Patent Publication Number: US-2020289737-A1

Title: Contactless actuation for valve implant

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 15/878385 filed Jan. 23, 2018; which claims priority to U.S. Provisional Patent Application Ser. No. 62/449,555 filed Jan. 23, 2017, U.S. Provisional Patent Application Ser. No. 62/449,639 filed Jan. 24, 2017, and U.S. Provisional Patent Application Ser. No. 62/453,476 filed Feb. 1, 2017. 
    
    
     BACKGROUND 
     Some medical procedures, require implanted devices. Hemodialysis, for instance, requires vascular access (that is, access to a patient&#39;s vascular system, including veins and arteries). In some cases, vascular access is required over long periods of time and for repeat medical procedures. In such instances, an implant or graft can be placed in the patient to allow for vascular access. One example implant is an arteriovenous (AV) graft, which is a biocompatible tube that links a patient&#39;s artery and vein. The tube has access points for access from outside of the patient&#39;s body. However, the AV graft is constantly open, and thus constantly and unnaturally diverts blood flow between the patient&#39;s artery and vein and vice versa, which can cause complications. 
     SUMMARY 
     An example magnetically activated implantable valve according to the present disclosure includes an implantable valve, the implantable valve including a first set of passive magnets, and an actuator configured to actuate the implantable valve. The actuator includes a second set of passive magnets corresponding to the first set of passive magnets. The first set of passive magnets is configured to interact with the second set of passive magnets to actuate the valve. 
     An example magnetically activated implantable valve according to the present disclosure includes an implantable valve, the implantable valve including a set of passive magnets, and an actuator configured to actuate the implantable valve. The actuator includes a set of active magnets corresponding to the set of passive magnets, wherein the set of passive magnets is configured to interact with the set of active magnets to actuate the implantable valve. 
     An implantable valve for controlling flow of an active fluid according to the present disclosure includes a housing, a driven assembly arranged in the housing; and a driving assembly arranged in the housing and configured to drive the driven assembly by magnetic activation such that the driven assembly compresses or decompresses a reservoir. The reservoir is configured to receive active fluid. One of the driven assembly and the housing includes a keyway and the other of the driven assembly and the housing includes a feature that corresponds with the keyway. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       The various features and advantages of the disclosed examples will become apparent to those skilled in the art from the detailed description. The figures that accompany the detailed description can be briefly described as follows: 
         FIG. 1  schematically illustrates an arteriovenous graft. 
         FIG. 2 a    schematically illustrates an exploded view of a valve with a passive nonlinear magnetic activation scheme. 
         FIG. 2 b    schematically illustrates a magnet. 
         FIG. 3  schematically illustrates an exploded view of a valve with a passive linear magnetic activation scheme. 
         FIG. 4  schematically illustrates an exploded view of a valve with a hybrid nonlinear magnetic activation scheme. 
         FIG. 5  schematically illustrates an exploded view of a valve with a hybrid linear magnetic activation scheme. 
         FIG. 6  schematically illustrates an example valve actuation scheme. 
         FIG. 7  schematically illustrates an alternate example valve actuation scheme. 
         FIG. 8  schematically illustrates an exploded view of the valve actuation scheme of  FIG. 6 . 
         FIG. 9  schematically illustrates an exploded view of a valve in the valve actuation scheme of  FIG. 6 . 
         FIG. 10  schematically illustrates an exploded view of an actuator in the valve actuation scheme of  FIG. 6 . 
         FIG. 11  schematically illustrates an alternate valve actuation scheme. 
         FIG. 12  schematically illustrates an exploded view of the alternate valve actuation scheme of  FIG. 11 . 
         FIG. 13  schematically illustrates a valve showing component dimensions. 
     
