JP7702287B2 - Stents - Google Patents

Description

The present invention relates to a stent used to improve occluded or narrowed lesions, and in particular to a tubular stent woven in a diagonal lattice pattern.

For example, a treatment is known in which a lesion that is blocked or narrowed by colon cancer or the like is opened and a cylindrical stent is placed there to maintain the open state. This type of stent is, for example, cylindrical in shape, with two wires woven in a diagonal lattice pattern (see Patent Document 1, etc.). Diamond-shaped cells are formed by wire parts connecting four nodes arranged in a ring in the diagonal lattice. Some of the lattice points, i.e., nodes, of the diagonal lattice of the stent are entangled nodes where two wire parts are bent in an L-shape and entangled with each other. Other nodes are overlapping nodes where two wire parts extend straight and overlap inside and outside (in the radial direction of the stent), and in particular, they are undulating overlapping sections where they are overlapped in an undulating manner by passing them through the opposite sides of adjacent nodes.

Generally, after manufacture, the stent is narrowed radially and placed in the tip of a dedicated delivery catheter. This delivery catheter is brought to the treatment site. The surgeon then inserts the delivery catheter into the affected area of the patient, and the stent is released from the tip of the delivery catheter and deployed.

Patent No. 6420918

In the conventional braided stent, the entangled nodes strongly resist external forces such as tension, and friction is also effective in the wavy overlapping portions, thereby suppressing deformation of the diagonal lattice-like braided pattern and each cell. On the other hand, when the stent is contracted and narrowed in the radial direction, the entangled nodes and wavy overlapping portions arranged in the circumferential direction gather together to form localized bumps or bamboo knots. Therefore, when the stent is narrowed and inserted into the tip of the delivery catheter, resistance increases, making it difficult to smoothly insert the stent into the delivery catheter. During the procedure, release resistance also increases when the stent is released from the tip of the delivery catheter. In particular, when the delivery catheter is made thinner, it becomes difficult to insert and remove the stent from the delivery catheter.
In view of the above circumstances, an object of the present invention is to provide a stent that can be smoothly accommodated in a delivery catheter and smoothly released from the delivery catheter, and that can maintain the uniformity of the braided weave pattern and cells against external forces.

In order to solve the above problems, in one embodiment of the present invention, there is provided a cylindrical stent woven in a diagonal lattice pattern using one or more wires,
The wire includes an intertwining node and an overlapping node formed by two wire portions of the wire,
At the intertwining node, the two wire rod portions are bent and intertwined with each other,
In the overlapping node portion, the two wire rod portions extend straight and are overlapped with each other in the inner and outer directions of the stent, and the overlapping node portion includes a wavy overlapping portion and a flat overlapping portion,
In the wavy overlap portion, a passing position in the inner/outer direction of one wire rod portion constituting the wavy overlap portion with respect to the other wire rod portion is opposite to a passing position at a portion from a tangled node portion or an overlapping node portion adjacent to the one wire rod portion toward the wavy overlap portion,
In the flat overlap portion, a passing position in the inner/outer direction of one wire rod portion constituting the flat overlap portion with respect to the other wire rod portion is the same as a passing position at a location from a tangled node portion or an overlapping node portion adjacent to the one wire rod portion toward the flat overlap portion,
In the end regions on both sides of the stent in the axial direction, the wavy overlap portion is greater than the flat overlap portion,
The intermediate region between the end regions has more of the flat overlap portion than the wavy overlap portion.

According to this stent, the frictional resistance between the two wire parts in the wavy overlapping portion is relatively large, and the frictional resistance between the two wire parts in the flat overlapping portion is relatively small. Therefore, in addition to the strong resistance of the entangled nodes to external forces such as tension, the friction is also effective in the wavy overlapping portions at both end regions, so that the deformation suppression effect extends to the entire area of the stent. This maintains the uniformity of the knitted pattern and cells of the entire stent. On the other hand, especially in the middle region of the stent, the frictional resistance of the flat overlapping portions is small, so that the stent is more likely to expand and contract, and when the stent is narrowed, even if the flat overlapping portions gather together, they do not form localized lumps or bamboo knots. As a result, the narrowed stent can be smoothly accommodated in the delivery catheter. In addition, the stent can be smoothly released from the delivery catheter and deployed.

Preferably, the majority of the overlapping nodes in the end regions are the wavy overlapping portions, and the majority of the overlapping nodes in the intermediate regions are the flat overlapping portions. Here, the majority refers to preferably 80% or more, and more preferably 90% or more of the overlapping nodes in each region.

Preferably, the length of the intermediate region along the axial direction is greater than the length of the end region. This allows the area in which the unevenness caused when the stent is narrowed to be reduced to be wider, allowing the stent to be inserted and removed reliably and smoothly from the delivery catheter.

