Abstract:
Medical leads have one or more openly coiled filars and a distal body coupled to the openly coiled filars. The openly coiled filars provide a lead with compliance and elasticity while the distal body provides the firmness needed for placement and support of the electrodes. The openly coiled filars may transition to a linear distal portion that extends to the distal body, and the distal body may have proximal tines that fold proximally to become adjacent to the linear distal portion of the filars. The openly coiled filars may instead extend to the distal body and the proximal tines may be laterally arced to then fold against the lateral surface of the coiled filars. The tines may fold distally during explantation to allow the distal body to release and exit the body.

Description:
TECHNICAL FIELD 
       [0001]    Embodiments are related to medical leads that carry stimulation signals. More particularly, embodiments are related to medical leads that have a distal body and openly coiled filars. 
       BACKGROUND 
       [0002]    Medical leads are used in conjunction with a medical device that generates stimulation signals to deliver the stimulation signals from the medical device to a target stimulation site within a body of a patient. The medical leads may be implanted through a percutaneous procedure where an introducer needle is inserted into the body, and a medical lead is inserted through a lumen in the needle. A stylet may be included within a lumen of the medical lead to guide the medical lead from the needle to the target site. 
         [0003]    One issue when implanting the medical lead is that the needle must be of adequate size to facilitate the introduction of the medical lead. However, a smaller needle is less bothersome to the patient. Thus, minimizing the diameter of the lead is desirable so that the size of the introducer needle may also be minimized. 
         [0004]    Another issue that occurs once the medical lead is implanted is that the medical lead needs to have a fixed position at the target site, which is particularly true when assessing the efficacy of therapy during a trial period. Movements by the patient may encourage the medical lead to migrate and therefore a fixation structure may be required to provide the fixation of the lead at the target site. However, the structure for fixation may contribute to the size of the medical lead which may call for an undesirable increase in the size of the introducer needle. Furthermore, explantation of the lead may be more difficult due to the presence of the fixation structure which resists movement in the direction of explantation. 
         [0005]    The effectiveness of a fixation structure may also be limited by the compliance of the body of the lead. The body of the lead needs a degree of firmness to support the electrodes and to maintain their alignment when at the target site. Yet a stiff lead body extending toward the proximal end of the lead is counterproductive to the fixation structure. 
       SUMMARY 
       [0006]    Embodiments address issues such as these and others by providing a body that utilizes one or more openly coiled filars that act as a portion of the lead body and provides a relatively high degree of compliance. A distal body is present at the distal end of the coiled filar where the distal body provides a firmer support for the electrodes. The distal body may include tines on the proximal end that offer fixation. The coiled filar may have a linear region proximal of the distal body, and the tines may collapse in the proximal direction to avoid increasing the diameter of the lead. Furthermore, the tines may collapse in the opposite direction when subject to a removal force during explantation. 
         [0007]    Embodiments provide a medical lead that includes a filar with an openly coiled center portion. The medical lead further includes a distal body having an electrode, with a distal portion of the filar passing through the distal body and being coupled to the electrode. 
         [0008]    Embodiments further provide a medical lead that includes an openly coiled filar that has a linear distal end. The medical lead includes a distal body having an electrode and also having at least one tine on a proximal end, with a distal portion of the linear distal end of the coiled filar passing through the distal body and being coupled to the electrode. A junction of the at least one tine to the distal body provides a hinge point, the at least one tine being rotatable about the hinge point between a collapsed state and an extended state. The at least one tine rotates in the proximal direction from the extended state to the collapsed state to become adjacent to the linear distal end of the coiled filar. 
         [0009]    Embodiments provide a medical system that includes a stimulation device and a medical lead with a proximal end coupled to the stimulation device. The medical lead includes an openly coiled filar that has a proximal end coupled to the stimulation device and has a linear distal end. The medical lead further includes a distal body having an electrode and also having at least one tine on a proximal end, with a distal portion of the linear distal end of the coiled filar passing through the distal body and being coupled to the electrode. A junction of the at least one tine to the distal body provides a hinge point, the at least one tine being rotatable about the hinge point between a collapsed state and an extended state, The at least one tine rotates in the proximal direction from the extended state to the collapsed state to become adjacent to the linear distal end of the coiled filar. 
