Patent Publication Number: US-11027100-B2

Title: Expandable introducer assembly and method of using same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. patent application Ser. No. 15/337,835 filed on Oct. 28, 2016, the entire disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates generally to medical devices and procedures. In particular, the present disclosure relates to expandable introducer assemblies, and methods of using the same. 
     2. Description of the Prior Art 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     Numerous procedures have been developed that involve the percutaneous insertion of a medical device into the body of a patient, with the medical device being introduced into the body by a variety of known techniques. For example, access to coronary arteries, carotid arteries, the aorta, and peripheral vessels or other tubular members of the body for percutaneous therapeutic, diagnostic, and guide catheters is often made through introducer sheaths which are positioned into body vessels from outside the bodies. Such access sites include, but are not limited to, the common femoral artery/vein and the radial arteries, as well as the ureter, urethra, intestinal track, veins and other tubular tissues. However, the use of introducer sheaths and/or medical devices which are large relative to the body vessels to which they are inserted poses risks and challenges to both the patient and the physician. 
     For example, relative to femoral sheaths and catheters, larger introducer sheaths create sizeable arteriotomies in the femoral artery which cause more trauma to the patient, such as through artery avulsion, and create more challenges in placement of the sheath with risk of dissection. In addition, the forces required by the physician to insert the larger introducer sheaths and/or medical devices into the body vessel can be higher than desired and create medical issues for the patient if calcification within the body vessel is dislodged during insertion of the introducer sheath and/or medical device. 
     Methods of accessing a body vessel with a larger introducer sheath and/or medical device can begin by dilating the vessel with a radially expanding intravascular sheath assembly prior to introducing the medical device. However, such radially expanding sheaths have complex mechanisms, such as ratcheting or balloon mechanisms that expand and maintain the sheath in an expanded configuration while a medical device with a large diameter is introduced. Further, since the mechanisms effectuate the expansion of the body vessel, they do not provide a user with tactile feedback, and can even pose a risk of dissection during the procedure. Accessing the body vessel remains a challenge with existing expandable sheath assemblies due to the relatively large profile of the medical device inserted which causes longitudinal and radial tearing of the vessel during insertion. As mentioned above, these prior art delivery systems can even dislodge calcified plaque within the vessels during insertion, posing an additional risk of clots caused by the dislodged plague. 
     Accordingly, there remains a need in the art for an improved expandable introducer assembly for use with the percutaneous insertion of a medical device into a body vessel of a patient. 
     SUMMARY OF THE DISCLOSURE 
     This section provides a general summary of the disclosure and is not intended to be a comprehensive disclosure of its full scope, aspects, objectives, and/or all of its features. 
     An expandable introducer assembly for use in inserting a medical device into a body vessel of a patient includes a dilator, an introducer subassembly, an expandable sheath and a coupler. The dilator extends along an axis from a proximal dilator end to a distal dilator end. The introducer subassembly includes a hemostasis valve releasably interconnected to the proximal dilator end and an introducer sheath extending in surrounding and coaxial relationship with the dilator from the hemostasis valve to next adjacent the expandable sheath. The expandable sheath includes a sheath hub interchangeable from a locked condition for preventing axial movement of the dilator and the introducer subassembly relative to the expandable sheath during the insertion of the expandable introducer assembly into the body vessel of the patient and an unlocked condition for allowing concurrent axial advancement of the introducer subassembly and the dilator relative to the expandable sheath after the insertion of the expandable introducer assembly into the body vessel of the patient. This concurrent axial advancement allows the introducer sheath to pass through the sheath hub and into the expandable sheath for radially expanding the expandable sheath, and thus radially expanding the body vessel with the introducer sheath overlaid with the expandable sheath. The coupler is releasably connected to the sheath hub and is disposed in an interlocked relationship with the hemostasis valve when the hemostasis valve is axially advanced towards the sheath hub to facilitate serial retraction of the introducer sheath and the expandable sheath out of the body vessel of the patient. In other words, the serial retraction allows for the introducer sheath and then the expandable sheath to be removed from the body vessel of the patient in a single, continuous step such as by one continuous pulling motion of the hemostasis valve by a user. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments, and are not all possible implementations and thus are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a perspective view of an expandable introducer assembly constructed in accordance with the principles of the present disclosure; 
         FIG. 2  is a perspective view of a dilator subassembly extending from a proximal end to a distal end and including a dilator having a insertion portion disposed adjacent the distal end, an expansion portion disposed adjacent the proximal end, and a tapered transition portion disposed therebetween and being tapered from the insertion portion to the expansion portion; 
         FIG. 3  is a magnified and fragmentary perspective view of the proximal end of the dilator subassembly illustrating a dilator hub defining an guide wire opening for receiving a guide wire to guide the expandable introducer assembly into a body vessel of a patient; 
         FIG. 4  is a fragmentary perspective view of the proximal end of the dilator subassembly illustrating a guide tube extending between the dilator hub and the expansion portion of the dilator, and a plurality of locking tabs extending from the dilator hub that lock to a proximal end of a valve; 
         FIG. 5  is a top view of an expandable sheath subassembly including an expandable sheath extending from a sheath hub; 
         FIG. 6  is an end view of the expandable sheath subassembly illustrating a hub passageway and coupling tabs of the sheath hub; 
         FIG. 7  is a perspective view of an introducer subassembly including an introducer sheath extending from a hemostatic valve; 
         FIG. 8  is a magnified fragmentary view of a portion of  FIG. 7  illustrating a nose cap threadingly secured to the hemostatic valve and defining a plurality of recesses; 
         FIG. 9  is an end view of the introducer subassembly illustrating an elastomeric seal compressed within the hemostatic valve and a plurality of circumferential grooves and notches defined by a first valve housing end of the hemostatic valve; 
         FIG. 10  is a magnified and fragmentary perspective view of the expandable sheath subassembly illustrating a duckbill shaped collar disposed in overlaying relationship with the expandable sheath; 
         FIG. 11  is a magnified and fragmentary perspective view of the expandable sheath subassembly illustrating a crown shaped collar disposed in overlaying relationship with the expandable sheath; 
         FIG. 12  is a magnified and fragmentary perspective view of the distal end of the dilator subassembly illustrating an expandable sheath nested between the introducer portion of the dilator and a distal sheath; 
         FIG. 13  is a cross-sectional view of the dilator subassembly taken along  13 - 13  and illustrating the expandable sheath being pleated and/or folded/wrapped when nested between the introducer portion of the dilator and the distal sheath; 
         FIG. 14  is a magnified and fragmentary perspective view of the dilator subassembly illustrating a locking orifice defined by the expansion portion of the dilator and the distal sheath overlaying the insertion portion of the dilator; 
         FIG. 15  is a fragmentary perspective view of the expandable introducer assembly illustrating a locking key disposed in mating relationship with the sheath hub and releasably interlocked with the locking orifice defined by the expansion portion of the dilator; 
         FIG. 16  is a perspective view of the locking key illustrating a U-shaped stopper for mating with a U-shaped mouth of the sheath hub; 
         FIG. 17  is a bottom view of the locking key illustrating a locking projection for mating with the locking orifice of the expansion portion of the dilator; 
         FIG. 18  illustrates an axial movement of the expandable introducer assembly along a guide wire to facilitate an initial insertion of the insertion portion of the dilator through an insertion site of the patient; 
