Abstract:
A bi-directional electrophysiology catheter having improved steerability which includes orientation sheaths, or thin walled tubes, placed in diametrically opposed lumen at the distal portion of the catheter for producing in-plane deflection of the distal portion of the catheter.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to an improved steerable electrophysiology catheter having a mechanism in the distal tip of the catheter to orient deflection.  
       BACKGROUND OF THE INVENTION  
       [0002]     Electrophysiology catheters have been in common use in medical practice for many years. Such catheters are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.  
         [0003]     In use, the electrophysiology catheter is inserted into a major vein or artery, e.g., femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical and largely determines how useful the catheter is.  
         [0004]     Steerable (or deflectable) electrophysiology catheters are generally well known. For example, U.S. Pat. No. Re. 34,502 describes a catheter having a control handle comprising a housing having a piston chamber at its distal end. A piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston and through the catheter body. The distal end of the puller wire is anchored in the tip section of the catheter. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section.  
         [0005]     Often it is desirable to have a bidirectional steerable catheter, i.e., a catheter that can be deflected in two directions, typically opposing directions. For example, U.S. Pat. No. 6,210,407 discloses a bidirectional steerable catheter having two puller wires extending through the catheter. The distal ends of the puller wires are anchored to opposite sides of the tip section of the catheter. A suitable bidirectional control handle is provided that permits longitudinal movement of each puller wire to thereby allow deflection of the catheter in two opposing directions.  
         [0006]     Regardless of whether the catheter is unidirectional or bidirectional, it is typically preferred that the tip section can be deflected in the plane of the catheter so that the catheter can be more precisely controlled in the heart. However, because the tip section is generally made of a flexible material, it is sometimes difficult to limit out-of-plane deflection. Accordingly, a need exists for a catheter having a tip section that can be consistently deflected within a single plane of the catheter.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention is directed to an improved electrophysiology steerable catheter having orientation sheaths, or tubes, extending through the distal end to improve deflection. More particularly, the catheter includes an elongated, flexible tubular catheter body having proximal and distal ends and a lumen extending therethrough. A tip section is provided at the distal end of the catheter body. The tip section includes flexible plastic tubing having first and second pairs of diametrically opposed lumens extending therethrough. The first pair of diametrically opposed lumens are generally perpendicular to the second pair of diametrically opposed lumens. A control handle is mounted at the proximal end of the catheter body. The catheter further includes first and second puller wires, each extending through one of the lumens of the first pair of diametrically opposed lumens and through the lumen of the catheter body. The puller wires each have a proximal end anchored to the control handle and a distal end anchored to the tip section. The first puller wire is longitudinally moveable relative to the catheter body to cause deflection of the tip section in a plane in a first direction, and the second puller wire is longitudinally moveable relative to the catheter body to cause deflection of the tip section in a plane in a second direction opposite the first direction. The catheter further comprises first and second orientation sheaths, or tubes, each having proximal and distal ends. Each orientation sheath extends through one of the lumens of the second pair of diametrically opposed lumens. The distal end of each orientation sheath is fixedly attached to the wall of the respective lumen at or near the distal end of the tip section, and the proximal end of each orientation sheath is fixedly attached to the wall of the respective lumen at a more proximal portion of the respective lumen. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0008]     These and other features of the advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:  
         [0009]      FIG. 1  is a side view of an embodiment of the catheter of the invention.  
         [0010]      FIG. 2  is a side cross-sectional view of the junction of the catheter body and tip section of an embodiment of a catheter according to the invention.  
         [0011]      FIG. 3  is a transverse cross-sectional view of the catheter body shown in  FIG. 2  taken along line  3 - 3 .  
         [0012]      FIG. 4  is a side cross-sectional view of the tip section of the catheter of the invention showing the lumens through which the orientation sheaths and electrode lead wires extend.  
         [0013]      FIG. 5  is a side cross-sectional view of the tip section of the catheter of the invention showing the lumens through which the pullers extend.  
         [0014]      FIG. 6  is an end cross-sectional view of the tip section rotated 90 degrees from the view shown in  FIG. 5 .  
         [0015]      FIG. 7  is an end cross-sectional view of the tip section of  FIGS. 4 and 6  taken along liens  7 - 7 . 
     
    
     DETAILED DESCRIPTION  
       [0016]     In a particularly preferred embodiment of the invention, there is provided a steerable bidirectional electrode catheter. As shown in  FIG. 1 , the catheter  10  comprises an elongated catheter body  12  having proximal and distal ends, a tip section  14  at the distal end of the catheter body  12 , and a control handle  16  at the proximal end of the catheter body  12 .  