         [0010]    Embodiments provide a method of positioning a medical lead that involves providing the medical lead having an openly coiled filar that has a linear distal end. The medical lead also has a distal body having an electrode and also having at least one tine on a proximal end, with a distal portion of the linear distal end of the coiled filar passing through the distal body and being coupled to the electrode. A junction of the at least one tine to the distal body provides a hinge point, the at least one tine being rotatable about the hinge point between a collapsed state and an extended state. The at least one tine rotates in the proximal direction from the extended state to the collapsed state to become adjacent to the linear distal end of the coiled filar. The method further involves implanting the medical lead by routing the medical lead through a needle with the at least one tine in the collapsed state and with the at least one tine achieving the extended state upon exiting the needle. The method also involves explanting the medical lead by removing the lead in the proximal direction, wherein during explanting the at least one tine rotates distally from the extended state to a second collapsed state where the at least one tine is adjacent to the distal body. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows an example of a medical lead according to various embodiments. 
           [0012]      FIG. 2  shows a longitudinal cross-section of the medical lead of  FIG. 1 . 
           [0013]      FIG. 3  shows a first stage of one example of an implantation procedure of the medical lead of  FIG. 1 . 
           [0014]      FIG. 4  shows a second stage of the implantation procedure. 
           [0015]      FIG. 5  shows the medical lead once implanted and connected to a stimulation device. 
           [0016]      FIG. 6  shows an example of an explantation of the medical lead. 
           [0017]      FIG. 7  shows another example of a medical lead according to various embodiments. 
           [0018]      FIG. 8  shows a longitudinal cross-section of the medical lead of  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Embodiments of medical leads include a compliant lead body formed by one or more openly coiled filars with a firmer distal body coupled to distal ends of the one or more filars. The distal body supports the electrodes, and some embodiments of the distal body may include proximal tines that collapse in the proximal direction to minimize the distal body diameter. Furthermore, in some embodiments the tines may collapse in the distal direction when the lead receives a removal force during explantation. 
         [0020]      FIGS. 1 and 2  show one example of a medical lead  100  having a central portion  114  of a filar that is openly coiled. In other words, the coiled filar is not surrounded by a protective tubular jacket but is instead itself the lead body. This openly coiled filar portion  114  provides a relatively high degree of compliance and elasticity for the lead  100 . The filar may he constructed of various biocompatible conductors such as stainless steel alloys (316L, 316LVM, MP35N, etc.) or other biocompatible metals and alloys such as alloys of platinum (Pt—Ir) or alloys of titanium (TiOsteum®, Ti—15Mo) that have a non-conductive coating such as polyethylene-co-tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE or Teflon®), polyurethanes, polyimides, etc. The coiled shape defines a lumen  116  through which a stylet may be passed when implanting the medical lead  100 . 
         [0021]    In this particular example, both a proximal filar portion  118  and a distal filar portion  112  are linear rather than coiled. These linear portions  112 ,  118  enter into respective distal and proximal bodies  102 ,  120 . It will be appreciated that in other examples, one or both of these portions may be coiled as well, as in the example discussed below in relation to  FIGS. 7 and 8 . 
         [0022]    The proximal body  120  of  FIGS. 1 and 2  provides a firmer support for one or more contacts  122 ,  124  that are ultimately connected to a stimulation device. The proximal body  120  may be inserted into a bore within a stimulation device where the electrical connections occur. The proximal body  120  may be constructed of various nonconductive biocompatible materials such as polyurethane, polyether block amide (PEBA or PEBAX®), polyether ether ketone or polyaryletherketone (PEEK) and others. The proximal body  120  may define a lumen  128  that allows a stylet to be inserted during implantation of the medical lead  100 . 
         [0023]    The proximal portion  118  of the filar(s) may extend through the proximal body  120  until reaching the respective contacts  122 ,  124 , The proximal portion  118  of the filar(s) is then physically and electrically coupled to the respective contacts  122 ,  124 . 
         [0024]    The distal body  102  provides a firmer support for one or more electrodes  104 ,  106  that are ultimately positioned at the target stimulation site within the body of the patient. The distal body  102  may be constructed of various nonconductive biocompatible materials such as polyurethane, silicone, and surface-modified endgroup (SME) polyurethanes to provide such firmness. The distal body  102  may define a lumen  126  that allows a stylet to be inserted when implanting the medical lead  100 . 
         [0025]    The distal portion  112  of the filar(s) may extend through the distal body  102  until then coupling to the respective electrode  104 ,  106 . The filar may be present within the lumen  126  or may otherwise tunnel through the distal body  102  until reaching the electrode  104 ,  106 . Furthermore, the distal-most region of the distal filar portion  112  which is present within the lumen  126  may be coiled rather than linear, which provides an additional mechanical advantage during explantation to minimize strain on the bond of the filar portions  112  to the electrodes  104 ,  106 . Another manner of minimizing such strain during explantation involves using a polyurethane coating directly on the metal of the filar portions  112  and then allowing the polyurethane coating to achieve a bond with the polymer forming the distal body  102 . 
