KR20090044807A - Intracranial stent - Google Patents

Abstract

The present invention relates to a stent for cerebral blood vessels that can expand evenly to the affected area during inflation by improving flexibility and resistance to pressure, and can evenly support blood vessel walls after inflation. The stent according to the present invention has a pair of horizontal shapes disposed horizontally with the axial direction of the stent, and an arc shape disposed between the pair of horizontal shapes and connected to one end of the pair of horizontal shapes. A plurality of shape holding portions having a curved portion; A flexible holding part connected to the shape holding part and extendable in the axial direction of the stent, and the other end of the horizontal shape part is connected to the other end of the horizontal shape part of the shape holding part adjacent in the circumferential direction, The shape retaining portion is connected in the circumferential direction to form a cylindrical shape, and each of the pair of horizontal shaped portions further includes a plurality of arc-shaped stress concentration preventing portions protruding toward the opposite horizontal shaped portions, thereby providing flexibility and blood pressure of the stent. It is possible to improve the anti-resistance against, and can reach the site where the stent is smoothly constricted and at the same time can withstand blood pressure, effectively prevent the restenosis of blood vessels, and can easily treat various diseases caused by blood vessel narrowing Being able to sustain the effect stably, and the concentration of stress in specific areas of the stent A fracture of the stent can be prevented after a couple of insertion preventing stress concentration portion to the holding portion shaped after a certain period of time to prevent.

Description

Cerebrovascular stents {INTRACRANIAL STENT}

The present invention relates to a stent, which is a metal-based interventional instrument for the treatment of cerebrovascular disorders such as cerebrovascular disorders or cerebral infarction, and more specifically, can be expanded evenly in the affected area by swelling by improving flexibility and anti-pressure resistance. It relates to a cerebrovascular stent that can support the vessel wall uniformly after.

In general, cerebrovascular disease is a term used to refer to a disorder of blood vessels supplying blood to the brain. It causes local neurological disorders such as loss of consciousness, paraplegia, and speech disorder due to sudden cerebrovascular disorder. It is a disease that leads to death. Cerebral infarction, which is a high frequency among cerebrovascular diseases, is a disease caused by a blood circulation disorder as clots are deposited and blood vessels are blocked in narrowed cerebral arteries.

In order to treat such diseases caused by vascular stenosis, a balloon catheter is inserted into the constricted blood vessel and fixed to the constricted area, and then balloon augmentation is used to expand the constricted area by expanding the balloon. The methods have problems such as causing pain and restenosis of patients due to major surgery. In addition, cerebrovascular disease has a greater risk of surgical treatment than other organs due to its physiological characteristics, and therefore, minimally invasive treatment is required instead of direct surgery.

In order to overcome this problem, a method using a stent to insert a stent formed of a metal mesh made of stainless steel into the stenosis and expand the original vessel size to treat stenosis and maintain normal blood flow It is used.

Such stents refer to implants in the form of metal nets that are used to normalize the flow of blood or body fluids by inserting them into blocked areas according to interventional procedures without surgical intervention.

Stent intervention, a minimally invasive procedure using stents, inserts a small catheter (catheter) or a thin wire (guide wire) through a blood vessel under X-ray perspective to access the affected area, and then secure a passage with a metal coil or the like in the blocked vessel. It is a treatment to normalize blood flow.

In order for the stent to function stably during the procedure or after insertion into the body, it must have excellent flexibility and anti-pressure resistance to withstand blood pressure in the vessel, and after expansion through structural arrangement with a small contact area with the vessel Characteristics such as minimizing the percentage of voids are required.

As a related art for stents, Korean Patent Laid-Open Publication Nos. 10-1999-010304 and 10-1999-0013858 disclose stents having wavy protrusions formed in horizontal branches in order to improve the flexibility of the stent. Korean Patent Laid-Open Publication No. 10-2001-0035531 discloses a stent with improved flexibility in the longitudinal direction, and Korean Patent Publication No. 10-2001-0052430 discloses a longitudinal axis in order to facilitate delivery through a winding human lumen. Thus, a relatively flexible expandable stent is disclosed.

And stents for improving anti-pressure resistance to blood pressure include stents that can withstand the pressure of blood vessels disclosed in US Pat. No. 6,398,805, and stents designed to improve resistance to blood pressure disclosed in US Pat. No. 6,042,606. Etc. can be mentioned.

However, the above-mentioned prior arts are inventions for improving the characteristics of mainly one of flexibility or anti-pressure resistance to blood pressure, and thus, there is no suggestion of a method for effectively improving flexibility and anti-pressure resistance at the same time.

