Variable stiffness dilator for intravascular access device

Abstract

Disclosed herein is a medical device comprising: an introducer sheath (100) comprising a stiffness transition (110); and a dilator (300) comprising a stiffness transition (312). When the dilator (300) occupies the lumen of the introducer sheath (100), the stiffness transition (110) of the introducer sheath is longitudinally offset from the stiffness transition (312) of the dilator, and the medical device can navigate through a significantly higher number of turns in the vasculature than without the longitudinally offset stiffness transition.

Description

[0001] Related Applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 412,946, filed on October 4, 2022, which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present disclosure relates to medical devices and, more particularly, to introducer sheaths and dilators having offset transitions in stiffness. Background Art

[0004] The statements in this section merely provide background information related to the present disclosure and may constitute prior art.

[0005] In today's medical field, many medical procedures require entry into a patient's blood vessels for the purpose of accessing a desired site, such as angioplasty and stent placement. In order to access the desired site, a sheath is usually advanced through the blood vessel. Once in place within the patient's blood vessel, various types of medical instruments can be fed through the sheath and positioned at the desired site so that the procedure can be performed.

[0006] To initially access a specific site within a patient's body, a needle is used to pierce the patient's skin and enter the desired blood vessel, a guide wire is then inserted into a lumen in the needle and fed into the blood vessel, and then the needle is removed and the guide wire is left in place.

[0007] The dilator / sheath assembly is then placed over the guidewire and advanced to a position inside the blood vessel. The distal end of the dilator can taper to a relatively small diameter and extend beyond the distal end of the sheath. The tapered distal end of the dilator allows the dilator / sheath assembly to be introduced into the patient's blood vessel in a manner that gradually increases the size of the opening in the blood vessel so that the blood vessel can ultimately accommodate a larger sized sheath without causing trauma, injury or other difficulties to the patient. Once the guidewire and dilator / sheath assembly are advanced to the desired location within the blood vessel, the dilator is removed. Summary of the invention

[0008] In an example, the present disclosure provides a medical device, the medical device includes an introducer sheath, the introducer sheath includes a tubular structure, the tubular structure includes a wall defining a sheath lumen extending longitudinally through the tubular structure, the tubular structure defines a longitudinal axis passing therethrough, the tubular structure further includes: a first longitudinal sheath segment, which has a first sheath stiffness; and a second longitudinal sheath segment distal to the first longitudinal sheath segment, the second longitudinal sheath segment having a second sheath stiffness less than the first sheath stiffness; and a sheath transition from the first longitudinal sheath segment to the second longitudinal sheath segment, the medical device further includes an expansion The expander is configured to occupy a sheath lumen, the expander comprising a shaft including a wall defining a expander lumen extending longitudinally therethrough, the shaft defining a second longitudinal axis, the second longitudinal axis being coaxial with the longitudinal axis when the expander occupies the sheath lumen, the shaft further comprising: a first longitudinal expander section having a first expander stiffness; and a second longitudinal expander section distal to the first longitudinal expander section, the second longitudinal expander section having a second expander stiffness less than the first expander stiffness; and a expander transition from the first longitudinal expander section to the second longitudinal expander section, the second longitudinal expander section extending longitudinally therethrough when the expander occupies the sheath lumen. When the sheath lumen is formed, the sheath transition portion is longitudinally offset from the dilator transition portion, in some examples, the first sheath stiffness can be less than the first dilator stiffness, in other examples, the sheath transition portion can be distal to the dilator transition portion, in still other examples, the second dilator stiffness can be less than the first sheath stiffness and greater than the second sheath stiffness, in still other examples, the dilator transition portion can be distal to the sheath transition portion, in still other examples, the second dilator stiffness can be less than the second sheath stiffness, in still other examples, the second longitudinal sheath segment can include a sheath distal tip at the distal end of the second longitudinal sheath segment; and when the dilator is formed, the sheath transition portion can be distal to the dilator transition portion, in still other examples, the second dilator stiffness can be less than the second sheath stiffness, and in still other examples, the second longitudinal sheath segment can include a sheath distal tip at the distal end of the second longitudinal sheath segment; and When the expander occupies the sheath lumen, the second longitudinal expander section can be configured to extend distally through the distal end of the sheath by at least one centimeter. In still other examples, the shaft can further include a third longitudinal expander section distal to the second longitudinal expander section, the third longitudinal expander section having a third expander stiffness different from the second expander stiffness. In still other examples, the third expander stiffness can be less than the second expander stiffness. In still other examples, the third expander stiffness can be greater than the second expander stiffness and / or equal to the first expander stiffness. In still other examples, the longitudinal expander length can be greater than the longitudinal sheath length.

[0009] In another example, the present disclosure provides an introducer sheath comprising a wall defining a sheath lumen extending longitudinally through a tubular structure, the tubular structure defining a longitudinal axis passing therethrough, the tubular structure comprising: a first longitudinal sheath segment having a first sheath stiffness; a second longitudinal sheath segment distal to the first longitudinal sheath segment, the second longitudinal sheath segment having a second sheath stiffness less than the first sheath stiffness; and a sheath transition from the first longitudinal sheath segment to the second longitudinal sheath segment, the dilator being configured to occupy the sheath lumen such that the sheath transition is longitudinally offset from the dilator transition from the first longitudinal dilator segment to the second longitudinal dilator segment , the dilator includes a shaft comprising: a wall defining a dilator lumen extending longitudinally through the shaft; a first longitudinal dilator section having a first dilator stiffness; and a second longitudinal dilator section distal to the first longitudinal dilator section and having a second dilator stiffness less than the first dilator stiffness. In some examples, the first sheath stiffness can be less than the first dilator stiffness. In other examples, the sheath transition portion can be configured to be distal to the dilator transition portion. In still other examples, the second dilator stiffness can be less than the first sheath stiffness and greater than the second sheath stiffness. In still other examples, the dilator transition portion can be configured to be distal to the sheath transition portion.

[0010] In yet another example, the present disclosure provides a dilator comprising a shaft comprising: a wall defining a dilator lumen extending longitudinally through the shaft; a first longitudinal dilator section having a first dilator stiffness; a second longitudinal dilator section distal to the first longitudinal dilator section, the second longitudinal dilator section having a second dilator stiffness less than the first dilator stiffness; and a dilator transition portion from the first longitudinal dilator section to the second longitudinal dilator section, the dilator being configured to occupy a sheath lumen of an introducer sheath such that the sheath transition portion from the first longitudinal sheath section to the second longitudinal sheath section is longitudinally offset from the dilator transition portion , the introducer sheath includes a tubular structure, the tubular structure including: a wall, the wall defining a sheath lumen extending longitudinally through the tubular structure, the tubular structure defining a longitudinal axis passing therethrough, the tubular structure including: a first longitudinal sheath segment having a first sheath stiffness; and a second longitudinal sheath segment, distal to the first longitudinal sheath segment and having a second sheath stiffness less than the first sheath stiffness, in some examples, the first sheath stiffness can be less than the first dilator stiffness, in other examples, the sheath transition portion can be configured to be distal to the dilator transition portion, in still other examples, the second dilator stiffness can be less than the first sheath stiffness and greater than the second sheath stiffness.