         FIG. 19  is a cross-sectional view of a body vessel of a patient taken along  19 - 19  of  FIG. 18  illustrating the guide wire extending axially therein; 
         FIG. 20  illustrates an axial movement of the insertion portion of the dilator into the body vessel to dispose the tapered transition portion of the dilator and the sheath hub next adjacent the insertion site; 
         FIG. 21  is a cross-sectional view of the body vessel taken along  21 - 21  of  FIG. 20  illustrating the insertion portion of the dilator disposed therein; 
         FIG. 22  illustrates a removal of the locking key from the sheath hub to allow concurrent axial advancement of the expansion portion of the dilator and the introducer sheath through the sheath hub to advance the dilator subassembly relative to the expandable sheath subassembly and retract the expandable sheath out from its nested relationship between the distal sheath and the insertion portion of the dilator and into overlaying relationship with the introducer sheath axially advanced into the body vessel; 
         FIG. 23  is a cross-sectional view of the body vessel taken along  23 - 23  of  FIG. 22  illustrating the introducer sheath disposed in overlaying relationship with the expansion portion of the dilator and the expandable sheath disposed in overlaying relationship with the introducer sheath; 
         FIG. 24  illustrates further concurrent axial advancement of the introducer and dilator subassemblies relative to the expandable sheath subassembly to place the hemostatic valve into abutting and coupled relationship with the hub and dispose the hemostatic valve next adjacent the insertion site; 
         FIG. 25  illustrates an axial removal of the dilator subassembly from the introducer sheath and the hemostatic valve; 
         FIG. 26  is a cross-sectional view of the body vessel taken along  26 - 26  of  FIG. 25  illustrating the dilator subassembly removed from the introducer subassembly to leave only the expandable sheath and the introducer sheath within the body vessel; 
         FIG. 27  illustrates an axial removal of the introducer subassembly out of the expandable sheath subassembly to leave only the expandable sleeve within the body vessel; 
         FIG. 28  is a cross-sectional view of the body vessel taken along  28 - 28  of  FIG. 27  illustrating the expandable sheath collapsed within the body vessel following removal of the introducer sheath; 
         FIG. 29  illustrates an application of direct radial pressure on the insertion site by a physician to collapse the expandable sheath and maintain hemostasis during removal of the expandable sheath from the body vessel of the patient; 
         FIG. 30  is a cross-sectional view of the body vessel taken along  30 - 30  of  FIG. 29  illustrating the collapse of the expandable sheath under the influence of the direct radial pressure; 
         FIG. 31  is a cross-sectional view of the body vessel after removal of the expandable sheath subassembly; 
         FIG. 32  is a perspective view of an alternative embodiment of the expandable introducer assembly illustrating the expandable introducer assembly adjacent the body of a patient prior to initial insertion into the body vessel of the patient and illustrating a coupler disposed between the sheath hub and the locking key; 
         FIG. 33  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the initial insertion of the expandable introducer assembly into the body vessel of the patient with the locking key preventing axial movement of the introducer subassembly and dilator subassembly relative to the expandable sheath; 
         FIG. 34  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the releasing of the locking key once the expandable introducer assembly has been initially inserted into the body vessel of the patient and axial movement of the hemostasis valve towards the coupler; 
         FIG. 35  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the hemostasis valve disposed next adjacent the receiving body and in an interlocked relationship with the coupler; 
         FIG. 36  is a cross-sectional, top view illustrating the sheath hub being u-shaped to define a pair of flanges and the coupler including a receiving body including tabs for releasably interlocking to the pair of flanges and a tether extending between the receiving body and the sheath hub for coupling the introducer subassembly to the expandable sheath and the sheath hub defining a cavity for containing the tether; 
         FIG. 37  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the dilator subassembly being axial retracted away from the body vessel and out of the introducer subassembly; 
         FIG. 38  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the retraction of the introducer subassembly away from the body vessel of the patient with the tether becoming taught about the introducer sheath to pull the expandable sheath for allowing the serial retraction of the introducer sheath and the expandable sheath out of the body vessel of the patient; 
         FIG. 39  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the serial retraction of the introducer sheath and the expandable sheath out of the body vessel of the patient via manual retraction of the introducer sheath axial away from the body vessel of the patient; 
         FIG. 40  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating a first embodiment of the tether including a plurality of sheets interconnected with one another in collapsible and expandable accordion like fashion; 
         FIG. 41  is a top view of the first embodiment of the tether illustrating an alternative arrangement of the plurality of sheets; 
         FIG. 42 a    is a top perspective view of the alternative embodiment of the expandable introducer assembly illustrating a second embodiment of the tether comprised of strands of material interlaced with one another and disposed in a semi-collapsed position; 
         FIG. 42 b    is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the second embodiment of the tether in a taught position; 
         FIG. 43 a    is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating a third embodiment of the tether comprised of a plurality of fibers orthogonally woven together and disposed in a semi-collapsed position; 
         FIG. 43 b    is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the third embodiment of the tether extending to a taught position; 
         FIG. 44  is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating a fourth embodiment of the tether extended to a taught position and comprised of a plurality of rings serially arranged between the sheath hub and the receiving body and connected to one another by at least one string; 
         FIG. 45 a    is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating a fifth embodiment of the tether comprising at least one cord extending between the sheath hub and the coupler and disposed in a semi-collapsed position; 
         FIG. 45 b    is a perspective view of the alternative embodiment of the expandable introducer assembly illustrating the fifth embodiment of the tether extending to a taught position; 
         FIG. 46  is a perspective view of a second alternative embodiment of expandable introducer assembly including a casing extending between a proximal casing end disposed in abutting relationship with the hemostasis valve and a distal casing end disposed in mating and releasably interlocked relationship with the receiving body for establishing the locked condition of the sheath hub and preventing concurrent axial advancement of the introducer subassembly and said dilator relative to said expandable sheath; 
         FIG. 47  is a perspective view of the second alternative embodiment of expandable introducer assembly illustrating the casing defining a trough extending between the casing the expandable sheath and defining an orifice for receiving a syringe; 
         FIG. 47 a    is a magnified perspective-view of a portion of  FIG. 47  illustrating a clamp disposed at the distal casing end and defining the orifice disposed in fluid connection with the trough; 
         FIG. 48  is a perspective view of an alternative embodiment of the expandable introducer assembly disposed adjacent the body of a patient prior to initial insertion into the body vessel of the patient; 
         FIG. 49  is a perspective view of the second alternative embodiment of the expandable introducer assembly illustrating the initial insertion of the expandable introducer assembly into the body vessel of the patient; 
         FIG. 50  is a perspective view of the second alternative embodiment of the expandable introducer assembly illustrating a releasing of the casing once the expandable introducer assembly has been initially inserted into the body vessel of the patient; 
         FIG. 51  is a magnified perspective view of the second alternative embodiment of the expandable introducer assembly illustrating the clamp of the casing in a closed position; 
         FIG. 52  is a magnified perspective view of the second alternative embodiment of the expandable introducer assembly illustrating the clamp of the casing in an open position. 
