Patent Abstract:
The invention relates to a steerable catheter having a distal section with reduced variation in deflection path during deflection. The distal section of the catheter includes stripes of different material hardness along the length of the distal section affecting the directionality of catheter deflection upon the application of a deflection force like that applied by pull wires. The stripes result in preferential bending in a desired path with greater reproducibility.

Full Description:
BACKGROUND OF THE INVENTION 
     a. Field of the Invention 
     The instant invention relates to catheters. In particular, the instant invention relates to a catheter with a steerable distal section having reduced variation in planarity during deflection. 
     b. Background Art 
     It is well-known that the pumping action of the heart is controlled by electrical stimulation of myocardial tissue. Stimulation of this tissue in various regions of the heart is controlled by a series of conduction pathways contained within the myocardial tissue. 
     Cardiac arrhythmias arise when the pattern of the heartbeat is changed by abnormal impulse initiation or conduction in the myocardial tissue. Such disturbances often arise from additional conduction pathways which are present within the heart either from a congenital developmental abnormality or an acquired abnormality which changes the structure of the cardiac tissue, such as a myocardial infarction. 
     One of the ways to treat such disturbances is to identify the conductive pathways and to sever part of this pathway by destroying these cells which make up a portion of the pathway. Traditionally, this has been done by either cutting the pathway surgically; freezing the tissue, thus destroying the cellular membranes; or by heating the cells, thus denaturing the cellular proteins. The resulting destruction of the cells eliminates their electrical conductivity, thus destroying, or ablating, a certain portion of the pathway. By eliminating a portion of the pathway, the pathway may no longer maintain the ability to conduct, and the arrhythmia ceases. 
     The success and advancement of current therapies is dependent upon the development and use of more precise localization techniques which allow accurate anatomical determination of abnormal conductive pathways and other arrythmogenic sites. Historically, the electrophysiologist has had to compromise between placing the catheter in the place of greatest clinical interest and areas that are anatomically accessible. 
     One area of advancement in improving localization techniques and accessing additional sites includes the use of curved and steerable catheters. Curved catheters offer improved maneuverability to specific, otherwise inaccessible sites by being shaped specifically to access a particular site. Although perhaps useful for some more accessible sites, the use of this type of catheter has limitations in reaching sites requiring active articulation during placement. Steerable catheters, which may also be pre-curved, proved additional advantages. 
     While steerability of catheters has improved, there is a need to eliminate significant variations in planarity during deflection of the distal tips of catheters. In accordance with this invention, a catheter is provided that addresses and potentially eliminates significant variation in planarity during catheter tip deflection. The invention also offers a catheter capable of a multitude of angular shaft deflection trajectories through a two or three dimensional range including a catheter that could initially be straight and, upon complete deflection, turn into a loop-shaped catheter. This invention would improve product reliability, consistency, and performance, as well as improve safety of electrophysiology ablation or diagnostic procedures. 
     BRIEF SUMMARY OF THE INVENTION 
     It is desirable to eliminate significant variations in planarity during deflection of the distal sections of catheters. In particular, it is desirable to have a catheter capable of a multitude of angular shaft deflection trajectories or paths through a two or three dimensional range. 
     An embodiment of the invention is a catheter comprising a distal section constructed of materials of different material hardness longitudinally placed along the distal section to aid bending deflection of the distal section along a desired path, wherein the materials of different material hardness form a wall creating a lumen, and the distal section has a distal end and a proximal end. 
     The distal section of the catheter may include a softer material placed adjoining a harder material in a lengthwise direction. The width of the softer material may vary in steps or graduations in the lengthwise direction. Alternatively, the hardness of the softer material may vary in a lengthwise direction. The location of the softer material may also vary in a lengthwise direction. Further, multiple pairs or layers of sections, of softer material may provide multiple planes of deflection and asymmetrical shaft deflection. 
     The catheter may further include pullwires fixed in the distal section at the distal end. The pullwires may be further accompanied by a system to provide actuation forces to deflect the distal section of the catheter via a handle actuator. The pullwires may also be aligned with the softer material and the pullwires may be housed within the softer material or within the wall of harder material, proximate to the softer material. The pullwires may also be housed within the lumen. 
