Patent ID: 12194256

DETAILED DESCRIPTION

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, embodiments, 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.

For purposes of this description, certain aspects, advantages, and novel features of the embodiments 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 embodiments, alone and in various combinations and sub-combinations with one another. The disclosed methods, systems, and apparatus are 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.

Features, integers, characteristics, compounds, chemical moieties, or groups described in conjunction with a particular aspect, embodiment or example of the invention are to be understood to be applicable to any other aspect, embodiment 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 invention is not restricted to the details of any foregoing embodiments. The invention 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.

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.

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.

“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.

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.

Disclosed embodiments of an 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 through. The expandable sheath can include, for example, an integrally formed inner tubular layer with thick and thin wall portions, wherein the thin wall portion can expand to an expanded lumen for passage of an implant and then fold back onto itself under biasing of an outer elastic tubular layer after departure of the implant. In another aspect, the expandable sheath can include one or more longitudinally oriented stiffening elements (such as rods) that are coupled to the elastic outer layer to provide stiffness for the expandable sheath. Some embodiments can comprise a sheath with a smaller profile than the profiles of prior art introducer sheaths. Furthermore, present embodiments 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 only one sheath is required, rather than several different sizes of sheaths. Embodiments of the present expandable sheath can avoid the need for multiple insertions for the dilation of the vessel.

Disclosed herein are elongate delivery sheaths that are particularly suitable for delivery of implants in the form of implantable heart valves, such as balloon-expandable implantable heart valves. Balloon-expandable implantable heart valves are well-known and will not be described in detail here. An example of such an implantable heart valve is described in U.S. Pat. No. 5,411,552, and also in U.S. Patent Application Publication No. 2012/0123529, both of which are hereby incorporated by reference. The elongate delivery sheaths disclosed herein may also be used to deliver other types of implantable devices, such as self-expanding implantable heart valves, stents or filters. The term “implantable” as used herein is broadly defined to mean anything—prosthetic or not—that is delivered to a site within a body. A diagnostic device, for example, may be an implantable.

FIG.1illustrates an exemplary sheath8in use with a representative delivery apparatus10, for delivering an implant12, or other type of implantable, to a patient. The apparatus10can include a steerable guide catheter14(also referred to as a flex catheter) and a balloon catheter16extending through the guide catheter14. The guide catheter14and the balloon catheter16in the illustrated embodiment are adapted to slide longitudinally relative to each other to facilitate delivery and positioning of the implant12at an implantation site in a patient's body, as described in detail below. The sheath8is an elongate, expandable tube that can include a hemostasis valve at the opposite, proximal end of the sheath to stop blood leakage.

Generally, during use a distal end of the sheath8is passed through the skin of the patient and inserted into a vessel, such as the trans-femoral vessel. The delivery apparatus10can be inserted into the sheath8through the hemostasis valve, and the implant12can then be delivered and implanted within the patient.

As shown inFIG.2, the sheath8includes a hub20, a flared proximal end22and a distal tip24. The hub20is constructed of a rigid cylindrical structure defining a hub lumen21and houses a hemostasis valve26and may define a side port28and have a threaded distal end30. The flared proximal end22of the sheath8includes a threaded female connector32mounted on a tubular wall structure34. The distal tip24of the sheath8is mounted over a distal end of the tubular wall structure34, as shown inFIG.3. The tubular wall structure34defines a central lumen38.

The hub20is attached to the flared proximal end22by twisting the threaded distal male end30into correspondingly threaded female connector32. This places the hub lumen21in communication with the central lumen38of the tubular wall structure34. The hemostasis valve26mediates access by the delivery apparatus10to the hub lumen21and central lumen38and ultimate deployment of the implant12in a pressurized (blood filled) environment. Side port28provides an additional access for application of saline or other fluids.

The distal tip24, meanwhile, provides some restraint to the otherwise radially expandable tubular wall structure34. The distal tip24also helps with advancement over an introducer by providing a tapered advancement surface. Further the distal tip24improves the stiffness of the sheath8at its distal tip to guard against buckling or collapse of the tubular wall structure34during torque and advancement forces.

