Stent delivery system

A stent delivery system includes a guide catheter, a tubular stent into which the guide catheter can be inserted, and a tubular pusher catheter into which the guide catheter can be inserted and disposed nearer to a proximal end side than the stent. The pusher catheter includes a diameter expansion-suppressing part provided at a distal end part and having the same inner diameter as the stent and an intermediate part provided at a proximal end side of the diameter expansion-suppressing part and having a bending stiffness less than that of the diameter expansion-suppressing part. When the stent is pushed toward a distal end side by pushing the intermediate part of the pusher catheter toward the distal end side and bringing a distal end part of the diameter expansion-suppressing part into contact with a proximal end part of the stent, an inner diameter of the pusher catheter is prevented from expanding.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a stent delivery system for placing a stent in a bile duct or the like.

Description of Related Art

When a stenosis or occlusion occurs in a hollow organ of a digestive system, a respiratory system, a urinary system, a reproductive system, or the like, a stent is used in a stenosis or occluded portion to recover an inherently provided drainage function, or to secure a drainage feature. When a stent is placed at a desired position within a bile duct or the like, an operation is performed using a stent delivery system (hereinafter simply referred to as a delivery system. Hereinafter, the delivery system is assumed to include a stent). As this type of delivery system, for example, a system disclosed in Japanese Unexamined Patent Application, First Publication No. 2000-152985 is known.

The delivery system includes a guide catheter, a stent into which the guide catheter is inserted, and a pusher catheter into which the guide catheter is inserted and which is positioned closer to a hand side than the stent.

The delivery system is used as follows. A guide wire is introduced into a bile duct through a channel of an endoscope, and a distal end of the guide wire is inserted to a position beyond a stenosis portion. Next, the guide wire is covered with the guide catheter from the hand side, the guide catheter is pushed using the guide wire as a guide, and a distal end part of the guide catheter is inserted to a position beyond the stenosis portion of the bile duct.

Next, the stent is pushed by the pusher catheter, the stent is introduced into the bile duct using the guide catheter as the guide, and the stent is disposed at a position of the stenosis portion. Only the guide catheter is pulled back to the hand side in a state in which the stent is supported by touching the pusher catheter with the stent and the stent and the pusher catheter are fixed so as not to move. Thereafter, the pusher catheter is pulled back to the hand side so that the stent is placed and maintained within the stenosis portion.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention, a stent delivery system includes: a guide catheter capable of being inserted into a channel of an endoscope; a stent formed in a tube shape and into which the guide catheter is capable of being inserted; and a pusher catheter formed in a tube shape and into which the guide catheter is capable of being inserted, the pusher catheter being disposed nearer to a proximal end side than the stent. The pusher catheter includes: a diameter expansion-suppressing part provided at a distal end part of the pusher catheter and having an inner diameter the same as an inner diameter of the stent; and an intermediate part provided at a proximal end side of the diameter expansion-suppressing part and having a bending stiffness less than a bending stiffness of the diameter expansion-suppressing part. When the stent is pushed toward a distal end side by pushing the intermediate part of the pusher catheter toward the distal end side and causing a distal end part of the diameter expansion-suppressing part to come into contact with a proximal end part of the stent, the diameter expansion-suppressing part prevents an inner diameter of the distal end part of the pusher catheter from expanding.

According to a second aspect of the present invention, in the stent delivery system according to the first aspect, a thickness of a tube wall of the stent in a radial direction may be the same as a thickness of a tube wall of the pusher catheter in the radial direction. A difference between the inner diameter of the stent and an outer diameter of the guide catheter may be less than or equal to 8% of the inner diameter of the stent.

According to a third aspect of the present invention, in the stent delivery system according to the second aspect, the diameter expansion-suppressing part and the intermediate part may be made of the same type of material to be mixed at different mixing ratios.

According to a fourth aspect of the present invention, in the stent delivery system according to the third aspect, the pusher catheter may be formed of a monolayer tube. The stent may be formed of a multilayer tube obtained by stacking different materials in the radial direction.

According to a fifth aspect of the present invention, in the stent delivery system according to the first aspect, the bending stiffness of the diameter expansion-suppressing part may be greater than a bending stiffness of the stent.

