermost layer

26

second layer

27

third layer

28

fourth, outermost layer

30

X-ray markers

Dcomp

compressed diameter

Dexp

expanded resting diameter

S1

first web width

S2

second web width

H

half cell height

2h

Cell height

x

half cell length

2x

Cell length

α

half cell angle

2α

Cell angle

Claims (8)

Stent with a compressible and expandable lattice structure (10) made of webs (11), which are connected to one another in one piece by web connectors (14) and delimit diamond-shaped cells (12), each cell (12) being connected by two straight webs (11a) and two S -shaped curved webs (11b), which connect the straight webs (11a) to one another, and wherein - the lattice structure (10) in a resting state has a fully expanded resting diameter D _exp , which is between 3.0 mm and 5.0 mm, - a ratio between a fully compressed diameter D _komp of the lattice structure (10) and the rest diameter D _exp of the lattice structure (10) is between 1:7 and 1:12, - the webs (11) have a web height that is in radial Direction is measured, which is at least 0.05 mm and at most 0.09 mm, so that the lattice structure (10) has a radial force between the fully compressed diameter D _komp and an insert diameter which is at most 90% of the rest diameter D _exp of at least 0.5 N, in particular at least 0.6 N. Stent after Claim 1 characterized in that the straight webs (11a) have a first web width S1 and the S-shaped curved webs (11b) have a second web width S2, the first web width S1 being at least 25% and at most 33% larger than the second web width S2. Stent after Claim 1 or 2 characterized in that the web connectors (14) of a cell (12), which follow one another in alignment in the longitudinal direction of the lattice structure (10), have a distance in the idle state that defines a cell length 2x, the cell length being between 2.0 mm and 3.6 mm is. Stent according to one of the preceding claims, characterized in that the web connectors (14) of a cell, which follow one another in alignment in the circumferential direction of the lattice structure (10), have a distance in the idle state which defines a cell height 2h, the cell height being between 1.5 mm and is 2.7 mm. Stent after Claim 3 or 4 characterized in that a ratio between the cell length 2x and the cell height 2h is between 1.3 and 1.41. Treatment system for the medical treatment of intracranial stenosis with a Stent according to one of the preceding claims and with a catheter (20) for feeding the stent into a hollow body organ, the catheter (20) having at least two working channels (21, 22) and a balloon (23) which is in the distal region of the working channels ( 21, 22), wherein a first working channel (21) is fluidly connected to the balloon (23) and a second working channel (22) extends through the balloon (23), the second working channel (22) being a through-channel with an inner diameter of at most 0.44 mm. treatment system Claim 6 characterized in that the second working channel (22) has a wall which is constructed at least in sections from four layers (25, 26, 27, 28). treatment system Claim 7 characterized in that a first, innermost layer (25) has polytetrafluoroethylene (PTFE) and is covered by a second layer (26) made of a stabilizing braid, the second layer (26) being surrounded by a third layer (27) made of a polyimide (PI ) and the third layer (27) is surrounded by a fourth, outermost layer (28) made of a polyether block amide (PEBA).

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