     
    
    
     DESCRIPTION OF THE ENABLING EMBODIMENTS 
     Example embodiments will now be described more fully with reference to the accompanying drawings. The example embodiments are provided so that this disclosure will be thorough and fully convey the scope to those skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, mechanisms, assemblies, and methods to provide a thorough understanding of various embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms, and that neither should be construed to limit the scope of the disclosure. With this in mind, the present disclosure is generally directed to expandable introducer assemblies of the type used to introduce and withdrawal a medical device (e.g., catheter systems, implants, etc.) into a body vessel of a patient. 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, an expandable introducer assembly  10  for use in inserting a medical device into a body vessel  108  of a patient includes a dilator subassembly  12  which extends from a proximal end  14  to a distal end  16  along an axis A. As best shown in  FIG. 2 , the dilator subassembly  12  includes a dilator  18  extending from a dilator hub  20  disposed adjacent the proximal end  14  to a distal dilator tip  22  disposed adjacent the distal end  16 . The dilator  18  is comprised of a flexible low-friction polymeric material that may be radiopaque and has an insertion portion  24  disposed adjacent the distal end  16  which has a low insertion profile so that, as shown in  FIGS. 18, 32, 38, and 48 , an initial insertion of the expandable introducer assembly  10  into the body vessel  108  of the patient can easily be achieved. In a preferred arrangement, the low insertion profile has an insertion outer diameter being approximately 8.5 F. However, other suitable outer diameters could be utilized for facilitating an initial insertion of the expandable introducer assembly  10  without departing from the scope of the subject disclosure. 
     A distal sheath  26  overlays the insertion portion  24  of the dilator  18  and is attached or fused to the distal dilator tip  22 . The distal sheath  26  is comprised of low friction polymeric material for creating a low friction surface of the dilator  18  to ease an initial insertion of the dilator  18  into the body vessel  108  of the patient. In a preferred embodiment, the low friction polymeric material is polyethylene, however, other suitable low friction polymeric materials could also be used without departing from the scope of the subject disclosure. As best shown in  FIG. 2 , the dilator  18  also has a tapered transition portion  28  disposed adjacent the insertion portion  24  and the distal sheath  26 . The tapered transition portion  28  is tapered outwardly from the insertion portion  24  to an expansion portion  30  which has an expansion profile being larger than the insertion profile. In a preferred arrangement, the larger expansion profile has an expansion outer diameter being approximately 18 F for compatibility with an appropriately sized introducer device. However, other expansion outer diameters that are larger than the insertion diameters could be utilized without departing from the scope of the subject disclosure. As will be explained in more detail below, and as illustrated by  FIGS. 20-22, 32-35 and 48-50 , the tapered and expansion portions  28 ,  30  of the dilator  18  facilitate a radial expansion of the body vessel  108  during an insertion of the dilator subassembly  12  into the body vessel  108  of the patient. In other words, only radial forces are applied to the vessel wall by the tapered transition portion  28  of the dilator  18 . This insertion process is advantageous because it reduces trauma to the body vessel  108  which does not require a pushing of the insertion and tapered transition portions  28 ,  30  of the dilator  18  past any calcification that is present in the vessel  108 , but rather applies radial forces to the vessel wall during insertion of the dilator subassembly  12 . Although not expressly shown, the dilator  18  defines a guide wire passageway which extends between the proximal and distal ends  14 ,  16  and which receives a guide wire  32  for guiding the dilator  18  into the body vessel  108  during insertion. As best illustrated in  FIG. 3 , the dilator hub  20  defines a guide wire opening  36  for initial receipt of the guide wire  32  to allow the guide wire  32  to be threaded through the dilator  18  along the guide wire passageway. 
     As best shown in  FIGS. 1, 18, 32, and 46 , the expandable introducer assembly  10  includes an introducer subassembly  38  disposed in a surrounding and coaxial relationship with the expansion portion  30  of the dilator  18 . The introducer subassembly  38  includes a hemostatic valve  40  disposed adjacent a proximal end  14  of the dilator subassembly  12  and releasably interlocked with the dilator hub  20  in a locked condition of the expandable introducer assembly  10 . In a preferred embodiment, the hemostatic valve  40  can be a variable diameter seal hemostatic valve as described in co-owned U.S. patent application Ser. No. 14/326,593 entitled “A Medical Valve with a Variable Diameter Seal” or U.S. patent application Ser. No. 14/726,099 entitled “An Automatic Medical Valve with Variable Seal”, the entire disclosures of which is incorporated by reference. However, other valves, such as iris valves, laparoscopic ports, slit valves, or the like, can also be utilized without departing from the scope of the subject disclosure. 
