KR100795125B1 - Coronary artery stent - Google Patents

Abstract

A stent for the coronary artery is provided to reach the stricture part smoothly and to endure the blood pressure by increasing flexibility and resistance against blood pressure. A stent for the coronary artery formed in the shape of a cylindrical metal net to expand blood vessels is composed of a shape maintaining unit(7) formed in the shape of a closed curve and a waveform pattern flexibility applying unit(3). Seven shape maintaining units are connected in an axial direction by the flexibility applying unit. Four shape maintaining units are connected in a circumferential direction by an excessive expansion preventing unit(12). The shape maintaining unit has two shape maintaining curve parts(10) symmetrically formed in the shape of a streamlined closed curve in a longitudinal direction. Excessive expansion preventing unit projections(11), flexibility applying unit projections(8), and shape maintaining projections(9) are symmetrically formed in a staple form at each edge in the middle portion to connect the ends of the shape maintaining curve parts.

Description

Coronary stents {CORONARY ARTERY STENT}

1 is a perspective view for explaining a Palmas stent according to the prior art.

2 is a perspective view of a stent formed by an embodiment of the present invention.

3 is an exploded view of a stent formed by an embodiment of the present invention.

4 is a cross-sectional view of the stent formed by the embodiment of the present invention.

Fig. 5 is an explanatory diagram showing waveform components (shape holding portions) that can be stretched in the circumferential direction of the stent formed in the embodiment of the present invention.

Fig. 6 is an explanatory diagram showing waveform components (flexibility) in the axial direction of the stent formed in the embodiment of the present invention.

7 is a front view showing a shape before expansion of the stent shown in FIG.

8 is a front view showing a shape after expansion of the stent shown in FIG.

** <Explanation of symbols for main parts of drawings> **

3: flexible part 5: horizontal part

6: void reduction curve part 7: shape holding part

8: Flexibility connection connecting protrusion 9: Shape maintaining protrusion

10: shape maintenance curve portion 11: connection expansion prevention portion over projection

12: overexpansion prevention part

The present invention relates to a stent, and more particularly, to a stent for making a general stent, which is an interventional instrument made of metal for the treatment of coronary artery angina or myocardial infarction, to be more flexible and excellent in pressure resistance. will be.

Coronary arteries are blood vessels surrounding the heart. When plaques containing cholesterol and lipids form in the coronary arteries due to various causes, stenosis occurs in the coronary arteries, which impedes the heart muscle from receiving blood. do. This can lead to angina or myocardial infarction, which can lead to death.

The method for treating the disease caused by the vascular stenosis is artificially connected to the stenosis site by bypass surgery after the abdominal incision, or by inserting a balloon catheter into the stenosis vessels fixed to the stricture site and then expand the balloon stenosis Balloon plastic surgery is used to widen the place. However, these methods have problems such as causing pain or restenosis of patients due to major surgery.

In order to overcome the above problems, a method using a stent to insert a stent formed of a metal mesh made of stainless steel to the stenosis vessels to expand the original vessel size to treat the stenosis vessels and maintain normal blood flow This is being used.

The stent is a metal mesh used to normalize the flow by inserting into the disabled site according to an interventional procedure technique, if there is a failure in the flow of blood or body fluid.

The stent should be easy to be transported along the blood vessel to the procedure site because of its flexibility during the procedure, and should have excellent anti-pressure resistance to withstand blood pressure at the site after the procedure, and the area of contact with the vessel is small and expanded through a structural arrangement. Characteristics such as minimizing the percentage of voids are required.

In consideration of the above characteristics, the Palmaz-Schatz stent has been developed and used in the past as shown in FIG. The limitations of the lack of flexibility needed to pass through to reach the desired vessel narrowing area are currently limited.

