Expandable Sheath

Abstract

Disclosed herein are expandable sheaths. In some embodiments, a braided layer is positioned radially outward from a first polymer layer. The braided layer comprises a plurality of filaments braided together. A second polymer layer is positioned radially outward from the braided layer, and the braided layer is encapsulated between the first and second polymer layers. In some embodiments, the braided layer is adhered to a sealing layer that is not permeable to blood flow. Also disclosed are methods of making and using the devices disclosed herein, as well as crimping devices that can be used in the methods of making the devices disclosed herein.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 62 / 912,569, filed October 8, 2019, which is incorporated herein by reference in its entirety.

[0002] The present application relates to an expandable introducer sheath for prosthetic devices such as transcatheter heart valves and methods for making the same. [Background technology]

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

[0004] Introducer sheaths can be used to safely introduce a delivery device into a patient's blood vessel (e.g., the femoral artery). Typically, an introducer sheath includes an elongated sleeve inserted into the vessel and a housing containing one or more sealing valves that allow the delivery device to be placed in fluid communication with the vessel with minimal blood loss. Such introducer sheaths can be radially expandable. However, they tend to have complex mechanisms, such as ratcheting mechanisms, that maintain the sheath in an expanded configuration when a device with a diameter larger than the diameter of the sheath's body is introduced. Additionally, existing expandable sheaths can tend to elongate axially as a result of the application of longitudinal forces associated with passing a prosthetic device through the sheath. Such elongation results in a corresponding reduction in the sheath diameter, thereby increasing the force required to thread the prosthetic device through the narrower sheath. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent Application Publication No. 2012 / 0123529 [Patent Document 2] U.S. Patent Application Publication No. 2012 / 0239142 [Patent Document 3] U.S. Patent Application Publication No. 2018 / 0153689 [Patent Document 4] U.S. Patent Application Serial No. 16 / 378,417 [Patent Document 5] U.S. Patent Application Publication No. 2014 / 0379067 [Patent Document 6] U.S. Patent Application Publication No. 2016 / 0296730 [Patent Document 7] U.S. Patent Application Publication No. 2018 / 0008407 [Patent Document 8] U.S. Patent Application No. 14 / 880,109 [Patent Document 9] U.S. Patent Application Serial No. 14 / 880,111 Summary of the Invention [Problem to be solved by the invention]

[0006] Thus, there remains a need in the art for improved introducer sheaths for endovascular systems used to implant valves and other prosthetic devices. [Means for solving the problem]

[0007] The expandable sheath disclosed herein includes a first polymer layer, a braided layer radially outward from the first polymer layer (the braided layer including a plurality of filaments braided together), and a second polymer layer radially outward from the braided layer. The second polymer layer can be bonded to the first polymer layer such that the braided layer is encapsulated between the first and second polymer layers. When a medical device passes through the sheath, the diameter of the sheath expands from a first diameter to a second diameter around the medical device.

[0008] In some embodiments, as the medical device passes through the sheath, the diameter of the sheath expands from a first diameter to a second diameter around the medical device while resisting axial elongation of the sheath so that the length of the sheath remains substantially constant.

[0009] In some embodiments, the first and second polymeric layers include a plurality of longitudinally extending folds when the sheath is at the first diameter. The longitudinally extending folds form a plurality of circumferentially spaced ridges and a plurality of circumferentially spaced grooves. The ridges and grooves may flatten to radially expand the sheath when a medical device is passed through the sheath.

[0010] In some embodiments, a portion of the first polymer layer and / or a portion of the second polymer layer comprises an elastomeric coating.

[0011] In some embodiments, the filaments of the braided layer are movable between the first and second polymer layers such that the braided layer can expand radially when the medical device is passed through the sheath. The length of the sheath can remain substantially constant as the braided layer expands radially. In some embodiments, the filaments of the braided layer are elastically buckled when the sheath is at a first diameter, and the first and second polymer layers are attached to each other at a plurality of spaces between the filaments of the braided layer. In some embodiments, the braided layer comprises a self-contracting material. In some embodiments, at least a portion of the plurality of filaments comprises an elastomeric coating.

[0012] Some embodiments of the expandable sheath can include an outer covering formed from a heat shrink material and extending over at least a longitudinal portion of the first polymeric layer, the braided layer, and the second polymeric layer, and the outer covering can include one or more longitudinally extending slits, weakened portions, or score lines.

[0013] Some embodiments of the expandable sheath include a buffer layer positioned between the braided layer and the adjacent polymer layer. The buffer layer dissipates radial forces acting between the filaments of the braided layer and the adjacent polymer layer. A first buffer layer may be positioned between the braided layer and the first polymer layer, and a second buffer layer may be positioned between the braided layer and the second polymer layer. These buffer layers may have a thickness of, for example, about 80 microns to about 1000 microns. Some embodiments of the buffer layer may include a porous interior region. The buffer layer may further include a sealed surface positioned between the porous interior region and the adjacent polymer layer, the sealed surface having a higher melting point than the adjacent polymer layer. The sealed surface may also be thinner than the porous interior region of the buffer layer. In some embodiments, the sealed surface is a sealing layer attached to the buffer layer. In some embodiments, the sealed surface is a surface of the buffer layer, and the sealed surface of the buffer layer is continuous with and formed from the same material as the porous interior region of the buffer layer.

[0014] Other embodiments of the expandable sheath can include a braided layer (comprising multiple filaments braided together) and a first expandable sealing layer adhered to a portion of the filaments of the braided layer. This sealing layer is impermeable to blood flow. When a medical device passes through the sheath, the diameter of the sheath expands from a first diameter to a second diameter around the medical device. In some embodiments, a second expandable sealing layer can be adhered to a portion of the filaments of the braided layer. The second expandable sealing layer can be positioned on the opposite side of the braided layer from the first expandable sealing layer. In some embodiments, the braided layer includes a self-contracting material, and the expandable sealing layer has a thickness that varies along the length of the sheath.

[0015] In some embodiments, at least a portion of the plurality of filaments comprises a seal coating instead of or in addition to one or both of the seal layers.

[0016] Also disclosed herein are methods of making an expandable sheath. One embodiment of a method of making an expandable sheath includes disposing a braided layer radially outward of a first polymer layer located on a mandrel, the mandrel having a first diameter; applying a second polymer layer radially outward of the braided layer; and applying heat and pressure to the first polymer layer, the braided layer, and the second polymer layer, such that the first polymer layer and the second polymer layer are bonded to one another and encapsulate the braided layer to form the expandable sheath. The method further includes removing the expandable sheath from the mandrel, such that the expandable sheath may be at least partially radially contracted to a second diameter smaller than the first diameter.

[0017] In some embodiments, an elastomeric coating can be applied to a portion of the plurality of filaments. In some embodiments, an elastomeric coating can be applied to a portion of the first polymer layer and / or a portion of the second polymer layer.

[0018] Some embodiments of the method of making an expandable sheath may include shape-setting the braided layer to a contracted diameter prior to disposing the braided layer radially outward of the first polymer layer.

[0019] In some embodiments of the method of making an expandable sheath, the step of applying heat and pressure further includes placing the mandrel in a container containing a heat-expandable material, heating the heat-expandable material in the container, and applying a radial pressure of 100 MPa or more against the mandrel through the heat-expandable material.

[0020] In some embodiments of the method of making an expandable sheath, the step of applying heat and pressure further includes applying a heat shrink tubing layer over the second polymer layer and applying heat to the heat shrink tubing layer.

[0021] Some embodiments of a method of making an expandable sheath can include radially contracting the sheath to a second diameter, thereby elastically buckling the filaments of the braided layer.

[0022] Some embodiments of a method of making an expandable sheath may include sealing a surface of a buffer layer and applying the buffer layer such that the sealed surface contacts the first polymer layer or the second polymer layer.

[0023] Some embodiments of the method of making the expandable sheath can include crimping the expandable sheath to a third diameter, the third diameter being smaller than the first diameter and the second diameter.

[0024] Additionally, some other embodiments describe sheaths that further comprise a distal end portion having a predefined length and comprising two or more layers.

[0025] In still other embodiments, as disclosed herein, the distal end portion may extend distally beyond the longitudinal portion of the sheath that comprises the braided layer.

[0026] Further disclosed herein are embodiments in which the distal end portion comprises an inner polymeric layer and an outer polymeric layer.

[0027] In a further embodiment, the distal end portion may further comprise an outer cover.

[0028] In a further embodiment, a portion of the distal end portion may consist of a portion of the distal end of the braided layer.

[0029] Additionally, an embodiment is disclosed in which a portion of the distal end of the braided layer comprises a loop.

[0030] In some embodiments disclosed herein, the outer cover can have a melting temperature that is lower than the melting temperature of the inner polymeric layer.

[0031] In other embodiments, the outer cover can have a melting temperature that is less than the melting temperature of the outer polymeric layer.

[0032] In a further embodiment, the outer cover may include low density polyethylene.

[0033] Additionally, embodiments are described herein in which a portion of the sheath proximal to the distal end portion of the sheath does not include an outer covering.

[0034] In still other embodiments described herein, a portion of the sheath extending from the proximal end of the sheath to a portion of the sheath proximal to the distal end portion of the sheath does not include an outer covering.

[0035] Some embodiments include a sheath that includes at least one attachment area between the distal end portion and a portion of the sheath proximal to the distal end.

[0036] In yet another embodiment, the mounting area is a circumferential mounting area.

[0037] However, in other embodiments, the mounting area comprises a plurality of circumferentially spaced mounting areas.

[0038] Additionally, an embodiment is disclosed in which the distal end portion of the sheath comprises a first plurality of folds present in the inner layer.

[0039] In other embodiments, the distal end portion of the sheath includes a second plurality of folds present in the outer layer.

[0040] In a further embodiment, the distal end portion of the sheath may include a third plurality of folds present in the outer cover.

[0041] Additionally, embodiments are disclosed in which the folds in the third plurality of folds present in the outer cover are at least partially attached to one another.

[0042] Additionally, in an embodiment, a method of forming a distal end portion of a sheath is disclosed. In such exemplary embodiment, the method includes the steps of pre-crimping a distal end portion of a sheath disclosed herein to a first diameter, the distal end portion extending distally beyond a longitudinal portion of the sheath comprising a braided layer and comprising inner and outer polymer layers, the inner and outer polymer layers exhibiting a first melt temperature; covering the pre-crimped distal end portion with an outer covering, the outer covering exhibiting a second melt temperature, the second melt temperature being lower than the first melt temperature; and covering the outer covering with an outer covering. The method includes the steps of heating at least a portion of the pre-crimped distal end portion to a first temperature, the first temperature being equal to or greater than a first melting temperature, thereby forming at least one attachment area between the outer cover and the inner and outer polymer layers; inserting a mandrel into a lumen of at least a portion of the distal end portion and further crimping at least a portion of the distal end portion to a second diameter; and heating at least a portion of the distal end portion to a second temperature, the second temperature being equal to or greater than the second melting temperature.

[0043] Further disclosed are embodiments in which the second temperature is less than the first melting temperature.

[0044] In some embodiments, the second diameter is smaller than the first diameter.

[0045] Some embodiments of the methods disclosed herein include that the crimping step may form a plurality of folds along the outer cover.

[0046] In yet other embodiments, the inner and outer polymeric layers comprise a plurality of folds.

[0047] In a further exemplary embodiment, the folds in the inner and outer polymer layers are formed in a pre-crimping step, while in other exemplary embodiments, the folds in the inner and outer polymer layers are formed in a crimping step.

[0048] Further disclosed herein are embodiments in which the heating to the second temperature forms attachments between at least a portion of the plurality of folds in the outer cover relative to one another.

[0049] Still other embodiments of the methods disclosed herein include applying a body of heat shrink material to at least a portion of the crimped distal end portion.

[0050] In further embodiments, the step of applying the heat shrink material is performed before the step of heating to the second temperature, while in still other embodiments the step of applying the heat shrink material is performed during the step of heating to the second temperature, while in still further embodiments the step of applying the heat shrink material is performed after the step of heating to the second temperature.

[0051] Still other embodiments disclosed herein include removing the body of heat shrink material after attachments of at least a portion of the plurality of folds in the outer cover to one another are formed.