     The hemostatic valve  40  includes a valve housing  42  extending from a first valve housing end  44  to a second valve housing end  46 . As best illustrated in  FIG. 9 , an elastomeric seal  47  is compressed within the valve housing  42  and has an inner diameter for use in establishing a seal with a medical device inserted through the first valve housing end  44  of the hemostatic valve  40 . A manual actuator  48 , such as a pair of lever arms  49  or the like, is interconnected to the valve housing  42  for allowing a physician to interact with the expandable introducer assembly  10  and vary a size of the inner diameter of the elastomeric seal  47  to establish an open condition of the hemostatic valve, such as illustrated in  FIG. 9 . As best illustrated in  FIGS. 1 and 7 , a locking member  50  is releasable interconnected with the manual actuator  48  for maintaining the hemostatic valve  40  in the open condition. As will be explained in more detail below, the locking member  50  allows the dilator subassembly  10  to be axially threaded or advanced through the hemostatic valve  40 , particularly through the inner diameter of the elastomeric seal  47 , to dispose the hemostatic valve  40  in abutting relationship with the dilator hub  20  in the locked position of the expandable introducer assembly  10 . The locking member  50  also allows the dilator subassembly  12  to be axially removed from the hemostatic valve  40  once the introducer subassembly  38  is introduced into the body vessel  108  of a patient. In a preferred arrangement, the locking member  50  includes at least one locking pin  52  disposed in engaging relationship with the pair of lever arms  49  to hold the lever arms  49  in a compressed position and maintain the hemostatic valve  40  in the open condition. However, other means of locking and maintaining the hemostatic valve  40  in the open condition could be utilized without departing from the scope of the subject disclosure. 
     As best illustrated in  FIGS. 3-4 and 9 , in a preferred arrangement the dilator hub  20  includes a plurality of ramped locking tabs  54  and the first valve housing end  44  defines a plurality of circumferential grooves  56  opening to notches  58  for receiving the ramped locking tabs  54  and allowing manual rotation of the ramped locking tabs  54  within the circumferential grooves  56  to establish the interlocked relationship of the hemostatic valve  40  with the dilator hub  20 . Put another way, the dilator hub  20  is rotatable about the axis A to threadingly interlock the hemostatic valve  40  to the dilator hub  20  and establish the locked condition of the expandable introducer assembly  10 . As will be described in more detail below, after the dilator and introducer sheath subassembly  12 ,  38  have been axially advanced into the body vessel and the physician desires to unlock the dilator subassembly  12  from the introducer subassembly  38 , the dilator hub  20  is counter-rotated about the axis A to unthread the ramped locking tabs  54  from the circumferential grooves  56  and align the ramped  FIG. 54  with the notches  58  to allow the dilator subassembly  12  to be axially retracted from the introducer subassembly  38  through the hemostatic valve  40 . Although the interlocked relationship between the dilator hub  20  and the hemostatic valve  40  has been described with respect to ramped locking tabs  54  and circumferential grooves  56  notches  58 , other means of establishing the interlocked relationship, such as a direct snap fit or the like, could also be utilized without departing from the scope of the subject disclosure. 
     As best illustrated in  FIGS. 2-4 , the dilator subassembly  12  includes a guide tube  60  disposed between the dilator hub  20  and the expansion portion  30  of the dilator  18  for interconnecting the dilator hub  20  with the expansion portion  30  of the dilator  18 . The guide tube  60  is disposed in coaxially aligned relationship with the elastomeric seal  47  of the hemostatic valve  40  when the hemostatic valve  40  is interlocked with the dilator hub  20 . The guide tube  60  has an outer guide tube diameter being less than the inner diameter of the seal when the hemostatic valve  20  is disposed in the open position to eliminate any radial compression forces imposed on the elastomeric seal  47  by the dilator subassembly  12 . Put another way, the guide tube  60  is not radially compressed against the elastomeric seal  47  in the interlocked position of the hemostatic valve  40  and dilator hub  20 , but rather is disposed in spaced relationship with the elastomeric seal  47  to reduce stress and wear on the elastomeric seal  47  of the hemostatic valve  40  during shipment and storage of the expandable introducer assembly  40  in the locked and open condition prior to use. 
     The introducer subassembly  38  includes a proximal introducer sheath  62  disposed in surrounding and coaxial relationship with the expansion portion  30  of the dilator  18 . The proximal introducer sheath  62  extends from a first introducer sheath end  64  being fixed to the second valve housing end  46  of the hemostatic valve  40  to a second introducer sheath end  66  disposed in spaced relationship with the tapered transition portion  28  of the dilator  18 . The introducer sheath  62  preferably has a constant introducer sheath diameter extending along its length which is complementarily sized to and disposed in overlaying relationship with the expansion portion  30  of the dilator  18 . In a preferred arrangement, the constant diameter ranges between 16 FR to 34 FR and is complementarily sized to the medical device that will be passing through the introducer sheath  62  and into the body vessel  108 . However, other constant diameter ranges could also be utilized without departing from the scope of the subject disclosure. The introducer sheath  62  can also be designed and fabricated using known methods such as coextruded tubing or reinforced construction having a PTFE or other low friction polymer liner, reinforced layer and thermoplastic polymer outer jacket. As best illustrated in  FIGS. 7 and 8 , the hemostatic valve  40  includes a nose cap  68  threadingly secured to the second valve housing end  46  for establishing a compression fit of the introducer sheath  62  between the nose cap  68  and the second valve housing end  46 . 
     As best shown in  FIGS. 1, 18, 32, and 46  the expandable introducer assembly  10  includes an expandable sheath subassembly  70  releasably interlocked with the dilator subassembly  12  in the locked condition of the expandable introducer assembly  10 . The expandable sheath subassembly  70  is disposed in surrounding and coaxial relationship with the insertion and tapered transition portions  24 ,  28  of the dilator  18 . The expandable sheath subassembly  70  includes a sheath hub  72  extending from a first hub end  74  releasably interlocked with the expansion portion  30  of the dilator  18  to a second hub end  76  which defines a hub passageway  78  disposed in surrounding and coaxial relationship with the expansion portion  30  of the dilator  18 . The expandable sheath assembly  70  includes an expandable sheath  80  extending from the second hub end  76  to adjacent the distal dilator tip  18  of the dilator  18 . As best illustrated in  FIGS. 10-13 , the expandable sheath  80  overlays the tapered transition portion  28  and is nested between the distal sheath  26  and the insertion portion  24  when the expandable introducer assembly  10  is disposed in the locked condition. As further illustrated in  FIG. 13 , in a preferred embodiment the expandable sheath  80  is pleated, rolled, or folded upon itself when nested between the distal sheath  26  and the insertion portion  24  of the dilator  18 . 