Various techniques are known for overcoming the above-mentioned problems of Palmaz-Schatz stents and for improving flexibility or breakdown resistance. For example, Korean Patent Laid-Open Publication Nos. 10-1999-010304 and 10-1999-0013858 disclose stents in which wavy protrusions are formed in horizontal branches in order to improve the flexibility of the stent. No. 10-2001-0035531 discloses a stent with improved longitudinal flexibility, and Republic of Korea Patent Publication No. 10-2001-0052430 is relatively flexible along the longitudinal axis direction to facilitate delivery through the winding human lumen A inflatable stent is disclosed. Also, US Pat. No. 6,231,598 discloses a radially expandable stand, while US Pat. No. 6,261,319 discloses a stent for improving flexibility.

In addition, a stent for improving anti-pressure resistance to blood pressure is a stent that can withstand the pressure of blood vessels disclosed in US Pat. No. 6,398,805, and is designed to improve resistance by pressure of blood vessels disclosed in US Pat. Stents; and the like.

However, the above technologies are mainly inventions for improving the characteristics of 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.

In order to solve the above problems, the present invention is flexible in the axial direction before expansion, minimizes the degree of contraction with respect to the length of the axial direction during expansion, and after the expansion, the pressure resistance against the force that the blood vessels try to contract after expansion, stent The purpose is to provide a stent that can evenly expand the strut of the.

In addition, there is another object to provide a stent that is evenly distributed on the inner wall of the vessel after the stent is expanded.

In order to achieve the above object, the present invention is a general stent formed in the form of a cylindrical metal net for expanding blood vessels,

A plurality of shape holding parts having a closed curve shape; Consists of a plurality of flexible parts of the corrugated pattern, each of the seven shape retaining portions in the axial direction are connected by the flexible granting portion, characterized in that the four shape holding portions in the circumferential direction are each connected by the overexpansion preventing portion.

The shape retaining portion is a streamlined closed curve, and two shape maintaining curves are formed symmetrically in the longitudinal direction, and in order to connect the ends of the shape maintaining curves, symmetrical in the center is connected to the overexpansion preventing portion and the flexible portion at each corner. Whether the connecting projection and the shape maintaining projection is formed in the '' 'shape.

The flexibility granting portion is formed in the center of the gap reduction curve intersecting the three arcs, the horizontal portion is formed on both sides of the gap reduction curve portion.

The flexible part is connected to three curved portions consisting of circular arcs having an outer radius of 0.12 and an inner radius of 0.04 mm. The width is 0.08 to 0.1 mm and the total length is 1.16 mm.

The flexible part connecting protrusion for connecting the flexible part and the shape holding part is symmetrically present in one shape holding part, and each protrusion in one shape holding part has a step difference of 1.0 mm with a step of 0.4 mm. They are mutually placed at the position.

When the stent is formed in a planar shape before forming a cylindrical shape, the horizontal length of the shape retaining portion is 2.3 mm and the total length of the vertical direction is 1.6 mm, and the shape maintaining curve is an outer radius of 0.3 mm and an inner radius of 0.2. It consists of an arc of mm, the flexible connecting joint has a radius of 0.04mm, the overexpansion preventing connecting joint consists of an arc of 0.05mm in radius, and the width of the struts is equal to 0.1mm.

Meanwhile, an overexpansion prevention portion is formed to prevent an increase in voids due to excessive expansion when the stent expands during the procedure. Are inclined 63 ° to the horizontal plane and the width of the strut is 0.1mm.

In addition, the diameter of the stent cylinder is about 1.4 to 1.6 mm for the entire stent, and the thickness of the flat plate used to prepare the stent is about 0.095 mm.

Hereinafter, described in detail with reference to the preferred embodiments and the accompanying drawings as follows.

2 to 5, the present invention is a general stent formed in the form of a cylindrical metal net for expanding blood vessels, a plurality of shape holding parts 7 of the closed curve shape; Consists of a plurality of flexible parts (3) of the corrugated pattern, the seven shape holding parts (7) in the axial direction are connected by the flexible part (3), respectively, and four shape holding parts (7) in the circumferential direction Are each connected by the over-expansion prevention portion 12.