According to a sixth aspect of the present invention, in the stent delivery system according to the fifth aspect, the bending stiffness of the intermediate part may be less than the bending stiffness of the stent.

According to a seventh aspect of the present invention, in the stent delivery system according to the sixth aspect, the bending stiffness of the diameter expansion-suppressing part may be less than or equal to 200% of the bending stiffness of the stent. The bending stiffness of the intermediate part may be greater than or equal to 50% of the bending stiffness of the stent.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, an embodiment of a delivery system according to the present invention will be described with reference toFIGS. 1 to 11.

Hereinafter, first, an endoscope used together with the present delivery system will be described. As illustrated inFIG. 1, an endoscope100is a so-called flexible side view type endoscope and includes an elongated insertion part110and a manipulation part120provided at a proximal end part of the insertion part110.

The insertion part110includes a distal end rigid part111provided at a distal end part, a bent part112attached to a proximal end side of the distal end rigid part111and capable of being operated to be bent, and a flexible tube part113attached to the proximal end side of the bent part112. A distal end part of a light guide115and an imaging unit116having a charge-coupled device (CCD) (not illustrated) are provided on a side surface of the distal end rigid part111in an externally exposed state. In the insertion part110, a channel117for inserting an endoscopic treatment tool such as a delivery system1is formed. The distal end part of the channel117is opened in the above-mentioned side surface of the distal end rigid part111. The proximal end part of the channel117extends to the manipulation part120. A raising base (not illustrated) is provided at a part corresponding to the distal end rigid part111of the channel117. The proximal end part of the raising base is supported to be rotatable on the distal end rigid part111. A raising base manipulation wire (not illustrated) fixed to the distal end part of the raising base is inserted into the insertion part110and extends to the proximal end side.

Although not illustrated, a plurality of bending pieces arranged side by side in a longitudinal direction of the insertion part110and mutually connected to be swingable are embedded in the bent part112. A distal end part of a bending piece manipulation wire is fixed to a bending piece arranged at a most distal end side among the bending pieces. The bending piece manipulation wire extends to the proximal end side through the inside of the insertion part110.

A forceps port122is provided at a distal end side of a manipulation part main body121constituting the manipulation part120. The proximal end part of the channel117is opened in the forceps port122. A lever (not illustrated) for manipulating the above-mentioned raising base manipulation wire, a knob123for manipulating the bending piece manipulation wire, and a switch124for manipulating a light source (not illustrated), a monitor (not illustrated), the above-mentioned imaging unit116, or the like are provided on the proximal end side of the manipulation part main body121. The bent part112can be bent in a desired direction by manipulating the knob123.

An endoscope adapter130is installed to be detachable at the manipulation part120. The endoscope adapter130includes a rod-shaped adapter main body131, a cylindrical treatment tool-fixing part132engaged with the delivery system1and disposed at one end part of the adapter main body131, and an endoscope-fixing part133disposed at the other end part of the adapter main body131substantially molded in a semi-cylindrical shape and having a segmented portion.

Next, the delivery system1according to the present embodiment will be described. As illustrated inFIGS. 2 and 3, the delivery system1includes a guide catheter10capable of being inserted into the channel117of the endoscope100, a stent20formed in a tube shape and into which the guide catheter10can be inserted, and a pusher catheter30formed in a tube shape, into which the guide catheter10can be inserted, and arranged closer to the proximal end side than the stent20.

Here, a cantilever stiffness test for measuring bending stiffness will be described when components of the delivery system1are described. The guide catheter10, the stent20, and the pusher catheter30mentioned above are used as a tubular sample S1illustrated inFIG. 4. In a state in which a distal end side of the sample S1protrudes by 5 mm or more, an outer peripheral surface of a proximal end side of the sample S1is grasped and supported by a clamp R1. The sample S1is arranged to be parallel to a horizontal plane. At this time, a cylindrical core body R2is inserted into a conduit of the sample S1in a range in which the sample S1is grasped by the clamp R1in a longitudinal direction of the sample S1. An outer diameter of the core body R2is substantially the same as an inner diameter of the conduit of the sample S1.