     As best illustrated in  FIGS. 10-11 , the expandable sheath subassembly  70  includes a collar  82  disposed adjacent the second hub end  76  in overlaying relationship with the expandable sheath  80 . In a preferred arrangement, the collar  82  is thermally bonded to the expandable sheath  80  and has a tensile strength being larger than the expandable sheath  80  to provide column strength and added reinforcement to the expandable sheath  80  as the dilator subassembly  12  is advanced into the body vessel  108  of the patient. As will be described in more detail below, and as best illustrated in  FIGS. 27 and 29 , upon completion of a medical procedure, only the expandable sheath subassembly  70  will remain in the body vessel  108  of the patient. Accordingly, as best illustrated in  FIG. 10 , in a first arrangement the collar  82  is duckbill shaped for allowing direct radial pressure applied by a physician on the collar  82  to collapse the expandable sheath  80  within the body vessel  108 . For example, as best illustrated in  FIG. 27 , when a physician removes the introducer sheath subassembly  38  from the expandable sheath subassembly  70 , the physician can press down on the collar  82  to seal off the lumen, if desired. As best illustrated in  FIG. 11 , in an alternative arrangement the collar  82  can be crown shaped to also allow the collar  82  to collapse under direct radial pressure by the physician. 
     As best illustrated in  FIG. 15 , the expandable sheath subassembly  70  includes a locking key  84  coupled to the sheath hub  72  and releasably interlocked with the expansion portion  30  of the dilator  18 . The locking key  84  establishes a locked condition of the sheath hub  72  and prevents axial movement of the introducer and dilator subassemblies  12 ,  38  relative to one another to establish the interlocked relationship between the introducer subassembly  38  and the dilator subassembly  12 . As best illustrated in  FIGS. 14-15 and 17 , in a preferred arrangement the locking key  84  mates with the first hub end  74  and includes a locking projection  86  disposed in mating relationship with a corresponding locking orifice  88  defined by the expansion portion  30  of the dilator  18 . The sheath hub  72  includes a pair of flanges  90  disposed about the first hub end  74  to define a U-shaped mouth  92  and the locking key  84  has a corresponding U-shaped stopper  94  for nesting within the mouth  92  of the sheath hub  72 . This mating arrangement prevents the dilator subassembly  12  from axially advancing relative to the expandable sheath subassembly  70  in the locked condition of the expandable introducer assembly  10 . 
     As best illustrated in  FIGS. 20 and 22 , after the dilator subassembly  12  is axially advanced into the body vessel  108  to place the sheath hub  72  next adjacent to the insertion site  106 , the locking key  84  is removable from the sheath hub  72  and the expansion profile  30  of the dilator  18  to unlock the expandable sheath and dilator subassemblies  12 ,  70  from one another and establish an unlocked condition of the expandable introducer assembly  10 . As best illustrated in  FIG. 6 , the hub passageway  78  has an inner diameter being slightly larger than the introducer sheath diameter of the introducer sheath  62 . As will be described in more detail below, in the unlocked condition of the expandable introducer assembly  10 , the dilator and introducer sheath subassemblies  12 ,  38  can be concurrently axially advanced through the hub passageway  78  to advance the dilator subassembly  12  further into the body vessel and simultaneously pull or retract the expandable sheath  80  out of its nested positioning between the insertion portion  24  of the dilator  18  and distal sheath  26  and into overlaying relationship with the introducer sheath  62 . Put another way, the expandable sheath subassembly  70  is held in position with the sheath hub  72  disposed next adjacent the insertion site  106  while the dilator and introducer subassemblies  12 ,  38  are concurrently axially advanced through the sheath hub  72  and further into the body vessel  108 . As best illustrated in  FIG. 24 , the dilator and introducer subassemblies  12 ,  38  are concurrently axially advanced until the nose cap  68  of the hemostatic valve  40  is disposed in nested and mating relationship with the U-shaped mouth  92  of the sheath hub  72  to place the expandable sheath  80  in overlaying relationship with the introducer sheath  62 . Accordingly, the sliding advancement of the introducer subassembly  38  through the sheath hub  72  by way of concurrent axially advancement with the dilator subassembly  12  retracts the expandable sheath  80  from its nesting positioning and disposes the expandable sheath  80  in overlaying relationship with the introducer sheath  62 , and thus provides a protective layer for the introducer sheath  62  when disposed within the body vessel  108 . In other words, the expandable sheath provides a protection barrier against shear forces applied to the wall of the body vessel during an introduction of the tapered and expansion portions as well as the introducer sheath. This expandable sheath  80  also provides for easier insertion of the introducer sheath  62  into the body vessel  108  by way of the lower friction barrier that is created by the expandable sheath  80 . This insertion process is advantageous because it reduces trauma to the body vessel  108  and does not require a pushing of the introducer sheath  62  past any calcification that is present. 
     As best illustrated in  FIGS. 8 and 15 , the nose cap  68  defines a plurality of recesses  96  and the sheath hub  72  includes a plurality of coupling tabs  98  which are each coupled with a respective recess  96  to couple the hemostatic valve  40  to the sheath hub  72 . Once the sheath hub  72  and hemostatic valve  40  are coupled together, the entire expandable sheath  80  overlays the introducer sheath  62  to establish one combined sheath disposed within the body vessel  108 . Furthermore, once the sheath hub  72  and hemostatic valve  40  are coupled together, and the combined expandable and introducer sheath  62 ,  80  are disposed in the body vessel  108 , the dilator cap  20  is counter-rotated about the axis A to unthread the ramped locking tabs  54  from the circumferential grooves  56  and align the ramped  FIG. 54  with the notches  58  to allow the dilator subassembly  12  to be axially retrieved or retracted through the introducer subassembly  38  to leave only the expandable and introducer subassemblies  38 ,  70  in the body vessel  108  of the patient. In this position, with the hemostatic valve  40  is disposed just outside the insertion site  106  of the patient. As a result, a medical device can now be serially inserted through the hemostatic valve  40  and the introducer sheath  62  and into the body vessel  108  by a physician. 