    
    
     DETAILED DESCRIPTION 
     Medical devices that are implanted in a patient&#39;s body can require actuation. One example is an arteriouvenous (AV) graft  20 , shown in  FIG. 1 , which is a biocompatible tube that links a patient&#39;s artery  21  and vein  22 . The AV graft  20  provides vascular access for hemodialysis. The AV graft  20  has access points  23  for access from outside of the patient&#39;s body, to connect to a hemodialysis machine. The AV graft  20  has a valve for controlling blood flow through the graft, such as a balloon valve  20   a . The balloon valve  20   a  in an inflated state blocks blood flow through the AV graft, and in a deflated state allows blood to flow through the AV graft  20 . The AV graft  20  also has access points to an active fluid line  26 , which includes a valve  24  (e.g., a driven element). An actuator  25  (e.g., a driving element) actuates the valve externally (from outside the body). The active fluid line  26  receives active fluid, such as saline solution. The valve  24  selectively controls the flow of active fluid, which in turn controls blood flow through the AV graft  20 . That is, the valve  24  can allow blood flow through the AV graft  20  during the hemodialysis procedure, and disallow blood flow at all other times via the actuator  25 . In this way, blood flow between the artery  21  and vein  22  is only allowed when necessary to facilitate hemodialysis, reducing the risk of complications from the unnatural diversion of blood. Though a valve for an AV graft is contemplated, it should be understood that the present disclosure is not limited to AV grafts and can be used in other applications as well. 
     Turning now to  FIGS. 2-5 , an example valve  24  and actuator  25  is shown. The example valve  24  in  FIGS. 2-5  includes a magnetic coupling, by which it is activated in a contactless manner. That is, the valve  24  can be implanted in a patient&#39;s body and the actuator  25  can actuate the valve from outside of the patient&#39;s body. In general, magnetic activation is facilitated by providing a set of magnets on a driven element (e.g., the valve  24 ), the set having an even number of magnets, and a corresponding set of magnets on a driving element (e.g., the actuator  25 ), the corresponding set having the same even number of magnets as in the driven element. The magnetic activation, defined and characterized by the magnets arrangement and design (geometric shape), can be passive linear, passive nonlinear, hybrid linear, or hybrid nonlinear. “Hybrid” means that valve  24  magnets are all passive magnets and actuator  25  magnets are all active magnets. “Nonlinear” means magnets in the valve  24  have a different geometry (and this produce a different magnetic field) than magnets in the actuator  25 . “Linear” means magnets in the valve  24  and actuator  25  have the same geometry. 
     Referring to  FIG. 2 a    , an exploded view of the example valve  24  and actuator  25  are shown.  FIG. 2 a    illustrates a passive nonlinear magnetic activation scheme. The actuator  25  includes passive magnets  30  arranged in a magnetic core  36 . In the example of  FIG. 2 a    , the magnetic core  36  includes four passive magnets  30 , however, in another example, any other even number of passive magnets  30  could be used. The magnetic core  36  is arranged in a nonmagnetic insulator  32  which is covered by a soft magnetic alloy disc  34  at one end. 
     In order to provide magnetic activation, the passive magnets  30  are arranged such that their magnetic field polarities are sequentially in an opposite direction from one magnet  30  to an adjacent magnet  30  in both axial and radial directions. This arrangement allows the passive magnets  30  in the valve  24  to interact with the passive magnets  31  in the actuator  25  (discussed below) and provide magnetic activation of the valve  24 . 
     The valve  24  includes a magnetic core  37  with passive magnets  31  corresponding to the magnetic core  36  in the actuator  25 . That is, the magnetic core  37  in valve  24  has the same number of passive magnets  30  as are in the magnetic core  36 . As in the actuator  25 , the passive magnets  31  are arranged such that their magnetic field polarities are sequentially in an opposite direction from one magnet  31  to an adjacent magnet  31  in both axial and radial directions. This arrangement allows the passive magnets  31  in the actuator  25  to interact with the passive magnets  30  in the valve  24  (discussed above) and provide magnetic activation of the valve  24 . 
     The interaction of the magnets  31  in the valve  24  and the magnets  30  in the actuator  25  due to the magnetic fields oriented as discussed above provides a rotational force and torque on the magnets  30  in the valve  24 , which is sufficient to opens and closes the valve  24  (as will be discussed in more detail below). 
     The magnets  30 ,  31  generally have an arcuate shape (shown in  FIG. 2 b   ) with an internal diameter (ID), an external diameter (OD) and a height (H 1 ). The arcuate shape maximizes the performance of the magnets  30 ,  31  by optimizing the active area of the magnetic activation. In the example of  FIG. 2 a    , the magnets  31  in the valve  24  have a lower height H than the magnets  30  in the actuator  25 . Accordingly, the example of  FIG. 2a  depicts a nonlinear activation scheme. The relatively thinner magnets  31  in the valve  24  allow the entire valve  24  implant to be smaller, which is more comfortable for the patient, and easier to implant. The magnets  30 ,  31  are made of the highest magnetic grade and uniquely designed to minimize the size of the assembly  24 ,  25  for optimal performance and comfort. In one example, the magnets  30 ,  31  have a Maximum Magnetic Energy (BH)max of about 56 MGOe (446 KJ/m3 ) and a Coercive Force (bHc) of about 14.5 kOe (1.154 MA/m). 
     The soft magnetic alloy discs  34 ,  35  are located at the backside of the magnet cores  36 ,  37  active surface, to shield and hold the magnets  30 ,  31 , as well as amplify or enhance the magnetic fields of the magnets  30 ,  31 . The shielding allows for, in one example, shielding of the magnetic field in the implanted valve  24  from imaging techniques such as magnetic resonance imaging (MRI) to reduce or eliminate the effect of the implanted valve  24  on the resulting images. The saturation thickness H sma  of the soft magnetic alloy disks can be estimated using the following correlation: 
     