     The catheter may further include a component in the distal section to prevent collapse of the wall of the distal section. 
     The catheter may further comprise a braiding material incorporated into the materials of different hardness to provide radial stability in the distal section. 
     The materials of different hardness may be co-extruded, reflowed, thermally bonded, etc. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a distal section of the catheter according to the present invention. 
         FIG. 2  is an end cross-sectional view of the catheter distal section of  FIG. 1 . 
         FIG. 3  is a side view of an embodiment of a catheter distal section according to the present invention having spiral stripes of material having hardness that is different from the remainder of the catheter shaft. 
         FIG. 4(   a ) is a transverse cross-sectional view of the catheter distal section of  FIG. 3  taken along line A-A of  FIG. 3 . 
         FIG. 4(   b ) is a transverse cross-sectional view of the catheter distal section of  FIG. 3  taken along line B-B of  FIG. 3 . 
         FIG. 4(   c ) is a transverse cross-sectional view of the catheter distal section of  FIG. 3  taken along line C-C of  FIG. 3 . 
         FIG. 5(   a ) is a side view of the catheter distal section of  FIG. 3  in an undeflected configuration. 
         FIG. 5(   b ) is a side view of the catheter distal section of  FIG. 3  in an partially deflected configuration. 
         FIG. 5(   c ) is a side view of the catheter distal section of  FIG. 3  in an deflected configuration. 
         FIG. 6  is a side view of an embodiment of a catheter distal section having stepped-width stripes of different material hardness according to the present invention. 
         FIG. 7(   a ) is a transverse cross-sectional view of the catheter distal section of  FIG. 5  taken along line A-A of  FIG. 6 . 
         FIG. 7(   b ) is a transverse cross-sectional view of the catheter distal section of  FIG. 5  taken along line B-B of  FIG. 6 . 
         FIG. 7(   c ) is a transverse cross-sectional view of the catheter distal section of  FIG. 5  taken along line C-C of  FIG. 6 . 
         FIG. 8(   a ) is a side view of the catheter distal section of  FIG. 6  in an undeflected configuration. 
         FIG. 8(   b ) is a side view of the catheter distal section of  FIG. 6  in an partially deflected configuration. 
         FIG. 8(   c ) is a side view of the catheter distal section of  FIG. 6  in an deflected configuration. 
         FIG. 9  is a side view of an embodiment of a catheter distal section having stripes of different material hardness according to the present invention. 
         FIG. 10(   a ) is a transverse cross-sectional view of the catheter distal section of  FIG. 9  taken along line A-A of  FIG. 9 . 
         FIG. 10(   b ) is a transverse cross-sectional view of the catheter distal section of  FIG. 9  taken along line B-B of  FIG. 9 . 
         FIG. 10(   c ) is a transverse cross-sectional view of the catheter distal section of  FIG. 9  taken along line B-B of  FIG. 9 . 
         FIG. 11(   a ) is a side view of the catheter distal tip of  FIG. 9  in an undeflected configuration. 
         FIG. 11(   b ) is a side view of the catheter distal tip of  FIG. 9  in an partially deflected configuration. 
         FIG. 11(   c ) is a side view of the catheter distal tip of  FIG. 9  in a further deflected configuration. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Several embodiments of a catheter distal tip deflection apparatus are depicted in the figures. As described further below, the catheter distal tip deflection apparatus according to the present invention provides a number of advantages, including, for example, reducing or eliminating significant variation in deflection path during shaft deflection, the ability to construct a catheter capable of a multitude of angular shaft deflection trajectories through a two or three dimensional range, improved product reliability, improved consistency and performance, and improved safety of electrophysiology ablation and diagnostic procedures. 
