Dilator, and introducer assembly

Abstract

[Problem] To provide: a dilator that can achieve high trackability of a dilator body over a guidewire and high insertability of the dilator body into a bodily lumen even when the dilator body is configured to have a large diameter; and an introducer assembly. [Solution] A distal end 351 of a second cylindrical region 350 provided to a distal end region 300A of a dilator body 210 is located closer to an inner channel 215 side of the dilator body 210 than is a virtual line A1 connecting a distal end 341 of a first cylindrical region 340 and a distal end 361 of a third cylindrical region 360.

Description

Dilator and introducer assembly

[0001] The present invention relates to a dilator and introducer assembly.

[0002] An introducer (introducer circuit) is known that is used when performing treatment, diagnosis, etc. using various medical devices such as catheters. The introducer includes a sheath introducer having a tubular sheath member and a dilator having a dilator main body (dilator tube) inserted into the lumen of the sheath member (see, for example, Patent Document 1).

[0003] In a procedure using an introducer, prior to inserting the introducer into a biological lumen, the surgeon forms a perforation connecting the biological lumen to the outside of the body and places a guidewire through this perforation between the biological lumen and the outside of the body. The surgeon then inserts the dilator body into the sheath member, and with the introducer and dilator assembled, inserts the guidewire into the dilator body and inserts the dilator body and sheath member into the biological lumen along the guidewire. The surgeon then removes the dilator body from the sheath member with the sheath member still inserted into the biological lumen. With the dilator body removed from the sheath member, the surgeon can use the lumen of the sheath member as an access path connecting the biological lumen to the outside of the body to insert various medical devices used for treatment or diagnosis into the biological lumen.

[0004] By inserting the introducer into a perforation formed in the living body while the dilator body is inserted through the sheath member as described above, the surgeon can widen the perforation while preventing the dilator body from bending the sheath member.

[0005] The dilator body is required to have the ability to follow the guidewire inserted into the biological lumen prior to the sheath member, and to have insertability that can reduce the burden on the surgeon when operating the dilator.

[0006] Meanwhile, in recent years, attempts have been made to develop introducers intended for use in relatively large blood vessels such as arteries in the lower limbs (see, for example, Patent Document 2).

[0007] JP-A-7-303703 JP-A-2022-27860

[0008] The dilator included in the introducer described in Patent Document 2 is larger than dilators intended for use in relatively thin blood vessels such as those in the upper limbs, etc. Therefore, the dilator body included in the dilator is also configured to have a large diameter corresponding to the diameter of the blood vessel into which it is to be inserted.

[0009] When the dilator body is configured with a large diameter, the amount of material (e.g., resin) that forms the tube wall of the dilator body also increases. This increases the rigidity of the tip of the dilator body, leading to a decrease in the dilator body's ability to follow the guidewire. Furthermore, the increased amount of material that forms the tube wall at the tip of the dilator body also increases the insertion load of the dilator body.

[0010] Therefore, in a dilator body provided in an introducer intended for use in relatively large blood vessels such as the arteries of the lower limbs, it becomes even more difficult to achieve followability to the guidewire and ease of insertion of the dilator body.

[0011] The present invention has been made in consideration of the above problems, and aims to provide a dilator and introducer assembly that can achieve high followability of the dilator body relative to a guidewire and high insertability of the dilator body into a biological lumen (reduced insertion resistance of the dilator body when inserted into a biological lumen), even when the dilator body is configured with a large diameter.

[0012] The present invention can be achieved by any one of the following means (1) to (5).

[0013] (1) A dilator body includes a dilator body having an inner cavity that penetrates with a substantially constant diameter from the base end side to the tip end side, and a dilator hub that is connected to the base end of the dilator body and has an opening that communicates with the inner cavity of the dilator body, wherein the dilator body has a tip region, a base region, and an intermediate region located between the tip region and the base region, and the tip region includes: a first tapered region whose outer diameter decreases toward the tip end; a first cylindrical region that extends from the base end of the first tapered region toward the base end side of the tip region; a second cylindrical region that is located closer to the base end than the first cylindrical region and has an outer diameter larger than the outer diameter of the first cylindrical region; a third cylindrical region that is located closer to the base end than the second cylindrical region and has an outer diameter larger than the outer diameter of the second cylindrical region; and a second tapered region that is located between the first cylindrical region and the second cylindrical region and has an outer diameter that decreases from the tip of the second cylindrical region toward the base end of the first cylindrical region. a third tapered region located between the second cylindrical region and the third cylindrical region, the outer diameter of which decreases from the tip of the third cylindrical region toward the base end of the second cylindrical region, wherein the tip of the second cylindrical region is located closer to the inner cavity of the dilator body than an imaginary line connecting the tip of the first cylindrical region and the tip of the third cylindrical region.

[0014] (2) The dilator described in (1), wherein the sum of the axial length of the second tapered region and the axial length of the third tapered region is equal to or greater than the axial length of the second cylindrical region, and the sum of the axial length of the first tapered region and the axial length of the second tapered region is equal to or greater than the axial length of the first cylindrical region.

[0015] (3) The dilator according to (1) or (2), wherein the value of the outer diameter of the first cylindrical region / the outer diameter of the second cylindrical region is equal to or less than the value of the outer diameter of the second cylindrical region / the outer diameter of the third cylindrical region.

[0016] (4) The dilator according to any one of (1) to (3), wherein the taper angle of the third tapered region is equal to or greater than the taper angle of the second tapered region, and the taper angle of the second tapered region is equal to or greater than the taper angle of the first tapered region.

[0017] (5) An introducer assembly including: the dilator according to any one of (1) to (4); a sheath introducer including a tubular sheath member through which the dilator body can be inserted; and a sheath hub connected to a proximal end of the sheath member and connectable to the dilator hub; wherein the distal end region is configured as a region that protrudes distally beyond the distal end of the sheath member when the dilator body is inserted through the lumen of the sheath member; and the axial length of the third cylindrical region is equal to or less than the axial length of the second cylindrical region and equal to or less than the axial length of the first cylindrical region.

