Catheter introducer releasably coupled to a normally expanded stretchable sheath

Abstract

Disclosed herein are introducer sheaths and methods of using the same. The sheaths (40) minimize trauma to the patient's vasculature by including an introducer (100) sized and configured to be received within an expandable sheath. The system includes a coupling mechanism (200) for releasably coupling the introducer to the expandable sheath. Engaging the coupling mechanism allows the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter, to a collapsed / narrowed configuration in which the expandable sheath has a second, smaller, outer diameter due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath.

Description

CATHETER INTRODUCER RELEASABLY COUPLED TO A NORMALLY EXPANDED STRETCHABLE SHEATHCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Application No. 63 / 653,704, filed June 20, 2024, which is incorporated by reference in its entirety for all purposes.TECHNICAL FIELD

[0002] The present application is directed to an expandable sheath and introducer for use with catheter-based technologies for repairing and / or replacing heart valves, as well as for delivering an implant, such as a prosthetic valve to a heart via the patient’s vasculature.BACKGROUND

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

[0004] Percutaneous interventional medical procedures utilize the large blood vessels of the body to reach target destinations rather than surgically opening a target site. There are many types of diseases or states that can be treated via interventional methods including coronary blockages, valve replacements (TAVR) and brain aneurysms. These techniques involve using wires, catheters, balloons, electrodes and other thin devices to travel down the length of the blood vessels from the access site to the target site. The devices have a proximal end which the clinician controls outside of the body and a distal end inside the body, which is responsible for treating the disease state. Percutaneous interventional procedures offer several advantages over open surgical techniques. First, they require smaller incision sites, which reduces scarring and bleeding as well as infection risk. Procedures are also less traumatic to the tissue, so recovery times are reduced. Finally, interventional techniques can usually be performed much faster, and with fewer clinicians participating in the procedure, so overall costs are lowered. In some cases, the need for anesthesia is also eliminated, further speeding up the recovery process and reducing risk.

[0005] A single procedure typically uses several different guidewires, catheters, and balloons to achieve the desired effect. One at a time, each tool is inserted and then removed from the access site sequentially. For example, a guidewire is used to track to the correct location within the body. Next a balloon may be used to dilate a section of narrowed blood vessel. Last, an implant may be delivered to the target site. Because catheters are frequently inserted and removed, introducer sheaths are used to protect the local anatomy and simplify the procedure.

[0006] An introducer sheath can be used to safely introduce a delivery apparatus into a patient’s vasculature (for example, the femoral artery). Introducer sheaths are conduits that seal onto the access site blood vessel to reduce bleeding and trauma to the vessel caused by catheters with rough edges. An introducer sheath generally has an elongated sleeve that is inserted into the vasculature and a housing that contains one or more sealing valves that allow a delivery apparatus to be placed in fluid communication with the vasculature with minimal blood loss. Once the introducer sheath is positioned within the vasculature, the shaft of the delivery apparatus is advanced through the sheath and into the vasculature, carrying the prosthetic device. Expandable introducer sheaths, formed of highly elastomeric materials, allow for the dilating of the vessel to be performed by the passing prosthetic device.

[0007] One method to reduce push forces through the blood vessel and minimize vessel trauma, is to provide a sheath and introducer with as minimal diameter as possible. However, very thin delivery sheaths present challenges of strength and durability. Additionally or alternatively, thicker layered sheaths can be provided but necessitate high push forces to advance the delivery device / implant through the sheath. On method to reduce push forces through the sheath is to predilate the sheath by passing a relatively large dilator (for example, 22 French dilator) into the sheath. This is done during sheath prep, prior to sheath insertion into the patient and / or with the sheath at least partially inserted into the patient. The challenge with this method is that it can be difficult with regard to physical strength of the user (for example, grip and arm strength) to advance the dilator into sheath, the possible trauma to the patient’s blood vessel during sheath advancement and dilation, and damage to the sheath caused by the dilator. This procedure requires a series of steps utilizing several different components (the introducer, the sheath, and the dilator). Accordingly, there remains a need for improvements to the devices, systems and methods of introducing and dilating sheaths, for example by reducing the number of components and the steps of the procedure.SUMMARY

[0008] Aspects of the present expandable sheath and introducer system can minimize trauma to the vessel and damage to the sheath and prosthetic device by reducing the push force through the vessel and the number of components and steps of the procedure. Aspects ensure that the blood vessel is not damaged during efforts to advance or dilate the expandable sheath. Additional aspects of the present expandable sheath can minimize trauma to the vessel by allowing for temporary expansion of a portion of the introducer sheath to accommodate a delivery system, followed by a return to the original diameter once the delivery system passes through. Some aspects can comprise a sheath with a smaller profile than that of prior art introducer sheaths. Furthermore, certain implementations can reduce the length of time a procedure takes, as well as reduce the risk of a longitudinal or radial vessel tear-, or plaque dislodgement, because less push force is required and only one sheath is used, rather than several different sizes of sheaths.

[0009] An implementation of the present disclosure provides an expandable sheath releasably coupled to an introducer, wherein the expandable sheath stretches axially and / or compresses radially, providing a sheath and introducer with a reduced profile during advancement into / through the patient’s blood vessel.

[0010] In one of its basic configurations, the present disclosure provides a sheath system for deploying a medical device is releasably coupled to an introducer in a collapsed / narrowed configuration for insertion into the blood vessel. This basic configuration can preferably be provided with any one or more of the features described elsewhere herein, in particular with those of the examples described hereafter. However, it should be understood that the basic configuration can preferably also be provided with any one or more of the features shown in the figures and / or described in conjunction with the figures, either in addition to or alternatively to the features of the examples described hereafter.

[0011] In some examples, the sheath system includes an expandable sheath having a central lumen extending therethrough and an introducer sized and configured to be received within the central lumen of the expandable sheath.

[0012] In some examples, the introducer includes a coupling mechanism releasably coupling the introducer to the expandable sheath proximate a distal end of the expandable sheath.

[0013] In some examples, engaging the coupling mechanism with the expandable sheath allows the expandable sheath to move from a first configuration to a second configuration.

[0014] In some examples, when in the first configuration, the expandable sheath has a first outer diameter (DI), and when in the second configuration, the expandable sheath has a second, smaller, outer diameter (D3) due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath.

[0015] In some examples, engagement between the coupling mechanism and the expandable sheath causes the expandable sheath to axially stretch and radially compress.

[0016] In some examples, engaging the coupling mechanism with the expandable sheath and distal movement of the introducer causes the length of the expandable sheath to increase from a first length (LI) to a second, longer, length (L2).

[0017] In some examples, the overall length of the introducer is greater than an overall length of the expandable sheath.

[0018] In some examples, the coupling mechanism is configured to engage the expandable sheath as the introducer moves distally within the expandable sheath.

[0019] In some examples, the coupling mechanism is movable between a locked position, where the coupling mechanism is coupled to the expandable sheath, and an unlocked position, where the coupling mechanism is uncoupled / released from the expandable sheath.

[0020] In some examples, the coupling mechanism extends radially from the introducer.

[0021] In some examples, the coupling mechanism extends radially from the introducer and engages a corresponding optional coupling feature or surface provided on an inner surface of the expandable sheath.

[0022] In some examples, the coupling mechanism extends radially from the introducer and engages the expandable sheath by an interference connection.

[0023] In some examples, the expandable sheath includes a sheath housing at a proximal end of the expandable sheath, and the introducer includes an introducer housing at a proximal end of the introducer, wherein at least one of the sheath housing or the introducer housing include a locking mechanism for releasably coupling the introducer with the expandable sheath in the collapsed / narrowed configuration, such that in a locked configuration the locking mechanism fixes the axial and / or rotational position of the introducer with respect to the expandable sheath.

[0024] In some examples, the expandable sheath includes: a first polymeric layer; a braided layer radially outward of the first polymeric layer, the braided layer including a plurality of filamentsbraided together; a resilient elastic layer radially outward of the braided layer, the elastic layer being configured to apply radial force to the braided layer and the first polymeric layer; and a second polymeric layer radially outward of the elastic layer and bonded to the first polymeric layer such that the braided layer and the elastic layer are encapsulated between the first and second polymeric layers; wherein when a medical device is passed through the expandable sheath, the diameter of the expandable sheath expands from a first diameter to a second diameter around the medical device; and wherein the sheath resiliently returns to the first diameter by radial force applied by the elastic layer upon passage of the medical device.

[0025] In some examples, the first and second polymeric layers optionally include a plurality of longitudinally-extending folds when the sheath is at the first diameter.

[0026] In some examples, as a medical device is passed through the sheath, the plurality of longitudinally-extending folds at least partially unfold to allow the sheath to radially expand.

[0027] A further example of the present disclosure provides a method of positioning an introducer within an expandable sheath, the method including: providing an introducer including a coupling mechanism proximate a distal end of the introducer; inserting the introducer into a central lumen of an expandable sheath. In some examples, the method includes advancing the introducer within the central lumen of the expandable sheath toward a distal end of the expandable sheath. In some examples, the method includes engaging a coupling mechanism provided on the introducer with the expandable sheath proximate the distal end of the expandable sheath allowing the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter (DI), to a collapsed / narrowed configuration in which the expandable sheath has a second, smaller, outer diameter (D3) due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath. In some examples, the method includes disengaging the coupling mechanism from the expandable sheath allowing the expandable sheath to move from the collapsed / narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath by the introducer and / or coupling mechanism.

[0028] In some examples, engaging the coupling mechanism with the expandable sheath causes the expandable sheath to move (for example, gradually move) from the first configuration to toward the collapsed / narrowed configuration.

[0029] In some examples, the method further includes further advancing the introducer within the central lumen of the expandable sheath after engaging the coupling mechanism, causing the expandable sheath to move (for example, gradually move) from the first configuration to toward the collapsed / narrowed configuration.

