Stent delivery system

Abstract

A stent delivery system 100 comprises: a stent 10 having, at a leading end thereof, a small-diameter part 12 with an outer diameter of 3 Fr or less and having, at a base end thereof, a large-diameter part 14 which has an inner diameter that allows an inner catheter 30 to be inserted and in the radial direction of which a fixation hole 16 is made; and a pusher catheter 20 to which is attached a filamentary body 50 having a nodular body 52. The filamentary body 50 and the nodular body 52 are inserted into the large-diameter part 14, and in a state with the nodular body 52 in a loose fit with the fixation hole 16, the inner catheter 30 is inserted into the pusher catheter 20 and the large-diameter part 14, and the inner catheter 30 maintains the loose fit between the nodular body 52 and the fixation hole 16.

Description

Stent Delivery System

[0001] The present invention relates to a catheter-based stent delivery system, and in particular to one that uses a tube stent (hereinafter sometimes simply referred to as a "stent") made of a plastic such as polyethylene or polyurethane.

[0002] Among the stents used in stent placement, tube stents are advanced through the body by being pushed by a pusher catheter along a guide wire or inner catheter inserted into the body. Conventionally, tube stents could only be pushed by a pusher catheter and could not be pulled back, so if the stent was positioned incorrectly, the stent had to be removed and then reinserted. Therefore, delivery systems that allow the stent to be pulled back have been developed.

[0003] The applicant of the present invention has developed a stent delivery system that can pull back the stent, has a simple structure, makes it difficult for the connection between the stent and the pusher catheter to be accidentally released, and makes it easy to release the connection when desired, and holds patent rights related to the publications listed below.

[0004] Patent No. 4913251

[0005] In the stent delivery system of Patent Document 1, the pusher catheter has a hole for attaching a filament to its end, and the stent has a hooking hole. The knobby member on the filament is loosely fitted into the hooking hole from inside the stent, and this loose fitting state is maintained by an inner catheter inserted inside the stent. Therefore, the connection between the stent and the pusher catheter is unlikely to be inadvertently released until the inner catheter is pulled out, and when the inner catheter is pulled out, the knobby member comes out of the hooking hole, and the connection between the stent and the pusher catheter is easily released.

[0006] By reducing the outer diameter of a stent, it becomes easier to advance it within the human body and the number of treatable sites can be increased. Therefore, in recent years, stents with smaller outer diameters have been developed. Stents with an outer diameter of less than 5 French (Fr) are considered ultrathin stents, and stents with an outer diameter of 3 French (Fr) or less, i.e., an outer diameter of 1 mm or less, have also appeared. However, a stent with a small outer diameter also has a small diameter of its internal communicating holes (hereinafter referred to as the "inner diameter"). In this case, although it is possible to pass a guidewire through the stent, it is not possible to pass an inner catheter between the inner diameter of the stent and the guidewire, which creates a problem in that the above-mentioned stent delivery system cannot be applied.

[0007] Therefore, an object of the present invention is to provide a stent delivery system that can pull back a stent even if it has a small outer diameter, that makes it difficult for the connection between the stent and the pusher catheter to be inadvertently released, and that makes it easy to release the connection when desired.

[0008] The present invention relates to a stent delivery system comprising a tube stent, a pusher catheter, and an inner catheter, wherein the tube stent comprises a small diameter section at the distal end side with an outer diameter of less than 5 Fr, a large diameter section at the proximal end side with an inner diameter allowing the inner catheter to be inserted, and a hooking hole provided radially in the large diameter section, the pusher catheter that can come into contact with an end face of the large diameter section comprises a hole provided radially and a filament having a knobby body that is attached using the hole, the filament and knobby body are inserted into the large diameter section, and the inner catheter is inserted into the pusher catheter and large diameter section with the knobby body loosely fitted into the hooking hole, and the inner catheter maintains a loose fit between the knobby body and the hooking hole, or a stent delivery system comprising a tube stent, a pusher catheter, and an inner catheter, The above problem was solved by a stent delivery system characterized in that the tube stent has a small diameter section on the tip side with an outer diameter of less than 5 Fr, a large diameter section on the base end side with an inner diameter that allows the inner catheter to be inserted, a hole provided radially in the large diameter section, and a filament having a knobby body that is attached using the hole, the pusher catheter that can contact the end face of the large diameter section has a hooking hole provided radially, the inner catheter is inserted into the pusher catheter and the large diameter section with the filament and knobby body loosely fitted into the hooking hole, and the inner catheter maintains a loose fit between the knobby body and the hooking hole.

