Stent

Abstract

To provide a stent which can be smoothly stored in a delivery catheter, can be smoothly released from the delivery catheter, and can retain a knitting and weaving pattern and uniformity of cells against external force.SOLUTION: A stent 3 comprises an entangled knot part 11 and an overlapped knot part 12 formed of two wire parts of a wire 10. In the entangled knot part 11, the two wire parts are bent and entangled with each other. In the overlapped knot part 12, two wire parts are overlapped in inside and outside directions of the stent 3 while each extending straight. In wavy overlapped parts 12A, insertion positions of the wire parts are opposite to insertion positions in an adjacent knot part 3p. In flat overlapped parts 12B, insertion positions of the wire parts are the same as insertion positions in the adjacent knot part 3p. In end regions 3A, 3B at both sides in an axial direction of the stent 3, the wavy overlapped parts 12A are more than the flat overlapped parts 12B, and in an intermediate area 3C, the flat overlapped parts 12B are more than the wavy overlapped parts 12A.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a stent used for improving an occluded or stenotic lesion, and particularly to a cylindrical stent knitted in a diagonal lattice pattern.

Background Art

[0002] For example, a treatment procedure is known in which a lesion occluded or stenosed due to colon cancer or the like is opened, and a cylindrical stent is placed therein to maintain the opened state. This type of stent is, for example, in the form of a cylinder knitted from two wire rods (wires) in a diagonal lattice pattern (see Patent Document 1, etc.). A rhombus-shaped cell is formed by the wire portions connecting four nodal portions arranged in a ring in the diagonal lattice. Part of the lattice points, i.e., nodal portions, of the diagonal lattice of the stent are entangled nodal portions in which two wire portions are bent in an L shape and entangled with each other. The other nodal portions are overlapping nodal portions in which two wire portions extend straight and overlap each other inside and outside (in the radial direction of the stent). In particular, by passing through the adjacent nodal portions on the opposite inner and outer sides, they are overlapped in a wavy manner to form a wavy overlapping portion.

[0003] Generally, after manufacturing, the stent is narrowed in the radial direction and accommodated in the tip of a dedicated delivery catheter. The delivery catheter is brought to the operation site. Then, the operator inserts the delivery catheter to the lesion of the patient, and the stent is released from the tip of the delivery catheter and deployed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the conventional stent with the knitting structure, the entangled knot parts strongly resist external forces such as tension, and friction also works at the wavy overlapping parts, so that the diagonal lattice knitting pattern and the deformation of each cell are suppressed. On the other hand, when the stent is radially contracted and narrowed, the entangled knot parts and the wavy overlapping parts arranged in the circumferential direction gather together, resulting in local bumps or bamboo flute shapes. Therefore, when the stent is narrowed and inserted into the tip of the delivery catheter, the resistance increases, and it is difficult to smoothly insert the stent into the delivery catheter. Also, when releasing the stent from the tip of the delivery catheter during the procedure, the release resistance increases. In particular, when the diameter of the delivery catheter is reduced, it becomes difficult to insert and remove the stent from the delivery catheter. In view of such circumstances, an object of the present invention is to provide a stent that can be smoothly accommodated in a delivery catheter, smoothly released from the delivery catheter, and can maintain the knitting pattern and the uniformity of cells against external forces.

Means for Solving the Problems

[0006] In order to solve the above problems, in one aspect of the present invention, there is provided a cylindrical stent knitted in a diagonal lattice pattern by one or more wires, comprising entangled knot parts and overlapping knot parts formed by two wire parts of the wire, in the entangled knot part, the two wire parts are bent and entangled with each other, in the overlapping knot part, the two wire parts extend straight and overlap each other in the inner and outer directions of the stent, and the overlapping knot part includes a wavy overlapping part and a flat overlapping part, in the wavy overlapping part, the passing position in the inner and outer directions of one wire part constituting the wavy overlapping part with respect to the other wire part is opposite to the passing position at the location from the entangled knot part or the overlapping knot part close to the one wire part to the wavy overlapping part, In the flat overlapping portion, the through position in the inner-outer direction of one wire portion constituting the flat overlapping portion with respect to the other wire portion is the same as the through position at a location from a tangling node portion or an overlapping node portion adjacent to the one wire portion toward the flat overlapping portion, In the end regions on both sides of the stent in the axial direction, the undulating overlapping portion is more than the flat overlapping portion, In the intermediate region between these end regions, the flat overlapping portion is more than the undulating overlapping portion.