[0018] The distal region of the dilator body of the dilator of the present invention is arranged, in this order from the distal end to the proximal end, with a first tapered region, a first cylindrical region, a second tapered region, a second cylindrical region, a third tapered region, and a third cylindrical region. The distal region of the dilator body has an outer diameter that gradually increases from the distal end to the proximal end due to the tapered regions arranged in the distal region. Therefore, when the distal region of the dilator body is inserted into a biological lumen, the dilator can gradually widen a perforation formed in the living body from the distal end to the proximal end of the distal region. This prevents a perforation formed in the living body from being suddenly widened when the dilator body is inserted into a biological lumen. Therefore, surgeons can reduce the burden on the patient during procedures using the dilator. Furthermore, the distal region of the dilator body is provided with cylindrical regions arranged between the tapered regions. Each cylindrical region extends with a substantially constant outer diameter along the axial direction of the dilator body. Therefore, when a surgeon inserts the dilator body into a biological lumen, the insertion resistance of the dilator body can be reduced at each cylindrical region located between the tapered regions. This allows the surgeon to smoothly insert the dilator body into a biological lumen. Furthermore, the distal end of the second cylindrical region of the dilator body is located closer to the lumen of the dilator body than the imaginary line connecting the distal end of the first cylindrical region and the distal end of the third cylindrical region. This reduces the change in rigidity of the dilator body at the boundary between the distal end of the second cylindrical region and the proximal end of the second tapered region, improving flexibility near the boundary between the distal end of the second cylindrical region and the proximal end of the second tapered region. Furthermore, due to the change in rigidity at the boundary between the proximal end of the first cylindrical region and the distal end of the second tapered region, and at the boundary between the proximal end of the second cylindrical region and the distal end of the third tapered region, each boundary becomes an inflection point when the distal region is bent, improving the flexibility of the distal region.Furthermore, compared to when the shape (outer diameter) of a portion of the distal end region (outer diameter changing region) from the tip of the first cylindrical region to the tip of the third cylindrical region is configured so that it follows the imaginary line or is located outward of the imaginary line when viewed from the lumen side of the dilator body, the amount of material (e.g., resin) constituting the portion of the tubular wall of the dilator body in the outer diameter changing region is reduced. This allows the dilator body to improve the guidewire followability of the distal end region located near the most distal end of the dilator body and reduce the insertion load of the distal end region. Therefore, even when the dilator body is configured with a large diameter, the dilator according to the present invention can achieve high guidewire followability and high insertability of the dilator body into a biological lumen.

[0019] Fig. 1 is a diagram showing an introducer circuit according to an embodiment. Fig. 2 is a perspective view of a tip region of a dilator body according to an embodiment. Fig. 3 is a plan view of a tip region of a dilator body according to an embodiment. Fig. 4 is a cross-sectional view along the axial direction of the tip region of a dilator body according to an embodiment. Fig. 5 is an enlarged view of a cross section of a portion of the tip region of a dilator body according to an embodiment. Fig. 6 is an enlarged view of a cross section of a portion of the tip region of a dilator body according to an embodiment.

[0020] A dilator 200 according to an embodiment will be described with reference to FIGS. 1 to 6.

[0021] <Introducer Circuit 10> In this embodiment, an introducer circuit (introducer) 10 including a dilator 200 will be described.

[0022] As shown in FIG. 1 , the introducer circuit 10 includes a sheath introducer 100 and a dilator 200 .

[0023] The operator can detachably fix the dilator hub 220 to the cap member 140 in a state in which the dilator body 210 is inserted into the interior of the sheath hub 130 of the sheath member 110 and into the lumen 115 of the sheath member 110. In this specification, the introducer circuit 10 in a state in which the dilator body 210 of the dilator 200 is inserted into the sheath member 110 of the sheath introducer 100 to form a distal end region 300A on the distal end side of the sheath member 110 (the state shown in FIGS. 3 to 6 ), or in a state before the dilator 300 and the sheath introducer 100 are assembled (separated state) as shown in FIG. 1 is referred to as an "introducer assembly."

[0024] <Sheath Introducer 100 > The sheath introducer 100 includes a tubular sheath member (sheath tube) 110 and a sheath hub 130 connected to a proximal end portion 113 of the sheath member 110 .

[0025] In the description of this specification, the direction in which the sheath member 110 extends is referred to as the "axial direction" and is indicated by arrows X1-X2. The direction indicated by arrow X1 is defined as the distal end side of the axial direction, and the direction indicated by arrow X2 is defined as the proximal end side of the axial direction. The axial direction of the dilator 200 (extension direction of the central axis c1) is the direction indicated by arrows X1-X2, similar to the axial direction of the sheath member 110. Note that arrows Y1-Y2 in the drawings indicate a direction perpendicular to the axial direction.

[0026] The sheath introducer 100 can be used to introduce various medical devices into a biological lumen (e.g., a blood vessel) via the lumen 115 of the sheath member 110. Specific methods and procedures for using the sheath introducer 100 are not particularly limited, but for example, the sheath introducer 100 can be used to form an access path for delivering various medical devices (e.g., a stent for placement in the aorta, a device used in artificial valve replacement surgery to treat aortic stenosis, a device for treating pulmonary thrombosis, etc.) from a relatively large-diameter blood vessel running through the lower limb to various parts of the living body, using the blood vessel in the lower limb as the insertion target site.

[0027] The introducer circuit 10 can be used, for example, in the following procedure.

[0028] The surgeon connects the dilator 200 to the sheath introducer 100 to form an introducer assembly, and then inserts the sheath member 110 into a perforation formed in the living body that connects the outside of the living body with a biological lumen into which the sheath member 110 is to be inserted, and widens the perforation. The dilator 200 prevents the sheath member 110 from being bent or otherwise damaged when the sheath member 110 is inserted into the biological lumen through the perforation as described above.

[0029] Prior to inserting the dilator 200 and the sheath member 110 into the biological lumen as described above, the surgeon passes a guide wire, which is disposed between the biological lumen and the outside of the living body, through the dilator body 210 via a perforation formed in the living body, and inserts the dilator 200 and the sheath member 110 along the guide wire into the biological lumen. After inserting the distal end 211 of the dilator body 210 to a predetermined position in the biological lumen, the surgeon removes the dilator body 210 from the sheath member 110. The surgeon can use the lumen 115 of the sheath member 110, from which the dilator body 210 has been removed, as an access route to deliver various medical devices to desired positions in the biological lumen.

[0030] As shown in FIGS. 1 and 2, the sheath member 110 has a distal end portion 111 having a distal end opening 111a formed at the most distal end position, and a proximal end portion 113 disposed inside the sheath hub 130.

[0031] The sheath member 110 has an inner lumen 115 that extends continuously between the distal end 111 and the proximal end 113 .

[0032] The proximal end portion 113 of the sheath member 110 is provided with a proximal end opening 113 a that is arranged so as to communicate with the inside of the sheath hub 130 .

[0033] As shown in FIGS. 1 and 3, the distal end portion 111 of the sheath member 110 has a tapered shape in which the outer diameter tapers toward the distal end.