[0052] In a further embodiment, the body of heat shrink material can be a tube or a tape. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 illustrates a delivery system for a prosthetic cardiovascular device according to one embodiment. [Figure 2] 2A-2C illustrate an expandable sheath that may be used in combination with the delivery system of FIG. 1, according to one embodiment. [Figure 3]FIG. 3 is an enlarged view of a portion of the expandable sheath of FIG. 2. [Figure 4] FIG. 3 is a side elevational cross-sectional view of a portion of the expandable sheath of FIG. 2. [Figure 5A] 3 is an enlarged view of a portion of the expandable sheath of FIG. 2 with the outer layer removed for purposes of illustration. [Figure 5B] 3 is an enlarged view of a portion of the braided layer of the sheath of FIG. 2. [Figure 6] 3 is an enlarged view of a portion of the expandable sheath of FIG. 2 showing the expansion of the sheath as a prosthetic device is advanced through the sheath. [Figure 7] 3 is an enlarged partial cross-sectional view showing the constituent layers of the sheath of FIG. 2 disposed on a mandrel. [Figure 8] FIG. 10 is an enlarged view of another embodiment of an expandable sheath. [Figure 9] 1 is a cross-sectional view of a device that can be used to form an expandable sheath according to one embodiment. [Figure 10A] 10A-10C illustrate another embodiment of a braided layer configured such that the filaments of the braided layer buckle when the sheath is in a radially contracted state. [Figure 10B] 10A-10C illustrate another embodiment of a braided layer configured such that the filaments of the braided layer buckle when the sheath is in a radially contracted state. [Figure 10C] 10A-10C illustrate another embodiment of a braided layer configured such that the filaments of the braided layer buckle when the sheath is in a radially contracted state. [Figure 10D] 10A-10C illustrate another embodiment of a braided layer configured such that the filaments of the braided layer buckle when the sheath is in a radially contracted state. [Figure 11] FIG. 1 is a side cross-sectional view of an assembly of an expandable sheath with a vascular dilator. [Figure 12] 12A-12C show a vascular dilator of the assembly embodiment of FIG. 11. [Figure 13] FIG. 10 is a side view of another assembly embodiment comprising an expandable sheath and a vascular dilator. [Figure 14]14 is a side view of the assembly embodiment of FIG. 13 with the vascular dilator pushed partially away from the expandable sheath. [Figure 15] 14 is a side view of the assembly embodiment of FIG. 13 with the vascular dilator pushed completely away from the expandable sheath. [Figure 16] 14 is a side view of the assembly embodiment of FIG. 13 with the vascular dilator retracted into the expandable sheath. [Figure 17] 14 is a side view of the assembly embodiment of FIG. 13 with the vascular dilator further retracted into the expandable sheath. [Figure 18] 14 is a side view of the assembly embodiment of FIG. 13 with the vascular dilator fully retracted into the expandable sheath. [Figure 19] FIG. 10 is a side cross-sectional view of another assembly embodiment comprising an expandable sheath and a vascular dilator. [Figure 20] FIG. 1 illustrates one embodiment of a vascular dilator that may be used in combination with the expandable sheath described herein. [Figure 21] FIG. 1 illustrates one embodiment of a vascular dilator that may be used in combination with the expandable sheath described herein. [Figure 22] FIG. 1 is a side view, partially broken away to show a partial cross section, of one embodiment of an expandable sheath having an outer cover and a flared portion. [Figure 23] 10A-10C show an example embodiment of an outer cover having longitudinal score lines. [Figure 24] 1A-1C show end portions of one embodiment of the braided layer of the expandable sheath. [Figure 25A] 10A-10C are perspective views of an embodiment of a roller-based crimping mechanism for crimping an expandable sheath. [Figure 25B] 25B is a side view of the disc-shaped roller and connector of the crimping mechanism shown in FIG. 25A. [Figure 25C] 25B is a top view of the disc-shaped rollers and connector of the crimping mechanism shown in FIG. 25A. [Figure 26] 1 illustrates one embodiment of a device for crimping an elongate expandable sheath, with the circled portion of the device enlarged as an illustration on the left side of the figure. [Figure 27] 1A-1C show an embodiment of an expandable sheath having an inner layer with score lines. [Figure 28] 13A-13C illustrate further embodiments of the braided layer of the expandable sheath. [Figure 29] 10A-10C are perspective views of further expandable sheath embodiments. [Figure 30] 30 is a perspective view of the embodiment of FIG. 29 with the outer heat shrink tubing layer partially cut away from the inner sheath layer. [Figure 31] FIG. 10 is a side view of an embodiment of a sheath before a delivery system is moved therethrough. [Figure 32] FIG. 10 is a side view of a sheath embodiment with the heat shrink tubing layer split by moving a delivery system through it. [Figure 33] FIG. 10 is a side view of a sheath embodiment in which the delivery system has been moved completely through, splitting the heat shrink tubing layer completely along the length of the sheath. [Figure 34] 12A is a perspective view of a sheath embodiment with a distal end portion folded around an introducer. FIG. [Figure 35] FIG. 10 is an enlarged cross-sectional view of the distal end portion folded around the introducer. [Figure 36] FIG. 10 is a cross-sectional view of an embodiment of an additional expandable sheath. [Figure 37] FIG. 1 illustrates one embodiment of a buffer layer. [Figure 38] 10A and 10B illustrate other embodiments of the buffer layer. [Figure 39] FIG. 10 is a side view of an embodiment of an additional expandable sheath. [Figure 40] FIG. 40 is a longitudinal cross-sectional view of the embodiment of FIG. 39. [Figure 41] FIG. 10 is a transverse cross-sectional view of an embodiment of an additional expandable sheath. [Figure 42] FIG. 10 is a partial longitudinal cross-sectional view of an embodiment of an additional expandable sheath. [Figure 43] FIG. 10 is a transverse cross-sectional view of an embodiment of an additional expandable sheath in an expanded state. [Figure 44] 44 is a transverse cross-sectional view of the embodiment of the expandable sheath of FIG. 43 during the crimping process. [Figure 45] FIG. 44 is a perspective view of an embodiment of a sheath similar to that of FIG. 43 in an expanded state. [Figure 46] FIG. 44 is a perspective view of an embodiment of a sheath similar to that of FIG. 43 in a folded and compressed state. [Figure 47] FIG. 10 illustrates an embodiment of an additional braided layer. DETAILED DESCRIPTION OF THE INVENTION

[0054] The expandable introducer sheath described herein can be used to deliver a prosthetic device through a patient's blood vessels to a procedure site within the body. The sheath can be configured to have high radial expandability and contractibility while limiting axial stretching of the sheath and therefore undesirable narrowing of the lumen. In one embodiment, the expandable sheath includes a braided layer, one or more relatively thin inelastic polymer layers, and an elastic layer. The sheath can elastically expand from its original diameter to an expanded diameter when a prosthetic device is advanced through the sheath, and can return to its original diameter under the influence of the elastic layer once the prosthetic device has passed. In some embodiments, one or more polymer layers can be configured to engage the braided layer, allowing radial expansion of the braided layer while preventing axial stretching of the braided layer that would otherwise result in sheath stretching and narrowing.

[0055] FIG. 1 illustrates a representative delivery apparatus 10 for delivering a medical device, such as a prosthetic heart valve or other artificial implant, to a patient. The delivery apparatus 10 is merely exemplary and may be used in combination with any of the expandable sheath embodiments described herein. Similarly, the sheaths described herein may be used in combination with any of a variety of known delivery apparatuses. The illustrated delivery apparatus 10 may generally include a steerable guide catheter 14 and a balloon catheter 16 extending therethrough. A prosthetic device, such as a prosthetic heart valve 12, may be positioned on the distal end of the balloon catheter 16. The guide catheter 14 and the balloon catheter 16 may be configured to slide longitudinally relative to one another to facilitate delivery and positioning of the prosthetic heart valve 12 within the patient's body at an implantation site. The guide catheter 14 includes a handle portion 18 and an elongated guide tube or guide shaft 20 extending from the handle portion 18.

[0056] The prosthetic heart valve 12 can be delivered into a patient's body in a radially compressed configuration and radially expanded to a radially expanded configuration at a desired deployment site. In the illustrated embodiment, the prosthetic heart valve 12 is a plastically expandable prosthetic valve that is delivered into a patient's body in a radially compressed configuration on a balloon of a balloon catheter 16 (as shown in FIG. 1 ) and then radially expanded to a radially expanded configuration at the deployment site by inflating the balloon (or by activating another type of expansion device on the delivery apparatus). Further details regarding plastically expandable heart valves that can be implanted using the devices disclosed herein are disclosed in U.S. Patent Application Publication No. 2012 / 0123529, which is incorporated herein by reference. In other embodiments, the prosthetic heart valve 12 can be a self-expanding heart valve that is constrained in a radially compressed configuration by a sheath or other component of the delivery apparatus and self-expands to a radially expanded configuration upon release by the sheath or other component of the delivery apparatus. Further details regarding self-expanding heart valves that can be implanted using the devices disclosed herein are disclosed in U.S. Patent Application Publication No. 2012 / 0239142, which is incorporated herein by reference. In yet other embodiments, the prosthetic heart valve 12 can be a mechanically expandable heart valve that includes multiple struts connected by hinge or pivot joints and is expandable from a radially compressed configuration to a radially expanded configuration by actuating an expansion mechanism that applies an expansion force to the prosthetic valve.

[0057] Further details regarding mechanically expandable heart valves that can be implanted using the devices disclosed herein are disclosed in U.S. Patent Application Publication No. 2018 / 0153689, which is incorporated herein by reference. In still other embodiments, a prosthetic valve can incorporate two or more of the above-described techniques. For example, a self-expanding heart valve can be used in combination with an expansion device to assist in the expansion of the prosthetic heart valve.

[0058] FIG. 2 illustrates an assembly 90 (which may also be referred to as an introducer device or introducer assembly) that may be used to introduce the delivery apparatus 10 and prosthetic device 12 into a patient's body, according to one embodiment. The introducer device 90 may include a housing 92 located at the proximal end of the device and an expandable sheath 100 extending distally from the housing 92. The housing 92 may function as a handle for the device. The expandable sheath 100 has a central lumen 112 ( FIG. 4 ) for guiding the passage of a delivery apparatus for a prosthetic heart valve. Typically, during use, the distal end of the sheath 100 is passed through the patient's skin and inserted into a blood vessel, such as the femoral artery. The delivery apparatus 10, together with its implant 12, may then be inserted through the housing 92 and sheath 100 and advanced through the patient's blood vessel to the treatment site where the implant is to be delivered and implanted within the patient. In some embodiments, the introducer housing 92 may include a hemostatic valve that forms a seal around the outer surface of the guide catheter 14 when inserted through the housing, thereby preventing leakage of pressurized blood.

[0059] In alternative embodiments, introducer device 90 need not include housing 92. For example, sheath 100 can be an integral part of a component of delivery apparatus 10, such as a guide catheter. For example, the sheath can extend from the handle 18 of the guide catheter. Additional examples of introducer devices and expandable sheaths can be found in U.S. Patent Application No. 16 / 378,417, which is incorporated herein by reference in its entirety.

[0060] FIG. 3 shows the expandable sheath 100 in further detail. With reference to FIG. 3, the sheath 100 can have an original, unexpanded outer diameter D1. In some embodiments, the expandable sheath 100 can include multiple coaxial layers extending along at least a portion of the sheath's length L (FIG. 2). For example, with reference to FIG. 4, the expandable sheath 100 can include a first layer 102 (also referred to as an inner layer), a second layer 104 disposed around and radially outward from the first layer 102, a third layer 106 disposed around and radially outward from the second layer 104, and a fourth layer 108 (also referred to as an outer layer) disposed around and radially outward from the third layer 106. In the illustrated configuration, the inner layer 102 can define a sheath lumen 112 extending along a central axis 114.

[0061] 3 , when the sheath 100 is in an unexpanded state, the inner layer 102 and / or the outer layer 108 may form longitudinally extending folds or wrinkles, and the surface of the sheath comprises a plurality of ridges 126 (also referred to herein as “folds”). These ridges 126 may be circumferentially spaced apart from one another by longitudinally extending grooves 128. When the sheath expands beyond its original diameter D1, the ridges 126 and grooves 128 may flatten or disappear as the surface radially expands and increases in circumference, as described further below. When the sheath contracts back to its original diameter, the ridges 126 and grooves 128 may reform.

[0062] In some embodiments, the inner layer 102 and / or the outer layer 108 may comprise relatively thin layers of polymeric material. For example, in some embodiments, the thickness of the inner layer 102 can be between 0.01 mm and 0.5 mm, 0.02 mm and 0.4 mm, or 0.03 mm and 0.25 mm. In some embodiments, the thickness of the outer layer 108 can be between 0.01 mm and 0.5 mm, 0.02 mm and 0.4 mm, or 0.03 mm and 0.25 mm.

[0063] In some embodiments, the inner layer 102 and / or the outer layer 108 may comprise a lubricious material, a low-friction material, and / or a relatively inelastic material. In certain embodiments, the inner layer 102 and / or the outer layer 108 may comprise a polymeric material having a modulus of elasticity of 400 MPa or greater. Example materials may include ultra-high molecular weight polyethylene (UHMWPE) (e.g., Dyneema®), high molecular weight polyethylene (HMWPE), or polyetheretherketone (PEEK). With respect to the inner layer 102 in particular, such low-friction materials may facilitate the passage of prosthetic devices through the lumen 112. Other suitable materials for the inner and outer layers may include polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), ethylenetetrafluoroethylene (ETFE), nylon, polyethylene, polyether block amide (e.g., Pebax), and / or any combination of the above. Some embodiments of the sheath 100 may include a lubricious liner on the inner surface of the inner layer 102. Examples of suitable lubricious 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. Suitable materials for the lubricious liner also include other materials that desirably have a coefficient of friction of 0.1 or less.