[0009] According to the present invention, a stent having a small-diameter portion with an outer diameter of less than 5 Fr at its distal end has a large-diameter portion at its proximal end with an inner diameter large enough to allow insertion of an inner catheter, the large-diameter portion having a radially extending hooking hole. The pusher catheter has a filament having a knobby body, and the filament and the knobby body are inserted into the large-diameter portion, and the inner catheter is inserted into the pusher catheter and the large-diameter portion with the knobby body loosely fitted into the hooking hole, so that the inner catheter maintains the loose fit between the knobby body and the hooking hole. Therefore, even if the stent has a small-diameter portion of less than 5 Fr, the stent can be pulled back, and the connection between the stent and the pusher catheter is unlikely to be released accidentally, and the connection can be easily released when desired. This provides a stent delivery system.

[0010] The stent delivery system may also be configured such that a hooking hole is provided in the radial direction of the pusher catheter, and a knotted filament is attached to a hole provided in the radial direction of the large-diameter portion of the stent. With this configuration, after the stent is placed, the filament can be easily grasped with forceps or the like when removing the stent, making it easy to remove the stent.

[0011] According to the present invention, when a stent is placed in the body, the large diameter portion can function as a flap that hooks onto the placement site to prevent the stent from being inserted further than necessary. Furthermore, when removing the stent after placement, the large diameter portion can be easily grasped with forceps, etc., making it easy to remove the stent.

[0012] Furthermore, if the stent is configured to have a tapered section between the large diameter section and the small diameter section, which gradually reduces in diameter from the large diameter section to the small diameter section, when it is necessary to insert a guide wire into the inside of the placed stent, it is easier to insert the guide wire from the large diameter section through the tapered section into the small diameter section than in a small diameter stent that does not have a large diameter section.

[0013] Fig. 1 is a side view of a first embodiment of a stent delivery system of the present invention. Fig. 2 is an enlarged cross-sectional view of a main part of Fig. 1. Fig. 3 is a side view of a second embodiment of a stent delivery system of the present invention.

[0014] An embodiment of the present invention will be described below with reference to Figures 1 to 3. However, the present invention is not limited to this embodiment.

[0015] The stent delivery system 100 of the present invention shown in FIG. 1 includes a tube stent (stent) 10, a pusher catheter 20, an inner catheter 30, and a guidewire 40. The stent 10, the pusher catheter 20, and the inner catheter 30 are cylindrical. The stent 10 can be made of plastic such as polyethylene or polyurethane, the pusher catheter 20 can be made of a fluororesin such as PTFE (polytetrafluoroethylene), and the inner catheter 30 can be made of a fluororesin such as ETFE (ethylene-tetrafluoroethylene copolymer). The guidewire 40 is a wire made primarily of metal with a coating applied to its surface. The stent 10, the pusher catheter 20, the inner catheter 30, and the guidewire 40 are inserted into an endoscope (not shown) for use.

[0016] The stent 10 comprises a small diameter section 12 and a large diameter section 14. The small diameter section 12 is located at the distal end of the stent 10 and has an outer diameter of less than 5 Fr, preferably 3 Fr or less. The large diameter section 14 is located at the proximal end of the stent 10 and has an inner diameter large enough to allow insertion of an inner catheter 30. To accommodate a typical inner catheter, the large diameter section 14 has an outer diameter of 6 Fr or more. However, if a smaller-diameter inner catheter is developed in the future, the large diameter section 14 may have an inner diameter large enough to allow insertion of the inner catheter. The dimensions and shapes of the small diameter section 12 and the large diameter section 14 are not limited to those shown in the drawings and may be any shape, such as a curved shape or a pigtail shape.

