an expandable introducer for widening the distal tip of the introducer sheath

Abstract

Expandable sheaths and introducers are disclosed herein. In some examples, the expandable introducer includes an elongate body member, an inflatable balloon disposed between a proximal end and a distal end of the elongate body member, and an inflation lumen in fluid communication with the inflatable balloon. A portion of the balloon passes through a distal opening of the expandable introducer sheath when in a deflated state and is sized and configured to widen the distal end of the introducer sheath when the balloon expands from the deflated configuration to an inflated configuration. Methods of making and using the devices disclosed herein are also disclosed.

Description

[Technical Field]

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 63 / 053,506, filed on 17 July 2020, entitled "Expandable Introducer for Dilating the Distal Tip of an Introducer Sheath," which is incorporated herein by reference.

[0002] This application relates to an expandable introducer sheath for the delivery of artificial devices such as transcatheter heart valves, and a method for manufacturing the same. [Background technology]

[0003] Intravascular delivery catheter assemblies are used to deliver surgical devices and prosthetic implants, such as prosthetic valves, to locations within the body that are not easily accessible by surgery or where access without invasive surgery is desirable. For example, aortic, mitral, tricuspid, and / or pulmonary prosthetic valves can be delivered to the treatment site using minimally invasive surgical techniques.

[0004] An introducer sheath can be used to safely introduce a delivery device into the patient's vascular structure (e.g., the femoral artery). An introducer sheath generally has a housing that includes an elongated sleeve inserted into the vascular structure along with the introducer, and one or more sealing valves that allow the delivery device to fluidly communicate with the vascular structure with minimal blood loss. Such an introducer sheath may be radially expandable. However, such sheaths tend to have complex mechanisms, such as ratchet mechanisms, that maintain the sheath in an expanded configuration when a device with a diameter larger than the sheath's original diameter is introduced. Furthermore, these introducer sheaths often include a compressed distal tip that is relatively rigid compared to the rest of the sheath body. The narrow, rigid distal tip may be formed by compressing and heat-bonding the material at the sheath tip. The bond between the material layers and / or folded / compressed material is configured to break during passage of the medical device, but this requires a strong pushing force, which can damage the medical device and pose a risk of trauma to the patient. In addition, in some procedures, the evacuation of medical devices for replacement / repositioning and / or removal of other devices is too large to fit through the distal opening of the sheath. For example, in the case of pre-BAV balloon aortic valve repair, the device passing through the tip is supplied with a diameter smaller than the diameter of the tip opening. The balloon may be delivered through a deflated introducer sheath having a diameter smaller than the diameter of the tip of the sheath (e.g., 10 Fr), so that the tip does not expand as the balloon passes distally through the sheath. After the pre-BAV procedure is completed, the diameter of the (deflated) balloon may be larger than the diameter of the compressed tip, making balloon evacuation difficult. Therefore, there remains a need in the art for improved introducer sheaths for intravascular systems used for the implantation of valves and other prosthetic devices. [Overview of the project]

[0005] An expandable introducer disclosed herein includes an elongated body member, an inflatable balloon positioned between the proximal and distal ends of the elongated body member, the balloon being expandable from a deflated configuration to an inflated configuration, and an expansion lumen fluidly communicating with the inflatable balloon, the expansion lumen being sized and configured to provide an expansion fluid to the balloon. In the deflated configuration, the outer diameter of the balloon corresponds to the outer diameter of the elongated body member, and in the inflated configuration, the outer diameter of the balloon is greater than the outer diameter of the elongated body member, and at least a portion of the balloon is sized and configured to pass through the distal opening of an expandable introducer sheath when the balloon is deflated, and the balloon is sized and configured to expand at least a portion of the distal end of the introducer sheath when the balloon expands.

[0006] Another expandable introducer sheath system disclosed herein is an expandable introducer sheath for deploying a medical device, an introducer, which is received within a central lumen of the introducer sheath and is movable axially and rotatably therein, the introducer comprising: an elongated body member having a proximal end and a tapered distal end; an inflatable balloon positioned between the proximal and distal ends of the elongated body member, the balloon being expandable from a deflated configuration to an inflated configuration; and an expansion lumen fluidly communicating with the inflatable balloon, the expansion being sized and configured to provide an expansion fluid to the balloon. In the deflated configuration, the outer diameter of the balloon corresponds to the outer diameter of the elongated body member, and in the inflated configuration, the outer diameter of the balloon is greater than the outer diameter of the elongated body member. At least a portion of the balloon is sized and configured to pass through the distal opening of the introducer sheath when the balloon is deflated, and as the balloon inflates, at least a portion of the distal end of the introducer sheath expands, increasing the diameter of the distal opening.

[0007] Methods for pre-broadening the tip of an introducer sheath are also disclosed herein. One example of pre-broadening the tip of an introducer sheath is to position an expandable introducer within a central lumen of an expandable sheath, wherein the introducer includes an elongated body member and an inflatable balloon positioned between the proximal and distal ends of the elongated body member, the balloon being expandable from a deflated configuration to an inflated configuration, where the initial diameter of the balloon in the deflated configuration corresponds to the outer diameter of the elongated body member, and where the inflated diameter of the balloon in the inflated configuration is greater than the outer diameter of the elongated body member; and an expansion lumen fluidly communicating with the inflatable balloon, where the expansion is sized and configured to provide an expansion fluid to the balloon. The method further includes advancing an introducer axially within the central lumen of a sheath such that an expandable balloon is axially aligned with the distal opening of the sheath; inflating the balloon to an inflated diameter such that the inflated diameter of the balloon is greater than the initial diameter of the distal opening, thereby expanding the diameter of the distal opening of the sheath; deflating the balloon; and withdrawing the introducer from the central lumen of the sheath.

[0008] A method for delivering a medical device using an expandable introducer is also disclosed herein. One example includes inserting an expandable sheath and an expandable introducer into the vascular structure of a patient, wherein the introducer is received within the central lumen of the sheath; advancing the introducer axially within the central lumen of the sheath such that an inflatable balloon positioned on the elongated body member of the introducer is axially aligned with the distal opening of the sheath; inflating the balloon to a diameter greater than the initial diameter of the distal opening, thereby expanding the diameter of the distal opening of the sheath; deflating the balloon; withdrawing the introducer from the central lumen of the sheath; advancing the medical device through the central lumen of the sheath; and delivering the medical device to the patient.

[0009] An expansion device configured to be received within an expandable sheath is also disclosed herein. The expansion device includes a body and a radially extending projection. The body includes an outer surface of the body, a proximal end, and a tapered distal end located opposite and spaced away from the proximal end. The radially extending projection is positioned along a portion of the body and includes the outer surface. The radially extending projection has a diameter greater than the diameter of the body. The device is sized and configured to be received within the central lumen of an expandable sheath such that the radially extending projection at least partially expands a portion of the expandable sheath.

[0010] A sheath system is also disclosed herein. The sheath system includes an expandable sheath and an expansion device. The expandable sheath comprises an inner layer defining the central lumen of the sheath and an outer layer extending at least partially around the inner layer. The inner and outer layers transition from an unexpanded configuration to an expanded configuration. The expansion device is movable within the central lumen of the sheath. The expansion device includes a body and a radially extending projection. The body includes an outer surface, a proximal end, and a tapered distal end located opposite and spaced away from the proximal end. The radially extending projection is positioned along a portion of the body and has an outer surface having a diameter greater than the diameter of the body. The reception of the expansion device within the central lumen of the sheath causes the sheath to locally expand at least a portion of the sheath in response to an outward-directed radial force provided by the radially extending projection.

[0011] A method for locally dilating an expandable sheath is also disclosed. The method includes introducing an expansion device into the central lumen of the expandable sheath, introducing the combined expandable sheath and expansion device into the patient's blood vessel, and advancing the expansion device distally within the central lumen of the expandable sheath to locally dilate the lumen of the sheath at a local axial position corresponding to the axial position of a radially extending projection provided to the expansion device.

[0012] Another method for locally dilating an expandable sheath is also disclosed. The method includes introducing an expandable sheath into a patient's blood vessel, wherein the expandable sheath has a central lumen; introducing an expansion device into the central lumen of the expandable sheath; and advancing the expansion device distally within the central lumen of the expandable sheath to locally dilate the lumen of the sheath at a local axial position corresponding to the axial position of a radially extending projection provided to the expansion device. [Brief explanation of the drawing]

[0013] Exemplary features and implementations are disclosed in the accompanying drawings. However, this disclosure is not limited to the exact configurations shown, and the drawings are not necessarily drawn to a specific scale.

[0014] [Figure 1] An example of a delivery system for cardiovascular prosthetic devices is shown. [Figure 2] An example of an expandable sheath that can be used in combination with the delivery system shown in Figure 1 is presented. [Figure 3] Figure 2 is a magnified view of a portion of the expandable sheath. [Figure 4] Figure 2 is a cross-sectional view of a portion of the expandable sheath. [Figure 5A] This is a magnified view of a portion of the expandable sheath shown in Figure 2, with the outer layer removed for illustrative purposes. [Figure 5B] Figure 2 is a magnified view of a portion of the braided layer of the sheath. [Figure 6] Figure 2 is a magnified view of a portion of the expandable sheath, showing the expansion of the sheath as the artificial device advances through it. [Figure 7] This is an enlarged partial cross-sectional view showing the constituent layers of the sheath of Figure 2, positioned on a mandrel. [Figure 8] This is a magnified view showing another example of an expandable sheath. [Figure 9]A cross-sectional view of an apparatus that can be used to form an expandable sheath, according to one example. [Figure 10A] Another example of a braided layer is shown where the filaments of the braided layer are configured to buckle when the sheath is in a radially folded state. [Figure 10B] Another example of a braided layer is shown where the filaments of the braided layer are configured to buckle when the sheath is in a radially folded state. [Figure 10C] Another example of a braided layer is shown where the filaments of the braided layer are configured to buckle when the sheath is in a radially folded state. [Figure 10D] Another example of a braided layer is shown where the filaments of the braided layer are configured to buckle when the sheath is in a radially folded state. [Figure 11] A side cross-sectional view of an assembly of an expandable sheath with a vascular dilator is shown. [Figure 12] A view showing the vascular dilator of the assembly example of FIG. 11. [Figure 13] A side view of another example of an assembly including an expandable sheath and a vascular dilator is shown. [Figure 14] A side view of the assembly example of FIG. 13 is shown where the vascular dilator is partially extruded from the expandable sheath. [Figure 15] A side view of the assembly example of FIG. 13 is shown where the vascular dilator is fully extruded from the expandable sheath. [Figure 16] A side view of the assembly example of FIG. 13 is shown where the vascular dilator is retracted into the expandable sheath. [Figure 17] A side view of the assembly example of FIG. 13 is shown where the vascular dilator is further retracted into the expandable sheath. [Figure 18] A side view of the assembly example of FIG. 13 is shown where the vascular dilator is fully retracted into the expandable sheath. [Figure 19] A side cross-sectional view of another example of an assembly including an expandable sheath and a vascular dilator is shown. [Figure 20] Examples of vascular dilators that can be used in combination with the expandable sheaths described herein are shown. [Figure 21] Examples of vascular dilators that can be used in combination with the expandable sheaths described herein are shown. [Figure 22] A cross-sectional side view is shown of an example of an expandable sheath having an outer cover and protruding parts. [Figure 23] An example of an outer cover with longitudinal scorelines is shown. [Figure 24] An example of a braided layer of an expandable sheath is shown, specifically the edge portion. [Figure 25A] A perspective view of an example of a roller-type crimping mechanism for crimping an expandable sheath is shown. [Figure 25B] Figure 25A shows a side view of the disc-shaped roller and connector of the crimping mechanism shown. [Figure 25C] Figure 25A shows a top view of the disc-shaped roller and connector of the crimping mechanism shown. [Figure 26] An example of a device for crimping a long, expandable sheath is shown. The circled portion of the device is enlarged in the inset on the left side of the drawing. [Figure 27] An example of an expandable sheath with an inner layer featuring scorelines is shown. [Figure 28] This shows an example of adding a braided layer to an expandable sheath. [Figure 29] A perspective view of an example of an additional expandable sheath is shown. [Figure 30] Figure 29 shows a perspective view of an example where the outer heat-shrinkable tube layer has been partially peeled away from the inner sheath layer. [Figure 31] This shows a side view of an example of a sheath before movement in a delivery system through the sheath. [Figure 32] A side view of an example of a sheath as the delivery system passes through and moves, splitting the heat-shrinkable tube layer. [Figure 33] A side view of an example sheath is shown, where the delivery system has completely passed through and moved, and the heat-shrinkable tube layer has completely split along the length of the sheath. [Figure 34] A perspective view of an example of a sheath with a distal end portion folded around the introducer is shown. [Figure 35] An enlarged cross-sectional view of the distal end portion folded around the introducer is shown. [Figure 36] A cross-section of an example of an additional expandable sheath is shown. [Figure 37] An example of a buffer layer is shown. [Figure 38] Here is another example of a buffer layer. [Figure 39] A side view of an example of an additional expandable sheath is shown. [Figure 40] Figure 39 shows a longitudinal cross-section of the example. [Figure 41] A cross-sectional view of an example of an additional expandable sheath is shown. [Figure 42] A partial longitudinal cross-section of an example of an additional expandable sheath is shown. [Figure 43] A cross-sectional view of an example of an additional expandable sheath in an expanded state is shown. [Figure 44] Figure 43 shows a cross-sectional view of an example of an expandable sheath during the crimping process. [Figure 45] A perspective view of an example of a sheath similar to the one in Figure 43, in an expanded state. [Figure 46] A perspective view of an example of a sheath similar to the one in Figure 43, in a folded and compressed state. [Figure 47] An example of adding a braided layer is shown. [Figure 48] This is an alternative cross-section of the sheath in Figure 2 in an unextended configuration. [Figure 49] This is an alternative cross-section of the sheath in Figure 2 in the extended configuration. [Figure 50] An example shows an expandable sheath combined with an expandable introducer. [Figure 51] Figure 50 is a magnified view of a portion of the expandable sheath and introducer. [Figure 52]Figure 50 is a magnified view of a portion of the expandable sheath and introducer. [Figure 53A] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53B] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53C] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53D] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53E] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53F] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53G] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53H] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53I] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 53J] Figure 50 shows a magnified view of a portion of the expandable introducer, accompanied by various balloon examples. [Figure 54] Figure 50 is an enlarged partial cross-sectional view showing the expandable introducer. [Figure 55] Figure 50 is an enlarged partial cross-sectional view showing the expandable introducer. [Figure 56] Figure 50 is an enlarged partial cross-sectional view showing the expandable introducer. [Figure 57] An exemplary side view of a delivery system for cardiovascular prostheses is shown. This is an enlarged partial cross section showing the expandable introducer of Figure 50. [Figure 58] A side view of an extension device in the form of an introducer is shown. [Figure 59] A side view of another example of an introducer-type extension device is shown. [Figure 60] Another example of an expansion device in the form of an introducer and a corresponding expandable sheath is shown. [Figure 61] Further examples of expansion devices in the form of an introducer and a corresponding expandable sheath are shown. [Figure 62] A side view of an extension device in the form of a dilator is shown. [Figure 63] A side view of another extension device in the form of a dilator is shown. [Figure 64] Examples of expansion devices in the form of dilators and corresponding expandable sheaths are shown.

[0015] Throughout the drawings, similar reference numbers are used to depict the same or similar elements, features, and structures. [Modes for carrying out the invention]

[0016] The expandable introducer sheaths described herein can be used to deliver an artificial device to a treatment site in the body through the patient's vascular structure. The sheath can be constructed to be highly expandable and foldable radially while limiting the axial elongation of the sheath, thereby limiting undesirable narrowing of the lumen. In one example, the expandable sheath includes a braided layer, one or more relatively thin inelastic polymer layers, and an elastic layer. The sheath can expand elastically from its original diameter to an expanded diameter as the artificial device advances through the sheath, and can return to its original diameter as the artificial device passes through under the influence of the elastic layer. In certain examples, one or more polymer layers can be engaged with the braided layer and configured to allow radial expansion of the braided layer while preventing axial elongation of the braided layer, otherwise elongation and narrowing of the sheath may occur.

[0017] Figure 1 shows a typical delivery device 10 for delivering a medical device, such as an artificial heart valve or other artificial implant, to a patient. The delivery device 10 is illustrative only and can be used in combination with any of the embodiments of the expandable sheaths described herein. Similarly, the sheaths disclosed herein can be used in combination with any of the various known delivery devices. The shown delivery device 10 may generally include an operable guide catheter 14 and a balloon catheter 16 extending through the guide catheter 14. The artificial device, such as an artificial heart valve 12, may be positioned at the distal end of the balloon catheter 16. The guide catheter 14 and the balloon catheter 16 may be fitted to slide longitudinally relative to each other to facilitate the delivery and positioning of the artificial heart valve 12 at the implantation site in the patient's body. The guide catheter 14 includes a handle portion 18 and an elongated guide tube or shaft 20 extending from the handle portion 18.

[0018] The artificial heart valve 12 is delivered into the patient's body in a radially compressed configuration and can be radially expanded to a radially expanded configuration at the desired deployment site. In the example shown, the artificial heart valve 12 is a plastically expandable artificial valve that is delivered into the patient's body in a radially compressed configuration on the balloon of a balloon catheter 16 (shown in Figure 1) and is subsequently radially expanded to a radially expanded configuration at the deployment site by inflating the balloon (or by activating another type of expansion device of the delivery device). Further details regarding plastically expandable heart valves that can be implanted using the devices disclosed herein are disclosed in U.S. Publication No. 2012 / 0123529, which is incorporated herein by reference. In other examples, the artificial heart valve 12 may be a self-expandable heart valve that is constrained in a radially compressed configuration by the sheath or other components of the delivery device and, when released by the sheath or other components of the delivery device, self-expands to a radially expanded configuration. Further details regarding self-expandable heart valves that can be implanted using the devices disclosed herein are disclosed in U.S. Publication No. 2012 / 0239142, which is incorporated herein by reference. In yet another embodiment, the artificial heart valve 12 may be a mechanically expandable heart valve comprising a plurality of struts connected by a hinge or pivot joint, and expandable from a radially compressed configuration to a radially expanded configuration by acting an expansion mechanism that applies an expansion force to the artificial valve. Further details regarding mechanically expandable heart valves that can be implanted using the devices disclosed herein are disclosed in U.S. Publication No. 2018 / 0153689, which is incorporated herein by reference. In yet another embodiment, the artificial valve may incorporate two or more of the above-described technologies. For example, a self-expandable heart valve may be used in combination with an expansion device that assists in the expansion of the artificial heart valve.

[0019] Figure 2 shows an example assembly 90 (which may be referred to as an introducer device or assembly) that can be used to introduce a delivery device 10 and an artificial device 12 into a patient's body. The introducer device 90 may comprise a housing 92 at the proximal end of the device and an expandable sheath 100 extending distally from the housing 92. The housing 92 can function as a handle for the device. The expandable sheath 100 has a central lumen 112 (Figure 4) for guiding the delivery device of the artificial heart valve through. Typically, during use, the distal end of the sheath 100 passes through the patient's skin and is inserted into a blood vessel, such as the femoral artery. The delivery device 10, with its implant 12, is then inserted through the housing 92 and sheath 100 and advanced through the patient's vascular structure to the treatment site where the implant is delivered and implanted in the patient. In certain examples, the introducer housing 92 may include a hemostatic valve that, when inserted through the housing, forms a seal around the outer surface of the guide catheter 14 to prevent leakage of pressurized blood.

[0020] In alternative examples, the introducer device 90 does not necessarily have to include the housing 92. For example, the sheath 100 may be an integral part of a component of the delivery device 10, such as a guide catheter. For example, the sheath may extend from the handle 18 of the guide catheter. Various exemplary sheaths are described herein. Similar reference numbers and names in various drawings indicate similar elements. Additional examples of introducer devices and expandable sheaths can be found in U.S. Patent Application No. 16 / 378,417 and U.S. Provisional Patent Application No. 62 / 912,569, filed on 8 October 2019 (also filed in International Patent Application PCT / US2020 / 054594), which are incorporated in their entirety by reference.

[0021] Figure 3 shows the expandable sheath 100 in more detail. Referring to Figure 3, the sheath 100 may have a natural unexpanded outer diameter D1. In certain examples, the expandable sheath 100 may comprise several coaxial layers extending along at least a portion of the sheath length L (Figure 2). Referring to Figure 4, for example, the expandable sheath 100 may include a first layer 102 (also referred to as the inner layer), a second layer 104 positioned around the first layer 102 and radially outward, a third layer 106 positioned around the second layer 104 and radially outward, and a fourth layer 108 (also referred to as the outer layer) positioned around the third layer 106 and radially outward. In the configuration shown, the inner layer 102 can define the lumen 112 of the sheath extending along the central axis 114.

[0022] Referring to Figure 3, when the sheath 100 is not expanded, the inner layer 102 and / or outer layer 108 can form longitudinally extending folds or creases such that the surface of the sheath has a plurality of ridges 126 (also referred to herein as “folds”). The ridges 126 can be spaced apart from each other circumferentially by longitudinally extending grooves 128. When the sheath expands beyond its original diameter D1, the ridges 126 and grooves 128 can become horizontal or incorporated as the surface expands radially and the circumference increases, as described further below. When the sheath 100 is folded back to its original diameter, the ridges 126 and grooves 128 can be reformed.

[0023] In certain examples, the inner layer 102 and / or the outer layer 108 may comprise relatively thin layers of polymer material. For example, in some sheaths 100, the thickness of the inner layer 102 may be 0.01mm to 0.5mm, 0.02mm to 0.4mm, or 0.03mm to 0.25mm. In certain examples, the thickness of the outer layer 108 may be 0.01mm to 0.5mm, 0.02mm to 0.4mm, or 0.03mm to 0.25mm.

[0024] In certain examples, the inner layer 102 and / or the outer layer 108 may comprise a lubricating, low-friction, and / or relatively inelastic material. In certain examples, the inner layer 102 and / or the outer layer 108 may comprise a polymer material having an elastic modulus of 400 MPa or greater. Exemplary materials may include ultra-high molecular weight polyethylene (UHMWPE) (e.g., Dyneema®), high molecular weight polyethylene (HMWPE), or polyether ether ketone (PEEK). With respect to the inner layer 102 in particular, such low-friction materials can facilitate the passage of artificial devices through the lumen 112. Other materials suitable for the inner and outer layers may include polytetrafluoroethylene (PTFE), stretched polytetrafluoroethylene (ePTFE), ethylene tetrafluoroethylene (ETFE), nylon, polyethylene, polyether block amide (e.g., Pebax), and / or any combination of the above. Some examples of the sheath 100 may include a lubricating liner on the inner surface of the inner layer 102. Examples of suitable lubricating liners include materials that can further reduce the coefficient of friction of the inner layer 102, such as PTFE, polyethylene, polyvinylidene fluoride, and combinations thereof. Other materials suitable for lubricating liners may also include those having a coefficient of friction of 0.1 or less, preferably.

