Patent Document

CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority of provisional application Ser. No. 61/001,019, filed Oct. 30, 2007. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a haemostatic valve for use, for example, in an introducer or deployment device of the type employed for delivering and deploying stents, stent grafts, vena cava filters, occlusion devices and other implants and prostheses into a lumen or organ of a patient. The introducer or deployment device can also be of a type used for diagnosis as well as for the carrying out of medical procedures and treatments. 
       BACKGROUND OF THE INVENTION 
       [0003]    Examples of such valves can be found, for instance, in U.S. Pat. No. 4,673,393, U.S. Pat. No. 5,176,652 and US-A-2005/017,479. 
         [0004]    A difficulty arises with the use of such a series of seals, however, in that in order to have good sealing characteristics they also tend to create a significant resistance to movement of an insert therein, which can substantially impair the operability of the insert by making it too hard to slide within the sheath. This can in some instances lead to damage of the insert, for example by kinking. This risk is particularly acute for inserts which are by necessity very flexible or of a small diameter. 
         [0005]    In order to mitigate the above disadvantages, it is also known to use a haemostatic valve which can be opened and closed under the clinician&#39;s control. This has the advantage that an element can be inserted into the sheath and moved therealong with relative ease while the controllable haemostatic valve is in an open configuration. Once the insert is in place the valve can be tightened to seal. Such tightening is also advantageous during the procedure of insertion of the device into the sheath assembly. In practice, it is often necessary for such a solution also to include a valve which self-seals, such as one or more of the disk-shaped valves mentioned above to secure sealing during handling. 
         [0006]    Such selectively openable and closable valve elements typically have an elongate valve member of tubular form which can be closed by twisting or by application of pressure laterally on the valve element by means of one or more movable closing plates. 
         [0007]    U.S. Pat. No. 4,673,393, U.S. Pat. No. 5,176,652 and U.S. Pat. No. 6,981,996 disclose valve assemblies which include substantially planar valve elements of disc-shape with a number of slits therein. An insert, such as a pusher, dilator or other elongate element, can pass through the slit or slits and into the sheath of the deployment of the device. When such inserts are removed, the slits close in order to close the valve element. 
         [0008]    There are a number of compromises with such valve elements. When an insert is passed through the valve to open the slits, the seal is no longer fluid tight, with the result that there can be leakage through the valve element. This problem can be mitigated by designing a valve element with an increased closure pressure, whereby the edges of the slit or slits push tightly against the insert so as to close around this to reduce leakage paths. However, increasing closure pressure increases the effective friction between any item inserted within the valve and the valve itself, which can make it harder to slide any insert through the valve. Such additional friction can also cause damage to any insert held therewithin and potentially cause damage to the valve itself. It will be appreciated that if such damage occurs in the middle of a medical procedure this can be highly disadvantageous, at worst resulting in an abortive procedure. 
         [0009]    As explained above, attempts have been made to try to resolve the problem with such valves by providing a plurality of valves in series, with the slit or slits of each valve element being rotated relative to one another so as to provide a more effective seal. However, even though this might improve the sealing characteristics of the valve, it does not satisfactorily deal with the problem of increased pressure on or friction against the insert held therewithin. 
         [0010]    US-A-2005/0,171,479 discloses a different type of valve element which is formed of an elongate tubular member which can be twisted so as to fold into a closed position at its centre. The material forming the valve element is sufficiently flexible that it can wrap itself around an insert held within the valve, thereby to provide the required seal. This type of valve has the advantage that when the valve element is opened, that is when it is in an untwisted state, it provides no or substantially no friction on an insert held therewithin. Of course, in practice it is necessary to provide additional sealing/valve elements. It is, for example, known to add disc-shaped seals of the type described above. In US-2005/0171479, for example, there are provided three disc-shaped seals in addition to the twistable cylindrical seal. 