As shown inFIG.3A, the tubular wall structure34includes an elastic outer tubular layer40and an inner tubular layer42and the distal tip24. The distal tip24generally has a tubular structure with a slightly tapering or frusto-conical distal end. The distal tip24includes an outer wall44, an inner wall46and a retainer48. The outer wall44has an axial length longer than the inner wall46. A proximal end of the outer wall44has a tubular shape with straight sides. The outer wall tapers to a neck52at its distal free end and begins to flare slightly to a cylindrical bulge50moving proximally from the distal free end. The neck52has a smaller diameter than the proximal tubular end of the outer wall44. The proximal tubular end in turn has a smaller diameter than the cylindrical bulge50.

The inner wall46has a shorter axial length than the outer wall but also has a cylindrical shape that tapers—although more gradually—toward its distal free end. An outer surface of the inner wall46and inner surface of the outer wall44define an annular space54which is configured to receive a distal free end of the elastic outer tubular layer40, as shown inFIG.3A. The annular space54bulges some due to its position subjacent the cylindrical bulge50of the outer wall44. This bulge facilitates insertion and capture of the elastic outer tubular layer. The annular space54tapers to a point moving distally as the surfaces of the outer wall44and inner wall46converge into binding contact.

The retainer48is an additional arc-shaped wall that extends along a portion of the inner surface of the inner wall46and defines its own crescent-shaped space56, as shown in the cross section ofFIG.3B. The crescent-shaped space56is configured to receive a foldable thin wall portion of the inner tubular layer42, as will be described in more detail below. The retainer48has an arc size that corresponds with a circumferential arc-length of the folded over portion of the inner tubular layer42when it is in its compressed or folded configuration. Advantageously, the distal tip24helps to increase the structural rigidity of the distal end of the tubular wall structure34, blocks blood flow between the layers and provides a smooth, tapered profile for pushing through tissue when advanced over a wire or dilator.

As shown inFIG.4, the outer tubular layer40of one embodiment has a cylindrical shape with a circular cross-section along its entire length. The outer tubular layer40defines an initial elastic lumen58extending axially through its cylindrical cross-section. The outer tubular layer is sized to accommodate the delivery passage of the patient and/or the size of the implant12to be delivered. For example, the inside diameter, ID, of the layer40may be 0.185 inches and may have a wall thickness of 0.005+/−0.001 inches for delivery of a stent-mounted heart valve through trans-femoral access. In one aspect, inner surface of the outer tubular layer40and/or outer surface of the inner tubular layer42may be treated to have or have applied thereto a lubricious coating to facilitate unfolding and folding of the inner tubular layer42.

The elastic lumen58is referred to as “initial” to designate its passive or as-formed diameter or cross-sectional dimension when not under the influence of outside forces, such as the implant12passing therethrough. It should be noted, however, that because the outer tubular layer40is comprised in the illustrated embodiment by an elastic material it may not retain its shape under even light forces such as gravity. Also, the outer tubular layer40need not have a cylindrical cross-section and instead could have oval, square or other cross-sections which generally can be configured to meet the requirements of the inner tubular layer42and/or expected shape of the implant12. Thus, the term “tube” or “tubular” as used herein is not meant to limit shapes to circular cross-sections. Instead, tube or tubular can refer to any elongate structure with a closed-cross section and lumen extending axially therethrough. A tube may also have some selectively located slits or openings therein—although it still will provide enough of a closed structure to contain other components within its lumen(s).

The outer tubular layer40, in one implementation, is constructed of a relatively elastic material that has enough flexibility to mediate the expansion induced by passage of the implant12and expansion of the inner tubular layer42while at the same time having enough material stiffness to urge the inner tubular layer back into an approximation of the initial diameter once the implant has passed. An exemplary material includes NEUSOFT. NEUSOFT is a translucent polyether urethane based material with good elasticity, vibration dampening, abrasion and tear resistance. The polyurethanes are chemically resistant to hydrolysis and suitable for overmolding on polyolefins, ABS, PC, Pebax and nylon. The polyuerthane provides a good moisture and oxygen barrier as well as UV stability. One advantage of the outer tubular layer40is that it provides a fluid barrier for the pressurized blood. Other materials having similar properties of elasticity may also be used for the elastic outer tubular layer40.

