Patent Publication Number: US-11389571-B2

Title: Multilayered catheter shaft containing polyvinylidene fluoride polymers

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. provisional application No. 61/792,644, filed 15 Mar. 2013, which is hereby incorporated by reference as though fully set forth herein. 
    
    
     BACKGROUND 
     a. Technical Field 
     The instant disclosure relates to catheters. In particular, the instant disclosure relates to catheter shafts which in use are guided within a human or animal so that a distal tip can be located at a remote internal location where medical equipment can be positioned or treatment fluids delivered. 
     b. Background Art 
     It is well known that catheters can be used to perform a growing number of procedures. Catheters can be used for performance of diagnostic, therapeutic, and ablative procedures, for example. Catheters include a shaft (tubular body) mounted on a handle which can guide the shaft within the vasculature system of a patient to reach a remote target site of the human anatomy where the procedure will be performed. The shaft of the catheter includes a central lumen through which one or more devices or treatment fluids can be guided to the remote target site. Such shafts need to have various physical and chemical characteristics. For instance, they need to be sufficiently flexible and durable to be reliably guided within the human anatomy or vascular system; they need to have an internal surface lubricity that facilitates the passage of other medical devices along their central lumen; they need to have a surface lubricity that allows for maneuvering the catheter within the vasculature of the patient; they should be externally hydrophobic, especially at their distal ends, to resist absorption of fluids and thus prevent shaft performance changes during medical procedures; and they should be chemically compatible with medical adhesives used to attach sensors and other monitoring devices to their outer surfaces. 
     The foregoing discussion is intended only to illustrate the present field and should not be taken as a disavowal of claim scope. 
     SUMMARY 
     In various embodiments, a tubular body is provided. In at least one embodiment, the tubular body can comprise three radially positioned polymeric layers. In these embodiments, at least two of the three layers can include chemically dissimilar polymers and at least one of the three layers can include functionalized polyvinylidene fluoride (PVDF). 
     In various embodiments, a catheter shaft is provided. In at least one embodiment, the catheter shaft can include an inner polymeric layer, a middle polymeric layer bonded to the inner polymeric layer, and an outer polymeric layer bonded to the middle polymeric layer. In these embodiments, one of the layers can include a functionalized PVDF. 
     In various embodiments, the catheter shaft can include a proximal segment, a transitional segment, and a distal segment. In at least one embodiment, each of the segments have an inner polymeric layer, a middle polymeric layer, and an outer polymeric layer. In various embodiments, at least one of the layers in the transitional segment can be formed of functionalized PVDF and at least one of the layers in the distal segment can be formed of functionalized PVDF. 
     The foregoing and other aspects, features, utilities, and advantages of the present disclosure will be apparent from reading the following description and claims, and from reviewing the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a catheter, according to a non-limiting embodiment. 
         FIG. 2  is an isometric view of a section of a catheter shaft according to a first non-limiting embodiment. 
         FIG. 3  is an isometric view of a section of a catheter shaft according to a second non-limiting embodiment. 
         FIG. 4  is an isometric view of a section of a catheter shaft according to a third non-limiting embodiment. 
         FIG. 5  is a partial cross-sectional view of a section of a catheter shaft according to a fourth non-limiting embodiment. 
         FIG. 6  is a partial cross-sectional view of a section of a catheter shaft according to a fifth non-limiting embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     It is well known to form catheters from multiple layers of polymeric materials which have been extruded and melt bonded together. With consideration of end-use performances of catheters, both polar and nonpolar polymers may have to be utilized. Typical polar polymers include polyamides, poly(ether block amides) copolymers (PEBA), thermoplastic polyurethanes (TPU), polyesters, poly(ester-co-ether) block polymers (PEE), etc., as these polymers display synergistically balanced mechanical properties for a catheter shaft and exhibit good chemical affinities with medical adhesives. On the other hand, nonpolar fluoropolymers such as polytetrafluoro-ethylene (PTFE), ethylene-tetrafluoroethylene-hexafluoropropylene terpolymer (EFEP), fluorinated ethylene-propylene copolymer (FEP), poly(vinylidene fluoride) (PVDF) etc., are also utilized due to their excellent surface lubricity and hydrophobicity as well as exceptional chemical resistance against body fluids. Those nonpolar fluoropolymers, in particular PTFE, are commonly used as catheter liner materials to facilitate the delivery of medical devices through the central lumens. 
     However, multilayered catheter shafts made of dissimilar polymers with differing chemical structures and/or molecular polarities may not have reliable layer-to-layer polymer adhesion, and layer delamination can be a risk. Tie layers which exhibit good chemical affinities with chemically dissimilar polymer layers may have to be employed. Alternatively, the bonding surfaces of the dissimilar polymeric layers may be pretreated using various physical and chemical techniques (e.g., plasma or corona treatment, chemical etching, etc.) in order to improve layer-to-layer polymer adhesions and prevent the occurrence of layer delamination. However, using tie layers or polymer surface treatment would result in increased manufacturing expenses and limit flexibility of catheter structural designs. 
     It is well known in the polymer industry that some selected fluoropolymers such as EFEP and PVDF can be polymerized or purposely grafted with reactive functional groups (such as amine, acrylics, carbonate, epoxides, carboxylic acids, maleic anhydride, etc.) to introduce molecular binding affinity with other polar polymers without compromising their inherent surface lubricity and chemical resistance, as required by catheter designs. Guo et al. (U.S. Appln. Pub. 2012/0172840 A1), which is incorporated herein by reference, discloses various hydrophobic catheters and compositions in which a hydrophobic and lubricious EFEP copolymer with terminal carbonate functional groups is utilized with various polar polymers such as PEBA, which is hereby incorporated by reference as though fully set forth herein. In the present disclosure, PVDF with purposely grafted reactive functional groups, such as maleic anhydride, is utilized to make various high-performance catheter shafts with synergistic consideration of not only surface lubricity and chemical resistance against body fluids, but also mechanical properties of PVDF polymers. 