[0064] Additionally, some embodiments of the sheath 100 may include an external hydrophilic coating on the outer surface of the outer layer 108. Such a hydrophilic coating may facilitate insertion of the sheath 100 into a patient's blood vessel and reduce the likelihood of injury. Examples of suitable hydrophilic coatings include Harmony™ Advanced Lubricity Coatings and other Advanced Hydrophilic Coatings available from SurModics, Inc., Eden Prairie, MN. DSM Medical Coatings (available from Koninklijke DSM NV, Heerlen, the Netherlands) and other hydrophilic coatings (e.g., PTFE, polyethylene, polyvinylidene fluoride) are also suitable for use with the sheath 100. Such a hydrophilic coating may also be included on the inner surface of the inner layer 102 to reduce friction between the sheath and the delivery system, thereby improving ease of use and safety. In some embodiments, a hydrophobic coating, such as perylene, may be used on the outer surface of the outer layer 108 or on the inner surface of the inner layer 102 to reduce friction.

[0065] In some embodiments, the second layer 104 can be a braided layer. FIGS. 5A and 5B show the sheath 100 with the outer layer 108 removed to expose the elastic layer 106. Referring to FIGS. 5A and 5B, the braided layer 104 can comprise multiple members or filaments 110 (e.g., metallic or synthetic wires or fibers) braided together. The braided layer 104 can have any desired number of filaments 110, which can be oriented and braided together along any suitable number of axes. For example, referring to FIG. 5B, the filaments 110 can comprise 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 as 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 some embodiments, the angle θ can be between 5° and 70°, between 10° and 60°, between 10° and 50°, or between 10° and 45°. In the illustrated embodiment, the angle θ is 45°. In other embodiments, the filaments 110 can be oriented along three axes and braided as a triaxial braid, or oriented along any number of axes and braided in any suitable braid pattern.

[0066] The braided layer 104 may extend along substantially the entire length L of the sheath 100, or alternatively, may extend along only a portion of the sheath's length. In certain embodiments, the filament 110 may be a wire made from any of a variety of polymers or polymer composites, such as metal (e.g., nitinol, stainless steel, etc.), or carbon fiber. In some embodiments, the filament 110 may be round and have a diameter between 0.01 mm and 0.5 mm, between 0.03 mm and 0.4 mm, or between 0.05 mm and 0.25 mm. In other embodiments, the filament 110 may have a flattened cross-section with dimensions between 0.01 mm x 0.01 mm x 0.5 mm x 0.5 mm, or between 0.05 mm x 0.05 mm x 0.25 mm x 0.25 mm. In one embodiment, a filament 110 with a flattened cross-section may have dimensions of 0.1 mm x 0.2 mm. However, other shapes and sizes may also be suitable for some embodiments. When braided wire is used, the braid density can vary. Some embodiments have a braid density of 10 picks / inch to 80 picks / inch and can include 8 wires, 16 wires, or up to 52 wires in various braid patterns. In other embodiments, the second layer 104 can be laser cut from a tube, or laser cut, pressed, stamped, etc. from sheet stock and wound into a tubular configuration. Layer 104 can also be woven or knitted as desired.

[0067] The third layer 106 can be an elastic layer (also referred to as an elastic material layer). In some embodiments, the elastic layer 106 can be configured to apply a radial force (e.g., toward the central axis 114 of the sheath) to the underlying layers 102 and 104 when passage of a delivery device through the sheath causes the sheath to expand beyond its original diameter. In other words, the elastic layer 106 can be configured to oppose the expansion of the sheath by applying a surrounding pressure to the layers of the sheath below the elastic layer 106. This radially inward force is sufficient to cause the sheath to radially contract back to its unexpanded state after the delivery device has been passed through the sheath.

[0068] In the illustrated embodiment, the elastic layer 106 may comprise one or more members configured as strands, ribbons, or bands 116 spirally wound around the braided layer 104. For example, in the illustrated embodiment, the elastic layer 106 comprises two elastic bands 116A and 116B spirally wound in opposite directions around the braided layer, although the elastic layers may comprise any number of bands depending on the desired characteristics. The elastic bands 116A and 116B may be made from any of a variety of natural or synthetic elastomers, including, for example, silicone rubber, natural rubber, any of a variety of thermoplastic elastomers, polyurethanes such as polyurethane-siloxane copolymers, urethanes, plasticized polyvinyl chloride (PVC), styrene block copolymers, polyolefin elastomers, and the like. In some embodiments, the elastic layer may comprise an elastomeric material having a modulus of elasticity of 200 MPa or less. In some embodiments, the elastic layer 106 may comprise a material exhibiting an elongation at break of 200% or more or an elongation at break of 400% or more. The elastic layer 106 can also take other forms, such as a tubular layer comprising an elastic material, a mesh, or a shrinkable polymer layer, such as a heat-shrink tubing layer. Alternatively, or in addition to the elastic layer 106, the sheath 100 can include an elastomeric layer or heat-shrink tubing layer around the outer layer 108. Examples of such elastomeric layers are disclosed in U.S. Patent Application Publication Nos. 2014 / 0379067, 2016 / 0296730, and 2018 / 0008407, which are incorporated herein by reference. In other embodiments, the elastic layer 106 can be positioned radially outward of the polymer layer 108.

[0069] In some embodiments, one or both of the inner layer 102 and / or the outer layer 108 can be configured to resist axial elongation of the sheath 100 during sheath expansion. More specifically, one or both of the inner layer 102 and / or the outer layer 108 can resist elongation against longitudinal forces caused by friction between the prosthetic device and the inner surface of the sheath, such that the length L remains substantially constant during sheath expansion and contraction. When used herein with reference to the sheath length L, the term "substantially constant" means that the sheath length L increases by no more than 1%, no more than 5%, no more than 10%, no more than 15%, or no more than 20%. Meanwhile, referring to FIG. 5B , the filaments 110A and 110B of the braided layers can be allowed to move angularly relative to one another such that the angle θ changes during sheath expansion and contraction. This, in combination with the longitudinal folds 126 in layers 102 and 108, may allow for expansion of the lumen 112 of the sheath as the prosthetic device is advanced through the sheath.

[0070] For example, in some embodiments, the inner layer 102 and the outer layer 108 may be heat-bonded during the manufacturing process such that the braided layer 104 and the elastic layer 106 are encapsulated between the layers 102 and 108. More specifically, in some embodiments, the inner layer 102 and the outer layer 108 may be bonded to one another through the spaces between the filaments 110 and / or the elastic bands 116 of the braided layer 104. The layers 102 and 108 may also be bonded or glued together at the proximal and / or distal ends of the sheath. In some embodiments, the layers 102 and 108 are not attached to the filaments 110. This allows the filaments 110 to move angularly relative to one another and relative to the layers 102 and 108, which may increase or decrease the diameter of the braided layer 104 and, therefore, the diameter of the sheath. As the angle θ between the filaments 110A and 110B changes, the length of the braided layer 104 may also change. For example, as angle θ increases, braided layer 104 shortens, and as angle θ decreases, braided layer 104 is allowed to stretch to the extent permitted by the area where layers 102 and 108 are joined. However, because braided layer 104 is not bonded to layers 102 and 108, changes in the length of the braided layer with changes in angle θ between filaments 110A and 110B do not result in a significant change in sheath length L.

[0071] 6 illustrates the radial expansion of the sheath 100 as the prosthetic device 12 passes through the sheath in the direction of the arrow 132 (e.g., distally). As the prosthetic device 12 is advanced through the sheath 100, the sheath may elastically expand to a second diameter D2 corresponding to the size or diameter of the prosthetic device. As the prosthetic device 12 is advanced through the sheath 100, the prosthetic device may apply a longitudinal force to the sheath in the direction of movement due to frictional contact between the prosthetic device and the inner surface of the sheath. However, as described above, the inner layer 102 and / or the outer layer 108 may resist axial elongation so that the sheath length L remains constant or substantially constant. This may reduce or prevent elongation of the braided layer 104 and, therefore, compression of the lumen 112.

[0072] Meanwhile, the angle θ between filaments 110A and 110B may increase as the sheath expands to a second diameter D2 to accommodate the prosthetic valve. This may cause the braided layer 104 to shorten. However, because filament 110 is not engaged or bonded to layers 102 or 108, the shortening of braided layer 104 with the increase in angle θ does not affect the overall length L of the sheath. Furthermore, the longitudinally extending folds 126 formed in layers 102 and 108 allow layers 102 and 108 to expand to the second diameter D2 without tearing, instead of becoming relatively thin and relatively inelastic. In this manner, sheath 100 may elastically expand from its original diameter D1 to a second diameter D2 greater than diameter D1 without stretching or compressing as the prosthetic device is advanced through the sheath. Therefore, the force required to push the prosthetic implant through the sheath is significantly reduced.

[0073] Furthermore, the radial force applied by the elastic layer 106 can localize the radial expansion of the sheath 100 to the specific portion of the sheath occupied by the prosthetic device. For example, referring to FIG. 6 , as the prosthetic device 12 is moved distally through the sheath, the portion of the sheath immediately proximal to the prosthetic device 12 can radially contract back to the initial diameter D1 under the influence of the elastic layer 106. Additionally, the layers 102 and 108 can buckle and reform the ridges 126 and grooves 128 as the sheath circumference decreases, allowing for a reduction in the size of the sheath required to introduce a given size prosthetic device. Furthermore, the temporary, localized nature of the expansion can reduce trauma to the vessel and surrounding tissue into which the sheath is inserted because the portion of the sheath occupied by the prosthetic device expands beyond the sheath's original diameter, and the sheath contracts back to its initial diameter after the device has passed. This limits the amount of tissue that must be stretched for the introduction of a prosthetic device and the amount of time that a given portion of the vessel must be dilated.

[0074] In addition to the above advantages, the expandable sheath embodiments described herein may provide surprising performance advantages over known introducer sheaths. For example, a sheath configured as described herein can be used to deliver prosthetic devices having diameters that are two, two and a half, or even three times larger than the sheath's native outer diameter. For example, in one embodiment, a crimped prosthetic heart valve having a diameter of 7.2 mm was successfully advanced through a sheath configured as described above and having a native outer diameter of 3.7 mm. As the prosthetic valve was advanced through the sheath, the outer diameter of the portion of the sheath occupied by the prosthetic valve expanded to 8 mm. In other words, a prosthetic device having a diameter more than twice the sheath's outer diameter could be advanced through the sheath, while the sheath's outer diameter elastically expanded by 216%. In another example, a sheath having an initial or native outer diameter of 4.5 mm to 5 mm can be configured to expand to an outer diameter of 8 mm to 9 mm.

[0075] In alternative embodiments, sheath 100 may optionally include layer 102 without layer 108, or layer 108 without layer 102, depending on the particular characteristics desired.

[0076] 10A-10D illustrate another embodiment of braided layer 104 configured to buckle filaments 110. For example, FIG. 10A illustrates unit cells 134 of braided layer 104 in a configuration corresponding to the braided layer in a fully expanded state. For example, the expanded state illustrated in FIG. 10A may correspond to the diameter of the braided layer while sheath 100 is in an initial configuration before the sheath radially contracts to diameter D2 described above and / or to its functional design diameter D1 as further described below with reference to FIG. 7. The angle θ between filaments 110A and 110B can be, for example, 40°, and unit cells 134 extend along the x-direction by a length L x (Note the Cartesian coordinate axes shown.) Figure 10B shows a portion of braided layer 104 comprising an array of unit cells 134 in an expanded state.

[0077] In the illustrated embodiment, the braided layer 104 is disposed between the polymer layers 102 and 108, as described above. For example, the polymer layers 102 and 108 may be bonded or laminated to each other at the ends of the sheath 100 and / or between the filaments 110 within the open spaces 136 defined by the unit cells 134. Thus, with reference to FIGS. 10C and 10D , as the sheath 100 is radially contracted to its functional diameter D1, the diameter of the braided layer 104 may decrease due to a decrease in the angle θ. However, the bonded polymer layers 102 and 108 may inhibit or prevent the braided layer 104 from elongating due to radial contraction. This allows the filaments 110 to elastically buckle in the axial direction, as shown in FIGS. 10C and 10D . The degree of buckling is determined by the length L of the unit cells 134. x The sheath may be configured such that the sheath length is the same or substantially the same between the contracted and fully expanded diameters of the sheath. This means that the overall length of the braided layer 104 may remain constant or substantially constant between the original diameter D1 of the sheath and the expanded diameter D2. As the sheath expands from its initial diameter D1 during passage of a medical device, the filaments 110 may unbuckle and straighten, allowing the sheath to radially expand. Once the medical device has passed through the sheath, the braided layer 104 may be forced back to the original diameter D1 by the elastic layer 106, and the filaments 110 may again elastically buckle. Using the configuration of Figures 10A-10C, it may be possible to accommodate prosthetic valves having diameters two, two and a half, or even three times larger than the original diameter D1 of the sheath.