         [0026]    To provide fixation for the electrodes  104 ,  106 , the distal body  102  may further define one or more proximal tines  108 ,  110 . As shown in  FIGS. 1 and 2 , two tines  108 ,  110  are present on opposite sides of the proximal end of the distal body  102  but any number of tines may be present in various embodiments. These tines have a natural extended state as shown in  FIGS. 1 and 2  whereby the tines  108 ,  110  extend from the distal body  102  at a particular angle. In this extended state, the tines  108 ,  110  effectively catch upon the surrounding tissue of the body to resist movement in the proximal and distal directions. The amount of fixation force created by the tines  108 ,  110  can be controlled by the physical dimensions chosen for the tines  108 ,  110  including the angle, the length, the width, the thickness, and the geometry. Thus, the medical lead  100  may be selected for a particular implantation scenario based on having a tine design that meets the fixation requirements of the scenario. 
         [0027]    The distal body  102  and tines  108 ,  110  may be constructed by being molded onto the linear distal end  112  of the filars. An alternative construction would be to use tine and tubing components assembled manually and bonding them together with adhesives or thermally reflowing the polymers together. 
         [0028]    During implantation, the tines  108 ,  110  can be forced into a collapsed state where the tines  108 ,  110  are rotated proximally about a hinge point that occurs at the junction of the tines  108 ,  110  to the distal body  102  by insertion in the distal direction into a lumen of an introducer needle. Once fully rotated, the tines  108 ,  110  become adjacent to the linear distal portion  112  of the filar(s) so that the overall diameter of the medical lead is no greater than the diameter of the distal body  102 . Therefore, the presence of the tines  108 ,  110  does not require an increase in size of the lumen of the introducer needle. 
         [0029]    During explantation, the tines  108 ,  110  can be forced into a collapsed state where the tines  108 ,  110  are rotated distally to become adjacent to the distal body  102 . The extraction force applied to the medical lead  102  is greater than the migration forces that the medical lead  102  is subject to such that the extraction force overcomes the natural reluctance of the tines  108 ,  110  to rotate distally from the extended state to this collapsed state. 
         [0030]    One example of the process of implantation is shown in  FIGS. 3 and 4 . In  FIG. 3 , the medical lead of  FIG. 1  is located within a lumen of the introducer needle  136 , and the titres  108 ,  110  are in the proximally collapsed state. The introducer needle  136  is inserted through the body  130  of the patient and directed toward a target stimulation site. In this particular example, the target stimulation site is in close proximity to the sacrum in order to stimulate nearby the sacral nerve. For instance, the electrodes  104 ,  106  may be positioned within a foramen  134  of the sacrum such that the needle  136  is directed to the foramen  134 . 
         [0031]    In this particular example, one the needle  136  has aligned with the foramen  134 , the medical lead  100  is advanced distally from the needle  136  and through the foramen  134  by manipulation of a stylet  138  that is present within the lumens  116 ,  126 , and  128  of the medical lead  100 . The stylet  138  is used to steer the distal body  102  to the desired location relative to the sacral nerve. 
         [0032]    As shown in  FIG. 4 , upon the distal body  102  exiting the needle  136 , the tines  108 ,  110  naturally begin to rotate distally to the extended state. However, forward motion of the lead  100  by an insertion force from the stylet  138  overcomes any retention force being created by the tines  108 ,  110 . Upon reaching the target site, the needle  136  and style  138  are then removed. 
         [0033]      FIG. 5  shows the medical lead  100  with the distal body  102  in the target site with the electrodes  104 ,  106  being in proximity to the sacral nerve. The tines  108 ,  110  are in their fully extended state and provide maximum resistance to further movements of the distal body  102 . The openly coiled filar portion  114  extends proximally back to a location where a stimulation device  140  is being positioned with the proximal body  120  being coupled to the stimulation device  140 . In this example, the stimulation device  140  is a trial stimulation device being positioned externally on the body  130  such that the filar portion  114  extends beyond the outer surface of the body  130 . However, it will be appreciated that in other examples the stimulation device  140  may be implanted within a pocket formed within the body  130 . 
         [0034]    It may be desirable to subsequently explant the medical lead  100 . This is particularly the case where the medical lead  100  has been implanted for a stimulation trial. This explantation of the medical lead  100  is shown in  FIG. 6 . In this case, a removal force is applied in the proximal direction to the proximal body  120  and the proximal end of the filar portion  114 . This proximal force causes proximal movement of the distal body  102  which causes the tines  108 ,  110  to rotate distally until achieving the distally collapsed state as shown. The distal body  102  then proceeds proximally until exiting the body  130 . 