The shape retaining portion 7 is a streamlined closed curve in which two shape maintaining curves 10 are formed symmetrically in the longitudinal direction, and symmetrically in the center to connect the ends of the shape maintaining curves 10. Over-expansion preventing portion connecting projections 11, flexible portion connecting projections (8) and shape maintaining projections (9) are formed in each corner in a 'c' shape.

The flexible imparting part 3 is formed in the center of the air gap reduction curve intersecting three arcs, the horizontal portion 5 is formed on both sides of the air gap reduction curve.

The stent (2) of the present invention includes a cylindrical shape having two sides open mesh shape including a flexible portion (3) of a corrugated pattern and a shape holding portion (7) of closed curve shape. It is preferable that the inner angle is 1.710 mm and the outermost angle is 1.805 mm.

The diameter of the cylinder is a value considering the thickness of the coronary artery (generally 2.5 to 3.5mm) and the narrowing of the blood vessels after the narrowing has progressed. If the diameter of the cylinder of the stent 2 is less than 1.4 mm, the diameter of the vessel is not easy. The stent 2 is too thin for its thickness and is not suitable for use as a coronary stent. On the other hand, if it exceeds 2.2 mm, the stent 2 may be thick and reach the vascular stenosis, which may be difficult due to friction, which may damage the vessel in which the stent 2 moves, which is not preferable in terms of flexibility. .

The stent 2 is made of a tube made of metal such as stainless steel by laser cutting or the like. Here, the thickness of the metal pipe which becomes the thickness d11 of the flexible part 3 and the shape maintaining part 7 is 0.095 mm which is a value between about 0.05 mm and 0.1 mm.

The void reduction curves 6 of the flexible part 3 are connected by crossing three arcs having an outer radius of 0.12 and an inner radius of 0.04 mm. The void reduction curve portion 6 plays a big role in solving the problem of increasing the voids around the flexible portion 3 after being expanded with the linear flexibility granting portion without a large difference in the flexibility characteristics compared to the linear type.

The flexible part (3) is installed in parallel with a plurality of intervals of about 0.9 to 1.4 mm, wound in a cylindrical shape as a whole constitute a stent. At this time, the spacing of the flexible portion is also related to the height of the shape retaining portion 7 to be described later. If it is less than 0.9 mm, as a result, the shape retaining portion 7 becomes small, and thus cannot serve as shape retaining. In the case of (2), the flexibility granting portion (3) is more than the number necessary for maintaining the flexibility and difficulty in production. In addition, when the distance between the flexibility granting portion 3 exceeds 1.4 mm, there is a problem in that the number of the flexibility granting portions decreases, so that the flexibility cannot be provided.

The flexible part 3 is to improve the flexibility of the stent (2) while maintaining the anti-pressure resistance to the blood pressure of the stent (2), the stent (2) through the various paths, such as bent blood vessels precisely to the vascular constriction site To be reached.

The shape retaining portion 7 has a connecting protrusion 8 connected to the horizontal portion 5 of the flexible granting portion 3, and extends from the connecting protrusion, so that the shape of the stent 2 according to the change in the breakdown voltage resistance during blood vessel expansion. It is a closed curve shape having a plurality of shape holding projections 9 for maintaining the shape.

Hereinafter, the method for treating the stent 2 formed by the preferred embodiment of the present invention and the physical characteristics of the stent 2 after the procedure will be described.

The stent 2 reaches the site where the blood vessels are constricted, expands by the diameter of a normal blood vessel by a balloon, and the balloon is removed to expand the constricted blood vessel.

Unlike the conventional stent 2, by constructing the stent 2 of the present invention in a closed curve, it is able to withstand resistance due to blood pressure, and after the stent 2 reaches the damaged blood vessel, the original blood vessel diameter by the balloon Designed in advance to predict the length of the stent 2 in the radial direction so that it can be expanded as much as possible, it can be expanded without difficulty.