[0030] In some examples, the method further includes engaging a locking mechanism provided on at least one of a sheath housing or an introducer housing when the expandable sheath is in the collapsed / narrowed configuration, such that the axial and / or rotational position of the introducer with respect to the expandable sheath is fixed, where the sheath housing is provided at a proximal end of the expandable sheath or the introducer housing provided at a proximal end of the introducer; and disengaging the locking mechanism allowing axial and / or rotational movement between the introducer and the expandable sheath.

[0031] Another example of the present disclosure provides a method of delivering a medical device into a blood vessel of a patient, the method including: providing an introducer including a coupling mechanism proximate a distal end of the introducer. In some examples, the method includes inserting the introducer into a central lumen of an expandable sheath. In some examples, the method includes advancing the introducer within the central lumen of the expandable sheath toward a distal end of the expandable sheath. In some examples, the method includes engaging a coupling mechanism provided on the introducer with the expandable sheath proximate the distal end of the expandable sheath allowing the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter (DI), to a collapsed / narrowed configuration in which the expandable sheath has a second, smaller, outer diameter (D3) due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath. In some examples, the method includes inserting the combined expandable sheath and the introducer in the second collapsed / narrowed configuration at least partially into the blood vessel of the patient. In some examples, the method includes disengaging the coupling mechanism from the expandable sheath allowing the expandable sheath to move from the collapsed / narrowed configuration to the first configuration; withdrawing the introducer from the central lumen of the expandable sheath causing the expandable sheath to move from the collapsed / narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath by the introducer and / or coupling mechanism. In some examples, themethod includes introducing a medical device into a proximal end of the central lumen of the sheath; advancing the medical device through the expandable sheath. In some examples, the method includes advancing the medical device beyond a distal opening in the expandable sheath to a treatment site within the blood vessel.

[0032] In some examples, the method further includes further advancing the introducer within the central lumen of the expandable sheath after engaging the with the expandable sheath, causing the expandable sheath to move (for example, gradually move) from the first configuration to toward the collapsed / narrowed configuration.

[0033] In some examples, the method further includes engaging an optional locking mechanism provided on at least one of a sheath housing or an introducer housing when the expandable sheath is in the collapsed / narrowed configuration, such that the axial and / or rotational position of the introducer with respect to the expandable sheath is fixed, where the sheath housing is provided at a proximal end of the expandable sheath or the introducer housing provided at a proximal end of the introducer; and disengaging the locking mechanism before disengaging the coupling mechanism from the expandable sheath thereby allowing axial and / or rotational movement between the introducer and the expandable sheath.

[0034] In some examples, advancing the medical device through the expandable sheath causes the expandable sheath to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by the medical device, and then locally contract at least partially back to the unexpanded configuration as the medical device moves within the central lumen.

[0035] In some examples, the medical device is a prosthetic device mounted in a radially crimped state on a delivery apparatus, wherein advancing the prosthetic device through the central lumen of the expandable sheath includes advancing the delivery apparatus and the prosthetic device through central lumen of the expandable sheath and into a vasculature of the patient.

[0036] In some examples, the prosthetic device includes a prosthetic heart valve, and the method further includes implanting the prosthetic heart valve at a treatment site within the patient.

[0037] In some examples, the prosthetic heart valve is mounted on a balloon catheter of the delivery apparatus as the prosthetic heart valve is advanced through the expandable sheath.

[0038] In some examples, the sheath is inserted into a femoral artery of the patient.

[0039] Various aspects of the examples described above can be combined based on desired sheath system characteristics.BRIEF DESCRIPTION OF DRAWINGS

[0040] Fig. 1 is a side view of an exemplary delivery apparatus for a cardiovascular prosthetic device.

[0041] Fig. 2 is a side view of an exemplary introducer device assembly.

[0042] Fig. 3 is a side view of an expandable sheath that can be used in combination with the introducer device assembly of Fig. 2.

[0043] Fig. 4 is a side cross-sectional view of a portion of the expandable sheath of Fig. 3.

[0044] Fig. 5 is a magnified side view of a portion of the expandable sheath of Fig. 3.

[0045] Fig. 6A is a magnified view of a portion of the expandable sheath of Fig. 3 with the outer layer removed for purposes of illustration.

[0046] Fig. 6B is a magnified side view of a portion of the braided layer of the sheath of Fig. 3.

[0047] Fig. 7 is a magnified side view of a portion of the expandable sheath of Fig. 3 illustrating expansion of the sheath as a prosthetic device is advanced through the sheath.

[0048] Fig. 8 is a partial cross-sectional side view of an introducer received within an expandable sheath with the sheath in a first configuration.

[0049] Fig. 9 is a partial cross-sectional side view of an introducer received within an expandable sheath with the sheath in a collapsed / narrowed configuration.DETAILED DESCRIPTION

[0050] The following description of certain examples of the inventive concepts should not be used to limit the scope of the claims. Other examples, features, aspects, implementations, and advantages will become apparent to those skilled in the art from the following description. As will be realized, the device and / or methods are capable of other different and obvious aspects, all without departing from the spirit of the inventive concepts. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not restrictive.

[0051] For purposes of this description, certain aspects, advantages, and novel features of the aspects of this disclosure are described herein. The described methods, systems, and apparatus should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed aspects, alone and invarious combinations and sub-combinations with one another. The disclosed methods, systems, and apparatus arc not limited to any specific aspect, feature, or combination thereof, nor do the disclosed methods, systems, and apparatus require that any one or more specific advantages be present or problems be solved.

[0052] Features, integers, characteristics, compounds, chemical moieties, or groups described in conjunction with a particular aspect or example of the present disclosure are to be understood to be applicable to any other aspect or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), and / or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and / or steps are mutually exclusive. The present disclosure is not restricted to the details of any foregoing aspects. The present disclosure extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract, and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

[0053] It should be appreciated that any patent, publication, or other disclosure material, in whole or in part, that is said to be incorporated by reference herein is incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as explicitly set forth herein supersedes any conflicting material incorporated herein by reference. Any material, or portion thereof, that is said to be incorporated by reference herein, but which conflicts with existing definitions, statements, or other disclosure material set forth herein will only be incorporated to the extent that no conflict arises between that incorporated material and the existing disclosure material.

[0054] As used in the specification and the appended claims, the singular’ forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from "about" one particular value, and / or to "about" another particular value. When such a range is expressed, another aspect includes from the one particular’ value and / or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular’ value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0055] "Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0056] The terms “proximal” and “distal” as used herein refer to regions of a sheath, catheter, or delivery assembly. “Proximal” means that region closest to handle of the device, while “distal” means that region farthest away from the handle of the device.

[0057] “Axially” or “axial” as used herein refers to a direction along the longitudinal axis of the sheath.

[0058] Throughout the description and claims of this specification, the word "comprise" and variations of the word, such as "comprising" and "comprises," means "including but not limited to," and is not intended to exclude, for example, other additives, components, integers or steps. "Exemplary" means "an example of" and is not intended to convey an indication of a preferred or ideal aspect. "Such as" is not used in a restrictive sense, but for explanatory purposes.

[0059] The expandable introducer sheaths and related componentry described herein can be used to deliver a prosthetic device through a patient’s vasculature to a procedure site within the body. The sheath can be constructed to be highly expandable and radially collapsible. Disclosed aspects of the expandable sheath can minimize trauma to the vessel by reducing push forces required to advance the sheath through the blood vessel, and / or reducing push forces required to advance the medical device and / or delivery system through the sheath. In some implementations, the expandable sheath can minimize trauma to the vessel by allowing for temporary expansion of a portion of the introducer sheath to accommodate the delivery system, followed by a return to the original diameter once the device passes therethrough. In some examples, the sheath is advanced into the blood vessel in a radially collapsed / non-expanded configuration. For example, the sheath can releasably couple to an introducer to permit axial lengthening and radial compression of the sheath. In certain examples, the introducer has a coupling mechanism to releasably couple to the sheath in a natural / uncompressed configuration and maintain coupling between the sheath and the introducer as the sheath moves to the radially collapsed / compressed configuration. In some examples, an introducer coupled to a sheath applies axial force to the sheath in a distal direction, increasing the length of the sheath. In some examples, the application of axial force to the sheath in a distal direction also decreases the diameter of the sheath. In certain examples, the system includes an optional locking mechanism for coupling the sheath andintroducer, fixing the axial and rotational movement of the introducer relative to the sheath in a collapscd / lcngthcncd state. In some implementations, the sheath can be prc-dilatcd / at least partially expanded prior to delivery of the medical device / delivery system. Pre-dilating and / or radially collapsing / lengthening the sheath can be done during sheath prep, prior to sheath insertion into the patient and / or with the sheath at least partially inserted into the patient. Various aspects of the sheath system structure provide for an expandable sheath / introducer that can be safely and predictably collapsed / contracted for advancement through the patient’s blood vessel and expands during medical device / delivery system delivery. This reduces the length of time a procedure takes, as well as reduces the risk of a longitudinal or radial vessel tear, and damage to the expandable sheath.