[0011] Further areas of applicability will become apparent from the description provided herein, and it should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order that the present disclosure may be better understood, various forms of the present disclosure given by way of example will now be described with reference to the accompanying drawings, wherein components are not necessarily drawn to scale and in which like reference numerals designate corresponding parts throughout the different views.

[0013] Figure 1 shows a side view of an example of an introducer sheath according to the principles of the present disclosure;

[0014] Figure 2 Shown Figure 1 A cross-sectional view of an example distal tip of an introducer sheath;

[0015] Figure 3 A side view showing an example of a dilator according to the principles of the present disclosure is shown;

[0016] Figure 4 shows a side view of another example of a dilator according to the principles of the present disclosure;

[0017] Figure 5 Shown Figure 4 A distal end view of an example of a dilator;

[0018] Figure 6 Demonstrated model tracking paths for analyzing various medical devices for their ability to complete turns in the vasculature without device failure;

[0019] Figure 7 Shown Figure 6 an exploded view of a model-tracked path in FIG. 1 indicating the number of turns in the vasculature at each point along the model-tracked path;

[0020] Figure 8 shows a side view of an example of an introducer sheath and an example of a dilator shown separately in accordance with the principles of the present disclosure; and

[0021] Fig. 9 Shown is a side view of an example of an introducer sheath and an example of a dilator occupying a sheath lumen in accordance with principles of the present disclosure.

[0022] The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. DETAILED DESCRIPTION

[0023] The following description presents examples and is not intended to limit the present disclosure, application, or uses, and it should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.

[0024] When adding reference designations to elements of each figure, it should be noted that the same elements have the same designations although the same elements are shown on different figures. In addition, when describing one aspect of the present disclosure, if it is determined that the detailed description of the related well-known configuration or function makes the main idea of ​​one aspect of the present disclosure obscure, it will be omitted.

[0025] In the following discussion, the terms "proximal" and "distal" will be used to describe the opposite axial ends of a device, as well as the axial ends of various component features, the term "proximal" is used in its conventional sense to refer to the end of a device (or component) closest to a medical professional during use of the assembly, the term "distal" is used in its conventional sense to refer to the end of a device (or component) that is initially inserted into a patient, or closest to the patient, during use, the term "longitudinal" will be used to refer to an axis aligned with the proximal-distal axis of the device (or component), the terms "radially" and "radial" will be used to refer to elements, surfaces or components relative to each other that can extend perpendicularly from the longitudinal axis, and the terms "circumferentially", "circumferentially" and "circumferential" will be used to refer to elements, surfaces or components relative to each other that surround the longitudinal axis at a certain radius.

[0026] The use of the terms "a" and "an" and "the" and similar referents in the context of describing the present disclosure (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context; unless applicants expressly assert otherwise, use of the term "plurality" is to be defined by applicants in the broadest sense, superseding any other implied definition or limitation, preceding or following, to refer to a quantity of more than one; unless otherwise indicated herein or clearly contradicted by context, the recitation of ranges of values ​​herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, and each separate value is incorporated into the specification as if it were recited individually herein; and all methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context.

[0027] As used herein, the terms "including," "comprising," "having," "has," "may," "containing," and variations thereof are intended to be open transitional phrases, terms, or words that do not exclude the possibility of additional actions or structures, and this description also contemplates other examples of "including," "consisting of," and "consisting essentially of" the examples or elements presented herein, whether explicitly stated or not.

[0028] When describing the elements of the present disclosure, the terms first (1st), second (2nd), first (first), second (second), A, B, (a), (b), etc. may be used herein. These terms are only used to distinguish one element from another element, but do not limit the corresponding elements, regardless of the nature or order of the corresponding elements.

[0029] Unless otherwise stated, all terms (including technical or scientific terms) used herein have the same meaning as commonly understood by technicians in the field to which the present disclosure belongs, and terms such as terms defined in general dictionaries will be interpreted as having the same meaning as the contextual meaning in the relevant field.

[0030] As used herein, the term "about" when used in the context of a stated value or range means a variation of ±15% or less of that value, e.g., values ​​that differ by ±15%, ±14%, ±10% or ±5%, etc., will satisfy the definition of "about" unless more narrowly defined in a particular instance.

[0031] As used herein, the term "stiffness" refers to a measure of the hardness of a material (e.g., a polymer, elastomer, or rubber). The term is relative and unitless, but a higher stiffness indicates a material with greater resistance to indentation and therefore a harder and less flexible and bendable property, while a lower relative stiffness indicates a material with lower resistance to indentation and therefore a softer and more flexible and bendable property. Methods for measuring or otherwise determining the relative stiffness of a material are generally known to those of ordinary skill in the art. In a specific example, stiffness can be measured by a Shore durometer, which measures the depth of an indentation in a material produced by a given force on a standardized presser foot. The depth can depend on the hardness of the material, the viscoelastic properties of the material, the shape of the presser foot, and the duration of the test. There are several scales of durometers that can be used for materials with different properties, but the two most common scales are: the ASTM D2240 Type A scale, in which a presser foot is pressed into the material with a force of approximately 10N for 15 seconds; and the Type D scale, in which the presser foot penetrates the surface of the material with a force of approximately 50N for 15 seconds. Each durometer scale produces values ​​between 0 and 100, with increasing values ​​indicating harder materials.

[0032] refer to Figure 1, showing a side view of an example of an introducer sheath 100, the introducer sheath 100 includes a tubular structure 104, the tubular structure includes a wall 118, the wall defining a sheath lumen 120 extending longitudinally through the tubular structure 104 from the proximal end 114 to the distal end 112, the tubular structure 104 defines a first longitudinal axis 122 extending therethrough, the proximal end 114 of the tubular structure 104 is fixed to the valve body 102, the tubular structure 104 includes a first longitudinal sheath segment 106 and a second longitudinal sheath segment 108, the second longitudinal sheath segment 108 is distal to the first longitudinal sheath segment 106, the first longitudinal sheath segment 106 has a first sheath stiffness, and the second longitudinal sheath segment 106 has a smaller stiffness than the first longitudinal sheath segment 106. The first and second longitudinal jacket segments 106, 108 are connected at a jacket transition 110, and the tubular structure 104 can be made by butt-joining the first longitudinal jacket segment 106 to the second longitudinal jacket segment 108. Alternatively, the second longitudinal jacket segment 108 can be integral with the first longitudinal jacket segment 106, and the tubular structure 104 can be formed by a process such as full batch extrusion, wherein the tubular structure 104 is prepared so that the first longitudinal jacket segment 106 has a first jacket stiffness and the second longitudinal jacket segment 108 has a second jacket stiffness, and the tubular structure 104 has a length L from a proximal end 114 to a distal end 112. S , the length of the second longitudinal jacket section 108 is L A (length of the middle longitudinal section 116) and L B The length of the first longitudinal sheath section 106 is the length L of the tubular structure 104. S Subtract L A +L B The sum of, or L S –(L A +L B ).

