JP4555845B2 - Vascular stent - Google Patents

Description

  The present invention is a vascular stent that is inserted into a blood vessel, a lymph vessel, a bile duct, a ureter, or the like, and the vascular stent has a vascular shape when inserted into a living vessel. Used to keep a certain state.

  Conventionally, when a stenosis occurs in a blood vessel of a living body, in particular, a blood vessel such as an artery, the balloon stenosis is formed by inserting a balloon forming part attached near the distal end of the catheter into the stenosis to form a balloon. Percutaneous angioplasty (PTA), which is a surgery to expand blood flow and improve blood flow, has been performed.

  By the way, it is known that even when percutaneous angioplasty is performed, restenosis is generated at a high probability in a portion where stenosis has occurred.

  In order to prevent such restenosis, a tubular stent is inserted into a portion where percutaneous angioplasty has been performed. As shown in FIG. 8, the stent 1 is embedded in the blood vessel 2 in an expanded state, thereby supporting the blood vessel 2 from the inside thereof and trying to prevent restenosis from occurring in the blood vessel 2. It is.

  According to a clinical case where a stent formed by weaving a conventional stainless steel wire in a mesh shape was inserted into a percutaneous angioplasty site, restenosis occurred in about 15%. It has been reported.

In order to prevent such restenosis, a stent formed of a polymer fiber containing a drug for preventing the occurrence of stenosis has been proposed in Japanese Patent Publication No. 5-502179 (WO91 / 01097) (Patent Document 1). ing. In addition, there is one described in Japanese Patent Application Laid-Open No. 10-505527 (Patent Document 2) as being inserted into a blood vessel to maintain blood circulation.
Japanese Patent Publication No. 5-502179 Japanese National Patent Publication No. 10-505527

  By the way, it is known that the restenosis of the blood vessel after the stent is inserted frequently occurs at the end of the stent or from the end.

A stent used by being inserted into a blood vessel is formed to have a sufficiently large rigidity as compared with a blood vessel in order to keep the blood vessel in an expanded state. For example, the Young's modulus of a blood vessel is approximately 3 × 10 ⁷ Pascals, whereas the Young's modulus of stainless steel, which is the main stent material used to hold the blood vessel in an expanded state, is approximately 3 × 10 ¹¹ Pascals. .

  The stent 1 expanded and inserted into the blood vessel 2 holds the blood vessel 2 in an expanded state as shown in FIG. At this time, the blood vessel 2 is reduced in diameter at a position corresponding to each end 1a, 1b of the stent 1 that is no longer supported by the stent 1. At this time, the portions of the blood vessel 1 supported by the end portions 1a and 1b of the stent 1 become stress concentration portions.

  The blood vessel 1, particularly the artery, constantly pulsates because blood flows. Therefore, a load based on pulsation is repeatedly applied to the stress concentration portion of the blood vessel 2 supported by the end portions 1 a and 1 b of the stent 1. As a result, the inner wall of the blood vessel 2 may be damaged by the end portions 1 a and 1 b of the stent 1. Since a load is applied to the stress concentration portion supported by the inner wall of the blood vessel 2, a wound is generated from the inner membrane of the blood vessel 2 and further from the inner membrane to the outer membrane of the blood vessel 2. When the blood vessel 2 is damaged, it repairs the damage as a biological reaction. When repairing damage, the blood vessel 2 may overgrow the intima and cause restenosis.

  An object of the present invention is to provide a novel vascular stent that can solve the problems of conventional vascular stents.

  Another object of the present invention is to provide a vascular stent that can reliably prevent damage to the blood vessel while reliably maintaining the expanded state of the blood vessel such as a blood vessel.

  Still another object of the present invention is to provide a vascular stent that can be inserted into a vascular vessel without generating a stress concentration portion in the vascular vessel.

A vascular stent according to the present invention proposed to achieve the above-described object is a vascular stent that is inserted into a vascular vessel of a living body and holds the inserted vascular vessel from the inside thereof. The tubular body which comprises one flow path is provided from one end part to the other end part side. This tubular body has a uniform thickness from one end side to the other end side, and furthermore, a central main body portion having rigidity sufficient to hold the vessel in an expanded state when inserted into the vessel. A plurality of micropores are formed on both ends of the central main body so that the density gradually decreases from the central main body toward both ends. A low-rigidity portion whose rigidity gradually decreases toward the surface is integrally formed.

  The low-rigidity part is formed by forming a plurality of micropores so that the number gradually increases from the central main body part side to the both end sides of the tubular body.

  Further, the low rigidity portion may be formed by forming a plurality of minute holes so that the hole diameter gradually increases from the central main body portion side to the both end sides of the tubular body.

  The tubular body is desirably formed of a bioabsorbable polymer.

