Abstract:
A catheter adapted for deflection in a narrow tubular region and/or sharp turn, has an elongated body, a deflection section having a support member adapted for heat activation to assume a trained configuration, and a lead wire configured to deliver a current to the support member for heat activation. The support member is constructed of a shaped memory alloy, for example, nitinol, and the lead wire is adapted to directly heat the support member. Moreover, the catheter may include a thermally insulating layer covering at least a portion of the support member. The trained configuration of the support member extends in a single dimension, in two dimensions or in three dimensions.

Description:
FIELD OF INVENTION 
       [0001]    This invention relates to medical catheterization. More particularly, this invention relates to steerable and deflectable EP catheters. 
       BACKGROUND 
       [0002]    Medical catheterizations are routinely carried out today. For example, in cases of cardiac arrhythmias, such as atrial fibrillation, which occur when regions of cardiac tissue abnormally conduct electric signals. Procedures for treating arrhythmia include surgically disrupting the origin of the signals causing the arrhythmia, as well as disrupting the conducting pathway for such signals. By selectively ablating cardiac tissue by application of energy, e.g., radiofrequency energy via a catheter, it is sometimes possible to cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. 
         [0003]    A typical cardiac catheter is inserted through a patient&#39;s vascular system into a chamber or vascular structure of the heart. The catheter&#39;s distal tip is brought into contact with the heart wall for obtaining electrical and positional information that is processed by a console that includes a processor for generating activation maps, anatomical positional information and other functional images. 
         [0004]    More recently, catheter-based ablation has been used in renal denervation. One in four adults suffers from hypertension worldwide. Overactive sympathetic nervous system plays a vital role in pathogenesis of hypertension. Renal denervation has demonstrated exceptional blood pressure reductions in patients with resistant hypertension. In renal catheterization, a very thin catheter is inserted in the groin, passed through the body and into the renal arteries. At the desired location RF or ultrasound energy is activated to deaden the nerves associated with the renal arteries in a way that will effectively switch off one of the mechanisms that cause high blood pressure. These so-called “sympathetic” nerves can be a main cause of hypertension when they become overactive, and by reducing their activity the body responds by lowering heart rate and other factors. 
         [0005]    Nitinol wire is often used in the construction of therapeutic and diagnostic catheter distal ends, including geometric distal ends such as a ring, a helix or a basket for use in a chamber or tubular region of the heart where contact with sides of the region is desired. At body temperature, nitinol wire is flexible and elastic and like most metals nitinol wires deform when subjected to minimal force and return to their shape in the absence of that force. Accordingly, a 3-D distal assembly can be easily collapsed to be fed into a guiding sheath, and readily deployed in the chamber or tubular region upon removal of the guiding sheath. Because Nitinol belongs to a class of materials called Shaped Memory Alloys (SMA). These materials have interesting mechanical properties beyond flexibility and elasticity, including shape memory and superelasticity which allow nitinol to have a “memorized shape.” That is, nitinol can be trained to remember a particular shape by annealing. 
         [0006]    Nitinol has three distinct temperature phases: martensitic phase, austenite phase and annealing phase. The martensitic phase is a low temperature phase where the crystal structure of nitinol is aligned and cubic. The alloy may be bent or formed easily. Bending deforms the crystalline structure of the alloy producing internal stress. In the austenite phase, the nitinol is heated above its transitional temperature where the crystalline structure returns to its non-stress (cubic) state. The transitional temperature of nitinol is highly dependent on the exact nickel and titanium ratio. The transitional temperature of nitinol can be adjusted between about −100 C to +100 C depending on the alloy composition and/or it processing. Annealing phase is a high temperature phase where the crystalline structure of nitinol can be reoriented to “remember” the shape imposed upon it while it is subjected to the high temperature. The annealing phase for nitinol wire is about 540 degrees Celsius. 
         [0007]    Once the memory is established in high temperature annealing, a cooled nitinol wire can be bent out of the memorized shape, whereupon subsequent heating of the nitinol wire above its transition temperature will return it to its memorized shape. Nitinol is activated for such thermal movement at its transition temperature which is typically about 70 degrees Celsius. An electric current may be passed through a Nitinol wire to heat it electrically as the wire&#39;s resistance is about 2.5 ohm/m. 
         [0008]    The human heart has four chambers and tubular regions feeding into and out of those chambers. A cardiac EP catheter is typically inserted into the vasculature through an incision in a femoral vein of the patient and advanced through the superior vena cava which feeds into the right atrium of the heart. The distal end of the cardiac catheter may then remain in the right atrium, or be further advanced into another chamber and/or a tubular region. The cardiac EP catheter is steered and deflected into each these regions by means of one or more puller wires responsive to a catheter control handle. Cardiac catheters offer a variety of deflection curvatures, as shown in  FIG. 11 , where each curvature typically has a uniform curvature (forming the arc of a circle of a different radius). Similarly, the renal arteries are accessed through an incision in a femoral artery and a renal catheter is advanced through the aorta to reach the renal arteries. However, unlike the right atrium which is a cavernous region accessed from the relatively wide superior vena cava, the left and right renal arteries are narrower than the aorta and nearly perpendicular to it, making the approach more challenging for a renal catheter. 