[0033] In some examples, the first jacket stiffness and the second jacket stiffness may differ by a value of at least 5D, or at least 10D, or at least 15D, or at least 20D, or at least 25D, or at least 30D, or at least 35D, or at least 40D, or at least 45D, or at least 50D, or at least 55D, or at least 60D, or at least 65D, or at least 70D, or at least 75D, or at least 80D, or at least 85D, or at least 90D, or at least 95D according to the ASTM D2240 Type D scale for measurement by a Shore durometer. In a specific example, the first jacket stiffness may be greater than 50D, or greater than 55D, or greater than 60D, or greater than 65D, or greater than 70D, or greater than 75D, and the second jacket stiffness may be less than 50D, or less than 45D, or less than 45D. 0D, or less than 35D, or less than 30D, or less than 25D, in other specific examples, the first sheath stiffness can be about 52D, or about 54D, or about 56D, or about 58D, or about 60D, or about 62D, or about 64D, or about 66D, or about 68D, or about 70D, or about 72D, or about 74D, or about 76D, or about 78D, or about 80D, and the second sheath stiffness can be about 48D, or about 46D, or about 44D, or about 42D, or about 40D, or about 38D, or about 36D, or about 34D, or about 32D, or about 30D, or about 28D, or about 26D, or about 24D, or about 22D, or about 20D.

[0034] In some examples, the length L of the tubular structure 104 is S It may be at least about 20 cm, or at least about 22 cm, or at least about 24 cm, or at least about 26 cm, or at least about 28 cm, or at least about 30 cm, or at least about 32 cm, or at least about 34 cm, or at least about 36 cm, or at least about 38 cm, or at least about 40 cm, or at least about 42 cm, or at least about 44 cm, or at least about 46 cm, or at least about 48 cm, or at least about 50 cm, or at least about 52 cm, or at least about 54 cm, or at least about 56 cm, or at least about 57 cm. 8cm, or at least about 60cm, in other specific examples, the longitudinal length LB of the distal tip 112 can be at least about 0.2cm, or at least about 0.3cm, or at least about 0.4cm, or at least about 0.5cm, or at least about 0.6cm, or at least about 0.7cm, or at least about 0.8cm, or at least about 0.9cm, or at least about 1.0cm, or at least about 1.1cm, or at least about 1.2cm, or at least about 1.3cm, or at least about 1.4cm, or at least about 1.5cm.

[0035] In an example, the tubular structure 104 may have a longitudinal cross-sectional dimension within a size range from 4 French ("Fr.") to 24 French. As will be appreciated by those skilled in the art, the French scale or French gauge system, which is typically used to measure the size of a medical device (e.g., a catheter), refers to three times the length of the outer diameter of the medical device (measured in millimeters ("mm")). In the case of the tubular structure 104, the French gauge system would refer to three times the length of the tubular structure 104 from wall 118 to wall 118 (measured in millimeters). For example, a 1 French round tubular structure 104 would have an outer diameter of 1 / 3 mm; a 3 French round catheter would have an outer diameter of 1 mm. In some examples, the tubular structure 104 may have the following sizes: from 4 French to 24 French, including from 5 French, or from 6 French, or from 7 French, or from 8 French, or from 9 French, or from 10 French, or from 11 French, or from 12 French, or from 13 French, or from 14 French, or from 15 French. ench, or from 16French, or from 17French, or from 18French, or from 19French, or from 20French, or from 21French, or from 22French, or from 23French to 24French; or from 4French to 5French, or to 6French, or to 7French, or to 8French, or to 9French, or to 10French, or to 11French ench, or to 12 French, or to 13 French, or to 14 French, or to 15 French, or to 16 French, or to 17 French, or to 18 French, or to 19 French, or to 20 French, or to 21 French, or to 22 French, or to 23 French, or to 24 French; or any other range from one of the above minimum values ​​to one of the above maximum values.

[0036] In an example, the first longitudinal jacket segment 106 and the second longitudinal jacket segment 108 can each include a blend of 0-95% polypropylene ("PP") impact copolymer and 5-100% high performance elastomer, examples of which can include thermoplastic elastomers, such as thermoplastic olefins ("TPO"), thermoplastic polyurethanes ("TPU"), thermoplastic vulcanizates ("TPV"), polyester elastomers, polyamide elastomers (e.g., polyester block amide ("PEBA")), nylon, polyethylene, and fluoropolymers (e.g., fluorinated ethylene propylene ("FEP"), perfluoroalkoxyalkane ("PFA"), and ethylene tetrafluoroethylene ("ETFE")).

[0037] refer to Figure 2 , showing a cross-sectional view of an example distal tip 112 of an introducer sheath 100, as shown in Figure 2 As shown in FIG. 1 , the wall 118 may taper slightly toward the distal end of the tubular structure 104, and the sheath lumen 120 of the tubular structure 104 may have a L T The diameter, diameter L T The dilator may be sized such that it may reversibly occupy the sheath lumen 120 .

[0038] refer to Figure 3 , showing a side view of an example of a dilator 300, the dilator 300 includes a shaft 302, the shaft including a wall defining a dilator lumen extending longitudinally through the shaft 302, the shaft 302 defining a second longitudinal axis 316, when the dilator 300 occupies the sheath lumen 120 of the introducer sheath 100, the second longitudinal axis 316 is coaxial with the first longitudinal axis 122 of the introducer sheath 100, the shaft 302 extends from the proximal end 304 to the distal end 306, the shaft 302 includes a first longitudinal dilator section 308 and a second longitudinal dilator section 310, the second longitudinal dilator section 310 is distal to the first longitudinal dilator section 308, the first longitudinal dilator section 308 has a first dilator stiffness, and the second longitudinal dilator section 310 has a stiffness less than the first dilator stiffness. The first longitudinal dilator section 308 and the second longitudinal dilator section 310 are connected at the dilator transition section 312, and the shaft 302 can be made by butt-joining the first longitudinal dilator section 308 to the second longitudinal dilator section 310. Alternatively, the second longitudinal dilator section 310 can be integral with the first longitudinal dilator section 308, and the shaft 302 can be formed by a process such as full intermittent extrusion, wherein the shaft 302 is prepared so that the first longitudinal dilator section 308 has a first dilator stiffness and the second longitudinal dilator section 310 has a second dilator stiffness, the proximal end 304 is attached to the dilator hub 314, and the shaft 302 has a length L from the proximal end 304 to the distal tip 306. D, the second longitudinal expander section 310 has a length L C , length L C Can be greater than L A +L B The sum, alternatively, of length L C Can be smaller than L A +L B The length of the first longitudinal expander section 310 is L of the shaft 302. D Subtract the length L of the second longitudinal section 310 C , when the dilator 300 occupies the sheath lumen 120 of the introducer sheath 100 , the sheath transition portion 110 is longitudinally offset from the dilator transition portion 312 , and the sheath transition portion 110 is proximal or distal to the dilator transition portion 312 .