Most of the prior art stents have been developed in the direction of improving each of the flexibility characteristics and the ability to withstand the pressure separately, and in recent years, technology development has been attempted to satisfy both characteristics, but has not satisfactory effects. I can't.

However, if the flexibility and the pressure resistance are not achieved at the same time, the use value of the stent is greatly reduced. In other words, if the shape and dimensions of the stent are too thin to emphasize flexibility, the stent has a low resistance to blood pressure after expansion in the constriction, causing a problem in the ability to support the radially after the stent has settled in the blood vessel. Designing a stent with emphasis on resistance to it may be a problem that it is impossible or very difficult to reach the stent of the vessel during the procedure. In addition, the increase in cross-sectional area may cause a problem of restenosis.

Therefore, there is an urgent need for the development of a stent that satisfies both the flexibility and the breakdown resistance at the same time while minimizing the cross-sectional area.

The present invention is to solve the above-mentioned problems of the prior art, the object of the present invention, through the structure different from the conventional stents have good flexibility characteristics and excellent anti-pressure resistance to blood pressure, and the contact area with blood vessels At the same time, the stent provides a stent that supports the vessel wall evenly after expansion.

The present invention, in consideration of the characteristics of the stent described above, is flexible in the axial direction before expansion, the degree of contraction with respect to the length of the stent axis direction during the stent expansion is minimized, and resistance to the force that the blood vessel is about to contract after expansion An object of this invention is to provide a stent capable of uniformly expanding the stent of the stent.

In addition, another object of the present invention is to provide a stent that can be evenly distributed on the inner wall of the vessel even after expansion to prevent restenosis.

In order to achieve the above object, the cerebrovascular stent according to the present invention, in the circumferentially expandable cerebrovascular stent, a pair of horizontal shape portion disposed horizontally with the axial direction of the stent, the pair A plurality of shape holding parts disposed between the horizontal shape parts of the plurality of shape holding parts having arc-shaped curved parts connected to one end of the pair of horizontal shape parts; And a flexible retaining portion connected to the shape holding portion and extendable in the axial direction of the stent, and the other end of the horizontal shape portion is connected to the other end of the horizontal shape portion of the shape holding portion adjacent in the circumferential direction. The shape maintaining part is connected in the circumferential direction to form a cylindrical shape.

Each of the pair of horizontal portions further includes a plurality of arc-shaped stress concentration preventing portions protruding toward the opposite horizontal portion.

The flexible retaining unit is not connected to each of the plurality of shape maintaining units, characterized in that arranged at a predetermined interval.

The flexible holding part includes a horizontal connection part connected to the shape holding part, a plurality of inclined shape parts connected at one end to the horizontal connection part and inclined with respect to the axial direction of the stent, and the plurality of inclination forming parts. It characterized in that it comprises a plurality of curved portions arranged.

The curved portions of the plurality of shape holding portions may have different radii of curvature, and the horizontal portions of the plurality of shape holding portions may have different lengths.

The stress concentration prevention portion is characterized in that formed in a U-shaped or Ω shape.

The angle between the inclination forming portion and the horizontal connecting portion of the flexible retainer is characterized in that the range of 120 ° to 150 °.

According to the cerebral vascular stent according to the present invention having the configuration as described above, since the blood vessel is intended to be applied in intracranial vessels smaller than 1/10 of the carotid artery, it has a fine size compared to the existing stent. It is possible to improve the stent's flexibility and resistance to blood pressure to mechanically express its performance, so that the stent can reach the tightly confined area and can withstand blood pressure, effectively preventing blood vessel restenosis. can do. As a result, various diseases caused by vascular narrowing can be easily treated, and there is an advantage that the effect can be stably maintained.

The flexibility of the stent and its resistance to blood pressure can be improved, and the stent can be distributed throughout the affected area, allowing the stent to reach the tightly constricted area and withstanding structural blood pressure, thereby restoring blood vessels. Can be effectively prevented.

In addition, the stent according to the present invention is excellent in the longitudinal flexibility and the pressure resistance to support the inner wall of the vessel, compared to the prior art stent, it is possible to minimize the degree of shrinkage in the longitudinal direction, radial direction after balloon-catheter removal In order to prevent the stress from being concentrated on a specific part of the stent, a stress concentration prevention part may be provided in the shape maintaining part to prevent the stent from being destroyed even after a certain time after insertion.

Hereinafter, with reference to the accompanying drawings, it will be described in detail with respect to the cerebral vascular stent according to the present invention.