     When the use of the medical procedure is complete and the medical device has been removed from the introducer subassembly  38 , the coupling tabs  98  of the sheath hub  72  can be radially compressed to release the coupling tabs  98  from the recesses  96  disposed on the nose cap  68  of the hemostatic valve  40 . As best illustrated in  FIG. 27 , the physician is then able to manually pull on the hemostatic valve  40  to retract the introducer sheath  62  along the axis A and out of the expandable sheath  80 . This retraction separates the introducer and expandable subassemblies  38 ,  70  and, as best shown in  FIG. 28 , leaves the expandable sheath  80  within the body vessel  108  in a collapsed state. For example, the expandable sheath  80  collapses back to approximately less than a 12 F profile to facilitate removal. As described previously, and as shown in  FIGS. 29 and 30 , direct radial pressure can now be applied by a physician on the collar  82  to collapse the expandable sheath  80  within the body vessel  108  and maintain hemostasis. The expandable sheath  80  can then be slowly removed from the body vessel  108  and appropriate closure procedures can be utilized to close the insertion site  106  of the patient. 
     A flush port  100  can be in fluid communication with the hemostatic valve  40  for flushing the expandable introducer assembly  10  prior to introducing the distal dilator tip  22  of the dilator  18  into the body vessel  108  of the patient. As best illustrated in  FIG. 12 , the insertion portion  24  of the dilator  18  defines a flushing hole  102  which is in fluid communication with the flush port  100  via the guide wire passageway for allowing a back flushing of the expandable sheath  80  and the distal sheath  26  prior to use of the expandable introducer assembly  10 . The dilator subassembly  12  also includes a radiopaque marker  104  disposed adjacent the distal dilator tip  22  in nested relationship between the distal sheath  26  and the insertion portion  24  of the dilator  18 . 
     Referring to the Figures, wherein like numerals indicate corresponding parts throughout the several views, the subject disclosure also includes a method of inserting an expandable introducer assembly  10  into a body vessel  108  of a patient along a guide wire  32 . As best shown in  FIG. 18 , the method begins by inserting an insertion portion  24  of a dilator  18  that is overlaid with a distal sheath  26  comprised of a low friction polymeric material and includes an expandable sheath  80  nested between the insertion portion  24  and the distal sheath  26  through an insertion site  106  and into the body vessel  108  of a patient. A flush port  100  is in fluid communication with the dilator  18  for flushing the distal sheath  26  and the expandable sheath  80  prior to introducing the insertion portion  24  of the dilator  18  into the body vessel  108  of the patient. 
     As best shown in  FIG. 21 , once the insertion portion  24  of the dilator  18  is placed within the body vessel  108 , the insertion portion  24  of the dilator  18  occupies a cross section of the vasculature equal in size to an outer diameter of the distal sheath, preferably about 8.5 F. As best shown in  FIG. 20 , the method proceeds by axially advancing the insertion portion  24  of the dilator  18  further into the body vessel  108  to radially expand the body vessel  108  with a tapered transition portion  28  of the dilator  18  that is overlaid with the expandable sheath  80  to dispose a sheath hub  72  fixed to the expandable sheath  80  and releasable interlocked with an expansion portion  30  of the dilator  18  next adjacent the insertion site  106 . As best shown in  FIG. 22  as another example, the method proceeds by removing a locking key  84  to unlock the sheath hub  72  from the dilator  18  and allow axial movement of the dilator  18  relative to the sheath hub  72  and the interconnected expandable sheath  80 . 
     As best shown in  FIG. 22  as another example, once the locking key  84  is removed from the expandable introducer assembly  10 , the method proceeds by concurrently axially advancing the expansion portion  30  of the dilator  18  and an introducer sheath  62  disposed in surrounding and overlaying relationship with the expansion portion  30  through the sheath hub  72  and into the body vessel  108  to simultaneously retract the expandable sheath  80  out of its nested relationship with the insertion portion  24  of the dilator  18  and distal sheath  26  and into overlaying relationship with the introducer sheath  62  disposed within the body vessel  108 . As best illustrated in  FIG. 23 , the axial advancement of the introducer sheath  62  results in a radial expansion of the body vessel  108  to the outer diameter of the introducer sheath  62 , preferably 18 F. In other words, only radial forces are applied to the vessel wall during insertion of the tapered transition portion  28  of the dilator  18 . As also illustrated in  FIG. 22 , a first introducer sheath end  64  of the introducer sheath  62  is fixed to a hemostatic valve  40 . In a preferred embodiment, the hemostatic valve  34  can be a variable diameter seal hemostatic valve as disclosed in co-owned U.S. patent application Ser. No. 14/326,593 entitled “A Medical Valve with a Variable Diameter Seal”, the entire disclosure of which is incorporated by reference. However, other valves, such as iris valves, laparoscopic ports, or the like, can also be utilized without departing from the scope of the subject disclosure. 
     As best illustrated in  FIGS. 24 and 35 , advancement of the introducer sheath  62  into the body vessel  108  also axially advances the hemostatic valve  40  into abutting and coupled relationship with the sheath hub  72  to dispose the hemostatic valve  40  next adjacent the insertion site  106  of the patient. As best illustrated in  FIGS. 6 and 8 , the hemostatic valve  40  includes a nose cap  68  which defines a plurality of recesses  96  and the sheath hub  72  includes a plurality of coupling tabs  98  which are each coupled with a respective recess  96  to couple the hemostatic valve  40  to the sheath hub  72 . Once the sheath hub  72  and the hemostatic valve  40  are coupled together, the entire expandable sheath  80  overlays the introducer sheath  62  to establish one combined sheath disposed within the body vessel  108 . 