[0039] In examples, when the dilator 300 occupies the sheath lumen 120 of the introducer sheath 100, the sheath transition portion 110 is longitudinally offset from the dilator transition portion 312 by a distance of at least about 0.1 cm, or at least about 0.2 cm, or at least about 0.3 cm, or at least about 0.4 cm, or at least about 0.5 cm, or at least about 0.6 cm, or at least about 0.7 cm, or at least about 0.8 cm, or at least about 0.9 cm, or at least about 1.0 cm, or at least about 1.1 cm, or at least about 1.2 cm, or at least about 1.3 cm, or at least about 1.4 cm, or at least about 1.5 cm, or at least about 1.6 cm, or at least about 1.7 cm, or at least about 1.8 cm, or at least about 1.9 cm. or at least about 3.9 cm, or at least about 4.0 cm, or at least about 4.1 cm, or at least about 4.2 cm, or at least about 4.3 cm, or at least about 4.4 cm, or at least about 4.5 cm, or at least about 4.6 cm, or at least about 4.7 cm, or at least about 4.8 cm, or at least about 4.9 cm, or at least about 5.0 cm, or at least about 5.1 cm, or at least about 5.2 cm, or at least about 5.3 cm, or at least about 5.4 cm, or at least about 5.5 cm, or at least about 5.6 cm, or at least about 5.7 cm, or at least about 5.8 cm, or at least about 5.9 cm, or at least about 6.0 cm, or at least about 6.1 cm, or at least about 6.2 cm, or at least about 6.3 cm, or at least about 6.4 cm. or at least about 4.5 cm, or at least about 4.6 cm, or at least about 4.7 cm, or at least about 4.8 cm, or at least about 4.9 cm, or at least about 5.0 cm, or at least about 5.1 cm, or at least about 5.2 cm, or at least about 5.3 cm, or at least about 5.4 cm, or at least about 5.5 cm, or at least about 5.6 cm, or at least about 5.7 cm, or at least about 5.8 cm, or at least about 5.9 cm, or at least about 6.0 cm, or at least about 6.1 cm, or at least about 6.2 cm, or at least about 6.3 cm, or at least about 6.4 cm, or at least about 6.5 cm, or at least about 6.6 cm, or at least about 6.7 cm, or at least about 6.8 cm, or at least about 6.9 cm. 9 cm, or at least about 7.0 cm, or at least about 7.1 cm, or at least about 7.2 cm, or at least about 7.3 cm, or at least about 7.4 cm, or at least about 7.5 cm, or at least about 7.6 cm, or at least about 7.7 cm, or at least about 7.8 cm, or at least about 7.9 cm, or at least about 8.0 cm, or at least about 8.1 cm, or at least about 8.2 cm, or at least about 8.3 cm, or at least about 8.4 cm, or at least about 8.5 cm, or at least about 8.6 cm, or at least about 8.7 cm, or at least about 8.8 cm, or at least about 8.9 cm, or at least about 9.0 cm, or at least about 9.1 cm, or at least about 9.2 cm, or at least about 9.3 cm, or at least about 9.4cm, or at least about 9.5cm, or at least about 9.6cm, or at least about 9.7cm, or at least about 9.8cm, or at least about 9.9cm, or at least about 10.0cm. .

[0040] In some examples, the first expander stiffness and the second expander stiffness can differ by a value of at least 5D, or at least 10D, or at least 15D, or at least 20D, or at least 25D, or at least 30D, or at least 35D, or at least 40D, or at least 45D, or at least 50D, or at least 55D, or at least 60D, or at least 65D, or at least 70D, or at least 75D, or at least 80D, or at least 85D, or at least 90D, or at least 95D according to the ASTM D2240 Type D scale for measurement by a Shore durometer. In certain examples, the first expander stiffness and the second expander stiffness can differ by a value of at least 5D, or at least 10D, or at least 15D, or at least 20D, or at least 25D, or at least 30D, or at least 35D, or at least 40D, or at least 45D, or at least 50D, or at least 55D, or at least 60D, or at least 65D, or at least 70D, or at least 75D, or at least 80D, or at least 85D, or at least 90D, or at least 95D. In certain examples, the first expander stiffness and the second expander stiffness can differ by a value of at least 5D, or at least 10D, or at least 15D, or at least 15D, or at least 160D, or at least 165D, or at least 170D, or at least 175D, or at least 180D, or at least 185D, or at least 190D, or at least 195D. The stiffness can be greater than the first sheath stiffness and greater than 55D, or greater than 60D, or greater than 65D, or greater than 70D, or greater than 75D. In other specific examples, when the shaft 302 of the dilator 300 occupies the sheath lumen 120 of the introducer sheath 100 and the dilator transition portion 312 is proximal to the sheath transition portion 110, the second dilator stiffness can be greater than the second sheath stiffness but less than the first sheath stiffness. In still other specific examples, when the shaft 302 of the dilator 300 occupies the sheath lumen 120 of the introducer sheath 100 and the dilator transition portion 312 is proximal to the sheath transition portion 110, the second dilator stiffness can be greater than the second sheath stiffness but less than the first sheath stiffness. When occupying the sheath lumen 120 of the introducer sheath 100 and the dilator transition portion 312 is distal to the sheath transition portion 110, the second dilator stiffness can be less than the second sheath stiffness, and can be less than 45D, or less than 40D, or less than 35D, or less than 30D, or less than 25D. In still other specific examples, the first dilator stiffness can be about 56D, or about 58D, or about 60D, or about 62D, or about 64D, or about 66D, or about 68D, Or about 70D, or about 72D, or about 74D, or about 76D, or about 78D, or about 80D, and the second expander stiffness can be about 55D, or about 54D, or about 52D, or about 50D, or about 48D, or about 46D, or about 44D, or about 42D, or about 40D, or about 38D, or about 36D, or about 34D, or about 32D, or about 30D, or about 28D, or about 26D, or about 24D, or about 22D, or about 20D.

[0041] By including a single stiffness transition in the dilator 300 and a single stiffness transition in the introducer sheath 100, and offsetting the dilator transition 312 longitudinally from the sheath transition 110, these offset stiffness transitions advantageously produce a combined effect of a series of stiffness transitions ranging from a highest stiffness in the first longitudinal dilator section 308, to a lower stiffness in the first longitudinal sheath section 106, to a lower stiffness in the second longitudinal dilator section 310 (or the second longitudinal sheath section 108), and finally to a lowest stiffness in the second longitudinal sheath section 108 (or the second longitudinal dilator section 310), these offset stiffness transitions result in a transition that is advantageously perceived as unique to the operator of the introducer sheath 100 and the dilator 300, while minimizing the stiffness transitions in each of the introducer sheath 100 and the dilator 300.