     A reactive PVDF polymer with grafted functional groups such as maleic anhydride in place of nonpolar, nonreactive PVDF homopolymers can be used when desiring a direct bonding to an adjacent polar polymer. At the interface of bonding, the reactive functional groups of the functionalized PVDF polymer would exhibit some chemical affinity via intermolecular interactions (e.g., dispersion, dipole-dipole forces and hydrogen bonding), and even form some permanent covalent bonds with terminal and mid-chain functional groups of polar polymers, leading to a reliable polymer adhesion. In the literature, there are numerous patents and applications teaching how to use functionalized or grafted PVDF polymers to enhance the polymer adhesions between nonpolar PVDF and polar polymers primarily polyamides or nylons. U.S. Appln. Pub. 2009/0188578, which is incorporated herein by reference, discloses multilayer tubes for transferring corrosive chemical fluids which are in direct contact with a functionalized PVDF layer. Patents EP 558373, EP 696301, EP 726926 and EP 740754 disclose various multilayer tubes for petrol or gasoline. U.S. Pat. No. 8,216,498, which is incorporated herein by reference, utilizes a grafted PVDF polymer with a polar polymer to coextrude catheter shafts. However, this patent only discloses a functionalized PVDF layer directly bonded to a single adjacent polar polymer layer (bilayer), and the resultant bilayer catheter shafts may not display all the desired mechanical performances and external hydrophobicity against body fluids, which are highly desired for a versatile, high performance catheter. 
       FIG. 1  depicts a catheter  10  for use in connection with a number of diagnostic and therapeutic procedures performed, for example, within a human heart. For clarity and brevity purposes, the description herein will be directed primarily to a medical device, such as catheter  10 , that comprises a catheter shaft, such as a tubular shaft  11 , for use in cardiac applications. It will be appreciated by those having ordinary skill in the art, however, that the description below may be applicable to medical devices and apparatuses other than catheters, and for catheters, medical devices, and apparatuses used in connection with applications other than cardiac applications. Accordingly, apparatuses and medical devices other than catheters and apparatuses, medical devices, and catheters for use in applications other than cardiac applications remain within the spirit and scope of the present disclosure. As used herein, a “catheter” is defined as an elongated structure that can be inserted into and/or through a body cavity, duct, and/or vessel. Additionally, as used herein, a “catheter” means an elongated structure that can be inserted into and/or through a body cavity, duct, and/or vessel. Accordingly, the catheter can be sized and configured to be inserted into a patient&#39;s body. In at least one embodiment, a catheter may be hollow and/or define a lumen therethrough for passing another medical device, such as a guidewire or another catheter, for example. However, in various embodiments, a catheter may be closed at least at its distal end. 
     As illustrated in  FIG. 1 , a catheter  10  includes a tubular shaft  11  and a handle  12 . The shaft  11  can be configured to be at least partially inserted into and/or through a body passage or another anatomic structure, such as a human patient&#39;s vasculature, including a blood vessel. The handle  12  can include an internal manipulation mechanism (not shown) for manipulating a distal tip  13  of the shaft  11 . The shaft  11  can be mounted at its proximal end  13  in the handle  12  such that manual manipulation of the handle  12  via the internal manipulation mechanism will direct the movement of the shaft  11  and/or distal tip  13  inside a person of interest. The shaft  11  is formed of either melt- or adhesive-bonded polymeric layers which are radially positioned relative to one another, and which define a central lumen for the passage of the internal manipulation device or other medical devices (not shown) or the flow of treatment liquids to the distal tip  13  of the shaft  11  that is in contact with the anatomical target being inspected or treated. 
       FIG. 2  depicts an isometric view of a section of a catheter shaft  11   A  according to a first non-limiting embodiment. In some embodiments, the shaft  11   A  can include three radially positioned polymeric layers that define a lumen  19   A . For example, the shaft  11   A  can include an inner polymeric layer  16   A , a middle polymeric layer  17   A , and an outer polymeric layer  18   A . The middle polymeric layer  17   A  can be bonded to the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be bonded to the middle polymeric layer  17   A . At least two of the three polymeric layers can include chemically dissimilar polymers and at least one of the three polymeric layers can include a functionalized polyvinylidene fluoride (PVDF). In addition to the functionalized PVDF, the polymers making up the at least two of the three polymeric layers can be chosen from polar polymers, PVDF homopolymers, and PVDF copolymers. 
     The functionalized PVDF can be a PVDF homopolymer or copolymer grafted with at least one functional monomer having at least one functional group such as a carboxylic acid, carboxylic acid salt, carbonate, carboxylic acid anhydride, epoxide, carboxylic acid ester, carboxylic amide, silyl, alkoxysilane, hydroxyl, and isocyanate. Preferably, the functionalized PVDF is grafted with at least one functional monomer having at least one functional group such as maleic anhydride (commercially available from Arkema, Inc. under the trademark KYNAR ADX®) and/or glycidyl methacrylate. 
     PVDF homopolymers include repeating units of vinylidene fluoride (VDF) monomer. They are commercially available from multiple commercial resources, including KYNAR® (Arkema Inc.), Dyneon™ PVDF homopolymers (3M Dyneon Company), Solef® PVDF homopolymers (Solvay), Hylar® (Solvay), Dyflor® (Evonic Industries) etc. Preferably, the functionalized PVDF includes a PVDF homopolymer grafted with maleic anhydride. 