[0060] Example expandable introducer sheaths are disclosed, for example, in U.S. Patent No. 8,690,936, entitled “Expandable Sheath for Introducing an Endovascular Delivery Device into a Body,” U.S. Patent No. 8,790,387, entitled “Expandable Sheath for Introducing an Endovascular Delivery Device into a Body,” U.S. Patent No. 10,639,152, entitled “Expandable Sheath and Methods of Using the Same,” U.S. Patent No. 10,792,471, entitled “Expandable Sheath,” U.S. Patent No. Application No. 16 / 407,057, entitled “Expandable Sheath with Elastomeric Cross Sectional Portions,” U.S. Patent No. 10,327,896, entitled “Expandable Sheath with Elastomeric Cross Sectional Portions,” U.S. Patent No. 11,273,062, entitled “Expandable Sheath,” Application No. PCT / US2021 / 019514, entitled “Expandable sheath for introducing an endovascular delivery device in to a body,” Application No. PCT / US2021 / 031227, entitled “Expandable sheath for introducing an endovascular delivery device into a body,” Application No. PCT / US2021 / 031275, entitled “Expandable sheath for introducing an endovascular delivery device into a body,” U.S. Application No. 17 / 113,268, entitled “Expandable Sheath and Method of Using the Same,” Application No. PCT / US2021 / 058247, entitled “Self-Expanding, Two Component Sheath,” Application No. PCT / US2022 / 012785, entitled “Expandable Sheath,” U.S. Patent No. 11,051,939, entitled “Active Introducer Sheath System,” Application No.PCT / US2022 / 012684, entitled “Introducer with Sheath Tip Expander,” U.S. Application No. 17 / 078,556, entitled “Advanced Sheath Patterns,” Application No. PCT / US2021 / 025038, entitled “Low temperature hydrophilic adhesive for use in expandable sheath for introducing an endovascular delivery device into a body,” Application No. PCT / US2021 / 050006, entitled “Expandable Sheath Including Reversable Bayonet Locking Hub,” U.S. Provisional ApplicationNo. 63 / 280,251 , entitled “Expandable Sheath Gasket to Provide Hemostasis,” U.S. Provisional Application No. 63 / 530,144, entitled “Introduccr / Dilator with Folded Balloon,” and U.S. Provisional Application No. 63 / 502,907, entitled “Lead Screw Driven Sheath Dilator,” the disclosures of which are herein incorporated by reference.

[0061] Fig. 1 illustrates an exemplary sheath 40 in use with a representative delivery apparatus 10, such as a prosthetic heart valve or other prosthetic implant, to a patient. The delivery apparatus 10 illustrated can generally include a steerable guide catheter 14 and a balloon catheter 16 extending through the guide catheter 14. A prosthetic device, such as a prosthetic heart valve (prosthetic device 12), can be positioned on the distal end of the balloon catheter 16. The guide catheter 14 and the balloon catheter 16 can be adapted to slide longitudinally relative to each other to facilitate delivery and positioning of a prosthetic heart valve (prosthetic device 12) at an implantation site in a patient's body. The sheath 40 is an elongated, expandable tube that can include a hemostasis valve at the proximal end of the sheath to stop blood leakage. The guide catheter 14 includes a handle portion 18 and an elongated guide tube or shaft extending from the handle portion 18.

[0062] The prosthetic heart valve (prosthetic device 12) can be delivered into a patient’s body in a radially compressed configuration and radially expanded to a radially expanded configuration at the desired deployment site. In the illustrated example, the prosthetic heart valve (prosthetic device 12) is a plastically expandable prosthetic valve that is delivered into the patient’s body in a radially compressed configuration on a balloon of the 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 actuating another type of expansion device of the delivery apparatus). Further details regarding a plastically expandable heart valve that can be implanted using the devices disclosed herein are disclosed in U.S. Publication No. 2012 / 0123529, which is incorporated herein by reference. In some examples, the prosthetic heart valve (prosthetic device 12) can be a self-expandable heart valve that is restrained in a radially compressed configuration by a sheath or other component of the delivery apparatus and self-expands to a radially expanded configuration when released by the sheath or other component of the delivery apparatus. Further details regarding a self-expandable heart valve that can be implanted using the devices disclosed herein are disclosed in U.S. Publication No. 2012 / 0239142, which is incorporated herein by reference. In still some examples, the prosthetic heart valve (prosthetic device 12) can be amechanically expandable heart valve that comprises a plurality of struts connected by hinges 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.

[0063] Further details regarding a mechanically expandable heart valve that can be implanted using the devices disclosed herein are disclosed in U.S. Publication No. 2018 / 0153689, which is incorporated herein by reference. In still some examples, a prosthetic valve can incorporate two or more of the above-described technologies. For example, a self-expandable heart valve can be used in combination with an expansion device to assist expansion of the prosthetic heart valve.

[0064] Fig. 2 illustrates an example of an introducer device assembly 20. The assembly 20 may include the sheath 40 and an introducer 100. The introducer 100 may be positioned within a central lumen 42 (indicated in Fig. 4) of the sheath 40, as shown in Fig. 2. An optional control housing 22 may be positioned at a proximal end of the assembly and may include a sheath hub 24 and an introducer hub 30. The sheath hub 24 and introducer hub 30 may optionally couple together, as shown in Fig. 2.

[0065] The sheath 40 and introducer 100 are shown in an insertion configuration, for insertion together into the patient's vasculature. Upon insertion into the patient's vasculature, the introducer 100 may be withdrawn longitudinally from the sheath 40, leaving the sheath 40 within the patient's vasculature. Features of the sheath 40 and the introducer 100 individually are discussed below, as well as the operation of the sheath 40 and introducer 100 together.

[0066] The sheath 40 comprises an elongated body that may have a cylindrical shape. The sheath 40 has a distal end 43 and a proximal end 44, and a length LI (see Fig. 3) extending from the distal end 43 to the proximal end 44. The sheath 40 is configured to be inserted into a patient's vasculature. The sheath 40 may optionally comprise an introducer sheath that is used to introduce a delivery apparatus into the patient's vasculature.

[0067] The vasculature may comprise the blood vessels of the patient's body which may include the femoral artery or other vessels of the patient's body. The vasculature, such as the femoral artery, may be narrow or stiff, and may be difficult to easily insert a delivery apparatus therein. For example, the delivery apparatus may be larger than the vasculature, or may be unwieldy to penetrate through the skin or vasculature of the patient to pass therethrough by itself. Also, thevasculature may be too fragile to receive the delivery apparatus without use of an introducer sheath.

[0068] The sheath 40 accordingly may optionally be inserted into the patient’s vasculature prior to the delivery apparatus being introduced, to provide an entry way or guide path for the delivery apparatus 10 to introduce the delivery apparatus into the patient’s vasculature. After the sheath 40 is inserted, the sheath 40 may remain positioned within and surrounded by the patient’s vasculature. The delivery apparatus 10 may then be passed through the lumen of the sheath 40 for introduction into the patient’s body. The sheath 40 may remain in the vasculature until a desired time to remove the sheath 40.

[0069] The sheath 40 may be inserted into the vasculature percutaneously or a portion of the patient’s body may be surgically opened for the sheath 40 to access the vasculature. The delivery apparatus 10 passes through the lumen of the sheath 40 to reach a desired position in the patient's body. As shown in Fig. 1, the delivery apparatus 10 may pass through an opening at the proximal end of the sheath 40 for passage through the central lumen 42 of the sheath 40 and the vasculature of the patient. For example, in some implementations, the delivery apparatus 10 passes through an opening at the proximal end of the sheath 40 provided at the control housing 22 shown in Fig. 2.

[0070] The delivery apparatus and the assemblies disclosed herein may be used in transcatheter aortic valve implantation (TAVI). The delivery apparatus and the systems disclosed herein may be utilized for transarterial access, including transfemoral access, to a patient’s heart.

[0071] The sheath 40 may optionally include a strain relief portion 46 at the proximal end 44 of the sheath 40. The strain relief portion 46 may be sized larger than a proximate portion of the sheath 40 and may seal the entry point of the vasculature, to reduce the possibility of blood or other fluid being released between the exterior surface of the sheath 40 and the vasculature. The strain relief portion 46 provides a transition between the larger diameter proximal opening of the sheath 40 and the smaller diameter distal portion / opening of the sheath 40 as the medical device and / or introducer 100 are inserted into the central lumen 42 of the sheath 40. In some examples, a seal 48 is optionally positioned along the length of the sheath 40 to further prevent blood or other fluid flow from passing around the sheath 40 toward and out of the proximal end 44 of the sheath 40.

[0072] Fig. 3 illustrates a side view of an exemplary expandable sheath 40 that can be used in the introducer device assembly of Fig. 2. As shown in Fig. 3, the sheath hub 24 is optionally positioned at the proximal end 44 of the sheath 40. The sheath hub 24 may optionally include an internal chamber for the delivery apparatus 10 to be passed through to be delivered to the patient's vasculature. The sheath hub 24 may be configured to remain external to the patient's vasculature when the sheath 40 is inserted therein and may be configured to remain external to the patient's skin for a percutaneous implantation of the sheath 40. The sheath hub 24 may be configured for a user (such as a surgeon) to grip to manipulate the sheath 40.

[0073] The sheath hub 24 may optionally comprise a cylindrical body and may include a coupler 29 for coupling to another housing or component of the system. The sheath hub 24 may optionally include a fluid port 26 for passing fluid such as blood to or from the patient's vasculature. Tubing 27 with a valve 28 may be coupled to the fluid port 26, for passing fluid through the fluid port 26 and for sealing flow of the fluid through the fluid port 26.

[0074] In some examples, the introducer sheath need not include a sheath hub 24. For example, the sheath 40 can be an integral part of a component of the delivery apparatus 10, such as the guide catheter. For example, the sheath can extend from the handle portion 18 of the guide catheter. Additional examples of introducer devices and expandable sheaths can be found in U.S. Patent No. 11,273,062, which is incorporated by reference in its entirety.

[0075] Figs. 4 and 5 illustrate a cross-sectional view and a side view, respectively, of a portion of the expandable sheath 40. As shown in Fig. 5, the sheath 40 can have a natural, unexpanded outer diameter DI. In certain examples, the expandable sheath 40 may optionally include a plurality of co-axial layers extending along at least a portion of the length LI of the sheath (Fig. 3). For example, with reference to Fig. 4, the expandable sheath 40 can include a first layer / inner layer 52 (also referred to as an inner layer), a second layer / braided layer 54 disposed around and radially outward of the inner layer 52, a third layer / elastic layer 56 disposed around and radially outward of the braided layer 54, and a fourth layer / outer layer 58 (also referred to as an outer layer) disposed around and radially outward of the elastic layer 56. In the illustrated configuration, the inner layer 52 can define the central lumen 42 extending along a central axis Cl. In some examples, the sheath 40 may optionally include the inner layer 52 without the outer layer 58, or the outer layer 58 without the inner layer 52, depending upon the particular characteristics desired.