         [0035]      FIGS. 7 and 8  show another example of a medical lead  200  having a central portion  214  of a filar that is openly coiled. Like the prior example, this openly coiled filar portion  214  provides a relatively high degree of compliance for the lead  200 . The filar may be constructed of the same various biocompatible conductors with a non-conductive coating as the previous example. The coiled shape defines a lumen through which the stylet may be passed when implanting the medical lead  200 . In this particular example, the filar portion  214  extends from a proximal body  220  to a distal body  202 . 
         [0036]    The proximal body  220  provides a firmer support for one or more contacts  222 ,  224  that are ultimately connected to the stimulation device. The proximal body  220  may be inserted into a bore within the stimulation device where the electrical connections occur. The proximal body  220  may be constructed of the same various nonconductive biocompatible materials as the previous example. The proximal body  220  may define a lumen  228  that allows the stylet to be inserted during implantation of the medical lead  200 . 
         [0037]    The filar(s) may extend through the proximal body  220  until reaching the respective contacts  222 ,  224 . The filar(s) then physically and electrically coupled to the respective contacts  222 ,  224 . 
         [0038]    The distal body  202  provides a firmer support for one or more electrodes  204 ,  206  that are ultimately positioned at the target stimulation site within the body of the patient. The distal body  202  may be constructed of the same various nonconductive biocompatible materials such as the previous example to provide such firmness. The distal body  202  may define a lumen  226  that allows a stylet to be inserted when implanting the medical lead  200 . 
         [0039]    The filar(s) may extend through the distal body  202  until then coupling to the respective electrode  204 ,  206 . The filar may be present within the lumen  226  or may otherwise tunnel through the distal body  202  until reaching the electrode  204 ,  206 . Furthermore, the distal-most region of the filars which is present within the lumen  226  may be coiled rather than linear, which provides an additional mechanical advantage during explantation to minimize strain on the bond of the filars to the electrodes  204 ,  206 . Another manner of minimizing such strain during explantation involves using a polyurethane coating directly on the metal of the filars and then allowing the polyurethane coating to achieve a bond with the polymer forming the distal body  202 . 
         [0040]    To provide fixation for the electrodes  204 ,  206 , the distal body  202  may further define one or more proximal tines  208 ,  210 . As shown in  FIGS. 7 and 8 , two tines  208 ,  210  are present on opposite sides of the proximal end of the distal body  202  but any number of tines may be present in various embodiments. These tines  208 ,  210  have a natural extended state as shown in  FIGS. 7 and 8  whereby the tines  208 ,  210  extend from the distal body  202  at a particular angle. In this extended state, the tines  208 ,  210  effectively catch upon the surrounding tissue of the body to resist movement in the axial proximal and distal directions. 
         [0041]    The distal body  202  and tines  208 ,  210  may be constructed in the same manner as discussed above for the embodiment of  FIG. 1  For instance, the distal body  202  and tines  208 ,  210  may be molded onto the linear distal end  112  of the filars. An alternative construction would again be to use separate components (tines, tubings, etc.) assembled manually and bonding them together with adhesives or thermally re-flowing the polymers together. 
         [0042]    During implantation, the tines  208 ,  210  can be forced into a collapsed state where the tines  208 ,  210  are rotated proximally about a hinge point that occurs at the junction of the tines  208 ,  210  to the distal body  202  by insertion in the distal direction into a lumen of the introducer needle. Once fully rotated, the tines  208 ,  210  become adjacent to the central portion  214  of the filar(s). The tines  208 ,  210  define an arced shape in a lateral dimension that rests on the arced lateral surface of the central portion  214 . Thus, when the overall diameter of the medical lead  200  is no greater than the diameter of the distal body  202  and where the diameter of the central portion  214  is slightly smaller than that of the distal body  202 , the presence of the tines  208 ,  210  does not require an increase in size of the lumen of the introducer needle. 
         [0043]    During explantation, the tines  208 ,  210  can be forced into a collapsed state where the tines  208 ,  210  are rotated distally to become adjacent to the distal body  202 . The extraction force applied to the medical lead  202  is greater than the migration forces that the medical lead  200  is subject to such that the extraction force overcomes the natural reluctance of the tines  208 ,  210  to rotate distally from the extended state to this collapsed state. 
         [0044]    The implantation of the medical lead  200  proceeds in the same manner discussed above in relation to  FIGS. 3 and 4 . Likewise, the explantation of the medical lead  200  proceeds in the same manner discussed above in relation to  FIG. 6 . 
         [0045]    While embodiments have been particularly shown and described, it will be understood by those skilled in the art that various other changes in the form and details may be made therein without departing from the spirit and scope of the invention.