     Referring to  FIGS. 1 and 2 , a single axis steerable catheter distal section  100  is disclosed in accordance with this invention. The catheter distal section  100  comprises a tubular body  102  defining a lumen or bore  104 , and a tip electrode  120 . As shown in  FIG. 2 , which is a transverse cross-sectional view of the tubular body  102 , the tubular body  102  may comprise an inner coil  106 , a PTFE sleeve  108  outside the inner coil  106 , and a braiding material  110  within a polymer sleeve  111  and two longitudinally-extending stripes  112  of material that is different from the remainder of the material of polymer sleeve  111  outside the PTFE sleeve  108 . The stripes  112  are offset 180° from each other and are made of material having a lower durometer than that of the polymer sleeve  111 . The stripes  112  may be located along the polymer sleeve  111  by co-extrusion, although those skilled in the art will understand that other means of fabrication are possible. The polymer sleeve  111  may be constructed from 50-55D Pebax®, while the stripes  112  may be constructed from 35-40D Pebax®. The braiding may be stainless steel or Kevlar®, for example. Although referred to as the “PTFE sleeve  108 ,” the sleeve  108  may be made of any material with similar qualities. The inner coil  106  helps to prevent collapse of catheter distal tip  100  when it is deflected. 
     Inside the tubular body  102 , in the plane formed by stripes  112 , are two or more pullwire sleeves  114  to house multiple pullwires  116 . Alternatively, the pullwire sleeves may instead be imbedded in the stripes  112 , the stripes  112  constructed in such a manner to house the pullwires  116 . The pullwire sleeves  114  maybe made of a number of polymers or rubbers. The pullwire sleeves  114  house the pullwires  116 , which run the length of the catheter body to a control means at the proximal end of the catheter body and may be anchored at or near the tip electrode  120 . The distal section may further comprise a compression coil to maintain circumferential integrity and facilitate deflection. Exemplary control means are shown in U.S. Pat. Nos. 5,395,329; 5,861,024; and 6,308,090; the disclosures of which are incorporated herein by reference. 
     The difference in durometer between the polymer sleeve  111  and the stripes  112 , combined with the location of the pullwires  116  in the same plane as the stripes  112  180° apart ensures angular deflection of catheter distal section  100  because the lower durometer stripes  112  stretch and compress more readily than the higher durometer polymer sleeve  111 . Thus, tension on one of the pullwires  116  causes the catheter tip  100  to bend in the plane defined by stripes  112 . 
     Although not shown, the catheter distal section  100  could have two pairs each of stripes and pullwires, allowing a user to deflect the catheter distal section in two separate planes. In this embodiment, the stripes and pullwires would be spaced equidistant across the circumference of the catheter distal section. Manipulation of the first pair of pullwires would deflect the catheter distal section along a first plane, while manipulation of the second pair of pullwires would deflect the catheter distal section along a second plane. 
     Signal wires for supplying energy to the tip electrode  120  are not shown, but can be located in the lumen  104 . The distal section may comprise multiple lumen  104 . 
     While the embodiment of  FIGS. 1 and 2  has straight stripes  112 ,  FIGS. 3 and 4(   a )-( c ) show a catheter distal section  300 , with spiral or helical stripes  312  of lower durometer than the durometer of the polymer sleeve  311 . 
       FIG. 3  shows the outside of the tubular body  302  of the catheter distal section  300 , showing the stripes  312  spiraling around the polymer sleeve  311 . Three transverse cross-sections, A-A, B-B, and C-C are cut at various points along the length of the catheter distal section  300 . The corresponding transverse cross-sectional views are shown at  FIGS. 4(   a )-( c ), respectively. 
     As shown in  FIGS. 4(   a )-( c ), the tubular body  302  may comprise an inner coil  306 , a PTFE sleeve  308  around the outside of inner coil  306 , and a braiding material  310  within the polymer sleeve  311  or alternatively, at the inside diameter of the polymer sleeve  311 , and the two stripes  312  around the outside of the PTFE sleeve  308 . The stripes  312  are located 180° from each other along the circumference of the distal section  300  and are made of lower durometer material than the material from which the polymer sleeve  311  is constructed. For example, the polymer sleeve  311  may be 50-55D Pebax®, while the stripes  312  may be 35-40D Pebax®. The braiding may be stainless steel or Kevlar®, for example. Although referred to as the “PTFE sleeve  308 ,” the sleeve  308  may be made of any material with qualities similar to those described herein. The inner coil  306  helps to prevent collapse of the catheter distal tip  300  when it is deflected. 