       
         
           
             
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     In general, the design of the magnets is developed by custom-made magnetic finite element software assisted by at least one industrial/commercial electromagnetic FEA (finite element analysis) software for validation. The custom-made 
     FEA output torque/force is a function of several independent variables depicted by the following function: 
       T(α g , P g , r i , r o , ω, Θ, h i , h o , h si , h so )  
 
     Both T and H sma  (described above) depend on the following variables, with dimensions shown in  FIG. 13 . 
     T: torque 
     a g : air gap 
     Pg: magnets poles gap 
     r i : driven module active/passive magnets radius 
     r o : driving module active/passive magnets radius 
     ω: module rotational speed 
     Θ: poles (pair of active/passive magnets) number 
     h i : driven module active/passive magnets height 
     h o : driving module active/passive magnets height 
     h si : driven module soft magnetic disk thickness 
     h so : driving module soft magnetic disk thickness 
     C te : Constant 
     M: magnetization 
     D o,i : magnets inner and outer diameter 
     N p : number of poles magnets pairs 
     k: complex function of diameters and number of pairs ƒ (D o , D i , N p ) 
     h m,g : heights (gap, magnets . . . ) 
     Δh: Difference of heights 
     i,j: integration step size 
     B max : Saturation Magnetization of the Soft magnetic Alloy 
     In one example, the soft magnetic alloy discs  34 ,  35  properties can have a saturation magnetization of greater than or equal to about 2.4 Tesla. 
     In one example, the magnets  30 ,  31  and the soft magnetic alloy discs  34 ,  35  are coated/plated (e.g., gold-plated) to avoid and/or inhibit any oxidation, corrosion, and/or decay. 
       FIG. 3  illustrates an exploded view of another example valve  24  and actuator  25 .  FIG. 3  illustrates a passive linear magnetic activation scheme. In the Example of  FIG. 3 , the valve  24  includes a magnetic core  46  with two passive magnets  41 , however, in another example, any other even number of passive nonlinear magnets  41  could be used. The magnetic core  46  is arranged in a nonmagnetic insulator  43  which is covered by a soft magnetic alloy disc  45  at one end. The actuator  25  similarly has a magnetic core  47  with two passive magnets  40  corresponding to the magnetic core  46  of the valve  24  arranged in a nonmagnetic insulator  42  and covered by a soft magnetic alloy disc  44  at one end. In this example, the magnets  40 ,  41  in the valve  24  and actuator  25  have the same geometry. Therefore, this example is a linear activation scheme. 
     The magnets  40 ,  41  and soft magnetic alloy discs  44 ,  45  can have the properties and characteristics as described above with respect to magnets  30 ,  31  and soft magnetic alloy discs  34 ,  35  in  FIG. 2   a as discussed above.    
     In the schemes of  FIGS. 2 and 3 , an external drive (such as a motor) rotates the magnets in the actuator  25 , which causes rotation of the corresponding magnets in the valve  24  by way of the magnetic couplings discussed above. 