FIG.5shows another implementation of the elastic outer tubular layer40including a plurality of longitudinal rods60. The longitudinal rods60extend the length of the outer tubular layer40and protrude into the initial elastic lumen58. The longitudinal rods60are coupled to the outer tubular layer, such as by being co-extruded and/or embedded into the elastic material of the outer tubular layer, as shown inFIG.6. Advantageously, the longitudinal rods60are configured to provide a bearing surface to facilitate relative movement of the inner tubular layer42within the outer tubular layer40. This is especially helpful when the inner tubular layer42is unfolding and returning to its originally folded shape.

The longitudinal rods60may be circumferentially spaced about the inside surface of the outer tubular layer60. Although fifteen longitudinal rods60are shown in the cross-section ofFIG.5, any number, including a single one, of longitudinal rods may be employed. Also, the longitudinal rods60need not extend the entire length of the outer tubular layer60. They may instead be applied selectively depending upon the demands of the implant, application and other circumstances. Longitudinal rods60may be selectively left out of an overall spacing pattern, such as inFIG.5where approximately 90 degrees of the inside surface of the outer tubular layer40is left as an unadorned surface.

As shown inFIG.6, the longitudinal rods may have a circular cross-section so as to present a curved bearing surface into the elastic lumen58. Although diameters for the longitudinal rods60may vary, in one embodiment they are 0.004 inches in diameter. The outermost part of the longitudinal rod is positioned about 0.006 inches from the outside surface of the outer tubular layer40. In this manner, the inner edge surface of the longitudinal rods60spaces the inner tubular layer42from the surface of the outer tubular layer40, thus reducing friction or the tendency to stick and impede relative movement. In other embodiments, the longitudinal rods can have other shapes, and the shapes may change within a single rod along the longitudinal direction. As also shown inFIG.6, the material of the outer tubular layer40extends up in a slope past the midpoint of the cross-section of the longitudinal rods60for extra stability.

As shown inFIG.7, the inner tubular layer42has a thick wall portion62integrally extruded with a thin wall portion64. The thick wall portion62is approximately 0.011+/−. 001 inches and the thin wall portion66is approximately 0.0065+/−0.0010 inches. The inner tubular layer42is preferably constructed of a relatively (compared to the outer tubular layer40) stiff material such as a stiff polymer like high density polyethylene (HDPE) or an equivalent polymer. Integral construction, such as integral extrusion, of the wall portions advantageously avoids the leakage of prior-art sheaths that use a split in the sheath to promote expandability. Prior-art C-sheaths tend to leak close to the proximal end at the manifold where the sheath is stretched the most. Also, integral construction improves the ability to torque the sheath8.

The thick wall portion62, in the illustrated embodiment ofFIG.7, has a C-shaped cross section with a first longitudinally extending end66and a second longitudinally extending end68. The ends are where the thickness of the thick wall portion62starts to narrow to thin portion64on the cross-section. That transition extends longitudinally in the direction of the axis of the sheath8, such that the thick wall portion62forms an elongate C-shaped channel.

From those ends66,68of the thick wall portion62extends the thin wall portion64and together they define a tubular shape. Extending longitudinally in that tubular shape is the central lumen38.FIG.7, in particular, shows the central lumen38in its expanded diameter which is larger than the initial diameter of the elastic outer tubular layer40. For example, the inner tubular layer42has a central lumen38that is about 0.300+/−0.004 inches. The outer tubular layer40has an initial elastic lumen58of about 0.185 inches.

FIGS.8and9show the inner tubular layer42in its compressed or folded condition, folded up and fit into the initial elastic lumen58of the outer tubular layer. In the compressed condition, the elastic outer tubular layer40urges the first longitudinally extending end66under the second longitudinally extending end68of the inner tubular layer42. This positions the thin wall portion64between the first and second longitudinally extending ends66,68.