[0076] Referring to Fig. 5, when the sheath 40 is in an unexpanded state, the inner layer 52 and / or the outer layer 58 can form longitudinally-extending folds or creases such that the surface of the sheath comprises a plurality of ridges 62 (also referred to herein as “folds”). The ridges 62 can be circumferentially spaced apart from each other by longitudinally-extending valleys 64. When the sheath expands beyond its natural diameter DI, the ridges 62 and the valleys 64 can level out or be taken up as the surface radially expands and the circumference increases, as further described below. When the sheath collapses back to its natural diameter, the ridges 62 and valleys 64 can reform.

[0077] In some examples, the inner layer 52 and / or the outer layer 58 can comprise a relatively thin layer of polymeric material. For example, in some examples, the thickness of the inner layer 52 can be from 0.01 mm to 0.5 mm, 0.02 mm to 0.4 mm, or 0.03 mm to 0.25 mm. In certain aspects, the thickness of the outer layer 58 can be from 0.01 mm to 0.5 mm, 0.02 mm to 0.4 mm, or 0.03 mm to 0.25 mm.

[0078] In some examples, the inner layer 52 and / or the outer layer 58 can comprise a lubricious, low-friction, and / or relatively non-elastic material. In particular examples, the inner layer 52 and / or the outer layer 58 can comprise a polymeric material having a modulus of elasticity of 400 MPa or greater. Exemplary materials can include ultra-high-molecular- weight polyethylene (UHMWPE) (for example, Dyneema®), high-molecular- weight polyethylene (HMWPE), or polyether ether ketone (PEEK). With regal'd to the inner layer 52 in particular, such a low coefficient of friction materials can facilitate passage of the prosthetic device through the central lumen 42. Other suitable materials for the inner and outer layers can include polytetrafluoroethylene (PTFE), expanded polytetrafluoroethylene (ePTFE), ethylene tetrafluoroethylene (ETFE), nylon, polyethylene, polyether block amide (for example, Pebax), and / or combinations of any of the above. Some examples of a sheath 40 can include a lubricious liner on the inner surface of the inner layer 52. Examples of suitable lubricious liners include materials that can further reduce the coefficient of friction of the inner layer 52, such as PTFE, polyethylene, polyvinylidene fluoride, and combinations thereof. Suitable materials for a lubricious liner also include other materials desirably having a coefficient of friction of 0.1 or less.

[0079] Additionally, some examples of the sheath 40 can include an optional exterior hydrophilic coating on the outer surface of the outer layer 58. Such a hydrophilic coating canfacilitate insertion of the sheath 40 into a patient’s vessel, reducing potential damage. Examples of suitable hydrophilic coatings include the Harmony™ Advanced Lubricity Coatings and other Advanced Hydrophilic Coatings available from SurModics, Inc., Eden Prairie, MN. DSM medical coatings (available from Koninklijke DSM N.V., Heerlen, the Netherlands), as well as other hydrophilic coatings (for example, PTFE, polyethylene, polyvinylidene fluoride), are also suitable for use with the sheath 40. Such hydrophilic coatings may also be optionally included on the inner surface of the inner layer 52 to reduce friction between the sheath and the delivery system, thereby facilitating the use and improving safety. In some examples, a hydrophobic coating, such as Perylene, may be used on the outer surface of the outer layer 58 or the inner surface of the inner layer 52 in order to reduce friction.

[0080] In certain examples, the second layer / braided layer 54 can includes a braided material. Figs. 6A and 6B illustrate the sheath 40 with the outer layer 58 removed to expose the elastic layer 56. With reference to Figs. 6A and 6B, the braided layer 54 can comprise a plurality of members or filaments 60 (for example, metallic or synthetic wires or fibers) braided together. The braided layer 54 can have any desired number of filaments 60, which can be oriented and braided together along any suitable number of axes. For example, with reference to Fig. 6B, the filaments 60 can include a first set of filaments 60A oriented parallel to a first axis A, and a second set of filaments 60B oriented parallel to a second axis B . The filaments 60A and 60B can be braided together in a biaxial braid such that filaments 60A oriented along axis A form an angle 0 with the filaments 60B oriented along axis B. In certain examples, the angle 0 can be from 5° to 70°, 10° to 60°, 10° to 50°, or 10° to 45°. In the illustrated example, the angle 0 is 45°. In some examples, the filaments 60 can also be oriented along three axes and braided in a triaxial braid, or oriented along any number of axes and braided in any suitable braid pattern.

[0081] The braided layer 54 can extend along substantially the entire length LI of the sheath 40, or alternatively, can extend only along a portion of the length of the sheath. In particular examples, the filaments 60 can be wires made from metal (for example, Nitinol, stainless steel, etc.), or any of various polymers or polymer composite materials, such as carbon fiber. In certain examples, the filaments 60 can be round, and can have a diameter of from 0.01 mm to 0.5 mm, 0.03 mm to 0.4 mm, or 0.05 mm to 0.25 mm. In some examples, the filaments 60 can have a flat cross-section with dimensions of 0.01 mm x 0.01 mm to 0.5 mm x 0.5 mm, or 0.05 mm x 0.05 mm to 0.25 mm x 0.25 mm. In one example, filaments 60 having a flat cross-section can havedimensions of 0. 1 mm x 0.2 mm. However, other geometries and sizes are also suitable for certain examples. If a braided wire is used, the braid density can be varied. Some examples have a braid density of from ten picks per inch to eighty picks per inch, and can include eight wires, sixteen wires, or up to fifty-two wires in various braid patterns. In some examples, the braided layer 54 can be laser cut from a tube, or laser-cut, stamped, punched, etc., from sheet stock and rolled into a tubular configuration. The braided layer 54 can also be woven or knitted, as desired.

[0082] The third layer / elastic layer 56 can be a resilient, elastic layer (also referred to as an elastic material layer). In certain examples, the elastic layer 56 can be configured to apply force to the underlying inner layer 52 and braided layer 54 in a radial direction (for example, toward the central axis Cl of the sheath) when the sheath expands beyond its natural diameter by passage of the delivery apparatus through the sheath. Stated differently, the elastic layer 56 can be configured to apply encircling pressure to the layers of the sheath beneath the elastic layer 56 to counteract expansion of the sheath. The radially inwardly directed force is sufficient to cause the sheath to collapse radially back to its unexpanded state after the delivery apparatus is passed through the sheath.

[0083] In the illustrated example, the elastic layer 56 can optionally comprise one or more members configured as strands, ribbons, or bands 66 helically wrapped around the braided layer 54. For example, in the illustrated sheath 40, the elastic layer 56 comprises two elastic bands 66A and 66B wrapped around the braided layer with opposite helicity, although the elastic layer may comprise any number of bands depending upon the desired characteristics. The elastic bands 66A and 66B can be made from, for example, any of a variety of natural or synthetic elastomers, including silicone rubber, natural rubber, any of various thermoplastic elastomers, polyurethanes such as polyurethane siloxane copolymers, urethane, plasticized polyvinyl chloride (PVC), styrenic block copolymers, polyolefin elastomers, etc.

[0084] In some examples, the elastic layer can comprise an elastomeric material having a modulus of elasticity of 200 MPa or less. In some examples, the elastic layer 56 can comprise a material exhibiting an elongation to break of 200% or greater, or an elongation to break of 400% or greater. The elastic layer 56 can also take other forms, such as a tubular layer comprising an elastomeric material, a mesh, a shrinkable polymer layer such as a heat-shrink tubing layer, etc. In lieu of, or in addition to, the elastic layer 56, the sheath 40 may also include an optional elastomeric or heat-shrink tubing layer around the outer layer 58. Examples of such elastomericlayers are disclosed in U.S. Patent Nos. 9,301 ,841 , 10,792,471 , and 10,856,981 , which are incorporated herein by reference. In some examples, the clastic layer 56 can also be radially outward of the polymeric outer layer 58.

[0085] In some examples, one or both of the inner layer 52 and / or the outer layer 58 can be configured to resist axial shortening of the sheath 40 when the sheath expands radially. More particularly, one or both of the inner layer 52 and / or the outer layer 58 can resist stretching against longitudinal forces caused by friction between a prosthetic device and the inner surface of the sheath such that the length LI remains substantially constant as the sheath expands and contracts radially. As used herein with reference to the length LI of the sheath, the term “substantially constant” means that the length LI of the sheath increases by not more than 1%, by not more than 5%, by not more than 10%, by not more than 15%, or by not more than 20%. Meanwhile, with reference to Fig. 6B, the filaments 60A and 60B of the braided layer can be allowed to move angularly relative to each other such that the angle 9 changes as the sheath expands and contracts. This, in combination with the longitudinal ridges 62 (folds) in the inner and outer layers 52, 58, can allow the central lumen 42 to expand as a prosthetic device is advanced through it.

[0086] In some examples, the inner layer 52 and the outer layer 58 can be heat-bonded during the manufacturing process such that the braided layer 54 and the elastic layer 56 are encapsulated between the inner layer 52 and the outer layer 58. More specifically, in certain examples, the inner layer 52 and the outer layer 58 can be adhered to each other through the spaces between the filaments 60 of the braided layer 54 and / or the spaces between the elastic bands 66. The inner layer 52 and outer layer 58 can also be bonded or adhered together at the proximal and / or distal ends of the sheath. In certain examples, the inner layer 52 and outer layer 58 are not adhered to the filaments 60. This can allow the filaments 60 to move angularly relative to each other, and relative to the inner layer 52 and outer layer 58, allowing the diameter of the braided layer 54, and thereby the diameter of the sheath, to increase or decrease. As the angle 0 between the filaments 60A and 60B changes, the length of the braided layer 54 can also change. For example, as the angle 9 increases, the braided layer 54 can foreshorten, and as the angle 9 decreases, the braided layer 54 can lengthen to the extent permitted by the areas where the inner layer 52 and outer layer 58 are bonded. However, because the braided layer 54 is not adhered to the inner layer 52 and outer layer 58, the change in length of the braided layer that accompanies a changein the angle 6 between the filaments 60A and 60B does not result in a significant change in the length LI of the sheath.