[0034] The sheath member 110 can be made of, for example, a polymer material such as polyolefin (e.g., polyethylene, polypropylene, polybutene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ionomer, or a mixture of two or more thereof), polyolefin elastomer, crosslinked polyolefin, polyvinyl chloride, polyamide, polyamide elastomer, polyester, polyester elastomer, polyurethane, polyurethane elastomer, fluororesin (e.g., polytetrafluoroethylene, tetrafluoroethylene-ethylene copolymer), polycarbonate, polystyrene, polyacetal, polyimide, polyetherimide, polyether ether ketone, or a mixture thereof. The sheath member 110 may also have a reinforcing member such as a metal wire within the wall thickness of a tubular member made of a polymer material or a mixture thereof.

[0035] 1, a valve body 160 is disposed inside the sheath hub 130. The valve body 160 is configured so that the dilator body 210 and a medical device to be inserted into a biological lumen can be inserted therethrough.

[0036] The valve body 160 prevents a gap from being formed between the dilator body 210 or the medical device when the dilator body 210 or the medical device is inserted through the valve body 160. By preventing the formation of the gap, the valve body 160 prevents a liquid such as blood or saline injected into the sheath hub 130 from flowing back toward the base end side of the cap member 140 connected to the sheath hub 130.

[0037] The sheath hub 130 has a first port portion 171 and a second port portion 172 that communicate with the interior of the sheath hub 130 .

[0038] A tube 181 connected to a three-way stopcock 190 for supplying a liquid such as physiological saline to the inside of the sheath hub 130 can be connected to the first port portion 171 .

[0039] A suction device can be connected to the second port 172 via a tube 182. The suction device can be used when performing a procedure to aspirate a blood clot or the like in a vein. Note that the installation of the second port 172 can be omitted as appropriate depending on the intended use of the introducer circuit 10, etc.

[0040] The sheath introducer 100 has a cap member 140 connected to the proximal end of the sheath hub 130. The cap member 140 has an opening (not shown) that communicates with the inside of the sheath hub 130. The surgeon or the like can insert the dilator body 210 into the inside of the sheath hub 130 and the lumen 115 of the sheath member 110 by pushing the dilator body 210 from the proximal end side of the cap member 140.

[0041] <Dilator 200> As shown in Figures 1 to 4, the dilator 200 includes a dilator body 210 having an inner cavity 215 that passes through with a substantially constant diameter d1 from the base end side to the tip end side, and a dilator hub 220 that is connected to the base end 213 of the dilator body 210 and has an opening 227 that communicates with the inner cavity 215 of the dilator body 210.

[0042] The dilator body 210 can be made of, for example, a resin material such as high-density polyethylene, low-density polyethylene, vinyl chloride, polyurethane, polyamide, or polyester, an elastomer material such as polyurethane elastomer, polyamide elastomer, or polyester elastomer, or a combination of two or more of these materials (e.g., a polymer blend).The dilator 200 may also have a low-friction resin such as PTFE (polytetrafluoroethylene) disposed on the inner surface that forms the lumen 215 of the dilator body 210 made of the above materials.

[0043] 1, the proximal end 213 of the dilator body 210 is disposed in the internal space 225 of the dilator hub 220. A proximal end opening 213a formed in the proximal end 213 of the dilator body 210 communicates with an opening 227 of the dilator hub 220 via the internal space 225 of the dilator hub 220.

[0044] As shown in FIG. 1, the dilator body 210 has a distal region 300A, a proximal region 300B, and an intermediate region 300C located between the distal region 300A and the proximal region 300B.

[0045] In this specification, in a state in which the introducer assembly is constructed (a state in which the dilator body 210 of the dilator 200 is inserted into the sheath member 110 of the sheath introducer 100), the distal region of the dilator body 210 that protrudes distally beyond the distal end portion 111 of the sheath member 110 is defined as the "distal region 300A" (see FIGS. 3 and 4). Furthermore, in the dilator body 210, the region disposed within the dilator hub 220 is defined as the "proximal region 300B." Furthermore, the region extending between the distal region 300A and the proximal region 300B is defined as the "intermediate region 300C." The tip region 300A is a region on the tip side of the dilator body 210 that protrudes further distally than the tip portion 111 of the sheath member 110 when the dilator body 210 of the dilator 200 is inserted into the sheath member 110 of the sheath introducer 100 and the dilator hub 220 is fixed to or in contact with the cap member 140.

[0046] The proximal end region 300B and the intermediate region 300C have substantially the same outer diameter. The intermediate region 300C extends from the proximal end 363 of the third cylindrical region 360 located in the distal end region 300A toward the proximal end (see FIGS. 3 and 4). Therefore, in this embodiment, the outer diameters of the proximal end region 300B, the intermediate region 300C, and the third cylindrical region 360 are substantially the same.

[0047] As described above, the inner diameter d1 (diameter of the lumen 215) of the dilator body 210 is substantially constant along the axial direction. Therefore, in this embodiment, the thickness of the base end region 300B, the thickness of the intermediate region 300C, and the thickness t3 (see FIG. 5 ) of the third cylindrical region 360 located in the distal end region 300A are substantially constant.

[0048] As shown in FIGS. 2 to 6, the distal end region 300A includes a first tapered region 310 whose outer diameter decreases toward the tip of the dilator body 210, a first cylindrical region 340 extending from a base end 313 of the first tapered region 310 toward the base end of the distal end region 300A, a second cylindrical region 350 located closer to the base end than the first cylindrical region 340 and having an outer diameter D2 larger than the outer diameter D1 of the first cylindrical region 340, and a second cylindrical region 350 located closer to the base end than the second cylindrical region 350 and having an outer diameter D3 of the second cylindrical region 350. The cylindrical member has a third cylindrical region 360 having an outer diameter D3 larger than the diameter D2, a second tapered region 320 located between the first cylindrical region 340 and the second cylindrical region 350, and having an outer diameter that decreases from the tip 351 of the second cylindrical region 350 toward the base end 343 of the first cylindrical region 340, and a third tapered region 330 located between the second cylindrical region 350 and the third cylindrical region 360, and having an outer diameter that decreases from the tip 361 of the third cylindrical region 360 toward the base end 353 of the second cylindrical region 350.

[0049] The tapered regions 310, 320, 330 and the cylindrical regions 340, 350, 360 located in the tip region 300A have circular inner and outer circumferential surfaces in an orthogonal cross section (a cross section perpendicular to the central axis c1).

