Abstract:
In one embodiment, the present invention provides a cardiac lead device including a fixation mechanism slidably attached to the lead such that when the fixation mechanism is expanded in to contact with a body lumen, the lead may be moved relative to the fixation mechanism if desired. Such lead movement may be limited by complimentary structure on the lead body and the fixation mechanism that prevents the lead from moving unless sufficient force is applied to the lead.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation-in-part of application Ser. No. 11/114,730 filed Apr. 26, 2005, entitled “Fixation Device for Coronary Venous Lead,” which is incorporated by reference herein in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to implantable medical devices and, in particular, to fixation of cardiac leads in a patient&#39;s vascular system. 
       BACKGROUND 
       [0003]    Cardiac function management systems are used to treat arrhythmias and other abnormal heart conditions. Such systems generally include cardiac leads, which are implanted at a target location suitable for delivering an electrical stimulus therapy to a patient&#39;s heart. A cardiac lead typically includes a flexible conductor defining a central channel or lumen, surrounded by an insulating tube or sheath extending from an electrode at the distal end to a connector pin at the proximal end. 
         [0004]    Cardiac lead placement may be accomplished by introducing the lead through a major blood vessel and advancing a distal end of the lead to a target location suitable for electrical stimulation of a patient&#39;s heart. The target location may be located near or in a patient&#39;s heart or at a location adjacent a nerve or nerve bundle. To facilitate cannulation of the vasculature, it is often helpful to first advance a guiding catheter through the desired vascular path. One difficulty with implanting leads in this fashion is that the cardiac lead has a tendency to become dislodged from its desired location during or after lead implantation. For example, when a clinician withdraws the guiding catheter, the lead may dislodge or otherwise reposition. Until tissue in-growth ultimately fixes the lead at the desired site, cardiac leads may also become dislodged by subsequent physiological activity. 
       SUMMARY 
       [0005]    In one embodiment, the present invention provides a cardiac lead system adapted for anchoring in a vessel. In one embodiment, the lead system is adapted for anchoring in a vessel adjacent a nerve. Stimulation of the nerve can result in regulation of cardiac function. The system includes a conductive lead body and an expandable fixation mechanism. The lead body has a proximal end and a distal end and defines a lead lumen extending between the proximal and distal ends. The expandable fixation mechanism has an expanded position adapted to engage an inner surface of the vessel, and is slidably secured to an outer surface of the lead body. The lead body and the fixation mechanism include respective first and second structures that are adapted to contact each other to resist relative longitudinal movement. 
         [0006]    The first structure on the lead body may include one or more stops, curves, bends, coils, ridges or other protrusions on the lead body. The second structure may include one or more rings connected to the fixation mechanism and encircling the lead body. In one embodiment, the system further includes a stylet, which may be inserted into the lead body to straighten any curves, bends, or ridges in the lead body, thus reducing the overall diameter of portions of the lead body. 
         [0007]    The fixation mechanism may be self-expanding or balloon-expanding. For self-expanding embodiments, the fixation mechanism may be compressed by an outer guide or by a dissolvable material which dissolves upon contacting bodily fluid. In one embodiment, the fixation mechanism is formed similarly to a conventional stent. 
         [0008]    In another embodiment, the present invention provides a cardiac lead device including a conductive lead body and an expandable fixation mechanism as reported above, means for compressing the fixation mechanism, and means for resisting the relative movement when the fixation mechanism is secured to the outer surface of the tubular wall of the lead body. The means for compressing the fixation mechanism may include one or more guides through which the lead body and/or fixation mechanism are slidably movable. The means for compressing may also include a dissolvable material as reported above. The means for resisting relative movement may include the first and/or second structure reported above. 
         [0009]    The present invention also provides a method for implanting a cardiac lead device in a body lumen. A cardiac lead device as reported herein is guided into the body lumen. A fixation mechanism, which is slidably secured to the lead body, is then deployed from a compressed position to an expanded position to engage the internal wall of the body lumen. The lead can be moved relative to the expanded fixation mechanism in order to reposition the lead. In one embodiment, the lead can be moved along a longitudinal axis of the vessel in which it is deployed. In another embodiment, the lead can be rotated relative to the expanded fixation device. Prior to guiding the lead device, one or more guides may be inserted into the body lumen to facilitate the lead implantation process. 