InFIG. 5, an attachment R3used to exert a load on the sample S1is illustrated. The attachment R3is formed in a plate shape having a width of 20 mm and a thickness of 5 mm. A contact surface R4of the attachment R3in contact with the sample S1is formed in a curved shape having a curvature radius of 2.5 mm so that a bending load for the sample S1is not concentrated on one point.

As illustrated inFIG. 4, a position of the outer peripheral surface of the sample S1corresponding to a distal end surface of the clamp R1is designated as a fulcrum S2, and the attachment R3is set such that the contact surface R4of the attachment R3abuts a force point S3, which is a position of the outer peripheral surface separated 5 mm along a horizontal plane from the fulcrum S2, from above. A measurement device (not illustrated) depresses the attachment R35 mm in a vertically downward direction at a speed of 10 mm/minute while concurrently measuring a deflection when the attachment R3is depressed and a reaction force that the attachment R3receives from the sample S1. A maximum reaction force received while the attachment R3is depressed 5 mm is measured, and the measured maximum reaction force is the bending stiffness of the sample S1. The bending stiffness in the present description is measured by the cantilever stiffness test.

Also, a bending stiffness ratio is defined by the following Formula (1).
((Bending stiffness of diameter expansion-suppressing part or intermediate part)/Bending stiffness of stent)×100(%)  (1)

Next, components of the delivery system1will be described. As the guide catheter10, a guide catheter having a well-known configuration formed of a tubular resin having biocompatibility such as polypropylene or polyethylene can be used.

The stent20may be formed of a multilayer tube in which an inside layer21and an outside layer22formed of resin materials in a tube shape are radially stacked.FIG. 3illustrates the stent20having a two-layer structure, wherein the outside layer22covers an outer peripheral surface of the inside layer21. The inside layer21and the outside layer22are formed of different materials. For example, it is possible to form the inside layer21of perfluoroalkoxy alkane (PFA) and form the outside layer22of a polyurethane-based elastomer resin. Thereby, flexibility can be imparted to the stent20having low invasiveness while the stent20is placed, and good sliding properties (delivery system operability) can be imparted to the stent20and the guide catheter10. Flaps23and24illustrated inFIGS. 2 and 3are formed in the distal end part and the proximal end part of the stent20, respectively. The flap23is formed to open outward in a radial direction toward the proximal end side. The flap24is formed to open outward in the radial direction toward the distal end side. In this example, the flaps23and24are formed by cutting and raising the outside layer22and the inside layer21.

Also, the stent20may be formed of a monolayer tube made of a resin material, and a reinforcing layer such as a blade layer or a coil layer may be disposed within the monolayer tube or the multilayer tube. The stent20is arranged to be able to slide on the distal end side of the guide catheter10.

The pusher catheter30includes a diameter expansion-suppressing part31provided at the distal end part of the pusher catheter30, an intermediate part32provided at a proximal end side of the diameter expansion-suppressing part31, and a proximal-end-side rigid part33provided at a proximal end side of the intermediate part32. That is, the distal end part of the pusher catheter30is constituted of the diameter expansion-suppressing part31, a proximal end side closer than the diameter expansion-suppressing part31in the pusher catheter30is constituted of the intermediate part32, and a proximal end side closer than the intermediate part32in the pusher catheter30is constituted of a proximal-end-side rigid part33. Each of the diameter expansion-suppressing part31, the intermediate part32, and the proximal-end-side rigid part33is formed of a monolayer tube in a tube shape. In this example, inner diameters of the diameter expansion-suppressing part31, the intermediate part32, and the proximal-end-side rigid part33are the same as one another, and outer diameters of the diameter expansion-suppressing part31, the intermediate part32, and the proximal-end-side rigid part33are the same as one another.

The inner diameter of the diameter expansion-suppressing part31and the inner diameter of the stent20are substantially the same (they can also be the same). A wall thickness of the stent20and a wall thickness of the pusher catheter30are substantially the same (they can also be the same). That is, the stent20, the diameter expansion-suppressing part31, the intermediate part32, and the proximal-end-side rigid part33have substantially the same wall thickness. Here, in the present description, the “wall thickness” is a dimension in a radial direction of a tube wall in a structure formed in a tube shape. A length of the diameter expansion-suppressing part31in an axial direction is appropriately set in a range in which insertion into the channel117is possible (it is not caught (not stacked) in the channel117) when the bent part112of the endoscope100is bent. When the length of the diameter expansion-suppressing part31is long, it is difficult to push the delivery system1into the channel117formed in the bent part112which is bent. It is preferable that the length of the diameter expansion-suppressing part31be less than 10 mm, and it is more preferable that the length of the diameter expansion-suppressing part31be about 2 mm. A bending stiffness of the intermediate part32is less than a bending stiffness of the diameter expansion-suppressing part31.