Referring to FIGS. 7 and 8, in the pre-expansion state in FIG. 7, the flexible part 3 and the shape retaining part 7 of the stent are in the same state as that of the stent 2 described above, but the stent 2 ) In the vessel where the vessel is constricted and inflated to a normal vessel size using a balloon, as shown in FIG. 8, the horizontal portion 5 of the flexible portion 3 is perpendicular to the axis of the stent cylinder. As the degree of expansion increases, the flexible part 3 and the shape maintaining part 7 are connected in a straight line shape.

As the stent 2 is expanded, the shape holding protrusions 9 constituting the plurality of shape holding parts 7 are deformed to prevent deformation of the stent while maintaining resistance to blood pressure. Maintain the shape of (2).

Hereinafter, the performance test results while comparing the stent (2) formed in the preferred embodiment of the present invention with the comparative example is as follows.

[Example]

(Standard of the stent)

The specific specification of the stent of this invention used for the experiment is as follows.

Width (d ₁ ) of the flexible part: 0.08 mm

Width of the flexible part (d ₂ ): 1.16 mm

Spacing of horizontal part of flexible part (d ₃ ): 0.28 mm

Spacing of curved parts of flexible part (d ₄ ): 0.60 mm

Outer radius of circular arc of connecting part with flexibility (r ₁ ): 0.12 mm

Inner radius of circular arc of connecting part with flexibility (r ₂ ): 0.04 mm

Width of the shape maintaining part (d ₅ ): 0.08 mm

Width of the shape retaining part (d ₆ ): 1.66 mm

Width in the vertical direction of the shape retainer (d ₇ ): 1.57 mm

Radius of circular arc of shape retaining curve portion (r ₃ ): 0.33 mm

Tilt of over-expansion preventing connection protrusion (): 63 °

Width of overexpansion prevention part (d ₈ ): 0.11 mm

Vertical length of overexpansion prevention part (d ₉ ): 0.18 mm

Diameter of the stent cylinder (d ₁₀ ): 1.8 mm

Stent cylinder thickness (d ₁₁ ): 0.095 mm

(Flexibility test and interpretation)

In order to judge the flexibility, a method of restraining one end of the stent 2 and applying a force to the other end to obtain a spring constant by the force displacement curve thereby was selected. This is a method of judging the flexibility of the stent (2) by bending stiffness assuming that the stent (2) like a cantilever (canti-lever), the bending stiffness (EI) value of the stent (2) by the shape of the stent (2) It becomes one of the fixed 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 the above formula (1), P is the load, L is the length of the stent, d is the amount of deflection, in this test, P is 10 N, L was 17 mm.

When the stent 2 of the present invention prepared above was analyzed using the finite element method, the EI value of the stent 2 according to the present invention was 40.

(Heat resistance test and interpretation)

After the stent 2 was placed on the damaged blood vessel, the following method was used to test the resistance (anti-pressure resistance) of the stent 2 expanded by the diameter of the normal blood vessel by the balloon.

Once the stent 2 is positioned in the vessel, the stent 2 continues to be pressured from the vessel by blood pressure in the circumferential direction, so the required property is radial stiffness. The stent 2 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 2, whereby the stent 2 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 by the primary or secondary mode which is applied by applying a constant pressure to the circumferential front surface of the stent 2.

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. When the stent 2 of the present invention prepared above was analyzed using the finite element method, the critical pressure value of the stent 2 was 2.3.

(Contact area test and analysis)

The stent (2) is used for the purpose of securing blood flow to the blocked blood vessels and to prevent the contraction of the blood vessels, which 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 (2) occupying in the blood vessel can be minimized in size, mass, and area while maintaining the function, the contact area is the following (Equation 2) Is displayed.

Contact area (%) = metal area / cylindrical area × 100-(Equation 2)

As a result of calculating the contact area of the stent 2 prepared according to Equation 2, the value was derived as 15%.