[0050] Each of the cylindrical regions 340, 350, and 360 extends with a substantially constant outer diameter along the axial direction of the dilator body 210. Therefore, the outer peripheral surface of each of the cylindrical regions 340, 350, and 360 extends in a substantially linear shape parallel to the central axis c1 in the drawings shown in Figures 3 and 4.

[0051] 3 and 4, the tip of the dilator body 210 is located at the tip 301 of the tip region 300A. In addition, the tip 311 of the first tapered region 310 located at the most tip side in the tip region 300A is located at the same position as the tip 301 of the tip region 300A.

[0052] 3 and 4 , the base end 303 of the distal region 300A is located at the base end 363 of the third cylindrical region 360, which is located at the base end side of the distal region 300A. As described above, the intermediate region 300C, which extends continuously from the third cylindrical region 360, is located on the base end side of the third cylindrical region 360. Therefore, the base end 303 of the distal region 300A is located at the boundary between the third cylindrical region 360 and the intermediate region 300C (the boundary between the distal region 300A and the intermediate region 300C).

[0053] 3 and 4 , the base end 313 of the first tapered region 310 is located at a position overlapping with the tip 341 of the first cylindrical region 340 that is connected to the first tapered region 310 on the base end side of the first tapered region 310. Therefore, the base end 313 of the first tapered region 310 and the tip 341 of the first cylindrical region 340 are located at the boundary between the regions 310 and 340.

[0054] 3 and 4 , the base end 343 of the first cylindrical region 340 is located at a position overlapping the tip 321 of the second tapered region 320 that is connected to the first cylindrical region 340 on the base end side of the first cylindrical region 340. Therefore, the base end 343 of the first cylindrical region 340 and the tip 321 of the second tapered region 320 are located at the boundary between the regions 340 and 320.

[0055] 3 and 4 , the base end 323 of the second tapered region 320 is located at a position overlapping with the tip 351 of the second cylindrical region 350 that is connected to the second tapered region 320 on the base end side of the second tapered region 320. Therefore, the base end 323 of the second tapered region 320 and the tip 351 of the second cylindrical region 350 are located at the boundary between the regions 320 and 350.

[0056] 3 and 4 , the base end 353 of the second cylindrical region 350 is located at a position overlapping the tip 331 of the third tapered region 330 that is connected to the second cylindrical region 350 on the base end side of the second cylindrical region 350. Therefore, the base end 353 of the second cylindrical region 350 and the tip 331 of the third tapered region 330 are located at the boundary between the regions 350 and 330.

[0057] 3 and 4 , the base end 333 of the third tapered region 330 is located at a position overlapping with the tip 361 of the third cylindrical region 360 that is connected to the third tapered region 330 on the base end side of the third tapered region 330. Therefore, the base end 333 of the third tapered region 330 and the tip 361 of the third cylindrical region 360 are located at the boundary between the regions 330 and 360.

[0058] As shown in Figures 3 and 4, the outer diameter D1 of the first cylindrical region 340 is smaller than the outer diameter D2 of the second cylindrical region 350, which in turn is smaller than the outer diameter D3 of the third cylindrical region 360. As described above, the diameter d1 of the lumen 215 of the dilator body 210 is substantially constant along the axial direction. Therefore, the wall thickness t1 of the first cylindrical region 340 is smaller than the wall thickness t2 of the second cylindrical region 350, which in turn is smaller than the wall thickness t3 of the third cylindrical region 360. Therefore, the amount of material (e.g., resin) constituting the tube wall of the distal portion of the dilator body 210 is smaller than that of the proximal portion of the distal region 300A. This results in greater flexibility in the distal portion of the dilator body 210 than in the proximal portion of the distal region 300A.

[0059] The dilator body 210 has three tapered regions 310, 320, 330 provided at different axial positions of the distal end region 300A. Therefore, when the distal end region 300A of the dilator body 210 is inserted into a biological lumen, the dilator 200 can gradually widen a perforation formed in the living body from the distal end toward the proximal end of the distal end region 300A. Therefore, when the dilator body 210 is inserted into a biological lumen, the dilator 200 can prevent a perforation formed in the living body from being suddenly widened.

[0060] The dilator body 210 also includes multiple cylindrical regions 340, 350, 360 located between the tapered regions 310, 320, 330. Each of the cylindrical regions 340, 350, 360 extends with a substantially constant outer diameter along the axial direction of the dilator body 210. Therefore, when an operator inserts the dilator body 210 into a biological lumen, the insertion resistance of the dilator body 210 can be reduced in each of the cylindrical regions 340, 350, 360 located between the tapered regions 310, 320, 330.

[0061] As shown in Figures 3, 4, and 6, the tip 351 of the second cylindrical region 350 is located closer to the inner cavity 215 of the dilator body 210 (closer to the central axis c1) than the imaginary line A1 connecting the tip 341 of the first cylindrical region 340 and the tip 361 of the third cylindrical region 360.

[0062] The virtual line A1 can be defined as a virtual straight line connecting the tip 341 of the first cylindrical region 340 and the tip 361 of the third cylindrical region 360 on the plan view shown in FIG. 3 (or the axial cross-sectional view shown in FIG. 4 ) in a natural state in which no external force is applied to the dilator body 210.

[0063] In this embodiment, the axial range of the tip region 300A located between the tip 341 of the first cylindrical region 340, which serves as the reference for drawing the virtual line A1, and the tip 361 of the third cylindrical region 360 is defined as the "outer diameter change region 370."

[0064] As described above, the distal end 351 of the second cylindrical region 350 of the dilator body 210 is located closer to the lumen 215 of the dilator body 210 than the imaginary line A1 connecting the distal end 341 of the first cylindrical region 340 and the distal end 361 of the third cylindrical region 360. Therefore, in the dilator body 210, changes in rigidity at the boundary between the distal end 351 of the second cylindrical region 350 and the proximal end 323 of the second tapered region 320 are alleviated, and flexibility is improved near the boundary between the distal end 351 of the second cylindrical region 350 and the proximal end 323 of the second tapered region 320. Therefore, the flexibility of the dilator body 210 smoothly changes from the proximal end to the distal end of a portion of the distal region 300A (outer diameter changing region 370) from the distal end 341 of the first cylindrical region 340 to the distal end 361 of the third cylindrical region 360. Furthermore, due to changes in rigidity at the boundary between the base end 343 of the first cylindrical region 340 and the tip 321 of the second tapered region 320, and at the boundary between the base end 353 of the second cylindrical region 350 and the tip 331 of the third tapered region 330, each boundary becomes an inflection point when the tip region 300A is bent, improving the flexibility of the tip region 300A. Furthermore, compared to when the dilator body 210 is configured so that the shape (outer diameter) of a portion of the tip region 300A (outer diameter changing region 370) from the tip 341 of the first cylindrical region 340 to the tip 361 of the third cylindrical region 360 is along the imaginary line A1 or is located outside the imaginary line A1 when viewed from the lumen 215 side of the dilator body 210, the amount of constituent material (e.g., resin amount) of the portion forming the tubular wall of the dilator body 210 in the outer diameter changing region 370 is reduced. As a result, the dilator body 210 can improve the followability of the tip region 300A, which is located near the most distal end of the dilator body 210, to the guide wire and reduce the insertion load of the tip region 300A (improving insertability into a biological lumen).