1 is a perspective view showing a stent according to the present invention, FIG. 2 is a development view thereof, and FIG. 3 is a front view thereof.

As shown in FIGS. 1 to 3, the stent 1 according to the present invention has a plurality of shape holding portions 10 and a flexible holding portion 20 connecting the shape holding portions in the axial direction, that is, the longitudinal direction of the stent. Consists of

The stent as a whole includes a flexible shape holding part 20 of the wave shape and a curved shape holding part 10 having different shapes, and has a mesh shape of a net shape in which both ends are open.

The diameter of the cylinder formed by the stent may be a value in consideration of the thickness of the blood vessels after the progress of the thickness and narrowing of the cerebrovascular vessel. If the diameter of the stent cylinder is less than 0.9 mm, it is not easy to manufacture and the stent is too thin compared to the thickness of the blood vessel, which is not suitable for use as a cerebrovascular stent. On the other hand, if the thickness exceeds 1.25mm, the stent is difficult to reach the vascular stenosis due to friction, etc. This may damage the vessel to which the stent moves, and is not preferable in terms of flexibility.

The stent is formed in a cylindrical tube shape by forming a shape of the flexible holding portion and the shape holding portion by, for example, laser cutting on a tube made of a material such as stainless steel, titanium, or nitinol alloy. Here, the thickness of the flat plate which becomes the thickness of a flexible holding part and a shape holding part is 0.09 mm, for example.

After the stent reaches the site where the blood vessel is constricted, the balloon is inflated by the diameter of the normal blood vessel by a balloon, and the balloon is removed except the stent. Unlike the conventional stent, the stent has a large and gentle curve. It is possible to withstand the resistance due to blood pressure, and to predict and design the diameter length of the stent in advance so that the stent can be inflated by the balloon after reaching the damaged vessel, it can be expanded without difficulty. .

The shape holding part 10 is comprised from a pair of horizontal shape part 11 and the curved shape part 12. As shown in FIG. The pair of horizontal portions 11 are arranged horizontally with the axial direction of the stent, and the curved portion 12 is disposed between the pair of horizontal portions and one end of the pair of horizontal portions It consists of an arc shape connected to.

In addition, the other end of the horizontal shape portion is connected to the other end of the horizontal shape portion of the shape holding portion adjacent in the circumferential direction so that the plurality of shape holding portions are connected in the circumferential direction to form a cylindrical shape.

4 is a view showing a shape holding portion of the stent according to the present invention, Figures 4a to 4e is a view showing a plurality of shape holding portions 13, 14, 15, 16, 17 having different lengths and different curvatures. to be.

As shown in Figs. 4A to 4E, the curved portions of the plurality of shape holding portions have different radii of curvature, and each of the horizontal shaped portions of the plurality of shape holding portions has a different length, and is arranged in the circumferential direction. Stretchable corrugated components are evenly distributed in the vessel wall during stent expansion and can resist pressure in the vessel wall. Thus, the structure of the curved shape maintaining portion of the present invention can be expected to improve performance in the shape holding function compared to the shape structure of the conventional stent.

The length in the horizontal direction (the axial direction of the stent) of the plurality of shape holding portions, the length in the vertical direction, the inner and outer radius of the curved portion, and the width of the strut are determined by the diameter and the required length of the cylinder of the stent inserted into the blood vessel. Can be adjusted accordingly.

5 is a view showing a flexible retention portion of the stent according to the present invention. As shown in FIG. 5, the flexible holding part 20 is configured to be connected to the shape holding part and to be stretchable in the axial direction of the stent.

The flexible retainer 20 may play a large role in solving the problem of increasing voids around the flexible retainer after expansion, which has a linear flexible retainer, without a large difference in flexibility characteristics compared to the linear flexible retainer.

The pore refers to an empty space of a stent having a predetermined pattern, and as the pore increases, the stent acts as a negative factor for supporting the vessel wall uniformly after expansion.

As shown in FIG. 2, the flexible holder 20 is provided in a horizontal manner in a plurality of stepwise parallel manners, and is arranged at a predetermined interval in the vertical direction without being connected to each of the plurality of shape holding parts. For example, it is installed in parallel with a 1.47mm interval is wound in a cylindrical shape as a whole to constitute a stent.

Under the above-described specific conditions, the flexible maintaining part may improve the flexibility of the stent while maintaining the anti-pressure resistance to the blood pressure of the stent, so that the stent can accurately reach the vascular constriction site through various paths such as a curved blood vessel.

