Vascular introducer sheath and hemostasis valve for use therewith

A vascular introducer sheath including a tubular shaft and a hemostasis valve assembly connected to the proximal end thereof. The hemostasis valve assembly includes a hub, a cap and a normally-flat gasket disposed therebetween. Both the hub and the cap include continuous curved contact surfaces facing the top and bottom surfaces of the gasket. The continuous contact surfaces may be flat or gently curved and may be smooth or include a means to grip the gasket. At least one of the contact surfaces is formed at an angle to cause the gasket to become convex or concave in response to compression between the hub and the cap. The continuous contact surfaces uniformly distribute forces onto the perimeter of the gasket to avoid stress concentration points that may compromise gasket integrity. In addition, the continuous contact surfaces reduce the amount of pressure necessary to impart the curved shape of the gasket.

FIELD OF THE INVENTION
 The present invention generally relates to introducer sheaths for use in
 procedures requiring vascular access. More specifically, the present
 invention relates to hemostasis valves for use in such introducer sheaths.
 BACKGROUND OF THE INVENTION
 Vascular introducer sheaths are well known components of vascular access
 systems which are used in a wide variety of diagnostic and therapeutic
 vascular procedures, such as angiography, angioplasty, thermolysis and
 embolization procedures. Vascular access systems typically include an
 introducer sheath for use in combination with a guide wire and a dilator.
 The introducer sheaths usually include a hemostatic or hemostasis valve
 which inhibits blood loss as guide wires, catheters and the like are
 introduced and manipulated in the vasculature via the sheath.
 An example of a known hemostasis valve is disclosed in U.S. Pat. No.
 5,520,655 to Davila et al. Davila '655 discloses a hemostasis valve
 including an inner housing, an end cap and a valve partition disposed
 between the inner housing and the end cap. The end cap includes a
 compression ring having a diameter which is less than the diameter of the
 valve partition but greater than the diameter of the aperture in the end
 cap and the bore in the inner housing. With this arrangement, the
 compression ring causes the valve partition to bow outwardly. Purportedly,
 the bowing enhances the sealing of the slit in the valve partition.
 However, the compression ring creates stress concentration points on the
 valve partition that may compromise the integrity of the valve partition.
 Furthermore, an excessive amount of compression must be applied by the
 compression ring against the valve partition to impart the bowing effect.
 A similar hemostasis valve is disclosed in International Patent Publication
 No. WO 99/06099 to Paul. Paul '099 discloses a hemostatic valve including
 a gasket seal contained in a valve body and compressed therein by a cap
 connected to the valve body. The valve body includes a valve seat, which
 in turn includes a flange and a series of annular recessed steps. The
 flange serves to impart a concave shape to the gasket seal. The series of
 annular steps serve to prevent the gasket seal from being displaced. As
 with the hemostasis valve disclosed in Davila '655, the hemostasis valve
 disclosed in Paul '099 suffers from the creation of stress concentration
 points imparted by the flange onto the valve gasket. The annular steps
 recessed in the valve body, depending on the size, may also create stress
 concentration points on the gasket seal. These stress concentration points
 may compromise the integrity of the gasket seal and also require an
 excessive amount of compression to impart the desired curved shape of the
 gasket seal.
 SUMMARY OF THE INVENTION
 The present invention overcomes these disadvantages by providing, in an
 exemplary embodiment, a vascular introducer sheath for use with a vascular
 access system. The vascular introducer sheath includes a tubular shaft and
 a hemostasis valve assembly connected to the proximal end of the tubular
 shaft. The hemostasis valve assembly includes a hub, a cap and a gasket
 disposed therebetween. The gasket may be normally-flat and may have at
 least one normally-closed slit extending therethrough.