         [0010]    According to some embodiments, the present invention provides a method of implanting a cardiac device in a body lumen adjacent a vagus nerve. In some embodiments, the body lumen is the internal jugular vein. The method includes advancing the cardiac lead device to a target location in a body lumen adjacent the vagus nerve and deploying an expandable fixation mechanism such that the fixation mechanism engages an internal wall of the lumen. The lead can be moved relative to the expanded fixation mechanism in order to reposition the lead. In one embodiment, the lead can be moved along a longitudinal axis of the vessel in which it is deployed. In another embodiment, the lead can be rotated relative to the expanded fixation device. 
         [0011]    While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. As will be realized, the invention is capable of modifications in various obvious aspects, all without departing from the spirit and scope of the present invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]      FIG. 1  is a schematic view of a cardiac lead implanted in a cardiac vessel according to an embodiment of the present invention. 
           [0013]      FIG. 2  is a schematic view of a cardiac lead implanted in a patient&#39;s internal jugular vein at a location adjacent the vagus nerve according to another embodiment of the present invention. 
           [0014]      FIG. 3  shows a schematic view of a distal portion of a cardiac lead according to an embodiment of the present invention implanted in a patient&#39;s vasculature. 
           [0015]      FIG. 4  illustrates the embodiment of  FIG. 3  after insertion of a stylet into a lumen of the cardiac lead. 
           [0016]      FIG. 5  shows a distal portion of a cardiac lead implanted in a patient&#39;s vasculature according to another embodiment of the present invention. 
           [0017]      FIG. 6  illustrates the embodiment of  FIG. 5  after insertion of a stylet into a lumen of the cardiac lead. 
           [0018]      FIGS. 7A-7D  show end plan views of multiple embodiments of the present invention. 
           [0019]      FIG. 8  is a flowchart illustrating a method for implanting a cardiac lead according to one embodiment of the present invention. 
           [0020]      FIG. 9  shows a cardiac lead being implanted according to the method described in  FIG. 8 . 
           [0021]      FIG. 10  is a flowchart describing an alternate method for implanting a cardiac lead according to one embodiment of the present invention. 
           [0022]      FIG. 11  illustrates a cardiac lead implanted according to the method illustrated in  FIG. 10 . 
       
    
    
       [0023]    While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION 
       [0024]    While some of the embodiments described herein generally refer to placement of a lead into a cardiac vessel such as, for example, the great cardiac vein, the various embodiments of the present invention as described below can be practiced at numerous sites within a patient&#39;s vasculature system. Any intravascular site that is located in or near a patient&#39;s heart or, alternatively, located adjacent to a nerve or muscle that when stimulated with an electrical pulse regulates cardiac function is a potential site for stimulation. In addition to the locations in and near a patient&#39;s heart, exemplary stimulation sites include, but are not limited to, the following: the left and right internal jugular veins, the azygous vein, the brachiocephalic (innominate) vein, the subclavian vein, the superior vena cava, and the pulmonary artery. Exemplary nerves to be stimulated in order to affect cardiac function include, but are not limited to, the following: the left and right vagus nerves, the phrenic nerve, the parasympathetic nerves, the sympathetic nerves, and the sacral nerve. 
         [0025]      FIG. 1  is a schematic drawing of a cardiac rhythm management device  12  coupled to an intravascular endocardial lead  14  having a proximal end  16  and a distal end  18 . Distal portions of the lead  14  are disposed in the vessel located within the patient&#39;s heart  20 , which includes a right atrium  22 , a right ventricle  24 , a left atrium  26 , and a left ventricle  28 . In the embodiment illustrated in  FIG. 1 , the distal end  18  of lead  14  is transvenously guided into the right atrium  22 , through a coronary sinus  30 , and into a cardiac vein  31  using techniques known to those of skill in the art. The illustrated disposition of the lead  14  may be used for delivering pacing and/or defibrillation energy through any cardiac vessel, including the cardiac sinus  30 , coronary veins or pulmonary artery, to the left ventricle  28  for the treatment of cardiac arrhythmias. 