         [0011]    Another twistable seal is disclosed in US-2004/078586 
         [0012]    An additional problem with the twistable seals disclosed in US-2005/0171479 and US-2004/0178586 is that the sealing efficiency of these seals is determined by the depth of the seal in the longitudinal direction of the valve, in practice the depth of the seal which comes into contact with the outer walls of the insert. This can be seen for example in FIG. 24 of US-A-2005/0171479 and in FIG. 2 of US-A-2004/0178586, in which only a small portion of the twistable valve element contacts the insert, thus providing a relatively narrow seal. A narrower seal provides less sealing effect and often also requires the provision of additional seals, such as the disc-shaped seals used in the device of US-A-2005/0171479. 
         [0013]    Therefore, these twistable seal elements do not mitigate all of the disadvantages of haemostatic seals. 
         [0014]    Another valve element for use in such deployment devices and also for endoluminal medical procedures includes a flexible valve element provided with two facing leaflets which are able to contact one another when the valve is closed so as to provide a seal. Particularly, one end of the valve element keeps the leaflets open, for example by provision of a support element holding to the two leaflets apart. At the other, free end, the leaflets can be made to contact one another when the valve is in a closed configuration, for example by sealing the side edges of the leaflets together.  FIG. 1  shows a cross sectional view of an example of such a two-leaflet valve, in which an insert is located within the valve, causing the two leaflets to open. 
         [0015]    A problem with this type of valve, as can be seen in  FIG. 1 , is that the valve element is unable to close well around the insert, leaving large apertures allowing leakage of fluid through the valve leaflets. 
       SUMMARY OF THE INVENTION 
       [0016]    The present invention seeks to provide an improved valve, in particular a haemostatic valve. 
         [0017]    The present invention also seeks to provide an improved introducer or deployment device. 
         [0018]    According to an aspect of the present invention, there is provided a valve element formed of at least three elongate flexible leaflets arranged so as to provide a polygonal passage therebetween when the valve element is in an open configuration, the leaflets being able to close in on one another along at least a portion thereof, thereby to provide a seal. 
         [0019]    Advantageously, the leaflets are sealed to one another along adjacent longitudinal sides thereof. It is envisaged that the leaflets could be sealed to one another by bonding, welding or during fabrication of the valve. For example, the valve could be formed as a unitary structure, for example by extrusion, vacuum or flow moulding. 
         [0020]    In the preferred embodiment, there are provided three leaflets. 
         [0021]    Advantageously, the leaflets extend along a major portion of the length of the valve. Most preferably, the leaflets extend for substantially the entire length of the valve. 
         [0022]    In the preferred embodiment, the valve has a waisted or hourglass configuration. 
         [0023]    The valve may be formed of a compliant or non-compliant material. The valve may be made of polyurethane, silicon, polychloroprene (Neoprene), styrene Butadiene, styrene ethylene Butadiene, latex, a rubber or rubber-like material. 
         [0024]    In another embodiment, the valve is made of a non-compliant material, for example polyethylene terephthalate (PET), polyethylene, nylon, a plastics is material, or any other relatively non-compliant material known in the art. 
         [0025]    The valve may be provided with a hydrophilic coating, which has the advantage of reducing function and of filling any sealing gaps. 
         [0026]    According to another aspect of the present invention, there is provided a medical treatment device, an introducer or deployment device including a valve element as specified herein. 
         [0027]    According to another aspect of the present invention, there is provided a valve assembly including a valve element as herein specified and means for configuring the valve element into a closed configuration. 
         [0028]    Preferably, the configuring means includes a pressurisable chamber within which the valve element is located, pressurization of the chamber causing the valve leaflets to close onto one another, thereby to seal the valve. 
         [0029]    In another embodiment, the configuring means includes a twisting element operable to twist and thereby to close the valve. 