     According to various embodiments, PVDF copolymers may be obtained by polymerizing VDF monomer with one or two other co-monomers such as hexafluoropropylene (HFP), mono-fluoroethylene, trifluoroethylene and tetrafluoroethylene. PVDF copolymers are commercially available from multiple commercial resources, including Dyneon™ PVDF copolymers (3M Dyneon Company) Solef® PVDF copolymers (Solvay Specialty Polymers), etc. The preferred PVDF copolymers (and used in the examples) were copolymers of VDF and HFP, which are commercially available from Arkema, Inc. under the trademark (KYNAR FLEX®). In some embodiments the PVDF copolymer can be a functionalized PVDF copolymer, including a copolymer of VDF and HFP grafted with maleic anhydride. 
     Polar polymers are polymers having a polymer chain containing polar atoms such as oxygen, nitrogen, halogen atoms and sulfur, or polar groups that likely exhibit-attractive intermolecular forces (e.g., dipole-dipole forces, hydrogen bonding, etc.) to itself and other dissimilar polymers. In general, a polar polymer has a much higher surface energy than a typical nonpolar polymer like polypropylene or PVDF homopolymer. Typical polar polymers include polyamides (e.g. nylon 11, nylon 12, nylon 612, nylon 66, nylon 6, etc.), engineering thermoplastic polyurethanes, polyesters (e.g., poly(ethylene terephthalate), poly(butylene terephthalate)), polyester-based thermoplastic elastomers, polyamide-based thermoplastic elastomers, thermoplastic polyurethane elastomers, polycarbonate, functionalized polyolefins, poly(ether block amide) copolymers, etc. 
     PVDF homopolymers and copolymers are melt-processable fluoroplastics, making the polymers suitable for use in forming the shaft  11   A  because of their ability to be processed. In addition, as discussed herein, PVDF polymers offer a surface lubricity and hydrophobicity that can increase a performance of the shaft  11   A . Increased surface lubricity of the materials that form an inner surface of the shaft  11   A  that defines a guidewire lumen can facilitate movement of the guidewire therein by reducing aggregation of fibrin and plasma proteins. Additionally, increased surface lubricity of the materials that form an outer surface of the shaft  11   A  can reduce organ damage as the shaft  11   A  is passed through the patient&#39;s vasculature as well as pain felt by a patient. Increased hydrophobicity of the materials that form the inner surface and/or outer surface can aid in reducing absorption of fluids being passed through the lumen and/or contacting the outer surface of the shaft  11   A . 
     As discussed herein, nonpolar polymers can offer desirable mechanical properties, as well as affinities for medical adhesives. As such, the layered shaft  11   A  that includes a composite of nonpolar and/or polar materials in various layers can have balanced mechanical properties, as well as a desirable surface lubricity and hydrophobicity. 
     However, polar polymers such as PVDF homopolymers and PVDF copolymers can have poor adhesion to chemically dissimilar polymers. Accordingly, various embodiments of the present disclosure can increase adhesion between the chemically dissimilar polymers by including a functionalized PVDF layer in at least one of the three layers of the shaft  11   A . 
     In some embodiments, the middle polymeric layer  17   A  can be formed of functionalized PVDF and the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be chemically dissimilar polymers to one another. For example, the inner polymeric layer  16   A  can be a polar polymer (e.g., polyamide) and the outer polymeric layer  18   A  can be a nonpolar polymer (e.g., PVDF copolymer, PVDF homopolymer). Alternatively, the inner polymeric layer  16   A  can be a non-polar polymer and the outer polymeric layer  18   A  can be a polar polymer. Because the functionalized PVDF has a reactive functional group, the chemically dissimilar polymers forming the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be bonded together by the middle polymeric layer  17   A  of functionalized PVDF. 
     Alternatively, the middle polymeric layer  17   A  can be a functionalized PVDF polymer and the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be chemically similar polymers bonded to the middle polymeric layer  17   A  of functionalized PVDF polymer. In some examples, the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be nonpolar polymers, which can provide a shaft  11   A  that is flexible and has a desired hydrophobicity and lubricity within the ranges specified herein. For instance, the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be PVDF copolymers; the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be PVDF homopolymers; the inner polymeric layer  16   A  can be a PVDF homopolymer and the outer polymeric layer  18   A  can be a PVDF copolymer; or the inner polymeric layer  16   A  can be a PVDF copolymer and the outer polymeric layer  18   A  can be a PVDF homopolymer. 
     In some embodiments, the functionalized PVDF can be used to form the inner polymeric layer  16   A  and/or the outer polymeric layer  18   A . Forming the inner polymeric layer  16   A  and/or the outer polymeric layer  18   A  with the functionalized PVDF can facilitate bonding of subassemblies to the inner polymeric layer  16   A  and/or the outer polymeric layer  18   A . For instance, in reference to  FIG. 1 , a tip (e.g., electrode tip) can be bonded to the distal tip  13  of the shaft  11 . Bonding to the inner polymeric layer  16   A  and/or the outer polymeric layer  18   A  can be performed with a UV curing epoxy, such as a diacrylate adhesive. In some examples, the inner polymeric layer  16   A  and the outer polymeric layer  18   A  can be formed from PVDF and the middle polymeric layer  17   A  can be formed from a polar polymer (e.g., nylon). As such, while subassemblies can be bonded to the inner polymeric layer  16   A  and/or outer polymeric layer  18   A  of functionalized PVDF, the middle polymeric layer  17   A  of polar polymer can also provide the shaft  11   A  with desired mechanical properties. 
     In some embodiments, when the inner polymeric layer  16   A  is made from functionalized PVDF, the middle polymeric layer  17   A  and/or the outer polymeric layer  18   A  can be formed from a PVDF copolymer and/or a PVDF homopolymer, in some examples. Alternatively, when the outer polymeric layer  18   A  is formed from functionalized PVDF, the middle polymeric layer  17   A  and/or the inner polymeric layer  16   A  can be made from a PVDF copolymer and/or a PVDF homopolymer, in some examples. 