[0087] Fig. 7 illustrates radial expansion of the sheath 40 as a prosthetic device 12 is passed through the sheath 40 in the direction of arrow 82 (for example, distally). As the prosthetic device 12 is advanced through the sheath 40, the sheath 40 can resiliently expand to a second diameter D2 that corresponds to a size or diameter of the prosthetic device 12. As the prosthetic device 12 is advanced through the sheath 40, the prosthetic device 12 can apply longitudinal force to the sheath 40 in the direction of motion by virtue of the frictional contact between the prosthetic device 12 and the inner surface of the sheath 40. However, as noted above, the inner layer 52 and / or the outer layer 58 can be optionally configured to resist axial elongation such that the length LI of the sheath 40 remains constant, or substantially constant. This can reduce or prevent the braided layer 54 from lengthening, and thereby constricting the central lumen 42.

[0088] Meanwhile, in some examples, the angle 0 between the filaments 60A and 60B can increase as the sheath 40 expands to the second diameter D2 to accommodate the prosthetic device 12. This can cause the braided layer 54 to foreshorten. However, because the filaments 60 are not engaged or adhered to the inner layer 52 or outer layer 58, the shortening of the braided layer 54 attendant to an increase in the angle 9 does not affect the overall length LI of the sheath. Moreover, because of the longitudinally-extending ridges 62 / folds formed in the inner layer 52 and outer layer 58, the inner layer 52 and outer layer 58 can expand to the second diameter D2 without rupturing, in spite of being relatively thin and relatively non-elastic. In this manner, the sheath 40 can resiliently expand from its natural diameter D 1 to a second diameter D2 that is larger than the diameter DI as a prosthetic device 12 is advanced through the sheath 40, without lengthening, and without constricting. Thus, the force required to push the prosthetic device 12 through the sheath 40 is significantly reduced.

[0089] Additionally, because of the radial force applied by the elastic layer 56, the radial expansion of the sheath 40 can be localized to the specific portion of the sheath 40 occupied by the prosthetic device 12. For example, with reference to Fig. 7, as the prosthetic device 12 moves distally through the sheath 40, the portion of the sheath 40 immediately proximal to the prosthetic device 12 can radially collapse back to the initial diameter DI under the influence of the elastic layer 56. The inner layer 52 and outer layer 58 can also buckle as the circumference of the sheath 40 is reduced, causing the ridges 62 and the valleys 64 to reform. This can reduce thesize of the sheath 40 required to introduce a prosthetic device of a given size. Additionally, the temporary, localized nature of the expansion can reduce trauma to the blood vessel into which the sheath 40 is inserted, along with the surrounding tissue, because only the portion of the sheath 40 occupied by the prosthetic device 12 expands beyond the sheath’s natural diameter and the sheath 40 collapses back to the initial diameter once the device has passed. This limits the amount of tissue stretched in order to introduce the prosthetic device 12, and the amount of time for which a given portion of the vessel is dilated to allow the prosthetic device 12 to pass.

[0090] In addition to the advantages above, the expandable sheath 40 examples described herein can provide surprisingly superior performance relative to known introducer sheaths. For example, it is possible to use a sheath 40 configured as described herein to deliver a prosthetic device having a diameter that is two times larger, 2.5 times larger, or even three times larger than the natural outer diameter of the sheath 40. For instance, in one example, 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 natural outer diameter of 3.7 mm. As the prosthetic valve was advanced through the sheath 40, the outer diameter of the portion of the sheath 40 occupied by the prosthetic valve increased to 8 mm. In other words, it was possible to advance a prosthetic device having a diameter more than two times the outer diameter of the sheath 40 through the sheath 40, during which the outer diameter of the sheath 40 resiliently increased by 216%. In another example, a sheath 40 with an initial or natural outer diameter of 4.5 mm to 5.0 mm can be configured to expand to an outer diameter of 8 mm to 9 mm.

[0091] Figs. 8-9 illustrate partial cross-sectional side views of an example introducer 100 used with the introducer device assembly and sheath 40 of Figs. 1-3. As described herein, the introducer 100 is sized and configured to be received within the central lumen 42 of the sheath 40 and facilitate movement of the sheath 40 between an initial / neutral configuration and a second (collapsed / narrowed) configuration. In the second (collapsed / narrowed) configuration, the sheath 40 has a reduced diameter helping to reduce the push force required to advance the combined sheath 40 and introducer 100 through the patient’s vasculature. The reduced diameter sheath 40 / introducer 100 also helps to reduce the risk of a longitudinal or radial vessel tear, or plaque dislodgement, because less push force is required and only one sheath is used, rather than several different sizes of sheaths.

[0092] As shown in Figs. 8-9, the introducer 100 includes an elongated body portion 110 having a generally cylindrical shaped structure. In some examples, introducer 100 includes a tapered distal region 112. In some examples, the tapered distal region 112 optionally includes a rounded distal end surface at the distal end 102 of the introducer 100. The introducer 100 is optionally coupled at its proximal end 104 to the introducer hub 30. The introducer hub 30 may optionally be configured to be gripped by an operator such that radial and / or axial force applied to the introducer hub 30 is translated to the introducer 100. In some examples, both the elongated body portion 110 and the introducer hub 30 include a central lumen extending therethrough. The central lumen of introducer hub 30 can be axially aligned and in fluid communication with the central lumen of the elongated body portion 110 of the introducer 100. For example, in some implementations, the central lumen of the introducer hub 30 and the central lumen of the elongated body portion 110 are sized and configured to allow fluid and / or a medical device to pass therethrough.

[0093] As illustrated in Figs. 8-9, the introducer 100 is sized and configured to be received within the central lumen 42 of the sheath 40. As described herein, the introducer 100 is movable within the sheath 40, causing the sheath 40 to move to between the initial unexpanded configuration illustrated in Fig. 8, and the radially collapsed / narrowed configuration illustrated in Fig. 9. Fig. 8 provides the sheath 40 at the initial unexpanded diameter DI. In some examples, the initial diameter DI may be the natural / neutral, unexpanded diameter of the sheath 40. As illustrated in Fig. 9, as the introducer 100 moves in a distal direction (arrow A), the sheath 40 moves to / toward the radially collapsed / narrowed configuration. In the radially collapsed / narrowed configuration the diameter (D3) of the sheath 40 is less than the initial, unexpanded, diameter (DI) of the sheath 40.

[0094] In some examples, the introducer 100 is releasably coupled to the sheath 40 for moving the sheath 40 between the initial unexpanded configuration and the radially collapsed / narrowed configuration. For example, the introducer 100 can be releasably coupled to the sheath 40 via a coupling mechanism 200. As described herein, the coupling mechanism 200 can be provided on the sheath 40 and / or introducer 100 and includes an engagement mechanism / feature for releasably engaging with an opposing portion of the sheath 40 and / or introducer 100. For example, as described herein, the coupling mechanism 200 can include a pin, clip, keyed or interlocking interface, threaded surface, press fit interface, interference fit interface, snap fitinterface, bayonet connection, magnetic connection, and mechanical and / or chemical fastener, provided on either or both the introducer 100 and sheath 40 that is suitable for rclcasably coupling the introducer 100 with the sheath 40.

[0095] Engagement between the coupling mechanism 200 and the sheath 40 and / or introducer 100, couples the sheath 40 and introducer 100 such that axial and / or rotational movement of the introducer 100 results in a corresponding axial and / or rotational movement of the sheath 40. For example, as illustrated in Fig. 9, engagement of the coupling mechanism 200 combined with distal axial movement of the introducer 100 within the sheath 40 causes the sheath 40 to move to / toward the collapsed / narrowed configuration in response to the axially directed force exerted on the sheath 40 by the introducer 100 and / or coupling mechanism 200. That is, with the introducer 100 coupled to the sheath 40, axial force is applied to the introducer 100 in the distal direction (arrow A) is transferred to the sheath 40, causing the sheath 40 to narrow, decreasing the diameter and / or profile of the sheath 40 from the first diameter (DI) to the smaller, second / smaller diameter (D3).

[0096] Additionally, in some examples, as axial force is applied to the introducer 100 in a distal direction (arrow A), the sheath 40 lengthens axially from the first length (LI), shown in Fig. 8, to the second, longer, length (L2), shown in Fig. 9. In some examples, the sheath 40 is optionally configured to stretch axially in response to the axial movement of the introducer 100. That is, axial movement of introducer 100 causes the expandable sheath 40 to axially stretch as the length increases from the first length (LI) to the second length (L2), while the sheath 40 also radially decreases / contracts.

[0097] As described herein, the coupling mechanism 200 can be provided on the introducer 100 or the sheath 40. That is, in some examples, the coupling mechanism 200 is provided on the introducer 100, while in some examples, the coupling mechanism 200 is provided on the sheath 40. In some examples, complementary components of the coupling mechanism 200 are optionally provided on both the introducer 100 and the sheath 40. In some examples, the complementary components of the coupling mechanism 200 are provided on both the introducer 100 and the sheath 40. As described herein, example coupling mechanisms 200 include a pin, clip, keyed or interlocking interface, threaded surface, press fit interface, interference fit interface, snap fit interface, bayonet connection, magnetic connection, and mechanical and / orchemical fastener, provided on either or both the introducer 100 and sheath 40 that is suitable for rclcasably coupling the introducer 100 with the sheath 40.