[0017] The stent 10 may have a tapered section 13 between the large diameter section 14 and the small diameter section 12, the diameter of which gradually decreases from the large diameter section 14 to the small diameter section 12, or may have a distal tapered section 15, the diameter of which gradually decreases from the small diameter section 12 to the distal side. A stent 10 having such a shape can be formed by subjecting a cylinder having the outer diameter of the large diameter section 14 to thermal processing or stretching, or by welding a cylinder having the outer diameter of the small diameter section 12, a cylinder having the outer diameter of the large diameter section 14, and the hollow tapered section 13 together.

[0018] The inner catheter 30 is inserted into the pusher catheter 20 so as to penetrate the interior of the pusher catheter 20, and is inserted into the large diameter portion 14 of the stent 10. The pusher catheter 20 is formed with an outer diameter that allows the distal end face to come into contact with the proximal end face of the large diameter portion 14 of the stent 10. The guide wire 40 is inserted through the inner catheter 30 and the stent 10 so as to penetrate the interior of the inner catheter 30 and the stent 10.

[0019] As shown in Figure 2, the large diameter portion 14 of the stent 10 is provided with a locking hole 16 extending radially therethrough. The locking hole 16 is provided with a size sufficient to allow a knobby body 52, described later, to fit loosely therethrough. Meanwhile, the pusher catheter 20 is provided with a hole 22 extending radially therethrough. The hole 22 is provided with a size sufficient to allow a filament 50, described later, to be inserted therethrough, and is preferably provided on the distal end side of the pusher catheter 20 to prevent the filament 50 from becoming longer than necessary.

[0020] A filament 50 is passed through the hole 22. Although not shown in the drawings, the filament 50 may be attached to the pusher catheter 20 by passing the filament 50 through the hole 22, tying a knot, and securing it with a knot. The filament 50 also has a knob 52. The knob 52 may be formed by tying the filament 50, or may be provided by welding a sphere.

[0021] As shown in the figure, the filament 50 and knot 52 attached to the pusher catheter 20 are inserted into the large diameter portion 14 of the stent 10, and the inner catheter 30 is inserted into the pusher catheter 20 and the large diameter portion 14 of the stent 10 with the knot 52 loosely fitted into the hooking hole 16. This maintains the loose fit of the inner catheter 30 between the knot 52 and the hooking hole 16. For ease of explanation, the sizes of the large diameter portion 14 of the stent 10, the pusher catheter 20, the inner catheter 30, and the knot 52 are exaggerated in Figure 2.

[0022] Because the stent delivery system 100 has the above-described configuration, even if the stent 10 has a small-diameter portion 12 with an outer diameter of less than 5 Fr, the stent 10 can be pulled back by pulling the pusher catheter 20 when placing the stent 10 in the body. Furthermore, since the inner catheter 30 maintains a loose fit between the knobby body 52 and the locking hole 16, the connection between the stent 10 and the pusher catheter 20 is unlikely to be inadvertently released. Furthermore, when it is desired to release the connection between the stent 10 and the pusher catheter 20, the inner catheter 30 is pulled out, causing the knobby body 52 to move into the large-diameter portion 14 of the stent 10, thereby releasing the connection between the stent 10 and the pusher catheter 20. Therefore, a stent delivery system in which the connection between the stent 10 and the pusher catheter 20 can be easily released can be provided.