       FIG. 4  illustrates an exploded view of another example valve  24  and actuator  25  are shown.  FIG. 4  illustrates a hybrid nonlinear magnetic activation scheme. In the example of  FIG. 4 , the valve  24  includes a magnetic core  59  with four passive magnets  53 , however, in another example, any other even number of passive magnets  53  could be used. The magnetic core  59  is arranged in a nonmagnetic insulator  55  which is covered by a soft magnetic alloy disc  57  at one end. The actuator  25  includes a magnetic core  58  with four active magnets  51  corresponding to the four passive magnets  53  in the valve  24 . The active magnets  51  are composed of a soft magnetic alloy core  52  a and a coil  52  b. The coil  52  b characteristics (e.g. number of turns, coil inner diameter, etc.) and the electrical current input are selected to provide suitable magnetic activation for system requirements, and depend on the arrangement and geometry of soft magnetic alloy core  52  a and passive magnets  53 . The magnetic core  58  is arranged in a nonmagnetic insulator  54  and which is covered by a soft magnetic alloy disc  56  at one end. The magnets  51 ,  53 , and soft magnetic alloy discs  56 ,  57  can have the properties and characteristics as described above with respect to magnets  30  and soft magnetic alloy discs  34 ,  35  in  FIG. 2 a    as discussed above. 
     In this example, magnetic activation of magnets  53  in the valve is provided by interaction of the active magnets  51  (e.g., the soft magnetic alloy core  52   a  interacting with the coil  52   b ) in the actuator  25  interacting with the passive magnets  53  in the valve  24 . Accordingly, this example is a “hybrid” activation scheme. 
     Like in the example of  FIG. 2 a   , in the example of  FIG. 4 , the passive magnets  53  have a smaller height than the active magnets  53  in the actuator  25 . Accordingly, the activation scheme in  FIG. 4  is nonlinear. 
       FIG. 5  illustrates an exploded view of another example valve  24  and actuator  25  are shown.  FIG. 5  illustrates a hybrid linear magnetic activation scheme. In the example of  FIG. 5 , the valve  24  includes a magnetic core  68  with six passive magnets  62 , however, in another example, any other even number of passive linear magnets  62  could be used. The magnetic core  68  is arranged in a nonmagnetic insulator  64  which is covered by a soft magnetic alloy disc  66  at one end. The actuator  25  includes a magnetic core  67  with six active magnets  60  corresponding to the six passive magnets  62  in the valve  24 . The active magnets  60  are composed of a soft magnetic alloy core  61  a and surrounded by a coil  61   b . The magnetic core  67  is arranged in a nonmagnetic insulator  63  and which is covered by a soft magnetic alloy disc  65  at one end. The magnets  60 ,  62  and soft magnetic alloy discs  65 ,  66  can have the properties and characteristics as described above with respect to magnets  30 ,  31  and soft magnetic alloy discs  34 ,  35  in  FIG. 2   a as discussed above.    
     In the hybrid schemes of  FIGS. 4 and 5 , a current is provided to the coils in the actuator  25  from an external power source, which induces a magnetic field in the magnets in the actuator  25  and causes movement of magnets in the valve  24  towards and away from the magnets in the actuator  25  by way of the magnetic couplings discussed above. 
     The table below summarizes example magnet dimensions for the magnets discussed in  FIGS. 2-5 . H 1  is the height of the magnets in the valve  24  or actuator  25 , and H 2  is the height of the soft magnetic alloy discs  65 ,  66 . 
     