The flexible holder 20 has a horizontal connection portion 21 connected to the shape holding portion, and a plurality of inclined portions 22 having one end connected to the horizontal connection portion and inclined with respect to the axial direction of the stent. And a plurality of curved portions 23 disposed between the plurality of inclination forming portions.

It is preferable that the plurality of inclination-forming parts 22 which serve to reduce voids when the stent is expanded while maximizing flexibility in the longitudinal direction are inclined to have a predetermined inclination with respect to the axial direction of the stent. That is, the angle between the inclined forming portion and the horizontal connecting portion of the flexible retaining portion is preferably in the range of 120 ° to 150 °. As a result, it is possible to minimize the voids around the flexible retaining part after the expansion of the stent and to prevent the stent from being broken at the connection point with the horizontal connection part when the stent is expanded in the axial and vertical directions.

The inclined forming portion and the curved portion 23 of the flexible retaining portion 20 are provided in plural so as to minimize the voids of the stent even when the stent is expanded.

By the above-described configuration, the shape maintaining part of the stent is formed of a combination of curves having different half diameters and a plurality of shape holding parts having different lengths so that the front surface of the stent can be expanded evenly and flexible. The holding part facilitates the change in the longitudinal direction, and the flexible holding part is also processed to be curved to improve the excessive voids that may occur in the flexible holding part after expansion.

On the other hand, the horizontal portion has a stress concentration prevention portion. 6 is a view for conceptually explaining the stress concentration prevention unit according to the present invention.

The stress concentration prevention part is to improve the durability of the stent, and the blood vessels undergo continuous contraction / relaxation movement according to the heartbeat. As a result, the stent supporting the blood vessel wall receives continuous external pressure over the entire surface. Periodically applied pressure increases fatigue in the stent structure and eventually leads to failure. Due to its structural characteristics, breakage is likely to occur at the portion where the degree of deformation of the stent is large. As shown in FIG.

As shown in FIG. 6, the stent according to the present invention further includes a plurality of stress concentration preventing portions 30 each having an arc shape protruding toward the opposing horizontal portion. In addition, the said stress concentration prevention part is formed in a U-shape or an ohm-shape, for example.

The stent according to the present invention is provided with a pair of stress concentration branches existing in the horizontal shape portion, as shown in Figure 6a, as shown in Figure 6a at the time of stent expansion, the stress concentration preventing portion is stretched in the direction of the arrow, By effectively dispersing the stress concentrated on the curved portion of the shape maintaining portion, the concentration of fatigue can be dispersed over the entire surface of the stent structure, thereby increasing the durability of the stent.

In addition, due to the elastic properties of a general metal material, the stent also has a property of returning to its original shape after expansion, which is larger as more stress is generated in the deformed portion. Therefore, the degree of shrinkage decreases as the stress concentrated on the deformed portion is reduced or dispersed. The curved portion of the stress concentration preventing portion reduces the stress applied to the curved portion of the shape maintaining portion and disperses the stress in the overall direction. This reduces the extent of shrinkage in the radial direction.

7 and 8 show the shapes before and after expansion of the stent according to the present invention having the configuration as described above. 7 is a side view conceptually showing a shape before expansion of the stent shown in FIG. 1. 8 is a side view conceptually showing a shape after expansion of the stent shown in FIG. 1.

In the pre-expansion state of FIG. 7, after the stent is attached to the site where the blood vessels are constricted, the balloon is horizontally connected to the flexible vessel as shown in FIG. It is maintained and connected in a horizontal form even if the degree of expansion increases, without twisting or deformation of the shape.

The test results for the flexibility, the breakdown voltage, and the contact area of the stent according to the present invention having the above-described configuration will be described.

(Flexibility test and interpretation)

In order to judge the flexibility, we chose a method of restraining one end of the stent and applying a force to the other end to obtain the spring constant by the force displacement curve. This is a method of judging the stent as a cantilever beam (canti-lever beam) to determine the flexibility in bending rigidity, the bending stiffness (EI) value of the stent 1 is fixed by the shape of the stent (1) It becomes one of physical properties, and the smaller the EI value, the better the flexibility. Specific EI is represented by the following Formula 1.

EI = PL ³ / 3d (Equation 1)

In Equation 1, P is the load, L is the length of the stent, d means the amount of deflection.

As a result of analyzing the flexibility of the prepared stent 1 of the present invention using the finite element method, the EI value of the stent according to the present invention was 1.689.

(Heat resistance test and interpretation)

The following method was used to test the resistance (anti-pressure resistance) that the stent (1) inflated by the diameter of the normal blood vessel by the balloon after the stent (1) is placed on the damaged blood vessel.

