Brush electrode and method for ablation

Abstract

A brush electrode and a method for using the brush electrode for tissue ablation are disclosed. The brush electrode comprises a plurality of flexible filaments or bristles for applying ablative energy (e.g., RF energy) to target tissue during the formation of spot or continuous linear lesions. Interstitial spaces are defined among the filaments of the brush electrode, and the interstitial spaces are adapted to direct conductive or nonconductive fluid, when present, toward the distal ends of the brush filaments. The brush electrode facilitates electrode-tissue contact in target tissue having flat or contoured surfaces. The flexible filaments may be selectively trimmed to give a desired tip configuration or a desired standoff distance between the tissue and the conductive filaments in the brush electrode. Also, the filaments may be grouped into clusters. A shielded-tip brush electrode, including a flexible boot, is also disclosed.

1 . A wet-brush electrode that facilitates electrode-tissue contact in target tissue having contoured surfaces, the wet-brush electrode comprising 
 a plurality of flexible filaments adapted to transfer ablative energy to target tissue, said plurality of flexible filaments defining interstitial spaces among said plurality of flexible filaments, wherein said interstitial spaces are adapted to carry conductive fluid;    a primary conductor operatively connected to, and adapted to transfer ablative energy to, said plurality of flexible filaments; and    a fluid-delivery means adapted to deliver conductive fluid to said interstitial spaces.    
   
   
       2 . The catheter of  claim 1 , wherein at least one flexible filament comprising said plurality of flexible filaments has a distal end, and wherein at least one of said plurality of flexible filaments taper, towards said distal end of said at least one of said flexible filaments.  
   
   
       3 . The catheter of  claim 1 , wherein said plurality of flexible filaments comprises a conductive filament and a nonconductive filament.  
   
   
       4 . The catheter of  claim 1 , further comprising an embedded device selected from the group consisting of a thermocouple, a pressure sensor, and an ultrasound sensor.  
   
   
       5 . The catheter of  claim 1 , further comprising an outer sheath.  
   
   
       6 . The catheter of  claim 5 , wherein said outer sheath comprises a concentric ring of sub-channels around a main channel, and wherein at least a portion of said plurality of flexible filaments resides in said main channel.  
   
   
       7 . A catheter for ablating tissue inside a human body, the catheter comprising 
 an outer sheath having a distal sheath end;    a conforming electrode adapted to apply ablative energy to target tissue, said conforming electrode comprising an embedded portion and an exposed portion, wherein said exposed portion has a distal electrode end, wherein a working surface is present at said distal electrode end of said exposed portion, and wherein said exposed portion extends from said distal electrode end of said outer sheath; and    a primary conductor in direct electrical contact with said conforming electrode and adapted to carry ablative energy from an energy source to said conforming electrode.    
   
   
       8 . The catheter of  claim 7 , wherein said conforming electrode comprises a brush electrode having a plurality of flexible filaments.  
   
   
       9 . The catheter of  claim 8 , wherein said plurality of flexible filaments comprises conductive filaments having longitudinal axes, and wherein said conductive filaments have varying conductivity along said longitudinal axes.  
   
   
       10 . The catheter of  claim 9 , wherein said filaments are coated with materials having different electrical conductivity at different locations along said conductive filaments.  
   
   
       11 . The catheter of  claim 9 , wherein said conductivity varies continuously.  
   
   
       12 . The catheter of  claim 11 , wherein said brush electrode comprises tapered filaments.  
   
   
       13 . The catheter of  claim 12 , wherein at said distal sheath end, said tapered filaments have larger cross-sectional areas than said tapered filaments have at said distal electrode end.  
   
   
       14 . The catheter of  claim 13 , wherein said outer sheath further comprises a lumen adapted to carry a conductive fluid from a fluid supply to interstitial gaps among said plurality of flexible filaments, and wherein said conductivity of said plurality of flexible filaments is adapted to match a conductivity of said conductive fluid at said distal ends of said filaments.  
   
   
       15 . The catheter of  claim 8 , wherein said outer sheath further comprises a circumferential ring of sub-channels around a main channel, and wherein said plurality of flexible filaments extends in said main channel.  
   
   
       16 . The catheter of  claim 15 , wherein said sub-channels are adapted to carry fluid.  
   
   
       17 . The catheter of  claim 8 , wherein said outer sheath surrounding said plurality of flexible filaments is porous adjacent to an exposed portion of said brush electrode.  
   
   
       18 . The catheter of  claim 8 , wherein a threaded sheath surrounds said plurality of flexible filaments, said threaded sheath having an outer surface and a spiral ridge on said outer surface.  
   
   
       19 . The catheter of  claim 18 , wherein said catheter further comprises a covering around at least a portion of said threaded sheath, thereby defining a helical flow channel between said threaded sheath and said covering, wherein said helical flow channel is adapted to deliver fluid to tissue adjacent to said brush electrode.  
   
   
       20 . The catheter of  claim 8 , wherein a grooved sheath surrounds said plurality of flexible filaments of said brush electrode, said grooved sheath having an outer surface and at least one longitudinally-extending groove formed on said outer surface of said grooved sheath.  
   
   
       21 . The catheter of  claim 20 , wherein said catheter further comprises a covering around at least a portion of said grooved sheath, thereby defining at least one longitudinally-extending flow channel between said grooved sheath and said covering, wherein said longitudinally-extending flow channel is adapted to deliver fluid to tissue adjacent to said brush electrode.  
   
   
       22 . The catheter of  claim 8 , wherein said outer sheath provides mechanical support for said plurality of flexible filaments and provides electrical shielding for said plurality of flexible filaments.  
   
   
       23 . The catheter of  claim 8 , wherein said outer sheath further comprises a lumen adapted to carry conductive fluid from a fluid source to said brush electrode.  
   
   
       24 . The catheter of  claim 23 , wherein said lumen has a configuration selected from the group consisting of a single, embedded channel; a plurality of sub-channels; a helical channel; and at least one longitudinally-extending groove.