       
         
           
               
               
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Sample 
                 Magnets in Actuator 25 
                 Magnets in Valve 24 
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Model 
                 ID(mm) 
                 OD(mm) 
                 H 1 (mm) 
                 H 2 (mm) 
                 ID(mm) 
                 OD (mm) 
                 H1(mm) 
                 H 2 (mm) 
               
               
                   
               
            
           
           
               
               
               
               
               
               
               
               
               
            
               
                 Passive 
                 2.0 
                 34.0 
                 10.0 
                 1.0 
                 2.0 
                 28.0 
                 0.8 
                 0.3 
               
               
                 Nonlinear (FIG. 2a) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Passive 
                 2.0 
                 19.2 
                 2.8 
                 1.0 
                 2.0 
                 19.2 
                 2.8 
                 0.3 
               
               
                 Linear (FIG. 3) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Hybrid 
                 2.0 
                 22.0 
                 5.0 
                 0.5 
                 2.0 
                 22.0 
                 0.3 
                 0.3 
               
               
                 Nonlinear (FIG. 4) 
                   
                   
                   
                   
                   
                   
                   
                   
               
               
                 Hybrid 
                 2.0 
                 18.0 
                 1.6 
                 0.3 
                 2.0 
                 18.0 
                 1.6 
                 0.3 
               
               
                 Linear (FIG. 5) 
               
               
                   
               
            
           
         
       
     