A method of configuring the diameter expansion-suppressing part31may be any method in which processing such as physical processing or chemical processing is enabled in a predetermined dimension. Physical processing includes, for example, a method of forming the diameter expansion-suppressing part31and the intermediate part32by a junction of the tube (a welding), disposing a metallic pipe within the diameter expansion-suppressing part31, or performing insert molding to configure the diameter expansion-suppressing part31. Alternatively, chemical processing includes a method of expressing a molecular cross-linked structure of a thermoplastic resin by electron beam processing.

When the diameter expansion-suppressing part31is formed in the junction of the tube, it is preferable to mix a filler with the resin material and mold the filler mixed with the resin material as a compound (resin kneading) material. As the diameter expansion-suppressing part31is configured as described above, because it is easy to adjust mechanical properties such as surface hardness, bending stiffness, and extensibility to appropriate values, it is possible to manufacture the diameter expansion-suppressing part31suitable for a use environment of the delivery system1.

The resin material to be used in the diameter expansion-suppressing part31is represented by the following thermoplastic resin. However, any thermoplastic resin may be used as long as a desired mechanical property is provided.

General purpose resins such as olefin-based resins such as polypropylene and polyethylene, a copolymer resin thereof, a polyester-based resin (polyethylene terephthalate (PET) or the like), and polyvinyl alcohol (PVA)

The filler is not limited to the resin materials and is mixed with the resin material to adjust mechanical properties or chemical properties of the diameter expansion-suppressing part31. Also, the filler may not be mixed with the resin material. Organic fillers among the fillers can include an ultraviolet (UV) inhibitor, a cellulose nanofiber, etc. Inorganic fillers among the fillers can include metals (carbon black, tungsten, etc.), metal compounds (calcium carbonate, barium sulfate, diamond-like carbon (DLC), etc.), metal oxides (titanium oxide, silica, or the like), and minerals (talc, clay, etc.).

Mechanical properties are imparted to the diameter expansion-suppressing part31by, for example, making a tube configuration having a multilayer tube in which reinforcing layers such as a coil and a blade are arranged as means having mechanical properties such as rigidity. Also, in order to secure bonding strength between the diameter expansion-suppressing part31and the intermediate part32, it is desirable to further increase an amount of a welded resin, and a monolayer tube in which only a resin material serving as a component is preferably used as the diameter expansion-suppressing part31or the intermediate part32.

The pusher catheter30may be configured by manufacturing and welding a set of the diameter expansion-suppressing part31and the intermediate part32and a set of the intermediate part32and the proximal-end-side rigid part33with the same material. In this case, because the types of materials mixed in the diameter expansion-suppressing part31, the proximal-end-side rigid part33, and the intermediate part32are the same, the compatibility during welding is good and the bonding strength is improved. When the diameter expansion-suppressing part31, the intermediate part32, and the proximal-end-side rigid part33are not manufactured and configured with the same type of material as described above, it is necessary to perform surface modification, binder arrangement, or the like to achieve required bonding strength. A manufacturing cost of the pusher catheter may increase by increasing the number of processing steps. By configuring the pusher catheter30using a tube junction, processing is easily performed in predetermined dimensions without requiring large-scale equipment (an initial investment) when the pusher catheter30is manufactured.