  The vascular stent according to the present invention is constituted by a tubular body integrally formed with a low-rigidity low-rigidity portion at both ends of the central main body portion, so that the vascular vessel is securely held in an expanded state. In addition, it is possible to suppress the occurrence of a stress concentration portion in the vascular vessel. Therefore, the vascular stent according to the present invention can prevent vascular inflammation, excessive thickening, and the like, and can prevent restenosis.

  Hereinafter, a vascular stent to which the present invention is applied will be described in detail with reference to the drawings.

  First, a vascular stent which is intended to solve a technical problem common to the technical problem to be solved by the present invention will be described with reference to the drawings. As shown in FIG. 1, the vascular stent 11 is used by being inserted into a blood vessel such as a coronary artery of a living body, and forms a single flow path from one end side to the other end side. A body 12 is provided. The tubular body 12 is formed using stainless steel having excellent corrosion resistance and biocompatibility.

  In addition, as a metal which comprises the tubular body 12, nickel-titanium alloy, platinum, a tantalum, and platinum other than stainless steel can be used.

  And the tubular body 12 has the center main-body part 13 which has rigidity sufficient to hold | maintain a blood vessel in an expanded state, when inserted in the blood vessel. Low-rigidity portions 14 and 15 having lower rigidity than the central main body portion 13 are integrally formed on both ends of the central main body portion 13. These low-rigidity portions 14 and 15 are formed by making both end portions of the tubular body 12 thinner than the thickness of the central main body portion 13.

  The thin rigid portions 14 and 15 are formed by cutting both ends of the tubular body 12 or forging. At this time, as shown in FIG. 2, the low-rigidity parts 14 and 15 are preferably formed so that the thickness gradually decreases from the thick central main body 13 toward the end of the tubular body 12. . That is, the tubular body 12 is formed with low-rigidity portions 14 and 15 whose rigidity gradually decreases from the central main body 13 side toward both end portions.

At this time, the central main body 13 is formed to have a Young's modulus sufficiently larger than the Young's modulus of the blood vessel so that the blood vessel into which the stent 11 is inserted can be held in an expanded state. Since the Young's modulus of the blood vessel into which the stent 11 is inserted is approximately 3 × 10 ⁷ pascals, the central main body 13 is formed to have a Young's modulus of approximately approximately 3 × 10 ¹¹ pascals. The low rigidity portions 14 and 15 are formed so as to have a Young's modulus substantially equal to or slightly larger than the Young's modulus of the blood vessel.

  As described above, when the stent 11 using the tubular body 12 in which the low-rigidity portions 14 and 15 are formed at both ends of the central main portion 13 having high rigidity is inserted into the blood vessel 16 as shown in FIG. The blood vessel 16 can be held in an expanded state by the central main body portion 13 having high rigidity.

  The blood then flows into the blood vessel 16 via the stent 11. Further, the blood vessel 16 applies a load for reducing the diameter of the stent 11 by pulsating and repeating expansion and contraction. At this time, the low-rigidity portions 14 and 15 formed at both ends of the tubular body 12 are easily elastically displaced by the pulsation of the blood vessel 16 as shown in FIG. That is, the low-rigidity portions 14 and 15 are elastically displaced so that the diameter gradually decreases from the central main body portion 13 toward each end portion of the tubular body 12, thereby generating a portion where stress is concentrated on the blood vessel 16. Can be prevented.

  Since the stent 11 configured as described above can suppress the generation of a portion where stress is concentrated when inserted into the blood vessel 16, damage to the blood vessel 16 can be prevented, and restenosis based on the repair function of the blood vessel 16 can be prevented. Can be suppressed.

  Next, a specific configuration of the vascular stent 11 according to the present invention will be described with reference to the drawings.

  As shown in FIG. 5, the vascular stent 1 according to the present invention is provided with a plurality of minute through holes 116 on each end side of a tubular body 12 having an equal thickness, and the density of each end portion. Is made lower than the density of the central main body 13, low rigidity portions 14 and 15 having lower rigidity than the central main body 13 are formed at each end of the tubular body 12. At this time, it is desirable that the micro holes 116 constituting the low-rigidity portions 14 and 15 are drilled so that the number gradually increases from the central main body portion 13 toward each end portion. By drilling the micro holes 116 in this way, the rigidity of the low-rigidity portions 14 and 15 gradually decreases from the central main body portion 13 toward each end portion.

  Further, the plurality of micro holes 116 are formed so that the hole diameter gradually increases from the central main body portion 13 toward each end portion, whereby the rigidity of the low rigidity portions 14 and 15 is increased from the central main body portion 13 side. It can be gradually reduced toward each end.

  And as shown in FIG. 6, the low-rigidity parts 14 and 15 formed at each end of the tubular body 12 may be formed so that the diameter gradually decreases from the central main body 13 side toward the end. desirable. By forming the tubular body 12 in this way, when the stent 11 is inserted into the blood vessel 16, the diameter of the blood vessel expanded by the central main body portion 13 is gradually reduced to follow the low rigidity portions 14 and 15. As a result, the occurrence of stress-concentrated portions can be more reliably suppressed.