         [0026]    The lead  14 , according to the various embodiments discussed below, can also be implanted at other locations within a patient&#39;s vasculature. In certain embodiments, distal portions of the lead  14  can be delivered and implanted at a target location within a vessel adjacent a nerve or nerve bundle. The lead  14  is capable of delivering an electrical stimulus pulse across the vessel walls to the adjacent nerve. Stimulation of the nerve or nerve bundle can result in regulation of cardiac function. 
         [0027]      FIG. 2  shows a perspective view showing a lead  14  deployed at another location within a patient&#39;s vasculature system  50 . As shown in  FIG. 2 , the lead  14  is inserted into a patient&#39;s vasculature system  50  and advanced through the left subclavian vein  52  and into the right internal jugular vein  54  at a location adjacent the vagus nerve  58 . Stimulation of the vagus nerve  58  can result in regulation of cardiac function. In another embodiment, the lead  14  can also be inserted and advanced into an internal jugular vein using a same side approach. For example, the lead  14  may be inserted into the patient&#39;s vasculature system  50  through the right subclavian vein  60  and into the right internal jugular vein  54 . In yet other embodiments, the lead  14  can be delivered to a target location within a patient&#39;s left internal jugular vein  62  to stimulate the right vagus nerve  64 . In still other embodiments, the lead  14  can be delivered to a location within a patient&#39;s brachiocephalic vein or subclavian vein that is adjacent to the vagus nerve. 
         [0028]      FIGS. 3-6  show cross-sectional views of a vessel  31  into which the cardiac lead  14  has been implanted. The cardiac lead  14  generally includes a lead body  133  and an expandable fixation mechanism  134 , which is secured to the lead body  133 . The lead body  133  has a proximal end  16  (see  FIG. 1 ) and a distal end  18  and at least one lead lumen  138  extending between the proximal and distal ends  16 ,  18 . The lead body  133  further includes at least one electrode  137  located on the lead body  133  for delivering an electrical pulse. The at least one electrode  137  can be located either proximal or distal to the expandable fixation mechanism  134 . In one embodiment, the electrode  137  is located at the distal end  18  of the lead  14  ( FIGS. 3-5 ). In another embodiment, as shown in  FIG. 6 , the at least one electrode  137  is located on the lead body  133  at a location proximal to the expandable fixation mechanism  134 . In certain embodiments, the electrode  137  may be affixed to the wall of vessel  31 . 
         [0029]    As shown in  FIGS. 3-6 , the fixation mechanism  134  is configured to contact the vessel  31  when in an expanded position. In certain embodiments, the fixation mechanism  134  is configured in a stent-like form as shown in  FIGS. 3-6 . Other shapes and configurations may also be suitable for embodiments of the present invention. The fixation mechanism  134  may be formed from conventional stent materials, for example, stainless steel, nitinol, or shape memory alloys or polymers. In a particular embodiment, the fixation mechanism  134  is (or is a modified version of) a Palmaz-Shatz type stent commonly used in vascular intervention procedures. In another embodiment, the fixation mechanism  134  is partially or completely formed from a biodegradable and or dissolvable material that degrades when contacted with body fluid. 
         [0030]    The fixation mechanism  134  is slidably secured to the lead body  133  such that the lead body  133  is selectively movable relative to the fixation mechanism  134  along the longitudinal path of the vessel  131  when the fixation mechanism  134  is in the expanded position shown. The lead  14  can be moved relative to the fixation mechanism  134  in either a proximal or a distal direction. In some embodiments, the position of the lead  14  can be adjusted such that one or more electrodes  137  located on the lead body  133  are located either proximal or distal to the fixation mechanism  134 . Such selective relative movement is accomplished by providing both the lead body  133  and the fixation mechanism  134  with cooperating or corresponding structures as described in detail below. 
         [0031]    The structure on the lead body  133  may be configured to increase a major dimension (e.g. diameter) of the lead body  133  at select locations. Numerous configurations may be employed for the structure on the lead body  133 . In the embodiment illustrated in  FIG. 3 , for example, the lead body  133  includes one or more coiled or looped portions  144 , which cooperate with the structure on the fixation mechanism  134  to limit undesired or unintentional longitudinal movement of the lead body  133 . In an alternate embodiment, the structure includes a two-dimensional shape such as a sinusoidal shape or a J-bend. 