[0098] For example, in some implementations, the coupling mechanism 200 includes a radially extending projection or surface extending from the elongated body portion 110 of the introducer 100. In some examples, the coupling mechanism 200 extends radially outward from the elongated body portion 110 of the introducer 100 and engages an optional corresponding coupling feature or surface provided on the inner surface of the central lumen 42 of the sheath 40. For example, in some implementations, coupling mechanism 200 projects radially from the elongated body portion 110 and engages the inner surface of the central lumen 42 of the sheath 40 and / or a corresponding coupling feature or surface provided on the sheath 40 and / or on the central lumen 42 of the sheath 40. In some examples, the coupling mechanism 200 projects radially from the introducer 100 and engages the sheath 40 by an interference connection. Similarly, in some examples, the coupling mechanism 200 may extend radially inward from the inner surface of the central lumen 42 of the sheath 40. In this implementation, the coupling mechanism 200 projects radially inward from the surface of the central lumen 42 of the sheath 40 and engages the outer surface of the elongated body portion 110 and / or a corresponding coupling feature provided on the elongated body portion 110 if the introducer 100.

[0099] As illustrated in Figs. 8-9, the coupling mechanism 200 is optionally provided proximate the distal end 43 of the sheath 40 and / or the distal end 102 of the introducer 100. In some examples, the coupling mechanism 200 (and / or the corresponding coupling feature or surface) is optionally provided on the sheath 40 at a location between the distal end 43 and proximal end 44 of the sheath 40. In some examples, the coupling mechanism 200 is optionally provided on the introducer 100 at a location between the distal end 102 of the introducer 100 and the proximal end 104 of the introducer 100. For example, the coupling mechanism 200 can be provided adjacent the tapered distal region 112 of the introducer 100.

[0100] In some examples, the coupling mechanism 200 engages the sheath 40 and / or introducer 100 as the introducer 100 moves within the central lumen 42 of the sheath 40. For example, in some implementations, as the introducer 100 is moved in a distal direction (arrow A) within the central lumen 42 of the sheath 40, the coupling mechanism 200 (whether provided on the introducer 100, sheath 40 and / or both) engages with the sheath 40 and / or introducer 100, thereby coupling the introducer 100 and sheath 40. Further distal movement of the introducer100 within the sheath 40 causes the sheath 40 to move from the first unexpanded configuration to / toward the collapscd / narrowcd configuration where the sheath 40 and / or central lumen 42 has a smaller diameter (D3). To disengage the coupling mechanism 200, the introducer 100 is moved in a proximal direction (arrow B), and the coupling mechanism 200 disengages and the introducer 100 and sheath 40 uncouple, allowing the sheath 40 to move back to / toward the first unexpanded configuration.

[0101] As described herein, in some implementations, the coupling mechanism 200 optionally includes a pin, clip, keyed or interlocking interface, threaded surface, or any other structure that may require rotational movement for coupling. In this example, coupling and uncoupling of the coupling mechanism 200 requires a corresponding rotational movement of the introducer 100 and / or sheath 40. For examples, in some implementations, the introducer 100 is moved in a distal direction (arrow A) within the central lumen 42 of the sheath 40 until the coupling mechanism 200 is located axially within the sheath 40 at a position proximate with the corresponding coupling feature provided on introducer 100 and / or sheath 40. With the coupling mechanism 200 at the desired position, rotational force is applied to either one of the introducer 100 and / or sheath 40 such that engagement between the coupling mechanism 200 and the corresponding coupling feature is facilitated. Similarly, to disengage the coupling mechanism 200, an opposite rotational force is applied to the introducer 100 and / or sheath 40 such that the coupling mechanism 200 is disengaged, and the introducer 100 can be removed in a proximal direction (arrow B) from the sheath 40.

[0102] In some examples, the coupling mechanism 200 and / or introducer 100 is optionally movable between a locked and an unlocked position. In the locked position, the axial and / or rotational position of the introducer 100 is fixed with respect to the sheath 40. For example, with the coupling mechanism 200 engaged such that the introducer 100 is coupled to the sheath 40, introducer 100 can be moved into a locked position such that engagement of the coupling mechanism 200 is fixed. Similarly, when the introducer 100 is in the unlocked position, the coupling mechanism 200 can be disengaged and the introducer 100 freely movable with respect to the sheath 40.

[0103] As illustrated in Figs. 8-9, in some examples, the introducer 100 is optionally sized and configured to have a greater overall length than the overall length of the sheath 40. Where the overall length of the introducer 100 is measured between the distal end 102 and theproximal end 104 of the elongated body portion 1 10, and the overall length of the sheath 40 is measured between the distal end 43 and the proximal end 44 of the sheath 40. In some examples, as illustrated in Figs. 8-9, when the introducer 100 is disposed within the central lumen 42 of the sheath 40, the distal end 102 of the introducer 100 extends beyond the distal end 43 of the sheath 40. In some examples, as illustrated in Figs. 2-3, the proximal end 44 of the sheath 40 is optionally coupled to a sheath hub 24. Similarly, the proximal end 104 of the introducer 100 is optionally coupled to the introducer hub 30.

[0104] In some examples, an optional locking mechanism 250 is included for releasably coupling the introducer 100 with the sheath 40 in the collapsed / narrowed configuration, such that in a locked configuration the locking mechanism 250 fixes the axial and / or rotational position of the introducer 100 with respect to the sheath 40. In some examples, the locking mechanism 250 is optionally provided on the sheath hub 24 and / or the introducer hub 30. For example, the locking mechanism 250 can be provided on the proximal end of the sheath hub 24 and / or the distal end of the introducer hub 30. In some examples, the locking mechanism 250 includes a press fit connection, interference fit connection, snap fit connection, a pin, thread, bayonet fastener, clip, locking key and / or any other suitable releasable connection type provided between and coupling the sheath hub 24 and the introducer hub 30.

[0105] A method of positioning an introducer 100 with respect to an expandable sheath 40 is disclosed. It is contemplated that the introducer 100 can be used with any example sheath 40 described herein. The introducer 100 is sized and configured to be received and movable within the central lumen 42 of the expandable sheath 40. As described in more detail herein, as the introducer 100 moves within the central lumen 42 of the sheath 40 the coupling mechanism 200 engages the sheath 40 and / or introducer 100. Further movement of the introducer 100 in the distal direction (arrow A) causes the sheath 40 to move from the initial / neutral configuration to the second, collapsed / narrowed, configuration. In the second, collapsed / narrowed, configuration the sheath 40 has a reduced diameter helping to reduce the push force required to advance the combined sheath 40 and introducer 100 through the patient’s vasculature.

[0106] Fig. 8 illustrates the introducer 100 received within the central lumen 42 of the sheath 40. As illustrated in Fig. 9, as the introducer 100 moves in a distal direction (arrow A) within the central lumen 42 of the sheath 40, the coupling mechanism 200 engages the introducer 100 with the expandable sheath 40 allowing the sheath 40 to move from the first configuration tothe second (collapsed / narrowed) configuration where the sheath 40 has a second, smaller, outer diameter (D3). In some examples, engaging the coupling mechanism 200 causes the expandable sheath 40 to move from the first configuration to toward the collapsed / narrowed configuration. In some examples, engaging the coupling mechanism 200 and further distal advancement of the introducer 100 causes the expandable sheath 40 to move from the first configuration to / toward the second, collapsed / narrowed, configuration. As described herein, the sheath 40 moves to / toward the second, collapsed / narrowed, configuration in response to the axially directed force exerted on the expandable sheath 40 by the introducer 100 and / or coupling mechanism 200 as it is advanced distally (arrow A) within the central lumen 42 of the sheath 40.

[0107] In some examples, with the sheath 40 in the second, collapsed / narrowed, configuration, a locking mechanism 250 is optionally engaged coupling the sheath hub 24 and the introducer hub 30. With the locking mechanism 250 engaged, the axial and / or rotational position of the introducer 100 with respect to the expandable sheath 40 is fixed.

[0108] The locking mechanism 250 can be disengaged to allow axial and / or rotational movement between the introducer 100 and the expandable sheath 40. With the locking mechanism 250 disengaged, the sheath 40 and / or introducer 100 can be moved axially, including removal of the introducer 100 from the central lumen 42 of the sheath 40. For example, movement of the introducer 100 in the proximal direction (arrow B), causes the coupling mechanism 200 to disengage between the introducer 100 and the sheath 40. Further proximal movement of the introducer 100 with respect to the sheath 40 causes the sheath 40 to move from the collapsed / narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath 40 by the introducer 100 and / or coupling mechanism 200.

[0109] A method of using the introducer 100 and sheath 40 described herein to implant a prosthetic device into a patient is described. The introducer 100 and sheath 40 as described herein is provided. The distal end 102 of the introducer 100 is inserted into the proximal end 44 of the sheath 40 and advanced into the central lumen 42 of the sheath 40 as shown in Fig. 8. The introducer 100 is advanced within the central lumen 42 of the sheath 40 in a distal direction (arrow A) toward the distal end 43 of the sheath 40.

[0110] As described herein and illustrated in Fig. 9, as the introducer 100 moves distally within the sheath 40, the coupling mechanism 200 couples the introducer 100 and the sheath 40.With the coupling mechanism 200 engaged, further distal advancement of the introducer 100 causes the expandable sheath 40 to move from the first configuration to / toward the second, collapsed / narrowed, configuration. In some examples, with the sheath 40 in the second, collapsed / narrowed, configuration, the locking mechanism 250 is optionally engaged such that the axial and / or rotational position of the introducer 100 with respect to the expandable sheath 40 is fixed and the sheath 40 is maintained in the second, collapsed / narrowed, configuration.