         [0030]    According to another aspect of the present invention, there is provided a valve element formed of at least two leaflets arranged so as to provide a passage therebetween when the valve element is in an open configuration, the leaflets being able to close in on one another along at least a portion thereof, thereby to provide a seal; wherein the valve element is formed of a substantially non-compliant material. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0031]    Embodiments of the present invention are described below, by way of example only, with reference to the accompanying drawings, in which: 
           [0032]      FIG. 1  shows in schematic form a cross-sectional plan view of an example of prior art two-leaflet valve; 
           [0033]      FIG. 2  is a schematic view of an embodiment of tri-leaflet valve, shown in cross-section; 
           [0034]      FIG. 3  is a front elevational view of a preferred embodiment of tri-leaflet valve; 
           [0035]      FIG. 4  is a plan view of the valve of  FIG. 3 ; 
           [0036]      FIG. 5  is a schematic view of an embodiment of valve element which is pre-twisted; 
           [0037]      FIG. 6  is a schematic view of a part of the valve element of  FIG. 5  closed around an insert; 
           [0038]      FIG. 7  is a schematic diagram of an embodiment of valve assembly; 
           [0039]      FIG. 8  is a cross-sectional view of the assembly of  FIG. 5  showing the valve element at its waist portion in a condition in which it has been pressurized to close; and 
           [0040]      FIG. 9  is a schematic diagram of another embodiment of valve assembly. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0041]    Referring to  FIG. 2 , this shows in schematic form a cross-sectional view of an embodiment of tri-leaflet valve  10 , taken substantially perpendicularly to the longitudinal direction of the valve element  10  and at a centre portion of the valve element. The valve  10  is shown in an unbiased condition, that is without being pressed or otherwise biased to force the material forming valve leaflets  14  to seal onto an insert  16 . 
         [0042]    Before explaining in detail the features of the valve  10 , it is useful to point out some of its main characteristics. A comparison of  FIGS. 1 and 2  will show that the example of tri-leaflet valve  10  shown in  FIG. 2  provides gaps  12  between the leaflets  14  and the insert  16  which in total area are much smaller than the gaps existing with a two-leaflet valve. Moreover, in light of the fact that two adjacent leaflets  14  of a tri-leaflet valve  10  are required to cover a smaller arc or radial area of the insert  16  held within the valve, the leaflets  14  can seal better than in the case of a two-leaflet valve where the two adjacent leaflets Must, at either side, cover 50% of the insert held therewithin. 
         [0043]    It is not ruled out that the valve  10  could have more than three leaflets, such as 4, 5 or 6. However, increasing the number of leaflets in the valve increases the amount of material of the leaflets of the valve  10  which contacts the insert  16  even when the valve  10  is in a not fully sealing or open condition as shown in  FIG. 2 . This can increase the friction between the valve  10  and the insert  16  during periods in which it is desired to slide the insert into and out of the valve  10 . In this regard, it has been found that a tri-leaflet valve provides the best combination of characteristics of sealing and low friction and is thus the preferred option. 
         [0044]    The shape of the valve  10  can take a variety of forms, the preferred of which is shown in  FIGS. 3 and 4  and described in further detail below. In one embodiment, the three leaflets  14  are substantially rectangular along their lengths such that the valve element  10  is substantially cylindrical throughout its length. It may be triangular in axial cross-section but is preferably formed such that each leaflet  14  tends naturally to curve inwardly towards the centre of the valve element  10 , shown in  FIG. 2 . This curvature of the leaflets  14  can be achieved by stretching the apices  18  at the junctions between two adjacent leaflets  14 , in a direction away from the central axis of the valve  10 . In an alternative, the valve  10  can be formed to have this shape when in a relaxed condition. 
         [0045]    The material forming the leaflets  14  could be any suitable material, the preferred being polyurethane, silicon, polychloroprene (Neoprene), styrene Butadiene, styrene ethylene Butadiene, latex, a rubber or rubber-like material. The leaflets  14  can be formed as a single layer of material but in some instances could be multilayered. 
         [0046]    It is preferred that the internal surfaces of the leaflets  14  are provided with a hydrophilic coating of a suitable type. This has the advantage of reducing friction between the valve leaflets  14  and an insert  16  and can also, as a result of the conformability of such hydrophilic coatings, assist in filling in any gaps  12  between the valve  10  and the insert  16  so as to optimize the sealing effect. 