[0023] Furthermore, when the stent 10 is placed in the body, the large diameter portion 14 can function as a so-called flap that latches onto the placement portion to prevent the stent 10 from being inserted further into the placement portion than necessary. Furthermore, when the stent 10 is to be removed after placement, the large diameter portion 14 can be easily grasped with forceps or the like, facilitating removal of the stent 10. Furthermore, if a tapered portion 13 that gradually decreases in diameter from the large diameter portion 14 to the small diameter portion 12 is provided between the large diameter portion 14 and the small diameter portion 12, as in the stent delivery system 100, when it is necessary to insert a guidewire 40 into the placed stent 10, it is easier to insert the guidewire 50 from the large diameter portion 14 through the tapered portion 13 into the small diameter portion 12 than in a small diameter stent that does not have the large diameter portion 14.

[0024] Also, as shown in the drawings, the filament 50 may be configured to have an extension 54 that extends beyond the hooking hole 16 when viewed from the pusher catheter 20. With this configuration, the filament 50 and the extension 54 are sandwiched between the tube stent 10 and the inner catheter 30 in front of and behind the hooking hole 16, preventing the knot 52 from completely protruding outside the stent 10. Furthermore, when the inner catheter 30 is pulled out, the knot 52 naturally attempts to return to the inside of the stent 10, allowing the connection between the stent 10 and the pusher catheter 20 to be reliably and easily released.

[0025] Although not illustrated, the basic configuration is the same as that of the stent delivery system 100, and the hooking holes 16 may be provided in the radial direction of the pusher catheter 20, the holes 22 may be provided in the radial direction of the large diameter portion 14 of the stent 10, and the filament 50 having the knobby bodies 52 may be attached using the holes 22 in the large diameter portion 14. With this configuration, when removing the stent 10 after placement, the filament 50 can be easily grasped with forceps or the like, making it easy to remove the stent 10.

[0026] A stent 10a may have a configuration in which there is no tapered portion between the small diameter portion 12a and the large diameter portion 14a, as in the stent delivery system 100a in Fig. 3. Such a stent 10a is formed by welding a cylinder having the outer diameter of the small diameter portion 12a to a cylinder having the outer diameter of the large diameter portion 14a.

[0027] As described above, according to the present invention, it is possible to provide a stent delivery system that can pull back a stent even if it has a small outer diameter, that makes it difficult for the connection between the stent and the pusher catheter to be inadvertently released, and that makes it easy to release the connection when desired.

[0028] REFERENCE SIGNS LIST 10 Tube stent 12 Small diameter portion 13 Tapered portion 14 Large diameter portion 16 Hook-up hole 20 Pusher catheter 22 Hole 30 Inner catheter 50 Filament-like body 52 Knob-like body 100 Stent delivery system

Claims

1. A stent delivery system comprising a tube stent, a pusher catheter, and an inner catheter, wherein the tube stent has a small diameter section at its distal end with an outer diameter of less than 5 Fr, a large diameter section at its proximal end with an inner diameter allowing the inner catheter to be inserted, and a hooking hole provided radially in the large diameter section, the pusher catheter that can come into contact with the end face of the large diameter section has a hole provided radially and a filament having a knobby body that is attached using the hole, the filament and knobby body being inserted inside the large diameter section and with the knobby body loosely fitted into the hooking hole, the inner catheter being inserted into the pusher catheter and large diameter section, and the inner catheter maintaining a loose fit between the knobby body and the hooking hole.

2. A stent delivery system comprising a tube stent, a pusher catheter, and an inner catheter, wherein the tube stent has a small diameter section at its distal end with an outer diameter of 3 Fr or less, a large diameter section at its proximal end with an inner diameter allowing the inner catheter to be inserted, a hole formed radially in the large diameter section, and a filament having a knobby body that is attached using the hole, the pusher catheter that can contact the end face of the large diameter section has a hooking hole formed radially, the filament and knobby body are inserted into the pusher catheter, and with the knobby body loosely fitted in the hooking hole, the inner catheter is inserted into the pusher catheter and the large diameter section, and the inner catheter maintains a loose fit between the knobby body and the hooking hole.

3. A stent delivery system according to claim 1 or 2, comprising a tapered section between the large diameter section and the small diameter section, the diameter of which gradually decreases from the large diameter section to the small diameter section.

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