FIG.10shows a side view of an implant moving through sheath8. During passage of an implant through the central lumen38, the tubular wall structure34takes on a locally expanded condition corresponding to the length and geometry of the implant12. In the expanded condition, the first and second longitudinally extending ends66,68radially expand apart, against the urging of the elastic outer tubular layer40by passage of the implant12, into a non-overlapping condition with the thin wall portion64extending therebetween to form the expanded lumen, as inFIG.7. After passage of the implant12, the inner tubular layer42is urged by the outer elastic tubular layer40into the compressed condition shown inFIGS.8and9. With this configuration, a 14 French sheath8allows passage of a 29 mm transcatheter heart valve, such as the Sapien XT and Sapien 3 transcatheter heart valves available from Edwards Lifesciences.

As another option, the inner tubular layer42may be adhered along one or more longitudinally extending portions of the outer tubular layer40. Adhesion may be by heat fusion between the two layers or adhesive bonding, for example. As shown inFIG.9, the longitudinally extending portion can be a strip70where the outer surface of the inner tubular layer42is bonded or otherwise adhered to the inner surface of the outer tubular layer40. Preferably, the strip70is positioned opposite the thin wall portion64to be away from, and not affect, the fold of the inner tubular layer42. Inhibiting folding would also raise the push force for passage of the implant12. Another implementation may include a second thin bonding strip70or line. Although the thickness of the strip70can vary, preferably it is relatively narrow to reduce its inhibition of expansion of the two layers and any increases in pushing force. Use of a narrow bonding line between the layers40,42prevents free rotation of the layers with respect to each other while minimizing the effect on push force.

In another embodiment, as shown inFIGS.11-15, the distal tip24of sheath tubular wall structure34can be a sealed tip to mitigate blood intrusion and/or facilitate expansion at the distal end of travel of the implant12. In one aspect, a distal portion of the tubular wall structure34may be reflowed to adhere the inner and outer layers40,42, as shown inFIG.11. In particular, the two layers40,42are urged into their fully expanded (unfolded condition) and then reflowed to bind the outer surface of the inner tubular layer42to the inner surface of the outer tubular layer40. Then, the reflowed portion is returned to the compressed or folded configuration and compressed under a heat shrink layer74to set the fold. The heat shrink layer74is then removed. Thus, when the distal end of the wall structure34folds, the outer tubular layer40is also folded, as shown inFIGS.14and15. Sealing the tip stops blood from getting between the two layers40,42at the distal end of the sheath8while maintaining the highly expandable performance of the tubular wall structure34.

The reflowed outer tubular layer40may have added thereto a radiopaque ring72. The radiopaque ring72can be adhered outside (such as by heat shrinking) and around the reflowed, folded distal portion of the outer tubular layer40. The ring72may be applied (such as by reflowing) outside the outer tubular layer40(FIG.13) or inside the outer tubular layer40(FIG.12). The ring72is preferably constructed of a highly elastic polymer to allow expansion and facilitate urging the tip back into a folded configuration.

Advantageously, the outer tubular layer40and inner tubular layer42are both seamless, which stops blood leakage into the sheath8. The seamless construction of the inner tubular layer42eliminates the ends of a conventional C-sheath. Elimination of the cut in the C-sheath by addition of thin portion64improves torque performance. Also, both layers are easily manufactured by an extrusion process. The elastic outer tubular layer40has an elastic material that is similar to or the same as most soft tips, making their attachment much easier.

As shown inFIGS.17-20, other embodiments of the sheath8may include a conventional C-shaped inner tubular layer42surrounded by an elastic outer tubular layer40employing longitudinal rods60. (FIGS.17-20may also use other types of inner tubular layer42, such as the integrally formed ones disclosed herein.)FIG.17shows use of seven longitudinal rods equally spaced from each other about the interior surface of the outer tubular layer40with the exception that a rod is missing from a portion adjacent a split in the inner tubular layer42. This gap facilitates distraction and return of the free edges of the C-shaped inner tubular layer42.FIG.18shows a similar arrangement but with the eighth longitudinal rod60present. But the rod is somewhat offset from the location of the free edges of the inner tubular layer42. Furthermore, the rods ofFIG.18protrude outward from the outer surface of the outer tubular layer40to lower friction between the sheath and, for example, a body lumen or an additional outer delivery sheath.