[0078] Turning now to a method of fabricating an expandable sheath, FIG. 7 shows layers 102-108 of an expandable sheath 100 disposed on a cylindrical mandrel 118, according to one embodiment. In some embodiments, the mandrel 118 can have a diameter D3 that is larger than the desired native outer diameter D1 of the finished sheath. For example, in some embodiments, the ratio of mandrel diameter D3 to sheath outer diameter D1 can be 1.5:1, 2:1, 2.5:1, 3:1, or greater. In some embodiments, the mandrel diameter D3 can be equal to the expanded diameter D2 of the sheath. In other words, the mandrel diameter D3 can be the same as or approximately the same as the desired expanded diameter D2 of the sheath when a prosthetic device is advanced through the sheath. Thus, in some embodiments, the ratio of the expanded outer diameter D2 of the sheath when expanded to the contracted outer diameter D1 of the sheath when unexpanded can be 1.5:1, 2:1, 2.5:1, 3:1, or greater.

[0079] 7, the expandable sheath 100 may be fabricated by wrapping or placing the ePTFE layer 120 around a mandrel 118, followed by the first polymer layer 102. In some embodiments, the ePTFE layer may aid in removal of the sheath 100 from the mandrel 118 upon completion of the assembly process. The first polymer layer 102 may be in the form of a prefabricated sheet that is applied by wrapping around the mandrel 118, or may be applied to the mandrel by dip coating, electrospinning, or the like. The braided layer 104 may be placed around the first layer 102, followed by the elastic layer 106. In embodiments where the elastic layer 106 includes one or more elastic bands 116, the bands 116 may be helically wrapped around the braided layer 104. In other embodiments, the elastic layer 106 may be dip coated, electrospun, or the like. An outer polymer layer 108 may then be wrapped or applied around the elastic layer 106, followed by another ePTFE layer 122 and one or more heat shrink tubing or tape layers 124.

[0080] In certain embodiments, the elastic band 116 may be applied to the braided layer 104 in a stretched, tensioned, or elongated state. For example, in some embodiments, the band 116 may be applied to the braided layer 104 stretched to twice its original relaxed length. This allows the completed sheath to radially contract under the influence of the elastic layer upon removal from the mandrel, which may then correspondingly relax the elastic layer, as described below. In other embodiments, the layer 102 and braided layer 104 can be removed from the mandrel, the elastic layer 106 applied in a relaxed or moderately stretched state, and then the assembly placed back onto the mandrel so that the elastic layer is radially expanded and stretched into tension before applying the outer layer 108.

[0081] The assembly may then be heated to a temperature high enough to cause the heat shrink layer 124 to shrink and compress the layers 102-108 together. In some embodiments, the assembly may be heated to a temperature high enough to cause the polymeric inner layer 102 and polymeric outer layer 108 to become soft and sticky, bond to each other in the open space between the braided layer 104 and the elastic layer 106, and encapsulate the braided layer and the elastic layer. In other embodiments, the inner layer 102 and outer layer 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 embodiment, the assembly may be heated to 150°C for 20-30 minutes.

[0082] After heating, the sheath 100 may be removed from the mandrel 118, and the heat shrink tubing 124 and ePTFE layers 120 and 122 may be removed. Upon removal from the mandrel 118, the sheath 100 may at least partially radially contract to its original design diameter D1 under the influence of the elastic layer 106. In some embodiments, the sheath may optionally be radially contracted to its design diameter with the assistance of a crimping mechanism. The accompanying reduction in circumference may cause the filaments 110, along with the inner and outer layers 102, 108, to buckle, forming longitudinally extending folds 126, as shown in FIGS. 10C and 10D .

[0083] In some embodiments, a PTFE layer may be disposed between ePTFE layer 120 and inner layer 102 and / or between outer layer 108 and ePTFE layer 122 to facilitate separation of inner and outer polymer layers 102, 108 from ePTFE layers 120 and 122, respectively. In further embodiments, one of inner and outer layers 102, 108 may be omitted, as described above.

[0084] FIG. 8 illustrates another embodiment of an expandable sheath 100 including one or more members configured as threads or cords 130 extending longitudinally along the sheath and attached to the braided layer 104. While only one cord 130 is illustrated in FIG. 8, in practice, the sheath may include two, four, six, etc. cords arranged along the circumference of the sheath at equal angular intervals. These cords 130 may be sutured to the exterior of the braided layer 104, although other configurations and attachment methods are possible. By being attached to the braided layer 104, the cords 130 may be configured to prevent axial elongation of the braided layer 104 as the prosthetic device is passed through the sheath. The cords 130 may be used in combination with the elastic layer 106 or separately. The cords 130 may also be used in combination with one or both of the inner layer 102 and / or outer layer 108 depending on the specific characteristics desired. The cord 130 may also be disposed on the interior of the braided layer 104 (eg, between the inner layer 102 and the braided layer 104).

[0085] Expandable sheath 100 can also be fabricated in other ways. For example, FIG. 9 shows apparatus 200 including a containment vessel 202 and a heating system, shown generally at 214. Apparatus 200 is particularly suited for forming devices (medical or non-medical) composed of two or more layers of material. A device formed with apparatus 200 can be formed from two or more coaxial layers of material, such as sheath 100, or from a shaft for a catheter. Alternatively, a device formed with apparatus 200 can be formed from two or more non-coaxial layers, such as two or more layers stacked on top of each other.

[0086] The containment vessel 202 may define an interior volume or chamber 204. In the illustrated embodiment, the vessel 202 may be a metal tube with a closed end 206 and an open end 208. The vessel 202 may be at least partially filled with a thermally expansive material 210 having a relatively high coefficient of thermal expansion. In a particular embodiment, the thermally expansive material 210 has a coefficient of thermal expansion of 2.4×10 -4 Exemplary thermally expansible materials include elastomers such as silicone materials. Silicone materials have a thermal expansion coefficient of 5.9×10 -4 / ℃~7.9×10 -4 / °C.

[0087] A mandrel similar to mandrel 118 of FIG. 7 and with a desired combination of sheath material layers disposed therearound can be inserted into thermally expansive material 210. Alternatively, mandrel 118 can be inserted into chamber 204, and the remaining volume of the chamber filled with thermally expansive material 210 such that the mandrel is surrounded by this material. Mandrel 118 is shown schematically for illustrative purposes. Thus, mandrel 118 can be cylindrical, as shown in FIG. 7. Similarly, the inner surface of material 210 and the inner surface of vessel 202 can have a cylindrical shape corresponding to the shape of mandrel 118 and the final shape of sheath 100. To facilitate placement of the cylindrical or circular mandrel 118, the container 202 can include two sections connected to each other by a hinge that allows the two sections to move between an open configuration for placing the mandrel inside the container and a closed configuration that extends 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 located on the closed side of the container (the left side of the container in Figure 9).

[0088] The open end 208 of the container 202 may be closed with a cap 212. The container 202 may then be heated by a heating system 214. The heating by the heating system 214 may cause the material 210 to expand within the chamber 204 and apply radial pressure to the layers of material on the mandrel 118. This combination of heat and pressure may cause the layers on the mandrel 118 to bond or adhere to one another to form a sheath. In some embodiments, the apparatus 200 may be used to apply radial pressures of 100 MPa or more to the mandrel 118. The amount of radial pressure applied to the mandrel may be controlled by, for example, the type, quality, and thermal expansion rate of the material 210 selected, the thickness of the material 210 surrounding the mandrel 118, the temperature to which the material 210 is heated, etc.

[0089] In some embodiments, heating system 214 can be an oven in which vessel 202 is placed. In some embodiments, the heating system can include one or more heating elements positioned around vessel 202. In some embodiments, vessel 202 can be an electrical resistance heating element or an induction heating element controlled by heating system 214. In some embodiments, a heating element can be embedded within thermally expandable material 210. In some embodiments, material 210 can be configured as a heating element, such as by adding a conductive filler material, such as carbon fiber or metal particles.

[0090] Apparatus 200 may offer several advantages over known sheath manufacturing methods, including highly controllable and uniform application of radial force to mandrel 118 along its length and high repeatability. Apparatus 200 may also facilitate fast and precise heating of 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 applied radial force may also be varied along the length of the mandrel, such as by varying the type or thickness of the surrounding material 210. In some embodiments, multiple containers 202 may be processed within a single fixture, and / or multiple sheaths may be fabricated within a single container 202. Apparatus 200 may also be used to fabricate other devices, such as shafts or catheters.

[0091] In one specific method, sheath 100 can be formed by placing layers 102, 104, 106, 108 on a mandrel 118 and placing the mandrel with these layers inside a container 202, with a thermally expandable material 210 surrounding the outermost layer 108. If desired, 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 removal of the completed sheath from mandrel 118 and material 210 (shown in FIG. 7). The assembly is then heated with a heating system 214 to reflow layers 102, 108. After subsequent cooling, layers 102, 108 become at least partially bonded to one another and at least partially encapsulate layers 104, 106.

[0092] FIG. 11 illustrates another embodiment in which the expandable sheath 100 is configured to receive an apparatus configured as a plain introducer or vessel dilator 300. In certain embodiments, the introducer device 90 may include the vessel dilator 300. Referring to FIG. 12, the vessel dilator 300 may include a shaft member 302 having a tapered dilator member configured as a nosecone 304 located at a distal end portion of the shaft member 302. The vessel dilator 300 may further include a capsule or retention member 306 extending proximally from a proximal end portion 308 of the nosecone 304, with a circumferential space 310 defined between an outer surface of the shaft member 302 and an inner surface of the retention member 306. In some embodiments, the retention member 306 may be configured as a thin polymer layer or sheet, as described further below.

[0093] 11 and 13, the first or distal end portion 140 of the sheath 100 can be received within the space 310 such that the sheath engages the nosecone 304 and / or the retention member 306 extends beyond the distal end portion 140 of the sheath. In use, the combined or assembled vessel dilator 300 and sheath 100 can be inserted into a blood vessel through an incision. The tapered cone shape of the nosecone 304 can assist in gradual dilation of the vessel and access site while minimizing trauma to the vessel and surrounding tissue. Once the assembly is inserted to a desired depth, the vessel dilator 300 can be advanced further (e.g., distally) into the vessel while the sheath 100 is held steady, as shown in FIG. 14.

[0094] 15, the vessel dilator 300 may be advanced distally through the sheath 100 until the retention member 306 is removed from over the distal end portion 140 of the sheath 100. In some embodiments, the sheath's spirally wound elastic layer 106 may terminate proximal to the sheath's distal end 142. Thus, once the sheath's distal end portion 140 is uncovered, this distal end portion (which may be heat set) may be allowed to flare or expand, increasing the diameter of the opening at the distal end 142 from a first diameter D1 (FIG. 13) to a second, larger diameter D2 (FIG. 15). The vessel dilator 300 may then be pulled back through the sheath 100, as shown in FIGS. 16-18, leaving the sheath 100 in place within the blood vessel.

[0095] The vessel dilator 300 can include various active and / or passive mechanisms for engaging and retaining it to the sheath 100. For example, in some embodiments, the retention member 306 can include a polymer heat shrink layer that can be shrunk around the distal end portion of the sheath 100. In the embodiment shown in FIG. 1 , the retention member can include a resilient member configured to compress the distal end portion 140 of the sheath 100. In still other embodiments, the retention member 306 and sheath 100 can be glued or welded (e.g., heat-bonded) together in a manner such that application of a selected amount of force can break the adhesive bond between the retention member 306 and the sheath 100, allowing withdrawal of the vessel dilator. In some embodiments, the end portions of the braided layer 104 can be heat-set to flare or expand radially inward or outward, thereby applying pressure against corresponding portions of the vessel dilator 300.

[0096] 19, the assembly may include a mechanically actuated retention mechanism, such as a shaft 312 disposed between the dilator shaft member 302 and the sheath 100. In some embodiments, the shaft 312 may removably couple the vascular dilator 300 to the sheath 100 and may be actuated from outside the body (i.e., may be manually deactivated).

[0097] 20 and 21 , in some embodiments, the shaft member 302 can include one or more balloons 314 circumferentially arranged along its outer surface and configured to engage the sheath 100 when inflated. The balloons 314 can be selectively deflated to remove the sheath 100 and withdraw the vessel dilator. For example, when inflated, the balloons compress 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 vessel dilator. When the balloons are deflated, the vessel dilator can be more easily moved relative to the sheath 100.

[0098] In another embodiment, an expandable sheath configured as described above may further include a shrinkable polymer outer covering, such as the heat shrink tubing layer 400 shown in FIG. 22. The heat shrink 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 shrink tubing layer 400 may also constrain the sheath to a selected initial small outer diameter. In some embodiments, the heat shrink tubing layer 400 may extend completely along the length of the sheath 100 and be attached to the sheath handle by mechanical fastening means such as clamps, nuts, adhesives, heat welding, laser welding, or elastic clamps. In some embodiments, the sheath is press-fit into the heat shrink tubing layer during manufacturing.