[0025] In addition, some examples of the sheath 100 may include an external hydrophilic coating on the outer surface of the outer layer 108. Such a hydrophilic coating can facilitate the insertion of the sheath 100 into the patient's blood vessel and reduce potential damage. Examples of suitable hydrophilic coatings include Harmony® Advanced Lubrication Coating and other advanced hydrophilic coatings, available from SurModics, Inc. of Eden Prairie, Minnesota. DSM medical coatings (Koninklijke DSM NV, available from Heerlen, Netherlands) and other hydrophilic coatings (e.g., PTFE, polyethylene, polyvinylidene fluoride) are also suitable for use with the sheath 100. Such a hydrophilic coating can also be included on the inner surface of the inner layer 102 to reduce friction between the sheath and the delivery system, thereby facilitating use and improving safety. In some examples, hydrophobic coatings such as perylene may be used on the outer surface of the outer layer 108 or the inner surface of the inner layer 102 to reduce friction.

[0026] In certain examples, the second layer 104 may be a braided layer. Figures 5A and 5B show the sheath 100 with the outer layer 108 removed and the elastic layer 106 exposed. Referring to Figures 5A and 5B, the braided layer 104 may comprise a plurality of members or filaments 110 (e.g., metal or synthetic wire or fiber) braided together. The braided layer 104 may have any desired number of filaments 110, which can be oriented and braided together along any preferred number of axes. For example, referring to Figure 5B, the filaments 110 may include a first set of filaments 110A oriented parallel to a first axis A, and a second set of filaments 110B oriented parallel to a second axis B. The filaments 110A and 110B can be braided together in a biaxial braid such that the filaments 110A oriented along axis A form an angle θ with the filaments 110B oriented along axis B. In certain examples, the angle θ may be 5° to 70°, 10° to 60°, 10° to 50°, or 10° to 45°. In the example shown, the angle θ is 45°. In other examples, the filament 110 may also be oriented along three axes and braided into a triaxial braid, or oriented along any number of axes and braided into any preferred braid pattern.

[0027] The braided layer 104 may extend along the substantial total length L of the sheath 100, or it may extend only along a portion of the length of the sheath. In certain examples, the filament 110 may be a wire made from either a metal (e.g., Nitinol, stainless steel, etc.) or a variety of polymers or polymer composite materials, such as carbon fiber. In certain examples, the filament 110 may be circular and have a diameter of 0.01 mm to 0.5 mm, 0.03 mm to 0.4 mm, or 0.05 mm to 0.25 mm. In other examples, the filament 110 may have a flat cross-section with dimensions of 0.01 mm × 0.01 mm to 0.5 mm × 0.5 mm, or 0.05 mm × 0.05 mm to 0.25 mm × 0.25 mm. In one example, the filament 110 with a flat cross-section may have dimensions of 0.1 mm × 0.2 mm. However, other shapes and sizes are also suitable for certain examples. When using braided wire, the braiding density can be varied. Some examples have braiding densities of 10 to 80 picks per inch and can include 8, 16, or up to 52 wires in various braiding patterns. In other examples, the second layer 104 may be laser-cut from a tube or laser-cut, embossed, punched, etc., from a sheet material and rolled into a tubular structure. The layer 104 may also be woven or braided as desired.

[0028] The third layer 106 may be a stretchable elastic layer (also referred to as an elastic material layer). In certain examples, the elastic layer 106 may be configured to apply a force radially (for example, toward the central axis 114 of the sheath) with the underlying layers 102 and 104 as the delivery device passes through the sheath, causing the sheath to expand beyond its original diameter. In other words, the elastic layer 106 may be configured to apply an encircling pressure to the layers of the sheath beneath the elastic layer 106 to counteract the expansion of the sheath. A force oriented radially inward is sufficient to cause the sheath to fold radially after the delivery device has passed through it, returning it to its unexpanded state.

[0029] In the examples shown, the elastic layer 106 may comprise one or more members configured as strands, ribbons, or bands 116 helically wound around the braided layer 104. For example, in the examples shown, the elastic layer 106 comprises two elastic bands 116A and 116B wound in opposite helices around the braided layer, but the elastic layer may comprise any number of bands depending on the desired properties. The elastic bands 116A and 116B can be made from any of a variety of natural or synthetic elastomers, including silicone rubber, natural rubber, any variety of thermoplastic elastomers, and polyurethane, such as polyurethane siloxane copolymer, urethane, plasticized polyvinyl chloride (PVC), styrene block copolymer, and polyolefin elastomer. In some examples, the elastic layer may include an elastomer material having an elastic modulus of 200 MPa or less. In some examples, the elastic layer 106 may include a material exhibiting an elongation at break of 200% or more, or an elongation at break of 400% or more. The elastic layer 106 may also take other forms, such as an elastomer material, a tubular layer containing a mesh, or a shrinkable polymer layer, such as a heat-shrinkable tube layer. Instead of, or in addition to, the elastic layer 106, the sheath 100 may also include an elastomer or heat-shrinkable tube layer around the outer layer 108. Examples of such elastomer layers are disclosed in U.S. Publication No. 2014 / 0379067, U.S. Publication No. 2016 / 0296730, and U.S. Publication No. 2018 / 0008407, which are incorporated herein by reference. In other examples, the elastic layer 106 may also be radially outward of the polymer layer 108.

[0030] In certain examples, one or both of the inner layer 102 and / or the outer layer 108 may be configured to resist axial stretching of the sheath 100 when the sheath expands. More specifically, one or both of the inner layer 102 and / or the outer layer 108 may resist stretching due to longitudinal forces caused by friction between the artificial device and the inner surface of the sheath, such that the length L remains substantially constant when the sheath expands and contracts. Where used herein with respect to the length L of the sheath, the term “substantially constant” means that the length L of the sheath increases by 1% or less, 5% or less, 10% or less, 15% or less, or 20% or less. On the other hand, referring to Figure 5B, the filaments 110A and 110B of the braided layer may be able to move angularly relative to each other such that the angle θ changes when the sheath expands and contracts. This, combined with the longitudinal folds 126 of layers 102 and 108, may allow the lumen 112 of the sheath to expand as the artificial device advances through it.

[0031] For example, in some sheaths 100, the inner layer 102 and the outer layer 108 may be heat-joined during the manufacturing process such that the braided layer 104 and the elastic layer 106 are sealed between layers 102 and 108. More specifically, in certain examples, the inner layer 102 and the outer layer 108 may be bonded to each other through the spaces between the filaments 110 of the braided layer 104 and / or the spaces between the elastic bands 116. Layers 102 and 108 may also be joined or bonded together at the proximal and / or distal ends of the sheath. In certain examples, layers 102 and 108 are not bonded to the filaments 110. This allows the filaments 110 to move angularly relative to each other and to layers 102 and 108, making it possible to increase or decrease the diameter of the braided layer 104, and thus the diameter of the sheath. As the angle θ between filaments 110A and 110B changes, the length of the braided layer 104 may also change. For example, as the angle θ increases, the braided layer 104 can shrink, and as the angle θ decreases, the braided layer 104 can lengthen to a degree permitted by the region where layers 102 and 108 are joined. However, since the braided layer 104 is not bonded to layers 102 and 108, the change in the length of the braided layer with respect to the change in angle θ between filaments 110A and 110B does not result in a significant change in the sheath length L.

[0032] Figure 6 shows the radial expansion of the sheath 100 as the artificial device 12 passes through the sheath in the direction of arrow 132 (e.g., distal direction). As the artificial device 12 advances through the sheath 100, the sheath can expand elastically to a second diameter D2 corresponding to the size or diameter of the artificial device. As the artificial device 12 advances through the sheath 100, the artificial device can apply a longitudinal force to the sheath in the direction of motion due to the action of frictional contact between the artificial device and the inner surface of the sheath. However, as described above, the inner layer 102 and / or outer layer 108 can resist axial elongation so that the length L of the sheath remains constant or substantially constant. This reduces or prevents the braided layer 104 from lengthening, thereby reducing or preventing compression of the lumen 112.

[0033] On the other hand, the angle θ between filaments 110A and 110B can increase as the sheath expands to a second diameter D2 to accommodate the artificial valve. This can result in a reduction in the braided layer 104. However, since filaments 110 do not engage with or bond to layers 102 or 108, the shortening of the braided layer 104 due to the increase in angle θ does not affect the overall length L of the sheath. Furthermore, due to the longitudinally extending folds 126 formed in layers 102 and 108, layers 102 and 108 can expand to a second diameter D2 without breaking, despite being relatively thin and relatively inelastic. In this way, the sheath 100 can expand and contract elastically from its original diameter D1 to a second diameter D2, which is larger than diameter D1, without stretching or contracting as the artificial device advances through the sheath. Therefore, the force required to push the artificial implant through the sheath is greatly reduced.

[0034] In addition, due to the radial force applied by the elastic layer 106, the radial expansion of the sheath 100 can be localized to specific portions of the sheath occupied by the prosthetic device. For example, referring to Figure 6, as the prosthetic device 12 moves distally through the sheath 100, the portion of the sheath immediately proximal to the prosthetic device 12 can, under the influence of the elastic layer 106, radially fold back to its initial diameter D1. Layers 102 and 108 can also buckle as the circumference of the sheath decreases, resulting in the reformation of the ridges 126 and grooves 128. This can reduce the size of the sheath required to accommodate a given size prosthetic device. In addition, the temporary and local nature of the expansion reduces trauma to the blood vessel into which the sheath is inserted and the surrounding tissue, as only the portion of the sheath occupied by the prosthetic device expands beyond the sheath's original diameter and the sheath folds back to its initial diameter once the device has passed. This limits the amount of tissue that needs to be stretched to accommodate the prosthetic device and the amount of time that a given portion of the blood vessel must be widened.

[0035] In addition to the advantages described above, the examples of expandable sheaths described herein can offer remarkably superior performance compared to known introducer sheaths. For example, using a sheath configured as described herein, it is possible to deliver prosthetic devices having a diameter twice, 2.5 times, or even three times larger than the sheath's original outer diameter. For example, in one example, a crimped prosthetic heart valve having a diameter of 7.2 mm is successfully advanced through a sheath configured as described above, having an original outer diameter of 3.7 mm. As the prosthetic valve advances through the sheath, the outer diameter of the portion of the sheath occupied by the prosthetic valve increases to 8 mm. In other words, it is possible to advance a prosthetic device having a diameter more than twice the sheath's outer diameter through the sheath, during which the sheath's outer diameter is expanded by 216%. In another example, a sheath with an initial or original outer diameter of 4.5 mm to 5 mm can be configured to expand to an outer diameter of 8 mm to 9 mm.

[0036] In an alternative example, the sheath 100 may optionally include a layer 102 without layer 108, or a layer 108 without layer 102, depending on the desired specific characteristics.

[0037] Figures 10A-10D show another example of a braided layer 104 configured to buckle the filament 110. For example, Figure 10A shows a unit cell 134 of the braided layer 104 in a configuration corresponding to the braided layer in a fully expanded state. For example, the expanded state shown in Figure 10A can correspond to the diameter D2 and / or the diameter of the braided layer during the initial construction of the sheath 100 before the sheath is radially folded to its functional design diameter D1, as described above, and further described below with reference to Figure 7. The angle θ between filaments 110A and 110B can be, for example, 40°, and the unit cell 134 has a length L along the x-direction. x It can have (note that Cartesian coordinate axes are shown). Figure 10B shows a portion of the braided layer 104 containing an array of unit cells 134 in an expanded state.

[0038] In the example shown, the braided layer 104 is positioned between the polymer layers 102 and 108 as described above. For example, the polymer layers 102 and 108 can be bonded or laminated to each other at the end of the sheath 100 and / or between the filaments 110 in the open space 136 defined by the unit cell 134. Thus, referring to Figures 10C and 10D, when the sheath 100 is folded radially to its functional diameter D1, the diameter of the braided layer 104 can decrease as the angle θ decreases. However, the bonded polymer layers 102 and 108 can suppress or prevent the braided layer 104 from becoming longer when it is folded radially. This allows the filament 110 to buckle axially and stretchably, as shown in Figures 10C and 10D. The degree of buckling is determined by the length L of the unit cell 134. x However, the folded diameter of the sheath can be the same as, or substantially the same as, the fully expanded diameter. This means that the total length of the braided layer 104 remains constant as, or substantially constant as, the original diameter D1 of the sheath and the expanded diameter D2. As the sheath expands from its initial diameter D1 during the passage of the medical device, the filament 110 straightens out as the buckling is relieved, and the sheath can expand radially. As the medical device passes through the sheath 100, the braided layer 104 is pushed back to its initial diameter D1 by the elastic layer 106, and the filament 110 can again buckle elastically. Using the configurations in Figures 10A-10C, it is also possible to accommodate artificial devices having a diameter twice, 2.5, or even three times larger than the original outer diameter D1 of the sheath.

[0039] Referring here to a method for fabricating an expandable sheath, Figure 7 shows layers 102-108 of an expandable sheath 100 arranged on a cylindrical mandrel 118, according to one example. In a particular example, the mandrel 118 may have a diameter D3 that is larger than the desired original outer diameter D1 of the finished sheath. For example, in some examples, the ratio of the mandrel diameter D3 to the outer diameter D1 of the sheath may be 1.5:1, 2:1, 2.5:1, 3:1, or higher. In a particular example, the mandrel diameter D3 may be equal to the expanded diameter D2 of the sheath. In other words, the mandrel diameter D3 may be the same as, or approximately the same as, the desired expanded diameter D2 of the sheath as the artificial device advances through the sheath. Thus, in a particular example, the ratio of the expanded outer diameter D2 of the expanded sheath to the folded outer diameter D1 of the unexpanded sheath may be 1.5:1, 2:1, 2.5:1, 3:1, or higher.

[0040] Referring to Figure 7, the expandable sheath 100 can be fabricated by winding or arranging an ePTFE layer 120, followed by a first polymer layer 102, around a mandrel 118. In some examples, the ePTFE layer can help remove the sheath 100 from the mandrel 118 at the completion of the manufacturing process. The first polymer layer 102 may be in the form of a pre-assembled sheet applied by winding it around the mandrel 118, or it may be applied to the mandrel by dip coating, electrospinning, etc. A braided layer 104 may be located around the first layer 102, followed by an elastic layer 106. In examples where the elastic layer 106 includes one or more elastic bands 116, the bands 116 may be helically wound around the braided layer 104. In other examples, the elastic layer 106 may be dip coating, electrospinning, etc. Next, the outer polymer layer 108 can be wrapped around, positioned, or applied around the elastic layer 106, followed by another layer 122 of ePTFE and one or more layers 124 of heat shrink tubing or heat shrink tape.

[0041] In certain examples, the elastic band 116 can be applied to the braided layer 104 in a stretched, taut, or elongated state. For example, in certain examples, the band 116 can be applied to the braided layer 104 stretched to twice its natural relaxed length. This would cause the finished sheath to fold radially due to the influence of the elastic layer when removed from the mandrel, causing the corresponding relaxation of the elastic layer as described below. In other examples, the layers 102 and braided layer 104 can be removed from the mandrel, the elastic layer 106 can be applied in a relaxed or moderately stretched state, and then the assembly can be placed back on the mandrel so that the elastic layer is radially expanded and stretched to a taut state before the outer layer 108 is applied.

[0042] Next, the assembly may be heated to a temperature high enough to cause the heat-shrinkable layer 124 to shrink and compress layers 102-108 together. In certain examples, the assembly may be heated to a temperature high enough to cause the inner and outer polymer layers 102 and 108 to become flexible and tacky, bonding to each other in the open space between the braided layer 104 and the elastic layer 106, and encapsulating the braided and elastic layers. In other examples, the inner and outer layers 102 and 108 may be reflowed or melted so that they flow around and through the braided layer 104 and the elastic layer 106. In one example, the assembly may be heated at 150°C for 20-30 minutes.

[0043] After heating, the sheath 100 can be removed from the mandrel 118, and the heat shrink tubing 124 and ePTFE layers 120 and 122 can be removed. Once removed from the mandrel 118, the sheath 100 can be folded at least partially radially to its original design diameter D1 under the influence of the elastic layer 106. In certain examples, the sheath can be folded radially to the design diameter with the optional assistance of a crimping mechanism. The resulting reduction in circumference can cause the filament 110 to buckle together with the inner layer 102 and the outer layer 108, as shown in Figures 10C and 10D, forming a longitudinally extending fold 126.

[0044] In certain examples, a PTFE layer may be interposed between the ePTFE layer 120 and the inner layer 102, and / or between the outer layer 108 and the ePTFE layer 122, respectively, to facilitate the separation of the inner and outer polymer layers 102 and 108 from the ePTFE layers 120 and 122. In further examples, one of the inner layer 102 or the outer layer 108 may be omitted as described above.

[0045] Figure 8 shows another example of an expandable sheath 100, which includes one or more members configured as threads or cords 130 extending longitudinally along the sheath and attached to the braided layer 104. Although only one cord 130 is shown in Figure 8, in practice the sheath can include two, four, six, etc., cords arranged at equal angular intervals around the sheath. The cords 130 can be sutured to the outside of the braided layer 104, but other configurations and attachment methods are also possible. By being attached to the braided layer 104, the cords 130 may be configured to prevent axial stretching of the braided layer 104 as the prosthetic device passes through the sheath. The cords 130 can be used in combination with or separately from the elastic layer 106. The cords 130 can also be used in combination with one or both of the inner and / or outer layers 102 and 108, depending on the desired specific characteristics. The cords 130 may also be positioned inside the braided layer 104 (e.g., between the inner layer 102 and the braided layer 104).

[0046] The expandable sheath 100 can also be fabricated in other ways. For example, Figure 9 shows a device 200 including a containment vessel 202 and a heating system schematically shown in 214. The device 200 is particularly suitable for forming devices (medical devices or devices for non-medical applications) composed of two or more layers of material. The device formed by the device 200 can be formed from two or more coaxial layers of material, such as the sheath 100 or a shaft for a catheter. Alternatively, the device formed by the device 200 can be formed from two or more non-coaxial layers, such as two or more layers stacked on top of each other.

[0047] The containment vessel 202 can define the internal volume or chamber 204. In the example shown, the vessel 202 may be a metal tube including a closed end 206 and an open end 208. The vessel 202 can be at least partially filled with a thermally expandable material 210 having a relatively high coefficient of thermal expansion. In a particular example, the thermally expandable material 210 may have a coefficient of thermal expansion of 2.4 × 10⁻¹⁰. -4 It may have a thermal expansion coefficient of 5.9 × 10°C or greater. Examples of thermally expandable materials include elastomers such as silicone materials. Silicone materials have a thermal expansion coefficient of 5.9 × 10°C. -4 / ℃~7.9×10 -4 It can have a thermal expansion coefficient of / °C.

[0048] A mandrel similar to the mandrel 118 in Figure 7, including a desired combination of sheath material layers arranged around it, can be inserted into the thermally expandable material 210. Alternatively, the mandrel 118 can be inserted into the chamber 204, and the remaining volume of the chamber can be filled with the thermally expandable material 210 so that the mandrel is surrounded by the material 210. The mandrel 118 is shown schematically for illustrative purposes. Thus, the mandrel 118 may be cylindrical as shown in Figure 7. Similarly, the inner surface of the material 210 and the inner surface of the container 202 may have a cylindrical shape corresponding to the shape of the mandrel 118 and the final shape of the sheath 100. To facilitate the placement of a cylindrical or circular mandrel 118, the container 202 may comprise two parts connected to each other by a hinge, such that the two parts can move between an open configuration for positioning the mandrel inside the container and a closed configuration extending around the mandrel. For example, the upper and lower halves of the container shown in Figure 9 can be connected to each other by a hinge on the closed side of the container (the left side of the container in Figure 9).

[0049] The open end 208 of the container 202 can be closed with a cap 212. The container 202 can then be heated by a heating system 214. Heating by the heating system 214 expands the material 210 within the chamber 204 and applies radial pressure to the layers of material on the mandrel 118. The combination of heat and pressure can cause the layers on the mandrel 118 to join or bond to each other, forming a sheath. In certain examples, it is possible to apply a radial pressure of 100 MPa or more to the mandrel 118 using the apparatus 200. The amount of radial force applied to the mandrel can be controlled by, for example, the type and amount of material 210 selected, as well as its coefficient of thermal expansion, the thickness of the material 210 surrounding the mandrel 118, and the temperature at which the material 210 is heated.

[0050] In some examples, the heating system 214 may be an oven in which the container 202 is placed. In some examples, the heating system may include one or more heating elements arranged around the container 202. In some examples, the container 202 may be an electrically resistive heating element or an induction heating element controlled by the heating system 214. In some examples, the heating elements may be embedded in a thermally expandable material 210. In some examples, the material 210 may be configured as a heating element by adding a conductive filler material, such as carbon fibers or metal particles.

[0051] The apparatus 200 can offer several advantages over known sheath manufacturing methods, including the uniform and highly controllable application of radial force to the mandrel 118 along its length, and high repeatability. The apparatus 200 can also facilitate the rapid and precise heating of the thermally expandable material 210, reducing or eliminating the need for heat shrink tubing and / or tape, thereby reducing material costs and labor. The amount of radial force applied can also be varied along the length of the mandrel, for example, by changing the type or thickness of the surrounding material 210. In certain examples, multiple containers 202 can be processed with a single fixture, and / or multiple sheaths can be processed within a single container 202. The apparatus 200 can also be used to manufacture other devices such as shafts or catheters.

[0052] In one particular method, the sheath 100 can be formed by placing layers 102, 104, 106, and 108 on a mandrel 118, with the mandrel having the layers inside a container 202 in which a thermally expandable material 210 surrounds the outermost layer 108. If necessary, one or more inner layers 120 of ePTFE (or similar material) and one or more outer layers 122 of ePTFE (or similar material) can be used to facilitate the removal of the final sheath from the mandrel 118 and material 210 (as shown in Figure 7). The assembly is then heated in a heating system 214 to reflow layers 102, 108. During subsequent cooling, layers 102, 108 are at least partially joined to each other and layers 104, 106 are at least partially sealed.