[0042] In some examples, the length L of shaft 302 D can be greater than the length L of the tubular structure 104 S Length L is at least about 0.5 cm, or length L is at least about 1.0 cm, or length L is at least about 1.5 cm, or length L is at least about 2.0 cm, or length L is at least about 2.5 cm, or length L is at least about 3.0 cm. or length L is at least about 3.5 cm, or length L is at least about 4.0 cm, or length L is at least about 4.5 cm, or length L is at least about 5.0 cm, or length L is at least about 5.5 cm, or length L is at least about 6.0 cm, or length L is at least about 6.5 cm, or length L is at least about 7.0 cm, or length L is at least about 7.5 cm, or length L is at least about 8.0 cm, or length L is at least about 8.5 cm, or length L is at least about 9.0 cm, or length L is at least about 9.5 cm, or length L is at least about 10. S At least about 10.0 cm in length. In other examples, when the shaft 302 of the expander 300 occupies the sheath lumen 120 of the introducer sheath 100, the distal end of the distal tip 306 of the expander 300 can extend at least about 0.5 cm beyond the distal end of the distal tip 112 of the introducer sheath 100, or can extend at least about 1.0 cm, or at least about 1.5 cm, or at least about 2.0 cm, or at least about 2.5 cm, or at least about 3.0 cm, or at least about 3.5 cm, or at least about 4.0 cm, or at least about 4.5 cm, or at least about 5.0 cm.

[0043] In some examples, the shaft 302 of the dilator 300 can have a longitudinal cross-sectional dimension such that the shaft 302 can reversibly occupy the sheath lumen 120 of the introducer sheath 100 .

[0044] In an example, the first longitudinal expander section 308 and the second longitudinal expander section 310 can each include a blend of 0-95% polypropylene (PP) impact copolymer and 5-100% high performance elastomer, examples of which can include thermoplastic elastomers, such as thermoplastic olefins (TPO), thermoplastic polyurethanes (TPU), thermoplastic vulcanizates (TPV), polyester elastomers, polyamide elastomers (e.g., polyester block amide (PEBA)), nylon, polyethylene, and fluoropolymers (e.g., fluorinated ethylene propylene (FEP), perfluoroalkoxyalkane (PFA), and ethylene-tetrafluoroethylene (ETFE)).

[0045] refer to Figure 4 , shows a side view of another example of a dilator 400, the dilator 400 includes a shaft 402, the shaft including a wall defining a dilator lumen extending longitudinally through the shaft 402, the shaft 402 defining a second longitudinal axis 422, when the dilator 400 occupies the sheath lumen 120 of the introducer sheath 100, the second longitudinal axis 422 is coaxial with the first longitudinal axis 122 of the introducer sheath 100, the shaft 402 extends from a proximal end 404 to a distal tip 406, the shaft 402 includes a first longitudinal dilator section 410, a second longitudinal dilator section 412, The expander section 412 and the third longitudinal expander section 416, the second longitudinal expander section 412 is distal to the first longitudinal expander section 410, the third longitudinal expander section 416 is distal to the second longitudinal expander section 412, the first longitudinal expander section 410 has a first expander stiffness, the second longitudinal expander section 412 has a second expander stiffness less than the first expander stiffness, the third longitudinal expander section 416 has a third expander stiffness different from the second expander stiffness, the first longitudinal expander section 410 and the third longitudinal expander section 416 are arranged on the distal side of the second longitudinal expander section 412, the first longitudinal expander section 410 has a first expander stiffness, the second longitudinal expander section 412 has a second expander stiffness less than the first expander stiffness, the third longitudinal expander section 416 has a third expander stiffness different from the second expander stiffness, The second longitudinal expander section 412 is connected at the first expander transition portion 414, the second longitudinal expander section 412 and the third longitudinal expander section 416 are connected at the second expander transition portion 418, the shaft 402 can be made by butt-joining the first longitudinal expander section 410 to the second longitudinal expander section 412 and butt-joining the second longitudinal expander section 412 to the third longitudinal expander section 416, alternatively, the second longitudinal expander section 412 can be integral with the first longitudinal expander section 410, and The third longitudinal dilator section 416 can be integral with the second longitudinal dilator section 412, and the shaft 402 can be formed by a process such as full batch extrusion, wherein the shaft 402 is prepared such that the first longitudinal dilator section 410 has a first dilator stiffness, the second longitudinal dilator section 412 has a second dilator stiffness, and the third longitudinal dilator section 416 has a third dilator stiffness, the proximal end 404 is attached to the dilator hub 408, and the shaft 402 has a length L from the proximal end 404 to the distal tip 406 E , length LE The length of the tubular structure 104 of the introducer sheath 100 may be at least about 0.5 cm, or at least about 1.0 cm, or at least about 1.5 cm, or at least about 2.0 cm, or at least about 2.5 cm, or at least about 3.0 cm, or at least about 3.5 cm, or at least about 4.0 cm, or at least about 4.5 cm, or at least about 5.0 cm, or at least about 5.5 cm, or at least about 6.0 cm, or at least about 6.5 cm, or at least about 7.0 cm, or at least about 7.5 cm, or at least about 8.0 cm, or at least about 8.5 cm, or at least about 9.0 cm, or at least about 9.5 cm, or at least about 10.0 cm longer.

[0046] The third longitudinal expander section 416 has a longitudinal length L G When the expander 400 occupies the sheath lumen 120 of the introducer sheath 100, the distal tip 406 of the expander 400 may extend beyond the distal tip of the introducer sheath by more than about a length L G , less than about length L G or equal to approximately length L G , and the longitudinal distance that the distal tip 406 of the dilator 400 extends beyond the distal tip of the introducer sheath can correspond to at least about 0.5 cm, or at least about 1.0 cm, or at least about 1.5 cm, or at least about 2.0 cm, or at least about 2.5 cm, or at least about 3.0 cm, or at least about 3.5 cm, or at least about 4.0 cm, or at least about 4.5 cm, or at least about 5.0 cm.

