High impedance electrode tip

Abstract

An implantable lead, being either a fixed or retractable/extendable lead, having a distal tip electrode is adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity. The electrode includes a mechanical fastener such as a fixation helix for securing the electrode to cardiac tissue, which may or may not be electrically active. The implantable electrode with a helical tip includes an electrode which has a distal end and a proximal end. A helix is disposed within the electrode, where the helix is aligned along a radial axis of the electrode. The electrode further includes one or more of the following features: the helix having a coating of an insulating material on a surface of the helix, a porous conductive surface at a base of the helix, or a porous conductive element at the end of the electrode having an insulating coating covering from 5-95% of the surface of the porous conductive element. The electrode may further include an electrode tip having a porous electrical conductive element, such as a mesh screen, disposed on a surface at the distal end of the electrode tip, which can be used as a sensing or pacing interface with the cardiac tissue.

What is claimed:  
     
         1 . An implantable electrode with a helical tip comprising: 
 an electrode having a distal end and a proximal end; and    a helix disposed on said electrode, which helix is aligned along a radial axis of the electrode at said distal end; and    said implantable electrode having at least one feature selected from the group consisting of: 
 a) said helix having a coating of an insulating material on 5-95% of its surface,  
 b) said helix having at least part of its surface beyond said distal end of said electrode and said distal end of said electrode having a porous conductive surface,  
 c) a conductive porous surface at said distal end of said electrode, and  
 d) a porous conductive surface at the distal end of the electrode having an insulating coating covering from 5-95% of the surface of said porous conductive surface.  
   
     
     
         2 . The implantable electrode of  claim 1 , wherein said helix has a coating of insulating material on it surface which covers from 5-95% of surface area of said helix beyond the distal end of the electrode.  
     
     
         3 . The implantable electrode of  claim 1 , wherein said helix has a coating of insulating material on it surface which covers from 10-90% of surface area of said helix beyond the distal end of the electrode.  
     
     
         4 . The implantable electrode of  claim 1 , wherein said porous conductive surface at said distal end of said electrode comprises a mesh, wherein said mesh comprises an electrically conducting surface.  
     
     
         5 . The implantable electrode of  claim 4 , wherein said mesh is electrically active.  
     
     
         6 . The implantable electrode of  claim 1 , wherein said helix is electrically active.  
     
     
         7 . The implantable electrode as recited in  claim 1 , wherein said helix is electrically inactive.  
     
     
         8 . The implantable electrode as recited in  claim 7 , wherein said helix is made electrically inactive by forming the helix from a highly resistant material.  
     
     
         9 . The implantable electrode of  claim 1  wherein said helix has a coating of an insulating material on 5-95% of its surface.  
     
     
         10 . The implantable electrode of  claim 1 , wherein said helix has at least part of its surface beyond said distal end of said electrode and said distal end of said electrode having a porous conductive surface.  
     
     
         11 . The implantable electrode of  claim 1 , wherein a conductive porous surface is at said distal end of said electrode.  
     
     
         12 . The implantable electrode of  claim 1 , wherein a porous conductive surface at the distal end of the electrode has an insulating coating covering from 5-95% of the surface of said porous conductive surface.  
     
     
         13 . A distal tip electrode adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity, said electrode comprising: 
 an electrode tip;    a porous conductive element disposed at a distal end of the electrode tip;    a surface area at the distal end of the electrode tip,    a helix disposed within said electrode, said helix comprising a conductor disposed in a helical shape, wherein said helix travels along radial axis of the electrode through said surface area; and    a helix guiding mechanism for directing movement of the helix during travel.    
     
     
         14 . A distal tip electrode as recited in  claim 13 , wherein said porous conductive element comprises a mesh screen.  
     
     
         15 . The distal tip electrode as recited in  claim 14 , wherein said mesh screen is electrically active.  
     
     
         16 . The distal tip electrode as recited in  claim 13 , wherein said helix is aligned with a radial axis of the electrode.  
     
     
         17 . The distal tip electrode as recited in  claim 13 , wherein said helix is electrically active.  
     
     
         18 . The distal tip electrode as recited in  claim 13 , wherein said helix is electrically inactive.  
     
     
         19 . The distal tip electrode as recited in  claim 18 , wherein said helix is made electrically inactive by an insulating coating.  
     
     
         20 . The distal tip electrode as recited in  claim 18 , wherein said helix is made electrically inactive by forming the helix from a highly resistant material.  
     
     
         21 . The distal tip electrode as recited in  claim 13 , wherein said helix is seated within said electrode tip.  
     
     
         22 . The distal tip electrode as recited in  claim 21 , wherein said porous conductive element has a hole therein for guidance of said helix.  
     
     
         23 . The distal tip electrode as recited in  claim 13 , wherein said helix guiding mechanism comprises a guiding bar.  
     