Once the stent 1 is positioned in the vessel, the stent 1 is continually subjected to pressure from the vessel by blood pressure in the circumferential direction, so the required property is radial stiffness. The stent 1 in the vessel is subjected to a compression pressure in the opposite direction of the inflation pressure, which presses over the front surface of the stent 1, whereby the stent 1 has the possibility of deformation. Accordingly, in this case, a method for measuring the radial intensity was used as a method of determining the critical pressure in the primary or secondary mode, which appears by applying a constant pressure to the circumferential front surface of the stent 1. Pcr. = P Eigenvalue (Equation 2)

In Equation 2, Pcr. Denotes a critical pressure, P denotes a load, and an eigenvalue denotes a characteristic value unique to each object.

The larger the critical pressure value obtained through this process, the better the pressure resistance caused by blood pressure. The critical pressure value was 1.317 as a result of analyzing using the prepared stent 1 of this invention using the finite element method.

(Contact area test and analysis)

Since the stent 1 is used for the purpose of securing blood flow to the blocked blood vessels and to prevent the contraction of the blood vessels, the stent 1 is beneficial to human life and health, but on the other hand, it corresponds to a foreign substance to the human body. It is desirable to minimize in all respects such as size, mass, and area within.

The coverage area test is a test to determine whether the stent 1 occupying in the blood vessel can be minimized in size, mass and area while maintaining its function. Is displayed.

         Contact area (%) = metal area / cylindrical area × 100 (Equation 3)

As a result of calculating the contact area of the stent 1 prepared according to Equation 3, the value was derived as 13.985%.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings attached to this specification clearly show some of the technical ideas included in the present invention, and modifications that can be easily inferred by those skilled in the art within the scope of the technical ideas included in the specification and drawings of the present invention. It is obvious that both and specific embodiments are included in the scope of the technical idea of the present invention.

1 is a perspective view showing a stent according to the present invention.

FIG. 2 is a developed view of the stent shown in FIG. 1.

3 is a front view of the stent shown in FIG. 1.

4 is a view showing a shape holding part of the stent according to the present invention, Figures 4a to 4e is a view showing a plurality of shape holding parts having different lengths and different curvatures.

5 is a view showing a flexible retention portion of the stent according to the present invention.

6A and 6B are views for conceptually explaining a stress concentration prevention unit.

7 is a side view conceptually showing a shape before expansion of the stent shown in FIG. 1.

8 is a side view conceptually showing a shape after expansion of the stent shown in FIG. 1.

<Description of the symbols for the main parts of the drawings>

1 stent

10: shape holding part

11: horizontal shape

12: curved portion

20: flexibility maintainer

21: horizontal connection

22: inclined forming part

23: curved portion

30: stress concentration prevention part

Claims (7)

In the circumferentially expandable cerebrovascular stent, A plurality of horizontal portions arranged horizontally and axially of the stent, and a plurality of arc-shaped curved portions disposed between the pair of horizontal portions and connected to one end of the pair of horizontal portions; A shape holding part; It is configured to include a flexible retaining portion connected to the shape holding portion and extendable in the axial direction of the stent, And the other end of the horizontal portion is connected to the other end of the horizontal shape portion of the shape holding portion adjacent in the circumferential direction, and the plurality of shape holding portions are connected in the circumferential direction to form a cylindrical shape. The stent for cerebrovascular according to claim 1, wherein each of the pair of horizontal shaped portions further includes a plurality of arc-shaped stress concentration preventing portions protruding toward the opposite horizontal shaped portions. [Claim 2] The stent for cerebrovascular according to claim 1, wherein the flexible retaining portion is disposed at a predetermined interval without being connected to each of the plurality of shape maintaining portions. The method of claim 1, wherein the flexible retainer, A horizontal connection part connected to the shape maintaining part; A plurality of inclined portions having one end connected to the horizontal connecting portion and inclined with respect to the axial direction of the stent; A cerebral blood vessel stent, comprising: a plurality of curved portions disposed between the plurality of inclination forming portions. The method of claim 2, The curved portions of the plurality of shape holding portions have different radii of curvature, Each of the horizontal shape portions of the plurality of shape holding parts has a different length from the cerebral vessel stent. [Claim 3] The stent for cerebrovascular according to claim 2, wherein the stress concentration preventing part is formed in a U-shape or Ω-shape. The stent for cerebrovascular according to claim 4, wherein the angle between the inclined portion and the horizontal connection portion of the flexible retaining portion is in the range of 120 ° to 150 °.

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