[0047] The second longitudinal expander section 412 and the third longitudinal expander section 416 have a combined longitudinal length L F The second longitudinal expander section 412 has a F –L G The longitudinal length L of the second longitudinal expander section 412 F –L GThe sheath transition portion 110 may be longitudinally offset from each of the first dilator transition portion 414 and the second dilator transition portion 418 when the dilator 400 occupies the sheath lumen 120 of the introducer sheath 100. The sheath transition portion 110 may be longitudinally offset from the first dilator transition portion 414, and additionally or alternatively, the sheath transition portion 110 may be longitudinally offset from the second dilator transition portion 418 by a distance of at least about 0.1 cm, or at least about 0.2 cm, or at least about 0.3 cm, or at least about 0.4 cm, or at least about 0.5 cm, or at least about 0.6 cm, or at least about 0.7 cm, or at least about 0.8 cm, or at least about 0.9 cm, or at least about 1.0 cm, or at least about 1.1 cm. 1 cm, or at least about 1.2 cm, or at least about 1.3 cm, or at least about 1.4 cm, or at least about 1.5 cm, or at least about 1.6 cm, or at least about 1.7 cm, or at least about 1.8 cm, or at least about 1.9 cm, or at least about 2.0 cm, or at least about 2.1 cm, or at least about 2.2 cm, or at least about 2.3 cm, or at least about 2.4 cm, or at least about 2.5 cm, or at least about 2.6 cm, or at least about 2.7 cm, or at least about 2.8 cm, or at least about 2.9 cm, or at least about 3.0 cm, or at least about 3.1 cm, or at least about 3.2 cm, or at least about 3.3 cm, or at least about 3.4 cm, or at least about 3.5 cm, or at least about 3.6 cm. 6 cm, or at least about 3.7 cm, or at least about 3.8 cm, or at least about 3.9 cm, or at least about 4.0 cm, or at least about 4.1 cm, or at least about 4.2 cm, or at least about 4.3 cm, or at least about 4.4 cm, or at least about 4.5 cm, or at least about 4.6 cm, or at least about 4.7 cm, or at least about 4.8 cm, or at least about 4.9 cm, or at least about 5.0 cm, or at least about 5.1 cm, or at least about 5.2 cm, or at least about 5.3 cm, or at least about 5.4 cm, or at least about 5.5 cm, or at least about 5.6 cm, or at least about 5.7 cm, or at least about 5.8 cm, or at least about 5.9 cm, or at least about 6.0 cm, or at least about 6. 1 cm, or at least about 6.2 cm, or at least about 6.3 cm, or at least about 6.4 cm, or at least about 6.5 cm, or at least about 6.6 cm, or at least about 6.7 cm, or at least about 6.8 cm, or at least about 6.9 cm, or at least about 7.0 cm, or at least about 7.1 cm, or at least about 7.2 cm, or at least about 7.3 cm, or at least about 7.4 cm, or at least about 7.5 cm, or at least about 7.6 cm, or at least about 7.7 cm, or at least about 7.8 cm, or at least about 7.9 cm, or at least about 8.0 cm, or at least about 8.1 cm, or at least about 8.2 cm, or at least about 8.3 cm, or at least about 8.4 cm, or at least about 8.5 cm, or at least about 8.8 cm.6cm, or at least about 8.7cm, or at least about 8.8cm, or at least about 8.9cm, or at least about 9.0cm, or at least about 9.1cm, or at least about 9.2cm, or at least about 9.3cm, or at least about 9.4cm, or at least about 9.5cm, or at least about 9.6cm, or at least about 9.7cm, or at least about 9.8cm, or at least about 9.9cm, or at least about 1.0cm. .

[0048] The first longitudinal expander section 410 has a width corresponding to L E –L F , and may have such a length that when the expander 400 occupies the sheath lumen 120 of the introducer sheath 100, the distal surface 502 of the expander hub 408 may face or approach the proximal end 122 of the valve body 102 of the introducer sheath 100.

[0049] In some examples, the first expander stiffness can differ from the second expander stiffness by at least 5D, or at least 10D, or at least 15D, or at least 20D, or at least 25D, or at least 30D, or at least 35D, or at least 40D, or at least 45D, or at least 50D, or at least 55D, or at least 60D, or at least 65D, or at least 70D, or at least 75D, or at least 80D, or at least 85D, or at least 90D, or at least 95D. 5D, in a specific example, the first dilator stiffness can be greater than the first sheath stiffness and greater than 55D, or greater than 60D, or greater than 65D, or greater than 70D, or greater than 75D, in other specific examples, when the shaft 402 of the dilator 400 occupies the sheath lumen 120 of the introducer sheath 100 and the first dilator transition portion 414 is proximal to the sheath transition portion 110, the second dilator stiffness can be greater than the second sheath stiffness but less than the first sheath stiffness, in still other specific examples, when the shaft 402 of the dilator 400 occupies the sheath lumen 120 of the introducer sheath 100 When the sleeve cavity 120 and the first expander transition portion 414 are distal to the sheath transition portion 110, the second expander stiffness can be less than the second sheath stiffness, and can be less than 45D, or less than 40D, or less than 35D, or less than 30D, or less than 25D. In still other specific examples, the first expander stiffness can be about 56D, or about 58D, or about 60D, or about 62D, or about 64D, or about 66D, or about 68D, or about 70D, or about 72D, or about 74D, or about 76D, or about 78D, or about 80D, and ... The second expander stiffness can be about 55D, or about 54D, or about 52D, or about 50D, or about 48D, or about 46D, or about 44D, or about 42D, or about 40D, or about 38D, or about 36D, or about 34D, or about 32D, or about 30D, or about 28D, or about 26D, or about 24D, or about 22D, or about 20D. In other specific examples, the third expander stiffness can be less than the second expander stiffness. In other specific examples, the third expander stiffness is greater than the second expander stiffness and / or equal to the first expander stiffness.

[0050] Regardless of whether the first dilator transition section 414 is distal or proximal to the sheath transition section 110 when the dilator 400 occupies the sheath lumen 120 of the introducer sheath 100, by limiting the stiffness transition sections in the dilator 400 and including only a single stiffness transition section in the introducer sheath 100 and offsetting the first dilator transition section 414, the sheath transition section 110, and the second dilator transition section 418 longitudinally from each other, advantageously, these offset stiffness transition sections produce a combined effect of a series of stiffness transitions: from the highest in the first longitudinal dilator section 410 to the lowest in the sheath lumen 120. The offset stiffness transitions from a lower stiffness in the first longitudinal sheath segment 106, to a lower stiffness in the second longitudinal dilator segment 412 (or the second longitudinal dilator segment 108), and finally to a lowest stiffness in the second longitudinal sheath segment 108 (or the second longitudinal dilator segment 412, or the third longitudinal dilator segment 416), result in a transition that is advantageously unique to the operator of the introducer sheath 100 and the dilator 400 while minimizing the stiffness transitions in each of the introducer sheath 100 and the dilator 400.

[0051] In some examples, the shaft 402 of the dilator 400 can have a longitudinal cross-sectional dimension such that the shaft 402 can reversibly occupy the sheath lumen 120 of the introducer sheath 100 .

[0052] In an example, the first longitudinal expander segment 410, the second longitudinal expander segment 412 and the third longitudinal expander segment 416 can each include a blend of 0-95% polypropylene (PP) impact copolymer and 5-100% high-performance elastomer, examples of which can include thermoplastic elastomers, such as thermoplastic olefins (TPO), thermoplastic polyurethanes (TPU), thermoplastic vulcanizates (TPV), polyester elastomers, polyamide elastomers (e.g., polyester block amide (PEBA)), nylon, polyethylene and fluoropolymers (e.g., fluorinated ethylene propylene (FEP), perfluoroalkoxyalkane (PFA) and ethylene-tetrafluoroethylene (ETFE)).

