Abstract:
This document discusses, among other things, a lead assembly including a lead body, a first conductor extending through the lead body and coupled to a first electrode, a second conductor extending through the lead body and coupled to a second electrode, and a multi-filar coil extending through the lead body. The multi-filar coil includes electrically independent first and second filars respectively coupled to first and second sensing or pacing electrodes. In an example, the second filar of the multi-filar coil is substantially coaxial with the first filar. An example method includes extending first and second conductors and a multi-filar coil through lumens in a lead body and coupling electrodes to the conductors and coils.

Description:
TECHNICAL FIELD  
       [0001]     This patent document pertains generally to medical device lead assemblies, and more particularly, but not by way of limitation, to a multiple electrode implantable lead.  
       BACKGROUND  
       [0002]     Medical device lead assemblies typically include a lead body and at least one conductor extending through the lead body. Lead assemblies are often used in conjunction with an implantable medical device, such as a pacer and defibrillation, or neural stimulator.  
         [0003]     An example pacer lead assembly includes a pacing electrode, an insulative lead body, and a conductor that extends through the lead body and is electrically coupled to the pacing electrode. In some examples, the pacing electrode is near a distal end of the lead assembly, and a proximal end of the lead assembly includes a connector that couples the lead assembly to a medical device.  
         [0004]     Defibrillation leads includes at least one defibrillation electrode, such as a defibrillation coil. An example defibrillation lead assembly includes two defibrillation electrodes, two conductors that extend through the lead body and couple to the respective defibrillation electrodes, and a connector assembly that couples the defibrillation electrodes to a medical device, which typically includes a pulse generator. Some defibrillation lead assemblies also include pacing and/or sensing electrodes and additional conductors that couple to the pacing and sensing electrodes to the medical device.  
         [0005]     Other types of lead assemblies also include multiple conductors and multiple electrodes. Improved lead assemblies are needed.  
       SUMMARY  
       [0006]     An example lead assembly includes a lead body, a first conductor extending through the lead body and coupled to a first electrode, a second conductor extending through the lead body and coupled to a second electrode, and a multi-filar coil extending through the lead body. The multi-filar coil includes a first filar coupled to a first sensing or pacing electrode, and a second filar coupled to a second sensing or pacing electrode, the first filar electrically independent from the second filar.  
         [0007]     Another example medical device includes a pulse generator, a connector block, a lead assembly coupleable to the connector block. The lead assembly includes a lead body, a first conductor extending through the lead body and coupled to a first electrode, a second conductor extending through the lead body and coupled to a second electrode, and a multi-filar coil including a plurality of filars extending through the lead body. The multi-filar coil includes a first filar coupled to a first sensing or pacing electrode and a second filar coupled to a second sensing or pacing electrode.  
         [0008]     A example method includes extending a first conductor through a lead body including at least one lumen, extending a second conductor through the lead body, extending a multi-filar coil through the lead body, the multi-filar coil including at least a first filar and a second filar, coupling a first electrode to the first conductor, coupling a second electrode to the second conductor, coupling the first filar of the multi-filar coil to a first sensing or pacing electrode and coupling the second filar of the multi-filar coil to a second sensing or pacing electrode. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]      FIGS. 1A and 1B  are illustrations of a lead assembly and a heart.  
         [0010]      FIG. 2  is an illustration of a lead assembly including multiple electrodes.  
         [0011]      FIG. 3A  is a partially cut-away illustration of an example lead assembly including a multi-filar coil.  
         [0012]      FIG. 3B  is a cross-section of the lead assembly of  FIG. 3 .  
         [0013]      FIG. 3C  is a partially cut-away illustration of another example lead assembly including a quad-filar coil.  
         [0014]      FIG. 4  is a flow chart that illustrates an example method.  
         [0015]      FIG. 5  is a cross-sectional illustration of a distal portion of an example lead assembly. 
     
    
     DETAILED DESCRIPTION  
       [0016]     The following detailed description includes references to the accompanying drawings, which form a part of the detailed description. The drawings show, by way of illustration, specific embodiments in which the invention may be practiced. These embodiments are also referred to herein as “examples.” The drawings and following detailed description is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.  
         [0017]     A medical device lead assembly includes a multi-filar coil that includes at least two electrically independent filars. In an example, the multi-filar coil includes two filars, at least one of which includes a coating of insulation. The filars extend along a helical path and form the multi-filar coil. The helical path optionally has a constant radius, and/or a constant pitch. The filars of the multi-filar coil are optionally coradial. In an example, each filar of the coil is insulated. In an example, the multi-filar coil extends through a lumen in a multi-lumen lead body. Cables or other conductors extend through other lumens in the lead body. The use of a multi-filar coil facilitates fabrication of small-diameter leads and/or multi-conductor leads, including leads that have four or more conductors, for example. Reducing the size of leads can be desirable, for example to avoid interference with heart valve functions.  