     
         24 . The distal tip electrode as recited in  claim 23 , wherein said guiding bar comprises a cylinder disposed proximate to said surface.  
     
     
         25 . The distal tip electrode as recited in  claim 23 , wherein said guiding bar is disposed transverse to said radial axis of said electrode.  
     
     
         26 . The distal tip electrode as recited in  claim 13 , wherein said porous conductive element comprises an annular ring, said annular ring having an open center.  
     
     
         27 . A distal tip electrode adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity, said electrode comprising: 
 an electrode tip;    a porous conductive element disposed at a distal end of the electrode tip, said porous conductive element forming a surface;    a protuberance extending from said porous conductive element;    a helix disposed within said electrode, said helix comprises a conductor disposed in a helical shape, wherein said helix travels along radial axis of the electrode through said surface; and    a helix guiding mechanism for directing movement of the helix during travel.    
     
     
         28 . The distal tip electrode as recited in  claim 27 , wherein said protuberance is disposed along said radial axis.  
     
     
         29 . The distal tip electrode as recited in  claim 27 , wherein said helix guiding mechanism comprises a groove disposed within said porous conductive element.  
     
     
         30 . The distal tip electrode as recited in  claim 27 , wherein said protuberance is positioned such that said helix coils around said protuberance during travel.  
     
     
         31 . The distal tip electrode as recited in  claim 27 , wherein said projection has a generally cylindrical cross-section.  
     
     
         32 . A distal tip electrode adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity, said electrode comprising: 
 an electrode tip;    a mesh screen disposed at a distal end of the electrode tip;    a surface at the distal end of the electrode tip;    a fixation device disposed within said electrode, said fixation device adapted for travel along radial axis of the electrode through said surface;    a guiding mechanism for directing movement of the fixation device during travel; and    a movement assembly, said movement assembly for providing movement to said fixation device.    
     
     
         33 . The distal tip electrode as recited in  claim 32 , wherein said fixation device comprises a helix.  
     
     
         34 . The distal tip electrode as recited in  claim 32 , wherein said movement assembly comprises a piston.  
     
     
         35 . The distal tip electrode as recited in  claim 34 , wherein the piston has a slot therein, and the base further comprises a knob, said slot for mating with said knob.  
     
     
         36 . The distal tip electrode as recited in  claim 34 , wherein the slot is mated with said knob to form a stop mechanism for said fixation device.  
     
     
         37 . The distal tip electrode as recited in  claim 32 , wherein the mesh screen has a groove guide disposed therein.  
     
     
         38 . The distal tip electrode as recited in  claim 34 , wherein said distal tip electrode further comprises a seal, said seal disposed between said piston and said base.  
     
     
         39 . An electrode adapted for implantation on or about the heart and for connection to a system for monitoring or stimulating cardiac activity, said electrode comprising: 
 a lead body having a first end and a second end;    an electrode disposed proximate the first end of the lead body;    connector terminal disposed at said second end of the lead body, said connector terminal for connecting with a pulse generating unit;    an electrode tip disposed proximate one end of the electrode;    a surface at the distal end of the electrode tip, said surface further comprising an electrical conducting surface wherein said surface is comprised of a porous conductive element;    a helix disposed within said electrode, said helix comprising a conductor disposed in a helical shape, wherein said helix travels along radial axis of the electrode through said surface thereby placing said helix in extension and retraction; and    a helix guiding groove for directing movement of the helix during extension and retraction of said helix.    
     
     
         40 . A system for delivering signals to the heart, said system comprising: 
 an electronics system including a cardiac activity sensor and a signal generator for producing signals to stimulate the heart; and    a lead adapted for implantation heart, said lead comprising: 
 an electrode tip;  
 a porous conductive element disposed at a distal end of the electrode tip;  
 a surface at the distal end of the electrode tip,  
 a helix disposed within said electrode, said helix comprises a conductor disposed in a helical shape, wherein said helix travels along radial axis of the electrode through said surface; and  
 a helix guiding mechanism for directing movement of the helix during travel.  
   
     
     
         41 . A tip electrode, comprising: 
 a fixation helix having a surface with an electrically insulating coating thereon which electrically insulating coating covers less than all of the surface of said fixation helix.    
     
     
         42 . The tip electrode of  claim 41 , wherein the surface of said fixation helix with an insulating coating thereon comprises 5-95% of said which is coated with an aqueous insoluble insulating layer so that 95-5% of said surface is electrically conductive.  
     
     
         43 . The tip electrode of  claim 41 , further comprising a circumferential steroid eluting matrix.  
     
     
         44 . The tip electrode of  claim 43 , wherein the circumferential steroid eluting matrix is tapered.  
     
     
         45 . The tip electrode of  claim 43 , further comprising a cylindrical polymeric tubing.  
     
     
         46 . The tip electrode of  claim 42 , wherein the electrically insulating coating comprises PARYLENE.