[0111] With the sheath 40 in the second, collapsed / narrowed, configuration, the combined expandable sheath 40 and introducer 100 are least partially advanced into the patient’s blood vessel and advanced to the treatment site. In some examples, the expandable sheath 40 is inserted into the femoral artery or other vessels of the patient’s body. The vasculature, such as the femoral artery, may be narrow or stiff, and may be difficult to easily insert a delivery apparatus therein. For example, the delivery apparatus may be larger than the vasculature, or may be unwieldy to penetrate through the skin or vasculature of the patient to pass therethrough by itself. Also, the vasculature may be too fragile to receive the delivery apparatus without the use of an introducer sheath 40. In the second, collapsed / narrowed, configuration the combined sheath 40 and introducer 100, the push force needed to advance the sheath 40 / introducer 100 into and through the patient’s blood vessel is reduced helping to minimize trauma to the vessel.

[0112] In some examples, a guidewire is optionally positioned at the treatment site and the sheath 40 and introducer 100 are advanced over the guidewire.

[0113] Once the combined sheath 40 and introducer 100 are positioned at the treatment site, the coupling mechanism 200 is disengaged between the introducer 100 and the expandable sheath 40 allowing the expandable sheath 40 to move from the second, collapsed / narrowed, configuration to the first configuration. In some examples, before the coupling mechanism 200 is disengaged, the locking mechanism 250 is disengaged allowing axial and / or rotational movement between the of the introducer 100 and the sheath 40.

[0114] With the introducer 100 movable with respect to the sheath 40, the introducer 100 is then withdrawn in a proximal direction (arrow B) within the central lumen 42 of the sheath 40. Withdrawing the introducer 100 within the central lumen 42 causes the sheath 40 to move from the second, collapsed / narrowed, configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath 40 by the introducer 100 and / orcoupling mechanism 200. As a result, the diameter of the sheath 40 increases to its natural / ncutral diameter.

[0115] The introducer 100 is then fully withdrawn from the central lumen 42 of the sheath 40, leaving the sheath 40 within the patient's vasculature. With the central lumen 42 of the sheath 40 clear, the medical device is then advanced into the central lumen 42 of the sheath 40. Accessing the treatment site may require creating an opening in the heart tissue (for example, foramen ovalis) of the patient. In some examples, a cutting instrument can be advanced through the sheath 40 to create an opening in the patient’s heart tissue.

[0116] The medical device, for example an implant, is advanced through the central lumen 42 of the sheath 40 and beyond the distal opening to the treatment site within the blood vessel and / or heart tissue. In some examples, the sheath 40 is sized and configured such that advancing the medical device through the sheath 40 causes the sheath 40 to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by the medical device, and then locally contract at least partially back to the unexpanded configuration as the medical device moves within the central lumen 42. With the distal end of the sheath 40 positioned at the treatment site, the medical device is deployed beyond distal opening of the sheath 40 and delivered to the patient.

[0117] In some examples, the medical device / implant is a prosthetic device 12 mounted in a radially crimped state on a delivery apparatus, and advancing the prosthetic device 12 through the central lumen 42 of the sheath 40 includes advancing the delivery apparatus and the prosthetic device through central lumen 42 of the sheath 40 and into a vasculature of the patient. In some examples, the prosthetic device comprises a prosthetic heart valve and the method further comprises implanting the prosthetic heart valve at a treatment site within the patient. In some examples, the prosthetic heart valve is mounted on a balloon catheter of the delivery apparatus as the prosthetic heart valve is advanced through the sheath 40.

[0118] Exemplary Aspects

[0119] In view of the described processes and compositions, hereinbelow are described certain more particularly described aspects of the disclosures. These particularly recited aspects should not, however, be interpreted to have any limiting effect on any different claims containing different or more general teachings described herein, or that the “particular” aspects aresomehow limited in some way other than the inherent meanings of the language and formulas literally used therein.

[0120] Example 1 : A sheath system for deploying a medical device, the sheath system comprising: an expandable sheath having a central lumen extending therethrough; an introducer sized and configured to be received within the central lumen of the expandable sheath, the introducer including a coupling mechanism releasably coupling the introducer to the expandable sheath proximate a distal end of the expandable sheath, wherein engaging the coupling mechanism with the expandable sheath allows the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter (DI), to a collapsed / narrowed configuration in which the expandable sheath has a second, smaller, outer diameter (D3) due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath.

[0121] Example 2: The sheath according to any example herein, particularly example 1, wherein engagement between the coupling mechanism and the expandable sheath causes the expandable sheath to axially stretch and radially compress.

[0122] Example 3: The sheath according to any example herein, particularly examples 1-2, wherein engaging the coupling mechanism with the expandable sheath and distal movement of the introducer causes a length of the expandable sheath to increase from a first length (LI) to a second, longer, length (L2).

[0123] Example 4: The sheath according to any example herein, particularly examples 1-3, wherein an overall length of the introducer is greater than an overall length of the expandable sheath.

[0124] Example 5 : The sheath according to any example herein, particularly examples 1-4, wherein the coupling mechanism is configured to engage the expandable sheath as the introducer moves distally within the expandable sheath.

[0125] Example 6 : The sheath according to any example herein, particularly examples 1-5, wherein the coupling mechanism is movable between a locked position, where the coupling mechanism is coupled to the expandable sheath, and an unlocked position, where the coupling mechanism is uncoupled / released from the expandable sheath.

[0126] Example 7: The sheath according to any example herein, particularly examples 1-6, wherein the coupling mechanism extends radially from the introducer.

[0127] Example 8 : The sheath according to any example herein, particularly examples 1-7, wherein the coupling mechanism extends radially from the introducer and engages a corresponding coupling feature or surface provided on an inner surface of the expandable sheath.

[0128] Example 9: The sheath according to any example herein, particularly example 7 or 8, wherein the coupling mechanism extends radially from the introducer and engages the expandable sheath by an interference connection.

[0129] Example 10: The sheath according to any example herein, particularly examples 1-9, wherein the expandable sheath includes a sheath hub at a proximal end of the expandable sheath, and the introducer includes an introducer hub at a proximal end of the introducer, wherein at least one of the sheath hub or the introducer hub include a locking mechanism for releasably coupling the introducer with the expandable sheath in the collapsed / narrowed configuration, such that in a locked configuration the locking mechanism fixes the axial and / or rotational position of the introducer with respect to the expandable sheath.

[0130] Example 11 : The sheath according to any example herein, particularly examples 1-10, wherein the expandable sheath includes: a first polymeric layer; a braided layer radially outward of the first polymeric layer, the braided layer comprising a plurality of filaments braided together; a resilient elastic layer radially outward of the braided layer, the elastic layer being configured to apply radial force to the braided layer and the first polymeric layer; and a second polymeric layer radially outward of the elastic layer and bonded to the first polymeric layer such that the braided layer and the elastic layer are encapsulated between the first and second polymeric layers; wherein when a medical device is passed through the expandable sheath, the diameter of the expandable sheath expands from a first diameter to a second diameter around the medical device; and wherein the sheath resiliently returns to the first diameter by radial force applied by the elastic layer upon passage of the medical device.

[0131] Example 12: The sheath according to any example herein, particularly example 11, wherein the first and second polymeric layers comprise a plurality of longitudinally- extending folds when the sheath is at the first diameter.

[0132] Example 13: The sheath according to any example herein, particularly example 12, wherein as a medical device is passed through the sheath, the plurality of longitudinally-extending folds at least partially unfold to allow the sheath to radially expand.

[0133] Example 14: A method of positioning an introducer within an expandable sheath, the method comprising: providing an introducer including a coupling mechanism proximate a distal end of the introducer; inserting the introducer into a central lumen of an expandable sheath; advancing the introducer within the central lumen of the expandable sheath toward a distal end of the expandable sheath; engaging a coupling mechanism provided on the introducer with the expandable sheath proximate the distal end of the expandable sheath allowing the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter (DI), to a collapsed / narrowed configuration in which the expandable sheath has a second, smaller, outer diameter (D3) due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the sheath; and disengaging the coupling mechanism from the expandable sheath allowing the expandable sheath to move from the collapsed / narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath by the introducer and / or coupling mechanism.

[0134] Example 15: The method according to any example herein, particularly example 14, wherein engaging the coupling mechanism with the expandable sheath causes the expandable sheath to move (for example, gradually move) from the first configuration to toward the collapsed / narrowed configuration.

[0135] Example 16: The method according to any example herein, particularly examples 14-15, further including further advancing the introducer within the central lumen of the expandable sheath after engaging the coupling mechanism, causing the expandable sheath to move (for example, gradually move) from the first configuration to toward the collapsed / narrowed configuration.

[0136] Example 17: The method according to any example herein, particularly examples 14-16, further including engaging a locking mechanism provided on at least one of a sheath hub or an introducer hub when the expandable sheath is in the collapsed / narrowed configuration, such that the axial and / or rotational position of the introducer with respect to the expandable sheath is fixed, where the sheath hub is provided at a proximal end of the expandable sheath orthe introducer hub provided at a proximal end of the introducer; disengaging the locking mechanism allowing axial and / or rotational movement between the introducer and the expandable sheath.

[0137] Example 18: A method of delivering a medical device into a blood vessel of a patient, the method comprising: providing an introducer including a coupling mechanism proximate a distal end of the introducer; inserting the introducer into a central lumen of an expandable sheath; advancing the introducer within the central lumen of the expandable sheath toward a distal end of the expandable sheath; engaging a coupling mechanism provided on the introducer with the expandable sheath proximate the distal end of the expandable sheath allowing the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter (DI), to a collapsed / narrowed configuration in which the expandable sheath has a second, smaller, outer diameter (D3) due to the axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath; inserting the combined expandable sheath and the introducer in the second collapsed / narrowed configuration at least partially into the blood vessel of the patient; disengaging the coupling mechanism from the expandable sheath allowing the expandable sheath to move from the collapsed / narrowed configuration to the first configuration; withdrawing the introducer from the central lumen of the expandable sheath causing the sheath to move from the collapsed / narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath by the introducer and / or coupling mechanism; introducing a medical device into a proximal end of the central lumen of the sheath; advancing the medical device through the expandable sheath; and advancing the medical device beyond a distal opening in the expandable sheath to a treatment site within the blood vessel.

