Heat transfer through a catheter tip

Abstract

Methods are disclosed which involve a catheter having a distal end that includes electrically and thermally conducting inner and outer layers, a polymer layer between the inner and outer layers, thermal bridges selectively positioned between the inner and outer layers through the polymer layer to transfer heath between the two layers through the polymer layer. An ablation method includes inserting the distal end into a body of a subject, contacting tissue with the outer layer, passing ablation current via the outer layer into tissue such that heat is transferred to the inner layer via the thermal bridges, and passing irrigation fluid through irrigation channels through the inner layer, outer layer, and polymer layer to evacuate heath from the inner layer into blood.

What is claimed is: 
     
         1 . A method, comprising:
 inserting, into a body of a subject, a distal end of a catheter, the distal end comprising:
 an electrically and thermally conducting outer layer, 
 an electrically and thermally conducting inner layer, 
 a polymer layer between the inner and outer layer, 
 a plurality of irrigation channels through the inner layer, the outer layer, and the polymer layer, and 
 a plurality of thermal bridges selectively positioned between the inner and outer layers and through the polymer layer such that the outer layer comprises a conductive path between and joining the thermal bridges, and the inner layer comprises a conductive path between and joining the thermal bridges; 
   subsequently to inserting the distal end of the catheter into the body of the subject, contacting tissue of the subject with the outer layer;   while contacting the tissue, passing an ablation current, via the outer layer, into the tissue, such that heat is generated in the tissue and is transferred, via the thermal bridges, to the inner layer; and   evacuating heat, from the inner layer, into blood of the subject, by passing an irrigating fluid through the plurality of irrigation channels.   
     
     
         2 . The method according to  claim 1 , further comprising:
 orienting the distal end of the catheter at either a 45° or 90° angle to the tissue;   penetrating the tissue to a penetration depth; and   ablating tissue, through the distal end of the catheter, with the ablation current for a predetermined duration of time under a predetermined safety temperature.   
     
     
         3 . The method according to  claim 2 , wherein the penetration depth is approximately about 0.8 mm. 
     
     
         4 . The method according to  claim 2 , wherein the step of ablating tissue results in a lesion depth of approximately about 5.6 mm at ablation current about 0.63 Amperes. 
     
     
         5 . The method according to  claim 2 , wherein the step of ablating tissue results in a lesion width of approximately about 8.9 mm at ablation current about 0.63 Amperes. 
     
     
         6 . The method according to  claim 2 , wherein the predetermined duration of time is at least about 30 seconds and the ablation current is about 0.63 Amperes whereby the throughout ablation the catheter maintains an ablation zone less than or equal to approximately about 130° C. thereby avoiding tissue rupture. 
     
     
         7 . The method according to  claim 2 , wherein the step of ablating tissue results in at least about a 93% improvement in lesion width versus a standard flex circuit ablation catheter where an ablation current is approximately 0.63 Amperes. 
     
     
         8 . The method according to  claim 2 , wherein the step of ablating tissue results in at least about a 500% improvement in clinically safe ablation time versus a standard flex circuit ablation catheter where an ablation current is about 0.63 Amperes. 
     
     
         9 . The method according to  claim 2 , wherein the step of ablating tissue results in at least about an 85% improvement in lesion depth versus a standard flex circuit ablation catheter where an ablation current is about 0.63 Amperes. 
     
     
         10 . The method according to  claim 2 , wherein the predetermined duration of time is at least about 5 seconds and the ablation current is about 0.90 Amperes whereby the throughout ablation the catheter maintains an ablation zone less than or equal to approximately about 130° C. thereby avoiding tissue rupture. 
     
     
         11 . The method according to  claim 2 , wherein the step of ablating tissue results in at least about a 60% improvement in lesion width versus a standard flex circuit ablation catheter where an ablation current is about 0.90 Amperes. 
     
     
         12 . The method according to  claim 2 , wherein the step of ablating tissue results in at least about a 160% improvement in clinically safe ablation time versus a standard flex circuit ablation catheter where an ablation current is about 0.90 Amperes. 
     
     
         13 . The method according to  claim 2 , wherein the step of ablating tissue results in at least about an 38% improvement in lesion depth versus a standard flex circuit ablation catheter where an ablation current is about 0.90 Amperes. 
     
     
         14 . The method according to  claim 2 , wherein the step of ablating tissue results in a lesion depth of approximately about 3.6 mm at ablation current about 0.90 Amperes. 
     
     
         15 . The method according to  claim 2 , wherein the step of ablating tissue results in a lesion width of approximately about 6.9 mm at ablation current about 0.90 Amperes. 
     
     
         16 . A method, comprising:
 drilling a plurality of thermal bridges, through a flexible thermally-insulating polymer substrate; and   using a thermally-conducting metal to sandwich the flexible thermally-insulating polymer substrate, over an inner surface and an outer surface of the polymer substrate such that the thermally-conducting metal comprises columns filling the thermal bridges, an outer layer covering at least a part of the outer surface and comprising a conductive path on the outer surface between and joining the columns, and an inner layer covering at least a part of the inner surface and comprising a conductive path on the inner surface between and joining the columns.   
     
     
         17 . The method according to  claim 16 , further comprising: drilling a plurality of irrigation holes through the inner and outer layers and the thermally-insulating polymer substrate, the irrigation holes having a diameter larger than the thermal bridges. 
     
     
         18 . The method according to  claim 16 , further comprising:
 bonding the thermally-conducting metal that covers the inner layer to a supporting structure of an ablation catheter; and   shaping the substrate and the supporting structure to define an interior lumen.   
     
     
         19 . The method according to  claim 18 , wherein shaping the substrate and the supporting structure comprises shaping the substrate and the supporting structure to define a thimble that contains the interior lumen; and
 coupling the supporting structure to a distal end of a catheter configured for insertion into a body of a subject.