     In some embodiments, when the inner polymeric layer  16   A  is made from functionalized PVDF, the middle polymeric layer  17   A  and/or the outer polymeric layer  18   A  can be formed from polar polymers, in some examples. Alternatively, when the outer polymeric layer  18   A  is formed from functionalized PVDF, the middle polymeric layer  17   A  and/or the inner polymeric layer  16   A  can be made from polar polymers, in some examples. 
       FIG. 3  depicts an isometric view of a section of a catheter shaft  11   B  according to a second non-limiting embodiment. The shaft  11   B  includes an inner polymeric layer  16   B , middle polymeric layer  17   B , and outer polymeric layer  18   B  that define a lumen  19   B . The inner polymeric layer  16   B , the middle polymeric layer  17   B , and the outer polymeric layer  18   B  can be formed from the same combination of polymers as discussed in relation to shaft  11   A , in  FIG. 2 . In addition, a metal wire braid layer  22   A  can be embedded at or near (e.g., proximate to) an interface of the middle polymeric layer  17   B  and outer polymeric layer  18   B . In some embodiments, the metal wire braid layer  22   A  can provide additional hoop strength to the shaft  11   B , while still permitting the shaft  11   B  to be flexible and/or compliant. The additional hoop strength can result in an increased kink resistance of the shaft  11   B . 
     Owing to a braid pattern of the metal wire braid layer  22   A , openings  23   A  may be defined within the metal wire braid layer  22   A . The outer polymeric layer  18   B  and the middle polymeric layer  17   B  can, in some instances, bind with one another through the openings  23   A . As such, the outer polymeric layer  18   B  and the inner polymeric layer  17   B  can form a cohesive bond with one another, even though the metal wire braid layer  22   A  is located at an interface of the two layers. 
     Alternatively, the metal wire braid layer  22   A  can be wholly and/or partly contained within the outer polymeric layer  18   B  and/or the middle polymeric layer  17   B . In some embodiments, it may be desirable to contain the metal wire braid layer  22   A  wholly within the middle polymeric layer  17   B . Containing the metal wire braid layer  22   A  wholly within the middle polymeric layer  17   B  can prevent wires associated with the metal wire braid layer  22   A  from protruding from the inner polymeric layer  17   B  and/or outer polymeric layer  18   B . 
       FIG. 4  depicts an isometric view of a section of a shaft  11   C  according to a third non-limiting embodiment. The shaft  11   C  includes an inner polymeric layer  16   C , middle polymeric layer  17   C , and outer polymeric layer  18   C  that define a lumen  19   C . The inner polymeric layer  16   C , the middle polymeric layer  17   C , and the outer polymeric layer  18   C  can be formed from the same combination of polymers as discussed in relation to shaft  11   A , in  FIG. 2 . A metal wire braid layer  22   B  can be embedded at or near an interface of the inner polymeric layer  16   C  and the middle polymeric layer  17   C . As discussed in relation to  FIG. 3 , the metal wire braid layer  22   B  can provide additional hoop strength to the shaft  11   C , while still permitting the shaft  11   C  to be flexible and/or compliant. Additionally, as discussed in relation to  FIG. 3 , the metal wire braid layer  22   B  can be located at an interface of the two layers and/or can be wholly contained within the middle polymeric layer  17   C  to prevent protrusion of wires associated with the metal braid layer  22   B . 
     In some embodiments, a polymeric layer adjacent to the metal wire braid layer, for example the inner polymeric layer  16   C  and middle polymeric layer  17   C  in  FIG. 4  and the outer polymeric layer  18   B  and middle polymeric layer  17   B  in  FIG. 3  can form a bond with the metal wire braid layer when the adjacent polymeric layer is formed of functionalized PVDF. In an example, the functionalized PVDF can have a reactive functional group that can bond with metal. As such, the polymeric layer that is adjacent to the metal wire braid layer  22   B  and/or contains the metal wire braid layer  22   B  can be formed of functionalized PVDF, according to some embodiments of the present disclosure. Forming the polymeric layer adjacent to the metal wire braid layer  22   B  and/or a polymeric layer that contains the metal wire braid layer  22   B  out of functionalized PVDF can reduce a chance of the shaft delaminating. For example, since the reactive functional group of the functionalized PVDF can bond to the metal, a reduced chance of delamination may be present as opposed to when other types of polymers (e.g., polyamides) are located adjacent to and/or contain the metal wire braid layer  22   B . 
     In other embodiments (not specifically depicted) the catheter shaft  11   C  can include metal wire braid layers between both the inner polymeric layer  16   C  and middle polymeric layer  17   C  and between the middle polymeric layer  17   C  and outer polymeric layer  18   C . Alternatively, the metal wire braid layers can be omitted, for example, in  FIG. 2 . 
     As discussed herein, in an embodiment, at least one of the inner polymeric layer  16   C , middle polymeric layer  17   C , and outer polymeric layer  18   C  is composed of functionalized PVDF and at least two of the layers are composed of chemically dissimilar polymers. In an example, the functionalized PVDF can enable bonding between layers, bonding of a subassembly to an outer and/or inner layer, and/or bonding of a metal wire braid layer. 
       FIG. 5  depicts a partial cross-sectional view of a section of a shaft  26   A  according to a fourth non-limiting embodiment. The shaft  26   A  includes a proximal segment  27   A , a transitional segment  28   A , and a distal segment  29   A . In some embodiments, each of the segments  27   A ,  28   A ,  29   A  have an inner polymeric layer  30   A ,  30   B ,  30   C  a middle polymeric layer  31   A ,  31   B ,  31   C , and an outer polymeric layer  32   A ,  32   B ,  32   C , respectively. 