[0065] In the above explanation, "when the shape (outer diameter) of the outer diameter changing region 370 changes so as to follow the imaginary line A1 or to be positioned outside the lumen 215 of the dilator body 210 relative to the imaginary line A1" means that the constituent material of the portion forming the tubular wall of the dilator body 210 is present in the gap between the imaginary line A1 shown in the drawing in FIG. 3 and the outer peripheral surface of each part included in the outer diameter changing region 370, or that the constituent material of the portion forming the tubular wall of the dilator body 210 is present beyond the imaginary line A1 on the far side as viewed from the lumen 215.

[0066] Next, the preferable size relationships between the dimensions of each part of the dilator body 210 will be described.

[0067] 3 can be formed to be equal to or greater than the axial length L22 of the second cylindrical region 350. In addition, the sum of the axial length L11 of the first tapered region 310 and the axial length L12 of the second tapered region 320 can be formed to be equal to or greater than the axial length L21 of the first cylindrical region 340.

[0068] As described above, the dilator body 210 is formed so that the sum of the axial length L12 of the second tapered region 320 and the axial length L13 of the third tapered region 330 is equal to or greater than the axial length L22 of the second cylindrical region 350 extending between the tapered regions 320, 330. This reduces insertion resistance using the second cylindrical region 350 located between the tapered regions 320, 330, while allowing for gradual changes in the outer diameter of the dilator body 210 on the distal and proximal sides of the second cylindrical region 350. Similarly, the dilator body 210 is formed so that the sum of the axial length L11 of the first tapered region 310 and the axial length L12 of the second tapered region 320 is equal to or greater than the axial length L21 of the first cylindrical region 340 located between the tapered regions 310, 320. This reduces insertion resistance using the first cylindrical region 340 located between the tapered regions 310, 320, while allowing the outer diameter of the dilator body 210 to change gradually on the distal and proximal sides of the first cylindrical region 340.

[0069] In addition, when configuring the outer diameter change of each tapered region 310, 320, 330 as gradual as possible as described above, it is preferable to make the axial lengths L11, L12, L13 of each tapered region 310, 320, 330 as long as possible. However, if the axial lengths L11, L12, L13 of each tapered region 310, 320, 330 are simply increased, the ratio of the axial lengths L21, L22 of each cylindrical region 340, 350 to the axial lengths of each tapered region 310, 320, 330 becomes relatively small, making it difficult to suppress insertion resistance. In this embodiment, in the tip region 300A having a predetermined axial length La, by adjusting the axial lengths of each region as described above, the outer diameter change of each tapered region 310, 320, 330 is made gradual while reducing the insertion resistance of each cylindrical region 340, 350.

[0070] The value of outer diameter D1 of the first cylindrical region 340 / outer diameter D2 of the second cylindrical region 350 (D1 / D2) shown in Figure 3 can be formed to be equal to or less than the value of outer diameter D2 of the second cylindrical region 350 / outer diameter D3 of the third cylindrical region 360 (D2 / D3).

[0071] As described above, the dilator body 210 is formed so that the value of (D1 / D2) is equal to or less than the value of (D2 / D3), and therefore the rate of change in outer diameter between the first cylindrical region 340 and the second cylindrical region 350 is greater than the rate of change in outer diameter between the second cylindrical region 350 and the third cylindrical region 360. In other words, when comparing the amount of change in outer diameter between the cylindrical regions 340, 350, and 360 in the distal end region 300A, the rate of reduction in the outer diameter of each of the cylindrical regions 340, 350, and 360 increases from the base end to the distal end. Therefore, the dilator body 210 is formed so that the rate of reduction in the amount of material constituting the tube wall of each of the cylindrical regions 340, 350, and 360 is greater from the base end to the distal end of the distal end region 300A, and the distal end region 300A is more flexible.

[0072] The taper angle θ3 of the third tapered region 330 (see FIG. 5) can be greater than or equal to the taper angle θ2 of the second tapered region 320 (see FIG. 6). In addition, the taper angle θ2 of the second tapered region 320 can be greater than or equal to the taper angle θ1 of the first tapered region 310 (see FIG. 6).

[0073] Each taper angle θ1, θ2, θ3 can be defined as the angle between an imaginary straight line H1 parallel to the central axis c1 and the outer peripheral surface of each tapered region 310, 320, 330 in a cross section along the axial direction of the dilator body 210.

[0074] As described above, the dilator body 210 is configured so that the taper angles θ1, θ2, θ3 of the tapered regions 310, 320, 330 decrease from the base end to the tip end, and therefore the first tapered region 310 located on the tip side of the tip region 300A experiences a steeper change in outer diameter due to the taper than the other tapered regions 320, 330 located on the base end side. Therefore, the dilator body 210 can further effectively improve the insertability of the first tapered region 310 located at the tip end, which is thinner and more flexible.

[0075] As shown in Figures 3 and 4, when the introducer assembly is constructed, the axial length L23 of the third cylindrical region 360 is equal to or less than the axial length L22 of the second cylindrical region 350 and equal to or less than the axial length L21 of the first cylindrical region 340.

[0076] As described above, the introducer assembly is configured so that the axial length L23 of the third cylindrical region 360 has a predetermined length. Therefore, when the dilator body 210 is inserted into the lumen 115 of the sheath member 110, a cylindrical region (straight portion) of a predetermined length can be disposed between the distal end of the sheath member 110 (the position of the distal end opening 111a) and the proximal end 333 of the third tapered region 330, which is the tapered region located most proximally in the distal end region 300A. This prevents the formation of a location (a step) where the outer diameter changes abruptly between the distal end of the sheath member 110 and the proximal end 333 of the third tapered region 330. Therefore, the introducer assembly allows the dilator body 210 to be smoothly inserted into a biological lumen.