It is preferable that the number of nodes in the end region, consisting of the entangled nodes and the overlapping nodes, arranged in the axial direction is between 1 and 4. This ensures that the end region is secured and deformation suppression is achieved regardless of the overall length of the stent, and also makes it easier to insert and remove the stent from a delivery catheter by making the middle region as long as possible.

The stent of the present invention can be smoothly inserted into and removed from a delivery catheter, and deformation of the knitted pattern and cells due to external forces such as tension can be suppressed.

FIG. 1 is a side cross-sectional view of the distal end of a delivery system housing a stent according to one embodiment of the present invention. FIG. 2 is a side view of the stent in its deployed natural state. FIG. 3 is an enlarged side view of circle III in FIG. FIG. 4 is a cross-sectional view taken along line VI-VI in FIG. FIG. 5 is an enlarged side view of the circle V in FIG. FIG. 6 is a cross-sectional view taken along line VI-VI in FIG.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.
FIG. 1(a) shows a delivery system 1. The delivery system 1 is used for treating a blocked or narrowed lesion such as colon 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 into the outer tube 5 so as to be movable in the axial direction. A cylindrical stent 3 woven in a diagonal lattice pattern is narrowed in the radial direction 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. As a result, the stent 3 is housed in the tip of the delivery catheter 2 while being sandwiched between the inner shaft 4 and the outer tube 5. In this state, the tip of the delivery catheter 2 is inserted into the lesion that has been opened in advance. Then, as shown in FIG. 1(b), the stent 3 is released from the delivery catheter 2 and placed in the lesion in a state where it is elastically expanded and deployed. This maintains the lesion in an open state.

As shown in FIG. 2, the stent 3 is composed of two (or more) wires 10. The material of the wires 10 is preferably a spring metal, and more preferably a shape-memory alloy having spring properties, such as a nickel-titanium alloy.

The stent 3 is constructed by weaving these wires 10 into a cylindrical shape with a diagonal lattice pattern. At each node 3p that constitutes a lattice point of the diagonal lattice of the stent 3, two portions of the wire 10 (hereinafter referred to as "wire portions 10a, 10b, 10c, 10d, 10e, 10f...") intersect with each other. Diamond-shaped cells 3q are formed by the wire portions that connect the four nodes 3p arranged in a ring. Both ends of each wire 10 are connected by connecting members 15. This makes each wire 10 into a closed ring.

The nodes 3p formed by the two wire parts are broadly divided into entangled nodes 11 and overlapping nodes 12. As shown in FIG. 3, in the entangled nodes 11, the two wire parts 10a and 10b are bent into an L-shape and entangled with each other. One wire part 10a wraps around the other wire part 10b from the outside to the inside or from the inside to the outside in the radial direction (inside-out direction) of the stent 3. Each entangled node 11 is formed by two wire parts 10a and 10b of the same wire 10, but the entangled nodes may be formed by intersecting parts (wire parts) of two different wires so that they are entangled with each other.

As shown in Figures 3 and 5, in the overlapping node 12, two wire portions extend straight without bending and are overlapped inward and outward. The overlapping node 12 may be formed by two wire portions of the same wire overlapping inward and outward, or may be formed by wire portions (portions) of two different wires overlapping inward and outward.

More specifically, the stent 3 includes an undulating overlapping portion 12A and a flat overlapping portion 12B as overlapping nodes 12. As shown in Fig. 3, in the undulating overlapping portion 12A, the position of one wire portion constituting the undulating overlapping portion 12A in the inward/outward direction relative to the other wire portion is opposite to the position of the entangled node 11 or overlapping node 12 adjacent to the one wire portion toward the undulating overlapping portion 12A. In short, as shown in Figures 3 and 4, at the node 3p1 adjacent to the undulating overlap portion 12A, the wire portion 10c extending from the inside of the other wire portion 10e (the far side of the paper in Figure 3, the lower side in Figure 4) toward the undulating overlap portion 12A passes through the outside of the other wire portion 10d (the near side of the paper in Figure 3) in the undulating overlap portion 12A. At the node 3p2 adjacent to the undulating overlap portion 12A, the wire portion 10d extending from the outside of the other wire portion 10f toward the undulating overlap portion 12A passes through the inside of the other wire portion 10c in the undulating overlap portion 12A.

5, in the flat overlap portion 12B, the passing position of one wire portion constituting the flat overlap portion 12B in the inward/outward direction relative to the other wire portion is the same as the passing position at the point from the entanglement node 11 or overlap node 12 adjacent to the one wire portion toward the flat overlap portion 12B. In short, as shown in Figures 5 and 6, in the node 3p3 adjacent to the flat overlap portion 12B, the wire portion 10g extending from the inside of the other wire portion 10i (the far side of the page in Figure 5, the lower side in Figure 6) toward the flat overlap portion 12B is also passed through the inside of the other wire portion 10h in the flat overlap portion 12B. At the node 3p4 adjacent to the flat overlapping portion 12B, the wire portion 10h extending from the outside of the other wire portion 10j (the front side of the paper in FIG. 5) toward the flat overlapping portion 12B is also passed through the outside of the other wire portion 10g in the flat overlapping portion 12B.