         [0018]     A multi-filar coil allows for efficient use of space in a lead body. For example, a multi-filar coil typically takes up about the same amount of cross-sectional space as a single-filar coil of the same size, while providing two or more electrical connections instead of one. In contrast, in a lead assembly that does not include a multi-filar coil, an increase in the number of conductors is usually accompanied by an increase in the overall size (e.g. diameter) of the lead assembly, a reduction in the diameter of one or more conductors, or a reduction in tubing wall thickness. Reducing the conductor diameter can be problematic, for example, because some small-diameter conductors can be difficult to string through a lumen in a lead body. Reducing wall thickness of tubing can affect abrasion performance.  
         [0019]     A multi-filar coil can also be used to achieve desirable handling characteristics. Lead assemblies with particularly low bending stiffness can be difficult to handle. For example, it is difficult to push a highly flexible lead through a blood vessel, because the lead bends when it is urged through the vessel. Increasing the bending stiffness of a lead assembly can improve the handling or “pushability” of a lead. A coiled filar tends to be stiffer than a straight filar of the same wire diameter. In an example, a multi-filar coil provides increased stiffness and desirable handling or pushability characteristics. In an example, the size and number of filars in a coil are adjusted to adjust the handling characteristics. In another example, a multi-filar coil that is coupled to pacing or sensing conductors is combined with high-voltage conductors such as defibrillation cables to provide a tachycardia lead with desirable size and bending characteristics.  
         [0020]      FIGS. 1A and 1B  show examples of lead assemblies extending from a pulse generator into a heart. The lead assembly includes a lead body and a multi-filar coil including two or more electrically isolated filars.  FIG. 2  shows another example lead assembly having multiple electrodes and a multi-filar coil.  FIG. 3A  shows a partially cutaway view of an example lead assembly that includes a multi-filar coil and two additional conductors. A cross-section of the example lead assembly shown in  FIG. 3A  is provided in  FIG. 3B . While a multi-filar coil having two filars is shown in  FIG. 3A , it is understood that a multi-filar coil can include three, four, or more filars. An example lead assembly having a quad-filar coil is shown in  FIG. 3C .  FIG. 4  is a flow chart that illustrates an example method.  FIG. 5  shows a cross-section of a distal portion of an example lead assembly including electrodes coupled to filars of a multi-filar coil. While a multi-filar coil having two filars is shown in  FIG. 3A , it is understood that a multi-filar coil can include three, four, or more filars.  
         [0021]     Turning now to  FIGS. 1A and 1B , an example lead assembly  100  includes a proximal portion  105  that is coupled to a pulse generator  110 , and a distal portion  115  that extends in, on, or around a heart  101 . The lead assembly  100  includes a lead body  170  and a multi-filar coil  135  including two or more filars  150 ,  155  extending through a lumen in the lead body. In an example, the filars are  150 ,  155  are coupled to respective sensing or pacing electrodes  160 ,  165 . In an example, the sensing or pacing electrodes  160 ,  165  are usable for sensing an intrinsic electrical heart signal and/or pacing a heart. In an example, electrode  165  includes an active fixation helix. In an example, the lead assembly  100  also includes two or more defibrillation  125 ,  130  electrodes. In an example, the defibrillation electrodes  125 ,  130 , each include a defibrillation coil that is coupled to a high-voltage cable extending through the lead body  170 .  
         [0022]     In the example shown in  FIG. 1A , the lead assembly  100  extends through the superior vena cava (SVC) into the right atrium  106  and right ventricle  107 . In another alternative example, the lead assembly  100  extends on or around the right side  103  of the heart  101 . In other examples, the lead assembly  100  extends on or around the heart, or in, on, or around another location in the body.  
         [0023]     In the example shown in FIG. B, the lead assembly  100  extends through the coronary sinus  120  to the left side  102  of the heart  101 . In an example, the lead assembly extends through a vessel  104  on the left side of the heart. In an example, the lead assembly  100  is a multi-polar lead. In the example shown in  FIG. 1B , the lead assembly  100  includes third and fourth sensing or pacing electrodes  180 ,  185 . In an example, the multi-filar coil  135  includes third and fourth filars that are respectively coupled to the third and fourth sensing or pacing electrodes  180 ,  185 . In an example, a connector on the lead assembly includes sufficient electrical contacts to simultaneously connect all four sensing or pacing electrodes  160 ,  165 ,  180 ,  185  to the pulse generator. In another example, switching capability is provided in the lead assembly  100 , and a subset (e.g. two) of the electrodes can be simultaneously electrically connected to pulse generating or analysis circuitry in the pulse generator.  