         [0047]    As will be apparent in  FIG. 2 , for example, it is preferred that the valve  10  has a minimum open diameter which substantially contacts an insert  16  intended to be held therewithin. This is not, however, a requirement of the valve  10  as this could also work more than satisfactorily with inserts of smaller diameter than the insert  16 , as well as inserts larger than the insert  16  shown in  FIG. 2 , in which case the leaflets  12  would be biased outwardly from the centre of the valve when such an insert is located therewithin. 
         [0048]    The size of the valve  10  and the thickness of the valve leaflets  14 , as well as the shape of valve  10 , are preferably chosen to provide an optimal balance between: friction between the valve  10  and any insert  16 , and sealing strength when the valve  10  is closed. As explained above, the provision of three leaflets  14  is considered the optimal solution. 
         [0049]    The valve  10  is preferably of a type intended to be used in an introducer or delivery device used, for example, in delivering stents, stent grafts, vena cava filters, occlusion devices and other implants and prostheses endoluminally into a patient, as well as for devices for effecting endoluminal treatments and diagnosis. Thus, the valve is preferably a haemostatic valve and the element  16  held within the valve can be a pusher, dilator, catheter or any other elongate medical device. 
         [0050]    Referring now to  FIGS. 3 and 4 , there is shown a preferred embodiment of valve  100  to be used as a haemostatic valve in a deployment or delivery device of the type discussed above. In this embodiment, the valve  100  has three elongate leaflets  102  which are connected to one another in sealed manner along their adjacent edges  104 . 
         [0051]    The leaflets  102  can be sealed to one another after being formed, for example by bonding or welding. In another embodiment, the valve  100  is formed as a unitary structure with the three leaflets and can be manufactured in this form by extrusion, by moulding, such as vacuum or blow moulding, or in any other suitable way. The valve is formed such that it is preferably fluid tight when in use, that is the connections between the leaflets  102  are fluid tight. 
         [0052]    As can be seen in  FIG. 3 , this embodiment of valve  100  has a waist  106 , which may be formed as a result of shaping the leaflets of the valve so as to narrow gradually towards their centre points or by stretching the top and bottom edges of the valve  100  radially outwardly and holding these in their stretched conditions by suitable fixing to a valve element housing  FIGS. 6 and 7 . 
         [0053]    In  FIG. 3  the waist is shown to be considerably narrower than the ends of the valve  100 , although the degree of reduction in the valve diameter from its ends to its centre can be chosen by the skilled person and is dependent upon the application and the sealing characteristics required for the valve  100 . For example, in some instances it may be preferable to have a valve which is substantially cylindrical, that is with a very shallow waist  106 , whereas in other instances it may be preferable for the valve  100  to have a more pronounced waist  106 , for example as shown in  FIGS. 3 and 4 . 
         [0054]    As can be seen in  FIG. 4 , the waist  106  provides a relatively narrow passage  108  in the middle of the interior of the valve  100 , formed by the three leaflets  102 . This passage  108  is equivalent to the arrangement shown in  FIG. 2  and discussed above. 
         [0055]    The valve  100  may typically be made of polyurethane, silicon, rubber, polychloroprene (Neoprene), styrene Butadiene styrene ethylene Butadiene, latex, a rubber like material. 
         [0056]    In another embodiment, the valve  100  could be made of a relatively non-compliant material, for example of the type used for dilatation, angioplasty or other balloons of low compliance. Suitable materials include polyethylene terephthalate (PET), polyethylene, nylon, PVC or any other suitable materials known in the art. Such materials can, because of their flexibilities, provide good sealing in such a valve element and exhibit low friction. 
         [0057]    As with the embodiment of  FIG. 2  the valve  100  could be provided with a hydrophilic coating on its internal surfaces and could also be formed of multi-layered leaflets. 
         [0058]    The valve  100  exhibits the advantages discussed above in connection with  FIG. 2 . 
         [0059]    Referring now to  FIGS. 5 and 6 , there is shown another embodiment of valve element  100 ′. This valve element  100 ′ has all of the characteristics and alternatives described in connection with the valve elements described above but differs in being pre-twisted. That is, the valve  100 ′ has an unbiased shape which is twisted in its longitudinal direction by, in this embodiment, around 120° from one end of the valve  100 ′ to the other. The amount of twist can be different and the optimum can be determined by trial and error. It is considered that a twist of 60° to 180° is optimal but could be more or less than these. The valve  100 ′ could be twisted in this manner in any of a number of ways, such as by twisting during extrusion or by suitable shaping in a mould. 