[0099] In some embodiments, the heat shrink tubing layer 400 can extend distally beyond the sheath distal end portion 140 as a distal flaring portion 408, shown in FIG. 22 . A vessel dilator can be inserted through the sheath lumen 112 and over the distal edge of the flaring portion 408. The flaring portion 408 conforms closely to the inserted vessel dilator to facilitate insertion of the dilator and sheath combination by providing a smooth transition between the diameter of the dilator and the diameter of the sheath. When the vessel dilator is removed, the flaring portion 408 remains within the vessel as part of the sheath 100. The heat shrink tubing layer 400 provides the added benefit of shrinking the overall outer diameter of the sheath along the longitudinal axis. However, it will be appreciated that some embodiments, such as the sheath 301 shown in FIG. 42, may include a heat shrink tubing layer 401 that terminates at the distal end of the sheath 301 or, in some embodiments, does not extend all the way to the distal end of the sheath. In embodiments without a distal flaring portion, the heat shrink tubing layer functions primarily as an outer shrink layer and is configured to maintain the sheath in a compressed configuration. Such embodiments do not provide a flap-like flaring portion at the distal end of the sheath when the dilator is retracted.

[0100] In some embodiments, the heat shrink tubing layer can be configured to split open upon advancement of a delivery device, such as delivery device 10, through the sheath. For example, in some embodiments, the heat shrink tubing layer can include one or more longitudinally extending openings, slits, or frangible elongated score lines 406, such as those shown in FIG. 22, configured to initiate splitting of the layer at selected locations. As delivery device 10 is advanced through the sheath, the heat shrink tubing layer 400 continues to split open, allowing the sheath to expand as described above with less force. In some embodiments, the sheath need not include the elastic layer 106, such that the sheath automatically expands from its initial reduced diameter when the heat shrink tubing layer splits open. The heat shrink tubing layer 400 can include polyethylene or other suitable material.

[0101] FIG. 23 illustrates a heat-shrink tubing layer 400 that may be disposed around an expandable sheath described herein, according to one embodiment. In some embodiments, the heat-shrink tubing layer 400 may include multiple cuts or score lines 402 that extend axially along the tubing layer 400 and terminate in distal stress relief features configured as circular openings 404. It is contemplated that the distal stress relief features may also be configured as any other regular or irregular curved shapes, including, for example, elliptical and / or oval openings. Various shapes of distal stress relief features along and around the heat-shrink tubing layer 400 are also contemplated. As the delivery device 10 is advanced through the sheath, the heat-shrink tubing layer 400 may split open along the score lines 402, and the distally positioned openings 404 may inhibit further tearing or cracking of the tubing layer along the respective score lines. As such, the heat shrink tubing layer 400 remains attached to the sheath along the length of the sheath. In the illustrated embodiment, the score lines and associated openings 404 are longitudinally and circumferentially offset, or staggered, from one another. Thus, when the sheath expands, the score lines 402 may form rhomboid structures. The score lines can also extend in other directions, such as in a spiral or zigzag pattern, around the longitudinal axis of the sheath.

[0102] In other embodiments, cracking or splitting of the heat shrink tubing layer may be induced in a variety of other ways, such as by forming a weakened area on the tubing surface, for example by applying a chemical solvent, cutting, scoring, or ablating the surface with a tool or laser, and / or by reducing the wall thickness or forming a crack in the tubing wall (e.g., by femtosecond laser ablation, etc.).

[0103] In some embodiments, the heat shrink tubing layer may be attached to the body of the sheath by adhesive, welding, or any suitable fastening means. FIG. 29 shows a perspective view of a sheath embodiment including an inner layer 802, a braided layer 804, an elastic layer 806, an outer layer 808, and a heat shrink tubing layer 809. As described below with reference to FIG. 36, some embodiments may not include the elastomeric layer 806. The heat shrink tubing layer 809 includes a split 811 and perforations 813 extending along the heat shrink tubing layer 809. The heat shrink tubing layer 809 is bonded to the outer layer 808 at a bonded seam 815. For example, in some embodiments, the heat shrink tubing layer 809 can be bonded at the seam 815 by welding, thermal bonding, chemical bonding, ultrasonic bonding, and / or the use of an adhesive (including, but not limited to, a thermal adhesive such as an LDPE fiber thermal adhesive). The outer layer 808 can be bonded to the heat shrink tubing layer 809 either axially or helically along the sheath at seam 815. Figure 30 shows an embodiment of the same sheath in which the heat shrink tubing layer 809 has split open at the distal end of the sheath.

[0104] Figure 31 shows the sheath with the heat shrink tubing layer 809 before a delivery system is passed through it. Figure 32 shows a perspective view of the sheath, with the heat shrink tubing layer 809 partially split open and released by the delivery system passing through it, expanding the diameter of the sheath. The heat shrink tubing layer 809 is held in place by an adhesive seam 815. Attaching the heat shrink tubing layer 809 to the sheath in this manner can help maintain the heat shrink tubing layer 809 attached to the sheath after the layer splits and the sheath expands, as shown in Figure 33, where a delivery system 817 has been passed completely through the sheath, splitting the heat shrink tubing layer 809 along the entire length of the sheath.

[0105] In another embodiment, the expandable sheath can have a distal end or tip portion comprising an elastic thermoplastic material (e.g., Pebax), which can be configured to provide an interference fit or interference with a corresponding portion of the vascular dilator 300. In some embodiments, the outer layer of the sheath can include a polyamide (e.g., nylon) to allow welding of the distal end portion to the body of the sheath. In some embodiments, the distal end portion can include intentionally weakened portions, scores, slits, etc., to allow the distal end portion to split open when a delivery device is advanced therethrough.

[0106] In another embodiment, the entire sheath can have an elastomeric outer covering extending longitudinally from the handle to the distal end portion 140 of the sheath, optionally extending outward to form a flaring portion similar to flaring portion 408 shown in FIG. 22. This elastomeric flaring portion conforms closely to the vasodilator but remains part of the sheath when the vasodilator is removed. As the delivery system passes through, the elastomeric flaring portion expands and then contracts to allow the delivery system to pass through. The elastomeric flaring portion or the entire elastomeric outer covering can include intentionally weakened portions, scores, slits, etc., to allow the distal end portion to split open as a delivery device is advanced therethrough.

[0107] FIG. 24 illustrates an end portion (e.g., a distal end portion) of another embodiment of the braided layer 104 in which portions 150 of the braided filaments 110 are bent to form loops 152, which loop or extend back along the sheath in reverse. The filaments 110 may be arranged such that the loops 152 of various filaments 110 are axially offset from one another in the braid. Moving toward the distal end of the braided layer 104 (to the right in the drawing), the number of braided filaments 110 may decrease. For example, the filament designated 5 may form a loop 152 first, followed by the filaments designated 4, 3, and 2, with filament 1 forming the most distal loop 152. Thus, the number of filaments 110 in the braid decreases distally, which may increase the radial flexibility of the braided layer 104.

[0108] In another embodiment, the distal end portion of the expandable sheath can include a polymer such as Dyneema®, which can be tapered relative to the diameter of the vascular dilator 300. A weakened portion, such as a dashed cut, score line, or the like, can be applied to the distal end portion to split open and / or expand in a repeatable manner.

[0109] Crimping of the expandable sheath embodiments described herein can be performed in a variety of ways, as described above. In further embodiments, the sheath can be crimped multiple times longitudinally along a longer sheath using a conventional short crimper. In other embodiments, the sheath can be shrunk to a specified crimped diameter in one or a series of stages in which the sheath is enclosed in heat shrink tubing and shrunk under heat. For example, a first heat shrink tube can be applied to the outer surface of the sheath, the sheath can be compressed to an intermediate diameter by shrinking (heat) the first heat shrink tube, the first heat shrink tube can be removed, a second heat shrink tube can be applied to the outer surface of the sheath, the second heat shrink tube can be compressed to a diameter smaller than the intermediate diameter by heat, and the second heat shrink tube can be removed. This can be continued as many times as necessary to achieve the desired crimped sheath diameter.

[0110] Crimping of the expandable sheath embodiments described herein can be accomplished in a variety of ways, as discussed above. A roller-based crimping mechanism 602, such as that shown in FIGS. 25A-25C, can 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 end surface 604 and the second end surface 605. A plurality of disk-shaped rollers 606a-f are radially arranged about the longitudinal axis aa, with each of the disk-shaped rollers 606a-f positioned at least partially between the first and second surfaces of the crimping mechanism 602. While six rollers are shown in the illustrated embodiment, the number of rollers may vary. Each disk-shaped roller 606 is attached to a larger crimping mechanism by a connector 608. 25B shows a side cross section of an individual disc-shaped roller 606 and connector 608, and FIG. 25C shows a top view of an individual disc-shaped roller 606 and connector 608. As shown in FIG. 25C, an individual 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 first side surface 612 and the second side surface 614. The plurality of disc-shaped rollers 606a-f are radially arranged about 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 central axis aa of the crimping mechanism 602. The circular edge 610 of the disc-shaped rollers partially defines a passageway extending axially through the crimping mechanism 602 along the longitudinal axis aa.

[0111] Each disc-shaped roller 606 is held in place in a radial arrangement by connectors 608 that are attached to the crimping mechanism 602 by one or more fasteners 619 such that the position of each of the connectors is fixed relative to the first end surface of the crimping mechanism 602. In the illustrated embodiment, the fasteners 619 are positioned radially outward of the disc-shaped roller 606 adjacent to an outer portion of the crimping mechanism 602. In the illustrated embodiment, two fasteners 619 are used to position each connector 608, although the number of fasteners 619 can be varied. As shown in FIGS. 25B and 25C , the connectors 608 have a first arm 616 and a second arm 618. The first arm 616 and the second arm 618 extend on the disc-shaped roller 606 from a radially outer portion of the circular edge 610 to a central portion of the disc-shaped roller 606. A bolt 620 extends through the first arm 616 and the second arm 618 and through a central lumen of the disc-shaped roller 606, which central lumen passes along a central axis cc from a center point of the front surface 612 to a center point of the rear surface 614 of the disc-shaped roller 606. The bolt 620 is positioned free within the lumen with substantial clearance / space to allow the disc-shaped roller 606 to rotate about the central axis cc.

[0112] During use, an elongate sheath is advanced from a first side 604 of the crimping mechanism 602 through the axial passage between the rollers to a second side 605 of the crimping mechanism 602. Pressure from the circular edge 610 of the disk-shaped roller 606 causes the disk-shaped roller 606 to roll along the outer surface of the elongate sheath, reducing the diameter of the sheath to the crimped diameter.

[0113] 26 illustrates one embodiment of a crimping device 700 designed to facilitate crimping of an elongated structure, such as a sheath. The crimping device includes an elongated base 704, an elongated mandrel 706 positioned above the elongated base 704, and a retention mechanism 708 attached to the elongated base 704. The retention mechanism 708 supports the mandrel 706 in an elevated position above the base 704. The retention mechanism includes a first end piece 710 that includes a crimping mechanism 702. The mandrel 706 includes a conical end portion 712 that is nested within a first tapered portion 713 of a constricted lumen 714 of the first end piece 710. The conical end portion 712 of the mandrel 706 is positioned loosely within the stenotic lumen 714, with sufficient space or clearance between the conical end portion 712 and the lumen 714 to allow passage of an elongated sheath over the conical end portion 712 of the mandrel 706 and through the stenotic lumen 714. During use, the conical end portion 712 helps prevent circumferential buckling of the sheath during crimping. In some embodiments, the mandrel 706 can further include a cylindrical end portion 724 that extends outwardly from the conical end portion 712 and defines an end 726 of the mandrel 706.

[0114] A first tapered section 713 of the constricted lumen 714 opens toward the second end piece 711 of the retention feature 708 such that the widest side of the tapered section is on the inner surface 722 of the first end piece 710. In the illustrated embodiment, the first tapered section 713 narrows to a narrow end 715 that connects to a narrow cylindrical section 716 of the constricted lumen 714. In this embodiment, the narrow cylindrical section 716 defines the smallest width diameter of the constricted lumen 714. The cylindrical end portion 724 of the mandrel 706 nests loosely within the narrow cylindrical section 716 of the constricted lumen 714, and there may be sufficient space or clearance between the cylindrical end portion 724 and the narrow cylindrical section 716 of the lumen to allow passage of an elongate sheath therethrough. The elongated nature of narrow cylindrical portion 716 may facilitate smoothing of the crimped sheath after the sheath has passed over mandrel conical end portion 712. However, this length of cylindrical portion 716 of constricted lumen 714 is not intended to limit the invention, and in some embodiments, crimping mechanism 702 may comprise only first tapered portion 713 of constricted lumen 714, yet still be effective in crimping an elongated sheath.