     As discussed herein, it can be desirable to have different mechanical properties for different segments  27   A ,  28   A ,  29   A  of the shaft  26   A . For example, it can be desirable to have a proximal segment  27   A  with a high column strength to effectively transfer a manipulating force placed on the catheter handle (e.g., proximal segment) by a physician. In addition, it can be desirable to have a distal segment  29   A  with a good mechanical flexibility or deflectability, high surface lubricity, and hydrophobicity, etc. Accordingly, some embodiments of the present disclosure can provide for a shaft  26   A  having segments with varying mechanical properties. 
     In some embodiments, the inner polymeric layer  30   A ,  30   B ,  30   C  the middle polymeric layer  31   A ,  31   B ,  31   C , and/or the outer polymeric layer  32   A ,  32   B ,  32   C  can be formed from the same polymer. For example, the proximal segment  27   A , transitional segment  28   A , and/or the distal segment  29   A  of the middle polymeric layer  30   A ,  30   B ,  30   C  can be formed from the same polymer, giving the middle polymeric layer  30   A ,  30   B ,  30   C  uniform mechanical characteristics along a length of the shaft  26   A . Alternatively, the proximal segment  27   A , transitional segment  28   A , and/or distal segment  29   A  of the middle polymeric layer  30   A ,  30   B ,  30   C  can be made from different polymers, giving the middle polymeric layer  30   A ,  30   B ,  30   C  varying mechanical characteristics along a length of the shaft  26   A . 
     In some examples, by forming the middle polymeric layer  30   A ,  30   B ,  30   C  from different polymers (e.g., polymers with different flexibilities), a flexibility of the middle polymeric layer  30   A ,  30   B ,  30   C  can increase from the proximal segment  27   A  to the distal segment  29   A . As such, a maneuverability of the distal segment  29   A  can be increased, which can be beneficial when feeding the distal segment through vasculature of a patient to a position where a medical procedure is to be performed with the shaft  26   A . 
     In some embodiments, the inner polymeric layer  30   A , middle polymeric layer  31   A , and outer polymeric layer  32   A  of the proximal segment  27   A  can be formed from at least one type of polar polymer (e.g., polyamide). Forming each of the layers of the proximal segment  27   A  from the polar polymer can provide a high column strength to effectively transfer a manipulating force placed on the catheter handle, while at the same time reducing a materials cost associated with construction of the proximal segment  27   A . 
     In some embodiments, the inner polymeric layers  30   B ,  30   C  of the transitional segment  28   A  and the distal segment  29   A  can be formed from the at least one type of polymer. In an example, the inner polymeric layers  30   B ,  30   C  can be made of the same type of polar polymer that forms the proximal segment. As such, the inner polymeric layers  30   A ,  30   B ,  30   C  can be formed of one continuous polar polymeric layer. 
     In embodiments where the inner polymeric layer  30   A , middle polymeric layer  31   A , and outer polymeric layer  32   A  of the proximal segment  27   A  are formed from at least one type of polar polymer, a bond between the proximal segment  27   A  and the transitional segment  28   A  may not be obtained when layers of the transitional segment  28   A  are chemically dissimilar to corresponding layers of the proximal segment  27   A  (e.g., polar and non-polar polymers). As such, embodiments of the present disclosure can include a tie band, which can bond chemically dissimilar layers of the proximal segment and transitional segment, as discussed further in relation to  FIG. 6 . 
     In some embodiments, the inner polymeric layers  30   A ,  30   B ,  30   C  and/or outer polymeric layers  32   A ,  32   B ,  32   C  can be formed from functionalized PVDF. The functionalized PVDF can act as a hydrophobic barrier layer. During clinical procedures, catheter shafts may be exposed to aqueous surroundings of the vessel and human anatomy for a prolonged time, and any exposed polar polymeric materials of a catheter shaft may, as a consequence, unavoidably absorb water, which may act as a plasticizer for exposed polar polymeric shafts. Tests have shown that PEBA based catheters, for example, that do not include a hydrophobic barrier layer, may absorb water at an amount of up to 2% by weight upon immersion into saline. The moisture absorbed into the materials may act as a plasticizer, potentially leading to decreases in the catheter shaft&#39;s mechanical strength and stiffness/rigidity. As a result, such shafts could exhibit mechanical softening phenomena over time, which could lead to decreases in mechanical strength, column stiffness, pushability, torqueability, and the like. As a consequence, this softening could lead to changes in end-use performance, such as compromised catheter shaft deliverability along a vessel and poor shaft maneuverability within the target human anatomy. Moreover, any such in-procedure performance changes could affect an operating physician&#39;s perception of use. 
     The hydrophobic barrier layer described above may be useful to prevent or resist water or any aqueous medium from being absorbed by the catheter shaft. As noted above, typically, catheter shafts are made of polar polymeric materials and providing a hydrophobic barrier layer may prevent the degradation of mechanical properties that may occur where the polar polymeric materials would have previously been exposed to an aqueous environment and absorb water and/or other fluids. Therefore, providing a hydrophobic barrier layer to the exterior of a catheter shaft may help minimize or eliminate the changes in shaft deliverability and/or maneuverability during a surgical procedure. Also, providing a hydrophobic barrier layer to the interior of a catheter shaft may help minimize or eliminate the changes in shaft deliverability and/or maneuverability due to saline from an irrigation lumen, either a central lumen or one or more such lumens in the wall of a catheter, for example. 