[0007] According to the stent, the frictional resistance between two wire portions in the undulating overlapping portion is relatively large, and the frictional resistance between two wire portions in the flat overlapping portion is relatively small. Therefore, in addition to the tangling node portion strongly resisting an external force such as tension, friction also works in the undulating overlapping portions of both end regions, so that the deformation restraining action extends over the entire area of the stent. As a result, the knitting pattern and the uniformity of the cells of the entire stent are maintained. On the other hand, particularly in the intermediate region of the stent, it is easier to expand and contract due to the small frictional resistance of the flat overlapping portion, and when the stent is narrowed, even if the flat overlapping portions gather, they do not become locally bumpy or bamboo shoot-like. As a result, the stent narrowed in the delivery catheter can be smoothly accommodated. And the stent can be smoothly released from the delivery catheter and deployed.

[0008] Preferably, most of the overlapping node portions in the end regions are the undulating overlapping portions, and most of the overlapping node portions in the intermediate region are the flat overlapping portions. Here, "most" means preferably 80% or more, more preferably 90% or more of the overlapping node portions in each region.

[0009] Preferably, the length of the intermediate region along the axial direction is larger than the length of the end region. Thereby, the region where the unevenness is alleviated when the stent is narrowed can be widened, and the stent can be surely and smoothly inserted into and removed from the delivery catheter.

[0010] In the end region, the number of axially arranged nodes including the entangled node portion and the overlapping node portion is preferably 1 or more and 4 or less. As a result, regardless of the length of the entire stent, an end region can be secured to reliably exhibit the deformation suppressing effect, and the intermediate region can be made as long as possible to facilitate the insertion and removal of the stent into and out of the delivery catheter.

Advantages of the Invention

[0011] According to the stent of the present invention, it can be smoothly accommodated in a delivery catheter, smoothly taken out from the delivery catheter, and moreover, the deformation of the knitting pattern and cells can be suppressed against external forces such as pulling.

Brief Description of the Drawings

[0012]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Figure 1(a) shows the delivery system 1. The delivery system 1 is used for treatment procedures of occluded or stenosed lesions such as colorectal cancer, and includes a delivery catheter 2 and a stent 3. The delivery catheter 2 includes an inner shaft 4 and an outer tube 5. The inner shaft 4 is inserted axially movably into the outer tube 5. A tubular stent 3 woven in a diagonal lattice pattern is radially narrowed and fitted onto the outer periphery of the tip of the inner shaft 4. The outer tube 5 covers the outer periphery of the stent 3. Thus, the stent 3 is accommodated at the tip of the delivery catheter 2 while being sandwiched between the inner shaft 4 and the outer tube 5. In that state, the tip of the delivery catheter 2 is inserted into a previously opened lesion. Then, as shown in Figure 1(b), the stent 3 is released from the delivery catheter 2 and elastically expanded in diameter and left in the lesion. Thereby, the patency of the lesion is maintained.

[0014] As shown in Figure 2, the stent 3 is composed of two (a plurality of) wires 10. The material of the wire 10 is preferably a springy metal, and more preferably a shape memory alloy having springiness such as a nickel-titanium alloy.

[0015] By weaving these wires 10 so as to form a diagonal lattice cylindrical shape, the stent 3 is constituted. At each node 3p constituting the lattice points of the diagonal lattice of the stent 3, two portions of the wire 10 (hereinafter "wire portions 10a, 10b, 10c, 10d, 10e, 10f...") intersect each other. A rhombic cell 3q is formed by the wire portions connecting four annularly arranged nodes 3p. Note that both ends of each wire 10 are connected by a connecting member 15. Thereby, each wire 10 is in a closed annular shape.