[0115] 26 , a second tapered section 718 of the constricted lumen 714 diverges from the narrow cylindrical section 716, with the widest side of the taper located on the outer surface 720 of the first end piece 710. A narrow end 719 of the second tapered section 718 connects to the narrow cylindrical section 716 of the constricted lumen 714 inside the crimp mechanism 702. In some embodiments, the second tapered section 718 of the constricted lumen 714 may not be present.

[0116] The retention mechanism 708 further includes a second end piece 711 positioned on the elongated base 704 opposite the first end piece 710. The second end piece 711 is movable relative to the elongated base 704, allowing the distance between the first end piece 710 and the second end piece 711 to be adjustable, thereby enabling mandrels of various sizes to be supported. In some embodiments, the elongated base 704 may include one or more elongated sliding tracks 728. The second end piece 711 may be slidably engaged to the sliding tracks 728 by at least one reversible fastener 730, such as, but not limited to, a bolt, extending through or in the second end piece 711 and the elongated sliding track 728. To move the second end piece 711, a 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.

[0117] In use, a sheath at its uncrimped diameter can be placed over the elongated mandrel 706 of the crimping device 700 shown in FIG. 26 such that the inner surface of the entire length of the uncrimped sheath is supported by the mandrel. The uncrimped sheath is then advanced over the conical end portion 712 and through the constricted lumen 714 of the crimping mechanism 702. The uncrimped sheath is crimped to the smaller crimped diameter by pressure from the inner surface of the constricted lumen 714. In some embodiments, the sheath is advanced through both the first tapered portion 713 and the cylindrical portion 716 of the constricted lumen 714 before exiting the crimping mechanism 702. In some embodiments, the sheath is advanced through the first tapered portion 713, the cylindrical portion 716, and the second tapered portion 718 of the constricted lumen 714 before exiting the crimping mechanism 702.

[0118] 25A can be positioned within a larger crimping device, such as the crimping device 700 shown in FIG. 26. For example, the crimping mechanism 602 can be positioned within the first end piece 710 of the crimping device 700 in place of or in combination with the crimping mechanism 702. For example, the rolling crimping mechanism 602 can completely replace the constricted lumen 714 of the crimping mechanism 702, or the rolling crimping mechanism 602 can be nested within the narrow cylindrical portion 716 of the constricted lumen 714 of the crimping mechanism 702, such that the first tapered portion 713 can feed the expandable sheath through a plurality of radially arranged, disc-shaped rollers 606.

[0119] 34-35 illustrate sheath embodiments including a distal end portion 902, which can be an extension of an outer cover extending longitudinally proximally along the sheath. FIG. 34 shows the distal end portion 902 folded (in a crimped, contracted configuration) around an introducer. FIG. 35 shows a cross-section of the distal end portion 902 folded (in a crimped, contracted configuration) around an introducer 908. The distal end portion 902 can be formed, for example, from one or more layers of material similar to or identical to those used to form the outer layer of the sheath. In some embodiments, the distal end portion 902 comprises an extension of the outer layer of the sheath, with or without another additional layer added by a separate processing technique. The distal end portion can comprise anywhere from 1 to 8 layers of material (including 1, 2, 3, 4, 5, 6, 7, and 8 layers of material). In some embodiments, the distal end portion 902 comprises multiple layers of Dyneema® material. The distal end portion 902 may extend distally past a longitudinal portion of the sheath that comprises the braided layer 904 and the elastic layer 906. Indeed, in some embodiments, the braided layer 904 may extend distally past the elastic layer 906, and the distal end portion 902 may extend distally past both the braided layer 904 and the elastic layer 906, as shown in FIGS. 34-35.

[0120] The distal end portion 902 may have a smaller collapsed diameter than more proximal portions of the sheath, thereby creating a tapered appearance. This provides a smooth transition between the introducer / dilator and the sheath, thereby ensuring that the sheath does not become seated against tissue during insertion into the patient. This smaller collapsed diameter may be the result of multiple folds (e.g., 1, 2, 3, 4, 5, 6, 7, or 8 folds) circumferentially positioned (evenly or unevenly spaced) around the distal end portion. For example, circumferential segments of the distal end portion may be mated with and then seated against adjacent outer surfaces of the distal end portion, thereby forming overlapping folds. In the collapsed configuration, the overlapping portions of the folds extend longitudinally along the distal end portion 902. Examples of creasing methods and fold configurations are described in U.S. Patent Application Nos. 14 / 880,109 and 14 / 880,111, each of which is incorporated by reference in its entirety. Score marks can be utilized as an alternative or in addition to the creases in the distal end portion. Both the score marks and creases in the distal end portion 902 allow for expansion of the distal end portion as the delivery system passes through and facilitate retraction of the delivery system into the sheath upon completion of the procedure. In some embodiments, the distal end portion of the sheath (and / or vessel dilator) can be reduced from the sheath's inner diameter (e.g., 8 mm) to 3.3 mm (10F), reducing it to the guidewire diameter so that the sheath and / or vessel dilator 300 can be passed over a guidewire.

[0121] In some embodiments, a distal end section is added, the sheath and its tip are crimped, and the crimp of the distal end section and sheath can be maintained by the following method: As described above, the distal end section 902 can be an extension of the outer layer of the sheath. Alternatively, a separate multi-layer tube can be heat-bonded to the remainder of the sheath before the tip crimping step. In some embodiments, this separate multi-layer tube is heat-bonded to the distal extension of the outer layer of the sheath to form the distal end section 902. To crimp the sheath after tip attachment, the sheath is heated over a small mandrel. The distal end section 902 can be folded around the mandrel to form the folded configuration shown in FIG. 34. A fold can be added to the distal end section 902 before the tip crimping process or at an intermediate point during the tip crimping process. In some embodiments, this small mandrel can be about 2 millimeters to about 4 millimeters in diameter (including about 2.2 millimeters, about 2.4 millimeters, about 2.6 millimeters, about 2.8 millimeters, about 3.0 millimeters, about 3.2 millimeters, about 3.4 millimeters, about 3.6 millimeters, about 3.8 millimeters, and about 4.0 millimeters). The heating temperature will be below the melting point of the material being used. This will allow the material to automatically shrink to a certain degree. For example, in some embodiments, such as when Dyneema® material is used as part of the sheath outer layer and / or distal end section material, the sheath crimping process begins by heating the sheath to about 125 degrees Celsius (below the melting point of Dyneema®, which is about 140 degrees Celsius) on a 3 millimeter mandrel. This will crimp the sheath to an outer diameter of about 6 millimeters. At this point, the sheath and distal end region 902 are allowed to cool. Heat shrink tubing may then be applied. In some embodiments, the heat shrink tubing can have a melting point that is approximately the same as the melting point of the material of the distal end portion.The sheath, with the heat shrink tubing extending over it and the distal end portion 902, is again heated (e.g., to about 125°C for a sheath with a Dyneema® outer layer and distal end portion) to crimp the sheath to an even smaller diameter. A higher temperature is applied at the distal end portion 902 (e.g., about 145°C to about 155°C for Dyneema® material) to weld the layers of material together in the folded configuration shown in FIG. 34 (these folds can be added at any time during this process). The bond at the distal end portion 902 induced by the high-temperature melting step remains weak enough to be broken by passage through a delivery system. As a final step, the heat shrink tubing is removed, leaving the sheath in its crimped diameter.

[0122] 43 shows a transverse cross section near the distal end of another sheath embodiment, at a location distal to the longitudinal direction of the braided layer. Sheath 501 includes inner polymer layer 513, outer polymer layer 517, and outer cover 561. A method for compressing the distal portion of the expandable sheath includes covering the distal portion of expandable sheath 501 in a pre-crimped state with outer cover layer 561 having a melting temperature TM1 lower than the melting temperatures TM2 of the inner and outer polymer layers, and heating at least a region, less than the entire overlap area between cover layer 561 and expandable sheath 501, to a first temperature equal to or greater than TM2 to melt both cover layer 561 and outer polymer layer 517 of expandable sheath 501. The method may include forming an attachment region 569 between the outer polymer layer 517 and the mandrel, inserting a mandrel into the lumen of the expandable sheath 501, crimping at least a portion, such as a distal portion, of the expandable sheath 501, and heating the outer cover layer 561 covering at least the distal portion of the expandable sheath 501 to a second temperature that is equal to or greater than the melting temperature TM1 of the outer cover layer 561 and less than the melting temperature TM2 of the inner and outer polymer layers for a first predetermined time window.

[0123] Advantageously, this method avoids the risk that a tear initiated at a split or fracture line (such as perforation 813 shown in FIG. 29) will deviate from the intended axial tear propagation direction due to imperfections (weak points or unintended apertures) in the heat shrink tubing. Additionally, this method allows for the selection of an outer cover layer made from a material that can be heated to a lower temperature than required for the inner or outer layers of the expandable sheath to form properly attached folds to one another.

[0124] The inner polymer layer 513, outer polymer layer 517, and outer cover layer 561 can be crimped, for example, from a pre-compressed diameter of about 8.3 mm to a compressed diameter of about 3 mm. Figure 44 shows a transverse cross section of the embodiment of Figure 43 during crimping. Folds 563 are formed along the outer layer 561 during crimping. Heating to a second temperature is sufficient to melt the outer cover layer 561 and attach the folds 563 to each other while avoiding similar melting and attachment of the inner and outer polymer layers.

[0125] The method of compressing the distal portion of the expandable sheath can further include covering the expandable sheath 510 and the outer cover layer 561 with heat shrink tubing (HST) before, during, or after heating to a second temperature. This second temperature further acts to shrink the HST and 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 561 are sufficiently seated against each other in the desired compressed state and allowed to cool for a sufficient period of time.

[0126] According to some embodiments, the HST may also be used as a heat shrink tape, wrapped around the outer cover layer 561 and the expandable sheath 501 and heated to apply external radial pressure.

[0127] According to some embodiments, non-heat shrink tape may be used in place of the heat shrink tubing.

[0128] FIG. 45 shows the distal portion of the expandable sheath 501 having the expandable braid 521. The distal portion is covered by an outer cover layer 561, which is shown extending a length L1 to the distal edge 567 of the expandable sheath 501. D1 denotes the distal diameter of the expandable sheath 501 in a pre-compressed state. FIG. 46 shows the distal portion of the expandable sheath 501 in a compressed state, with a distal diameter D2 smaller than D1. 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 (FIGS. 44 and 46) along the outer cover layer 561 and layers 517 and 513 due to the diameter reduction when the compressed state is reached. It is desirable to promote a tight fit between the folds 563. As used herein, the term "moderate fit" refers to a fit force that is large enough to form a structural cover that maintains the expandable sheath 501 in a compressed state prior to advancing the DS components through the lumen of the expandable sheath 501, yet low enough that advancing the DS components through the lumen of the expandable sheath 501 disrupts or separates the fit portions 565 between the folds 563 (FIG. 44), thereby allowing expansion of the expandable sheath 501.

[0129] The outer cover layer 561 is selected so that its melting temperature TM1 is lower than the melting temperature TM2 of the polymer layers of the expandable sheath 100 to promote the formation of folds 563 in the outer cover layer 561 with moderate adhesion while avoiding similar melting and adhesion of folds in the polymer layers 513 and 517 of the expandable sheath 501.

[0130] According to some embodiments, the outer cover layer 561 is low density polyethylene. Other suitable materials, such as polypropylene and thermoplastic polyurethane, as known in the art, may also be used to form the outer cover layer 561.

[0131] Figures 45 and 46 show perspective views of one embodiment of a sheath similar to or identical to Figures 43 and 44. The outer cover layer 561 and the expandable sheath 501 have been heated to a first temperature TM2 at the proximal end of the outer cover layer 561 along the circumferential interface therebetween to form a circumferential proximal attachment region 569.

[0132] According to some embodiments, the outer cover layer 561 is attached to the exterior surface (e.g., outer polymer layer) of the expandable sheath 501 at various attachment zones, such as along longitudinally oriented attachment lines. According to some embodiments, the outer cover layer 561 is attached to the exterior surface of the expandable sheath 501 by a plurality of circumferentially spaced attachment zones. The circumferential distance between adjacent attachment zones is selected so that folds 563 can be formed therebetween. Attachment zones such as 569 ensure that the outer cover layer 561 remains attached to the expandable sheath 501 at all times during either the compressed or expanded state of the expandable sheath 501.

[0133] According to some embodiments, covering with the outer cover layer 561 is performed such that after crimping of the expandable sheath 501, the outer layer 561 covers the pre-formed folds of the inner layer 513 and / or outer layer 517 of the sheath 501.

[0134] According to some embodiments, the bond between the folds 563 is by an adhesive having a medium adhesive strength.

[0135] The sheath embodiments described herein may include various lubricious outer coatings, including hydrophilic or hydrophobic coatings, and / or surface blooming additives or coatings.

[0136] 27 shows another embodiment of a sheath 500 that includes a tubular inner layer 502. The inner layer 502 may be formed from a resilient thermoplastic material, such as nylon, and may include multiple cuts or score lines 504 along its length such that the tubular layer 502 is divided into multiple long, thin ribs or sections 506. As the delivery device 10 is advanced through the tubular layer 502, the score lines 504 elastically expand or open, thereby spreading the ribs 506 and increasing the diameter of the layer 502 to accommodate the delivery device.