[0077] Furthermore, the introducer assembly can prevent the axial length L23 of the third cylindrical region 360 from becoming excessively large when the axial length L23 of the third cylindrical region 360 is configured to be equivalent to the axial length L22 of the second cylindrical region 350 and the axial length L11 of the first cylindrical region 340. This makes it possible to prevent the third cylindrical region 360 from bending when the introducer assembly inserts the dilator body 210 into a biological lumen, and enables the dilator body 210 to be smoothly inserted into a biological lumen with less pushing force.

[0078] In order to prevent the introducer assembly from forming a point (step) where the outer diameter changes suddenly as described above, and to prevent the third cylindrical region 360 from bending as described above when the dilator body 210 is inserted into a biological lumen, it is preferable that the axial length L23 of the third cylindrical region 360 be equal to or less than half the outer diameter D3 of the third cylindrical region 360, and more preferably be equal to or greater than 3 mm.

[0079] The introducer circuit 10 may employ the following example dimensions as an example for realizing the dimensional relationship of the above-mentioned components.

[0080] The axial length of the sheath member 110 can be formed to be, for example, 300 mm or more and 1000 mm or less.

[0081] The diameter (inner diameter) of the lumen 115 of the sheath member 110 can be, for example, 5.0 mm or more and 10.0 mm or less. The diameters of the distal end opening 111 a of the sheath member 110 and the proximal end opening 113 a of the sheath member 110 can be formed to be approximately the same as the diameter of the lumen 115 of the sheath member 110.

[0082] The axial length La (see FIG. 3) of the distal end region 300A of the dilator body 210 can be formed to be, for example, 50 mm or more and 100 mm or less.

[0083] The axial length of the proximal end region 300B of the dilator body 210 can be formed to be, for example, 5.0 mm or more and 15.0 mm or less.

[0084] The axial length of the intermediate region 300C of the dilator body 210 can be formed to be, for example, 300 mm or more and 1000 mm or less.

[0085] The diameter d1 (inner diameter shown in FIG. 4 ) of the lumen 215 of the dilator body 210 can be formed to be, for example, 0.9 mm or more and 2.0 mm or less. The diameter of the distal opening 211a of the dilator body 210 and the diameter of the proximal opening 213a of the dilator body 210 can be formed to be approximately the same as the diameter d1 of the lumen 215 of the dilator body 210.

[0086] The axial length L11 (see FIG. 3) of the first tapered region 310 can be formed to be, for example, 5 mm or more and 15 mm or less.

[0087] The axial length L12 (see FIG. 3) of the second tapered region 320 can be formed to be, for example, 5 mm or more and 15 mm or less.

[0088] The axial length L13 (see FIG. 3) of the third tapered region 330 can be formed to be, for example, 5 mm or more and 15 mm or less.

[0089] The taper angle θ1 (see FIG. 6) of the first tapered region 310 can be formed to be, for example, not less than 1.3° and not more than 4.0°.

[0090] The taper angle θ2 (see FIG. 6) of the second tapered region 320 can be formed to be, for example, not less than 3.6° and not more than 10.7°.

[0091] The taper angle θ3 (see FIG. 5) of the third tapered region 330 can be formed to be, for example, not less than 4.6° and not more than 13.5°.

[0092] The axial length L21 (see FIG. 3) of the first cylindrical region 340 can be formed to be, for example, not less than 10 mm and not more than 30 mm.

[0093] The axial length L22 (see FIG. 3) of the second cylindrical region 350 can be formed to be, for example, not less than 10 mm and not more than 30 mm.

[0094] The axial length L23 (see FIG. 3) of the third cylindrical region 360 can be formed to be, for example, not less than 10 mm and not more than 30 mm.

[0095] The outer diameter D1 (see FIG. 3) of the first cylindrical region 340 may be, for example, 2.2 mm or more and 3.0 mm or less. The thickness t1 (see FIG. 6) of the first cylindrical region 340 may be, for example, 0.1 mm or more and 1.1 mm or less.

[0096] The outer diameter D2 (see FIG. 3) of the second cylindrical region 350 can be, for example, 3.0 mm or more and 5.0 mm or less. The thickness t2 (see FIG. 5) of the second cylindrical region 350 can be, for example, 0.5 mm or more and 2.1 mm or less.

[0097] The third cylindrical region 360 may have an outer diameter D3 (see FIG. 3) of, for example, 5.0 mm or more and 10.0 mm or less, and a wall thickness t3 (see FIG. 5) of, for example, 1.5 mm or more and 4.6 mm or less.

[0098] As described above, the dilator 200 according to this embodiment comprises a dilator body 210 having an inner cavity 115 penetrating from the base end side to the tip end side with a substantially constant diameter d1, and a dilator hub 220 connected to the base end 113 of the dilator body 210 and having an opening 227 communicating with the inner cavity 215 of the dilator body 210. The dilator body 210 has a tip region 300A, a base region 300B, and an intermediate region 300C located between the tip region 300A and the base region 300B. The tip region 300A has a first tapered region 310 whose outer diameter decreases toward the tip end of the dilator body 210, and a tapered region 310 extending from the base end 313 of the first tapered region 310 toward the base end side of the tip region 300A. a first cylindrical region 340 extending from the distal end 351 of the second cylindrical region 350 toward the proximal end 343 of the first cylindrical region 340; a second cylindrical region 350 located closer to the proximal end than the first cylindrical region 340 and having an outer diameter D2 larger than the outer diameter D1 of the first cylindrical region 340; a third cylindrical region 360 located closer to the proximal end than the second cylindrical region 350 and having an outer diameter D3 larger than the outer diameter D2 of the second cylindrical region 350; a second tapered region 320 located between the first cylindrical region 340 and the second cylindrical region 350 and having an outer diameter decreasing from the distal end 351 of the second cylindrical region 350 toward the proximal end 343 of the first cylindrical region 340; and a third tapered region 330 located between the second cylindrical region 350 and the third cylindrical region 360 and having an outer diameter decreasing from the distal end 361 of the third cylindrical region 360 toward the proximal end 353 of the second cylindrical region 350.

[0099] As described above, the distal end region 300A of the dilator body 210 included in the dilator 200 is arranged, in this order from the distal end to the proximal end, with the first tapered region 310, the first cylindrical region 340, the second tapered region 320, the second cylindrical region 350, the third tapered region 330, and the third cylindrical region 360. The distal end region 300A of the dilator body 210 has an outer diameter that gradually increases from the distal end to the proximal end due to the tapered regions 310, 320, and 330 arranged in the distal end region 300A. Therefore, when the distal end region 300A of the dilator body 210 is inserted into a biological lumen, the dilator 200 can gradually widen a perforation formed in the living body from the distal end toward the proximal end of the distal end region 300A. This allows the dilator 200 to prevent a perforation formed in the living body from being suddenly widened when the dilator body 210 is inserted into a biological lumen. Therefore, the surgeon can reduce the burden on the patient during the procedure using the dilator 200.