[0016] The node portion 3p formed by the two wire portions is roughly classified into an entangled node portion 11 and an overlapping node portion 12. As shown in FIG. 3, in the entangled node portion 11, the two wire portions 10a and 10b are each bent in an L shape and are entangled with each other. One wire portion 10a wraps around the other wire portion 10b from the outside to the inside or from the inside to the outside in the radial direction (inside-outside direction) of the stent 3. Each entangled node portion 11 is composed of two wire portions 10a and 10b of the same wire 10, but the entangled node portion may be formed by crossing such that a part (wire portion) of two different wires are entangled with each other.

[0017] As shown in FIGS. 3 and 5, in the overlapping node portion 12, the two wire portions extend straight without being bent and overlap each other in the inside-outside direction. The overlapping node portion 12 may be formed by overlapping two wire portions of the same wire inside and outside, or may be formed by overlapping wire portions (parts) of two different wires inside and outside.

[0018] More specifically, the stent 3 includes a wavy overlap portion 12A and a flat overlap portion 12B as the overlapping node portion 12. As shown in FIG. 3, in the wavy overlap portion 12A, the inside-outside passing position of one wire portion constituting the wavy overlap portion 12A with respect to the other wire portion is opposite to the inside-outside passing position at the location from the entangled node portion 11 or the overlapping node portion 12 close to the one wire portion toward the wavy overlap portion 12A. In short, as shown in FIGS. 3 and 4, in the node portion 3p1 close to the wavy overlap portion 12A, the wire portion 10c extending from the inside (the back side of the paper in FIG. 3 and the lower side in FIG. 4) of the other wire portion 10e toward the wavy overlap portion 12A is passed outside the other wire portion 10d in the wavy overlap portion 12A (the front side of the paper in FIG. 3). In the node portion 3p2 close to the wavy overlap portion 12A, the wire portion 10d extending from the outside of the other wire portion 10f toward the wavy overlap portion 12A is passed inside the other wire portion 10c in the wavy overlap portion 12A.

[0019] As shown in FIG. 5, in the flat overlapping portion 12B, the through position in the inner and outer direction of one wire portion of the flat overlapping portion 12B with respect to the other wire portion is the same as the through position at the location from the entanglement node portion 11 or the overlapping node portion 12 adjacent to the one wire portion toward the flat overlapping portion 12B. In short, as shown in FIGS. 5 and 6, at the node portion 3p3 adjacent to the flat overlapping portion 12B, the wire portion 10g extending from the inner side of the other wire portion 10i (the back side of the paper in FIG. 5, the lower side in FIG. 6) toward the flat overlapping portion 12B is passed through the inner side of the other wire portion 10h also in the flat overlapping portion 12B. At the node portion 3p4 adjacent to the flat overlapping portion 12B, the wire portion 10h extending from the outer side of the other wire portion 10j (the front side of the paper in FIG. 5) toward the flat overlapping portion 12B is passed through the outer side of the other wire portion 10g also in the flat overlapping portion 12B.

[0020] The node portion adjacent to the overlapping node portion 12 may be the entanglement node portion 11 or another overlapping node portion 12. The flat overlapping portion 12B only needs to have the through position of at least one wire portion constituting it be the same as the through position at the location from at least one adjacent entanglement node portion 11 or overlapping node portion 12 toward the flat overlapping portion 12B.

[0021] As shown in FIG. 2, in the intermediate region 3C in the axial direction of the stent 3, the ratio of the flat overlapping portion 12B in the overlapping node portion 12 is larger than that in the end regions 3A and 3B on both sides in the axial direction of the stent 3. Preferably, in the intermediate region 3C, the ratio of the flat overlapping portion 12B in the overlapping node portion 12 is more than the ratio of the undulating overlapping portion 12A. In the end regions 3A and 3B, the ratio of the undulating overlapping portion 12A in the overlapping node portion 12 is more than the ratio of the flat overlapping portion 12B. More preferably, most of the overlapping node portion 12 in the intermediate region 3C is the flat overlapping portion 12B. Most of the overlapping node portion 12 in the end regions 3A and 3B is the undulating overlapping portion 12A. The number of axial nodes (the number of axial arrangements of the node portions 3p) in each end region 3A, 3B is preferably 1 or more and 4 or less.