It is preferable that the types of mixed materials of the diameter expansion-suppressing part31and the intermediate part32be the same as each other and mixing ratios of the materials be different from each other. Thereby, the bonding strength during weld bonding is maintained and an adjustment to a predetermined bending stiffness is easy. For example, a relatively soft elastomer resin and a relatively rigid thermoplastic resin are used as the above-mentioned resin material so that the bending stiffness of the intermediate part32is less than the bending stiffness of the diameter expansion-suppressing part31. The elastomer resin and the thermoplastic resin are mixed in the diameter expansion-suppressing part31and the intermediate part32, and the mixing ratio of the thermoplastic resin in the diameter expansion-suppressing part31is greater than the mixing ratio of the thermoplastic resin in the intermediate part32. The proximal-end-side rigid part33is formed of the same material as that of the diameter expansion-suppressing part31. That is, the bending stiffness of the proximal-end-side rigid part33is equal to the bending stiffness of the diameter expansion-suppressing part31.

As illustrated inFIG. 6, a pusher cap41is attached to the proximal end part of the proximal-end-side rigid part33of the pusher catheter30. A male screw part41ais formed at the proximal end part of the pusher cap41. A hook43with an elastically deformable C shape is attached to the pusher cap41. In the hook43, a slanting distal end side is opened in a side view. When the hook43is attached to the treatment tool-fixing part132of the endoscope adapter130, the hook43slides around the treatment tool-fixing part132. A cap42is attached to the proximal end part of the guide catheter10. In a distal end part of the cap42, a female screw part42awhich is screwed onto the male screw part41ais formed.

Next, an operation of the delivery system1configured as described above will be described as an example of when the stent20is placed within a bile duct.

When the light source is operated by manipulating the switch124of the manipulation part120, illuminating light emitted from the light source is guided by the light guide115and illuminates a periphery of the distal end rigid part111of the insertion part110. An image of the periphery of the distal end rigid part111of the insertion part110captured by the imaging unit116is displayed on a monitor. The user inserts the insertion part110of the endoscope100into a body cavity of a patient through a natural orifice of a mouth or the like while viewing the image displayed on the monitor. At this time, the knob123is optionally manipulated to bend the bent part112.

As illustrated inFIG. 7, the distal end part of the insertion part110moves into the vicinity of a duodenal papilla P2through a duodenum P1. An opening of the distal end part of the channel117opposes the duodenal papilla P2. The guide wire140is inserted into the forceps port122of the endoscope100, and the guide wire140protruding from the distal end part of the channel117is inserted into a stenosis portion P4of a bile duct P3. At this time, the raising base is appropriately manipulated to adjust the direction of the guide wire140protruding from the opening of the distal end part of the channel117.

Next, as illustrated inFIG. 1, the endoscope-fixing part133of the endoscope adapter130is mounted at a predetermined position of the manipulation part120of the endoscope100. The stent20on the distal end side of the guide catheter10and the pusher catheter30on the proximal end side thereof are arranged to be able to slide in an outer peripheral part of the guide catheter10. The distal end part of the guide catheter10is inserted along the proximal end side end part of the guide wire140protruding from the forceps port122. Parts of the distal end sides of the stent20and the pusher catheter30are inserted into the channel117.

In the vicinity of the forceps port122, the guide catheter10and the pusher catheter30are folded back in the middle, and the hook43is attached to the treatment tool-fixing part132of the endoscope adapter130. While the hook43rotates on the treatment tool-fixing part132, the cap42opposes the forceps port122and adjustment is performed so that the guide catheter10and the pusher catheter30are substantially parallel to the guide wire140protruding from the cap42.

In this state, the proximal-end-side rigid part33of the pusher catheter30and the guide wire140are grasped together and move in a direction of an arrow A1in the drawing. At this time, a length in which the guide catheter10and the pusher catheter30are inserted into the channel117is the same as a length in which the guide wire140is extracted from the cap42. Accordingly, by repeating this operation, as illustrated inFIG. 7, the guide catheter10and the pusher catheter30are inserted into the channel117in a state in which a distal end position of the guide wire140is constantly maintained, and a distal end of the guide catheter10is inserted to a desired position. By causing a force to act on the proximal-end-side rigid part33, the force is effectively delivered to the proximal end side of the pusher catheter30.

Next, as illustrated inFIG. 8, the cap42rotates with respect to the pusher cap41, and the cap42is removed from the pusher cap41. As illustrated inFIG. 9, the guide catheter10is extracted from the pusher cap41while the cap42is grasped, and the guide catheter10protruding from the pusher cap41and the pusher catheter30are arranged to be substantially parallel in the vicinity of the forceps port122.