FIG.19shows another embodiment wherein rods are embedded in the outer tubular layer40and extend from the inside and outside surfaces thereof in alternation. This can lower friction from advancement of the sheath8wherein, for example, the outer surface of the layer40touches a body lumen or additional outer delivery sheath.FIG.20shows another embodiment wherein the inner tubular layer42also includes a plurality of longitudinal rods60that facilitate, for example, easy passage of the implant12.

The outer tubular layer40in the configurations ofFIGS.17-20still can have a highly elastic, thin structure to fit over the conventional C-sheath inner tubular layer42. As the outer tubular layer40is not adhered to the inner tubular layer42, there is free movement between the sleeve and the delivery catheter10. The outer tubular layer40is also seamless to guard against blood leakage. The sheath8is stretched evenly along all segments in a radial direction—reducing the risk of tearing or fracture. And, the elastic outer tubular layer40will urge the C-shaped sheath back into the reduced profile configuration. During construction, the inner layer42is easily fitted inside the outer layer40without flattening or heat wrapping. Implementations may include a large number of longitudinal rods60—even 100 or more depending upon their cross-sectional size. The longitudinal rods60may include microstructure patterns that further reduce friction.

FIGS.21and22show yet another embodiment of the sheath8including a segmented outer tubular layer40having longitudinal rods60that may be employed with or without an inner tubular layer42. As shown inFIG.21, the outer tubular layer40has elongate cuts or grooves that form elongate segments76extending axially along inner surface. Formed or mounted along the grooves are the longitudinal rods60. The longitudinal rods60are shown inFIG.21to have curved or arc-shaped top surfaces that reduce friction for passing implants12. The longitudinal rods60are comprised of relatively high stiffness materials such as HDPE, fluropolymer and PTFE. The outer tubular layer40can be constructed of highly elastic materials with a low tensile set (TPE, SBR, silicone, etc.) to facilitate recovery after expansion. When used without an inner tubular layer42, the outer tubular layer40can have additionally lowered expansion force—especially because the higher strength material (the rods) are not connected in the radial direction. Other variations may include changing the number and shape of the rods60, incorporation of a tie layer or undercut/bard to strengthen the connection of the rods to the outer layer40and adding sections of stiff material to the outside of the outer layer for improved stiffness and pushability. A slip additive may be applied to the surfaces to increase lubricity.FIG.22shows the bulge in the sheath8as the implant12passes therethrough.

FIGS.23-25show another embodiment wherein a distal end of the tubular wall structure34can have a flared portion78. The flared shape of the flared portion78helps to reduce snags or interference during retrieval experienced with conventional sheaths during retrieval of medical devices. The flared portion78is folded or wrapped around the tapered distal end of an introducer80to maintain a low profile for advancement, as shown inFIGS.23and25. The number and size of the folds may vary depending upon the size and material type of the tubular wall structure34. For example,FIG.25shows three folds in a cross-sectional view. After the distal end of the sheath8is in position, the introducer80is removed. Then, the sheath8is ready to receive the delivery catheter10and implant12. When the implant12reaches the flared portion78the folds then break and expand into the flared configuration, as shown inFIG.24. The flared portion78remains in this flared configuration for possible retrieval of the implant12.

FIGS.26-29show another embodiment of the sheath8. The sheath8includes the tubular wall structure34that extends from the proximal end (as shown in cross-section inFIG.27) to the distal end (FIGS.28and29). Generally, the tubular wall structure34includes inner tubular layer42, inner tip layer81, strain relief tubular layer82, outer tip layer84and the elastic outer tubular layer40.