     Turning now to  FIGS. 6-10 , a valve actuation scheme  70  for controlling the flow of active fluid in the active fluid line  26  is disclosed. The valve actuation scheme can be used in the valve  24  above, for example. More generally, the valve actuation scheme  70  includes an implant  71  and an actuator  85 . The implant  71  is implanted in the body along the active fluid line  26  while the actuator  85  remains outside of the body. 
     The implant  71  includes a housing module  72  and an activated/driven assembly  73  inside the housing module  72 . The activated/driven assembly  73  is externally driven by the actuator  85  which is supported internally by a passive mechanical support (e.g. spring  81  ) and/or by a passive thermally responsive support (e.g. balloon  82  ). The balloons  82  are pressurized with a fluid that is thermally responsive (that is, the pressure in the balloon  82  changes with thermal changes, which in turn changes the amount of force exerted by the balloons  82  on the driven assembly  73 . In this example, the actuation of the driven assembly  73  is by translational motion of the driven assembly  73 . The housing module  72  includes a container  74 , a cover  75 , and a reservoir/accumulator  76  in fluid communication with one or more fluid outlets  78 , which in turn are in fluid communication with the active fluid line  26 . The driven assembly  73  includes a soft magnetic alloy disc  79  (such as one of the soft magnetic alloy discs discussed above) with one or more keys  77 , a passive magnet  83 , and a separator  74  between the soft magnetic alloy disc  79  and the passive magnet  83 . 
     The keys  77  are received in a keyway  80  in the container  74 . The keys  77 /keyway  80  maintain the alignment of the soft magnetic alloy disc  79  in the housing module  72  while allowing it to move axially (e.g., translational motion) within the housing module  72 . In general, rotational motion can be provided by an external drive (e.g. motor) to the actuator  85  magnets, which causes passive magnets  83  in the implant  71  to rotate due to magnetic coupling. The passive magnet  83  is connected to the soft magnetic alloy disc  79 . As the passive magnets  83  and soft magnetic alloy disc  79  move, fluid is forced into and out of the AV graft  20  valve  20   a  as discussed below. 
     In one example, a feature such as a spring  81  and/or a balloon  82  is arranged adjacent the keys  77  in the keyway  80  to maintain a position of the soft alloy disc  79  in a resting state, as shown in  FIGS. 6 and 8 . In other words, the spring  81  and/or the balloons  82  provide passive support for the soft magnetic alloy disc  79 . In another example, a spring  81  is between the soft magnetic alloy disc  79  and the container  74 , as shown in  FIG. 7 . The springs  81  are non-magnetic and have high corrosion resistivity and a high frequency life cycle. In the resting state the soft magnetic alloy disk  79  is locked with the passive magnet  83 , compressing the reservoir/accumulator  76  and draining the active fluid into the balloon valve  20   a , which blocks the blood from flowing between artery  21  and vein  22  as discussed above When activated by magnetic activation, as discussed in more detail below, the actuator  85  moves the soft magnetic alloy disk  79  away from the passive magnet  83 , decompressing the reservoir/accumulator  76 , which drains the balloon valve  20   a  active fluid into the reservoir/accumulator  76  and allows blood to flow between artery  21  and vein  22 . 
     Similar to the hybrid magnetic activation schemes discussed above, in one example, the actuator  85  includes a driving assembly  86   a , which in turn includes a non-magnetic base  90 , a body  91 , and an active magnet  86   b . The active magnet  86   b  includes a soft magnetic alloy core  87  wrapped with a coil  88 , and the soft magnetic alloy core  87  and coil  88  are arranged in a non-magnetic shell  89 . The number of turns of the coil  88  is selected to provide the required power to activate the magnet  83  in the implant  71 , and depends on the particular configuration and geometry of the soft magnetic alloy core  87  and the passive magnet  83 . 
     The active magnet  86   b  in the actuator  85  interacts with the passive magnets  83  in the implant  71  when a current is applied to the coil  88  via an external power source to generate a magnetic field to overcome the resistive forces provided by the springs  81  and/or balloons  82  and move the soft magnetic alloy disc  79  out of the resting state and into the active state, as discussed above. 
     Turning now to  FIGS. 11-12 , an alternate valve actuation scheme with implant  171  and actuator  185  are shown. The alternate implant  171  includes a housing module  172  and an activated/driven assembly  173  inside the housing module  172 . The housing module  172  includes a container  174 , a cover  75 , and a reservoir/accumulator  76  in fluid communication with one or more fluid outlets  78 , which in turn are in fluid communication with the active fluid line  26 . 
     The activated/driven assembly  173  is externally driven by the actuator  185 . In this example the motion of the activated/driven assembly  173  is rotational. The driven assembly  173  includes passive magnets  179 , and a soft magnetic alloy disc  183  attached to a nonmagnetic separator  184 . The housing module  172  includes a shaft  177  extending through its center and through a hole in the driven assembly  173 . The hole in the driven assembly  173  includes a keyway  178  around its surface. The shaft  177  includes a thread  176  which interacts with the keyway  178 . The outer surface of the nonmagnetic separator  184  also includes a keyway  180  that interacts with a thread  181  on the container  174 . When the nonmagnetic separator  184  is moved from the resting state as discussed above, it rotates. The keyway  178  and corresponding thread  176  and the keyway  180  corresponding to thread  181  provide a track along which the nonmagnetic separator  184  moves axially within the housing module  172  as it rotates due to magnetic activation, compressing or decompressing the reservoir/accumulator  76  as discussed above. 
     The actuator  185  includes a driving/activator assembly  186 , a housing  191  and a separator  190 . The driving assembly  186  includes the same number of passive or active magnets  187  as in the activated/driven assembly  173  and is surrounded by a nonmagnetic shell  189 . The implant  171  and actuator  185  include the appropriate components for any of the magnetic activation schemes discussed above and shown in  FIGS. 2-5 . 
     The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. Thus, the scope of legal protection given to this disclosure can only be determined by studying the following claims.