[0053] Figure 11 shows another example in which the expandable sheath 100 is configured to receive a device configured as a pre-introducer or vascular dilator 300. In certain examples, the introducer device 90 may include the vascular dilator 300. Referring to Figure 12, the vascular dilator 300 may comprise a shaft member 302 including a tapered dilator member configured as a nose cone 304 located at the distal end portion of the shaft member 302. The vascular dilator 300 may further comprise a capsule or retaining member 306 extending proximal from the proximal end portion 308 of the nose cone 304 such that a circumferential space 310 is defined between the outer surface of the shaft member 302 and the inner surface of the retaining member 306. In certain embodiments, the retaining member 306 may be configured as a thin polymer layer or sheet, as further described below.

[0054] Referring to Figures 11 and 13, the first or distal end portion 140 of the sheath 100 can be received in the space 310 so that the sheath engages with the nose cone 304 and / or so that the retaining member 306 extends over the distal end portion 140 of the sheath. When in use, the connected or assembled vascular dilator 300 and sheath 100 can then be inserted into the blood vessel through the incision. The tapered conical shape of the nose cone 304 can help to gradually widen the blood vessel and access site while minimizing trauma to the blood vessel and surrounding tissue. Once the assembly has been inserted to the desired depth, the vascular dilator 300 can be advanced further into the blood vessel (e.g. distally) while the sheath 100 is held stably, as shown in Figure 14.

[0055] Referring to Figure 15, the vascular dilator 300 can be advanced distally through the sheath 100 until the retaining member 306 is removed beyond the distal end portion 140 of the sheath 100. In certain examples, the helically wound elastic layer 106 of the sheath can be terminated proximal to the distal end 142 of the sheath. Thus, if the distal end portion 140 of the sheath is not covered, the distal end portion (which may be heat-set) can be flared or expanded by increasing the diameter of the opening at the distal end 142 from a first diameter D1 (Figure 13) to a second larger diameter D2 (Figure 15). The vascular dilator 300 can then be withdrawn through the sheath 100, leaving the sheath 100 in place within the vascular vessel, as shown in Figures 16-18.

[0056] The vascular dilator 300 may include a variety of active and / or passive mechanisms for engaging and holding the sheath 100. For example, in certain examples, the retaining member 306 may comprise a polymer heat-shrinkable layer that can be folded around the distal end portion of the sheath 100. In the example shown in Figure 1, the retaining member may include an elastic member configured to compress the distal end portion 140 of the sheath 100. In yet another example, the retaining member 306 and the sheath 100 may be bonded or fused together (e.g., heat-bonded) in such a way that when a selected amount of force is applied, the adhesive bond between the retaining member 306 away from the sheath 100 breaks, allowing the vascular dilator to be pulled out. In some examples, the end portions of the braided layer 104 may be heat-set to flare or expand radially inward or outward to apply pressure to the corresponding portion of the vascular dilator 300.

[0057] Referring to Figure 19, the assembly may include a mechanically actuated retaining mechanism, such as a shaft 312 positioned between the dilator shaft member 302 and the sheath 100. In a particular example, the shaft 312 may be releasably connected to the sheath 100, allowing it to be actuated from outside the body (i.e., manually deactivated).

[0058] Referring to Figures 20 and 21, in some examples, the shaft 304 may comprise one or more balloons 314 arranged circumferentially around its outer surface and configured to engage with the sheath 100 when inflated. The balloons 314 can be selectively deflated to release the sheath 100 and withdraw the vascular dilator. For example, when inflated, the balloons press the captured distal end portion of the sheath 100 against the inner surface of the capsule 306, helping to hold the sheath in place relative to the vascular dilator. When the balloons deflate, the vascular dilator can move more easily relative to the sheath 100.

[0059] In another example, the expandable sheath configured as described above may further comprise a shrinkable polymer outer cover, such as a heat-shrinkable tubing layer 400 shown in Figure 22. The heat-shrinkable tubing layer 400 may be configured to allow a smooth transition between the vascular dilator 300 and the distal end portion 140 of the sheath. The heat-shrinkable tubing layer 400 may also constrain the sheath to a selected initial reduced outer diameter. In certain examples, the heat-shrinkable tubing layer 400 extends over the entire length of the sheath 100 and can be attached to the sheath handle by mechanical fastening means, such as clamps, nuts, adhesives, thermal welding, laser welding, or elastic clamps. In some examples, the sheath 100 is press-fitted to the heat-shrinkable tubing layer 400 during manufacturing.

[0060] In some examples, the heat-shrinkable tubing layer 400 can extend distally beyond the distal end portion 140 of the sheath 100 as a distal projection 408, as shown in Figure 22. The vascular dilator 300 can be inserted through the sheath membrane 112 beyond the distal edge of the projection 408. The projection 408 fits snugly to the inserted vascular dilator 300, providing a smooth transition between the diameter of the dilator and the diameter of the sheath, facilitating the insertion of the dilator 300 and sheath 100 combination. When the vascular dilator 300 is removed, the projection 408 remains in the vascular as part of the sheath 100. The heat-shrinkable tubing layer 400 offers the further advantage of shrinking the entire outer diameter of the sheath 100 along its longitudinal axis. However, it will be understood that some examples, such as the sheath 301 shown in Figure 42, may have a heat-shrinkable tube layer 401 that stops at the distal end of the sheath 301, or, in some examples, does not extend completely to the distal end of the sheath. In examples without a distal projection, the heat-shrinkable tube layer functions primarily as an outer shrinkage layer and is configured to maintain the sheath in a compressed configuration. Such examples would not result in a flapped projection at the distal end of the sheath when the dilator is retrieved.

[0061] In some examples, the heat shrink tubing layer 400 may be configured to split and open as a delivery device, such as a delivery device 10, advances through the sheath 100. For example, the heat shrink tubing layer 400 may have one or more longitudinally extending openings, slits, or weakened elongated score lines 406, as shown in Figure 22, configured to initiate the splitting of the layer at selected locations. As the delivery device 10 advances through the sheath 100, the heat shrink tubing layer 400 may continue to split and open, allowing the sheath to expand with reduced force as described above. In certain examples, the sheath 100 does not need to have an elastic layer 106 such that the sheath expands automatically from the outset and its diameter is reduced when the heat shrink tubing layer 400 splits and opens. The heat shrink tubing layer 400 may include polyethylene or other suitable materials.

[0062] Figure 23 shows an example of a heat-shrinkable tube layer 400 that can be arranged around an expandable sheath described herein. In some examples, the heat-shrinkable tube layer 400 may comprise a number of cuts or score lines 402 that extend axially along the tube layer 400 and terminate at distal stress-relieving features configured as circular openings 404. The distal stress-relieving features are intended to be configured as any other regular or irregular curved shapes, including, for example, oval and / or egg-shaped openings. Distal stress-relieving features of various shapes along and around the heat-shrinkable tube layer 400 are also intended. As the delivery device 10 advances through the sheath 100, the heat-shrinkable tube layer 400 can split and open along the score lines 402, and the distally positioned openings 404 can prevent further tearing or splitting of the tube layer along each score line 402. Thus, the heat-shrinkable tube layer 400 remains attached to the sheath 100 along the length of the sheath. In the example shown, the score lines 402 and associated openings 404 are offset from each other or staggered in the longitudinal and circumferential directions. Thus, as the sheath 100 expands, the score lines 402 can form a rhomboid structure. The score lines 402 can also extend in other directions, such as helically or in a zigzag pattern around the longitudinal axis of the sheath 100.

[0063] In other examples, the splitting or tearing of the heat-shrinkable tube layer 400 can be induced in various other ways, such as by applying a chemical solvent, cutting, notching, or excising the surface with an instrument or laser, and / or by reducing the wall thickness or creating a cavity in the tube wall (e.g., by femtosecond laser excision) to form a weakened region on the tube surface.

[0064] In some examples, the heat shrink tubing layer can be attached to the sheath body by adhesive, welding, or any other suitable fastening means. Figure 29 shows a perspective view of an exemplary sheath including an inner layer 802, a braided layer 804, an elastic layer 806, an outer layer 808, and a heat shrink tubing layer 809. Some examples may omit the elastic layer 806, as described below with respect to Figure 36. The heat shrink tubing layer 809 includes splits 811 and perforations 813 extending along the heat shrink tubing layer 809. The heat shrink tubing layer 809 is joined to the outer layer 808 at an adhesive seam 815. For example, in certain examples, the heat shrink tubing layer 809 may be joined at the seam 815 using welding, thermal bonding, chemical bonding, ultrasonic bonding, and / or adhesives (including, but not limited to, thermal adhesives such as LDPE fiber thermal adhesive). The outer layer 808 can be joined to the heat shrink tubing layer 809 at a seam 815 axially along the sheath, or in a spiral or helical manner. Figure 30 shows a sheath of the same example in which the heat shrink tubing layer 809 splits open at the distal end of the sheath.

[0065] Figure 31 shows a sheath with a heat shrink tubing layer 809, before the delivery system moves through it. Figure 32 shows a perspective view of the separated sheath, as the heat shrink tubing layer 809 is partially torn open and separated as the delivery system moves through, expanding the diameter of the sheath. The heat shrink tubing layer 809 is held in place by an adhesive seam 815. Adhering the heat shrink tubing layer 809 to the sheath in this manner can help maintain adhesion of the heat shrink tubing layer 809 to the sheath after the layer splits and the sheath expands, as shown in Figure 33, when the delivery system 817 moves completely through the sheath and tears the heat shrink tubing layer 809 along the entire length of the sheath.

[0066] In another example, the expandable sheath 100 may have a distal end or tip portion comprising an elastic thermoplastic material (e.g., Pebax), which may be configured to provide an interference fit or compression structure with the corresponding portion of the vascular dilator 300. In a particular configuration, the outer layer of the sheath 100 may include polyamide (e.g., nylon) for welding the distal end portion to the body of the sheath 100. In a particular example, the distal end portion 140 may have intentionally weakened sections, score lines, slits, etc., to allow the distal end portion 140 to split and separate as the delivery device 10 advances through the distal end portion 140.

[0067] In another example, the entire sheath 100 may have an elastomer outer cover that extends longitudinally from the handle to the distal end portion 140 of the sheath, and optionally extends forward to create a projection similar to the projection 408 shown in Figure 22. The elastomer projection fits tightly onto the vascular dilator 300, but remains part of the sheath when the vascular dilator 300 is removed. As the delivery system passes through, the elastomer projection expands and then folds down to allow it to pass. The elastomer projection, or the entire elastomer outer cover, may include intentionally weakened sections, score lines, slits, etc., to allow the distal end portion 140 to split and separate as the delivery device advances through the distal end portion 140.

[0068] Figure 24 shows the end (e.g., distal end) of another example of a braided layer 104, where portions 150 of the braided filaments 110 are bent to form loops 152 such that the filaments 110 loop in opposite directions along the sheath 100 or extend back. The filaments 110 can be arranged such that the loops 152 of various filaments 110 are offset axially from each other in the braid. As we move toward the distal end (to the right in the figure) of the braided layer 104, the number of braided filaments 110 can decrease. For example, the filament 110 indicated by 5 may first form a loop 152, followed by the filaments 110 indicated by 4, 3, and 2, with filament 110 forming the most distal loop 152. Thus, the number of filaments 110 in the braid decreases distally, which can increase the radial flexibility of the braided layer 104.

[0069] In another example, the distal end portion 140 of the expandable sheath 100 may contain a polymer such as Dyneema® that can be tapered to the diameter of the vascular dilator 300. Weakened portions, such as dashed cuts or incisions, may be applied to the distal end portion 140 so that it splits and opens and / or expands in a repeatable manner.

[0070] The crimping of the expandable sheath 100 examples described herein can be carried out in various ways as described above. In an additional example, the sheath 100 may be crimped several times longitudinally along a longer sheath 100 using a conventional short crimping machine. In another example, the sheath 100 may be folded to a specific crimped diameter in one or a series of steps in which the sheath is wrapped in heat shrink tubing and folded under heat. For example, a first heat shrink tubing may be applied to the outer surface of the sheath 100, the sheath 100 may be compressed to an intermediate diameter by shrinking the first heat shrink tubing (by heat), the first heat shrink tubing may be removed, a second heat shrink tubing may be applied to the outer surface of the sheath 100, the second heat shrink tubing may be compressed to a diameter smaller than the intermediate diameter by heat, and the second heat shrink tubing may be removed. This can be continued as many rounds as necessary to achieve the desired crimped sheath diameter.

[0071] The crimping of the various expandable sheath examples described herein can be carried out in various ways, as described above. A roller-based crimping mechanism 602, such as those shown in Figures 25A-25C, may be advantageous for crimping elongated structures such as the sheaths disclosed herein. The crimping mechanism 602 has a first end surface 604, a second end surface 605, and a longitudinal axis aa extending between the first and second end surfaces 604, 605. A plurality of disc-shaped rollers 606a-f are arranged radially around the longitudinal axis aa, each at least partially positioned between the first and second end surfaces of the crimping mechanism 602. Six rollers are illustrated in the example, but the number of rollers may vary. Each disc-shaped roller 606 is attached to a larger crimping mechanism by a connector 608. Side cross-sectional views of individual disc-shaped rollers 606 and connectors 608 are shown in Figure 25B, and top views of individual disc-shaped rollers 606 and connectors 608 are shown in Figure 25C. Each disc-shaped roller 606 has a circular edge 610, a first side surface 612, a second side surface 614, and a central axis cc extending between the center points of the first and second side surfaces 612 and 614, as shown in Figure 25C. The multiple disc-shaped rollers 606a to f are arranged radially around the longitudinal axis aa of the crimping mechanism 602 such that the central axis cc of each disc-shaped roller 606 is oriented perpendicular to the longitudinal axis aa of the crimping mechanism 602. The circular edge 610 of the disc-shaped roller partially defines a passage that extends axially through the crimping mechanism 602 along the longitudinal axis aa.

[0072] Each disc-shaped roller 606 is held in place in a radially arranged configuration by connectors 608 attached to the crimping mechanism 602 via one or more fasteners 619, such that the position of each of the multiple connectors is fixed relative to the first end surface of the crimping mechanism 602. In the example shown, the fasteners 619 are positioned radially outward of the disc-shaped roller 606, adjacent to the outer portion of the crimping mechanism 602. In the example shown, two fasteners 619 are used to position each connector 608, but the number of fasteners 619 can be changed. As shown in Figures 25B and 25C, the connector 608 has a first arm 616 and a second arm 618. The first and second arms 616, 618 extend over the disc-shaped roller 608, covering it from the radially outward portion of the circular edge 610 to the central portion of the disc-shaped roller 608. The bolt 620 extends through the first and second arms 616, 618 and through the central lumen of the disc-shaped roller 608, which passes along the central axis cc from the center point of the front surface 612 to the center point of the rear surface 614 of the disc-shaped roller 606. The bolt 620 is loosely positioned within the lumen with substantial clearance / space that allows the disc-shaped roller 608 to rotate around the central axis cc.

[0073] During use, the elongated sheath moves forward from the first side 604 of the crimping mechanism 602, through the axial passage between the rollers, to the second side 605 of the crimping mechanism 602. The pressure from the circular edge 610 of the disc-shaped roller 606 reduces the diameter of the sheath to the crimped diameter as it rotates along the outer surface of the elongated sheath.

[0074] Figure 26 shows an example of a crimping device 700 designed to facilitate the crimping of elongated structures such as sheaths. The crimping device includes an elongated base 704, an elongated mandrel 706 positioned on the elongated base 704, and a retaining mechanism 708 attached to the elongated base 704. The retaining mechanism 708 supports the mandrel 706 in a raised position on the base 704. The retaining mechanism includes a first end piece 710 containing a crimping mechanism 702. The mandrel 706 includes a conical end piece 712 that nests within a first tapered portion 713 of the narrowed lumen 714 of the first end piece 710. The conical end portion 712 of the mandrel 706 is loosely positioned within the narrowed lumen 714, providing sufficient space or gap between the conical end portion 712 and the lumen 714, allowing the elongated sheath to pass over the conical end portion 712 of the mandrel 706 and through the narrowed lumen 714. During use, the conical end portion 712 helps to avoid circumferential buckling of the sheath during crimping. In some examples, the mandrel 706 may also include a cylindrical end portion 724 that extends outward from the conical end portion 712 and defines the end portion 726 of the mandrel 706.

[0075] The first tapered portion 713 of the narrowed lumen 714 opens toward the second end piece 711 of the retaining mechanism 708 such that the widest side of the taper is located on the inner surface 722 of the first end piece 710. In the example shown, the first tapered portion 713 narrows down to a narrow end 715 that connects to the narrow cylindrical portion 716 of the narrowed lumen 714. In this example, the narrow cylindrical portion 716 defines the narrowest diameter of the narrowed lumen 714. The cylindrical end portion 724 of the mandrel 706 may be loosely nested within the narrow cylindrical portion 716 of the narrowed lumen 714 to allow sufficient space or clearance between the cylindrical end portion 724 of the lumen and the narrow cylindrical portion 716, and to allow the passage of an elongated sheath. The elongated nature of the narrowed cylindrical portion 716 can facilitate smoothing of the crimping sheath after it has passed through the conical end portion 712 of the mandrel. The length of the cylindrical portion 716 of the narrowed lumen 714 is not intended to limit the disclosure, and in some examples the crimping mechanism 702 may include only the first tapered portion 713 of the narrowed lumen 714 and still be effective for crimping an elongated sheath.

[0076] At the opposite end of the first end piece 710 shown in Figure 26, the second tapered portion 718 of the narrowed lumen 714 opens from the narrowed cylindrical portion 716 such that the widest side of the taper is located on the outer surface 720 of the first end piece 710. The narrowed end 719 of the second tapered portion 718 connects with the narrowed cylindrical portion 716 of the narrowed lumen 714 inside the crimping mechanism 702. The second tapered portion 718 of the narrowed lumen 714 may be omitted in some examples.

[0077] The retaining mechanism 708 further includes a second end piece 711 positioned opposite the first end piece 710 to the elongated base 704. The second end piece 711 is movable relative to the elongated base 704 so that the distance between the first end piece 710 and the second end piece 711 is adjustable, and thus it can support mandrels of various sizes. In some examples, the elongated base 704 may include one or more elongated sliding tracks 728. The second end piece 711 can be slidably engaged with the sliding track 728 via at least one reversible fastener 730, such as a bolt, which extends within or through the second end piece 711 and the elongated sliding track 728. To move the second end piece 711, the user loosens or removes the reversible fastener 730, slides the second end piece 711 to the desired position, and replaces or tightens the reversible fastener 730.

[0078] During use, the sheath at its uncrimped diameter may be positioned beyond the elongated mandrel 706 of the crimping device 700 shown in Figure 26, such that the inner surface of the entire length of the uncrimped sheath is supported by the mandrel. The uncrimped sheath then advances beyond the conical end portion 712 through the narrowing lumen 714 of the crimping mechanism 702. The uncrimped sheath is crimped to a smaller crimped diameter via pressure from the inner surface of the narrowing lumen 714. In some examples, the sheath advances through both the first tapered portion 713 and the cylindrical portion 716 of the narrowing lumen 714 before exiting the crimping mechanism 702. In some examples, the sheath advances through the first tapered portion 713, the cylindrical portion 716, and the second tapered portion 718 of the narrowing lumen 714 before exiting the crimping mechanism 702.

[0079] In some examples, the crimping mechanism 602 shown in Figure 25A may be located within a larger crimping device, such as the crimping device 700 shown in Figure 26. For example, the crimping mechanism 602 may be located within the first end piece 710 of the crimping device 700, either in place of or in combination with the crimping mechanism 702. For example, the roller crimping mechanism 602 may completely replace the narrowing lumen 714 of the crimping mechanism 702, such that the first tapered portion 713 supplies an expandable sheath through a plurality of radially arranged disc-shaped rollers 606, or the roller crimping mechanism 602 may be nested within the narrowing cylindrical portion 716 of the narrowing lumen 714 of the crimping mechanism 702.

[0080] Figures 34-35 show an exemplary sheath 100 including a distal end portion 902, which may be an extension of the outer cover that extends longitudinally along the sheath 100 in the proximal direction. Figure 34 shows the distal end portion 902 folded around the introducer 908 (crimped and folded configuration). Figure 35 shows a cross-section of the distal end portion 902 folded around the introducer 908 (crimped and folded configuration). The distal end portion 902 may be formed from one or more layers of similar or the same material used to form the outer layer of the sheath 100, for example. In some examples, the distal end portion 902 includes an extension of the outer layer of the sheath 100, having or not having one or more additional layers added by a separate processing technique. The distal end portion 902 may anywhere include 1 to 8 layers of material (including layers 1, 2, 3, 4, 5, 6, 7, and 8). In some examples, the distal end portion comprises multiple layers of Dyneema® material. The distal end portion 902 may extend distally beyond the longitudinal portion of the sheath containing the braided layer 904 and the elastic layer 906. In fact, in some examples, as shown in Figures 34-35, the braided layer 904 may extend distally beyond the elastic layer 906, and the distal end portion 902 may extend distally beyond both the braided layer 904 and the elastic layer 906.

[0081] The distal end portion 902 may have a smaller folded diameter than the more proximal portion of the sheath, giving it a tapered appearance. This ensures a smooth transition between the introducer / dilator 908 and the sheath 100, and that the sheath 100 does not press against tissue and prevent insertion into the patient. The smaller folded diameter may be the result of multiple folds (e.g., 1, 2, 3, 4, 5, 6, 7, or 8 folds) arranged circumferentially around the distal end portion. For example, circumferential segments of the distal end portion 902 can be brought together and then positioned against adjacent outer surfaces of the distal end portion 902 to create overlapping folds. In the folded configuration, the overlapping portions of the folds extend longitudinally along the distal end portion 902. Exemplary folding methods and configurations are described in U.S. Patent Application No. 14 / 880,109 (published as U.S. Patent No. 10,792,471) and U.S. Patent Application No. 14 / 880,111 (published as U.S. Patent No. 10,327,896), each of which is incorporated herein by reference in whole. Notches can be used as an alternative to, or in addition to, folding of the distal end portion 902. Both notches and folding of the distal end portion 902 allow for expansion of the distal end portion 902 as it passes through the delivery system and facilitates its retraction into the sheath 100 of the delivery system once the procedure is complete. In some examples, the distal end portion 902 of the sheath 100 (and / or vascular dilator) can be reduced from the initial diameter of the sheath (e.g., 8 mm) to 3.3 mm (10 F), and may be reduced to the diameter of the guidewire, allowing the sheath 100 and / or vascular dilator 300 to run on the guidewire.