 Both the hub and the cap include continuous contact surfaces facing the top
 and bottom surfaces of the gasket. The continuous contact surfaces may be
 flat or gently curved, and may be smooth or include a means to grip the
 gasket. At least one of the contact surfaces forms a non-orthogonal angle
 with the longitudinal axis of the assembly to cause the gasket to become
 curved in response to compression between the hub and the cap. The
 continuous contact surfaces uniformly distribute forces onto the perimeter
 of the gasket to avoid stress concentration points that may compromise
 gasket integrity. In addition, the continuous contact surfaces increase
 the contact surface area and thereby reduce the amount of pressure
 necessary to impart the desired curved shape of the gasket.

DETAILED DESCRIPTION OF THE INVENTION
 The following detailed description should be read with reference to the
 drawings in which similar elements in different drawings are numbered the
 same. The drawings, which are not necessarily to scale, depict
 illustrative embodiments and are not intended to limit the scope of the
 invention.
 Refer now to FIG. 1 which illustrates a plan view of a vascular access
 system 10 in accordance with the present invention. Vascular access system
 10 includes two primary components, namely an introducer sheath 12 and a
 dilator 14. Introducer sheath 12 includes an elongate shaft 16 and a
 hemostasis valve assembly 18. The hemostasis valve assembly 18 is
 connected to the proximal end of the shaft 16 utilizing conventional
 techniques. Hemostasis valve assembly 18 includes a hub, a cap and a
 gasket disposed therebetween as will be described in greater detail with
 reference to FIGS. 2-4. The hub of the hemostasis assembly 18 may include
 a side port 19 for connection to a flush or injection tube subassembly 20.
 The shaft 16 of the introducer 12 may have a size (outside diameter or
 profile) ranging from 4F to 9F, and a length ranging from 10 cm to 25 cm.
 The distal tip of the elongate shaft 16 is preferably tapered to
 facilitate smooth insertion into the vascular system and smooth transition
 to the dilator 14.
 Refer now to FIGS. 2A and 2B which illustrate cross-sectional side views of
 hemostasis valve assemblies 18 for use with the introducer sheath 12
 illustrated in FIG. 1. As mentioned previously, the hemostasis valve
 assembly 18 includes a hub 22, a cap 24 and a gasket 26 disposed
 therebetween. For purposes of simplicity and clarity, the side port 19 of
 the hub 22 is not illustrated. Similarly, although not illustrated for
 purposes of simplicity and clarity, the hub 22 and the end cap 24 include
 a means for compressive connection therebetween, such as a snap-fit
 connection or a threaded connection, both of which are well-known in the
 art.
 The hub 22 includes an inner lumen 28 extending therethrough, and the end
 cap 24 includes an aperture 30 extending therethrough. The inner lumen 28
 of the hub 22 is in fluid communication with the aperture 30 of the end
 cap 24 absent the gasket 26, which includes one or more slits (not shown)
 discussed in more detail with reference to FIGS. 5, 6A and 6B. The hub 22
 and the end cap 24 may have conventional dimensions and may be formed of
 conventional materials using known manufacturing techniques.
 Hub 22 includes a continuous surface 32 which is in intimate contact with
 the bottom surface 34 of the gasket 26. Similarly, the end cap 24 includes
 a continuous surface 36 in intimate contact with the top surface 38 of the
 gasket 26. The continuous contact surfaces 32, 36 may be flat or gently
 curved and may be smooth or include a means to grip the gasket as
 described with reference to FIGS. 3 and 4.
 Both the surface 32 of the hub 22 and the surface 36 of the end cap 24
 define a line 41 that is tangent to the surface. If a curved surface is
 used, the tangent line 41 may be taken at the cross-sectional mid-point of
 the curved surface. Either the tangent line 41 of surface 32 or the
 tangent lines 41 of both surfaces 32, 36 may be formed at an angle 40 with
 the longitudinal axis 42 of the assembly 18. The angle 40 is
 non-orthogonal (i.e. acute or obtuse) such that the gasket 26 becomes
 curved in response to compression between the hub 22 and the end cap 24.
 as seen in FIGS. 2A and 2B, the surface 32 of the hub 22 and the surface
 36 of the cap 24 define a contact area with the gasket 26. The continuous
 contact surface 32 of the hub 22 and the continuous contact surface 36 of
 the cap 24 have parallel contact angles as illustrated by tangent lines 41
 and angles 40, which are the same throughout the contact area of the
 gasket 26 with the hub 22 and the cap 24.