         [0017]     As shown in  FIGS. 2 and 3 , the catheter body  12  comprises an elongated tubular construction having a single axial or central lumen  18 . The catheter body  12  is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body  12  can be of any suitable construction and made of any suitable material. A presently preferred construction comprises an outer wall  20  made of polyurethane or PEBAX. The outer wall  20  preferably comprises an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter body  12  so that when the control handle  16  is rotated the tip section  14  will rotate in a corresponding manner.  
         [0018]     The overall length and diameter of the catheter  10  may vary according to the application. A presently preferred catheter  10  has an overall length of about 48 inches. The outer diameter of the catheter body  12  is not critical, but is preferably no more than about 8 french. The inner surface of the outer wall  20  is preferably lined with a stiffening tube  22 , which can be made of any suitable material, preferably nylon or polyimide. The stiffening tube  22 , along with the braided outer wall  20 , provides improved flexural and torsional stability while at the same time minimizing the wall thickness of the catheter body  12 , thus maximizing the diameter of the central lumen  18 . The outer diameter of the stiffening tube  22  is about the same as or slightly smaller than the inner diameter of the outer wall  20 . A particularly preferred catheter  10  has an outer diameter of about 0.092 inch and a lumen  18  diameter of about 0.052 inch. If desired, the stiffening tube can be omitted.  
         [0019]     As shown in  FIGS. 4, 5  and  6 , the tip section  14  comprises a short section of flexible tubing  19  having four off-axis lumens  23 ,  24 ,  25  and  26  extending therethrough. The flexible tubing  19  can comprise a single unitary piece of plastic or can comprise a series of layers, as is generally known in the art. For example, the flexible tubing  19  can comprise a plastic core, an inner plastic layer surrounding the core, a braided stainless steel mesh surrounding the inner layer, and an outer plastic layer surrounding the braided mesh. The core is preferably made by extruding the plastic over four mandrels to thereby form the four off-axis lumens  23 ,  24 ,  25  and  26 , where the mandrels are removed after the core is extruded. The inner layer is formed over the core by any suitable technique, such as extrusion, which can be performed simultaneously with the extrusion of the core. Thereafter, the braided mesh is formed over the inner layer. The braided mesh comprises interwoven helical members, typically twelve, sixteen or twenty-four interwoven helical members, half extending in one direction and the other half extending in the in the counter direction. The tightness or braid angle of the helical members to a line parallel with the axis of the catheter and intersecting the helical members is not critical, but is preferably about 45. The helical members are preferably made of a conductive material having a high modulus of elasticity. Preferred helical members are made of stainless steel wire. Other methods for forming a braided mesh known in the art may be used. Finally the outer layer is formed over the braided mesh by any suitable technique, preferably extrusion.  
         [0020]     As would be recognized by one skilled in the art, the specific number and composition of the layers of the tip section  14  is not critical. For example, the inner layer can be omitted, particularly if it is desired to have a relatively small diameter tip section. The braided mesh can also be omitted, in which case the tip section  14  can optionally comprise a unitary core formed without additional plastic layers. Preferably whatever design is used, the tip section  14  is more flexible than the catheter body  12 . The outer diameter of the tip section  14 , like that of the catheter body  12 , is preferably no greater than about 8 french, more preferably about 6 French or less, but can vary depending on the particular application for which the catheter is to be used.  
         [0021]     In the depicted embodiment, the off-axis lumens  23 ,  24 ,  25  and  26  are arranged in diametrically opposed pairs. Each of the diametrically opposed lumens  23  and  24  of the first pair carry an orientation sheath  54 , discussed further below. The diametrically opposed lumens  25  and  26  of the second pair each carry a puller wire  32 , also discussed further below. For reasons that will become apparent, the first pair of lumens  23  and  24  is preferably generally perpendicular to the second pair of lumens  25  and  26 . The precise size of the lumens is not critical and will depend on the sizes of the components being carried by the lumens. As would be recognized by one skilled in the art, additional lumens could be provided if desired. For example, a central lumen could be provided for infusion of fluids.  
         [0022]     A preferred means for attaching the catheter body  12  to the tip section  14  is illustrated in  FIG. 2 . The proximal end of the tip section  14  comprises an outer circumferential notch  34  that receives the inner surface of the outer wall  20  of the catheter body  12 . The tip section  14  and catheter body  12  are attached by glue or the like. Before the tip section  14  and catheter body  12  are attached, however, the stiffening tube  22  is inserted into the catheter body  12 . The distal end of the stiffening tube  22  is fixedly attached near the distal end of the catheter body  12  by forming a glue joint with polyurethane glue or the like. Preferably a small distance, e.g., about 3 mm, is provided between the distal end of the catheter body  12  and the distal end of the stiffening tube  22  to permit room for the catheter body  12  to receive the notch  34  of the tip section  14 . A force is applied to the proximal end of the stiffening tube  22 , and, while the stiffening tube  22  is under compression, a first glue joint (not shown) is made between the stiffening tube  22  and the outer wall  20  by a fast drying glue, e.g. Super Glue®. Thereafter a second glue joint is formed between the proximal ends of the stiffening tube  22  and outer wall  20  using a slower drying but stronger glue, e.g., polyurethane. Other suitable techniques for attaching the catheter body  12  and tip section  14  can also be used in accordance with the present invention.  