As can be seen the tubular wall structure34has different layers depending up on the axial position. The wall structure34includes a strain relief tubular layer82that terminates about ⅔ of the way from the proximal end, as shown inFIG.27. The strain relief layer82is preferable comprised of a relatively stiff material, such as HDPE, that can withstand the strains of the proximal end of the sheath8where it is joined to the hub and20and other components for accepting initial insertion of the delivery apparatus10. It terminates short of the distal end of the sheath8to facilitate a greater flexibility and lower profile of the distal end of the sheath8.

Extending past the strain relief tubular layer82the tubular wall structure34drops down to two layers, the inner tubular layer42and elastic outer tubular layer40. On the proximal-most end of the portion of the sheath8shown inFIG.27, the inner tubular layer splits (in cross-section) into its thick wall portion62and thin wall portion64in the folded over configuration.

At the distal end, as shown inFIGS.28and29, the sheath8includes tip structure (including inner tip layer81an outer tip layer84) configured to taper the wall structure34and seal the free end of the layers against blood or fluid invasion. Generally, these components build up the diameter of a length of the wall structure34with some additional layers including stiffening layers, and then tapers out and over the distal free end of the inner tubular layer42.

The inner tubular layer42is similar to that described above. It includes the thin wall portion64that is configured to fold over into the folded configuration back onto the thick wall portion62. Also, the elastic outer tubular layer40restrains the inner tubular layer42against expansion. But, the elasticity of the outer tubular layer40can also be overcome to allow the inner tubular layer to at least partially unfold into a wider central lumen38for passage of the implant12or other device.

As shown inFIG.28, the inner tip layer81extends only a short axial length. In particular, the inner tip layer81extends around and past the distal-most end of the foldable inner tubular layer42, tapering into smaller diameter free end after extending distally past the free end of the foldable inner tubular layer. As shown in the cross-section orthogonal to the long axis of the sheath8ofFIG.29, the inner tip layer81has a C-shaped cross-section. (The top of the C-shape is enlarged somewhat to account for the overlapping layers of the wall structure34—so that the free longitudinal edges are radially spaced apart to form a gap.) The C-shaped cross-section allows the free longitudinal edges of the inner tip layer81to spread apart during unfolding of the inner tubular layer42. Advantageously, the inner tubular layer42has a relatively stiff material construction smoothing, stiffening and tapering the distal end of the sheath8as well as providing some protection for the free end of the inner tubular layer42. The inner tip layer81also advantageously extends over the distal end of the inner tubular layer42, thereby sealing the thick and thin wall portions62,64against blood and fluid invasion.

The outer tip layer84extends over and is adhered to the inner tip layer81and a distal portion of the inner tubular layer42. The outer tip layer84covers the proximal edge of the inner tip layer81, sealing it against the inner tubular layer42. The outer tip layer84is of a relatively bendable material and, where it is directly adhered to the thin wall portion64, can be folded over onto itself as shown inFIG.28. Advantageously, then, the outer tip layer84tracks the unfolding of the thick and thin wall portions62,64to continue to seal the inner tip81to the inner tubular layer42. Notably, as the outer tip layer84unfolds the free longitudinal edges of the C-shaped inner tip layer81can come apart for coordinated lumen expansion of the sheath8. But, also, at the same time the stiffness of the inner tip layer81and extra reinforcement of the outer tip layer84help to maintain tip stiffness and stability.

The elastic outer tubular layer40extends all the way to the distal end of the sheath8, including over the distal end of the outer tip layer84. In addition, the inside of the elastic outer tubular layer includes rods60extending axially and reducing unfolding resistance by lowering surface area and increasing lubricity.

The sheath8may also include a radiopaque marker band or layer portion86that provides an orientation and depth indication under radioscopy during implantation or other medical procedures.

FIGS.30through38show a method of assembling a stiffened and sealed tip for another embodiment of the sheath8.FIGS.30-38show varying views of the same sheath8as it undergoes the method of assembly.FIGS.30and31show the inner tubular layer42(to the right) in the unfolded configuration. An additional tubular layer92(such as a strain relief or elastic layer) (to the left) extends over the inner tubular layer42but stops short of the free end of the inner tubular layer.FIG.31shows a portion of the radiopaque marker86attached to the inner tubular layer42.