 The continuous surfaces 32, 36, which may be flat or gently curved,
 uniformly distribute forces onto the bottom and top surfaces 34, 38 to
 avoid stress concentration points that may otherwise compromise the
 integrity of the gasket 26. In addition, the continuous contact surfaces
 32, 36 increase the contact surface area and thereby reduce the amount of
 pressure between the hub 22 and the end cap 24 necessary to impart the
 desired curved shape of the gasket 26.
 As illustrated, in FIG. 2A the continuous surfaces 32, 36 form an acute
 angle 40 with the longitudinal axis 42 such that the top surface 38 of the
 gasket 26 assumes a convex shape. Alternatively, as illustrated in FIG. 2B
 the continuous surfaces 32, 36 may form an obtuse angle 40 with the
 longitudinal axis 42 such that the top surface 38 assumes a concave shape.
 As mentioned previously, it is only necessary that the surface 32 of the
 hub 22 is formed at an angle 40 with the longitudinal axis 42 in order to
 impart a curve on the gasket 26. However, both the surface 32 of the hub
 and the surface 36 of the end cap 24 may be formed at an angle 40 to cause
 the gasket 26 to assume a curved shape. If both surfaces 32, 36 are formed
 at an angle 40, the angles are preferably the same but may be different.
 Refer now to FIG. 3 which illustrates a cross-sectional side view of an
 alternative hemostasis valve assembly 48 for use with the introducer
 sheath 12 illustrated in figure 1. Except as specifically described
 herein, hemostasis valve assembly 48 is the same in form and function as
 hemostasis valve 18. In this embodiment, the end cap 24 includes a
 non-orthogonal continuous surface 36 as described previously, and a flat
 surface 37 that is orthogonal to the axis 42. By providing an orthogonal
 flat surface 37, the gasket 26 is less likely to be displaced from the
 recess formed between the hub 22 and the end cap 24. Accordingly, the
 combination of an orthogonal flat surface 37 and a nonorthogonal
 continuous surface 36 retains the gasket 26 between the hub 22 and the end
 cap 24 while guide wires, catheters and the like are advanced or retracted
 through the hemostasis valve assembly 48. In other words, the orthogonal
 flat surface 37 combined with the non-orthogonal flat surface 36 comprises
 a means to retain the gasket 26 between the hub 22 and the end cap 24.
 Refer now to FIG. 4 which illustrates a cross-sectional side view of
 another alternative hemostasis valve assembly 58 for use with the
 introducer sheath illustrated in FIG. 1. Except as specifically described
 herein, hemostasis valve 58 is the same in form and function as hemostasis
 valve assembly 18. For purposes of simplicity and clarity, the gasket 26
 is not illustrated in FIG. 4. It should be understood, however, that the
 gasket 26 is disposed between the hub 22 and the end cap 24 as described
 previously.
 In this particular embodiment, the continuous surfaces 32, 36 of the hub 22
 and the end cap 24, respectively, include an annular protrusion 44 to grip
 the gasket 26. Annular protrusion 44 preferably has a relatively low
 profile of less than approximately 0.010" to minimize or avoid creating
 stress concentration points on the gasket 26. It is believed that the
 annular protrusions 44 do not contribute to curving the gasket 26, but
 merely retain the gasket between the hub 22 and the cap 24. Accordingly,
 annular protrusions 44 comprise means to retain the gasket 26 between the
 hub 22 and the cap 24.