         [0023]      FIG. 4  provides a schematic side cross-sectional view of the tip section  14 . As shown in  FIG. 4 , the distal end of the tip section  14  carries a tip electrode  38 . Mounted along the length of the tip section  14  are three ring electrodes  40 . The length of each ring electrode  40  is not critical, but preferably ranges from about 1 mm to about 3 mm. The distance between the ring electrodes  40  is not critical so long as their edges do not touch. More or less ring electrodes  40  can be provided if desired.  
         [0024]     The tip electrode  38  and ring electrode  40  are each connected to a separate electrode lead wire  30 . Each lead wire  30  extends through a lumen  23  in the tip section  14 , through the central lumen  18  in the catheter body  12  and through the control handle  16 . The proximal end of each lead wire  30  extends out the proximal end of the control handle  16  and is connected to an appropriate connector, which can be plugged into or otherwise connected to a suitable monitor, source of energy, etc.  
         [0025]     The lead wires  30  are connected to the tip electrode  38  and ring electrode  40  by any conventional technique. Connection of a lead wire  30  to the tip electrode  38  is preferably accomplished by solder or the like, as shown in  FIG. 4 . Connection of a lead wire  30  to a ring electrode  40  is preferably accomplished by first making a small hole through the wall of the tip section  14  into the lumen  23  through which the lead wire extends, as also shown in  FIG. 4 . Such a hole can be created, for example, by inserting a needle through the wall of the tip section  14  and heating the needle sufficiently to form a permanent hole. A lead wire  30  is then drawn through the hole by using a microhook or the like. The end of the lead wire  30  is then stripped of any coating and welded to the underside of the ring electrode  40 , which is then slid into position over the hole and fixed in place with polyurethane glue or the like.  
         [0026]     Two puller wires  32  extend through the catheter  10 . Each puller wire  32  extends from the control handle  16 , through the central lumen  18  in the catheter body  12  and into one of the off-axis lumens  25  and  26  of the tip section  14 , as shown in  FIG. 5 . As described in more detail below, the proximal end of each puller wire  32  is anchored within the control handle  16 , and the distal end of each puller wire  32  is anchored within the tip section  14 .  
         [0027]     Each puller wire  32  is made of any suitable metal, such as stainless steel or Nitinol. Preferably each puller wire  32  has a coating, such as a coating of Teflon® or the like. Each puller wire  32  has a diameter preferably ranging from about 0.006 inch to about 0.0010 inch. Preferably both of the puller wires  32  have the same diameter.  
         [0028]     Each puller wire  32  is anchored near the distal end of the tip section  14 . In the embodiment depicted in  FIG. 5 , the puller wires  32  are both anchored in blind holes  37  in the tip electrode  38  by a welding or the like. Alternatively, one or both puller wires  32  can be anchored to the side wall of the tip section  14 , as described in U.S. patent application Ser. No. 09/710,210, filed Nov. 10, 2000, the disclosure of which is incorporated herein by reference. Other means for anchoring the puller wires  32  in the tip section  14  would be recognized by those skilled in the art and are included within the scope of the invention.  
         [0029]     In the depicted embodiment, the distal ends of the puller wires  32  are attached to opposite sides of the tip section  14 . This design permits deflection of the tip section  14  in opposing directions.  
         [0030]     The catheter  10  further comprises two compression coils  46 , each in surrounding relation to a corresponding puller wire  32 , as shown in  FIGS. 2 and 3 . Each compression coil  46  is made of any suitable metal, such as stainless steel. Each compression coil  46  is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of each compression coil  46  is slightly larger than the diameter of its associated puller wire  32 . For example, when a puller wire  32  has a diameter of about 0.007 inch, the corresponding compression coil  46  preferably has an inner diameter of about 0.008 inch. The coating on the puller wires  32  allows them to slide freely within the compression coil  46 . The outer surface of each compression coil  46  is covered along most of its length by a flexible, non-conductive sheath  48  to prevent contact between the compression coil  46  and the lead wires  30  within the central lumen  18 . A non-conductive sheath  48  made of thin-walled polyimide tubing is presently preferred.  
         [0031]     At the distal end of the catheter body, the two compression coils  46  are positioned in diametric opposition within the stiffening tube  22  so that they can be aligned with the two off-axis lumens  25  and  26  in the tip section  14  through which the puller wires  32  extend. The compression coils  46  and stiffening tube  22  are sized so that the compression coils  46  fit closely and slidably within the stiffening tube  22 . With this design, the lead wires  30  distribute themselves around the two compression coils  46  without misalligning the coils.  