     Rather than having separate pullwire sleeves inside the tubular body  302 , the pullwire sleeves  314  are integral with the stripes  312  in the embodiment depicted in  FIGS. 3 and 4(   a ). The pullwire sleeves  314  house the pullwires  316 , which run the length of the catheter body to a control means at the proximal end of the catheter body and may be anchored at or near the electrode  320 . 
     The construction of the stripes  312  with a material of lower durometer than the material of the polymer sleeve  311 , in combination with the spiral arrangement of co-extruded stripes  312  around the polymer sleeve  311 , allow a user to form complex curves along multiple planes with the catheter distal section by pulling the pullwires  316  as shown in  FIGS. 5(   a )-( c ). 
       FIGS. 6 ,  7 ( a )-( c ), and  8 ( a )-( c ) show another embodiment of a catheter according to the present invention. Referring to  FIGS. 6 ,  7 ( a )-( c ), and  8 ( a )-( c ), a single-axis steerable catheter distal section  500  is disclosed. The catheter distal tip  500  comprises a tubular body  502  defining a lumen or bore  504 , and a tip electrode  520 . Transverse cross-sections A-A, B-B, and C-C are cut at various points along the length of catheter distal tip  500 . The corresponding cross-sectional views are shown at  FIGS. 7(   a )-( c ), respectively. 
       FIGS. 7(   a )-( c ) are transverse cross-sectional views of tubular body  502 . Tubular body  502  may comprise an inner coil  506 , a PTFE sleeve  508  around the outside of inner coil  506 , and a braiding material  510  within a polymer sleeve  511  or alternatively, at the inside diameter of the polymer sleeve  511 , and the two stripes  512  along the outside of the PTFE sleeve  508 . The stripes  512  are located 180° from each other along the circumference of the distal section  500  and are made of a matrix having lower durometer than the durometer of the material from which the polymer sleeve  511  is constructed. For example, the polymer sleeve  511  may be 50-55D Pebax®, while the stripes  512  may be 35-40D Pebax®. The braiding may be stainless steel or Kevlar®, for example. Although referred to as the “PTFE sleeve  508 ,” the sleeve  508  may be made of any material with similar qualities to those described herein. Inner coil  506  helps to prevents collapse of catheter distal section  500  when it is deflected. 
     As shown in  FIGS. 6 and 7(   a )-( c ), the width of the stripes  512  is greater closer to the tip electrode  520  at the distal end of catheter distal section  500  when compared to the width of the stripes  512  at the proximal end of the distal section  500 . A greater width of stripes  512  provides for greater deflection of the catheter distal section  500  near the distal end for a given tension on a pullwire  516  when compared to the same section of the catheter distal section  500  with stripes  512  of narrower width. 
     The pullwire sleeves  514  are shown embedded in stripes  512 , although they also could be located inside the tubular body  502  as in the embodiment shown in  FIGS. 1 and 2 . The pullwire sleeves  514  house the pullwires  516 , which run the length of the catheter body to a control means at the proximal end of the catheter body and may be anchored at or near the electrode  520 . The stripes  512  may also be constructed of materials varying in durometer to produce the same effect. 
       FIGS. 8(   a )-( c ) show the distal end of the catheter distal section  500  deflected as a result of pulling a pullwire  516 . The angular deflection of distal end of the distal section  500  increases with increased width of stripes  512 —in this case moving toward the distal end of the catheter distal section  500 , approaching the tip electrode  520 . 
     Although not shown, the catheter distal section  500  could have two pairs each of stripes (four total) and pullwires, allowing a user to deflect the catheter distal section in two separate planes. In this embodiment, the stripes and pullwires would be spaced equidistant across the circumference of the catheter distal section. Manipulation of the first pair of pullwires would deflect the catheter distal section along a first plane, while manipulation of the second pair of pullwires would deflect the catheter distal section along a second plane. 