         [0060]    A pre-twisted shape to the valve  100 ′ facilitates the collapse of the valve leaflets  102 ′ towards the sealed configuration and thus facilitates the formation of a good seal. 
         [0061]      FIG. 6  shows an enlarged view of a portion of valve  100 ′ sealed against insert  16 ′. 
         [0062]    The leaflets of this valve and of the other valves disclosed herein could be of a type in which they collapse and/or overlap thus to seal without an insert in the valve. 
         [0063]    Turning now to  FIG. 7 , there is shown an embodiment of valve assembly  200  including therewithin a tri-leaflet valve element  100  of the type shown in  FIGS. 3 and 4  or of the type shown in  FIGS. 5 and 6 . The assembly  200 , in this embodiment, includes a casing  202  having openings  204 ,  206  at either end. The valve  100  is sealed to the casing  202  so that each end of the valve  100  envelops one of the openings  204 ,  206 , so as to provide a channel passing through the centre of the assembly  200 , for the passage of an element  16  of the type shown in  FIG. 2  and discussed in connection therewith. 
         [0064]    The casing  202  is provided with a port  208  for the supply of pressured fluid  210  into the chamber  212  which surrounds the outside of the valve element  100 . Application of pressurized fluid into the chamber  212  causes the valve leaflets of the valve  100  to be pressed towards the centre of the casing  202  and thereby to constrict the passage between the two openings  204 ,  206 , in other words to compress the central aperture  108  of  FIG. 4 . This has the effect of closing the valve element  100  into a sealing configuration. When an insert  16  is placed within the valve assembly  200 , passing through the openings  204  and  206 , pressurization of the chamber  212  causes the leaflets  102  to compress onto the element  16  and to seal either side of that element  16  as will be apparent from the cross-sectional view of  FIG. 8 . For this purpose, the leaflets  102  are such that they can fold easily onto one another and also onto any insert  16  placed within the valve  100 . In this way, a reliable seal can be achieved with the valve  100 . 
         [0065]    Further details of the valve assembly  200  are disclosed in the applicant&#39;s co-pending United States provisional patent application filed on 30 Oct. 2007 and having the No. 61/001,018, as well as the United States patent application being filed claiming priority therefrom. 
         [0066]      FIG. 9  shows in schematic form another embodiment of valve assembly  300  in which the valve  100  is supported by first and second support members  302 ,  304  which may be part of a casing  310  for the valve  100 . Such casing can be any suitable casing which encloses the valve  100 , for example one similar to that disclosed in US-2005/0171479 discussed above. The supports  302  and  304  can be rotated relative to one another (typically, one is rotated while the other is stationary), in the direction of the arrow  306 , for example. Such rotation causes the valve  100  to twist, with such twisting action causing the leaflets to close the passage  108  therebetween. 
         [0067]    As with the embodiment of  FIG. 7 , the connecting elements  302 ,  304  have apertures therein (not visible in  FIG. 9 ) such that an element  16 , can be inserted into and through the valve  100 . 
         [0068]    The fact that the valve is formed of a plurality of leaflets  102 , as shown in the Figures, in which the leaflets can touch and be very close to the insert  16  held within the valve element, has the effect of causing the leaflets  102  to form a seal of substantial depth, in the example of  FIG. 5  or  7  being approximately the length D. Of course, this depth is dependent upon the nature of the waist  106  of the valve  100  and the size of an insert  16  held is within the assembly  300  and passing through the valve  100 . It will be appreciated that the depth of the seal produced by a multi-leaflet valve of the type disclosed herein is substantially greater than that provided by prior art valves, such as those disclosed in US-2005/0171479 and US-2004/0178586. This gives a substantially enhanced seal. 
         [0069]    It is also envisaged that the valve could be made of polyvinyl acetate (EVA).

Technology Category: 1