FIG.32shows the inner tubular layer42with a window or v-shaped notch90cut into its free end to allow for tip expansion. The v-shaped notch90also facilitates retrieval of an implant.FIG.32also shows the C-shaped inner tip layer81extended around an outside of the inner tubular layer.FIG.33shows a second notch90on the opposite side of the inner tubular layer42. Also inFIG.33, the distal tip of the partially constructed sheath8is extended over a mandrel94to facilitate folding and attachment of other layers.

FIG.34shows formation of a proximal hemostasis seal by application of a proximal sealing layer96that extends around a distal free end of the additional tubular layer92and over and past the distal end of the emerging inner tubular layer42. In the embodiment shown inFIG.34, the proximal sealing layer96is transparent such that the v-shaped notch90is visible from underneath the sealing layer96. A proximal section98of the sealing layer96is heat treated to seal the transition between the additional tubular layer92and the inner tubular layer42, which in some embodiments can give proximal section98a glossier appearance than the remainder of sealing layer96. The proximal section98blocks blood and other fluids from entering between the two layers42,92.

FIG.35shows the layers42,92and96being folded over onto themselves.FIG.36shows the elastic outer tubular layer40or jacket with rods60being unrolled over the now folded layers42,92and96.FIG.37shows the outer tubular layer40itself slightly folded at the distal end and having applied thereover a distal sealing layer100. The excess of the free end of the proximal sealing layer96extending past the distal sealing layer100is cut away. The distal sealing layer advantageously urges the distal free end of the layers40,42and96into a tapered configuration and provides a rounded distal end for the tubular wall structure34that facilitates insertion and advancement over the guidewire.

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

FIG.39shows the delivery sheath3′ of another embodiment of the present invention with the capsule13′ carrying a stent-mounted heart valve or other prosthetic implant5′ passing through the sheath's lumen32′. (For example, the implant can be a 29 mm stent-mounted prosthetic heart valve.) The capsule13′ is passing in a proximal to distal direction. As used herein, “distal” (marked “D” inFIG.39), means towards the implantation site, and “proximal” (marked “P” inFIG.39) means away from the implantation site. The delivery sheath3′ can comprise a transparent or semi-transparent material through which can be seen the capsule13′. Generally, the sheath ofFIGS.39and40exhibits the ability to temporarily expand for passage of an implant5′ and then return back to its normal diameter afterwards. Also, the sheath3′ can include multiple rods50′, that can be seen through the sheath, and that facilitate lower friction passage of the capsule13′.

FIG.40shows a cross section of the delivery sheath3′ including a stiff wall portion52′, an elastic wall portion54′ and the rods50′. The stiff wall portion52′ has a partial circular, or arc-shaped, or C-shaped cross-section with a consistent wall thickness within the cross-section. The C-shape of the stiff wall portion has a pair of edges56′ that extend between the inner and outer surfaces of the stiff wall portion52′. Perpendicular to the cross-section, the two edges extend generally along the length of the stiff wall portion52′ and in the direction of, and parallel to, the elongate axis of the delivery sheath3′.

FIG.40shows three of the rods50′ embedded into the elastic wall portion54′ and extending into the lumen32′ of the sheath3′. The rods50′ are elongate structures with extruded cross sections—such as a cylindrical shape with a circular cross-section—that extend along the longitudinal axis of the sheath3′. The rods50′ ofFIG.40are equally spaced from each other in a circumferential direction between the edges56′ of the C-shaped stiff wall portion52′. Advantageously, the spacing of the rods50′ can increase, as shown inFIG.39, during passage of the capsule13′ with stretching of the elastic wall portion54′. Thus the rods can provide some additional stiffness and reduce the surface area and friction that would otherwise be present between the elastic wall portion and the passing implant or capsule without much impact on the expandability of the sheath. As can be seen, at least about half of the cross-section of the rods50′ extends into the lumen32′.