     As best illustrated in  FIGS. 25 and 37 , the method proceeds by unlocking the dilator  18  from the hemostatic valve  40  and axially removing the dilator  18  from the introducer sheath  62  and the hemostatic valve  40 . In a preferred arrangement, the dilator  18  includes a dilator hub  20  that is rotatably interlocked with a first valve housing end  44  of the hemostatic valve  40 . For example, as best illustrated in  FIG. 4 , the dilator hub  20  includes a plurality of ramped locking tabs  54  and the first valve housing end  44  defines a plurality of circumferential grooves  56  opening to notches  58  for receiving the ramped locking tabs  54  and allowing axial rotation of the ramped locking tabs  54  within the circumferential grooves  56  to establish the interlocked relationship of the hemostatic valve  40  with the dilator hub  20 . Accordingly, when a physician desires to unlock the dilator  18  from the hemostatic valve  40 , the dilator hub  20  is counter-rotated about the axis A to unthread the ramped locking tabs  54  from the circumferential grooves  56  and align the ramped locking tabs  54  with the notches  58  to allow the dilator subassembly  12  to be axially removed from the introducer sheath  62  and through the hemostatic valve  40 . 
     As best illustrated in  FIG. 26 , the axial removal of the dilator subassembly  12  leaves only the introducer sheath  62  overlaid with the expandable sheath  80  within the body vessel  108  of the patient. Furthermore, in this arrangement, the introducer sheath  62  is interconnected to the hemostatic valve  40  which is disposed outside the body of the patient. As a result, a medical device can now be serially inserted through the hemostatic valve  40  and the introducer sheath  62  and into the body vessel  108  by a physician. 
     When the medical procedure is complete and the medical device has been removed from the introducer sheath  62 , as best illustrated in  FIG. 27 , the method proceeds by releasing the sheath hub  72  from the hemostatic valve  40  and axially removing the hemostatic valve  40  and the introducer sheath  62  out of the expandable sheath  80 . As best illustrated in  FIG. 28 , this axial movement separates the introducer sheath  62  from the expandable sheath  80  and leaves the expandable sheath  80  within the body vessel  108  in a collapsed state. Accordingly, as best illustrated in  FIG. 29 , the method proceeds by the application of direct radial pressure on the expandable sheath  80  by a physician to further collapse the expandable sheath  80  within the body vessel  108  and maintain hemostasis during removal of the expandable sheath  80 . As best illustrated in  FIG. 30 , the expandable sheath has a relative flat cross section in its radially collapsed state and thus can be removed from the body vessel as a “limp noodle”. As best illustrated in  FIGS. 10 and 11 , in a preferred arrangement the expandable sheath includes a collar  82  that is thermally bonded to the expandable sheath  80  and is preferably either duckbill shaped or crown-shaped to facilitate an initial collapse of the expandable sheath  80  in response to direct radial pressure by a physician. As best illustrated in  FIG. 30 , the method concludes by removing the expandable sheath  80  from the body vessel followed by an appropriate closure method to close the insertion site  106  of the patient. 
     As illustrated in  FIGS. 32-52 , an alternative embodiment of the expandable introducer assembly  10  includes a coupler  118  releasably connected to the sheath hub  72  and disposed in an interlocked relationship with the hemostasis valve  40  when the hemostasis valve  40  is axially advanced towards the sheath hub  72 . The coupler  118  allows for serial retraction of the introducer sheath  62  and the expandable sheath  80  out of the body vessel  108  of the patient. In other words, and as best illustrated in  FIGS. 38 and 39 , as the introducer sheath  62  is pulled out of the body vessel of the patient the coupler  118  is detached from and becomes taught between the sheath hub  72  and the hemostasis valve  40  to also pull the expandable sheath  80  from the body vessel. Rather than the expandable sheath  80  and the introducer sheath  62  being removed in separate steps, as is required in the earlier disclosed embodiment, the coupler  118  allows for the removal of each in one step via one continuous pulling movement on the hemostasis valve  40 . 
     As best illustrated in  FIGS. 38-40 and 42-45 , the coupler  118  includes a receiving body  120  for establishing the releasable connection to the sheath hub  72  and the interlocked relationship with the hemostasis valve  40 . The coupler  118  includes a tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  extending between the receiving body  120  and the sheath hub  72  for coupling the introducer subassembly  38  to the expandable sheath  80  and facilitating the serial retraction of the introducer sheath  62  and the expandable sheath  80  out of the body vessel  108  of the patient. The tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  defines a passageway  132  extending between the receiving body  120  and the sheath hub  72  for receiving the introducer sheath  62  when the introducer sheath  62  is passed through the sheath hub  72  and into the expandable sheath  80 . The tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is comprised of a material of sufficient tensile strength, lubricity, and resistance to fatigue to allow for the serial retraction of the introducer sheath  62  and the expandable sheath  80 . For example, and as illustrated in  FIGS. 38 and 39 , the tether  122  is comprised of a sheath  122 . 
     To facilitate the serial retraction of the introducer sheath  62  and the expandable sheath  80  out of the body vessel  108  of the patient, when the hemostasis valve  40  is interconnected with the receiving body  120  and the introducer subassembly  38  is axially retracted away from the body vessel  108 , the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  becomes taught about the introducer sheath  62  to pull the sheath hub  72  with the expandable sheath  80  axially out of the body vessel  108  in one continuous motion which results in the serial retraction. As the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  expands from its collapsed condition to its taught position the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is restrained about the introducer sheath  62  as to avoid having to much slack and becoming a nuisance. In other words, the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  supported by the introducer sheath  62  during its transition from its collapsed condition to its taught position. In one embodiment, as illustrated in  FIG. 39 , the introducer subassembly  38  is manually pulled to retract the expandable sheath  80  from the body vessel  108  while pressure is applied to the body  106 . However, it is contemplated that the introducer subassembly  38  could be pulled to be retracted away from the body vessel  108  by a robotic instrument, or any alternative method. 
     As best illustrated in  FIG. 36 , the sheath hub  72  defines a cavity  124  and the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is collapsed and stored within the cavity  124  when the receiving body  120  is connected to the sheath hub  72 . In other words, the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is designed such that in a collapsed state, it can be contained within the cavity  124 . In a preferred embodiment, the sheath hub  72  is u-shaped to define a pair of flanges  126  and the receiving body  120  includes tabs  128  for releasably interlocking to the pair of flanges  126 . These tabs  128  are detachable from the flanges  126  and when the hemostasis valve  40  interconnects with the receiving body  120  and when the hemostasis valve  40  is retracted away from the body  106  the tether  122  pulls on the expandable sheath  80  from the body vessel  108  of the patient. 