[0053] refer to Figure 5 , illustrates a distal end view of the dilator 400 , showing the distal surface 502 of the dilator hub 408 in the background and the distal surface 504 of the distal tip 406 in the foreground, the shaft 402 including a wall defining a dilator lumen 506 .

[0054] refer to Figure 6 , showing a model tracking path 602 on a test bench 600, the model tracking path is used to analyze various medical devices for their ability to complete turns in the vascular system, in Figure 7, the straight lines intersecting the model tracking path 602, numbered in half-integer increments, indicate the number of turns (from 0.5 to 5.0 complete turns) that the medical device will complete at each straight line through the vasculature within the model tracking path 602. Table 1 below provides the average number of turns that each tested introducer sheath and dilator assembly can complete through the model tracking path 602 before the introducer sheath and dilator assembly will no longer advance further. As indicated in Table 1, the examples of the introducer sheath and dilator of the present disclosure completed an average of 4.7 complete turns, while the use of a standard introducer sheath and / or a standard dilator resulted in only 1-2.2 complete turns on average. Thus, the introducer sheath and dilator of the present disclosure demonstrated far superior performance of approximately 187.8% that outperformed commercially available sheaths and dilators.

[0055] Table 1

[0056]

[0057] refer to Figure 8 , showing a side view of the introducer sheath 100 and dilator 400 shown separately, in Fig. 9 , a side view of the introducer sheath 100 and the dilator 400 is shown, with the dilator 400 occupying the sheath lumen 120, and when the distal surface 502 of the distal end 420 of the dilator hub 408 of the dilator 400 faces or approaches the proximal end 122 of the valve body 102 of the introducer sheath 100, each of the first dilator transition section 414, the sheath transition section 110 and the second dilator transition section 418 are longitudinally offset from each other, and the distal end 406 extends beyond the distal end 112.

[0058] Although the present disclosure has been described with reference to the examples and the accompanying drawings, the present disclosure is not limited thereto but may be variously modified and altered by those skilled in the art without departing from the spirit and scope of the present disclosure.

[0059] The subject matter of the present disclosure may also relate to the following aspects:

[0060] A first aspect relates to a medical device, the medical device comprising: an introducer sheath, the introducer sheath comprising a tubular structure, the tubular structure comprising a wall defining a sheath lumen extending longitudinally through the tubular structure, the tubular structure defining a longitudinal axis passing therethrough, the tubular structure further comprising: a first longitudinal sheath segment having a first sheath stiffness; and a second longitudinal sheath segment distal to the first longitudinal sheath segment, the second longitudinal sheath segment having a second sheath stiffness less than the first sheath stiffness; and a sheath transition from the first longitudinal sheath segment to the second longitudinal sheath segment; and a dilator configured to occupy the sheath lumen, the dilator Comprising: an axis including a wall defining a dilator lumen extending longitudinally through the axis, the axis defining a second longitudinal axis, the second longitudinal axis being coaxial with the longitudinal axis when the dilator occupies the sheath lumen, the axis further comprising: a first longitudinal dilator section having a first dilator stiffness; and a second longitudinal dilator section distal to the first longitudinal dilator section, the second longitudinal dilator section having a second dilator stiffness less than the first dilator stiffness; and a dilator transition section from the first longitudinal dilator section to the second longitudinal dilator section; and wherein, when the dilator occupies the sheath lumen, the sheath transition section is longitudinally offset from the dilator transition section.

[0061] A second aspect relates to the medical device of aspect 1, wherein the first sheath stiffness is less than the first dilator stiffness.

[0062] A third aspect relates to the medical device of any preceding aspect, wherein the sheath transition portion is distal to the dilator transition portion.

[0063] A fourth aspect relates to the medical device of any preceding aspect, wherein the second dilator stiffness is less than the first sheath stiffness and greater than the second sheath stiffness.

[0064] A fifth aspect relates to the medical device of aspect 1 or 2, wherein the dilator transition portion is distal to the sheath transition portion.

[0065] A sixth aspect relates to the medical device of aspect 5, wherein the second dilator stiffness is less than the second sheath stiffness.

[0066] A seventh aspect relates to the medical device of any of the preceding aspects, wherein the second longitudinal sheath segment comprises a sheath distal tip at the distal end of the second longitudinal sheath segment; and wherein, when the dilator occupies the sheath lumen, the second longitudinal dilator segment is configured to extend distally at least one centimeter past the sheath distal tip.

[0067] An eighth aspect relates to the medical device of any preceding aspect, wherein the shaft further comprises a third longitudinal dilator section distal to the second longitudinal dilator section, the third longitudinal dilator section having a third dilator stiffness different from the second dilator stiffness.

[0068] A ninth aspect relates to the medical device of aspect 8, wherein the third expander stiffness is less than the second expander stiffness.

[0069] A tenth aspect relates to the medical device of aspect 8, wherein the third expander stiffness is greater than the second expander stiffness and / or equal to the first expander stiffness.

[0070] An eleventh aspect relates to the medical device of any preceding aspect, wherein the longitudinal dilator length is greater than the longitudinal sheath length.

[0071] A twelfth aspect relates to an introducer sheath, the introducer sheath comprising a tubular structure, the tubular structure comprising a wall defining a sheath lumen extending longitudinally through the tubular structure, the tubular structure defining a longitudinal axis passing therethrough, the tubular structure comprising: a first longitudinal sheath segment having a first sheath stiffness; a second longitudinal sheath segment distal to the first longitudinal sheath segment, the second longitudinal sheath segment having a second sheath stiffness less than the first sheath stiffness; and a longitudinal sheath segment extending from the first longitudinal sheath segment to the second longitudinal sheath segment. a sheath transition portion; wherein the expander is configured to occupy the sheath lumen such that the sheath transition portion is longitudinally offset from the expander transition portion from the first longitudinal expander section to the second longitudinal expander section; and wherein the expander comprises a shaft comprising: a wall defining a expander lumen extending longitudinally through the shaft; a first longitudinal expander section having a first expander stiffness; and a second longitudinal expander section distal to the first longitudinal expander section and having a second expander stiffness less than the first expander stiffness.

[0072] A thirteenth aspect relates to the introducer sheath of aspect 12, wherein the first sheath stiffness is less than the first dilator stiffness.

[0073] A fourteenth aspect relates to the introducer sheath of aspect 12 or 13, wherein the sheath transition portion is configured distal to the dilator transition portion.

[0074] A fifteenth aspect relates to the introducer sheath of any one of aspects 12 to 14, wherein the second dilator stiffness is less than the first sheath stiffness and greater than the second sheath stiffness.

[0075] A sixteenth aspect relates to the introducer sheath of aspect 12 or 13, wherein the dilator transition portion is configured distal to the sheath transition portion.