         [0024]     Referring now to  FIG. 2 , an illustration of an example lead assembly is shown. The lead assembly  200  includes a lead body  205 , defibrillation electrodes  210 ,  215 , and pacing or sensing electrodes  220 ,  225 . The pacing or sensing electrodes  220 ,  225  may be used for pacing, sensing, or both. In an example, electrode  220  is a ring electrode, and electrode  225  includes a fixation helix. In an example, the electrodes  220 ,  225  include platinum or titanium coated with a combination of iridium oxide (IrOx), titanium/nickel (Ti/Ni), black platinum (Pt black) or tantalum oxide. The lead assembly  200  also includes a multi-filar coil  201  that includes at least two filars  250 ,  255 . The lead body  205  is shown partially cut-away in  FIG. 2  to show the filars  250 ,  255  of the multi-filar coil  201  extending through the lead body  205 . In an example, the filars  250 ,  255  are approximately coradial. In an example, the pacing or sensing electrodes  220 ,  225  are located near a distal end portion  230  of the lead assembly  200 . In an alternative example, the pacing or sensing electrodes are located elsewhere on the lead assembly  200 . In an example, a proximal end portion  235  of the lead assembly coupled is to a pacer, defibrillator, stimulator, or other medical device. In an example, the lead assembly includes a connector  240  at the proximal end  235  of the lead assembly that is sized and shaped to interface with a connector block or other component of a medical device. In an example, the connector is a modified IS-4 terminal that is sized and shaped to couple with the multi-filar coil.  
         [0025]     Turning now to  FIGS. 3A and 3B , an example lead assembly  300  has a multi-filar coil that includes two filars.  FIG. 3A  is a partially cut-away illustration of an example lead assembly  300 .  FIG. 3B  is a cross-section of the lead assembly  300 . The lead assembly  300  includes a lead body  315  and multi-filar coil  301  extending through a lumen  316  in the lead body. In an example, the multi-filar coil  301  includes two filars  305 ,  310 . In an example, the filars  305 ,  310  are approximately coradial, i.e. the filars follow helical paths having approximately the same radius and approximately the same axis. In an example, at least a portion of the helical paths followed by the filars  305 ,  310  have a constant radius and a constant pitch.  
         [0026]     Referring again to  FIGS. 3A and 3B , the lead assembly  300  also includes one or more additional conductors. In the example shown in  FIGS. 3A and 3B , the lead assembly  300  includes two additional conductors  320 ,  325  that extend through second and third lumens  355 ,  360  in the lead body  315 . In an example, the conductors  320 ,  325  are approximately equally spaced from each other and from the multi-filar coil. In an example, the conductors  320 ,  325  are cabled from small diameter wire.  
         [0027]     In an example, the lead assembly  300  is configured as shown in  FIG. 1A  or  FIG. 2 , i.e. the lead assembly has two pacing/sensing electrodes and two defibrillation electrodes. In an example, the coils  305 ,  310  are respectively coupled to the pacing/sensing electrodes, and conductors  320 ,  325  are each coupled to a defibrillation electrode. In an example, one or both of the conductors  320 ,  325  is a cable that includes a plurality or multiplicity of filars.  
         [0028]     Referring now to  FIG. 3C , another example lead assembly  302  includes a multi-filar coil  317  including four filars  370 ,  375 ,  380 ,  385 . Filar  370  contacts filar  375 , filar  375  contacts  380 , and filar  380  contacts filar  385 . There is a gap between filar  385  and filar  370 . In another option, filar  370  contacts filar  385  and the filars define a close tube. At least two of the filars  370 ,  375 ,  380 ,  385  are electrically independent. At least one filar includes a coating of insulation. In an example, all four filars  370 ,  375 ,  380 ,  385  are electrically independent. In another option, two or more filars are electrically connected. In an example, filar  370  is electrically connected with filar  375  and filar  380  is electrically connected to filar  385 . In an example, the lead assembly  302  is configured as shown in  FIG. 1B , i.e. the lead assembly has two defibrillation electrodes respectively coupled to conductors  320 ,  325  and four sensing or pacing electrodes respectively coupled to filars  370 ,  375 ,  380 ,  385 . In another example, one or more filars is not used as a conductor, and is provided to facilitate control of bending and stiffness properties of the lead assembly.  