[Comparative Example]

As a comparative example to show the superior performance of this stent (2), we selected the Palmaz-Schatz stent (PS154 model), a stent that has been applied to the human body for a long time, and compared some models whose performance is known among various stents that are commercially used. Added to the example.

(Flexibility test and interpretation)

As a result of the computer-aided flexibility test analysis in the same manner as in the above example, the EI value of the Palmaz-Schatz stent was able to derive a value of 1869.

(Heat resistance test and interpretation)

As a result of the computer-aided resistance test analysis in the same manner as in the above example, the critical pressure value of the Palmaz-Schatz stent was 1.0.

 (Contact area test and analysis)

As a result of performing contact area test analysis in the same manner as in the above example, the contact area ratio of the Palmaz-Schatz stent was 20%.

The results are summarized in Table 1 when compared with the performance of various stents that are being used commercially.

TABLE 1

flexibility Anti-pressure resistance Contact area (%) Stent of the present invention 40 2.3 15 Palmaz stent 1869 1.0 20 Tenax stent 64 0.7 11 Multilink Stent 52 0.8 15 MAC stent 47 1.2 14

According to Table 1, the stent according to the present invention exhibits very excellent characteristics in terms of flexibility compared to various conventional stents, and exhibits two or more excellent characteristics in anti-pressure resistance, and the contact area is similar to that of a conventional stent. It was confirmed that the appearance is somewhat improved.

While the invention has been described with reference to the preferred embodiments, those skilled in the art will be able to variously modify and change the invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

As described above, according to the stent of the present invention, the flexibility of the stent and the anti-pressure resistance against blood pressure can be improved, and the stent can reach the narrowly confined area and can withstand blood pressure, thereby effectively preventing blood vessel restenosis. You can do it. As a result, various diseases caused by vascular narrowing can be easily treated, and the effect can be stably maintained.

Claims (7)

In the general stent formed in the form of a cylindrical metal net for expanding blood vessels, A shape holding part 7 having a closed curve shape; Consisting of the flexible pattern (3) of the corrugated pattern, the seven shape holding parts (7) in the axial direction are connected by the flexible part (3), respectively, the four shape holding parts (7) in the circumferential direction is excessive Stents, characterized in that each formed by the expansion prevention portion (12). delete The method of claim 1, The shape retaining portion 7 is a streamlined closed curve in which two shape maintaining curves 10 are formed symmetrically in the longitudinal direction, and symmetrically in the center to connect the ends of the shape maintaining curves 10. Stent, characterized in that the over-expansion preventing portion connecting projections (11) and the flexible connection connecting projections (8) and the shape holding projections (9) formed in each of the corners in the 'c' shape. The method of claim 1, The flexible part 3 is characterized in that the void reduction curve portion 6 is formed in the middle of the three arcs intersecting, and the horizontal portion 5 is connected to both sides of the void reduction curve portion 6 Stent. The method of claim 4, wherein The circular arc of the flexible part 3 is connected to the three arcs of the outer radius of 0.12, the inner radius of 0.04mm intersecting, the width is 0.08 to 0.1 mm, the total length is 1.16mm is installed in parallel in the horizontal direction Stent. The method of claim 1, A stent, characterized in that the adjacent shape holding portions (7) of the shape holding portions (7) are arranged with a step on the shape holding portions. Including all of the configuration of claim 1, when formed in a planar shape, the total length in the horizontal direction of the shape holding portion is 2.3mm, the total length in the vertical direction is 1.6mm, the shape holding curve portion 10 has an outer radius 0.3 mm, the inner radius of 0.2mm arc, the flexible connection connecting projections (8) has a radius of 0.04mm, the overexpansion preventing connection connecting projections (11) consists of a circular arc with a radius of 0.05mm, the width of the strut The stent, characterized in that all formed in the same 0.1mm is formed in a cylindrical shape.

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