The proximal-end-side rigid part33of the pusher catheter30and the guide catheter10are grasped together and move in a direction of an arrow A2ofFIG. 9. At this time, a length in which the pusher catheter30is inserted into the channel117is the same as a length in which the guide catheter10and the guide wire140are extracted from the pusher cap41.

As illustrated inFIG. 10, the intermediate part32is moved (pushed) to the distal end side via the proximal-end-side rigid part33with respect to the guide catheter10and the distal end part of the diameter expansion-suppressing part31abuts the proximal end part of the stent20so that the stent20is pushed toward the distal end side. Around the outer peripheral surface of the guide catheter10, the stent20and the pusher catheter30slide to the distal end side. Because the bending stiffness of the diameter expansion-suppressing part31is greater than the bending stiffness of the intermediate part32, the diameter expansion-suppressing part31prevents the inner diameter of the distal end part of the pusher catheter30from expanding (increasing) compared to the inner diameter of the intermediate part32. Thereby, the proximal end surface of the stent20and the distal end surface of the diameter expansion-suppressing part31reliably come into contact with each other, and the force acting on the diameter expansion-suppressing part31is efficiently delivered to the stent20. When the intermediate part32of the pusher catheter30is arranged within the channel117formed in the bent part112, the bending of the bent part112is easily maintained because the bending stiffness of the intermediate part32is relatively small.

By repeating the above-mentioned operation, as illustrated inFIG. 10, the pusher catheter30is inserted into the channel117in a state in which the distal end positions of the guide catheter10and the guide wire140are constantly held, and the stent20is inserted to a position at which the flap23of the stent20is locked on a liver side of the stenosis portion P4and the flap24of the stent20is locked on the duodenal papilla P2. Thereafter, the guide catheter10, the pusher catheter30, and the guide wire140are pulled out from the inside of the bile duct P3and extracted from the channel117of the endoscope100so that the stent20is placed (released).

InFIG. 11, a state in which a conventional delivery system200is inserted into the channel117of the endoscope100is illustrated. The delivery system200includes a guide catheter201, and a stent202and a pusher catheter203into which the guide catheter201can be inserted. When the bent part112of the endoscope100is bent and the stent202is unlikely to be moved to the distal end side, a distal end part of the pusher catheter203may be deformed in a bellows shape when the stent202is pushed if the pusher catheter203is moved to the distal end side relative to the guide catheter201. In this case, the distal end part of the pusher catheter203having an expanded diameter strongly comes into contact with the inner peripheral surface of the channel117. A frictional force between the inner peripheral surface of the channel117and the distal end part of the pusher catheter203increases, a force necessary to push the stent202or the pusher catheter203increases, and operability of a user deteriorates. When the delivery system is inserted into the channel of the endoscope, the outer diameter of the delivery system is limited to be less than the inner diameter of the channel. In the placement of the stent, the pusher catheter formed in a tube shape performs an operation of pushing the stent formed in a tube shape while being guided by the guide catheter.

According to the delivery system1of the present embodiment, the pusher catheter30includes the diameter expansion-suppressing part31provided at the distal end part and the intermediate part32provided at the proximal end side of the diameter expansion-suppressing part31. Thus, when the distal end part of the diameter expansion-suppressing part31is allowed to abut the proximal end part of the stent20by pushing the intermediate part32to the guide catheter10, the stent20is pushed toward the distal end side in a state in which the diameter expansion-suppressing part31prevents the inner diameter of the distal end part of the pusher catheter30from expanding. Therefore, when the pusher catheter30pushes the stent20, it is possible to reliably release the stent20from the pusher catheter30after pushing the stent20without covering and storing the distal end part of the pusher catheter30in the proximal end part of the stent20and radially making a bulge at an outside and an inside simultaneously.

When there is a large difference between the wall thickness of the stent20and the wall thickness of the pusher catheter30, axial deviation is likely to occur between the stent20and the pusher catheter30, particularly, from the opening of the distal end part of the channel117to the duodenal papilla P2. Thus, it is impossible to uniformly deliver a pushing force to the stent20and placement of the stent20is difficult. Because the stent20and the pusher catheter30have substantially the same wall thickness, it is possible to prevent the axial deviation between the stent20and the pusher catheter30from occurring.