       FIGS. 9 ,  10 ( a )-( c ), and  11 ( a )-( c ) show another embodiment of the catheter construction according to the present invention. Referring to  FIGS. 9 ,  10 ( a )-( c ), and  11 ( a )-( c ), a single-axis steerable catheter distal section  800  is shown. The catheter distal section  800  may comprise a tubular body  802  defining a lumen or bore  804 , and a tip electrode  820 . Transverse cross-sections A-A, B-B, and C-C are cut at various points along the length of catheter distal section  800 . The corresponding cross-sectional views are shown at  FIGS. 10(   a )-( c ), respectively. 
       FIGS. 10(   a )-( c ) are transverse cross-sectional views of tubular body  802 . The tubular body  802  comprises an inner coil  806 , a PTFE sleeve  808  around the outside of the inner coil  806 , and a braiding material  810  within a polymer sleeve  811 , or alternatively, at the inside diameter of the polymer sleeve  811 , and the two stripes  812  (including stripe sections  812   a ,  812   b , and  812   c ) on the outside of the PTFE sleeve  808 . The stripes  812   a ,  812   b , and  812   c  are located equidistant from each other across the circumference of the tubular body  802  and are made of lower durometer material than the material from which the polymer sleeve  811  is constructed. For example, the polymer sleeve  811  may be made of 50-55D material, while the stripes  812   a ,  812   b , and  812   c  may be made of material of 50D, 40D, and 35D, respectively. The braiding may be stainless steel or Kevlar®, for example. Although referred to as the “PTFE sleeve  808 ,” the sleeve  808  may be made of any material with similar qualities to those described herein. The inner coil  806  helps to prevent collapse of catheter distal tip  100  when it is deflected. 
     As stated above, the Durometer of the stripes  812   a ,  812   b , and  812   c  may decrease in steps as they are located closer to the tip electrode  820  at the distal end of catheter distal section  800 . The angular deflection of distal end of the distal section  800  increases with decreased durometer of the stripes  812   a ,  812   b , and  812   c —in this case moving toward the distal end of the catheter distal section  800 , approaching the tip electrode  820 . 
     The pullwire sleeves  814  are shown embedded in the stripes  812 , although they also could be located inside the tubular body  802  as in the embodiment shown in  FIGS. 1 and 2 . The pullwire sleeves  814  house the pullwires  816 , which run the length of the catheter body to a control means at the proximal end of the catheter body and may anchored at or near electrode  820 . 
     Although not shown, the catheter distal section  800  could have two pairs each of stripes and pullwires, allowing a user to deflect the catheter distal section in two separate planes. In this embodiment, the stripes and pullwires would be spaced equidistant across the circumference of the catheter distal section. Manipulation of the first pair of pullwires would deflect the catheter distal section along a first plane, while manipulation of the second pair of pullwires would deflect the catheter distal section along a second plane. 
     Although the embodiments described above specifically describe the tip of the catheter, it will be understood by those skilled in the art that the catheter tip is only a portion of a complete system that may also include, e.g., control means or an irrigation system. In addition, rather than using an electrode for ablation, the catheter may use ultrasonic methods of ablation. The catheter tip disclosed may be used for any purpose for which a medical catheter is used including, but not limited to, diagnostics. It will further be understood by those skilled in the art that the present invention may be sold as a kit including other elements used with the catheter such as electronic components used in imaging. 
     Although several embodiments of this invention have been described above with a certain degree of particularity, those skilled in the art could make numerous alterations to the disclosed embodiments without departing from the spirit or scope of this invention. Joinder references (e.g., attached, coupled, connected, and the like) are to be construed broadly and may include intermediate members between a connection of elements and relative movement between elements. As such, joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting. Changes in detail or structure may be made without departing from the spirit of the invention as defined in the appended claims.

Technology Classification (CPC): 0