     Some embodiments of the present disclosure can include a metal wire braid layer  33   A , as discussed in relation to  FIGS. 3 and 4 . For example, the metal wire braid layer  33   A  can be embedded proximate to an interface of the middle polymeric layers  31   A ,  31   B ,  31   C  and the outer polymeric layers  32   A ,  32   B ,  32   C , as shown in  FIG. 4 , and/or the metal wire braid layer  33   A  can be embedded proximate to an interface of the middle polymeric layers  31   A ,  31   B ,  31   C  and the inner polymeric layers  30   A ,  30   B ,  30   C . As discussed herein, the metal wire braid layer  33   A  can provide an increased kink resistance to the shaft  26   A . 
     In some embodiments, the shaft  26   A  can include a reinforcing spring  34   A  that extends along the inner polymeric layers  30   A ,  30   B ,  30   C  of the shaft  26   A . The reinforcing spring  34   A  can be located within the lumen  35   A  of the shaft  26   A  and can extend from the proximal segment  27   A  to a portion of the distal segment  29   A . For example, the spring may partially extend through the distal segment  29   A  so as to maintain a maneuverability and flexibility of the distal segment  29   A . In addition, partially extending the distal segment  29   A  through the distal segment aids in torque transfer between the proximal segment  27   A  and the distal segment  29   A , while increasing a kink resistance of the shaft  26   A  along a length of the reinforcing spring  34   A . 
     A protective shrink tube  36   A  can be placed around a distal end of the reinforcing spring  34   A , which can contain the distal end of the reinforcing spring  34   A . The protective shrink tube  36   A  can be made from functionalized PVDF, which can be bonded to the inner polymeric layer  30   B  of the transitional segment  28   A  and/or the inner polymeric layer  30   C  of the distal segment  29   A . In some embodiments, the protective shrink tube  36   A  can be placed around the distal end of the reinforcing spring  34   A  to alleviate a stress rise that can be caused by sudden changes in the internal structure of the shaft  26   A . 
       FIG. 6  depicts a partial cross-sectional view of a section of a shaft  26   B  according to a fifth non-limiting embodiment. The shaft  26   B  includes a proximal segment  27   B , tie band  40 , transitional segment  28   B , and distal segment  29   B . The shaft includes inner polymeric layers  30   D ,  39 ,  30   E ,  30   F , middle polymeric layers  31   D ,  38 ,  31   E ,  31   F , and outer polymeric layers  32   D ,  37 ,  32   E ,  32   F . Additionally, the shaft can include the metal wire braid layer  33   B , the reinforcing spring  34   B , and shrink tube  36   B . 
     As discussed herein, when a particular polymeric layer of the proximal segment  27   B  is chemically dissimilar from a corresponding polymeric layer of the transitional segment  28   B , a bond may not be obtained between the polymeric layers. As such, embodiments of the present disclosure can include a tie band  40  that consists of an outer polymeric layer  37 , middle polymeric layer  38 , and/or inner polymeric layer  39  of functionalized PVDF, depending on which corresponding polymeric layers of the transitional segment  28   B  and the proximal segment  27   B  are chemically dissimilar. 
     In some embodiments, a high hydrophobicity can be provided only for the deflectable distal segment  29   B  and transitional segment  28   B , while the lengthy proximal segment  27   B  of the catheter shaft  26   B  can be made of relatively economical polymeric materials like polyamide-based thermoplastic elastomers, thermoplastic polyurethanes, thermoplastic polyester-based elastomers, polyesters, and polyamides, etc. 
     In one embodiment, the inner polymeric layers  30   D ,  39 ,  30   E ,  30   F  can be selected from polar polymeric materials such as polyamide-based thermoplastic elastomers, thermoplastic polyurethanes, thermoplastic polyester-based elastomers, polyamides, and can extend the whole length of the catheter shaft  26   B . The middle polymeric layer  31   D  and outer polymeric layer  32   D  for the proximal segment  27   B  of the catheter shaft  26   B  can be formed from a same polymer as the inner polymeric layer  30   D , or can be formed from a polymer selected from the same family as the inner polymeric layer  30   D  with higher or lower durometer. 
     Between the proximal segment  27   B  and transition segment  28   B  of the shaft, the functionalized PVDF tie band  40  can be overlaid on the polar, inner polymeric layer  39 . The middle polymeric layer  38  of the tie band  40  can be formed from functionalized PVDF and can extend from the transitional segment  28   B  to the deflectable distal segment  29   B . In some embodiments, the outer polymer layer  37  of the tie band  40  can be formed of functionalized PVDF, while the outer polymeric layers  32   E  and  32   F  can be selected from PVDF homopolymers or copolymers having different durometers or mechanical flexibilities (such as KYNAR FLEX® 2750 and KYNAR FLEX® 2500) for the transitional segment  28   B  and distal segment  29   B  of the shaft  26   B , respectively. This can result in the distal segment  29   B  having an increased flexibility over the transitional segment  28   B . The metal wire braid layer  33   B  can extend from the proximal segment  27   B  to the transitional segment  28   B  or a portion of the deflectable distal segment  29   B . 
     In this embodiment, the functionalized PVDF tie band  40  can provide good face-to-face, axial polymer adhesions between the polar, proximal segment  27   B  and the hydrophobic, transitional segment  28   B  (or the deflectable distal segment  29   B ) of the catheter shaft  26   B . In addition, the PVDF tie band  40  also acts as a hydrophobic shut-off barrier dividing the catheter shaft  26   B  into two portions: the hygroscopic (or polar), proximal portion  27   B  and the hydrophobic (or nonpolar), portion (e.g., tie band  40 , transitional segment  28   B  and distal segment  29   B ). Moreover, within the transitional segment  28   B  and distal segment  29   B , the functionalized PVDF middle polymeric layers  31   E ,  31   F  enable sound layer-to-layer adhesions between polar inner polymeric layers  30   E ,  30   F , metal wire braid layer  33   B  and nonpolar hydrophobic outer polymeric layers  32   E ,  32   F . 