When the wall thickness of the pusher catheter30is thin, the force acting on the pusher catheter30is efficiently delivered to the stent20by providing the diameter expansion-suppressing part31at the distal end part of the pusher catheter30, and an effect of delivering and maintaining the force from the pusher catheter30to the stent20tends to increase. Consequently, by providing the diameter expansion-suppressing part31at the distal end part of the pusher catheter30, it is possible to thin the wall thickness of the pusher catheter30and set a wide variation of dimensions of the pusher catheter30. Because the proximal-end-side rigid part33is provided at the proximal end side of the intermediate part32in the pusher catheter30, the force acting on the proximal-end-side rigid part33can be further effectively delivered to the distal end side of the pusher catheter30.

In the present embodiment, it is possible to variously deform a configuration of the delivery system1as will be described below.

As illustrated inFIG. 3, a difference (a clearance) between an inner diameter L1of the stent20and an outer diameter L2of the guide catheter10may be less than or equal to 8% (0.08 times) of the inner diameter L1of the stent20. When the above-mentioned clearance is too large, axial deviation occurs between the stent20and the guide catheter10or the pusher catheter30, and the force pushing the pusher catheter30is not effectively delivered to the stent20(force delivery efficiency deteriorates). Particularly, when a stent having a thin wall thickness and a small bending stiffness (bending deformation is likely to occur) is placed, the stent is likely to be bent in an operation of placing the stent. Because the occurrence of frictional resistance within the channel117is prevented when the stent is bent, it is necessary to make bending the stent difficult by reducing a clearance.

From the study by the inventors so far, it can be confirmed that the above-mentioned axial deviation occurs and operability during placement of the stent deteriorates when a clearance design equivalent to that of an existing product (a clearance of about 22% with respect to an internal diameter of the stent) is made in the above-mentioned stent in which the wall thickness is thin. By setting the clearance to a value less than or equal to 8% of the inner diameter L1of the stent20, it is possible to suppress the axial deviation between the stent20and the pusher catheter30and favorably deliver the force for pushing the stent20.

Also, in the following Formula (2), a clearance ratio is specified.
{(L1−L2)/L1}×100(%)  (2)

In this modified example, a clearance ratio of the delivery system1may be less than or equal to 8%. Also, the clearance ratio of the delivery system1is greater than 0%.

The bending stillness of the diameter expansion-suppressing part31of the pusher catheter30may be greater than the bending stiffness of the stent20. In general, a degree of deformation between the proximal end part of the stent and the distal end part of the pusher catheter decreases as the bending stiffness of each portion increases. Also, the degree of deformation that is mentioned here indicates a dimensional variation amount of the tube shape in the radial direction. When the bending stiffness of the diameter expansion-suppressing part31is greater than the bending stiffness of the stent20, the diameter expansion-suppressing part31that is the distal end part of the pusher catheter30can push (place) the stent20without being deformed before the proximal end part of the stent20. However, the following problems occur when the bending stiffness of the diameter expansion-suppressing part31is excessively large depending on the length of the diameter expansion-suppressing part31in the axial direction. That is, when the diameter expansion-suppressing part31passes through the inside of the channel117formed in the bent part112which is bent, a hooked feeling (a stacked feeling) occurs between the inner peripheral surface of the channel117and the diameter expansion-suppressing part31because the diameter expansion-suppressing part31is unlikely to be deformed. In the worst case, the inner peripheral surface of the channel117is likely to be damaged.

From the study by the inventors so far, it is confirmed that the stent20is favorably pushed into the channel117if the bending stiffness of the diameter expansion-suppressing part31is less than or equal to 200% of the bending stiffness of the stent20when the pusher catheter30passes through the inside of the channel117of the bent part112in a bent shape adapted to a use environment.

The bending stiffness of the intermediate part32of the pusher catheter30may be less than the bending stiffness of the stent20. When the bending stiffness of the intermediate part32is greater than the bending stiffness of the stent20, a reaction force that the intermediate part32receives from the inner peripheral surface of the channel117increases when the stent20passes through the inside of the channel117of the bent part112in the bent shape. A following capability of the delivery system1within the channel117deteriorates and force delivery efficiency for the stent20deteriorates. When the bending stiffness of the intermediate part32is less than the bending stiffness of the stent20, the above-mentioned following capability of the delivery system1within the channel117is improved.