[0082] In some examples, the distal end portion 902 may be added, the sheath 100 and the tip may be crimped, and the crimping of the distal end portion 902 and the sheath 100 may be maintained by the following method. As described above, the distal end portion 902 may be an extension of the outer layer of the sheath 100. It may also be a separate multilayer tube that is heat-bonded to the rest of the sheath 100 before the tip crimping process step. In some examples, a separate multilayer tube is heat-bonded to the distal extension of the outer layer of the sheath 100 to form the distal end portion 902. For crimping the sheath 100 after tip attachment, the sheath 100 is heated on a small mandrel. The distal end portion 902 may be folded around the mandrel to create the folded configuration shown in Figure 34. The folding is added to the distal end portion 902 before the tip crimping process or at an intermediate point during the tip crimping process. In some examples, the small mandrels may have diameters ranging from approximately 2 mm to approximately 4 mm (including approximately 2.2 mm, 2.4 mm, 2.6 mm, 2.8 mm, 3.0 mm, 3.2 mm, 3.4 mm, 3.6 mm, 3.8 mm, and 4.0 mm). The heating temperature will be lower than the melting point of the material being used. This may result in some degree of shrinkage of the material itself. For example, in an exemplary sheath where Dyneema® material is used as part of the outer layer and / or distal end portion 902 of the sheath 100, the sheath crimping process is initiated by heating the sheath 100 on a 3 mm mandrel to approximately 125 degrees Celsius (lower than the melting point of Dyneema®, which is approximately 140 degrees Celsius). This crimps the sheath 100 itself to an outer diameter of approximately 6 mm. At this point, it is possible to cool the sheath 100 and the distal end region 902. Next, a heat shrink tube may be applied. In some examples, the heat shrink tube may have a melting point that is approximately the same as the melting point of the material in the distal end portion 902.The sheath 100, having a heat-shrink tube extending over and covering the distal end portion 902, is heated again (e.g., to about 125 degrees Celsius for the sheath including the Dyneema® outer layer and distal end portion) to compress the sheath 100 to an even smaller diameter. At the distal end portion 902, a higher temperature (e.g., about 145 to 155 degrees Celsius for the Dyneema® material) can be applied to bring the layers of material together in the folded configuration shown in Figure 34 (folding can be applied at any point during this process). The joint at the distal end portion 902 induced by the high-temperature melting step will still be weak enough to be destroyed by the through-delivery system. As a final step, the heat-shrink tube is removed, and the shape of the sheath 100 remains the compressed diameter.

[0083] Figure 43 shows a cross-section taken near the distal end of another sheath example, at a point longitudinally distal to the braided layer. The sheath 501 includes an inner polymer layer 513, an outer polymer layer 517, and an outer cover 561. A method for compressing the distal portion of an expandable sheath 501 may include: covering the distal portion of the expandable sheath 501 in a pre-compressed state with an outer cover layer 561 having a melting temperature TM1 lower than the melting temperature TM2 of the inner and outer polymer layers; heating at least one region that does not extend to the entire overlapping region between the cover layer 561 and the expandable sheath 501 to a first temperature of TM2 or higher, thereby melting both the cover layer 561 and the outer polymer layer 517 of the expandable sheath 501 and forming an adhesion region 569 between them; inserting a mandrel into the lumen of the expandable sheath 501 and compressing at least a portion thereof, such as the distal portion of the expandable sheath 501; and heating the outer cover layer 561 covering the distal portion of the expandable sheath 501 to a second temperature that is of TM1 or higher than the melting temperature TM1 of the outer cover layer 561 and lower than the melting temperature TM2 of the inner and outer polymer layers, within a predefined first time window.

[0084] This method advantageously avoids the risk that a tear initiated at a cut or split line (such as perforation 813 shown in Figure 29) will deviate from the intended axial direction of tear propagation due to defects in the heat-shrink tubing (weak points or unintended openings). This method further allows for the selection of an outer cover layer made of a material that can be heated at a lower temperature than required for the inner or outer layer of the expandable sheath to form moderately adhered folds.

[0085] The crimping of the inner and outer polymer layers (e.g., inner and outer layers 513, 517) and the outer cover layer (e.g., layer 561) can result in a compressed diameter of approximately 3 mm from, for example, a pre-compression diameter of approximately 8.3 mm. Figure 44 shows a cross-sectional view of the example in Figure 43 during crimping. The fold 563 is formed along the outer layer 561 during crimping. Heating to a second temperature is sufficient to melt the outer cover layer 561 so that the folds 563 adhere to each other, while avoiding similar melting and adhesion of the inner and outer polymer layers.

[0086] A method for compressing the distal portion of an expandable sheath may further include the step of covering the expandable sheath 501 and the outer cover layer 561 with a heat shrink tubing (HST) before, during, or after heating to a second temperature, the second temperature further acting to shrink the HST in order to hold the outer cover layer 561 and the expandable sheath 501 in a compressed state. The HST can be removed from the expandable sheath 501 and the outer cover layer 561 after the folds 563 of the cover layer 563 are sufficiently attached to each other in the desired compressed state and after a sufficient period of cooling.

[0087] In some examples, the HST is further utilized as a heat shrink tape, applying external radial pressure by wrapping it over the outer cover layer 561 and the expandable sheath 501 and heating it. In some examples, a non-heat shrink tape can be used instead of a heat shrink tube.

[0088] Figure 45 shows the distal portion of an expandable sheath 501 having an expandable braid 120, which is covered by an outer cover layer 561 that extends along length L1 to the distal end 513 of the expandable sheath 501. D1 is the distal diameter of the expandable sheath 501 before compression. Figure 6B shows the distal portion of the expandable sheath 501 in the compressed state, where its distal diameter D2 is smaller than D1. It should be noted that compressing the outer cover layer 561 from the uncompressed state to the compressed state of the expandable sheath 501 results in the formation of folds 563 (Figures 44 and 46) along the outer cover layer 561, as well as layers 517 and 513, and that its diameter is reduced when it reaches the compressed state. It is desirable to promote adequate adhesion between the folds 563. As used herein, the term “moderate adhesion” refers to an adhesion force that forms a structural cover that keeps the expandable sheath 501 in a compressed state before the DS component advances through its lumen, and is further low enough (Figure 44) to break or detach the adhesion 565 between the folds 563, thereby allowing the DS component to pass through, and is large enough to allow the expandable sheath 501 to expand.

[0089] The outer cover layer 561 is selected such that its melting temperature TM1 is lower than the melting temperature TM2 of the polymer layers of the expandable sheath 100, in order to promote the formation of folds 563 with moderate adhesion to the outer cover layer 561, while avoiding similar folds melting and adhering to the polymer layers 513 and 517 of the expandable sheath 501.

[0090] According to some examples, the outer cover layer 561 is low-density polyethylene. The outer cover layer 561 can be formed using other suitable materials known in the art, such as polypropylene or thermoplastic polyurethane.

[0091] Figures 45 and 46 show perspective views of the same or identical exemplary sheath as those in Figures 43 and 44. The outer cover layer 561 and the expandable sheath 501 were heated to a first temperature TM2 along the circumferential interface between them at the proximal end of the outer cover layer 561, forming a circumferential proximal adhesion region 569.

[0092] In some examples, the outer cover layer 561 is attached to the outer surface of the expandable sheath 501 (e.g., the outer polymer layer) in different attachment regions, such as along longitudinally oriented attachment lines. In some examples, the outer cover layer 561 is attached to the outer surface of the expandable sheath 501 by a plurality of circumferentially spaced attachment regions 569, 571, where the circumferential distance between adjacent attachment regions is selected to allow for the formation of folds 573 between them. The attachment regions 569, 571 ensure that the outer cover layer 561 remains attached to the expandable sheath 501 at all times, whether in its compressed or expanded state.

[0093] According to some examples, covering with the outer cover layer 561 is performed after the expandable sheath 501 has been crimped so that the outer layer 561 covers the pre-formed folds of the inner layer 513 and / or outer layer 517 of the sheath 501.

[0094] According to some examples, the joining between the folds 563 is based on adhesion with moderate adhesive strength.

[0095] Examples of sheaths described herein may include various lubricating external coatings, including hydrophilic or hydrophobic coatings and / or surface blooming additives or coatings.

[0096] Figure 27 shows another example of a sheath 500 having a tubular inner layer 502. The inner layer 502 may be formed from an elastic thermoplastic material such as nylon and may have a number of cuts or score lines 504 along its length so that the tubular layer 502 is divided into a number of long, thin ribs or sections 506. As the delivery device 10 advances through the tubular layer 502, the score lines 504 can elastically expand or open, thereby spreading the ribs 506 apart and increasing the diameter of the layer 502 to accommodate the delivery device.

[0097] In other examples, the scoreline 504 may be configured as openings or cutouts having various geometric shapes, such as rhombuses, hexagons, or combinations thereof. In the case of a hexagonal opening, the opening may be an irregular hexagon with a relatively long axial dimension to reduce sheath shortening during expansion.

[0098] The sheath 500 may contain a relatively low durometer, thermoplastic material (e.g., Pebax, polyurethane, etc.) and may further include an outer layer (not shown) that can be bonded to the inner nylon layer (e.g., by bonding or welding, such as by thermal or ultrasonic welding). Attaching the outer layer to the inner layer 502 can reduce the axial movement of the outer layer relative to the inner layer during radial expansion and folding of the sheath. The outer layer may also form the distal end of the sheath.

[0099] Figure 28 shows another example of a braided layer 600 that can be used in combination with any of the sheath examples described herein. The braided layer 600 may comprise a plurality of braided portions 602 in which the filaments of the braided layer are braided together, and unbraided portions 604 in which the filaments are not braided and extend axially without entanglement. In certain examples, the braided portions 602 and unbraided portions 604 may be alternating along the length of the braided layer 600 or incorporated into any other suitable pattern. The ratio of the lengths of the braided layer 600 given to the braided portions 602 and unbraided portions 604 may allow for selection and control of the expansion and contraction characteristics of the braided layer.

[0100] Figure 47 depicts an example of a braided layer 601 having at least one radiopaque strut or filament. The expandable sheath 601 and its expandable braided layer 621 are shown without a polymer layer for illustrative purposes, as they are visualized by X-ray fluorescence fluoroscopy. As shown in Figure 47, the expandable braided layer 621 comprises a plurality of crossing struts 623 that can further form a distal crown 633, for example, in the form of distal loops or eyelets in the distal portion of the expandable sheath 601.

[0101] The expandable sheath 601 is configured to advance, for example, along the abdominal aorta or aortic bifurcation, in a pre-compressed state to a target region, at which point the physician needs to halt further advancement and introduce DS through its lumen to facilitate its expansion. For this purpose, the physician needs to receive real-time indication of the position of the expandable sheath as it advances. According to one aspect of the present disclosure, at least one radiopaque marker is provided in or along at least one region of the expandable braided layer 621, and is configured to allow visualization of the position of the expandable sheath under radiofluoroscopy.

[0102] In one example, at least one of the distal crowns 633 includes a radiopaque marker. In some examples, the distal crown 633 includes at least one gold-plated crown 635 (Figure 47) configured to function as a radiopaque marker. Gold plating is merely an example, and it will be apparent that the crown 635 may include other radiopaque materials known in the art, such as tantalum, platinum, or iridium.

[0103] Since the expandable sheath 601 includes an expandable braided layer 621 having a plurality of transverse struts 623 arranged along its length, this structure can be advantageously utilized for more convenient incorporation of radiopaque elements.

[0104] In some examples, a strut 623 further comprises at least one radiopaque strut 625 having a radiopaque core. For example, a drawn-filled tube (DFT) wire containing a gold core (such as one that may be provided by Fort Wayne Metals Research Products Corp.) can function as a radiopaque strut 625. Figure 47 shows an exemplary expandable braided layer 621 comprising multiple low-opacity struts or filaments 623, as well as radiopaque struts or filaments 625a, 625b, and 625c. In some cases, struts 625a and 625c can be fabricated from a single wire, which extends along the path of strut 625a, loops at the distal crown 635, and extends from there along the path of strut 625c. Thus, a single wire, such as a DFT wire, can be used to form radiopaque struts 625a and 625c, as well as the radiopaque distal crown 635.

[0105] Since radiopaque wires such as DFT wires can be costly, the expandable braided layer 621 may be made of, for example, a shape memory alloy such as nitinol and a polymer wire such as PET, and may comprise multiple radiopaque or less radiopaque struts 623 intertwined with at least one radiopaque strut 625 (Figure 47).

[0106] According to some examples, radiopaque wires are embedded within polymer braids such as an outer polymer layer 617 or an inner polymer layer 615, which are made of a low-opacity material.

[0107] Advantageously, an expandable braid embedded within an expandable sheath is utilized in accordance with this disclosure to incorporate radiopaque markers along specific portions thereof to improve real-time visualization of the sheath's position under fluoroscopy.

[0108] According to yet another aspect of this disclosure, the radiopaque tube can be screwed into the distal crown or loop 633, or the radiopaque rivet can be stretched onto the distal crown or loop 633 to improve visibility under radiography.

[0109] Figure 36 shows a longitudinal cross-section of another example of an expandable sheath 11 (placed on a mandrel 91 during the manufacturing process under compression by a heat-shrinkable tube 51). The sheath 11 comprises a braided layer 21 but lacks the elastic layer described in the previous example. The heat applied during the shrinking procedure can facilitate at least partial melting of the inner 31 and outer 41 polymer layers. As the filaments of the braid define continuous cells among them, the inner 31 and outer 41 polymer layers melt into the cell openings and cover the filaments of the braided layer 21, potentially forming an uneven outer surface.

[0110] To mitigate uneven surface formation, buffer polymer layers 61a and 61b are added between the inner layer 31 and the outer layer 41 of the sheath 11, configured to uniformly distribute the radially acting forces during sheath compression. The first buffer layer 61a is positioned between the inner polymer layer 31 and the braided layer 21, and the second buffer layer 61b is positioned between the outer polymer layer 41 and the braided layer 21.

[0111] The buffer layers 61a and 61b may include porous materials having multiple micropores of nanopores 63 (Figures 37-38) in their porous internal regions. One such material is, but is not limited to, stretched polytetrafluoroethylene (ePTFE). The porous buffer layers can be advantageously formed with the minimum thickness h1 necessary to sufficiently spread compressive forces and prevent non-uniform surface formation along the inner 31 and outer 41 polymer layers. The thickness h1 is measured radially (from the inner surface to the outer surface) of the buffer layer and can range from approximately 80 microns to approximately 1000 microns (e.g., including approximately 80 microns, 90 microns, 100 microns, 110 microns, 120 microns, 130 microns, 140 microns, 150 microns, 160 microns, 170 microns, 180 microns, 200 microns, 250 microns, 300 microns, 350 microns, 400 microns, 450 microns, 500 microns, 550 microns, 600 microns, 650 microns, 700 microns, 750 microns, 800 microns, 850 microns, 900 microns, 950 microns, and approximately 1000 microns). In some examples, the thickness h1 ranges from approximately 110 to 150 microns.

[0112] However, if the buffer layer contains multiple micropores of nanopores 63 (Figures 37-38), the inner 31 and outer 41 polymer layers may melt into the pores of the buffer layers 61a and 61b when heated during the manufacturing process. To prevent the inner 31 and outer 41 polymer layers from melting into the pores 63 of the buffer layer 61, a first sealing layer 71a can be placed between the inner polymer layer 31 and the first buffer layer 61a, and a second sealing layer 71b can be placed between the outer polymer layer 41 and the second buffer layer 61b (as shown in Figure 36). The sealing layers 71a and 71b may have a higher melting point than the polymer layers 31 and 41 and may be formed from a non-porous material (such as, but not limited to, polytetrafluoroethylene) to prevent fluid flow through them. The thickness h2 of each sealing layer 71 (Figure 37) is measured radially from the inner surface to the outer surface of the sealing layer and can be much thinner than the thickness of the buffer layer 61, for example, up to about 15 to about 35 microns (including about 15 microns, about 20 microns, about 25 microns, about 30 microns, and about 35 microns).

[0113] While advantageous for the reasons stated above, adding buffers and seals can increase the complexity and time required to assemble the sheath 11. Advantageously, by providing a single sealed buffer member configured to provide both buffering and sealing functions (instead of providing two separate buffer and sealing layers, each configured to provide one function), the assembly time of the sheath is reduced and the process is significantly simplified. According to one aspect of the present disclosure, a single sealed buffer member is provided, configured to be positioned between the inner and outer polymer layers and a central braided layer of the sheath. The single sealed buffer member includes a buffer layer and a sealing surface configured to prevent leakage / melting into radial pores.

[0114] Figure 37 shows an example of a single sealed buffer member 81', which includes a buffer layer 61 having a width and thickness h1 as detailed herein, fixedly attached to a corresponding sealing layer 71 having a thinner thickness h2 to form a sealing surface. The sealing layer 71 and the buffer layer 61 are pre-assembled or pre-attached to each other to form a single member 81' together, for example by bonding, welding, etc.

[0115] Figure 38 shows an example of a single sealed buffer member 81 including a buffer layer 61 having a width and thickness h1, the buffer layer 61 being provided with at least one sealing surface 65 configured to face an inner 31 or outer 41 polymer layer when assembled within the sheath 11. According to some examples, the sealing surface 65 may be formed by a surface treatment configured to fluidly seal the surface of the buffer layer 61. Thus, the sealing surface 65 may be made of the same material as the buffer layer 61.

[0116] According to another aspect of the present disclosure, as described above with respect to Figure 36, at least three layers may be sufficient to maintain the expandability of the sheath, providing favorable resistance to axial elongation. This is achieved by eliminating the need to incorporate additional elastic layers within the sheath, thereby favorably reducing manufacturing costs and simplifying the manufacturing process. The sheath does not necessarily need to return to its initial diameter, but if there is no elastic layer, it may remain at the expanded diameter during passage through the valve.

[0117] Figures 39-40 show an expandable sheath 101 similar to the expandable sheath 100 shown in Figure 3, but without the elastic layer 106. The sheath 301 includes a similar structure to the sheath 100 described above, and similar element numbers are used to indicate similar structures. The inner and outer layers 103 and 109 may be structured and configured to resist axial elongation of the sheath 101 during expansion. However, in the proposed configuration, as a result of the absence of the elastic layer, the sheath 101 remains at the expanded diameter along the portion of the sheath proximal to the valve, without necessarily returning to its initial diameter D1 after the valve has passed longitudinally. Figure 39 is a schematic diagram of the sheath 101 remaining at the expanded diameter D2 along the portion proximal to the valve passage.

[0118] Accordingly, an expandable sheath for arranging a medical device is provided, comprising a first polymer layer, a braided layer radially outward from the first polymer layer, and a second polymer layer radially outward from the braided layer. The braided layer comprises a plurality of filaments braided together. The second polymer layer is bonded to the first polymer layer such that the braided layer is encapsulated between the first and second polymer layers. As the medical device passes through the sheath, the diameter of the sheath expands from the first diameter to the second diameter around the medical device, while the first and second polymer layers resist axial elongation of the sheath, so that the length of the sheath remains substantially constant. However, according to some examples, the first and second polymer layers are not necessarily configured to resist axial elongation.

[0119] According to another aspect of this disclosure, an expandable sheath includes an elastic layer. However, unlike the elastic layer 106 shown in Figure 3, the elastic layer is not configured to apply substantial radial forces. It can still help provide column strength to the sheath. By limiting the tangential (diameter) expansion of the braid, the elastic layer enhances the axial strength (column strength) of the braid and the sheath. Thus, the use of an elastic material with higher tensile strength (resistance to stretching) may result in a sheath with greater column strength. Similarly, elastic materials under greater tension in a free state will also result in a sheath with greater column strength during extrusion, as they may be more resistant to stretching. The pitch of any helically wound elastic layer is another variable that contributes to the column strength of the sheath. The additional column strength ensures that the sheath does not spontaneously expand due to the frictional forces applied to it during forward movement in the distal direction and does not buckle when the delivery system is pulled out of the sheath.

[0120] In another arbitrary example, the elastic layer may be applied by dipping coating an elastic material (not limited to silicone or TPU). Dipping coating can be applied to a polymer outer layer or a braided layer.

[0121] Accordingly, an expandable sheath for accommodating a medical device is provided, comprising a first polymer layer, a braided layer radially outward from the first polymer layer, an elastic layer radially outward from the braided layer, and a second polymer layer radially outward from the braided layer. The braided layer comprises a plurality of filaments braided together. The elastic layer is configured to provide the expandable sheath with sufficient columnar strength to resist buckling of spontaneous expansion due to frictional forces applied to it by the surrounding anatomical structure during axial movement of the sheath. The second polymer layer is bonded to the first polymer layer such that the braided layer is encapsulated between the first and second polymer layers. As the medical device passes through the sheath, the diameter of the sheath expands from the first diameter to the second diameter around the medical device, while optionally, the first and second polymer layers resist axial elongation of the sheath such that the length of the sheath remains substantially constant.

[0122] According to one aspect of the present disclosure, a three-layer expandable sheath is provided, comprising an inner polymer layer, an outer polymer layer bonded to the inner polymer layer, and a braided layer encapsulated between the inner polymer layer and the outer polymer layer, wherein the braided layer includes an elastic coating.

[0123] Figure 41 shows a cross-section of the expandable sheath 201. Sheath 201 has a similar structure to sheath 100 described above, and similar element numbers are used to indicate similar structures. The expandable sheath 201 includes inner and outer polymer layers 203 and 209, as well as a braided layer 205. Instead of the elastic layer described with reference to Figure 3 above, the braided layer 205 is provided by an elastic coating 207. The elastic coating 207 can be applied directly to the filaments of the braided layer 205, as shown in Figure 41. The elastic coating can be made from a synthetic elastomer and exhibits similar properties to those described in relation to the elastic layer 106.

[0124] In some examples, the second outer polymer layer 209 is bonded to the first inner polymer layer 203 such that the braided layer 205 and the elastic coating 207 are encapsulated between the first and second polymer layers. Furthermore, the elastic coating applied directly to the braided filament is configured to perform the same function as the elastic layer 106 (i.e., to apply radial forces to the braided layer and the first polymer layer).

[0125] The example in Figure 41 shows an elastic coating 207 covering the entire circumference of all filaments in the braided layer 205, but it will be understood that only a portion of the filaments, for example, the portion that essentially constitutes the outer surface of the braided layer, may be coated by the elastic coating 207.

[0126] Alternatively or additionally, the elastic coating can be applied to other layers of the sheath 201.

[0127] In some examples, the braided layer, as shown in Figure 40, may have a self-shrinking frame made of a shape memory material, such as but not limited to nitinol. The self-shrinking frame can be pre-set to have a free-state diameter equal to the initial compressed diameter D1 of the sheath before being placed, for example, on a mandrel around the first polymer layer. The self-shrinking frame can expand to a larger diameter D2 while an internal device, such as an artificial valve, passes through the lumen of the sheath, and then self-shrink back to the initial diameter D1 upon passage of the valve. In some examples, the filaments of the braid are the self-shrinking frame, which is made of a shape memory material.

