Steerable catheter having intermediate stiffness transition zone

Abstract

A flexible, steerable intravascular catheter includes an elongate flexible shaft having a heterogeneous or multi-zone stiffness profile or structure. A first or distal portion of the catheter shaft may have a substantially constant or distinct stiffness or flexibility, a second, intermediate or transition section is proximal relative to, and less flexible than, the first section, and a third section is proximal relative to, and also less more flexible than, the first section. The third section also includes a substantially constant or distinct stiffness or flexibility. The flexibility or stiffness of the second section varies along its length, e.g., in a substantially linear, step-like or ramp-like manner to provide a smooth or gradual transition between the stiffness of the first or distal section and the flexibility or stiffness of the third or proximal section.

1 . An intravascular steerable catheter, comprising:
 an elongate flexible shaft having a proximal portion and a distal portion, the distal portion of the shaft comprising:
 first, second, and third sections extending in order from a distal end of the distal portion towards the proximal portion, wherein an overall stiffness of the shaft increases from a distal end towards the proximal portion; 
 wherein a stiffness of the second section increases gradually along its entire length from its distal end to its proximal end; 
 wherein the third section includes a distal segment and a proximal segment, the distal segment having a substantially constant stiffness along its length, the proximal segment being stiffer than the distal segment, and the stiffness of the proximal segment increasing gradually along its entire length from its distal end to its proximal end; 
 wherein a rate at which the stiffness changes in the second section is less than a rate at which the stiffness changes in the proximal segment of the third section. 
   
     
     
         2 . The catheter of  claim 1 , wherein the stiffness of the second section increases substantially linearly along its length between the first and third sections in a step-like or ramp-like manner. 
     
     
         3 . The catheter of  claim 1  wherein the first section has a substantially constant stiffness along its length. 
     
     
         4 . The catheter of  claim 1  wherein the first section comprises an internal support member made of a material having a yield strength greater than 120,000 psi. 
     
     
         5 . The catheter of  claim 4 , wherein the support member is made of Type 301 stainless steel. 
     
     
         6 . The catheter of  claim 1 , wherein at least the third section includes a braid. 
     
     
         7 . An intravascular catheter, comprising:
 a handle;   an elongate flexible shaft extending from the handle and having a proximal portion and a distal portion, the distal portion of the shaft comprising, in order from a distal end of the distal portion towards the proximal portion:
 a first sheath; 
 a stiffening sheath connected to a proximal end of the first sheath, the stiffening sheath being stiffer than the first sheath and having a stiffness that increases gradually along its length from its distal end to its proximal end; and 
 a main sheath connected to a proximal end of the stiffening sheath, the main sheath being stiffer than the first sheath and the stiffening sheath, wherein at least one of the first or main sheaths has a stiffness that increases gradually along at least a portion of its length, wherein a rate at which the stiffness changes in the stiffening sheath is less than a rate at which the stiffness changes in the at least one of the first or main sheaths; 
   an electrode carried on the distal portion of the elongate flexible shaft.   
     
     
         8 . The catheter of  claim 7 , wherein the stiffness of the stiffening sheath increases substantially linearly along its length between the first and main sheaths in a step-like or ramp-like manner. 
     
     
         9 . The catheter of  claim 7 , wherein the stiffness of at least a portion of the main sheath varies along its length. 
     
     
         10 . The catheter of claim  129 , the main sheath comprising:
 a distal segment that is adjacent to the stiffening sheath, the distal segment having a substantially constant stiffness along its length; and   a proximal segment that is stiffer than the distal segment, wherein the stiffness of the proximal segment increases gradually along its length from a distal end to a proximal end.   
     
     
         11 . The catheter of  claim 10 , wherein a rate at which the stiffness changes in the stiffening sheath is less than a rate at which the stiffness changes in the proximal segment of the main sheath. 
     
     
         12 . The catheter of  claim 7 , wherein the first sheath has a substantially constant stiffness along its length. 
     
     
         13 . The catheter of  claim 7 , wherein the first sheath includes an internal support member. 
     
     
         14 . The catheter of  claim 13 , wherein the internal support member is made of a material having a yield strength greater than 120,000 psi. 
     
     
         15 . The catheter of  claim 14 , wherein the internal support member is made of Type 301 stainless steel. 
     
     
         16 . The catheter of  claim 7 , wherein the first sheath includes a braid. 
     
     
         17 . An electrophysiology catheter, comprising:
 a handle;   an elongate flexible shaft extending from the handle, the shaft having a proximal portion and a distal portion, the distal portion of the shaft comprising:
 first, second, third, and fourth sections extending in order from a distal end of the distal portion towards the proximal portion, wherein an overall stiffness of the shaft increases from a distal end towards the proximal portion; 
 wherein a stiffness of the second section increases gradually along its entire length from its distal end to its proximal end; 
 wherein the third section includes a distal segment and a proximal segment, the distal segment having a substantially constant stiffness along its length, the proximal segment having a stiffness that increases gradually along its entire length from its distal end to its proximal end, wherein a rate at which the stiffness changes in the second section is less than a rate at which the stiffness changes in the proximal segment of the third section; 
 wherein the fourth section extends from the handle and is stiffer than each of the first, second, and third sections; 
 wherein the electrophysiology catheter is a closed system from the distal end of the distal portion to the handle. 
   
     
     
         18 . The catheter of  claim 17 , wherein the stiffness of the second section increases substantially linearly along its length between the first and third sections in a step-like or ramp-like manner. 
     
     
         19 . The catheter of  claim 17 , wherein at least the first section comprises an internal support member made of a material having a yield strength greater than 120,000 psi. 
     
     
         20 . The catheter of  claim 19 , wherein the support member is made of Type 301 stainless steel.