 Those skilled in the art will recognize that other means may be employed to
 grip the gasket 26. For example, a series of small knobs or ridges may be
 utilized. Alternatively, the contact surfaces 32, 36 may be provided with
 a coating having a high coefficient of friction or other roughened surface
 treatment. However, it is to be understood that protrusions 44 and other
 suitable means for gripping the gasket 26 preferably do not significantly
 compromise the flatness or gentle curvature of the contact surfaces 32, 36
 engaging the gasket 26. These protrusions and other means to grip the
 gasket 26 merely increase resistance to displacement of the gasket 26
 relative to the hub 22 and the end cap 24, but do not result in stress
 concentration or focal points that may otherwise compromise the integrity
 of the gasket 26.
 Refer now to FIG. 5 which illustrates an isometric perspective view of the
 gasket 26 for use with any of the hemostasis assemblies 18, 48, 58
 illustrated in FIGS. 2-4. Gasket 26 includes a flat top surface 38 and a
 flat bottom surface 34 as described previously. Gasket 26 is normally flat
 such that the gasket 26 assumes a flat, disk shape 5 when not in
 compression. The gasket 26 may be formed of a variety of elastimeric
 materials such as PDMS, latex or other suitable material. Preferably, the
 gasket 26 has a durometer in the range of 15A-50A. The gasket 26 thickness
 may range from approximately 0.045 to 0.075 inches and may have an outside
 diameter ranging from 0.050 to 0.150 inches to snugly fit in the recess of
 the cap 24. The gasket 26 may be punched out of a sheet of elastimeric
 material or molded using conventional techniques. A slit 46 may be punched
 through the gasket 26 using a three-edged cutter or other suitable
 geometry, depending on the desired number and shape of the slits. Those
 skilled in the art will recognize that the dimensions, materials and
 methods of manufacture may be readily modified without departing from the
 scope or spirit of the invention.
 Refer now to FIGS. 6A and 6B which illustrate cross-sectional views of the
 gasket 26 shown in the normal (relaxed) state 26A and the curved
 (compressed) state 26B, respectively. The normally flat gasket 26A
 illustrated in FIG. 6A includes a slit 46 that is normally closed.
 Specifically, the slit 46 is normally closed at the top surface 38 and the
 bottom surface 34 of the gasket 26 such that a fluid tight seal is created
 along the entire length of the slit 46.
 Upon compression, the gasket 26B assumes a curved shape, depending on the
 degree of compression and the angle 40 of the contact surfaces 32, 36. For
 purposes of illustration only, the top surface 38 is shown to have a
 convex shape and the bottom surface 34 is shown to have a concave shape.
 The surface that assumes the convex shape creates an opening 52 while an
 enhanced fluid tight seal 54 is created along the concave surface. The
 opening 52 on the convex surface allows for easy insertion of a guide
 wire, catheter or the like, particularly when incorporated onto the top
 surface 38 of the gasket 26. The enhanced fluid tight seal 54 on the
 concave surface inhibits the egress of blood through the gasket 26.
 The size of the opening 52 and the amount of compression at the seal 54
 depends in part on the degree of curvature of the gasket 26. The curvature
 of the gasket 26 may be adjusted by changing the angle 40 or the amount of
 compression to impart the desired size of the opening 52 and the desired
 tightness of the seal 54. Thus, the amount of curvature may be adjusted to
 affect device performance in terms of hemostasis (i.e., seal) and
 resistance (i.e., drag) to movement of devices passing therethrough.
 From the foregoing, those skilled in the art will recognize that an
 improved vascular introducer sheath, and in particular an improved
 hemostasis valve assembly has been described. The improved hemostasis
 valve assemblies provide continuous (e.g., flat or gently curved) contact
 surfaces between the gasket and the housing components (i.e., the hub and
 end cap). The continuous contact surfaces distribute forces uniformly onto
 the perimeter of the gasket to avoid stress concentration points that may
 otherwise compromise gasket integrity. In addition, the continuous contact
 surfaces increase the amount of contact area and thereby reduce the amount
 of pressure necessary to impart the desired curved shape of the gasket.
 Those skilled in the art will recognize that the present invention may be
 manifested in a variety of forms other than the specific embodiments
 described and contemplated herein. Accordingly, departures in form and
 detail may be made without departing from the scope and spirit of the
 present invention as described in the appended claims.