[0022] According to the stent 3, the entangled node portion 11 strongly resists external forces such as tension. Also, the frictional resistance between the two wire portions in the wavy overlapping portion 12A is greater than the frictional resistance in the flat overlapping portion 12B. For this reason, in addition to the resistance of the entangled node portion 11 to the external force, friction also acts on the wavy overlapping portions 12A that are mostly distributed in the end regions 3A, 3B on both sides, so that a deformation restraining force acts in the end regions 3A, 3B on both sides, and the deformation restraining force is transmitted from each end region 3A, 3B to the central region 3C, thereby exerting a deformation restraining effect over the entire area of the stent 3. As a result, the uniformity of the knitting pattern of the entire stent 3 is maintained, and the size and shape of the cells 3q are uniformly maintained. Incidentally, if the deformation restraining force is only manifested in one end region, it is difficult for the deformation restraining effect to reach the opposite end region, and the size and shape of the cells 3q in the opposite end region are likely to collapse. If the deformation restraining force is only manifested at the central part of the stent, it is difficult for the deformation restraining effect to reach at least one end region, and the size and shape of the cells 3q in that end region are likely to collapse. On the other hand, in the intermediate region 3C of the stent 3, since the distribution ratio of the flat overlapping portions 12B is high and the frictional resistance thereof is small, it is easily expanded and contracted. Moreover, when the stent 3 is radially contracted and narrowed, even if the flat overlapping portions 12B gather, they do not become local bumps or bamboo flute shapes. As a result, the narrowed stent 3 can be smoothly accommodated in the delivery catheter 2. And the stent 3 can be smoothly released from the delivery catheter 2.

[0023] The present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit thereof. For example, the number of wires 10 is not limited to 2, and may be 1 or 3 or more.

Industrial Applicability

[0024] The present invention can be applied to, for example, a therapeutic device for an occluded or stenotic lesion.

Explanation of Reference Numerals

[0025] 1 Delivery system 2 Delivery catheter 3 Stent 3A, 3B End region 3C Intermediate region 3p Node 3q Cell 10 Wire 10a - 10j Wire portion 11 Entangled node 12 Overlapping node 12A Wavy overlap portion 12B Flat overlap portion

Claims

1. A cylindrical stent knitted in a diagonal lattice pattern by one or more wires, comprising entanglement nodes and overlapping nodes formed by two wire portions of the wire, wherein in the entanglement nodes, the two wire portions are each bent and intertwined with each other, and in the overlapping nodes, the two wire portions extend straight and overlap each other in the inner and outer directions of the stent, and the overlapping nodes include a wavy overlap portion and a flat overlap portion, wherein in the wavy overlap portion, the inner and outer direction passing position of one straight wire portion constituting the wavy overlap portion with respect to the other wire portion is opposite to the inner and outer direction passing position of the straight wire portion in the entanglement node or overlapping node adjacent to the wavy overlap portion along the extending direction of the straight wire portion with respect to the wire portion that is the counterpart of the entanglement or overlap of the straight wire portion, wherein in the flat overlap portion, the inner and outer direction passing position of one straight wire portion constituting the flat overlap portion with respect to the other wire portion is the same as the inner and outer direction passing position of the straight wire portion in the entanglement node or overlapping node adjacent to the flat overlap portion along the extending direction of the straight wire portion with respect to the wire portion that is the counterpart of the entanglement or overlap of the straight wire portion, the end regions on both sides in the axial direction of the stent have more of the wavy overlap portions than the flat overlap portions, and in the intermediate region between these end regions, the flat overlap portions are more than the wavy overlap portions. A stent characterized by this.

2. The stent according to claim 1, characterized in that most of the overlapping nodes in the end regions are the wavy overlap portions, and most of the overlapping nodes in the intermediate region are the flat overlap portions.

3. The stent according to claim 1 or 2, characterized in that the length of the intermediate region along the axial direction is greater than the length of the end regions.

4. The stent according to any one of claims 1 to 3, characterized in that the number of arrangements in the axial direction of the nodes composed of the entanglement nodes and the overlapping nodes in the end regions is one or more and four or less.

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