[0128] In another embodiment, the expandable sheath may include a braided expandable layer attached to at least one expandable sealing layer. In some examples, the braided layer and the sealing layer constitute only two layers of the expandable sheath. The braided layer is passively or actively expandable with respect to a first diameter, and at least one expandable sealing layer is passively or actively expandable with respect to a first diameter. The expandable sealing layer is useful in any of the above examples and may be particularly advantageous for braids having a self-contracting frame or filament.

[0129] The braided layer can be attached to or bonded to an expandable sealing layer along its entire length, advantageously reducing the risk of the polymer layer detaching from the braided layer due to frictional forces that may be applied to the polymer layer either during entry or exit through a surgical incision. At least one sealing layer may include a lubricating, low-friction material to facilitate passage of the sheath through a blood vessel and / or to facilitate passage of a delivery device carrying a valve through the sheath.

[0130] A sealing layer is defined as a layer that is not permeable to blood flow. A sealing layer can include polymer layers, films, coatings, and / or fabrics such as polymer fabrics. According to some examples, the sealing layer includes a lubricating, low-friction material. According to some examples, the sealing layer is radially outward relative to the braided layer to facilitate passage of the sheath through the blood vessel. According to some examples, the sealing layer is radially inward relative to the braided layer to facilitate passage of a medical device through the sheath.

[0131] According to some examples, at least one sealing layer is capable of passively expanding and / or self-contracting. In some examples, the sealing layer is thicker at certain longitudinal locations of the sheath than others, which can hold open the braided layer that self-contracts with a wider diameter than other longitudinal locations where the sealing layer is thinner.

[0132] Attaching the braided layer to at least one expandable sealing layer, instead of encapsulating it between two bonded polymer layers, could simplify the manufacturing process and reduce costs.

[0133] In some examples, the braided layer can be attached to both an outer and an inner expandable sealing layer so as to seal the braided layer from both sides, while facilitating the passage of the sheath along the blood vessel and the passage of the medical device within the sheath. In such examples, the braided layer can be attached to the first sealing layer, while the other sealing layer can also be attached to the first sealing layer. For example, the braided layer and the inner sealing layer can each be attached to the outer sealing layer, or the braided layer and the outer sealing layer can each be attached to the inner sealing layer.

[0134] In some examples, the braided layer is further coated with a sealing coating. This may be advantageous in configurations where the braided layer is attached to only a single expandable layer, and the coating ensures that the braided layer remains sealed from blood flow or other surrounding tissue, even along areas not covered by the expandable layer. For example, if the braided layer is attached to one side with a sealing layer, the other side of the braided layer may be able to receive the sealing coating. In some examples, the sealing coating can be used instead of, or in addition to, one or both of the sealing layers.

[0135] In another example, the sheath 100 may include a folded inner and outer layer structure. Examples of sheaths are described, for example, in U.S. Application No. 12 / 249,867 filed on 10 October 2008 (issued as U.S. Patent No. 8,690,936) and U.S. Application No. 13 / 312,739 filed on 6 December 2011 (issued as U.S. Patent No. 8,790,387), and these disclosures are incorporated herein by reference in their entirety. Figures 48 and 49 show cross-sections of another sheath structure. The sheath 100 includes an inner layer 102 and an outer layer 108 as described above. In some examples, a thin layer 162 of bonding or adhesive material is placed between the inner layer 102 and the outer layer 108. As shown in Figure 48, the inner layer 102 may be arranged to form a substantially cylindrical lumen 112 through which it passes. The inner layer 102 may include one or more folded portions 150. In the example shown in Figure 48, the inner layer 102 is arranged to have one folded portion 150 which may be located on both sides of the inner layer 102. The inner layer 102 may be continuous in that there are no breaks, slits, or perforations in the inner layer 102. The outer layer 108 may be arranged to overlap so that the overlapping portion 120 overlaps with at least a portion of the folded portion 150 of the inner layer 102. As shown in Figure 48, the overlapping portion 152 also overlaps with the base portion 154 of the outer layer 108. The base portion 154 may be arranged to be the base of both the overlapping portion 152 of the outer layer 108 and the folded portion 150 of the inner layer 102. Thus, the outer layer 108 may be discontinuous in that it includes slits or cuts to form the overlapping portion and the base portions 152, 154. In other words, the first edge 156 of the outer layer 108 is spaced apart from the second edge 158 of the outer layer 108 so as not to form a continuous layer. The configuration in Figure 48 allows for radial expansion of the sheath 100 when an inward-outward radial force is applied (for example, by a medical device such as an artificial heart valve passing through the lumen 112).When a radial force is applied, the folding portion 150 can be separated at least partially, straightened, and / or unfolded, and / or the overlapping portion 152 and base portion 154 of the outer layer 108 can slide circumferentially relative to each other, thereby allowing the diameter of the lumen 112 to expand as shown in Figure 49.

[0136] Thus, the sheath 100 is configured to expand from a stationary configuration (Figure 48) to an expanded configuration. In the expanded configuration, an annular gap 160 may be formed between the longitudinal edge of the overlapping portion 152 of the outer layer 108 and the base portion 154, as shown in Figure 49. When the sheath 100 expands at a particular position, the overlapping portion 152 of the outer layer 108 can move circumferentially relative to the base portion 154 as the folded portion 150 of the inner layer 102 unfolds. This movement can be facilitated by using a low-friction material such as PTFE for the inner layer 102. Furthermore, the folded portion 150 can be at least partially separated and / or unfolded to accommodate a medical device having a diameter larger than the diameter of the lumen 112 in the stationary configuration. As shown in Figure 48, in some examples, the folded portion of the inner layer 108 can be fully unfolded, so that the inner layer 102 forms a cylindrical tube in the expanded configuration.

[0137] The sheath 100 may be configured to expand locally at specific locations corresponding to the position of the medical device along the length of the lumen 112, and to contract locally as the medical device passes through those specific locations. Thus, the bulge may appear to move longitudinally along the length of the sheath as the medical device is introduced through the sheath, representing continuous local expansion and contraction as the device moves along the length of the sheath 100. In some examples, each segment of the sheath 100 can be locally contracted so that, after any radially outward force is removed, it recovers to the original stationary diameter of the lumen 112.

[0138] The expandable introducer is intended to be used with any of the sheath examples described herein. As described above, various sheath examples may include a distal tip formed from multiple layers and / or folded layers treated by compression or heat of the material. As a result, the distal tip of the sheath may be narrower and / or rigider than the rest of the sheath. Therefore, an expandable introducer can be used to facilitate the expansion of the distal tip of the sheath / pre-widen the sheath tip, providing more space for delivering and withdrawing a medical device through the distal opening of the sheath. Thus, it is possible to reduce the pushing force required for delivery and provide an opening large enough to retrieve the medical device without causing trauma to the patient and / or damage to the sheath.

[0139] Figure 50 shows an example of an expandable introducer sheath 100 combined with an expandable introducer 160. The expandable introducer 160 is shown together with the sheath 100 in Figure 2, but it is intended that the expandable introducer 160 can be used with any of the examples of expandable sheaths described above. Similar to the vascular dilator 300 described above, the introducer 160 facilitates the dilation of the distal tip of the sheath 100 and the corresponding area of ​​the patient's blood vessel.

[0140] As shown in Figure 50, the introducer 160 is received within the central lumen 112 of the sheath 100. The introducer 160 includes an elongated body member 162 and one or more inflatable members, such as a balloon 164, positioned along the elongated body member 162 between the proximal and distal ends 166, 168. The balloon 164 is configured to expand radially away from the outer surface of the elongated body member 162. As the balloon 164 inflates, the distal end portion 140 of the sheath 100 expands to provide an enlarged distal opening (Figure 52).

[0141] The balloon 164 can be inflated from an uninflated configuration (Figures 50 and 51) to an inflated configuration (Figure 52). In the uninflated / deflated configuration, the outer diameter of the balloon 164 corresponds to the outer diameter of the elongated body member 162. In the uninflated / deflated configuration, the outer diameter of the balloon 164 may be smaller than the outer diameter of the elongated body member 162. In the inflated / inflated configuration, the outer diameter of the balloon 164 is larger than the outer diameter of the elongated body member 162. In the inflated / inflated configuration, the diameter of the balloon 164 is up to approximately 75% larger than the diameter of the elongated body member 162. In some examples, in the inflated / inflated configuration, the diameter of the balloon 164 is approximately 10% to approximately 25% larger than the diameter of the elongated body member 162. In the exemplary system, the maximum diameter of the balloon 146 in the inflated configuration is approximately 25% to approximately 50% larger than the maximum diameter of the elongated body member 162. In a further example, the maximum diameter of the balloon 146 in the inflated configuration is approximately 50% to 75% larger than the maximum diameter of the elongated main body member 162.

[0142] The introducer 160 is movable axially / longitudally and rotatably within the central lumen 112. As shown in Figures 50-51, the introducer 160 is movable through the distal opening provided in the introducer sheath 100. When the balloon 164 deflates, at least a portion of the balloon 164 can pass through the distal opening of the introducer sheath 100 (Figure 51). When inflated / expanded, the balloon 164 widens / expands the distal end portion 140 (or at least a portion thereof) of the sheath 100, increasing the diameter of the distal opening.

[0143] The inflated balloon 164 can have any regular and irregular shape. Figures 53A–53J show various exemplary shapes of the inflated balloon 164. The shape of the inflated balloon 164 can be selected based on the patient's anatomical structure and / or the physician's preference. As described below, the shape of the balloon 164 can affect the expanded shape of the distal end portion 140 of the sheath 100. The physician can select the desired shape of the expanded distal end portion 140 based on the medical device being delivered and / or the tool being used, which will likely require withdrawal / retrieval through the expanded distal opening of the sheath 100. Figure 53A shows a circular / elliptical balloon 164. Figure 53B shows a circular / spherical balloon 164. Figure 53C shows an elongated spherical balloon 164 having an elongated cylindrical body and hemispherical front and rear edges, the front edge adjacent to the distal end 168 of the introducer 160 and the rear edge adjacent to the proximal end 166 of the introducer 160. Figure 53D shows an elongated conical / square balloon having an elongated cylindrical body and a square first edge and a tapered second edge. Figure 53D shows a square front edge and a tapered rear edge, but opposite orientations are intended. The tapered rear edge may be desirable to provide a tapered extended configuration to the distal end portion 140 of the sheath 100. Figure 53E shows an elongated conical / sphere balloon 164 having an elongated cylindrical body and a tapered hemispherical first edge and a tapered second edge. Figure 53E shows a tapered trailing edge and a hemispherical trailing edge, although opposite orientations are intended. As shown in Figure 53D, the tapered trailing edge of Figure 53E may be desirable to provide a tapered extended configuration of the distal end portion 140 of the sheath 100. Figure 53F shows an elongated conical / conical balloon including an elongated cylindrical body and tapered trailing edges. The trailing and leading edges may have corresponding tapers (Figure 53F). Alternatively, the taper of the trailing edge may be greater than the taper of the trailing edge. Similarly, the taper of the trailing edge may be greater than the taper of the trailing edge. The balloon 164 may include only the trailing and leading edges that abut each other, and is intended not to include a cylindrical portion extending between them.Furthermore, the balloon 164 is intended to include a tapered body portion extending between a tapered leading edge and a tapered trailing edge, for example, as shown in Figure 53H. In this example, the taper may vary between the leading edge, the trailing edge, and the body portion. Similarly, the axial length of the taper may vary between the leading edge and the trailing edge (and the tapered body portion, if applicable). Figure 53G shows that a conical / square balloon includes a square first edge and a tapered second edge, with opposite orientations intended. As shown in Figure 53G, a conical trailing edge may be desirable to provide a conical extended configuration of the distal end portion 140 of the sheath 100). Figure 53I shows a stepped balloon 164 including a portion with a varying diameter. As shown in Figure 53I, the diameter of each section decreases between the distal and proximal ends 168, 166 of the introducer 160, with the opposite orientation (proximal to distal) of the reduced diameter sections intended. Figure 53J shows an offset balloon 146 having a height on the first side of the elongated body member 162 that is greater than the height on the second side opposite the elongated body member 162. Although not shown, balloon 164 is intended to have a square shape.

[0144] The balloon 164 can be constructed from compliant materials, semi-compliant materials, and / or non-compliant materials. For example, if the balloon 164 is made of a compliant material, it may be made of polyamide, polyolefin, silicone, and / or polyester. In some examples, the polyamide may be nylon. In some examples, the polyolefin may be polyethylene or polypropylene. In some examples, the polyester may be polyethylene terephthalate (PET). The balloon 164 can also be made from polymer materials. Different parts of the balloon 164 may be made of different materials, such as compliant materials, semi-compliant materials, and / or non-compliant materials. For example, the proximal portion of the balloon 164 may be made of a material with a lower degree of conformity than the distal portion of the balloon 164, the proximal portion of the balloon adjoins the proximal end 166 of the elongated body member 162, and the distal portion of the balloon 164 adjoins the distal end 168 of the elongated body member 162.

[0145] The balloon 164 may also be composed of an impermeable material for containing an inflatable fluid, such as saline solution, within the balloon 164. In some examples, the inflatable fluid may also contain a contrast agent. The balloon 164 may be composed of a permeable material, such as mesh or a perforated material. In this example, the permeable material allows fluid communication between the inside and outside of the balloon 164. The inflatable fluid is supplied to the inside of the balloon 164 through an expansion lumen 170. The expansion lumen 170 extends longitudinally within the elongated body portion 162 of the introducer 160, between the reservoir for the inflatable fluid and the inside of the balloon 164. The volume of the inflatable fluid can be varied to control the volume / expansion of the balloon 164. If the balloon 164 is permeable, the flow rate of the inflatable fluid into the balloon 164 and through the mesh material can be varied to control the expansion of the balloon 164. In addition, the flow rate of the expanding fluid can be controlled so that the balloon 164 expands to a diameter larger than the outer diameter of the elongated main body member 162, even while the expanding fluid is passing through the mesh material.

[0146] The balloon 164 may have a uniform wall thickness along its circumference and / or around it. In another example, the wall thickness of the balloon 164 varies along its circumference and / or around it. For example, the wall thickness of the proximal portion of the balloon 164 may be greater than the thickness of the distal portion of the balloon 164, with the proximal portion adjacent to the proximal end 166 of the elongated body member 162 and the distal portion adjacent to the distal end 168 of the elongated body member 162. In an alternative example, the thickness of the distal portion of the balloon 164 is greater than the thickness of the proximal portion of the balloon 164. In a further example, the balloon 164 includes at least one circumferential band with increased wall thickness.

[0147] Figures 54-56 provide cross-sectional views of the distal end portion 140 of the sheath 100 and the introducer 160. As shown in Figure 54, the balloon 164 is connected to the elongated body member 162 such that there is no gap or break between the outer surface of the elongated body member 162 and the outer surface of the balloon 164. To facilitate the movement of the introducer 160 within the central lumen 112 of the sheath 100, the elongated body member 162 may be made of a lubricating material or may have a lubricating coating. In some examples, the elongated body member 162 is composed of a flexible material, including, for example, high-density polyethylene, PTFE, other fluoropolymers, such as ECTFE (ethylene chlorotrifluoroethylene) (e.g., Halar®, available from Solvay), polyamides (e.g., nylon 6, nylon 6,6, and other nylons), acetal copolymers or polyoxymethylenes (e.g., Celcon®, available from Celanese), polyolefins (e.g., HDPE), and / or polyolefin blends. Alternatively, a "blend" of materials, such as a blend of HDPE and LDPE, may also be used. The elongated body member 162 may include flexible features / attributes that promote lateral flexibility. Exemplary flexible features include grooves extending circumferentially and / or longitudinally, slits extending circumferentially / radially, and coil structures embedded within the elongated body member 162 of the introducer 160.

[0148] As shown in Figure 54, the distal end of the elongated body member 162 includes a tapered tip portion adapted for insertion into body tissue. To assist in positioning the introducer 160 and sheath 100 close to the treatment site, the introducer may also include at least one radiopaque marker. For example, the radiopaque marker may be positioned close to the tapered distal end of the introducer 160, along the elongated body member 162 at the anterior end of the balloon 164, on the balloon 164, and / or along the elongated body member 162 at the posterior end of the balloon. To further assist in positioning the introducer 160 and sheath 100, the introducer 160 includes a guidewire lumen 172. The guidewire lumen 172 extends through the introducer 160, receives a guidewire, and is sized and configured to facilitate the advancement of the introducer 160 / sheath 100 into the treatment site. As shown in Figure 54, the guide wire lumen 172 extends along the longitudinal centerline of the elongated body member 162, and the expansion lumen 170 is radially offset from the guide wire lumen 172 such that the expansion lumen 170 extends along one side of the guide wire lumen 172.

[0149] A method for expanding the distal end portion 140 of the sheath 100 during delivery of the medical device is described below. Figure 54 shows the sheath 100 and introducer 160 before the distal end portion 140 of the sheath 100 is expanded by the balloon 164, before insertion into the patient's vascular structure and / or during insertion. As shown in Figure 54, the introducer 160 is advanced into the central lumen 112 of the sheath 100. Generally, the outer diameter of the elongated body member 162 of the introducer is smaller than the diameter of the central lumen 112 of the sheath 100. Thus, the introducer 160 is generally movable (axially and rotationally) within the central lumen 112 of the sheath 100. However, as shown in Figure 54, during insertion and before inflation of the balloon 164, at least a portion of the outer surface of the elongated body member 162 is fitted to the surface of the central lumen 112 of the introducer sheath 100 adjacent to the distal opening. The tight fit between the introducer 160 and the sheath 100 helps reduce the pushing force and patient trauma when inserting the sheath into the patient's tissue. The elongated body member 162 is fitted to the surface of the central lumen 112 by at least one of press-fit and interference fit. As shown in Figure 54, with the introducer 160 fitted to the distal end portion 140 of the sheath 100, the distal end of the introducer 160 extends through and beyond the distal opening of the central lumen 112. In some examples (not shown), the distal end of the introducer 160 is coplanar with the distal end / distal opening of the central lumen 112.

[0150] Typically, the guidewire is advanced through the patient's vascular structure to the treatment site. With the sheath 100 and introducer 160 connected, the sheath 100 and introducer 160 are advanced along the guidewire to the treatment site. The guidewire may remain in place or be removed during expansion of the distal end portion 140 of the sheath 100. The position of the sheath 100 and / or introducer 160 can be imaged as it moves through the patient's vascular structure using an imaging modality such as radiofluoroscopy. The introducer 160 may include radiopaque markers to determine its position.

[0151] Once the sheath 100 is in the desired position, the introducer 160 is advanced axially / longitudinally within the central lumen of the sheath 100, as shown in Figure 55, so that the inflatable balloon 164 is axially aligned with the distal opening of the sheath 100. Advancement of the introducer 160 axially / longitudinally within the central lumen 112 of the sheath 100 includes advancing the distal end of the elongated body member 162 beyond the distal opening of the central lumen 112 (if it does not already extend beyond that range). The introducer 160 and / or sheath 100 may include a stopping feature so that the axial movement of the introducer 160 through the distal opening is limited to a previously determined most distal position of the introducer 160 relative to the sheath 100. At this most distal position, the balloon 164 is axially aligned with the distal opening of the sheath 100. When the balloon 164 is aligned axially with the distal opening of the sheath 100, the balloon 100 is positioned such that the first portion 164A of the balloon 164 extends beyond the distal opening of the sheath 100 and the second portion 164B of the balloon 164 is located within the central lumen 112 of the sheath 100 (Figure 55).

[0152] Next, as shown in Figure 56, the expansion fluid is supplied to the balloon 164 through the expansion lumen 170, causing the balloon 164 to expand. The balloon 164 expands from its initial diameter to a second diameter larger than the initial diameter. The expansion of the balloon 164 results in a corresponding expansion of the distal end portion 140 of the sheath 100, such that the diameter of the distal opening increases from the initial (unexpanded) diameter to the second, larger expanded diameter. As discussed above, the shape of the expanded balloon 146 can determine the shape of the expanded configuration of the distal end portion 140 of the sheath 100. For example, as shown in Figure 56, the rear end of the balloon 164 has a tapered surface extending from an elongated cylindrical body toward the outer surface of the introducer 160. The tapered surface is located adjacent to the distal opening of the sheath 100 and expands the distal end portion 140 into a corresponding tapered shape.

[0153] Next, the balloon 164 deflates once the inflating fluid is removed from inside the balloon 164. For example, the inflating fluid can be withdrawn from the balloon 164 via mechanical suction or suction. In another example, if the balloon 164 contains mesh material, the flow of the inflating fluid into the balloon 164 ends, resulting in the balloon's deflation. As the balloon 164 deflates, its diameter becomes smaller than its second / inflated diameter and approaches its initial / uninflated diameter. The introducer 160 is then withdrawn through the central lumen 112 of the sheath 100, while the distal end portion 140 of the sheath 100 remains expanded after the introducer 160 has been withdrawn.

[0154] Once the introducer 160 is removed from the central lumen 112, the medical device 12 can be advanced through the sheath 100 to the treatment site. As the medical device 12 is advanced through the central lumen 112 of the sheath 100, the medical device 12 applies an outward radial force to the inner surface of the central lumen 112. This outward radial force locally expands the sheath 100 from an initial unexpanded state to a locally expanded state. The diameter of the sheath 100 increases from a first (unexpanded) diameter to a second larger (expanded) diameter. In some of the examples described above, the sheath 100 includes a polymer layer having at least one longitudinally extending fold when the sheath 100 is at its first (unexpanded) diameter. The medical device 12 passing through the central lumen 112 of the sheath 100 applies an outward radial force to the sheath 100, causing the sheath 100 to expand radially by unfolding longitudinally extending folds at least partially. In some examples, the partial unfolding of the longitudinally extending folds results in a reduction in the wall thickness of the introducer sheath 100. Similarly, in some of the examples described above, the sheath 100 includes a polymer layer having multiple longitudinally extending folds when the sheath 100 is at a first (unexpanded) diameter. The longitudinally extending folds create multiple circumferentially spaced ridges and multiple circumferentially spaced grooves. As the medical device 12 passes through the central lumen 112 of the sheath 100, it applies an outward radial force to the sheath 100, flattening any ridges and grooves, thereby radially expanding the sheath 100 from a first (unexpanded) diameter to a second, larger (expanded) diameter. Preferably, the medical device 12 advances through the sheath 100 with a pushing force smaller than the pushing force required for a sheath with an unexpanded tip.