     Examples of the inner, middle and outer polymeric layers of at least portions (or segments) of a catheter shaft according to plural embodiments are as follows. 
     EXAMPLE 1 
     All Layers Include PVDF Homopolymers and Copolymers 
     A multilayered catheter shaft included an inner polymeric layer of PVDF homopolymer (KYNAR® 460), a middle polymeric layer of PVDF copolymer (KYNAR FLEX® 3120), and an outer polymeric layer of functionalized PVDF (KYNAR ADX®). The shaft exhibited good flexibility, balanced mechanical strengths, excellent internal and external surface lubricity, and high chemical resistance against body fluids or medical agents. Relatively, the outer polymeric layer of functionalized PVDF and inner polymeric layer of PVDF homopolymer provided layers with lubricities greater than that associated with a polar polymer, such as nylon. Due to the outer polymeric layer being made of functionalized PVDF, subassemblies with other functional components could be attached to the shaft using adhesive bonding techniques. If an increased kink resistance is desired, a metal wire braid layer could be included between the outer and middle polymeric layers to provide enhanced shaft strength and kink resistance. 
     EXAMPLE 2 
     All Layers Include PVDF Homopolymers and Copolymers 
     A multilayered catheter shaft included an inner polymeric layer of PVDF homopolymer (KYNAR® 460), a middle polymeric layer of functionalized PVDF (KYNAR ADX®), and an outer polymeric layer of PVDF homopolymer (KNAR® 460). The shaft displayed excellent internal and external surface lubricity and chemical resistance against body fluids and medical fluids if applicable. Relatively, the inner and outer polymeric layers of PVDF homopolymer provided layers with lubricities greater than that associated with a polar polymer, such as nylon. When a metal wire braid layer was included between inner and middle polymeric layers or between the middle and outer polymeric layers, the shaft displayed enhanced shaft strength and excellent kink resistance. 
     EXAMPLE 3 
     All Layers Include PVDF Homopolymers and Copolymers 
     A multilayered catheter shaft including an inner polymeric layer of PVDF copolymer (KYNAR FLEX® 2500), a middle polymeric layer of functionalized PVDF (KYNAR ADX®), and an outer polymeric layer of PVDF copolymer (KYNAR FLEX® 2750). The shaft was highly flexible, but displayed excellent surface lubricity and high chemical resistances against body fluids or medical agents. Relatively, the inner and outer polymeric layers of PVDF homopolymer provided layers with lubricities greater than that associated with a polar polymer, such as nylon. 
     EXAMPLE 4 
     Functionalized PVDF Inner and Outer Polymeric Layers with Metal Wire Braid Layer 
     A multilayered catheter shaft included an inner polymeric layer of functionalized PVDF (KYNAR ADX®), a middle polymer layer of nylon 12 (Rilsan AESNO or Pebax 7233/7033), and an outer polymeric layer of functionalized PVDF (KYNAR ADX®). A metal wire braid was included between the inner and middle polymeric layers, or between the middle and outer polymeric layers. It should be noted that some polar polymers contain reactive functional groups as their terminal groups (amido, epoxy, hydroxyl, isocyanate, and urethane, etc.) and thus can adhere to functionalized PVDF (copolymer) grafted with maleic anhydride monomers, when they are melt coextruded. Polar polymers provide a wide spectrum of mechanical performance characteristics in catheter shafts, while the PVDF polymers provide excellent water resistance and surface lubricity. The outer functionalized PVDF layer enabled adhesive bonding thereto of typical subassemblies, whereas the inner functionalized PVDF layer provided excellent surface lubricity for the central lumens of the shaft. Relatively, the inner and outer polymeric layers of functionalized PVDF provided layers with lubricities greater than that associated with a polar polymer, such as nylon. 
     EXAMPLE 5 
     Functionalized PVDF Middle Polymeric Layer and PVDF Copolymer Outer Polymeric Layer with Metal Wire Braid Layer 
     A multilayered catheter shaft included an inner polymer layer of nylon 12 (Rilsan AESNO P40TL or Pebax 4033/3533), a middle polymeric layer of functionalized PVDF (KYNAR ADX®), and an outer polymeric layer of PVDF copolymer (KNAR FLEX® 2750). A metal wire braid layer was optionally included between the inner and middle polymeric layers or between the middle and outer polymer layers. The outer layer of PVDF copolymer provided high moisture resistance and excellent surface lubricity, the inner layer of polar polymer provided good mechanical properties, and the middle layer of functionalized PVDF acted as a tie or adhesive layer integrating the inner and outer layers, which were chemically very dissimilar. Relatively, the outer polymeric layer of PVDF copolymer provided a layer with a lubricity greater than that associated with a polar polymer, such as nylon. The metal wire braid layers, when used between the inner and middle layers or between the outer and middle layers, provided enhanced kink resistance and shaft strength. 
     EXAMPLE 6 
     Functionalized PVDF Middle Polymeric Layer and PVDF Homopolymer Inner Polymeric Layer with Metal Wire Braid Layer 
     A multilayered catheter shaft included an inner polymeric layer of PVDF homopolymer (KYNAR® 460), a middle polymeric layer of functionalized PVDF (KYNAR ADX®), and an outer polymeric layer of nylon 12 (Rilsan AESNO or Pebax 7233/7033). A metal wire braid layer was optionally included between the inner and middle polymeric layers, or between the middle and outer polymeric layers. Use of the PVDF homopolymer as the inner polymeric layer provided low frictional resistance to any components moving through the central lumen of the shaft. Relatively, the inner polymeric layer of PVDF homopolymer provided a layer with a lubricity greater than that associated with a polar polymer, such as nylon. 