[0138] Example 19: The method according to any example herein, particularly example 18, further including further advancing the introducer within the central lumen of the expandable sheath after engaging the with the expandable sheath, causes the expandable sheath to move (for example, gradually move) from the first configuration to toward the collapsed / narrowed configuration.

[0139] Example 20: The method according to any example herein, particularly examples 18-19, further including: engaging a locking mechanism provided on at least one of asheath hub or an introducer hub when the expandable sheath is in the collapsed / narrowed configuration, such that the axial and / or rotational position of the introducer with respect to the expandable sheath is fixed, where the sheath hub is provided at a proximal end of the expandable sheath or the introducer hub provided at a proximal end of the introducer; and disengaging the locking mechanism before disengaging the coupling mechanism from the expandable sheath thereby allowing axial and / or rotational movement between the introducer and the expandable sheath.

[0140] Example 21: The method according to any example herein, particularly examples 18-20, wherein advancing the medical device through the expandable sheath causes the expandable sheath to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by the medical device, and then locally contract at least partially back to the unexpanded configuration as the medical device moves within the central lumen.

[0141] Example 22: The method according to any example herein, particularly examples 18-21, wherein the medical device is a prosthetic device mounted in a radially crimped state on a delivery apparatus, wherein advancing the prosthetic device through the central lumen of the expandable sheath comprises advancing the delivery apparatus and the prosthetic device through central lumen of the expandable sheath and into a vasculature of the patient.

[0142] Example 23: The method according to any example herein, particularly example22, herein the prosthetic device comprises a prosthetic heart valve and the method further comprises implanting the prosthetic heart valve at a treatment site within the patient.

[0143] Example 24: The method according to any example herein, particularly example23, wherein the prosthetic heart valve is mounted on a balloon catheter of the delivery apparatus as the prosthetic heart valve is advanced through the expandable sheath.

[0144] Example 25: The method according to any example herein, particularly examples 18-24, wherein the sheath is inserted into a femoral artery of the patient.

[0145] In view of the many possible aspects to which the principles of the disclosed disclosure can be applied, it should be recognized that the illustrated aspects are only preferred examples of the disclosure and should not be taken as limiting the scope of the disclosure.Rather, the scope of the disclosure is defined by the following claims. We, therefore, claim as our disclosure all that comes within the scope and spirit of these claims.

Claims

CLAIMSWhat is claimed is:

1. A sheath system for deploying a medical device, the sheath system comprising: an expandable sheath having a central lumen extending therethrough; and an introducer sized and configured to be received within the central lumen of the expandable sheath, the introducer including a coupling mechanism releasably coupling the introducer to the expandable sheath proximate a distal end of the expandable sheath, wherein engaging the coupling mechanism with the expandable sheath allows the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter, to a narrowed configuration in which the expandable sheath has a second, smaller, outer diameter due to axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath.

2. The sheath system of claim 1, wherein engagement between the coupling mechanism and the expandable sheath causes the expandable sheath to axially stretch and radially compress.

3. The sheath system of any one of claims 1-2, wherein engaging the coupling mechanism with the expandable sheath and distal movement of the introducer causes a length of the expandable sheath to increase from a first length (LI) to a second, longer, length (L2).

4. The sheath system of any one of claims 1-3, wherein an overall length of the introducer is greater than an overall length of the expandable sheath.

5. The sheath system of any one of claims 1-4, wherein the coupling mechanism is configured to engage the expandable sheath as the introducer moves distally within the expandable sheath.

6. The sheath system of any one of claims 1-5, wherein the coupling mechanism is movable between a locked position, where the coupling mechanism is coupled to the expandable sheath, and an unlocked position, where the coupling mechanism is uncoupled / released from the expandable sheath.

7. The sheath system of any one of claims 1-6, wherein the coupling mechanism extends radially from the introducer.

8. The sheath system of any one of claims 1-7, wherein the expandable sheath includes a sheath hub at a proximal end of the expandable sheath, and the introducer includes an introducer hub at a proximal end of the introducer, wherein at least one of the sheath hub or the introducer hub include a locking mechanism for releasably coupling the introducer with the expandable sheath in the collapsed / narrowed configuration, such that in a locked configuration the locking mechanism fixes an axial and / or rotational position of the introducer with respect to the expandable sheath.

9. The sheath system of any one of claims 1-8, wherein the expandable sheath includes: a first polymeric layer; a braided layer radially outward of the first polymeric layer, the braided layer comprising a plurality of filaments braided together; a resilient elastic layer radially outward of the braided layer, the elastic layer being configured to apply radial force to the braided layer and the first polymeric layer; and a second polymeric layer radially outward of the elastic layer and bonded to the first polymeric layer such that the braided layer and the elastic layer are encapsulated between the first and second polymeric layers; wherein when a medical device is passed through the expandable sheath , the diameter of the expandable sheath expands from a first diameter to a second diameter around the medical device; and wherein the sheath resiliently returns to the first diameter by radial force applied by the elastic layer upon passage of the medical device.

10. The sheath system of claim 9, wherein the first and second polymeric layers comprise a plurality of longitudinally-extending folds when the sheath is at the first diameter.

11. The sheath system of claim 10, wherein, as a medical device is passed through the sheath, the plurality of longitudinally -extending folds at least partially unfold to allow the sheath to radially expand.

12. A method of positioning an introducer within an expandable sheath, the method comprising: providing an introducer including a coupling mechanism proximate a distal end of the introducer; inserting the introducer into a central lumen of an expandable sheath; advancing the introducer within the central lumen of the expandable sheath toward a distal end of the expandable sheath; engaging a coupling mechanism provided on the introducer with the expandable sheath proximate the distal end of the expandable sheath allowing the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter, to a narrowed configuration in which the expandable sheath has a second, smaller, outer diameter due to axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath; and disengaging the coupling mechanism from the expandable sheath allowing the expandable sheath to move from the narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath by the introducer and / or coupling mechanism.

13. The method of claim 12, wherein engaging the coupling mechanism with the expandable sheath causes the expandable sheath to gradually move from the first configuration to toward the collapsed / narrowed configuration.

14. The method of any one of claims 12-13, further including:further advancing the introducer within the central lumen of the expandable sheath after engaging the coupling mechanism, causing the expandable sheath to move from the first configuration to toward the collapsed / narrowed configuration.

15. The method of any one of claims 12-14, further including: engaging a locking mechanism provided on at least one of a sheath hub or an introducer hub when the expandable sheath is in the collapsed / narrowed configuration, such that an axial and / or rotational position of the introducer with respect to the expandable sheath is fixed, where the sheath hub is provided at a proximal end of the expandable sheath or the introducer hub provided at a proximal end of the introducer; and disengaging the locking mechanism allowing axial and / or rotational movement between the introducer and the expandable sheath.

16. A method of delivering a medical device into a blood vessel of a patient, the method comprising: providing an introducer including a coupling mechanism proximate a distal end of the introducer; inserting the introducer into a central lumen of an expandable sheath; advancing the introducer within the central lumen of the expandable sheath toward a distal end of the expandable sheath; engaging a coupling mechanism provided on the introducer with the expandable sheath proximate the distal end of the expandable sheath allowing the expandable sheath to move from a first configuration, in which the expandable sheath has a first outer diameter, to a narrowed configuration in which the expandable sheath has a second, smaller, outer diameter due to axially directed force exerted on the expandable sheath by the introducer and / or coupling mechanism as the introducer is advanced within the central lumen of the expandable sheath; inserting the combined expandable sheath and the introducer in the second collapsed / narrowed configuration at least partially into the blood vessel of the patient; disengaging the coupling mechanism from the expandable sheath allowing the expandable sheath to move from the narrowed configuration to the first configuration;withdrawing the introducer from the central lumen of the expandable sheath causing the expandable sheath to move from the narrowed configuration to the first configuration in response to the removal of the axial force exerted on the expandable sheath by the introducer and / or coupling mechanism; introducing a medical device into a proximal end of the central lumen of the sheath; advancing the medical device through the expandable sheath; and advancing the medical device beyond a distal opening in the expandable sheath to a treatment site within the blood vessel.

17. The method of claim 16, further including: further advancing the introducer within the central lumen of the expandable sheath after engaging the with the expandable sheath, causing the expandable sheath to move from the first configuration to toward the narrowed configuration.

18. The method of any one of claims 16-17, further including: engaging a locking mechanism provided on at least one of a sheath hub or an introducer hub when the expandable sheath is in the collapsed / narrowed configuration, such that an axial and / or rotational position of the introducer with respect to the expandable sheath is fixed, where the sheath hub is provided at a proximal end of the expandable sheath or the introducer hub provided at a proximal end of the introducer; and disengaging the locking mechanism before disengaging the coupling mechanism from the expandable sheath thereby allowing axial and / or rotational movement between the introducer and the expandable sheath.

19. The method of any one of claims 16-18, wherein advancing the medical device through the expandable sheath causes the expandable sheath to locally expand from an unexpanded configuration at a first diameter to an expanded configuration at a second, larger, diameter in response to an outwardly directed radial force exerted on the central lumen by the medical device, and then locally contract at least partially back to the unexpanded configuration as the medical device moves within the central lumen.

20. The method of any one of claims 16-19, wherein the medical device is a prosthetic device mounted in a radially crimped state on a delivery apparatus, wherein advancing the prosthetic device through the central lumen of the expandable sheath comprises advancing the delivery apparatus and the prosthetic device through central lumen of the expandable sheath and into a vasculature of the patient.

21. The method of claim 20, wherein the prosthetic device comprises a prosthetic heart valve and the method further comprises implanting the prosthetic heart valve at a treatment site within the patient.

22. The method of any one of claims 16-21, wherein the medical device comprises a prosthetic heart valve mounted in a radially crimped state on a balloon catheter of a delivery apparatus as the prosthetic heart valve is advanced through the expandable sheath.

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