The node adjacent to the overlapping node 12 may be a tangled node 11 or another overlapping node 12. The flat overlapping portion 12B may have a threading position of at least one wire portion constituting it that is the same as the threading position at a location from at least one adjacent tangled node 11 or overlapping node 12 toward the flat overlapping portion 12B.

As shown in FIG. 2, in the axial intermediate region 3C of the stent 3, the flat overlapping portion 12B occupies a larger proportion of the overlapping joint portion 12 than in the axial end regions 3A, 3B of the stent 3 on both sides.
Preferably, in the intermediate region 3C, the flat overlap portion 12B accounts for a larger proportion of the overlap node portion 12 than the undulating overlap portion 12A. In the end regions 3A and 3B, the undulating overlap portion 12A accounts for a larger proportion of the overlap node portion 12 than the flat overlap portion 12B.
More preferably, the majority of the overlap nodes 12 in the intermediate region 3C are flat overlap portions 12B, whereas the majority of the overlap nodes 12 in the end regions 3A and 3B are wavy overlap portions 12A.
The number of nodes in the axial direction in each of the end regions 3A, 3B (the number of node portions 3p arranged in the axial direction) is preferably one or more and four or less.

According to the stent 3, the entangled nodes 11 strongly resist external forces such as tension. In addition, the frictional resistance between the two wire portions in the wavy overlapping portion 12A is greater than that in the flat overlapping portion 12B. Therefore, in addition to the resistance of the entangled nodes 11, friction also works in the wavy overlapping portion 12A, which is distributed in large numbers in the end regions 3A and 3B, so that a deformation suppressing force works in the end regions 3A and 3B on both sides, and the deformation suppressing force is propagated from each end region 3A and 3B to the central region 3C, so that the deformation suppressing effect is applied to the entire area of the stent 3. This maintains the uniformity of the knitted pattern of the entire stent 3, and the size and shape of the cells 3q are maintained uniform. Incidentally, if the deformation suppressing force is only manifested in one end region, the deformation suppressing effect is unlikely 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 suppressing force is only exerted in the central portion of the stent, the deformation suppressing effect is unlikely to extend to 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 middle region 3C of the stent 3, the distribution ratio of the flat overlapping portions 12B is high and the frictional resistance is small, so that the stent 3 is easily expanded and contracted. Moreover, when the stent 3 is contracted and narrowed in the radial direction, even if the flat overlapping portions 12B gather together, they do not form localized lumps or bamboo knots. As a result, the narrowed stent 3 can be smoothly accommodated in the delivery catheter 2. Moreover, the stent 3 can be smoothly released from the delivery catheter 2.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, the number of wires 10 is not limited to two, but may be one, or three or more.

The present invention can be applied to, for example, treatment devices for occluded or narrowed lesions.

1 Delivery system 2 Delivery catheter 3 Stent 3A, 3B End region 3C Middle region 3p Node portion 3q Cell 10 Wire
10a to 10j Wire rod portion 11 Tangled node portion 12 Overlapped node portion 12A Wavy overlap portion 12B Flat overlap portion

Claims (4)

A cylindrical stent woven in a diagonal lattice pattern using one or more wires,
The wire includes an intertwining node and an overlapping node formed by two wire portions of the wire,
At the intertwining node, the two wire rod portions are bent and intertwined with each other,
In the overlapping node portion, the two wire rod portions extend straight and are overlapped with each other in the inner and outer directions of the stent, and the overlapping node portion includes a wavy overlapping portion and a flat overlapping portion,
In the wavy overlap portion, a passing position in the inner/outer direction of one straight wire rod portion constituting the wavy overlap portion with respect to the other wire rod portion is opposite to a passing position in the inner/outer direction of the straight wire rod portion with respect to a tangled or overlapped counterpart wire rod portion at a tangled node portion or overlapped node portion adjacent to the wavy overlap portion along an extension direction of the straight wire rod portion ,
In the flat overlapping portion, a passing position in the inner/outer direction of one straight wire rod portion constituting the flat overlapping portion with respect to the other wire rod portion is the same as a passing position in the inner/outer direction of a tangled or overlapping counterpart wire rod portion of the straight wire rod portion at a tangled node portion or an overlapping node portion adjacent to the flat overlapping portion along an extending direction of the straight wire rod portion ,
In the end regions on both sides of the stent in the axial direction, the wavy overlap portion is greater than the flat overlap portion,
A stent comprising an intermediate region between said end regions, said flat overlap portion being greater than said undulating overlap portion. The stent of claim 1, characterized in that the majority of the overlap nodes in the end regions are wavy overlaps, and the majority of the overlap nodes in the middle region are flat overlaps. 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. The stent according to any one of claims 1 to 3, characterized in that the number of nodes in the axial direction, consisting of the entangled nodes and the overlapping nodes, in the end region is 1 to 4.

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