Embodiments disclosed herein can be employed in combinations with each other to create sheaths with varying characteristics.FIG.41shows combination of two single-layer tubes nested into each other. Each of the single layer tubes includes a stiff wall portion52′ having a C-shape and an elastic wall portion54′ to close the C-shape around lumen32′. Each single layer tube also includes rods50′ in a similar configuration to the embodiment ofFIG.40. One of the single layer tubes has a smaller diameter and fits within the lumen32′ of the other tube. The advantage of this combination is a more balanced distribution of elastic wall portions54′ on both sides of the tube which in turns distributes the strains of expansion. The other embodiments disclosed herein can be nested within each other to adjust expansion resistance and distribution.

FIGS.42-45illustrate section views of various embodiments of unexpanded sheaths66′ according to the present disclosure. The sheath66′ includes a split outer polymeric tubular layer70′ having a longitudinal cut76′ through the thickness of the outer polymeric tubular layer70′ such that the outer polymeric tubular layer70′ comprises a first portion78′ and a second portion80′ separable from one another along the cut76′. An expandable inner polymeric layer68′ is associated with an inner surface82′ of the outer polymeric tubular layer70′, and a portion of the inner polymeric layer68′ extends through a gap created by the cut76′ and can be compressed between the first and second portions78′,80′ of the outer polymeric tubular layer70′. Upon expansion of the sheath66′, first and second portions78′,80′ of the outer polymeric tubular layer70′ have separated from one another, and the inner polymeric layer68′ is expanded to a substantially cylindrical tube. In some embodiments, two or more longitudinal cuts76′ may be provided through the thickness of the outer polymeric tubular layer70′. In such embodiments, a portion of the inner polymeric layer68′ may extend through each of the longitudinal cuts76′ provided in the outer polymeric tubular layer70′.

Preferably, the inner polymeric layer68′ comprises one or more materials that are elastic and amenable to folding and/or pleating. For example,FIGS.42-45illustrate an inner polymeric layer68′ with folded regions85′. As seen inFIGS.42-45, the sheath66′ can be provided with one or more folded regions85′. Such folded regions85′ can be provided along a radial direction and substantially conform to the circumference of the outer polymeric tubular layer70′. At least a portion of the folded regions85′ can be positioned adjacent the outer surface83′ of the outer polymeric tubular layer70′. Additionally, as shown inFIGS.42and45, at least a portion of the folded region or regions85′ can be overlapped by an outer covering, such as outer polymeric covering81′. The outer polymeric covering81′ can be adjacent at least a portion of the outer surface83′ of the outer polymeric tubular layer70′. The outer polymeric covering81′ serves to at least partially contain the folded regions85′ of the inner polymeric layer68′, and can also prevent the folded regions85′ from separating from the outer polymeric tubular layer70′ when, for example, the sheath66′ undergoes bending. In some embodiments, the outer polymeric covering81′ can be at least partially adhered to the outer surface83′ of the outer polymeric tubular layer70′. The outer polymeric covering81′ can also increase the stiffness and/or durability of the sheath66′. Additionally, as shown inFIGS.42and45, the outer polymeric covering81′ may not entirely overlap the circumference of the sheath66′. For example, the outer polymeric covering81′ may be provided with first and second ends, where the ends do not contact one another. In these embodiments, only a portion of the folded region85′ of the inner polymeric layer68′ is overlapped by the outer polymeric covering81′.

In embodiments having a plurality of folded regions85′, the regions can be equally displaced from each other around the circumference of the outer polymeric tubular layer70′. Alternatively, the folded regions can be off-center, different sizes, and/or randomly spaced apart from each other. While portions of the inner polymeric layer68′ and the outer tubular layer70′ can be adhered or otherwise coupled to one another, the folded regions85′ preferably are not adhered or coupled to the outer tubular layer70′. For example, adhesion between the inner polymeric layer68′ and the outer tubular layer70′ can be highest in areas of minimal expansion.