         [0032]    The embodiment illustrated in  FIG. 5  includes protrusions  146  secured along a plurality of ridges  148  formed in the lead body  133 . The protrusions  146  may be formed as bumps, spheres, ears, rings, or other shapes formed on and extending from the surface of the lead body  133 . The protrusions  146  may be formed from silicone or other biocompatible materials and may remain substantially permanently secured to the lead body  133  or may be biodegradable. 
         [0033]    The looped portions  144 , protrusions  146 , or ridges  148  may be positioned anywhere along the length of the lead body  133 . In the illustrated embodiments, structure is located both proximal and distal to the fixation mechanism  134  to allow for a range of proximal and distal movement of lead body  133 . Other configurations may also be appropriate depending on the specific application of the cardiac lead  14 . Furthermore, although  FIGS. 3 and 5  show specific structures for limiting movement of the lead body  133 , it should be appreciated that a wide range of structures, either individually or in combination, may be used in embodiments of the present invention. The loops  144 , protrusions  146 , or ridges  148  may be spaced at various adjustment intervals depending on the magnitude of adjustments desired. In one embodiment, for example, these structures are located between about 1 and about 10 millimeters apart, or more preferably between about 2 and about 5 millimeters apart, along the lead body  133 . 
         [0034]      FIGS. 7A-7D  show plan views of the cardiac lead  14  from the perspective of the line  9 - 9  shown in  FIG. 3 . As shown in  FIGS. 7A-7D , the fixation mechanism  134  includes one or more fixation rings  140  which contact or otherwise interact with structure on the lead body  133  to provide selective movement of the lead body  133 . The fixation rings  140  generally encircle the lead body  133 , and are generally connected to the outside (i.e. vessel engaging) surface of the fixation mechanism  134  via struts  142 . As further shown in  FIGS. 7A-7D , the struts  142  may have a variety of configurations. The fixation rings  140  may be formed anywhere along the length of the fixation mechanism  134 , but in one embodiment, the fixation rings  140  are disposed on opposing ends of the fixation mechanism  134 . 
         [0035]    The fixation rings  140  and struts  142  may be formed from a variety of materials, including materials commonly used to form stents. In certain embodiments either or both of the rings  140  and the struts  142  may be formed from an elastic, string, fibrous, or thread-like material. Additionally the fixation rings  140  and the struts  142  may be formed to be biodegradable and/or dissolvable upon contact with bodily fluid, or to remain substantially and permanently in the vessel  31 . In one embodiment, the fixation rings  140  and the struts  142  may be formed to biodegrade after a period of time sufficient to allow the lead body to become secured within the vessel  31  by tissue in-growth. For example, the fixation mechanism  134  could be temporarily fixed to the lead body with a resorbable material that would dissolve over a period of weeks or months to allow extraction of the lead at a later date. 
         [0036]    As shown in  FIGS. 3 and 5 , the structures disposed on both the lead body  133  and the fixation mechanism  134  resist longitudinal movement of the lead body  133  relative to the fixation mechanism  134  because the structure on the lead body  133  (i.e. coiled portions  144 , protrusions  146  and/or ridges  148 ) has a major dimension that is greater than the diameter of the fixation rings  140  such that longitudinal movement of the lead body  133  is limited or selectively prevented. In certain embodiments, the structures on the lead body  133  can also prevent rotational movement of the lead body  133  relative to the fixation mechanism  134 . 
         [0037]    To reposition the lead body  133  according to one embodiment, the major dimension of the lead body  133  in the vicinity of the fixation mechanism  134  may be reduced to a size that is smaller than the diameter of the fixation rings  140 , by inserting a stylet or guidewire into the lead lumen  138 . For example,  FIG. 4  shows the embodiment of  FIG. 3  after inserting a stylet or guidewire  150  such that the coiled portions  144  are straightened.  FIG. 6  shows the embodiment of  FIG. 5  after inserting a stylet or guidewire  150  such that the ridges  148  are straightened. In both cases, the lead body  133  becomes movable relative to the fixation mechanism  134  along the longitudinal path of the vessel  31 . In certain embodiments, the lead  14  also becomes rotatable relative to the fixation mechanism  134 . Rotation of the lead  14  allows the at least one electrode  137  to be oriented towards the target stimulation site. After repositioning the lead body  132 , the stylet or guidewire  150  may be removed such that the structure returns to the shape shown in  FIGS. 3 and 5 , which again limits longitudinal and/or rotational movement of the lead  133  with respect to the fixation mechanism  134 . According to another embodiment, instead of changing the major diameter of the lead, the interacting structures on the lead body  133  and the fixation rings  140  have sufficient flexibility to allow the structures to pass through the rings upon application of a sufficient force at the proximal end  16  of the lead body  133 . 