[0137] In other embodiments, the score lines 504 can be configured as apertures or cutouts having various geometric shapes, such as rhomboid, hexagonal, etc., or combinations thereof. In the case of hexagonal apertures, the apertures can be irregular hexagons having a relatively long axial dimension to reduce foreshortening of the sheath upon expansion of the sheath.

[0138] The sheath 500 may further include an outer layer (not shown), which may comprise a relatively low durometer resilient thermoplastic material (e.g., Pebax, polyurethane, etc.) and may be bonded (e.g., with an adhesive or by welding, such as by heat welding or ultrasonic welding, etc.) to the inner nylon layer. Attaching the outer layer to the inner layer 502 may reduce axial movement of the outer layer relative to the inner layer during radial expansion and contraction of the sheath. The outer layer may also form the distal end of the sheath.

[0139] 28 illustrates another embodiment of a braided layer 600 that can be used in combination with any of the sheath embodiments described herein. The braided layer 600 can include multiple braided sections 602, in which the filaments of the braided layer are braided together, and non-braided sections 604, in which the filaments extend axially without being braided or twisted together. In some embodiments, the braided sections 602 and non-braided sections 604 can alternate along the length of the braided layer 600 or can be incorporated in any other suitable pattern. The ratio of the length of a given braided layer 600 to the braided sections 602 and non-braided sections 604 can allow for selection and control of the expansion and foreshortening characteristics of the braided layer.

[0140] 47 shows one embodiment 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 the polymer layer, as visualized under fluoroscopy, for illustrative purposes. As shown in FIG. 47, the expandable braided layer 621 comprises a plurality of crossing struts 623, which may further form a distal crown 633, for example, in the form of a distal loop or distal eyelet located at a distal portion of the expandable sheath 601.

[0141] The expandable sheath 601 is configured to be advanced in a pre-compressed state to a target area, such as along the abdominal aorta or an aortic bifurcation. At the target area, the clinician must stop further advancement of the expandable sheath 601 and introduce a DS through its lumen to facilitate expansion of the expandable sheath 601. To this end, the clinician should receive a real-time indication of the position of the expandable sheath as it is advanced. According to one aspect of the present invention, at least one radiopaque marker configured to allow visualization of the position of the expandable sheath under fluoroscopy is provided in or along at least one region of the expandable braided layer 621.

[0142] According to one embodiment, at least one of the distal crowns 633 comprises a radiopaque marker. According to some embodiments, the distal crowns 633 comprise at least one gold-plated crown 635 configured to function as a radiopaque marker (FIG. 47). It will be apparent that gold plating is merely an example, and the crown 635 can comprise other radiopaque materials known in the art, such as tantalum, platinum, and iridium.

[0143] Because the expandable sheath 601 comprises an expandable braided layer 621 having a plurality of intersecting struts 623 disposed along its length, this structure can be advantageously used for more convenient incorporation of radiopaque elements.

[0144] According to some embodiments, struts 623 further comprise at least one radiopaque strut 625 having a radiopaque core. For example, drawn filled tubing (DFT) with a gold core (such as that supplied by Fort Wayne Metals Research Products Corp.) can serve as radiopaque strut 625. FIG. 47 shows an example expandable braided layer 621 comprising a plurality of low-opacity struts or filaments 623 and radiopaque struts or filaments 625a, 625b, and 625c. In some examples, struts 625a and 625c can be made from a single wire that extends along the path of strut 625a, forms a loop at distal crown 635, and extends therefrom along the path of strut 625c. Thus, a single wire, such as a DFT wire, may be used to form radiopaque struts 625a and 625c and radiopaque distal crown 635.

[0145] Because radiopaque wires such as DFT wire tend to be expensive, the expandable braided layer 621 can comprise a plurality of radiolucent or low radiolucency struts 623 made from shape memory alloys such as nitinol wire and polymer wires such as PET, each intertwined with at least one radiopaque strut 625 (FIG. 47).

[0146] According to some embodiments, radiopaque wires are embedded within the polymer braid, such as the outer polymer layer 617 or the inner polymer layer 615, and these radiopaque wires are made from a low opacity material.

[0147] Advantageously, in accordance with the present invention, an expandable braid embedded within an expandable sheath is used to improve real-time visualization of the sheath position under fluoroscopy by incorporating radiopaque markers along specific portions of the expandable sheath.

[0148] According to yet another aspect of the present invention, a radiopaque tube can be threaded over the distal crown or distal loop 633 or a radiopaque rivet can be swaged onto the distal crown or distal loop 633 to improve visibility under fluoroscopy.

[0149] 36 shows a longitudinal cross-section of another embodiment of the expandable sheath 11 (positioned on a mandrel 91 during the manufacturing process and under compression by a heat shrink tube 51). The sheath 11 includes a braided layer 21 but does not have the elastomeric layer described in the previous embodiment. Heat applied during the shrinking process can promote at least partial melting of the inner polymer layer 31 and the outer polymer layer 41. Because the filaments of the braid define open cells between them, an uneven outer surface can be formed when the inner polymer layer 31 and the outer polymer layer 41 melt into these cell openings and coat the filaments of the braided layer 21.

[0150] To mitigate the formation of uneven surfaces, buffering polymer layers 61 a, 61 b ​​configured to evenly spread radial forces during sheath compression are added between the inner layer 31 and the outer layer 41 of the sheath 11. A first buffering layer 61 a is disposed between the inner polymer layer 31 and the braided layer 21, and a second buffering layer 61 b ​​is disposed between the outer polymer layer 41 and the braided layer 21.

[0151] The buffer layers 61 a, 61 b ​​may comprise a porous material having a plurality of micropores or nanopores 63 (FIGS. 37-38) in a porous interior region. One such material includes, but is not limited to, expanded polytetrafluoroethylene (ePTFE). Advantageously, the porous buffer layers may be formed with a minimum thickness h1 required to provide sufficient diffusion of compressive forces to prevent uneven surface formation along the inner and outer polymeric layers 31, 41. The thickness h1 is measured radially (from the inner surface to the outer surface) of the buffer layer and can be from about 80 microns to about 1000 microns (e.g., about 80 microns, about 90 microns, about 100 microns, about 110 microns, about 120 microns, about 130 microns, about 140 microns, about 150 microns, about 160 microns, about 170 microns, about 180 microns, about 200 microns, about 250 microns, about 300 microns, about 350 microns, about 400 microns, about 450 microns, about 500 microns, about 550 microns, about 600 microns, about 650 microns, about 700 microns, about 750 microns, about 800 microns, about 850 microns, about 900 microns, about 950 microns, and about 1000 microns). In some embodiments, the thickness h1 ranges from about 110 to 150 microns.

[0152] However, when the buffer layers include a plurality of micropores or nanopores 63 (FIGS. 37-38), the inner and outer polymer layers 31, 41 may melt into the pores of the buffer layers 61a, 61b when heated during the manufacturing process. To prevent the inner and outer polymer layers 31, 41 from melting into the pores 63 of the buffer layer 61, a first sealing layer 71a may be disposed between the inner and outer polymer layers 31, 61a, and a second sealing layer 71b may be disposed between the outer and second buffer layers 41, 61b (as shown in FIG. 36). These sealing layers 71a, 71b may have a higher melting point than the polymer layers 31, 41 and may be formed from a non-porous material (such as, but not limited to, polytetrafluoroethylene) to prevent fluid flow therethrough. The thickness h2 (FIG. 37) of each sealing layer 71 measured radially from the inner surface to the outer surface of the sealing layer can be much thinner than the buffer layer 61, for example, about 15 to about 35 microns (including about 15 microns, about 20 microns, about 25 microns, about 30 microns, and about 35 microns).

[0153] While advantageous for the reasons discussed above, this additional buffering and sealing can increase the complexity and time required to manufacture the sheath 11. Advantageously, providing a single sealed buffering member configured to perform both buffering and sealing functions (rather than providing two separate buffering and sealing layers, each configured to perform one function) reduces sheath manufacturing time and significantly simplifies the process. In accordance with one aspect of the present invention, a single sealed buffering member is provided that is configured to be disposed between the inner and outer polymeric layers of the sheath and the central braided layer. The single sealed buffering member includes a buffering layer and a sealing surface configured to prevent leakage / melting into the pores in the radial direction.

[0154] 37 illustrates one embodiment of a unitary sealed cushioning member 81'. The cushioning member 81' includes a cushioning layer 61 having a width thickness h1 as described hereinabove, which is fixedly attached to a corresponding sealing layer 71 having a smaller thickness h2 to form a sealing surface. The sealing layer 71 and cushioning layer 61 are pre-assembled or pre-attached to one another, such as by gluing and welding, to together form the unitary member 81'.

[0155] 38 illustrates one embodiment of a single sealed buffer member 81 comprising a buffer layer 61 having a width thickness h1. The buffer layer 61 comprises at least one sealed surface 65 configured to face either the inner polymer layer 31 or the outer polymer layer 41 when assembled into the sheath 11. According to some embodiments, the sealed surface 65 is formed by a surface treatment configured to fluidly seal the surface of the buffer layer 61. As such, the sealed surface 65 can be the same material as the buffer layer 61.

[0156] According to another aspect of the present invention, and as described above, with reference to FIG. 36, a minimum of three layers may be sufficient to maintain the expandability of the sheath with suitable resistance to axial elongation. This is achieved by eliminating the need to incorporate additional elastomeric layers into the sheath, thereby advantageously reducing manufacturing costs and simplifying the manufacturing procedure. The sheath does not necessarily return to its initial diameter, but rather may remain at its expanded diameter upon passage through the valve in the absence of the elastomeric layer.

[0157] 39-40 illustrate an expandable sheath 101 similar to the expandable sheath 100 shown in FIG. 3 but without the elastomeric layer 106. The inner layer 103 and outer layer 109 may be structured and configured to resist axial elongation of the sheath 101 during expansion. However, in this proposed configuration, the absence of an elastomeric layer results in the sheath 101 maintaining its expanded diameter along the sheath portion proximal to the valve rather than necessarily contracting to its initial diameter D1 after longitudinal passage through the valve. FIG. 39 is a schematic illustration of the sheath 101 remaining at its expanded diameter D2 along the proximal portion of the valve passage.

[0158] Thus, an expandable sheath for deploying a medical device is provided, comprising a first polymer layer, a braided layer radially outward of the first polymer layer, and a second polymer layer radially outward of 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. When a medical device is inserted into the sheath, the diameter of the sheath expands from a first diameter to a 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 embodiments, the first and second polymer layers are not necessarily configured to resist axial elongation.

[0159] According to another aspect of the present invention, an expandable sheath includes an elastomeric layer. However, unlike the elastomeric layer 106 shown in FIG. 3, this elastomeric layer is not configured to apply a substantial radial force. This elastomeric layer can still provide column strength to the sheath. By limiting the tangential (diametric) expansion of the braid, the elastomeric layer enhances the axial strength (column strength) of the braid and sheath. Therefore, using an elastomeric material with a higher tensile strength (resistance to stretching) will result in a sheath with higher column strength. Similarly, an elastomeric material under higher tension in the free state will also result in a sheath with higher column strength during compression due to its higher resistance to stretching. The pitch of any helically wound elastomeric layer is another variable that contributes to the column strength of the sheath. The added column strength ensures that the sheath will not spontaneously expand due to frictional forces applied during distal advancement and will not buckle when the delivery system is withdrawn out of the sheath.

[0160] In another optional embodiment, the elastomeric layer may be applied by dip coating in an elastomeric material (such as, but not limited to, silicone or TPU). The dip coating may be applied to the polymer outer layer or the braided layer.

[0161] Thus, an expandable sheath for deploying a medical device is provided, comprising a first polymer layer, a braided layer radially outward of the first polymer layer, an elastomeric layer radially outward of the braided layer, and a second polymer layer radially outward of the braided layer. The braided layers comprise a plurality of filaments braided together. The elastomeric layer is configured to provide the expandable sheath with sufficient column strength to resist spontaneous expansion buckling due to frictional forces applied by surrounding anatomical structures during axial sheath movement. 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. When a medical device is inserted into the sheath, the diameter of the sheath expands from a first diameter to a second diameter around the medical device, optionally while the first and second polymer layers resist axial elongation of the sheath so that the length of the sheath remains substantially constant.

[0162] According to one aspect of the present invention, there is provided a three-layer expandable sheath comprising an inner polymeric layer, an outer polymeric layer bonded to the inner polymeric layer, and a braided layer encapsulated between the inner and outer polymeric layers, wherein the braided layer comprises an elastomeric coating.

[0163] Figure 41 shows a transverse cross section of expandable sheath 201. Expandable sheath 201 comprises inner and outer polymer layers 203 and 209, and braided layer 205. Instead of the elastomeric layer described above with reference to Figure 3, braided layer 205 comprises an elastomeric coating 207. This elastomeric coating 207 may be applied directly to the filaments of braided layer 205, as shown in Figure 41. The elastomeric coating may be made from a synthetic elastomer that exhibits properties similar to those described in combination with elastomeric layer 106.