     The tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is capable of becoming taught about the introducer sheath  62  and then being collapsed and stored again in the cavity  124  should the introducer subassembly  38  need to be re-advanced into the body vessel  108 . The tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is sized such that when the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  is taught about the introducer sheath  62 , a distal end of the introducer sheath  62  resides within a maximum length of the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622 . In other words, the tether  122 ,  222 ,  322 ,  422 ,  522 ,  622  in its expanded condition has an overall length equal to, or smaller than, the overall length of the introducer sheath  62 . 
     As illustrated in  FIGS. 40 and 41 , a first embodiment of the tether  222  includes a plurality of sheets  130  interconnected with one another in collapsible and expandable accordion fashion. In other words, the tether  222  is collapsible in an accordion fashion to be collapsed and stored within the cavity  124  when the receiving body  120  is connected to the sheath hub  72  and is expandable to establish the taught condition. Each of the plurality of sheets define a hole  223  to collectively define the passageway  132 . The tether  222  is comprised of a film-like material but could be comprised of alternative materials. 
     As illustrated in  FIGS. 42 a  and 42 b   , a second embodiment, of the tether  322  is of a braided material (i.e., a braided tether). In other words, the tether  322  is comprised of strands of material interlaced or braided with one another to define the passageway  132 . When the braided tether  322  is contained within the cavity  124 , the strands of material interlaced with one another will be nearly orthogonal to one another. When the braided tether  322  is taught about the introducer sheath  62 , the strands of material interlaced with one another will be orientated closer to longitudinal to one another. The orientation of the strands of material with one another is proportional to the amount of extension as well as a decrease in an outer diameter of the braided tether  322 . In this way, when the braided tether  322  is taught about the introducer sheath  62 , an inner diameter of the braid tether  322  is equivalent to an outer diameter of the introducer sheath  62  and at this point the braid will no longer extend to allow for the serial retraction of the introducer sheath  62  and the expandable sheath  80 . When the braided tether is taught about the introducer sheath  62 , the strength of the braided tether  322  increases due to friction between the braided tether  322  and the introducer sheath  62  relative to the compressive forces as the result of tension on the braided tether  322 . It is also to be appreciated that a maximum length of the braided tether  322  is such that a distal end of the introducer sheath  62  resides within the maximum length of the tether  322 . 
     As illustrated in  FIGS. 43 a  and 43 b   , a third embodiment of the tether  422  is of a woven material (i.e., a woven tether). In other words, the tether  322  is comprised of a plurality of fibers orthogonally woven together to define the passageway  132 . 
     As illustrated in  FIG. 44 , a fourth embodiment of the tether  522  includes a plurality of rings  134  serially arranged between the sheath hub  72  and the receiving body  120  and each defining an opening  523  for collectively defining the passageway  132  and concentrically receiving the introducer sheath  62  when the introducer sheath  62  is passed through the sheath hub  72  and into the expandable sheath  80 . The plurality of rings  134  are connected to one another by at least one string  136  extending between the sheath hub  72  and the coupler  118  for sliding or pulling the rings  136  along the introducer sheath  62  during relative movement between the introducer subassembly  38  and the expandable sheath  80 . 
     As illustrated in  FIGS. 45 a  and 45 b   , a fifth embodiment of the tether  622  includes at least one cord  138  extending between the sheath hub  72  and the coupler  118 . The at least one cord  138  is spirally wound to define the passageway  132  and to define a series of loops  623 . The at least one cord  138  may include a plurality of cords  138  and the series of loops of one of said cords  138  is secured to the series of loops of the other cords  138  via a connection point  140 . The connection point  140  may be formed by a knot, chemical bond, heat bond, welding, or alternative method. 
     As best illustrated in  FIGS. 32 through 35 , when the expandable introducer assembly  10  includes a coupler  118 , the locking key  184  is disposed in a mating and releasably interlocked relationship with the receiving body  120  of the coupler  118  for establishing the locked condition of the sheath hub  70  and preventing concurrent axial advancement of the introducer subassembly  38  and the dilator  12  relative to the expandable sheath  80 . As discussed above, the locking key  138 ,  184  is also releasably interlocked with the dilator  12  for establishing the locked condition and for preventing concurrent axial advancement of the introducer subassembly  38  and the dilator  12  relative to the expandable sheath  80 . 
     As best illustrated in  FIGS. 46 through 52 , in an additional alternative embodiment of the expandable introducer assembly  10 , a casing  142  extends between a proximal casing end  144  disposed in abutting relationship with the hemostasis valve  40  and a distal casing end  146  disposed in mating and releasably interlocked relationship with the receiving body  118 . The casing  142  prevents concurrent axial advancement and rotational misalignment of the introducer subassembly  38  and said dilator  12  relative to said expandable sheath  80  and replaces the locking key  184  for establishing the locked condition of the sheath hub  72 . The casing  142  is disposed in encasing relationship with the introducer sheath  62  and defines a trough  148  extending between the proximal and distal casing ends  144 ,  146  for receiving a lubricant to lubricate the introducer sheath  62  prior to its introduction into the expandable sheath  80 . In a preferred embodiment the trough  148  is defined as a u-shaped channel that is open along a top portion and extends between the proximal and distal ends  144  for receiving the introducer sheath  62  and holds the lubricant therein during the encasing relationship between the casing  142  and the introducer sheath  62 . The casing  142  defines an orifice  150  in fluid communication with the trough  148  to allow a fluid to be introduced through the orifice  150  and into the trough  148  to lubricate the introducer sheath  62  prior to axial advancement through the sheath hub  72  into the expandable sheath  80 . The casing  142  also defines a handle portion  156  adjacent the distal casing end  146  for allowing gripping of the handle portion  156  during the initial insertion of the expandable introducer assembly  10 . 
     The casing  142  may include a clamp  152  hinged to the distal casing end  146  and pivotable from an open position ( FIG. 52 ) to a closed position ( FIG. 51 ) for establishing the mating and releasably interlocked condition with the receiving body  120 . In a preferred embodiment, the clamp  152  defines the orifice  142  for being pivoted into fluid communication with the trough  148  when the clamp  152  is disposed in the closed position. The introducer sheath  62  may include a hydro-coating which is activated by the lubricant (e.g., saline) when the lubricant is introduced through the orifice  142  and into the trough  148 . It is to be appreciated that the introducer sheath  62  may be lubricated by alternative means. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.