         [0029]     Referring again to FIGS.  3 A-C, in an example, the lead body  315  includes silicone rubber, polyurethane elastomer, or a fluoropolymer. In an example, one or more of the filars in the multi-filar coil includes a conductive core  330  and an insulative cover  335 . In an example, the conductive core  330  is an alloy such as MP35N with a silver core. In another example, the conductor is platinum-clad tantalum (Pt/Ta), or platinum-clad tantalum with a silver core. In an example, conductors  320 ,  325  also include an insulative outer layer  340  and a conductive core  345 . In an example, the conductive core  345  includes stainless steel, MP35N with a silver core, platinum-clad tantalum, or platinum-clad tantalum with a silver core. In an example, one or both of the conductors  320 ,  325  include drawn brazed strand (DBS®) cable.  
         [0030]     In an example, the electrodes include platinum or titanium coated with IrOx, titanium/nickel (Ti/Ni), black platinum (Pt black) or tantalum oxide. In an example, the lead assembly also includes an outer covering  350  that extends over the lead body  315 . In an example, the outer covering includes ethylene-tetrafluoroethylene (ETFE), polytetrafluoroethylene (PTFE), polyethylene (PE), silicone rubber, or polyurethane. In an example, the lead assembly  300  shown in  FIGS. 3A and 3B  is used to deliver cardiac resynchronization therapy (CRT), neural stimulation, antibradyarrhythmia therapy (e.g. pacing) or antitachyarrhythmia therapy (e.g. defibrillation).  
         [0031]     Referring now to  FIG. 4 , an example method of making a lead assembly including a multi-filar coil is schematically illustrated in a flowchart. At  405 , a first conductor is extended through lead body including at least one lumen. At  410 , a second conductor is extended through the lead body. In an example, the first conductor and/or the second conductor include a multi-wire cable. In an example, the first and second conductors are extended through separate lumens. At  415 , a multi-filar coil is extended through the lead body. The multi-filar coil includes two or more electrically independent coiled filars. In an example, the filars of the multi-filar coil are coradial. In an example, the filars are wound on a mandrel into a coil before the multi-filar coil is extended through the lead body. In an example, the first and second conductors are extended through respective first and second lumens, and the multi-filar coil is extended through a third lumen. At  420 , a first electrode is coupled to the first conductor. At  425 , a second electrode is coupled to the second conductor. At  430 , the filar of the multi-filar coil is coupled to a first sensing or pacing electrode. In an example, the first sensing or pacing electrode is configured for use in both sensing and pacing operations. At  435 , a second filar of the multi-filar coil is coupled to a second sensing or pacing electrode. At  440 , tubing is extended over the lead body. In an example, the tubing makes part or all of the lead body isodiametric. At  445 , the tubing is optionally bonded to the lead body. In an example, the tubing is formed from the same material as the lead body. In an example, the tubing and lead body are formed from silicone or polyurethane. In an example, the tubing is fused to the lead body using heat fusion or laser fusion, for example. In an example, the resulting product is a lead assembly including a lead body, conductors and a multi-filar coil extending through the lead body, and tubing extending over and connected to the lead body. In an example, the resulting lead assembly is isodiametric.  
         [0032]     In an example, the operations illustrated in  FIG. 4  are performed in order starting at the top with  FIG. 4  and progressing downward through  440  or  450 . Alternatively, the operations are performed in a different order. For example, in one option, the multi-filar coil is extended through the lead body before the conductors are extended through the lead body. In an example, fewer than all of the operations are performed. For example, in one option, the extending tubing over the lead body (at  445 ) and the bonding of the tubing to the lead body (at  450 ) are omitted, and the result of the method is a lead body including conductors and a multi-filar coil extending through the lumens.  
         [0033]     Referring now to  FIG. 5 , a cross-sectional illustration of a distal portion of a lead assembly  500  is shown. The lead assembly  500  includes a lead body  505  and a multi-filar coil  510  extending through the lead body  505 . In an example, a driver component  515  with an optional lumen  520  extends through the multi-filar coil  510 . In an example, one filar  525  of the multi-filar coil  510  couples to an electrode  530  which is optionally near a distal end  535  of the lead assembly  500 . A second filar  540  extends past a location where the first filar terminates and couples to a component  545  that is electrically coupled to an active fixation helix  550 .  
         [0034]     The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the scope of the invention, the invention resides in the claims hereinafter appended.