[0164] In some embodiments, the second outer polymer layer 209 is bonded to the first inner polymer layer 203 such that the braided layer 205 and elastomeric coating 207 are encapsulated between the first and second polymer layers. Additionally, the elastomeric coating applied directly to the braided filaments is configured to perform the same function as the elastomeric layer 106 (i.e., to apply a radial force to the braided layer and first polymer layer).

[0165] While the embodiment of FIG. 41 shows elastomeric coating 207 covering the entire periphery of each filament of braided layer 205, it will be understood that only a portion of the filament may be coated with elastomeric coating 207, for example, a portion that essentially constitutes the outer surface of the braided layer.

[0166] Alternatively or additionally, an elastomeric coating may be applied to other layers of the sheath.

[0167] In some embodiments, a braided layer such as that shown in FIG. 40 can have a self-contracting frame made from a shape memory material, such as, but not limited to, Nitinol. The self-contracting frame can be preset to have a free-state diameter equivalent to the initial compressed diameter D1 of the sheath, such as before being placed on a mandrel around the first polymer layer. The self-contracting frame can expand to a larger diameter D2 while an inner device, such as a prosthetic valve, passes through the lumen of the sheath, and then self-contract back to the initial diameter D1 once the valve has passed. In some embodiments, the filaments of the braid are self-contracting frames and made from a shape memory material.

[0168] According to another aspect, the expandable sheath can include an expandable braided layer attached to at least one expandable sealing layer. In some embodiments, the braided layer and the sealing layer are the only two layers of the expandable sheath. The braided layer has passive or active expandability to a first diameter, and the at least one expandable sealing layer has passive or active expandability to the first diameter. An expandable sealing layer can be useful with any of the above-described embodiments, and can be particularly advantageous in the case of a braid having a self-retracting frame or self-retracting filaments.

[0169] The braided layer may be attached or bonded to the expandable sealing layer along the entire length of the expandable sealing layer to advantageously reduce the risk of the polymer layer delaminating from the braided layer due to frictional forces that may be applied during either entry or exit through a surgical incision. At least one sealing layer may include a lubricious, low-friction material to facilitate passage of a sheath within a vessel and / or passage of a delivery device carrying the valve through a sheath.

[0170] The sealing layer is defined as a layer that is impermeable to blood flow. The sealing layer can comprise a polymer layer, a membrane, a coating, and / or fibers, such as polymer fibers. According to some embodiments, the sealing layer comprises a lubricious, low-friction material. According to some embodiments, the sealing layer is positioned radially outward from the braided layer to facilitate passage of the sheath through the vessel. According to some embodiments, the sealing layer is positioned radially inward from the braided layer to facilitate passage of the medical device through the sheath.

[0171] According to some embodiments, at least one sealing layer has passive expandability and / or contractibility. In some embodiments, the sealing layer is thicker at certain longitudinal locations of the sheath than at other locations. These thicker locations may hold the self-contracting braided layer open to a larger diameter than other longitudinal locations where the sealing layer is thinner.

[0172] By attaching the braided layer to at least one expandable sealing layer rather than encasing the braided layer between two polymer layers bonded together, the manufacturing process can be simplified and costs reduced.

[0173] According to some embodiments, the braided layer may be attached to both the outwardly expandable sealing layer and the inwardly expandable sealing layer to seal the braided layer from both sides while facilitating passage of the sheath along the vessel and passage of the medical device within the sheath. In such embodiments, the braided layer may be attached to a first sealing layer while the other sealing layer may also be attached to the first sealing layer. For example, the braided layer and the inner sealing layer may each be attached to the outer sealing layer, or the braided layer and the outer sealing layer may each be attached to the inner sealing layer.

[0174] According to some embodiments, the braided layer is further coated with a sealing coating. This can be advantageous in configurations where the braided layer is attached to only a single expandable layer. This coating ensures that the braided layer remains sealed from blood flow or other surrounding tissue even at locations along the braided layer that are not covered by the expandable layer. For example, if the braided layer is attached to a sealing layer on one side, the other side of the braided layer may receive a sealing coating. In some embodiments, the sealing coating can be used instead of or in addition to one or both of these sealing layers.

[0175] General Considerations In this description, certain aspects, advantages, and novel features of embodiments of the present disclosure are described. These disclosed methods, apparatus, and systems should not be construed as limiting. Rather, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with each other. These methods, apparatus, and systems are not limited to any particular aspect or feature or combination thereof, nor do embodiments of the present disclosure require that any one or more particular advantages be present or problems be solved.

[0176] Although some operations of embodiments of the present disclosure are described in a particular order for convenience, it should be understood that this description method encompasses reordering unless a particular order is required by specific language set forth below. For example, operations described sequentially may, in some examples, be reordered or performed simultaneously. Moreover, for simplicity, the accompanying drawings may not show the various ways in which the disclosed methods can be utilized in combination with other methods. Furthermore, the present description sometimes uses terms such as "provide" or "achieve" to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations corresponding to these terms may vary depending on the specific implementation and are readily discernible by those skilled in the art.

[0177] In this application and claims, the singular forms "a," "an," and "the" include the plural unless the context clearly dictates otherwise. Furthermore, the term "comprises" means "comprising." Furthermore, the terms "coupled" and "associated" generally mean electrically, electromagnetically, and / or physically (e.g., mechanically or chemically) coupled or linked and do not exclude the presence of intermediate elements between coupled or associated items unless specifically stated to the contrary.

[0178] In the context of this application, the terms "lower" or "upper" are used interchangeably with the terms "inflow" and "outflow," respectively. Thus, for example, the lower end of a valve is the inflow end of the valve and the upper end of the valve is the outflow end of the valve.

[0179] As used herein, the term "proximal" refers to a position, orientation, or portion of a device that is closer to the user and farther from the implantation site. As used herein, the term "distal" refers to a position, orientation, or portion of a device that is farther from the user and closer to the implantation site. Thus, for example, proximal movement of a device is movement of the device toward the user, and distal movement of the device is movement of the device away from the user. The terms "longitudinal" and "axial," unless otherwise specified, refer to axial extension in the proximal and distal directions.

[0180] Unless otherwise indicated, all numbers expressing dimensions, amounts of ingredients, molecular weights, percentages, temperatures, forces, times, and the like as used in the specification or claims are to be understood as modified by the term "about." Thus, unless otherwise indicated implicitly or explicitly, the numerical parameters presented are approximations that may be determined by the desired properties required and / or detection limits under testing conditions / methods well known to those skilled in the art. When fully and clearly distinguishing an embodiment from the prior art discussed, the number of that embodiment is not an approximation unless the term "about" is recited. Furthermore, not all alternatives listed herein are equivalents.

[0181] In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it is to be understood that these illustrated embodiments are merely preferred examples and should not be construed as limiting the scope of the disclosure. Rather, the scope of the disclosure is at least as broad as the appended claims. Accordingly, we claim all that comes within the scope and spirit of those claims. [Explanation of symbols]

[0182] 10 Delivery device 11 Expandable Sheath 12 Artificial heart valves, artificial devices, and implants 14 Steerable guide catheter 16 Balloon catheter 18 Handle part 20. Long and thin guide shaft 21 braided layers 31 Inner polymer layer 41 outer polymer layer 51 Heat shrink tubing 61 Buffer layer 61a buffer polymer layer, buffer layer, first buffer layer 61b Buffer polymer layer, buffer layer, second buffer layer 63 Micropores and nanopores 65 Sealed surface 71 Sealing layer 71a first sealing layer 71b Second sealing layer 81 Cushioning material 90 Assembly, introducer device 91 Mandrel 92 Introducer housing 100 Expandable Sheath 101 Expandable Sheath 102 first layer, inner layer, first polymer layer, polymer inner layer, polymer layer, inner polymer layer 103 Inner layer 104 Second layer, braided layer 106 Third layer, elastic layer, elastomer layer 108 fourth layer, outer layer, outermost layer, outer polymer layer, polymer outer layer, polymer layer 109 Outer layer 110 Components, filaments, braided filaments 110A filament 110B filament 112 Central lumen, sheath lumen 114 Central axis 116 Strands, Ribbons, Bands, Elastic Bands 116A Elastic band 116B Elastic Band 118 Cylindrical mandrel 120 ePTFE layer, inner layer 122 ePTFE layer, outer layer 124 Heat shrink tube layer, heat shrink tape layer, heat shrink layer 126 Ridges, folds, 128 longitudinally extending groove 130 Code 132 Arrow direction 134 unit cells 136 Space 140 distal end portion 142 distal end 150 portions 152 Loops 200 equipment 201 Expandable Sheath 202 Containment Container 203 Inner polymer layer 204 Chamber 205 Braided layer 206 Closed End 207 Elastomer Coating 208 Open end 209 Outer polymer layer 210 Thermally Expandable Materials 212 Cap 214 Heating System 300 Vasodilator 301 Sheath 302 Shaft member 304 Nosecone 306 Retaining member, capsule 308 Proximal end portion 310 Circumferential space 312 Shaft 314 Balloon 400 layers of heat shrink tubing 401 Heat Shrink Tubing Layer 402 Marked line 404 Circular Opening 406 Long carved line 408 overhang 500 sheath 501 Expandable Sheath 502 Tubular inner layer 504 Marked line 506 Long thin rib or piece 510 Expandable Sheath 513 Inner polymer layer 517 Outer polymer layer 521 Expandable Braided Body 561 outer cover, outer cover layer, outer layer 563 creases 565 Mounting part 567 Distal Edge 569 Mounting Area 600 braided layers 601 Braided layer, expandable sheath 602 Roller-based crimp mechanism, rolling crimp mechanism, braided part 604 First end surface, first side, non-braided portion 605 second end surface, second side 606 Disc-shaped roller 606a-f Disc-shaped roller 608 Connector 610 circular edge 612 first side surface, front surface 614 Second side surface, rear surface 615 Inner polymer layer 616 First Arm 617 Outer polymer layer 618 Second Arm 619 Fixtures 620 volts 621 Expandable Braided Layer 623 Crossed struts, low impermeability filaments 625 Radiopaque Strut 625a Radiopaque struts, radiopaque filaments 625b Radiopaque struts, radiopaque filaments 625c Radiopaque struts, radiopaque filaments 633 Distal Crown, Distal Loop 635 Gold-plated crowns, distal crowns, radiopaque distal crowns 700 Crimp Device 702 Crimp mechanism 704 Long and narrow base 706 Long and thin mandrel 708 Retention mechanism 710 first end piece 711 Second end piece 712 Conical end part 713 First tapered section 714 Stenotic Lumen 715 Narrow end 716 Narrow cylindrical section 718 Second tapered section 719 Narrow end 720 Outer surface 722 Inner surface 724 Cylindrical end section 726 End 728 Slender Sliding Track 730 Reversible Fixture 802 Inner layer 804 braided layer 806 Elastic layer, elastomer layer 808 Outer layer 809 Heat Shrink Tubing Layer 811 Crack 813 Perforation 815 bonded seams 817 Delivery System 902 distal end portion 904 Braided layer 906 Elastic layer 908 Introducer D1 Distal diameter of the expandable sheath 501 in a pre-compressed state, initial diameter, initial compressed diameter D2 distal diameter, expanded diameter L1 length TM1 Melting temperature of outer cover layer 561 TM2 Melting temperature of the inner and outer polymer layers h1 Thickness, width thickness h2 thickness

Claims

1. 1. An expandable sheath for deploying a medical device, comprising: a first polymer layer; a braided layer radially outward of the first polymer layer, the braided layer comprising a plurality of filaments braided together; a second polymer layer located radially outward of the braided layer and bonded to the first polymer layer such that the braided layer is enveloped between the first polymer layer and the second polymer layer; at least one buffer layer positioned between the braided layer and an adjacent polymer layer; Equipped with the buffer layer has a porous interior region for dissipating radial forces acting between the filaments of the braided layer and the adjacent polymer layer; when the medical device passes through the sheath, the diameter of the sheath expands from a first diameter to a second diameter around the medical device; An expandable sheath wherein the diameter of the sheath expands from a first diameter to a second diameter around a medical device as the medical device passes through the sheath while resisting axial elongation of the sheath so that the length of the sheath remains substantially constant.

2. 10. The expandable sheath of claim 1, wherein the buffer layer comprises a sealed surface positioned between the porous interior region and the adjacent polymer layer, the sealed surface having a higher melting point than the adjacent polymer layer and being thinner than the porous interior region of the buffer layer.

3. 3. The expandable sheath of claim 2, wherein the sealed surface is a sealing layer attached to the cushioning layer.

4. 4. The expandable sheath of claim 2 or 3, wherein the sealed surface is a surface of the buffer layer, the sealed surface being continuous with the porous interior region of the buffer layer and formed from the same material as the porous interior region.

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