[0155] As the medical device 12 passes through, the sheath 100 locally shrinks after the passage of the medical device 12, returning from a locally expanded state to at least partially unexpanded. In some examples, the sheath 100 includes a layer of self-shrinking material that facilitates the local shrinking of the sheath.

[0156] As shown in Figure 57, the medical device advances through the central lumen 112 of the sheath 100 and beyond the distal opening to be positioned at the treatment site. In some examples, the medical device 12 is an artificial heart valve, for example, a self-expanding artificial heart valve. Once the medical device 12 is delivered to the patient, the sheath 100 is removed.

[0157] The introducer sheath 100 described herein is further intended to be used in combination with an expansion device 1000. Examples of the expansion device 1000 are shown in Figures 58-64. Similar to the vascular dilator 300 and introducer 160 described above, the expansion device 1000 pre-dilates the sheath and / or the patient's blood vessel prior to the delivery device. The expansion device 1000 may be an introducer or a dilator, depending on when / how the expansion device 1000 is used in the procedure. For example, when used as an introducer, the expansion device 1000 is positioned within the central lumen 112 of the sheath 100, and the combined expansion device 1000 and sheath are introduced together into the patient's blood vessel. The expansion device 1000 can then advance further within the sheath to locally dilate the central lumen 112 of the sheath 100. In another example, if the dilation device 1000 is used as a dilator, the sheath 100 is placed in the patient's blood vessel before insertion of the dilation device 1000. Once the sheath 100 is placed in the vascular structure, the dilation device 1000 passes through the central lumen of the sheath 100 to widen / dilate the sheath 100 and the patient's blood vessel.

[0158] As described above, the expansion device 1000 is received within the central lumen 112 of the sheath 100. As shown in FIGS. 58-64, the expansion device 1000 includes an elongated body 1010 and one or more radially extending protrusions 1020 disposed along a portion of the body 1010. The expansion device 1000 is sized and configured to be received within the central lumen 112 of the expandable sheath 100 such that the protrusions 1020 at least partially expand a portion of the expandable sheath 100. As described above, the expansion device 1000 is configured to be received within any of the expandable sheath implementations disclosed herein. The protrusions 1020 of the expansion device 1000 may be formed from a fixed structure such that the size and shape of the protrusions 1020 do not change during use. In another embodiment, the protrusions 1020 are constructed from an expandable structure such that the size and shape of the protrusions 1020 can be adjusted during use.

[0159] FIG. 58 shows an exemplary expansion device 1000. The expansion device 1000 includes a body 1010 having a proximal end 1012 and a tapered distal end 1014 that is opposite and spaced from the proximal end 1012 of the body 1010. The tapered distal end 1014 of the body 1010 includes a decreasing taper that extends from the diameter of the body 1010 toward the distal end of the expansion device 1000. As shown in FIG. 58, the protrusions 1020 extend radially from the outer surface of the body 1010 such that the outer surface of the protrusions 1020 has a diameter greater than the diameter of the body 1010.

[0160] For example, the body 1010 includes a body diameter D B and the protrusions 1020 include a protrusion diameter D P and the protrusion diameter D P is greater than the body diameter D B In some examples, the body diameter D B is 14F and the diameter D PIn other examples, the body diameter is 2F and the projection diameter is greater than 2F. In other examples, the body diameter is 4F and the projection diameter is greater than 4F. In other examples, the body diameter is 6F and the projection diameter is greater than 6F. In other examples, the body diameter is 8F and the projection diameter is greater than 8F. In other examples, the body diameter is 10F and the projection diameter is greater than 10F. In other examples, the body diameter is 12F and the projection diameter is greater than 12F. In other examples, the body diameter is 16F and the projection diameter is greater than 16F. In other examples, the body diameter is 18F and the projection diameter is greater than 18F. In other examples, the body diameter is 20F and the projection diameter is greater than 20F. In other examples, the body diameter is 22F and the projection diameter is greater than 22F. In other examples, the body diameter is 24F and the projection diameter is greater than 24F. In other examples, the body diameter is 26F and the projection diameter is greater than 26F. In other examples, the body diameter is 28F, and the projection diameter is greater than 28F. In other examples, the body diameter is any suitable diameter, as long as the projection diameter is greater than the body diameter.

[0161] The projection 1020 can be fixedly positioned along the length of the body 1010. For example, the projection 1020 can be fixedly connected to the body 1010 and / or formed integrally with the body 1010. In some examples, the projection 1020 is molded together with the body 1010 or otherwise formed integrally with the body 1010. In further examples, the projection 1020 is fixedly connected to the body 1010 by adhesive, chemical or mechanical fasteners and / or heat treatment (e.g., welding).

[0162] The projection 1020 can have any regular or irregular shape. The projection 1020 can have any shape similar to the shape of the balloon 164 shown in Figures 53A-53J. The physician can select the desired shape of the projection 1020 based on the medical device to be delivered and / or the tool to be inserted after the expansion device 1000 has been used to pre-expand and / or pre-inflate the sheath 100. As shown in Figures 58 and 59, the projection 1020 can be molded into a spherical shape having a curved front end 1022 and a curved rear end 1024. As shown in Figure 60, the projection 1020 is cylindrical and has curved / tapered front and rear ends 1022, 1024. In other examples, as shown in Figures 53F and 53H-53J, the projection 1020 has a tapered front end 1022. As shown in Figures 53D-53J, the projection 1020 has a tapered rear end 1024. In other examples, the projection is any preferred shape having a diameter or outer circumference larger than the diameter of the main body 1010, so as to be able to at least partially expand a portion of the expandable sheath 100.

[0163] As shown in Figures 58-64, the projection 1020 is positioned between the proximal end 1012 and the tapered distal end 1014 of the body 1010. As shown in Figures 58 and 59, the projection 1020 is positioned adjacent to the proximal end of the body 1012. In this example, when the expansion device is inserted into the sheath 100, the projection 1020 expands and / or unfolds a portion of the proximal end of the sheath 100. In some examples, the sheath 100 includes a strain relief portion 1102 that extends distally from the proximal end of the sheath 100 (e.g., along the outer layer / jacket), providing increased hardness and rigidity compared to the rest of the sheath 100. When the expansion device 1000 and projection 1020 are moved through the sheath 100 adjacent to the strain relief portion 1102, the portion of the sheath 100 adjacent to the strain relief portion 1102 expands / unfolds at least partially.

[0164] Both the body 1010 and the projection 1020 further include outer surfaces 1018 and 1028. In some examples, the outer surface 1018 of the body 1010 and the outer surface 1028 of the projection 1020 include a hydrophilic coating to reduce friction between the sheath 100 and the expansion device 1000, ensuring that the expansion device 1000 is easily received and movable within the central lumen of the expandable sheath 100. In some examples, the hydrophilic coating includes a material having a low coefficient of friction.

[0165] In another example, as shown in Figure 59, the expansion device 1000 further includes a locking mechanism 1030 connected to the main body 1010. The locking mechanism 1030 can be used to fix / restrict the movement of the expansion device 1000 within the central lumen 112 of the sheath 100. In some examples, the locking mechanism 1030 can restrict the axial and / or rotational movement of the expansion device 1000 within the central lumen 112. In some examples, the locking mechanism 1030 connects / engages with the housing 92. In further examples, the locking mechanism 1030 has an increased diameter portion that protrudes from the outer surface / diameter of the sheath 100, with the outer diameter of the locking mechanism 1030 being larger than the diameter of the central lumen 112, preventing the locking mechanism 1030 from entering the central lumen 112 and fixing the axial position of the locking mechanism 1030 / expansion device 1000.

[0166] The locking mechanism 1030 is positioned along the proximal end 1012 of the main body 1010, and the main body diameter D B Larger than. In some implementations, the locking mechanism 1030 can be adjusted along a portion of the body so that the user can adjust the distance between the projection 1020 and the locking mechanism 1030, thereby adjusting the distance the projection 1020 / expansion device 1000 moves within the expandable sheath 100. As a result, the locking mechanism 1030 helps prevent the user from inserting the expansion device 1000 (and projection 1020) too deeply into the expandable sheath 100, thus avoiding unnecessary trauma to the patient's vascular system.

[0167] In the example shown in Figure 60, the expansion device 1000 can be used as an introducer. The locking mechanism 1030 is positioned at a predetermined distance from the projection 1020 so that when inserted into the sheath 100, the projection 1020 does not extend beyond the strain relief portion 1102 of the sheath 100. As a result, the expansion device 1000 expands the expandable portion of the sheath 100 within the strain relief portion 1102, and the pushing force required to subsequently insert a medical device through the strain relief portion 1102 is greatly reduced.

[0168] Figure 61 shows another example of an expansion device 1000 that can be used as an introducer. The expansion device 1000 includes a tapered front end 1026 that extends from the outer diameter / surface of the body 1010 to the outer diameter of the projection 1020. In this example, when the expansion device is inserted into the central lumen 112 of the sheath 100, the projection 1020 and / or the tapered front end 1026 align with the position of the strain relief portion 1102 of the expandable sheath 100. In the exemplary projection 1020 shown in Figure 60, the outer diameter of the projection 1020 remains constant between the proximal end of the tapered front end 1026 and the proximal end 1012 of the expansion device. However, as outlined above, in other examples, the projection 1020 may include a rear end that is tapered, curved, or has any other regular or irregular shape.

[0169] As described above, the expansion device 1000 can be used as a dilator to widen / expand the sheath 100 and the corresponding portion of the patient's blood vessel prior to insertion of the delivery device. Figures 62 and 63 show an exemplary expansion device 1000 that can be used as a dilator. In this example, the projection 1020 is positioned close to the tapered distal end 1014 of the body 1010. When used as a dilator, the projection 1020 is intended to be positioned at any position between the tapered distal end 1014 and the proximal end 1012 of the body 1010. As shown in Figures 62 and 63, the spherical projection 1020 is positioned offset from the proximal end 1015 of the tapered distal tip 1014. In other examples, the projection is positioned adjacent to the proximal end 1015 of the tapered distal end 1014. When provided at the distal end of the main body 1010, the projection 1020 locally widens and / or dilates the sheath 100 and the patient's vessel as it advances through the central lumen of the sheath. This local and transient dilation reduces stress on both the sheath 100 and the vessel compared to a typical introducer / dilator that provides increased diameter over a longer area along the sheath / vascular space over a longer period of time.

[0170] Figure 64 shows another example of the dilation device 1000 that can be used as a dilator. In this example, the projection is positioned close to the tapered distal end 1014 of the body 1010. As described above, the dilation device 1000 also includes a locking mechanism 1030. The locking mechanism 1030 is positioned relative to the projection 1020 of the dilation device 1000 so that the projection 1020 can extend beyond the strain relief portion 1102 of the corresponding dilatable sheath 100 when assembled. As the dilation device 1000 and the projection 1020 advance through the sheath 100, the projection 1020 locally widens and / or dilates the sheath and the patient's blood vessels. The axial distance that the projection 1020 can advance within the sheath 1100 is adjustable by changing the position of the locking mechanism 1030 or by adjusting the axial position of the projection 1020 on the body 1010, as described below.

[0171] As described above, the projection 1020 can be fixed axially and / or rotationally at specific positions along and around the body 1010 of the extension device. It is further intended that the axial and rotational positions of the projection 1020 can be adjusted along and around the body 1010. For example, the projection 1020 may include an adjustment device that can fix the projection 1020 at positions that vary longitudinally and circumferentially along and around the body 1010. For example, the projection 1020 may include a threaded portion for engaging with a corresponding threaded portion on the body 1010. In one example, the projection 1020 includes a central lumen / through hole with a threaded inner surface. Similarly, the outer surface of the body 1010 may include a threaded outer surface extending along all or part of the outer surface of the body 1010. The threaded opening provided in the projection 1020 can engage with a threaded portion provided on the outer surface of the body 1010 such that the projection 1020 is rotatably adjustable around the body 1010 and therefore axially movable along the body 1010 by engagement between the threaded portions. In other configurations, the projection 1020 is rotatably positioned on the body 1010 and includes a locking mechanism (e.g., a mechanical fastener including a pin, screw, bolt, clip, bayonet lock, or any other mechanical fastener suitable for securing the projection 1020 to the body 1010) for fixing the axial and rotational position of the projection 1020 along the body 1010.

[0172] Each of the expandable sheaths 100 shown in Figures 60, 61, and 64 (Figures 48 and 49) includes an inner layer 1104 having at least one fold 1106 configured to move between a folded configuration as shown in Figure 48 and a less folded configuration as shown in Figure 49 during local expansion of the sheath 100. In particular, local expansion of the sheath 100 is caused by receiving a projection 1020 of one of the aforementioned implementations of the expansion device 1000. As described above, examples of foldable expandable sheaths can be found in U.S. Application No. 12 / 249,867, filed on 10 October 2008 (issued as U.S. Patent No. 8,690,936), titled "Expandable Sheath," U.S. Application No. 13 / 312,739, filed on 6 December 2011 (issued as U.S. Patent No. 8,790,387), and U.S. Provisional Patent Application No. 62 / 912,569, which are incorporated in their entirety by reference.

[0173] A method for locally dilating an expandable sheath using an expansion device is disclosed herein. In this example, a combined sheath and expansion device can be used as an introducer. The method includes introducing the expansion device into the central lumen of the expandable sheath. The combined expandable sheath and expansion device then advance into the patient's blood vessel. The expansion device advances distally within the central lumen of the expandable sheath, locally dilating the lumen of the sheath at a local axial position corresponding to the axial position of a radially extending projection provided on the expansion device.

[0174] Introducing an expansion device within the central lumen of an expandable sheath also includes positioning the expansion device within the central lumen of the sheath such that a radially extending projection is located proximal (outer) to the strain relief portion of the sheath. In another example, introducing an expansion device within the central lumen of an expandable sheath also includes positioning the expansion device within the central lumen of the sheath such that a projection is located at least partially within the strain relief portion of the expandable sheath.

[0175] In some examples, locally expanding the lumen of the sheath further involves advancing the expansion device into the elongated body portion of the sheath through the strain relief portion of the sheath. The expansion device can then advance beyond the strain relief portion of the sheath into the elongated body portion of the sheath.

[0176] The method then includes removing the expansion device from the expandable sheath such that the outer diameter of the sheath corresponding to the position of the projection (and the inner diameter of the central lumen of the sheath) is greater than the diameter of the initial, unexpanded sheath.

[0177] Finally, the method involves inserting a medical device into the central lumen of an expandable sheath.

[0178] Another method for locally dilating an expandable sheath using an expansion device is disclosed herein. In this example, the sheath and the expansion device can be used as dilators to pre-widen / dilate the sheath and the patient's vascular structure. The method comprises introducing an expandable sheath having a central lumen into the patient's vascular system. The expansion device is advanced into the central lumen of the expandable sheath. The expansion device advances distally within the central lumen of the expandable sheath, locally dilating the lumen of the sheath at a (local) axial position corresponding to the axial position of a radially extending projection provided on the expansion device.

[0179] Introducing an expansion device within the central lumen of an expandable sheath may further include positioning the expansion device within the central lumen of the sheath such that a radially extending projection is located within at least the strain relief portion of the expandable sheath.

[0180] In some cases, locally expanding the lumen of the sheath further involves advancing the expansion device beyond the strain relief portion of the sheath into the elongated body portion of the sheath.

[0181] Next, the method includes removing the expansion device from the expandable sheath such that the outer diameter of the sheath corresponding to the position of the projection (and the inner diameter of the central lumen of the sheath) is greater than the diameter of the initial, unexpanded sheath. Finally, the method includes inserting the medical device into the central lumen of the expandable sheath.

[0182] General Considerations For the purposes of this specification, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The methods, apparatus, and systems disclosed should not be construed as limiting in any way. Rather, this disclosure covers all novel and non-obvious features and aspects of the various embodiments disclosed, both individually and in various and partial combinations with each other. The methods, apparatus, and systems are not limited to any particular aspect or feature, or any combination thereof, nor is it required that any particular advantage or problem be solved in any one or more of the embodiments disclosed.

[0183] Some of the operations of the disclosed embodiments are described in a specific sequential order for convenience of presentation, but it should be understood that this method of description is inclusive of reordering unless a specific order is required by the specific terms set forth below. For example, operations described sequentially may, in some cases, be reordered or performed simultaneously. Furthermore, for simplification, the accompanying drawings may not show various ways in which the disclosed methods may be used in combination with other methods. In addition, this description sometimes uses terms such as “provides” or “achieves” to describe the disclosed methods. These terms are high-level abstractions of the actual operations performed. The actual operations corresponding to these terms may vary depending on the specific implementation and will be readily apparent to those skilled in the art.

[0184] As used in this application and claims, the singular forms "a," "an," and "the" include the plural form unless the context otherwise explicitly indicates. In addition, the term "includes" means "comprises." Furthermore, the terms "connected" and "related" generally mean connected or related electrically, electromagnetically, and / or physically (e.g., mechanically or chemically), and do not preclude the existence of intermediate elements between connected or related items, without the presence of a specific opposite term.

[0185] In the context of this application, the terms “lower” and “upper” are used interchangeably with the terms “inflow” and “outflow,” respectively. Therefore, for example, the lower end of the valve is the inflow end, and the upper end of the valve is the outflow end.

[0186] As used in this specification, the term “proximal” refers to a location, orientation, or portion of the device that is closer to the user and further away from the implantation site. As used herein, the term “distal” refers to a location, orientation, or portion of the device that is further away from the user and closer to the implantation site. For example, proximal movement of the device is movement of the device toward the user, while distal movement of the device is movement of the device away from the user. Unless otherwise explicitly defined, the terms “longitudinal” and “axial” refer to axes extending in the proximal and distal directions.

[0187] Unless otherwise indicated, all figures used in the specification or claims, representing dimensions, component quantities, molecular weights, percentages, temperatures, forces, times, etc., should be understood to be modified by the term "approximately." Therefore, unless implicitly or explicitly indicated otherwise, the numerical parameters shown are approximations that may depend on the desired properties and / or detection limits under test conditions / methods well known to those skilled in the art. Where examples are directly and explicitly distinguished from the prior art discussed, the figures in the examples are not approximations unless the phrase "approximately" is enumerated. Furthermore, not all substitutes listed herein are equivalent.

[0188] Given the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the exemplary embodiments are merely preferred embodiments and should not be considered to limit the scope of the disclosure. Rather, the scope of this disclosure is at least as broad as the following claims. Accordingly, we assert all that falls within the scope of these claims and their intent.