[0076] A seventeenth aspect relates to a dilator, the dilator comprising a shaft, the shaft comprising: a wall defining a dilator lumen extending longitudinally through the shaft; a first longitudinal dilator section having a first dilator stiffness; a second longitudinal dilator section distal to the first longitudinal dilator section, the second longitudinal dilator section having a second dilator stiffness less than the first dilator stiffness; and a dilator transition from the first longitudinal dilator section to the second longitudinal dilator section; wherein the dilator is configured to occupy a sheath of an introducer sheath lumen, such that a sheath transition from the longitudinal sheath segment to the second longitudinal sheath segment is longitudinally offset from the dilator transition segment; and wherein the introducer sheath comprises a tubular structure comprising: a wall defining a sheath lumen extending longitudinally through the tubular structure, the tubular structure defining a longitudinal axis passing therethrough, the tubular structure comprising: a first longitudinal sheath segment having a first sheath stiffness; and a second longitudinal sheath segment distal to the first longitudinal sheath segment and having a second sheath stiffness less than the first sheath stiffness.

[0077] An eighteenth aspect relates to the dilator of aspect 17, wherein the first sheath stiffness is less than the first dilator stiffness.

[0078] A nineteenth aspect relates to the dilator of aspect 17 or 18, wherein the sheath transition portion is configured distal to the dilator transition portion.

[0079] A twentieth aspect relates to the dilator of aspects 17 to 19, wherein the second dilator stiffness is less than the first sheath stiffness and greater than the second sheath stiffness.

[0080] In addition to the features mentioned in each of the above-enumerated independent aspects, some examples may also show, alone or in combination, optional features mentioned in the dependent aspects and / or as disclosed in the above description and shown in the drawings.

Claims

1. A medical device comprising: An introducer sheath comprising a tubular structure including a wall defining a sheath lumen extending longitudinally therethrough, the tubular structure defining a longitudinal axis therethrough, the tubular structure further comprising: a first longitudinal jacket section having a first jacket stiffness; and a second longitudinal jacket segment distal to the first longitudinal jacket segment, the second longitudinal jacket segment having a second jacket stiffness less than the first jacket stiffness; and a jacket transition from the first longitudinal jacket section to the second longitudinal jacket section; and a dilator configured to occupy the sheath lumen, the dilator comprising: a shaft including a wall defining a dilator lumen extending longitudinally therethrough, the shaft defining a second longitudinal axis coaxial with the longitudinal axis when the dilator occupies the sheath lumen, the shaft further comprising: a first longitudinal expander section having a first expander stiffness; and a second longitudinal dilator section distal to the first longitudinal dilator section, the second longitudinal dilator section having a second dilator stiffness less than the first dilator stiffness; and a dilator transition from the first longitudinal dilator section to the second longitudinal dilator section; and Wherein, when the dilator occupies the sheath lumen, the sheath transition portion is longitudinally offset from the dilator transition portion.

2. The medical device according to claim 1, wherein: The first sheath stiffness is less than the first dilator stiffness.

3. The medical device according to claim 1, wherein: The sheath transition portion is distal to the dilator transition portion.

4. The medical device according to claim 3, wherein: The second dilator stiffness is less than the first sheath stiffness and greater than the second sheath stiffness.

5. The medical device according to claim 1, wherein: The dilator transition portion is distal to the sheath transition portion.

6. The medical device according to claim 5, wherein: The second dilator stiffness is less than the second sheath stiffness.

7. The medical device according to claim 1, wherein: The second longitudinal sheath segment includes a sheath distal tip at a distal end of the second longitudinal sheath segment; and Wherein, when the dilator occupies the sheath lumen, the second longitudinal dilator section is configured to extend distally at least one centimeter past the sheath distal tip.

8. The medical device according to claim 1, wherein: The shaft further includes a third longitudinal dilator section distal to the second longitudinal dilator section, the third longitudinal dilator section having a third dilator stiffness different from the second dilator stiffness.

9. The medical device according to claim 8, wherein: The third expander stiffness is less than the second expander stiffness.

10. The medical device according to claim 8, wherein: The third dilator stiffness is greater than the second dilator stiffness and / or equal to the first dilator stiffness.

11. The medical device according to claim 1, wherein: The longitudinal dilator length is greater than the longitudinal sheath length.

12. An introducer sheath comprising a tubular structure including a wall defining a sheath lumen extending longitudinally therethrough, the tubular structure defining a longitudinal axis therethrough, the tubular structure comprising: a first longitudinal jacket section having a first jacket stiffness; a second longitudinal jacket segment distal to the first longitudinal jacket segment, the second longitudinal jacket segment having a second jacket stiffness less than the first jacket stiffness; and a jacket transition from the first longitudinal jacket section to the second longitudinal jacket section; wherein the dilator is configured to occupy the sheath lumen such that the sheath transition is longitudinally offset from a dilator transition from a first longitudinal dilator section to a second longitudinal dilator section; and Wherein, the expander includes a shaft, which includes: a wall, which defines a expander lumen extending longitudinally through the shaft; a first longitudinal expander section, which has a first expander stiffness; and a second longitudinal expander section, which is distal to the first longitudinal expander section and has a second expander stiffness less than the first expander stiffness.

13. The introducer sheath according to claim 12, wherein: The first sheath stiffness is less than the first dilator stiffness.

14. The introducer sheath according to claim 12, wherein: The sheath transition portion is configured distal to the dilator transition portion.

15. The introducer sheath of claim 14, wherein: The second dilator stiffness is less than the first sheath stiffness and greater than the second sheath stiffness.

16. The introducer sheath of claim 12, wherein: The dilator transition portion is configured distal to the sheath transition portion.

17. A dilator comprising a shaft, the shaft comprising: a wall defining a dilator lumen extending longitudinally through the shaft; a first longitudinal expander section having a first expander stiffness; a second longitudinal dilator section distal to the first longitudinal dilator section, the second longitudinal dilator section having a second dilator stiffness less than the first dilator stiffness; as well as an expander transition from the first longitudinal expander section to the second longitudinal expander section; wherein the dilator is configured to occupy a sheath lumen of an introducer sheath such that a sheath transition from a first longitudinal sheath segment to a second longitudinal sheath segment is longitudinally offset from the dilator transition; and Wherein, the introducer sheath comprises a tubular structure, which comprises: a wall defining a sheath lumen extending longitudinally through the tubular structure, the tubular structure defining a longitudinal axis passing therethrough, the tubular structure comprising: the first longitudinal sheath segment having a first sheath stiffness; and the second longitudinal sheath segment, which is distal to the first longitudinal sheath segment and has a second sheath stiffness less than the first sheath stiffness.

18. The dilator of claim 17, wherein: The first sheath stiffness is less than the first dilator stiffness.

19. The dilator of claim 17, wherein: The sheath transition portion is configured distal to the dilator transition portion.

20. The dilator of claim 19, wherein: The second dilator stiffness is less than the first sheath stiffness and greater than the second sheath stiffness.

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