         [0038]      FIGS. 9-10  depict a method of implanting the cardiac lead  14  according to an embodiment of the present invention.  FIG. 8  is a flow-chart showing a method of implanting the cardiac lead  14  according to one embodiment of the present invention. The cardiac lead  14  is pre-loaded into an inner guide catheter  158  such that the fixation mechanism  134  is in a compressed position (block  202 ). The inner guide catheter  158  is then directed through the patient&#39;s vasculature, optionally through an outside guide catheter or sheath  160 , to a desired location in the patient&#39;s vasculature (block  204 ) as shown in  FIG. 8 . The inner guide catheter  158  is then withdrawn such that the fixation mechanism  134  deploys to an expanded position (block  206 ) shown in  FIGS. 3-6 . The fixation mechanism  134 , in this embodiment, may expand by, for example, self-expansion or balloon expansion. In one embodiment, after the fixation mechanism  134  is expanded and secured to the wall of the vessel  31 , the longitudinal position of the lead body  133  may be adjusted. In yet another embodiment, the lead body  133  can be rotated relative to the fixation mechanism  134 . The stylet or guidewire  150  is then removed, which allows the lead  133  to resume its default shape (see, for example,  FIGS. 3 and 5 ) having an increased major diameter, which, in turn, limits or resists further longitudinal movement of the lead body  133 . 
         [0039]    In a variation of the method described in  FIGS. 8-9 , the fixation mechanism  134  may be fixed to the lead body  133  in a compressed state with a dissolvable material such as manitol. The lead  14  is inserted through an inner guide catheter  158  until positioned as desired. The lead  14  could then be advanced out of the inner guide catheter  158  to the desired position, which would also expose the dissolvable material to blood. After a short period of time the dissolvable material would dissolve, allowing the fixation mechanism  134  to expand and contact the vessel wall. 
         [0040]      FIGS. 10-11  depict a method of implanting the cardiac lead  14  according to another embodiment of the present invention.  FIG. 11  is a flow-chart summarizing a method of implanting the cardiac lead  14  according to an embodiment of the present invention, in which the fixation mechanism  134  is initially positioned on an outer surface of the inner guide catheter  158  (block  262 ) with an optional inflation balloon  159  disposed between the fixation mechanism  134  and the inner guide catheter  158 . The inner guide catheter  158  is then directed through an outside guide catheter  160  and into a desired location in a patient&#39;s vasculature (block  264 ). The lead body  133  is then directed through the inner guide catheter  158  (block  266 ) until the distal end  18  of the lead body  133  extends past the distal end of the inner guide catheter  158  and into a desired location (block  266 ) as shown in  FIG. 10 . The fixation mechanism  134  is then expanded via self-expansion or by inflating the optional balloon  159  in a conventional manner (block  270 ). The inner guide catheter  158  is then withdrawn such that the fixation rings  140  encircle the lead body  133  as shown in  FIGS. 3-6  (block  272 ). After the fixation mechanism  134  is expanded and secured to the wall of the vessel  31 , the longitudinal position of the lead body  133  may be adjusted. In a further embodiment, the lead body  133  can also be rotated relative to the fixation mechanism. The stylet or guidewire  150  is then removed, which allows the lead body  133  to resume its default shape (see, for example,  FIGS. 3 and 4 ) having an increased major diameter, which, in turn, limits or resists further longitudinal and/or rotational movement of the lead body  133 . 
         [0041]    In a variation to the method shown in  FIGS. 10-11  and described above, the fixation mechanism  134  is disposed on the inner guide catheter  158  and is pre-loaded into the outside guide catheter  160 . After positioning the inner and outer guide catheters  158 ,  160  and the lead body  133  as described above, a tube or other structure (not shown) may be directed between the inner and outer guide catheters  158 ,  160  to deploy the fixation mechanism  134  into an expanded position shown in  FIGS. 3-6 . 
         [0042]    Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.