  The above-described stent 11 is made of a metal such as stainless steel, but may be made of a polymer material.

  As shown in FIG. 7, the vascular stent 21 using this polymer material is formed by forming the polymer material into a tubular shape using an injection molding method, an extrusion molding method, or the like, or forming a sheet body made of the polymer material into a tubular shape. The tubular body 22 is provided.

  As the polymer material constituting the tubular body 22, a biocompatible material is selected, and in particular, a bioabsorbable material is selected. As bioabsorbable materials, polylactic acid (PLA), polyglycolic acid (PGA), polyglactin (polyglycolic acid, polylactic acid copolymer), polydioxanone, polyglyconate (trimethylene carbonate, glycolide copolymer), Polyglycolic acid or polylactic acid and ε-caprolactone copolymer can be used. The stent 11 formed of such a bioabsorbable polymer material retains its shape for several weeks to several months after insertion into the blood vessel, but is absorbed into the living tissue around several months after insertion. Can be eliminated.

  As shown in FIG. 7, the tubular body 22 constituting the stent 21 also has a central main body portion 23 having sufficient rigidity to hold the blood vessel in an expanded state when inserted into the blood vessel. Low-rigidity parts 24 and 25 having lower rigidity than the central main body part 23 are integrally formed on both ends of the central main body part 23. These low rigidity portions 24 and 25 are formed by making both end portions of the tubular body 22 thinner than the thickness of the central main body portion 13.

  Such thin low-rigidity portions 24 and 25 are formed by extending both end portions of the tubular body 12.

  The stent 21 using the polymer material may be the one in which the low-rigidity portions 24 and 25 are formed by drilling micro holes in each end portion of the tubular body 22 as in the case of using the metal described above. Good. Further, it is desirable that the low rigidity 24, 25 is formed so as to gradually reduce the diameter from the central main body 23 side toward the end.

  The stent according to the present invention can be used not only for blood vessels but also for living vessels such as lymphatic vessels, bile ducts and ureters.

  The vascular stent according to the present invention is applied to percutaneous angioplasty (PTA), which is a surgery for expanding blood vessel stenosis to improve blood flow.

It is a perspective view which shows the example of the stent for vessels provided with the basic composition of the stent for vessels concerning the present invention. FIG. 2 is a cross-sectional view of the vascular stent shown in FIG. 1. It is a perspective view which shows the state which inserted the stent for blood vessels shown in FIG. 1 in the blood vessel. It is sectional drawing which shows a state when the vascular stent shown in FIG. 1 is inserted in the blood vessel, and the blood vessel beats. 1 is a perspective view showing a vascular stent according to the present invention. FIG. 10 is a cross-sectional view showing another example of a vascular stent, wherein a vascular stent is formed by gradually reducing the diameter of a low-rigidity portion formed at each end of a tubular body. It is sectional drawing which shows the stent for blood vessels which formed the tubular body with the polymer material. FIG. It is a perspective view which shows the state which inserted the conventional vascular stent in the blood vessel.

Explanation of symbols

  11 Vascular Stent, 12 Tubular Body, 13 Central Main Part, 14, 15 Low Rigidity Part, 116 Micropore

Claims (5)

In a vascular stent that is inserted into a vessel in a living body and holds the inserted vessel from the inside thereof,
Comprising a tubular body constituting one flow path from one end to the other end,
The tubular body has a uniform thickness from one end side to the other end side, and is provided with a central main body portion having rigidity sufficient to hold the vessel in an expanded state when inserted into the vessel. In addition, a plurality of micro holes are formed on both ends of the central main body so that the density gradually decreases from the central main body toward both ends, and from the central main body toward the both ends. A vascular stent characterized by integrally forming a low-rigidity portion whose rigidity gradually decreases. The plurality of micropores are formed so as to gradually increase in number from the central main body portion side toward both end sides of the tubular body, and on both end sides of the central main body portion, the both ends from the central main body portion side. The vascular stent according to claim 1, wherein a low-rigidity portion whose rigidity gradually decreases toward the side is integrally formed . The plurality of micro holes are formed so that the hole diameter gradually increases from the central main body portion side to both end sides of the tubular body, and the both ends of the central main body portion are connected to the both ends from the central main body side. The vascular stent according to claim 1, wherein a low-rigidity portion whose rigidity gradually decreases toward the side is integrally formed .   The vascular stent according to any one of claims 1 to 3, wherein the tubular body is formed of a bioabsorbable polymer.   The bioabsorbable polymers include polylactic acid (PLA), polyglycolic acid (PGA), polyglactin (polyglycolic acid, polylactic acid copolymer), polydioxanone, polyglyconate (trimethylene carbonate, glycolide copolymer), poly The vascular stent according to claim 4, wherein the stent is selected from glycolic acid or polylactic acid and an ε-caprolactone copolymer.

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