[0189] Exemplary embodiments Example 1: An expandable introducer comprising: an elongated body member; an inflatable balloon positioned between the proximal and distal ends of the elongated body member, wherein the balloon is expandable from a deflated configuration to an inflated configuration; and an expansion lumen in fluid communication with the inflatable balloon, wherein the expansion is sized and configured to provide expansion fluid to the balloon, wherein in the deflated configuration, the outer diameter of the balloon corresponds to the outer diameter of the elongated body member; and in the inflated configuration, the outer diameter of the balloon is greater than the outer diameter of the elongated body member, and at least a portion of the balloon is sized and configured to pass through the distal opening of the expandable introducer sheath when the balloon is deflated, and the balloon is sized and configured to expand at least a portion of the distal end of the introducer sheath when the balloon expands. Example 2: An expandable introducer according to any embodiment of this specification, particularly the expandable introducer according to Example 1, comprising an expandable introducer sheath for deploying a medical device, wherein an elongated body member is received within a central lumen of the introducer sheath and is axially and rotatably movable therein. Example 3: An expandable introducer according to any embodiment of this specification, particularly the one described in Example 2, wherein an elongated body member is movable through a distal opening provided in the introducer sheath. Example 4: An expandable introducer according to any embodiment of this specification, particularly Example 3, wherein, during insertion into a patient's vascular structure, at least a portion of the outer surface of the elongated main body member is fitted against the surface of the central lumen of the introducer sheath adjacent to the distal opening. Example 5: An expandable introducer according to any embodiment of this specification, particularly Example 4, wherein an elongated body member is fitted to the surface of the central lumen by at least one of press-fit and interference fit. Example 6: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 5, wherein the axial movement of an elongated body member through the distal opening is restricted such that the balloon axially aligns with the distal opening of the introducer sheath when the elongated body member is provided in its most distal position. Example 7: An expandable introducer according to any embodiment of this specification, particularly Example 6, wherein when the elongated main body member is at its most distal position, a first portion of the balloon extends beyond the distal opening of the introducer sheath, a second portion of the balloon remains within the central lumen of the introducer sheath, and the second portion of the balloon expands at least a portion of the distal end of the introducer sheath when the balloon expands from a deflated configuration to an inflated configuration. Example 8: An expandable introducer according to any embodiment of this specification, particularly the one described in Example 7, wherein the second portion of the balloon includes a tapered surface adapted to widen at least a portion of the distal end of the introducer sheath to a corresponding tapered shape. Example 9: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 8, wherein the diameter of the central lumen of the introducer sheath is greater than the diameter of the elongated body member. Example 10: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 9, wherein the diameter of the distal opening of the introducer sheath when expanded is up to about 75% larger than the diameter of the distal opening of the introducer sheath when not expanded. Example 11: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 10, wherein the diameter of the introducer sheath expands from a first diameter to a second larger diameter as a medical device passes through the central lumen of the introducer sheath. Example 12: An expandable introducer according to any embodiment of this specification, particularly the expandable introducer described in Example 11, wherein the introducer sheath comprises at least one polymer layer including a plurality of longitudinally extending folds when the sheath is at a first diameter, and a medical device passing through the central lumen of the introducer sheath applies an outward radial force to the introducer sheath, thereby radially expanding the introducer sheath from a first diameter to a second diameter by at least partially unfolding the plurality of longitudinally extending folds. Example 13: An expandable introducer according to any embodiment of this specification, particularly the one described in Example 12, wherein the unfolding of at least a portion of multiple longitudinally extending folds causes a reduction in the wall thickness of the introducer sheath. Example 14: An expandable introducer according to any embodiment of this specification, particularly the expandable introducer according to Example 11, wherein the introducer sheath comprises at least one polymer layer including a plurality of longitudinally extending folds when the sheath is at a first diameter, the longitudinally extending folds creating a plurality of circumferentially spaced ridges and a plurality of circumferentially spaced grooves, and a medical device passing through the central lumen of the introducer sheath applies an outward radial force to the introducer sheath, flattening the ridges and grooves, thereby radially expanding the introducer sheath from a first diameter to a second diameter. Example 15: An expandable introducer according to any embodiment of this specification, in particular the one described in Example 12, wherein the introducer sheath comprises at least one layer of a self-shrinking material. Example 16: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 15, wherein the outer diameter of the elongated body member is smaller than the diameter of the central lumen. Example 17: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 16, wherein the elongated main body member comprises a lubricating material. Example 18: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 17, wherein the elongated main body member is flexible. Example 19: An expandable introducer according to any embodiment of this specification, particularly Example 18, wherein the elongated main body member is made of a flexible material containing high-density polyethylene. Example 20: An expandable introducer according to any embodiment of this specification, particularly the one described in Example 18, wherein the elongated main body member includes flexible features including grooves, slits, and coils extending in at least one circumferential and / or longitudinal direction. Example 21: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 20, wherein the distal end of an elongated main body member includes a tapered tip portion adapted for insertion into body tissue. Example 22: An expandable introducer according to any example of this specification, particularly any of Examples 1 to 21, wherein the introducer includes a radiopaque marker. Example 23: An expandable introducer according to any embodiment of this specification, particularly Example 22, wherein the radiopaque marker is located in proximity to at least one of the following positions: the tapered distal end of the elongated body member, along the elongated body member adjacent to the front end of the balloon, on the balloon, and along the elongated body member at the rear end of the balloon. Example 24: An expandable introducer according to any embodiment of this specification, in particular any of Examples 1 to 23, comprising and extending through a guide wire lumen. Example 25: An expandable introducer according to any embodiment of this specification, particularly Example 24, wherein the guide wire lumen extends along the longitudinal centerline of an elongated body member, and the expansion lumen is radially offset from the guide wire lumen, and the expansion lumen extends along a first side of the guide wire lumen. Example 26: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 25, wherein the shape of the balloon in the inflated configuration includes at least one of a regular shape or an irregular shape. Example 27: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 26, wherein the shape of the balloon in the inflated configuration includes a tapered leading edge and a tapered trailing edge, the leading edge adjacent to the distal end of an elongated body member and the trailing edge adjacent to the proximal end of an elongated body member. Example 28: An expandable introducer according to any embodiment of this specification, particularly Example 27, wherein the leading edge taper corresponds to the trailing edge taper. Example 29: An expandable introducer according to any embodiment of this specification, particularly Example 27, wherein the leading edge taper is greater than the trailing edge taper. Example 30: An expandable introducer according to any embodiment of this specification, particularly Example 27, wherein the leading edge taper is smaller than the trailing edge taper. Example 31: An expandable introducer according to any embodiment of this specification, particularly Example 27, wherein the balloon includes a cylindrical body portion extending between a tapered leading edge and a tapered trailing edge. Example 32: An expandable introducer according to any embodiment of this specification, particularly Example 27, wherein the balloon includes a tapered body portion extending between a tapered leading edge and a tapered trailing edge, the taper of the body portion being different from the taper of the leading edge and the trailing edge, respectively. Example 33: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 32, wherein the shape of the balloon in the inflated configuration includes at least one elliptical balloon, spherical balloon, square balloon, conical balloon, elongated spherical balloon, elongated conical / square balloon, elongated conical / spherical balloon, elongated conical / conical balloon, conical / square balloon, tapered balloon, stepped balloon, and offset balloon. Example 34: A cone-shaped balloon includes tapered front and rear edges; an elongated spherical balloon includes an elongated cylindrical body portion and hemispherical front and rear edges; an elongated cone / square balloon includes an elongated cylindrical body, a tapered first edge and a square second edge; an elongated cone / sphere balloon includes an elongated cylindrical body, a tapered first edge and a hemispherical second edge; an elongated cone / cone-shaped balloon includes a tapered An expandable introducer according to any embodiment of this specification, particularly embodiment 33, wherein the conical / square balloon includes a leading edge and a trailing edge, the conical / square balloon includes a tapered first edge and a square second edge, the tapered balloon includes a tapered leading edge and a tapered trailing edge, the stepped balloon includes a portion of varying diameter, and the offset balloon includes a height on the first side of the elongated body member that is higher than the height on the second side opposite the elongated body member. Example 35: An expandable introducer according to any of the embodiments herein, particularly Example 1, wherein the balloon is made of a polymer material. Example 36: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 35, wherein the balloon is composed of at least one of compliant material, semi-compliant material, and non-compliant material. Example 37: An expandable introducer according to any embodiment of this specification, particularly Example 36, wherein the balloon is made of a compliant material. Example 38: An expandable introducer according to any example herein, particularly the one described in Example 37, wherein the balloon is composed of at least one of polyolefin, silicone, and polyethylene terephthalate. Example 39: An expandable introducer according to any embodiment of this specification, particularly Example 36, wherein different parts of the balloon are composed of different compliant, semi-compliant, and non-compliant materials. Example 40: An expandable introducer according to any embodiment of this specification, particularly Example 39, wherein the proximal portion of the balloon is made of a material with a lower degree of fit than the distal portion of the balloon, the proximal portion of the balloon is adjacent to the proximal end of an elongated body member, and the distal portion of the balloon is adjacent to the distal end of an elongated body member. Example 41: An expandable introducer according to any embodiment of this specification, particularly Example 40, wherein at least a portion of the proximal portion of the balloon includes a tapered surface. Example 42: An expandable introducer according to any embodiment of this specification, particularly the expandable introducer described in Example 41, wherein the tapered surface is sized and configured to be positioned adjacent to the distal opening of the introducer sheath so that the tapered surface of the balloon is adapted to expand the distal end of the introducer sheath. Example 43: An expandable introducer according to any of the embodiments herein, particularly any of Examples 1 to 42, wherein the balloon is made of an impermeable material. Example 44: An expandable introducer according to any of the embodiments herein, particularly any of Examples 1 to 43, wherein the balloon is made of a permeable material. Example 45: An expandable introducer according to any embodiment of this specification, particularly the one described in Example 44, wherein the balloon includes a mesh material that allows fluid communication between the inside and outside of the balloon. Example 46: An expandable introducer according to any embodiment of this specification, particularly Example 45, wherein the flow rate of the expanding fluid through the mesh material of the balloon has a diameter greater than the outer diameter of the elongated body member when inflating the balloon. Example 47: An expandable introducer according to any of the embodiments herein, particularly any of Examples 1 to 46, comprising an expanding fluid containing physiological saline. Example 48: An expandable introducer according to any example of this specification, particularly any of Examples 1 to 47, wherein the expanding fluid comprises a contrast agent. Example 49: An expandable introducer according to any embodiment of this specification, in particular any of Examples 1 to 48, wherein the balloon has a uniform thickness along the circumference and / or around the balloon. Example 50: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 49, wherein the thickness of the balloon varies along the length and / or around the circumference of the balloon. Example 51: An expandable introducer according to any embodiment of this specification, particularly Example 50, wherein the thickness of the proximal portion of the balloon is greater than the thickness of the distal portion of the balloon, the proximal portion of the balloon is adjacent to the proximal end of the elongated body member, and the distal portion of the balloon is adjacent to the distal end of the elongated body member. Example 52: An expandable introducer according to any embodiment of this specification, particularly Example 50, wherein the thickness of the distal portion of the balloon is greater than the thickness of the proximal portion of the balloon, the proximal portion of the balloon is adjacent to the proximal end of the elongated body member, and the distal portion of the balloon is adjacent to the distal end of the elongated body member. Example 53: An expandable introducer according to any embodiment of this specification, in particular Example 50, wherein the balloon includes at least one circumferential band of increased thickness. Example 54: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 53, wherein the balloon is coupled to an elongated body member such that there is no breakage between the outer surface of the elongated body member and the outer surface of the balloon. Example 55: An expandable introducer according to any embodiment of this specification, particularly any of Examples 1 to 54, wherein in the inflated configuration, the diameter of the balloon is up to approximately 75% larger than the diameter of the elongated body member. Example 56: An introducer sheath system comprising an expandable introducer sheath for deploying a medical device, an introducer which is received within a central lumen of the introducer sheath and is movable axially and rotatably therein, the introducer comprising an elongated body member having a proximal end and a tapered distal end, an inflatable balloon positioned between the proximal and distal ends of the elongated body member, the balloon being expandable from a deflated configuration to an inflated configuration, and an expansion lumen which is in fluid communication with the inflatable balloon. An introducer sheath system comprising: an expansion lumen, which is sized and configured to provide an expansion fluid to a balloon; in a deflated configuration, the outer diameter of the balloon corresponds to the outer diameter of an elongated body member; and in an expanded configuration, the outer diameter of the balloon is greater than the outer diameter of the elongated body member, and at least a portion of the balloon is sized and configured to pass through the distal opening of the introducer sheath when the balloon is deflated; and as the balloon expands, at least a portion of the distal end of the introducer sheath expands, increasing the diameter of the distal opening. Example 57: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 56, wherein an elongated main body member is movable through a distal opening provided in the introducer sheath. Example 58: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 57, wherein, during insertion into a patient's vascular structure, at least a portion of the outer surface of the elongated main body member is fitted against the surface of the central lumen of the introducer sheath adjacent to the distal opening. Example 59: An introducer sheath system according to any embodiment of this specification, in particular Example 58, wherein an elongated body member is fitted to the surface of the central lumen by at least one of press-fit and interference fit. Example 60: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56-59, wherein the axial movement of an elongated body member through the distal opening is restricted so that the balloon axially aligns with the distal opening of the introducer sheath when the elongated body member is provided to its most distal position. Example 61: An introducer sheath system according to any embodiment of this specification, particularly Example 60, wherein when the elongated main body member is at its most distal position, a first portion of the balloon extends beyond the distal opening of the introducer sheath, a second portion of the balloon remains within the central lumen of the introducer sheath, and the second portion of the balloon is sized and configured to widen at least a portion of the distal end of the introducer sheath when the balloon expands from a deflated configuration to an inflated configuration. Example 62: An introducer sheath system according to any embodiment of this specification, in particular Example 61, wherein a second portion of the balloon includes a tapered surface adapted to widen at least a portion of the distal end of the introducer sheath to a corresponding tapered shape. Example 63: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 62, wherein the diameter of the central lumen of the introducer sheath is greater than the diameter of the elongated body member. Example 64: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56-63, wherein the diameter of the distal opening of the introducer sheath when expanded is up to about 75% larger than the diameter of the distal opening of the introducer sheath when not expanded. Example 65: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56-64, wherein the diameter of the introducer sheath expands from a first diameter to a second larger diameter as the medical device passes through the central lumen of the introducer sheath. Example 66: An introducer sheath system according to any embodiment of this specification, particularly the introducer sheath system according to Example 65, wherein the introducer sheath comprises at least one polymer layer including a plurality of longitudinally extending folds when the sheath is at a first diameter, and a medical device passing through the central lumen of the introducer sheath applies an outward radial force to the introducer sheath, thereby radially expanding the introducer sheath from a first diameter to a second diameter by at least partially unfolding the plurality of longitudinally extending folds. Example 67: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 66, wherein the unfolding of at least a portion of multiple longitudinally extending folds causes a reduction in the wall thickness of the introducer sheath. Example 68: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 65-67, wherein the introducer sheath comprises at least one polymer layer including a plurality of longitudinally extending folds when the sheath is at a first diameter, the longitudinally extending folds creating a plurality of circumferentially spaced ridges and a plurality of circumferentially spaced grooves, and a medical device passing through the central lumen of the introducer sheath applies an outward radial force to the introducer sheath, flattening the ridges and grooves, thereby radially expanding the introducer sheath from a first diameter to a second diameter. Example 69: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 65-68, wherein the introducer sheath comprises at least one layer of a self-shrinking material. Example 70: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 69, wherein the outer diameter of the elongated main body member is in the range of less than the diameter of the central lumen of the introducer sheath. Example 71: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 70, wherein the elongated main body member comprises a lubricating material. Example 72: An introducer sheath system according to any embodiment of this specification, particularly Example 61, wherein the elongated main body member is flexible. Example 73: An introducer sheath system according to any embodiment of this specification, particularly Example 72, wherein the elongated main body member is made of a flexible material containing high-density polyethylene. Example 74: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 72, wherein the elongated main body member includes flexible features including grooves, slits, and coils extending in at least one circumferential and / or longitudinal direction. Example 75: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 74, wherein the distal end of an elongated main body member includes a tapered tip portion adapted for insertion into body tissue. Example 76: An introducer sheath system according to any example of this specification, particularly any of Examples 56 to 75, wherein the introducer includes a radiopaque marker. Example 77: An introducer sheath system according to any embodiment of this specification, particularly Example 76, wherein the radiopaque marker is located in proximity to at least one of the following positions: the tapered distal end of the elongated body member, along the elongated body member adjacent to the front end of the balloon, on the balloon, and along the elongated body member at the rear end of the balloon. Example 78: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56-77, comprising and extending through a guide wire lumen. Example 79: An introducer sheath system according to any embodiment of this specification, particularly Example 78, wherein the guidewire lumen extends along the longitudinal centerline of an elongated body member, the expansion lumen is radially offset from the guidewire lumen, and the expansion lumen extends along a first side of the guidewire lumen. Example 80: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 79, wherein the shape of the balloon in the inflated configuration includes at least one of a regular shape or an irregular shape. Example 81: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 80, wherein the shape of the balloon in the inflated configuration includes a tapered leading edge and a tapered trailing edge, the leading edge being adjacent to the distal end of an elongated body member and the trailing edge being adjacent to the proximal end of an elongated body member. Example 82: An introducer sheath system according to any embodiment of this specification, particularly Example 81, wherein the leading edge taper corresponds to the trailing edge taper. Example 83: An introducer sheath system according to any embodiment of this specification, particularly Example 81, wherein the leading edge taper is greater than the trailing edge taper. Example 84: An introducer sheath system according to any embodiment of this specification, particularly Example 81, wherein the leading edge taper is smaller than the trailing edge taper. Example 85: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 81, wherein the balloon includes a cylindrical body portion extending between a tapered leading edge and a tapered trailing edge. Example 86: An introducer sheath system according to any embodiment of this specification, particularly Example 81, wherein the balloon includes a tapered body portion extending between a tapered leading edge and a tapered trailing edge, the taper of the body portion being different from the taper of the leading edge and the trailing edge, respectively. Example 87: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 86, wherein the balloon shape in the inflated configuration includes at least one elliptical balloon, spherical balloon, square balloon, conical balloon, elongated spherical balloon, elongated conical / square balloon, elongated conical / spherical balloon, elongated conical / conical balloon, conical / square balloon, tapered balloon, stepped balloon, and offset balloon. Example 88: A cone-shaped balloon includes tapered front and rear edges; an elongated spherical balloon includes an elongated cylindrical body portion and hemispherical front and rear edges; an elongated cone / square balloon includes an elongated cylindrical body, a tapered first edge and a square second edge; an elongated cone / sphere balloon includes an elongated cylindrical body, a tapered first edge and a hemispherical second edge; an elongated cone / cone-shaped balloon includes a tapered front edge An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 87, wherein a conical / square balloon includes a tapered first edge and a square second edge, a tapered balloon includes a tapered front edge and a tapered rear edge, a stepped balloon includes a portion of varying diameter, and an offset balloon includes a height on the first side of an elongated body member that is higher than the height on the second side opposite the elongated body member. Example 89: An introducer sheath system according to any of the embodiments herein, particularly any of Examples 56 to 88, wherein the balloon is made of a polymer material. Example 90: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 89, wherein the balloon is composed of at least one of a compliant material, a semi-compliant material, and a non-compliant material. Example 91: An introducer sheath system according to any embodiment of this specification, particularly Example 90, wherein the balloon is made of a compliant material. Example 92: An introducer sheath system according to any example herein, particularly the one described in Example 91, wherein the balloon is composed of at least one of polyolefin, silicone, and polyethylene terephthalate. Example 93: An introducer sheath system according to any embodiment of this specification, particularly Example 90, wherein different parts of the balloon are composed of different compliant, semi-compliant, and non-compliant materials. Example 94: An introducer sheath system according to any embodiment of this specification, particularly Example 93, wherein the proximal portion of the balloon is made of a material with a lower degree of fit than the distal portion of the balloon, the proximal portion of the balloon is adjacent to the proximal end of an elongated body member, and the distal portion of the balloon is adjacent to the distal end of an elongated body member. Example 95: An introducer sheath system according to any embodiment of this specification, particularly Example 94, wherein at least a portion of the proximal portion of the balloon includes a tapered surface. Example 96: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 95, wherein the tapered surface is sized and configured to be positioned adjacent to the distal opening of the introducer sheath so that the tapered surface of the balloon is adapted to widen the distal end of the introducer sheath. Example 97: An introducer sheath system according to any example of this specification, any example of this specification, particularly any of Examples 56 to 96, wherein the balloon is made of an impermeable material. Example 98: An introducer sheath system according to any of the embodiments of this specification, particularly any of Examples 56 to 97, wherein the balloon is made of a permeable material. Example 99: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 98, wherein the balloon includes a mesh material that allows fluid communication between the inside and outside of the balloon. Example 100: An introducer sheath system according to any embodiment of this specification, particularly Example 99, wherein the flow rate of the expansion fluid through the mesh material of the balloon has a diameter greater than the outer diameter of the elongated body member when inflating the balloon. Example 101: An introducer sheath system according to any of the embodiments herein, particularly any of Examples 56 to 100, comprising an expanding fluid containing physiological saline. Example 102: An introducer sheath system according to any example of this specification, particularly Example 101, wherein the expansion fluid comprises a contrast agent. Example 103: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 102, wherein the balloon has a uniform thickness along the circumference and / or around the balloon. Example 104: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 103, wherein the thickness of the balloon varies along the length and / or around the circumference of the balloon. Example 105: An introducer sheath system according to any embodiment of this specification, particularly Example 104, wherein the thickness of the proximal portion of the balloon is greater than the thickness of the distal portion of the balloon, the proximal portion of the balloon is adjacent to the proximal end of the elongated main body member, and the distal portion of the balloon is adjacent to the distal end of the elongated main body member. Example 106: An introducer sheath system according to any embodiment of this specification, particularly Example 104, wherein the thickness of the distal portion of the balloon is greater than the thickness of the proximal portion of the balloon, the proximal portion of the balloon is adjacent to the proximal end of the elongated main body member, and the distal portion of the balloon is adjacent to the distal end of the elongated main body member. Example 107: An introducer sheath system according to any embodiment of this specification, particularly the one described in Example 104, wherein the balloon includes at least one circumferential band of increased thickness. Example 108: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 107, wherein the balloon is coupled to an elongated body member such that there is no breakage between the outer surface of the elongated body member and the outer surface of the balloon. Example 109: An introducer sheath system according to any embodiment of this specification, particularly any of Examples 56 to 108, wherein in the inflated configuration, the diameter of the balloon is up to about 75% larger than the diameter of the elongated body member. Example 110: An introducer sheath system according to any embodiment of this specification, particularly Example 61, wherein the maximum diameter of the balloon in the inflated configuration is about 50% greater than the diameter of the elongated body member. Example 111: A method for pre-expanding the tip of an introducer sheath, wherein an expandable introducer is placed in the central lumen of an expandable sheath, the introducer comprising an elongated body member and an inflatable balloon positioned between the proximal and distal ends of the elongated body member, the balloon being expandable from a deflated configuration to an inflated configuration, the initial diameter of the balloon corresponding to the outer diameter of the elongated body member when in the deflated configuration, and the inflated diameter of the balloon being larger than the outer diameter of the elongated body member when in the inflated configuration, the inflatable balloon and the fluid are in fluid communication. A method comprising: positioning an inflatable lumen, the inflatable lumen being sized and configured to provide an inflatable fluid to a balloon; advancing an introducer axially within the central lumen of a sheath so that an expandable balloon is axially aligned with the distal opening of the sheath; inflating the balloon to an inflated diameter such that the inflated diameter of the balloon is greater than the initial diameter of the distal opening, thereby expanding the diameter of the distal opening of the sheath; deflating the balloon; and withdrawing the introducer from the central lumen of the sheath. Example 112: Positioning the introducer within the central lumen of the sheath includes fitting at least a portion of the outer surface of the introducer to the surface of the central lumen of the sheath adjacent to the distal opening, as described in any embodiment of this specification, particularly the method of Example 111. Example 113: Any embodiment of this specification, particularly the method of Example 112, wherein the introducer is fitted to the surface of the central lumen by at least one of press-fit and interference fit. Example 114: Positioning the introducer within the central lumen of the sheath includes positioning the introducer such that the distal end of the elongated body member of the introducer passes through and extends beyond the distal opening of the central lumen, as described in any of the embodiments herein, particularly the method of any of Examples 111 to 113. Example 115: Any embodiment of this specification, particularly the method of any of Examples 111 to 114, wherein advancing the introducer axially within the central lumen of the sheath includes advancing the distal end of an elongated body member beyond the distal opening of the central lumen, and the axial movement of the elongated body member through the distal opening is limited so that the balloon axially aligns with the distal opening of the introducer sheath when the elongated body member is provided in its most distal position. Example 116: Any embodiment of this specification, particularly the method of any of Examples 111 to 115, wherein the introducer is advanced axially, and the balloon is positioned such that a first portion of the balloon extends beyond the distal opening of the sheath and a second portion of the balloon is positioned within the central lumen of the sheath. Example 117: Any embodiment of this specification, particularly the method of Example 116, wherein a second portion of the balloon includes a tapered surface adapted to extend at least a portion of the distal end of the sheath into a corresponding tapered shape. Example 118: Any embodiment of this specification, particularly the method of any of Examples 111 to 117, wherein the diameter of the distal opening of the introducer sheath when expanded is up to about 75% larger than the diameter of the distal opening of the introducer sheath when not expanded. Example 119: A method for delivering a medical device, comprising inserting an expandable sheath and an expandable introducer at least partially into the vascular structure of a patient, wherein the introducer is received within the central lumen of the sheath; advancing the introducer axially within the central lumen of the sheath such that an inflatable balloon positioned on an elongated body member of the introducer is axially aligned with the distal opening of the sheath; inflating the balloon to a diameter greater than the initial diameter of the distal opening, thereby expanding the diameter of the distal opening of the sheath; deflating the balloon; withdrawing the introducer from the central lumen of the sheath; advancing the medical device through the central lumen of the sheath; and delivering the medical device to the patient. Example 120: The method according to any embodiment of this specification, particularly the method according to Example 119, wherein during insertion, at least a portion of the outer surface of the introducer is fitted against the surface of the central lumen of the sheath adjacent to the distal opening. Example 121: Any embodiment of this specification, in particular the method of Example 120, wherein the introducer is fitted to the surface of the central lumen by at least one of press-fit and interference fit. Example 122: The method according to any embodiment of this specification, particularly the method according to any one of Examples 119 to 121, wherein the introducer is received within the central lumen of a sheath such that the distal end of the introducer extends through the distal opening of the central lumen. Example 123: Any embodiment of this specification, particularly the method of any of Examples 119-122, wherein advancing the introducer axially within the central lumen of the sheath includes advancing the distal end of an elongated body member beyond the distal opening of the central lumen, and the axial movement of the elongated body member through the distal opening is limited so that the balloon axially aligns with the distal opening of the introducer sheath when the elongated body member is provided in its most distal position. Example 124: Any embodiment of this specification, particularly the method of any of Examples 119-123, comprising advancing the introducer axially so that the balloon is positioned such that a first portion of the balloon extends beyond the distal opening of the expandable sheath and a second portion of the balloon is positioned within the central lumen of the sheath. Example 125: Any embodiment of this specification, particularly the method of any of Examples 119-124, wherein the diameter of the distal opening of the introducer sheath when expanded is up to about 75% larger than the diameter of the distal opening of the introducer sheath when not expanded. Example 126: Any embodiment of this specification, particularly the method of any of Examples 119-125, further comprising inserting a guidewire at least partially into the patient's vascular structure and advancing an introducer along the guidewire to a therapeutic position within the patient's vascular structure. Example 127: Any embodiment of this specification, particularly the method of Example 126, further comprising withdrawing a guide wire from the introducer. Example 128: The method according to any of the embodiments herein, particularly the method according to any of Examples 119 to 127, further comprising visualizing the location of at least one of an expandable sheath and an introducer within a vascular structure using an imaging modality, wherein the introducer includes a radiopaque marker located in proximity to at least one of the tapered distal end, the anterior end of the balloon, and the posterior end of the balloon. Example 129: Any embodiment of this specification, particularly the method of any one of Examples 119 to 128, wherein inflating a balloon includes providing an expansion fluid to the balloon through an expansion lumen extending through an introducer that is in fluid communication within the internal volume of the balloon. Example 130: The method according to any of the embodiments herein, particularly the method according to any of Examples 119-129, wherein the balloon includes a tapered surface adapted to expand at least a portion of the distal end of the sheath into a corresponding tapered shape. Example 131: Any embodiment of this specification, particularly the method of any of Examples 119-130, wherein withdrawing the introducer from the central lumen of the sheath includes moving the introducer axially toward the proximal end of the sheath until the introducer is completely removed from the central lumen. Example 132: The method according to any of the embodiments herein, particularly the method according to any of Examples 119-131, wherein the diameter of the distal opening of the sheath remains expanded after the balloon has deflated and the introducer has been withdrawn. Example 133: Any embodiment of this specification, particularly the method of any of Examples 119-132, further comprising: advancing a medical device through the central lumen of the sheath, the medical device applying an outward radial force against the inner surface of the central lumen; locally expanding the sheath from an initial unexpanded state to a locally expanded state; at least partially unfolding a plurality of longitudinally extending folds within the sheath during the locally expanding of the sheath; and locally folding the sheath from the locally expanded state back to at least partially folded after the passage of the medical device. Example 134: Any embodiment of this specification, particularly the method of any of Examples 119-133, further comprising advancing a medical device through the central lumen of the sheath with a smaller pushing force than required for a sheath having an unextended tip. Example 135: Any embodiment of this specification, particularly the method of any of Examples 119-134, further comprising advancing the medical device through a distal opening of a sheath to position it at a treatment site, for delivery of the medical device to the patient. Example 136: The method according to any embodiment of this specification, particularly the method according to any one of Examples 119 to 135, wherein the medical device is an artificial heart valve. Example 137: Any embodiment of this specification, particularly the method of Example 136, wherein the artificial heart valve includes a self-expanding heart valve. Example 138: Any embodiment of this specification, particularly the method of Example 136, wherein the artificial heart valve includes a balloon-expandable heart valve. Example 139: Any embodiment of this specification, particularly the method of any of Examples 119-138, further comprising removing the sheath from the patient after the medical device has been delivered to the patient. Example 140: An expansion device configured to be received within an expandable sheath, the device comprising a body including an outer surface of the body, a proximal end, and a tapered distal end located opposite the proximal end and spaced apart therefrom, a radially extending projection positioned along a portion of the body, the radially extending projection having an outer surface, and the radially extending projection having a diameter greater than the diameter of the body, the device being sized and configured to be received within the central lumen of an expandable sheath such that the radially extending projection at least partially expands a portion of the expandable sheath. Example 141: An extension device according to any embodiment of this specification, particularly Example 140, wherein the outer surface of the main body and the outer surface of radially extending protrusions include a hydrophilic coating. Example 142: An extension device according to any example of this specification, particularly Example 141, wherein the hydrophilic coating comprises a material having a low coefficient of friction. Example 143: An extension device according to any embodiment of this specification, particularly any of Examples 140 to 142, wherein radially extending projections are fixedly positioned along the length of the main body. Example 144: An extension device according to any embodiment of this specification, particularly Example 143, wherein radially extending protrusions are molded onto the outer surface of the main body. Example 145: An extension device according to any embodiment of this specification, particularly Example 143, wherein radially extending projections are fixedly positioned on a body by adhesive, fasteners, or welding. Example 146: An extension device according to any embodiment of this specification, particularly any of Examples 140 to 142, wherein radially extending projections are adjustably positioned along the length of the main body. Example 147: An expansion device according to any embodiment herein, particularly the expansion device described in Example 146, wherein the outer surface of the body includes a first plurality of screw portions extending along a portion of the length of the body, and the radially extending protrusion has an inner surface including a second plurality of screw portions corresponding to the first plurality of screw portions, the radially extending protrusion is configured to be rotationally adjustable around the body, and the radially extending protrusion is axially movable along the body by the engagement of the first and second pluralities of screw portions. Example 148: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 2F and the diameter of the radially extending protrusion is greater than 2F. Example 149: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 4F and the diameter of the radially extending protrusion is greater than 4F. Example 150: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 6F and the diameter of the radially extending protrusion is greater than 6F. Example 151: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 8F and the diameter of the radially extending protrusion is greater than 8F. Example 152: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 10F and the diameter of the radially extending protrusion is greater than 10F. Example 153: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 12F and the diameter of the radially extending protrusion is greater than 12F. Example 154: An expansion device according to any embodiment herein, particularly any of Examples 140 - 147, wherein the diameter of the body is 14F and the diameter of the radially extending protrusion is greater than 14F. Example 155: An expansion device according to any of the examples herein, particularly any of Examples 140 to 147, wherein the diameter of the body is 16F and the diameter of the radially extending protrusion is greater than 16F. Example 156: An expansion device according to any of the examples herein, particularly any of Examples 140 to 147, wherein the diameter of the body is 20F and the diameter of the radially extending protrusion is greater than 20F. Example 157: An expansion device according to any of the examples herein, particularly any of Examples 140 to 147, wherein the diameter of the body is 24F and the diameter of the radially extending protrusion is greater than 24F. Example 158: An expansion device according to any of the examples herein, particularly any of Examples 140 to 147, wherein the diameter of the body is 28F and the diameter of the radially extending protrusion is greater than 28F. Example 159: An expansion device according to any of the examples herein, particularly any of Examples 140 to 158, wherein the radially extending protrusion is disposed between the proximal end and the tapered distal end of the body. Example 160: An expansion device according to any of the examples herein, particularly Example 159, wherein the radially extending protrusion is disposed adjacent to the tapered distal end of the body. Example 161: An expansion device according to any of the examples herein, particularly Example 160, wherein the radially extending protrusion is offset from the proximal end of the tapered distal tip. Example 162: An expansion device according to any of the examples herein, particularly any of Examples 140 to 159, wherein the radially extending protrusion is disposed adjacent to the proximal end of the body. Example 163: An expansion device according to any of the examples herein, particularly Example 162, wherein the radially extending protrusion is offset from the proximal end of the body. Example 164: An expansion device according to any of the examples herein, particularly any of Examples 140 to 163, wherein the radially extending protrusion is spherical. Example 165: An expansion device according to any embodiment of this specification, particularly any of Examples 140 to 163, wherein the radially extending projection is cylindrical in shape. Example 166: An extension device according to any embodiment of this specification, particularly any of Examples 140 to 165, wherein a radially extending projection has a curved front end and a curved rear end. Example 167: An expansion device according to any embodiment of this specification, particularly any of Examples 140 to 166, wherein a radially extending projection has a tapered front end. Example 168: An expansion device according to any embodiment of this specification, particularly any of Examples 140 to 167, wherein the radially extending projection has a tapered rear end. Example 169: An extension device according to any embodiment of this specification, particularly any of Examples 140-168, wherein the device is a dilator. Example 170: An extension device according to any embodiment of this specification, particularly any of Examples 140-168, wherein the device is an introducer. Example 171: An extension device according to any embodiment of this specification, in particular Example 170, further comprising a locking mechanism positioned along the proximal end of the main body. Example 172: An extension device according to any embodiment of this specification, in particular Example 171, wherein the diameter of the locking mechanism is greater than the diameter of the main body. Example 173: An extension device according to any embodiment of this specification, particularly Example 171 or 172, wherein the locking mechanism is adjustable and can be positioned along at least a portion of the length of the body. Example 174: A sheath system comprising an expandable sheath comprising an inner layer defining a central lumen of the sheath, an outer layer at least partially extending around the inner layer, wherein the inner and outer layers transition from an unexpanded configuration and an expanded configuration; an expandable device movable within the central lumen of the sheath, the expandable device comprising a body including an outer surface, a proximal end, and a tapered distal end located opposite and spaced away from the proximal end, a radially extending projection positioned along a portion of the body, the radially extending projection having an outer surface having a diameter greater than the diameter of the body, wherein the reception of the expandable device within the central lumen of the sheath causes the sheath to locally expand at least a portion of the sheath in response to an outwardly directed radial force provided by the radially extending projection. Example 175: A sheath system according to any embodiment of this specification, particularly Example 174, wherein the outer layer is locally retracted by removing the expansion device from the central lumen of the outer layer, returning it from an expanded configuration to at least a partially unexpanded configuration. Example 176: A sheath system according to any embodiment of this specification, particularly Example 174 or 175, wherein the inner layer includes a folding portion configured to move between a folded configuration and a less folded configuration during local expansion of the sheath. Example 177: A sheath system according to any embodiment of this specification, particularly Example 176, wherein the folding portion includes a first folding region and a second folding region, and an overlapping portion extending between the first and second regions, wherein the first folding region is configured to move closer to the second folding region to shorten the overlapping portion at a local axial position during the application of outward radial force by the passage of an expansion device, and shortening the overlapping portion corresponds to a local expansion of lumens. Example 178: The sheath system according to any embodiment of this specification, particularly Example 177, wherein the first folding region is configured to move further away from the second folding region and, after the outward radial force is removed, lengthen the overlapping portion at a local axial position, and lengthening the overlapping portion corresponds to local contraction of the lumen. Example 179: A sheath system according to any embodiment of this specification, particularly Example 177 or 178, wherein the first folding region and the second folding region are spaced apart from each other in the circumferential direction, and the overlapping portion extends circumferentially between the first and second folding regions. Example 180: A sheath system according to any embodiment of this specification, particularly any of Examples 177 to 179, wherein the inner layer defines a continuous layer in the circumferential direction, the overlapping portion being radially separated from the outer surface of the non-overlapping portion of the inner layer, and the outer layer defines a discontinuous outer layer including a base portion that radially separates the overlapping portion from the outer surface of the non-overlapping portion. Example 181: A sheath system according to any embodiment of this specification, particularly any of Examples 174-180, further comprising an expandable sheath extending around an outer layer and an elastic outer cover that applies radially inward forces to the inner and outer layers. Example 182: A sheath system according to any embodiment of this specification, particularly any of Examples 174 to 181, wherein the outer surfaces of radially extending protrusions of the main body and extension device include a hydrophilic coating. Example 183: A sheath system according to any embodiment of this specification, particularly any of Examples 174 to 182, wherein radially extending projections are fixedly positioned along the length of the body. Example 184: A sheath system according to any embodiment of this specification, particularly any of Examples 174 to 182, wherein radially extending projections are adjustably positioned along the length of the body. Example 185: A sheath system according to any embodiment of this specification, particularly Example 184, wherein the outer surface of the body includes a first plurality of threaded portions extending along a portion of the length of the body, and a radially extending projection has an inner surface including a second plurality of threaded portions corresponding to the first plurality of threaded portions, the radially extending projection is configured to be rotatably adjustable about the length of the body, and the radially extending projection is axially movable along the body by engagement of the first and second plurality of threaded portions. Example 186: A sheath system according to any embodiment of this specification, particularly any of Examples 174 to 185, wherein the expandable sheath includes a strain relief portion adjacent to the proximal end of the sheath and an elongated body portion extending between the strain relief and the distal end of the sheath, wherein the strain relief portion has a larger diameter than the elongated body portion of the sheath, and the diameter of a radially extending projection is larger than the diameter of the strain relief portion. Example 187: A sheath system according to any embodiment of this specification, particularly the one described in Example 186, wherein the distal end of the strain relief portion includes a reduced taper between the diameter of the strain relief portion and the diameter of the elongated body portion. Example 188: A sheath system according to any embodiment of this specification, particularly any of Examples 174 to 187, wherein the expansion device further includes a locking mechanism for engaging with the sheath and fixing the axial position of the expansion device within the central lumen of the sheath. Example 189: A sheath system according to any embodiment of this specification, particularly the one described in Example 188, wherein an expandable sheath is connected to a sheath hub at its proximal end, and a locking mechanism engages with the sheath hub to fix the axial position of the expansion device within the central lumen of the sheath. Example 190: A method for locally dilating an expandable sheath, comprising: introducing an expansion device into the central lumen of the expandable sheath; introducing the combined expandable sheath and expansion device into a patient's blood vessel; and advancing the expansion device distally within the central lumen of the expandable sheath to locally dilate the lumen of the sheath at a local axial position corresponding to the axial position of a radially extending projection provided to the expansion device. Example 191: The method according to any embodiment of this specification, particularly Example 190, wherein introducing an expansion device into the central lumen of an expandable sheath includes positioning the expansion device within the central lumen of the sheath such that a radially extending projection is located at least within the strain relief portion of the expandable sheath. Example 192: Any embodiment of this specification, particularly the method of Example 191, further comprising locally expanding the lumen of the sheath to advance the expansion device beyond the strain relief portion of the sheath to the elongated body portion of the sheath. Example 193: Any embodiment of this specification, particularly the method of any of Examples 190-192, further comprising removing the expansion device from an expandable sheath such that the outer diameter of the sheath is greater than the initial, unexpanded diameter of the sheath. Example 194: Any embodiment of this specification, particularly the method of Example 193, further comprising inserting a medical device into the central lumen of an expandable sheath. Example 195: A method for locally dilating an expandable sheath, comprising introducing the expandable sheath into a patient's blood vessel, wherein the expandable sheath has a central lumen; introducing an expansion device into the central lumen of the expandable sheath; and advancing the expansion device distally within the central lumen of the expandable sheath to locally dilate the lumen of the sheath at a local axial position corresponding to the axial position of a radially extending projection provided to the expansion device. Example 196: The method according to any embodiment of this specification, particularly the method according to Example 195, wherein introducing an expansion device into the central lumen of an expandable sheath includes positioning the expansion device within the central lumen of the sheath such that a radially extending projection is located at least within the strain relief portion of the expandable sheath. Example 197: Any embodiment of this specification, particularly the method of Example 196, further comprising locally expanding the lumen of the sheath to advance the expansion device beyond the strain relief portion of the sheath to the elongated body portion of the sheath. Example 198: Any embodiment of this specification, particularly the method of any of Examples 195-197, further comprising removing the expansion device from an expandable sheath such that the outer diameter of the sheath is greater than the initial, unexpanded diameter of the sheath. Example 199: Any embodiment of this specification, particularly the method of Example 198, further comprising inserting a medical device into the central lumen of an expandable sheath.