     EXAMPLE 7 
     Catheter Shaft Embodiment 
     A catheter shaft  26   A  was constructed in accordance with the embodiment illustrated in  FIG. 5 . The catheter shaft  26   A  includes a proximal segment  27   A , a distal segment  29   A  and a transitional segment  28   A  smoothly tethering the proximal segment  27   A  and the distal segment  29   A . A reinforcing spring extends within the inner polymeric layers  30   A    30   B ,  30   C  of the shaft  26   A  from the proximal segment  27   A , through the transitional segment  28   A  and into a proximal portion of the distal segment  29   A , so as to enhance the torqueability and column strength of the shaft and kink resistance. A protective shrink tube  36   A  (preferably PVDF) is placed around a distal end of a reinforcing spring  34   A  to alleviate stress rise that may be produced by sudden changes in internal shaft  26   A  structure. 
     The inner polymeric layer of proximal segment  27   A , transitional segment  28   A , and distal segment  29   A  is the same polymeric tube extruded from functionalized PVDF (e.g., KYNAR ADX®). The middle polymeric layers  31   A ,  31   B ,  31   C  are different for different shaft segments. The middle polymer layers  31   A ,  31   B ,  31   C  consist of nylon 12 (Pebax 7233SA01 or AESNO) filled with 30% wt. barium sulfate for the proximal segment  27   A , Pebax 5533SA01 filled with 30% wt. barium sulfate in the transitional segment  28   A , and Pebax 3533SA01 filled with 40% wt. barium sulfate in the distal segment  29   A . The distal segment  29   A  is mechanically flexible and deflectable via an internal manipulation mechanism embedded within the shaft and extended proximally to the catheter handle (not shown here). The different polymers in the middle polymeric layers  31   A ,  31   B ,  31   C  are primarily to achieve increasing mechanical flexibility from the proximal to the distal ends of the shaft  26   A . The outer polymeric layers  32   A ,  32   B ,  32   C  are formed from a same tube extruded from functionalized PVDF, such as KYNAR ADX®. The outer polymeric layers  32   A ,  32   B ,  32   C  provide good hydrophobic barrier properties against body fluids or medical fluids and surface lubricity when the catheter shaft  26   A  is manipulated through the vasculature system. At the same time, the functionalized PVDF outer polymeric layers  32   A ,  32   B ,  32   C  allow for good adhesions with the polar middle polymer layers  31   A ,  31   B ,  31   C . A metal wire braid layer  33   A  extends from the proximal segment  27   A  to the portion of the transitional segment  29   A  or the deflectable distal segment  29   A , and can be reliably embedded into the middle polymer layers  31   A ,  31   B ,  31   C . Also, the inner polymeric layers  30   A ,  30   B ,  30   C  of the lubricious PVDF polymer allows for smooth passage of other medical devices during clinical uses. Relatively, the inner and outer polymeric layers of functionalized PVDF provided layers with lubricities greater than that associated with a polar polymer, such as nylon. 
     The deflectable distal segment  29   A  of a catheter shaft  26   A  plays an important role in the successes of medical procedures. Its mechanical performances during clinical procedures are of critical importance to manual manipulation of catheter devices, to a physician&#39;s feel, and to get easy accesses to human anatomy for delivering medical therapy on targeted anatomical sites. It is highly desirable to maintain the mechanical performances of the deflectable distal segment  29   A  of the catheter shaft  26   A  during the course of a medical procedure. On the other hand, due to its bulky structure, the distal segment  29   A  of the catheter shaft  26   A  can generally fulfill various clinical requirements on its mechanical performances. Therefore, to maintain the optimum and consistent mechanical strengths of catheter shafts within aqueous environments (consisting of body fluids and medical agents such as saline), the deflectable distal segment and transitional segment should be self-protected from the adverse influences on its mechanical performances arising from body fluids and medical agents. 
     Various embodiments are described herein to various apparatuses, systems, and/or methods. Numerous specific details are set forth to provide a thorough understanding of the overall structure, function, manufacture, and use of the embodiments as described in the specification and illustrated in the accompanying drawings. It will be understood by those skilled in the art, however, that the embodiments may be practiced without such specific details. In other instances, well-known operations, components, and elements have not been described in detail so as not to obscure the embodiments described in the specification. Those of ordinary skill in the art will understand that the embodiments described and illustrated herein are non-limiting examples, and thus it can be appreciated that the specific structural and functional details disclosed herein may be representative and do not necessarily limit the scope of the embodiments, the scope of which is defined solely by the appended claims. 
     Reference throughout the specification to “various embodiments,” “some embodiments,” “one embodiment,” or “an embodiment,” or the like, means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, appearances of the phrases “in various embodiments,” “in some embodiments,” “in one embodiment,” or “in an embodiment,” or the like, in places throughout the specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Thus, the particular features, structures, or characteristics illustrated or described in connection with one embodiment may be combined, in whole or in part, with the features, structures, or characteristics of one or more other embodiments without limitation given that such combination is not illogical or non-functional. 
     It will be appreciated that the terms “proximal” and “distal” may be used throughout the specification with reference to a clinician manipulating one end of a medical device or instrument used to treat a patient. The term “proximal” refers to the portion of the device closest to the clinician (or to a robotic control configured to manipulate the device) and the term “distal” refers to the portion located furthest from the clinician. It will be further appreciated that for conciseness and clarity, spatial terms such as “vertical,” “horizontal,” “up,” and “down” may be used herein with respect to the illustrated embodiments. However, medical devices may be used in many orientations and positions, and these terms are not intended to be limiting or absolute. 
     Although only certain embodiments have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the scope of this disclosure. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected/coupled and in fixed relation to each other. Additionally, the terms “electrically connected” and “in communication” are meant to be construed broadly to encompass both wired and wireless connections and communications. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the invention as defined in the appended claims. 
     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 materials does not conflict with existing definitions. 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.