         [0032]     The compression coils  46  are secured within the catheter body  12  with polyurethane glue or the like. Each compression coil  46  is anchored at its proximal end to the proximal end of the stiffening tube  22  in the catheter body  12  by a glue joint (not shown). When a stiffening tube  22  is not used, each compression coil is anchored directly to the outer wall  20  of the catheter body  12 .  
         [0033]     The distal end of each compression coil  46  is anchored to the distal end of the stiffening tube  22  in the catheter body  12  by a glue joint  52 , or directly to the distal end of the outer wall  20  of the catheter body  12  when no stiffening tube  22  is used. Alternatively, the distal ends of the compression coils  46  may extend into the off-axis lumens  26  and  28  of the tip section  14  and are anchored at their distal ends to the proximal end of the tip section  14  by a glue joint. In the depicted embodiment, where the compression coils  46  are each surrounded by a sheath  48 , care should be taken to insure that the sheath is reliably glued to the compression coil. The lead wires  30  can also be anchored in the glue joint. However, if desired, tunnels in the form of plastic tubing or the like can be provided around the lead wires at the glue joint to permit the lead wires to be slidable within the glue joint.  
         [0034]     The glue joints preferably comprise polyurethane glue or the like. The glue may be applied by means of a syringe or the like through a hole made between the outer surface of the catheter body  20  and the central lumen  18 . Such a hole may be formed, for example, by a needle or the like that punctures the outer wall  20  and the stiffening tube  22  that is heated sufficiently to form a permanent hole. The glue is then introduced through the hole to the outer surface of the compression coil  46  and wicks around the outer circumference to form a glue joint about the entire circumference of each sheath  48  surrounding each compression coil  46 . Care must be taken to insure that glue does not wick over the end of the coil so that the puller wire cannot slide within the coil.  
         [0035]     Within the off-axis lumens  25  and  26 , each puller wire  32  is surrounded by a plastic sheath  42 , preferably made of Teflon®. The plastic sheathes  42  prevent the puller wires  32  from cutting into the wall of the tip section  14  when the tip section is deflected. Each sheath  42  ends near the distal end of each puller wire  32 . Alternatively, each puller wire  32  can be surrounded by a compression coil where the turns are expanded longitudinally, relative to the compression coils extending through the catheter body, such that the surrounding compression coil is both bendable and compressible.  
         [0036]     Longitudinal movement of a puller wire  32  relative to the catheter body  12 , which results in deflection of the tip section  14  in the direction of the side of the tip section to which that puller wire is anchored, is accomplished by suitable manipulation of the control handle  16 . A suitable bidirectional control handle for use in the present invention is described in copending application Ser. No. 09/822,087, filed Mar. 30, 2001 and entitled “Steerable Catheter with a Control Handle Having a Pulley Mechanism”, the disclosure of which is incorporated herein by reference. Other suitable bidirectional control handles are described in U.S. Pat. Nos. 6,123,699, 6,171,277, 6,183,463, and 6,198,974, the disclosures of which are incorporated herein by reference.  
         [0037]     As illustrated in  FIGS. 6 and 7 , the tip section  14  includes a mechanism for enhancing control over the deflection of the tip section. The mechanism comprises two orientation sheaths  54  that extend through the two lumens  23  and  24  of the first diametrically opposed pair in the tip section  14 . Each orientation sheath  54  comprises an elongated, very flexible, thin walled polymer sheath, or tube. In a preferred embodiment, the two orientation sheaths  54  are formed of thin-walled polyimide tubes which are on the order of 0.001 inches and which are inserted into the lumens and are then fed onto stainless steel mandrels. A Teflon heat shrink sleeve is then placed around the entire catheter body and heat is applied to soften the orientation sheaths and the body of the catheter while the Teflon heat shrink sleeve squeezes the materials together to bond the sheaths into the walls of the lumens.  
         [0038]     The precise anchor point of the proximal end of each orientation sheath  54  is not critical. Preferably the proximal ends of the sheaths  54  are anchored at approximately the same longitudinal position within the catheter.  
         [0039]     As noted above, the first pair of diametrically opposed lumens  23  and  24  extend in a plane which is generally perpendicular to the plane of the second pair of diametrically opposed lumens  25  and  26 . Accordingly, the orientation sheaths  54  are provided in the plane of deflection of the tip section  14 . This arrangement improves the in-plane deflection of the tip section  14  because the orientation sheaths  54  reduce the tendency of the tip section to bend in a direction other than across the plane along which the sheaths are positioned, i.e., the plane of deflection of the tip section. Such in-plane deflection increases the lateral tip stability which results in the user being able to create a greater contact force against the heart tissue.  
         [0040]     The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.