[0190] Given the many possible ways in which the principles of disclosure may apply, it should be recognized that the illustrated embodiments are merely preferred examples of the disclosure and should not be interpreted as limiting the scope of the disclosure. Rather, the scope of this disclosure is defined by the following claims. Accordingly, everything within the scope of these claims and intent is asserted as a disclosure.

Claims

1. 1. An extensible introducer, comprising: an elongated body member; an inflatable balloon disposed between the proximal and distal ends of the elongate body member, the balloon being expandable from a deflated configuration to an inflated configuration; an inflation lumen in fluid communication with the inflatable balloon, the inflation lumen being sized and configured to provide inflation fluid to the balloon; In the deflated configuration, an outer diameter of the balloon corresponds to an outer diameter of the elongate body member, and in the inflated configuration, the outer diameter of the balloon is greater than the outer diameter of the elongate body member; at least a portion of the balloon is sized and configured to pass through a distal opening of an expandable introducer sheath when the balloon is in the deflated configuration, and the balloon is sized and configured to expand at least a portion of the distal end of the introducer sheath when the balloon is inflated; axial movement of the elongate body member through the distal opening is restricted such that the balloon is axially aligned with the distal opening of the introducer sheath when the elongate body member is provided in its distal-most position; when the elongate body member is in the distal-most position, a first portion of the balloon extends beyond the distal opening of the introducer sheath and a second portion of the balloon resides within a central lumen of the introducer sheath; the second portion of the balloon is sized and configured to expand at least a portion of the distal end of the introducer sheath when the balloon expands from the deflated configuration to the inflated configuration; An expandable introducer, wherein the second portion of the balloon includes a tapered surface adapted to expand at least a portion of the distal end of the introducer sheath in a corresponding tapered shape.

2. the introducer sheath includes at least one polymer layer including a plurality of longitudinally extending folds when the sheath is at a first diameter; 2. The expandable introducer of claim 1, wherein a medical device passing through the central lumen of the introducer sheath applies an outward radial force to the introducer sheath, causing the introducer sheath to radially expand from the first diameter to the second diameter by at least partially unfolding the plurality of longitudinally extending folds.

3. The expandable introducer of claim 1 or 2, wherein the elongate body member includes flexibility features including at least one circumferentially and / or longitudinally extending groove, slit, and coil.

4. The expandable introducer of any one of claims 1 to 3, wherein the introducer includes a radiopaque marker located near at least one of the tapered distal end of the elongate body member, along the elongate body member near the leading end of the balloon, on the balloon, and along the elongate body member at the trailing end of the balloon.

5. 5. The expandable introducer of claim 1, wherein the shape of the balloon in the inflated configuration comprises at least one of an elliptical balloon, a spherical balloon, a square balloon, a conical balloon, an elongated spherical balloon, an elongated conical / square balloon, an elongated conical / spherical balloon, an elongated conical / conical balloon, a conical / square balloon, a tapered balloon, a stepped balloon, and an offset balloon.

6. the cone-shaped balloon includes tapered leading and trailing edges; the elongated spherical balloon includes an elongated cylindrical body portion and hemispherical leading and trailing edges; the elongated conical / square balloon comprises an elongated cylindrical body, a tapered first edge, and a square second edge; the elongated conical / spherical balloon comprises an elongated cylindrical body, a tapered first edge, and a hemispherical second edge; the elongated conical / cone-shaped balloon includes tapered leading and trailing edges; the conical / square balloon includes a tapered first edge and a square second edge; the tapered balloon includes a tapered leading edge and a tapered trailing edge; the stepped balloon includes portions of varying diameter; The expandable introducer of claim 5 , wherein the offset balloon comprises a height on a first side of the elongate body member that is greater than a height on an opposite second side of the elongate body member.

7. 7. The expandable introducer of claim 1, wherein a proximal portion of the balloon is constructed from a less compliant material than a distal portion of the balloon, the proximal portion of the balloon is adjacent the proximal end of the elongate body member, and the distal portion of the balloon is adjacent the distal end of the elongate body member.

8. 1. An introducer sheath system, comprising: an expandable introducer sheath for deploying a medical device; an introducer received within a central lumen of the introducer sheath and axially and rotationally movable therein, the introducer comprising: an elongate body member having a proximal end and a tapered distal end; an inflatable balloon disposed between the proximal end and the distal end of the elongate body member, the balloon being expandable from a deflated configuration to an inflated configuration; and an inflation lumen in fluid communication with the inflatable balloon, the inflation lumen being sized and configured to provide inflation fluid to the balloon; In the deflated configuration, an outer diameter of the balloon corresponds to an outer diameter of the elongate body member, and in the inflated configuration, the outer diameter of the balloon is greater than the outer diameter of the elongate body member; at least a portion of the balloon is sized and configured to pass through a distal opening of the introducer sheath when the balloon is in the deflated configuration, and the balloon expands at least a portion of the distal end of the introducer sheath when the balloon is inflated, increasing the diameter of the distal opening; a first portion of the balloon extends beyond the distal opening of the introducer sheath when the elongate body member is in its distal-most position, and a second portion of the balloon resides within the central lumen of the introducer sheath, the second portion of the balloon being sized and configured to span at least a portion of the distal end of the introducer sheath when the balloon expands from the deflated configuration to the inflated configuration; An introducer sheath system, wherein the second portion of the balloon includes a tapered surface adapted to expand at least a portion of the distal end of the introducer sheath in a corresponding tapered shape.

9. the introducer sheath includes at least one polymer layer including a plurality of longitudinally extending folds when the sheath is at a first diameter; 9. The introducer sheath system of claim 8, wherein a medical device passing through the central lumen of the introducer sheath applies an outward radial force to the introducer sheath, causing the introducer sheath to radially expand from the first diameter to the second diameter by at least partially unfolding the plurality of longitudinally extending folds.

10. 10. The introducer sheath system of claim 8 or 9, wherein the shape of the balloon in the inflated configuration comprises at least one of an elliptical balloon, a spherical balloon, a square balloon, a conical balloon, an elongated spherical balloon, an elongated conical / square balloon, an elongated conical / spherical balloon, an elongated conical / conical balloon, a conical / square balloon, a tapered balloon, a stepped balloon, and an offset balloon.

11. the cone-shaped balloon includes tapered leading and trailing edges; the elongated spherical balloon includes an elongated cylindrical body portion and hemispherical leading and trailing edges; the elongated conical / square balloon comprises an elongated cylindrical body, a tapered first edge, and a square second edge; the elongated conical / spherical balloon comprises an elongated cylindrical body, a tapered first edge, and a hemispherical second edge; the elongated conical / cone-shaped balloon includes tapered leading and trailing edges; the conical / square balloon includes a tapered first edge and a square second edge; the tapered balloon includes a tapered leading edge and a tapered trailing edge; the stepped balloon includes portions of varying diameter; The introducer sheath system of claim 10 , wherein the offset balloon comprises a height on a first side of the elongate body member that is greater than a height on an opposite second side of the elongate body member.

12. 12. The introducer sheath system of claim 8, wherein a proximal portion of the balloon is constructed from a less compliant material than a distal portion of the balloon, the proximal portion of the balloon is adjacent the proximal end of the elongate body member, and the distal portion of the balloon is adjacent the distal end of the elongate body member.

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