However, when the bending stiffness of the intermediate part32is excessively less than the bending stiffness of the stent20, the following problem occurs. That is, before a necessary push force when the stent20breaks through the stenosis portion P4is delivered to the stent20, deformation such as a kink due to stress concentration in which the bending stiffness is small with respect to the reaction force of the pusher catheter30delivered from the stent20is likely to occur. Thereby, the original delivery function is not shown and quality function deterioration is caused. From the study by the inventors so far, it can be confirmed that a good delivery function is shown when the bending stiffness of the intermediate part32of the pusher catheter30is greater than or equal to 50% of the bending stiffness of the stent20.

While an embodiment of the present invention has been described above with reference to the drawings, specific configurations are not limited to the embodiment, and changes, combinations, and deletions of the configurations, etc. can be included without departing from the spirit and scope of the present invention.

For example, in the above-mentioned embodiment, the pusher catheter30includes the diameter expansion-suppressing part31, the intermediate part32, and the proximal-end-side rigid part33. However, the pusher catheter30may be configured without including the proximal-end-side rigid part33.

The pusher catheter30is formed of a monolayer tube, but the pusher catheter may be formed of a multilayer tube. A reinforcing layer may be internally disposed.

EXAMPLES

An example of the present invention will be described in further detail through a specific example hereinafter, but the present invention is not limited to the following example.

Stent: the stent had a layer configuration of an inner layer (PFA)/a reinforcing layer (a coil)/an external layer (polyurethane) and had an inner diameter of 2.75 mm and an outer diameter of 3.2 mm.

Guide catheter: the guide catheter was made of a PFA tube and a distal end part was formed in a tapered shape which narrowed toward the distal end side. An outer diameter of a stent mount portion in which the stent was disposed was 2.6 mm.

Diameter expansion-suppressing part: the diameter expansion-suppressing part was subjected to tube molding in a compound material of polypropylene (Rockwell hardness (R-scale): 80), a styrene-based elastomer (durometer A hardness: 90), and barium sulfate (particle size distribution 1 to 100 μm (micrometers): cumulative frequency 80% of 1 μm to 10 μm) at a mixing ratio of 79:5:16. The diameter expansion-suppressing part was joined to an intermediate part by tube welding based on heating of a heater. The diameter expansion-suppressing part had an inner diameter of 2.75 mm and an outer diameter of 3.3 mm.

Intermediate part: the intermediate part was subjected to tube molding in a compound material of polypropylene (Rockwell hardness (R-scale): 80), a styrene-based elastomer (durometer A hardness: 90), and barium sulfate (particle size distribution 1 to 100 μm (micrometers): cumulative frequency 80% of 1 μm to 10 μm) at a mixing ratio of 54:29:17. The intermediate part was joined to the diameter expansion-suppressing part and a proximal-end-side rigid part by tube welding based on heating of a heater. The intermediate part had an inner diameter of 2.75 mm and an outer diameter of 3.3 mm. Proximal-end-side rigid part: the proximal-end-side rigid part used the same tube as the diameter expansion-suppressing part.

The stent had a bending stiffness of 7.2N.

Pusher Catheter

The diameter expansion-suppressing part and the proximal-end-side rigid part had a bending stiffness of 8.8N and the intermediate part had a bending stiffness of 5.7N.

Clearance ratio between the guide catheter and the stent: 5.8%

The bending stiffness of the diameter expansion-suppressing part was greater than the bending stiffness of the stent, and a bending stiffness ratio of the diameter expansion-suppressing part (when the numerator of the above-mentioned Formula (1) is the bending stiffness of the diameter expansion-suppressing part) was 122%.

The bending stiffness of the intermediate part was less than the bending stiffness of the stent, and a bending stiffness ratio of the intermediate part (when the numerator of the above-mentioned Formula (1) is the bending stiffness of the intermediate part) was 79%.

Through the above configuration, a delivery system capable of maintaining a moderate force delivery effect and reliably releasing and placing a stent is provided.

The present invention is limited only by the appended claims without being limited by the above description.