[0100] Furthermore, the distal end region 300A of the dilator body 210 is provided with cylindrical regions 340, 350, and 360 that are disposed between the tapered regions 310, 320, and 330. Each of the cylindrical regions 340, 350, and 360 extends with a substantially constant outer diameter along the axial direction of the dilator body 210. Therefore, when an operator inserts the dilator body 210 into a biological lumen, the operator can reduce the insertion resistance of the dilator body 210 at each of the cylindrical regions 340, 350, and 360 that are disposed between the tapered regions 310, 320, and 330. This allows the operator to smoothly insert the dilator body 210 into a biological lumen while reducing the burden on the patient, such as pain, that occurs when the dilator body 210 pushes open the perforation.

[0101] Furthermore, in the dilator body 210, the tip 351 of the second cylindrical region 350 is located closer to the lumen 215 of the dilator body 210 than the imaginary line A1 connecting the tip 341 of the first cylindrical region 340 and the tip 361 of the third cylindrical region 360. Therefore, in the dilator body 210, changes in rigidity at the boundary between the tip 351 of the second cylindrical region 350 and the base end 323 of the second tapered region 320 are alleviated, and flexibility is improved near the boundary between the tip 351 of the second cylindrical region 350 and the base end 323 of the second tapered region 320. Furthermore, due to changes in rigidity at the boundary between the base end 343 of the first cylindrical region 340 and the tip 321 of the second tapered region 320, and at the boundary between the base end 353 of the second cylindrical region 350 and the tip 331 of the third tapered region 330, each boundary becomes an inflection point when the tip region 300A is bent, improving the flexibility of the tip region 300A. Furthermore, compared to when the dilator body 210 is configured so that the shape (outer diameter) of a portion of the tip region 300A (outer diameter changing region 370) from the tip 341 of the first cylindrical region 340 to the tip 361 of the third cylindrical region 360 is along the imaginary line A1 or is located outside the imaginary line A1 when viewed from the lumen 215 side of the dilator body 210, the amount of constituent material (e.g., resin amount) of the portion forming the tubular wall of the dilator body 210 in the outer diameter changing region 370 is reduced. This allows the dilator body 210 to improve the ability of the tip region 300A located near the most distal end of the dilator body 210 to follow the guide wire and improve the insertability of the tip region 300A into a biological lumen.

[0102] As described above, the dilator 200 according to this embodiment can achieve high followability of the dilator body 210 relative to the guidewire and high insertability of the dilator body 210 into a biological lumen, even when the dilator body 210 is configured with a large diameter.

[0103] Furthermore, the dilator body 210 can be formed so that the sum of the axial length L12 of the second tapered region 320 and the axial length L13 of the third tapered region 330 is equal to or greater than the axial length L22 of the second cylindrical region 350, and the sum of the axial length L11 of the first tapered region 310 and the axial length L12 of the second tapered region 320 is equal to or greater than the axial length L21 of the first cylindrical region 340.

[0104] As described above, the dilator body 210 is formed so that the sum of the axial length L12 of the second tapered region 320 and the axial length L13 of the third tapered region 330 is equal to or greater than the axial length L22 of the second cylindrical region 350 extending between the tapered regions 320, 330. This reduces insertion resistance using the second cylindrical region 350 located between the tapered regions 320, 330, while allowing for gradual changes in the outer diameter of the dilator body 210 on the distal and proximal sides of the second cylindrical region 350. Furthermore, the dilator body 210 is formed so that the sum of the axial length L11 of the first tapered region 310 and the axial length L12 of the second tapered region 320 is equal to or greater than the axial length L21 of the first cylindrical region 340 extending between the tapered regions 310, 320. This reduces insertion resistance due to the first cylindrical region 340 located between the tapered regions 310, 320, while allowing for gradual changes in the outer diameter of the dilator body 210 on the distal and proximal sides of the first cylindrical region 340. Therefore, the dilator body 210 can more effectively improve the insertability of the distal region 300A into a biological lumen.

[0105] Furthermore, the dilator body 210 is formed such that the value of outer diameter D1 of the first cylindrical region 340 / outer diameter D2 of the second cylindrical region 350 (D1 / D2) is equal to or less than the value of outer diameter D2 of the second cylindrical region 350 / outer diameter D3 of the third cylindrical region 360 (D2 / D3).

[0106] Because the dilator body 210 is formed such that the value of (D1 / D2) is equal to or less than the value of (D2 / D3) as described above, the rate of change in outer diameter between the first cylindrical region 340 and the second cylindrical region 350 is greater than the rate of change in outer diameter between the second cylindrical region 350 and the third cylindrical region 360. Therefore, when comparing the amount of change in outer diameter between the cylindrical regions 340, 350, and 360 in the distal end region 300A, the rate of reduction in the outer diameter of each of the cylindrical regions 340, 350, and 360 increases from the base end side to the distal end side. As a result, in the dilator body 210, the rate of reduction in the amount of constituent material of the portions forming the tube walls of each of the cylindrical regions 340, 350, and 360 increases from the base end side to the distal end side of the distal end region 300A. Therefore, the dilator body 210 can be formed with greater flexibility near the tip 301 of the tip region 300A, and the ability of the tip portion 211 of the dilator body 210 to follow the guidewire can be further effectively improved.

[0107] In addition, the dilator body 210 has a taper angle θ3 of the third tapered region 330 that is equal to or greater than the taper angle θ2 of the second tapered region 320, and the taper angle θ2 of the second tapered region 320 that is equal to or greater than the taper angle θ1 of the first tapered region 310.

[0108] As described above, the dilator body 210 is configured so that the taper angles θ1, θ2, θ3 of the tapered regions 310, 320, 330 become smaller from the base end to the tip end, and therefore the first tapered region 310 located on the tip side of the tip region 300A experiences a steeper change in outer diameter due to the taper than the other tapered regions 320, 330 located on the base end side. Therefore, the dilator body 210 can further effectively improve the insertability of the first tapered region 310 located at the tip end, which is configured to be thinner and more flexible.

[0109] In addition, in an introducer assembly having a dilator 200, a sheath introducer 100 including a tubular sheath member 110 through which a dilator body 210 can be inserted, and a sheath hub 130 connected to the proximal end 113 of the sheath member 110 and connectable to the dilator 200, the distal end region 300A is configured as a region that protrudes distally beyond the distal end of the sheath member 110 when the dilator body 210 is inserted through the inner cavity 115 of the sheath member 110, and the axial length L23 of the third cylindrical region 360 is equal to or less than the axial length L22 of the second cylindrical region 350 and is equal to or less than the axial length L21 of the first cylindrical region 340.

[0110] As described above, the introducer assembly is configured so that the axial length L23 of the third cylindrical region 360 has a predetermined length. Therefore, when the dilator body 210 is inserted into the lumen 115 of the sheath member 110, a cylindrical region (straight portion) of a predetermined length can be disposed between the distal end of the sheath member 110 (the position of the distal opening 111a) and the proximal end 333 of the third tapered region 330, which is the tapered region located most proximal in the distal end region 300A. This prevents the formation of a location (a step) where the outer diameter changes abruptly between the distal end of the sheath member 110 and the proximal end 333 of the third tapered region 330 when the dilator body 210 is inserted into a biological lumen. Therefore, the dilator body 210 can more effectively improve the insertability of the distal end region 300A into a biological lumen.

[0111] Furthermore, the introducer assembly can prevent the axial length L23 of the third cylindrical region 360 from becoming excessively large when the axial length L23 of the third cylindrical region 360 is configured to be equivalent to the axial length L22 of the second cylindrical region 350 and the axial length L11 of the first cylindrical region 340. This makes it possible to prevent the third cylindrical region 360 from bending when the introducer assembly inserts the dilator body 210 into a biological lumen, and allows the dilator body 210 to be smoothly inserted into the biological lumen with less pushing force.

[0112] Although the dilator and introducer assembly according to the present invention has been described above through the embodiments, the present invention is not limited to the content described in this specification and may be modified as appropriate based on the claims.

[0113] The structure of each part and the arrangement of components described in the specification may be changed as appropriate, and the use of additional components described in the drawings may be omitted or other additional components may be used as appropriate.

[0114] This application is based on Japanese Patent Application No. 2024-86075, filed on May 28, 2024, the disclosure of which is incorporated herein by reference in its entirety.

[0115] 10 Introducer circuit 100 Sheath introducer 110 Sheath member 111 Distal end of sheath member 113 Proximal end of sheath member 115 Lumen of sheath member 130 Sheath hub 200 Dilator 210 Dilator body 211 Distal end of dilator body 211a Distal opening of dilator body 213 Proximal end of dilator body 213a Proximal opening of dilator body 215 Lumen of dilator body 220 Dilator hub 227 Opening of dilator hub 300A Distal region 300B Proximal region 300C Intermediate region 301 Distip end of distal region 303 Proximal end of distal region 310 First tapered region 311 Distip end of first tapered region 313 Proximal end of first tapered region 320 Second tapered region 321 Distance of second tapered region 323 Base end of second tapered region 330 Third tapered region 331 Distance of third tapered region 333 Base end of third tapered region 340 First cylindrical region 341 Distance of first cylindrical region 343 Base end of first cylindrical region 350 Second cylindrical region 351 Distance of second cylindrical region 353 Base end of second cylindrical region 360 Third cylindrical region 361 Distance of third cylindrical region 363 Base end of third cylindrical region 370 Outer diameter changing region A1 Virtual line c1 Central axis of dilator body La Axial length of distal region L11 Axial length of first tapered region L12 Axial length of second tapered region L13 Axial length of third tapered region L21 Axial length of first cylindrical region L22 Axial length of second cylindrical region L23 Axial length of third cylindrical region D1 Outer diameter of first cylindrical region D2 Outer diameter of second cylindrical region D3 Outer diameter of the third cylindrical region d1 Diameter of the bore t1 Wall thickness of the first cylindrical region t2 Wall thickness of the second cylindrical region t3 Wall thickness of the third cylindrical region θ1 Taper angle of the first tapered region θ2 Taper angle of the second tapered region θ3 Taper angle of the third tapered region

Claims

1. A dilator body having a lumen that penetrates with a substantially constant diameter from the base end side to the tip end side, and a dilator hub connected to the base end of the dilator body and having an opening that communicates with the lumen of the dilator body, wherein the dilator body has a tip region, a base region, and an intermediate region located between the tip region and the base region, wherein the tip region has: a first tapered region whose outer diameter decreases toward the tip end; a first cylindrical region extending from the base end of the first tapered region toward the base end of the tip region; a second cylindrical region located closer to the base end than the first cylindrical region and having an outer diameter larger than the outer diameter of the first cylindrical region; a third cylindrical region located closer to the base end than the second cylindrical region and having an outer diameter larger than the outer diameter of the second cylindrical region; and a second tapered region located between the first cylindrical region and the second cylindrical region and having an outer diameter that decreases from the tip of the second cylindrical region toward the base end of the first cylindrical region. a third tapered region located between the second cylindrical region and the third cylindrical region, the outer diameter of which decreases from the tip of the third cylindrical region toward the base end of the second cylindrical region, wherein the tip of the second cylindrical region is located closer to the inner cavity of the dilator body than an imaginary line connecting the tip of the first cylindrical region and the tip of the third cylindrical region.

2. A dilator as described in claim 1, wherein the sum of the axial length of the second tapered region and the axial length of the third tapered region is equal to or greater than the axial length of the second cylindrical region, and the sum of the axial length of the first tapered region and the axial length of the second tapered region is equal to or greater than the axial length of the first cylindrical region.

3. The dilator according to claim 1, wherein the value of the outer diameter of the first cylindrical region / the outer diameter of the second cylindrical region is equal to or less than the value of the outer diameter of the second cylindrical region / the outer diameter of the third cylindrical region.

4. The dilator according to claim 1, wherein the taper angle of the third tapered region is equal to or greater than the taper angle of the second tapered region, and the taper angle of the second tapered region is equal to or greater than the taper angle of the first tapered region.

5. An introducer assembly comprising: a dilator according to any one of claims 1 to 4; a sheath introducer comprising a tubular sheath member through which the dilator body can be inserted; and a sheath hub connected to the proximal end of the sheath member and connectable to the dilator hub; wherein the distal region is configured as a region that protrudes distally beyond the distal end of the sheath member when the dilator body is inserted through the lumen of the sheath member; and the axial length of the third cylindrical region is less than or equal to the axial length of the second cylindrical region and is also less than or equal to the axial length of the first cylindrical region.

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