         [0009]    Accordingly there is a desire for a catheter to be more easily maneuverable in tight spaces and tubular regions, including an EP catheter that can be steerable through a narrow tubular region with a sharp turn. There is also a desire for an EP catheter that can be advanced atraumatically through a patient&#39;s vasculature, predictably adopt a preformed shape or configuration upon actuation, and return to an atraumatic configuration for relocation or withdrawal from the patient&#39;s body. There is a further desire that such preformed shape or configuration be more acute and/or sharper than configurations previously achieved through one or more puller wires. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention is directed to a catheter having an elongated body, a deflection section having a support member adapted for heat activation to assume a trained configuration, and a lead wire configured to deliver a current to the support member for heat activation. 
         [0011]    In some embodiments, the support member is constructed of a shaped memory alloy, for example, nitinol, and the lead wire is adapted to directly heat the support member. Moreover, the catheter may include a thermally insulating layer covering at least a portion of the support member. 
         [0012]    In some embodiments, the trained configuration of the support member extends in a single dimension, in two dimensions or in three dimensions. 
         [0013]    In some embodiments, the catheter includes a second support member adapted for heat activation to assume a second trained configuration, wherein the second support member has at least a portion that is distal of the first support member and/or wherein the second support member has a least a portion that is coextensive with the first support member along the longitudinal axis. A second lead wire is provided configured to deliver a current to the second support member. 
         [0014]    The present invention also includes a method of using the above catheter, comprising advancing the elongated body and deflection section of the catheter into a patient&#39;s vasculature and activating the lead wire to heat the support member to at least its transitional temperature. The method may include allowing the support member to cool to below its transitional temperature before relocating the catheter or removing the catheter from the patient&#39;s vasculature. Allowing the support member to cool may include deactivating the lead wire from delivering the current to the support member. 
         [0015]    The present invention further includes a method of manufacturing the above catheter, comprising heating the support member to its annealing phase and forming the support member while in its annealing phase into a first configuration, and cooling the support member to below its transitional temperature and forming the support member into a second configuration. In some embodiments, the heating and cooling are prior to assembling the catheter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. It is understood that selected structures and features have not been shown in certain drawings so as to provide better viewing of the remaining structures and features. 
           [0017]    FIG. I is a top plan view of a catheter of the present invention, in accordance with an embodiment. 
           [0018]      FIG. 2A  is a side cross-sectional view of the catheter of  FIG. 1 , including a junction of a catheter body and an intermediate deflection section, taken along a first diameter. 
           [0019]      FIG. 2B  is a side cross-sectional view of the catheter of  FIG. 1 , including a junction of a catheter body and an intermediate deflection section, taken along a second diameter generally perpendicular to the first diameter. 
           [0020]      FIG. 2C  is an end cross-sectional view of the intermediate deflection section of  FIGS. 2A and 2B , taken along line C-C. 
           [0021]      FIG. 3A  is a side cross-section view of the catheter of  FIG. 1 , including a junction of an intermediate deflection section and a distal section, taken along the first diameter. 
           [0022]      FIG. 3B  is a side cross-sectional view of the catheter of  FIG. 1 , including a junction of an intermediate section and a distal section, taken along the second diameter generally perpendicular to the first diameter. 
           [0023]      FIG. 4A  is a side cross-sectional view of the distal section of the catheter of  FIG. 1 , taken along the first diameter. 
           [0024]      FIG. 4B  is a side cross-sectional view of the distal section of the catheter of  FIG. 1 , taken along the second diameter generally perpendicular to the first diameter. 
           [0025]      FIG. 4C  is an end cross-sectional view of the distal section of  FIGS. 4A and 4B , taken along line C-C. 
           [0026]      FIG. 5  is a perspective view of a catheter portion in a first configuration (in solid lines) and a second configuration (in broken lines), in accordance with an embodiment of the present invention. 
           [0027]      FIG. 6  is a schematic illustration of a catheter of the present invention in use in a renal region, in accordance with an embodiment. 
           [0028]      FIG. 7  is an end cross-sectional view of an intermediate deflection section, in accordance with an embodiment of the present invention. 
           [0029]      FIG. 8A  is a side view of a portion of a catheter deflected in one configuration, in accordance with an embodiment of the present invention. 
           [0030]      FIG. 8B  is a side view of the catheter portion of  FIG. 8A  deflected in another configuration. 
           [0031]      FIG. 8C  is an end cross-sectional view of the catheter portion of  FIGS. 8A and 8B , taken along line C-C. 
           [0032]      FIG. 9A  is a side view of a portion of a catheter deflected in one configuration, in accordance with an embodiment of the present invention. 
           [0033]      FIG. 9B  is a side view of the catheter portion of  FIG. 9A  deflected in another configuration. 
           [0034]      FIG. 9C  is an end cross-sectional view of the catheter portion of  FIGS. 9A and 9B , taken along line C-C. 
           [0035]      FIG. 10A  is a side view of a catheter with parts broken away to reveal serially-connected support members, in accordance with an embodiment of the present invention. 
           [0036]      FIG. 10B  is a side view of the catheter of  FIG. 10A , with the support members in their trained configurations. 
           [0037]      FIG. 11  is a perspective view of catheters in various deflections, as known in the art. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    Referring to  FIG. 1 , a catheter  10  according to the disclosed embodiments comprises an elongated body that may include an insertion shaft or catheter body  12  having a longitudinal axis, and an intermediate deflection section  14  distal of the catheter body that can be deflected off axis from the catheter body longitudinal axis. A distal section  15  extending distally from the intermediate section  14  includes a distal tip electrode  17  and one or more ring electrodes  19 . A control handle  11  extends from a proximal end of the catheter body  12 . In accordance with a feature of the present invention, the deflection section  14  is constructed with a support member having a temperature-sensitive trained shape which can be heat activated to change from one configuration into another configuration, and be returned to the prior configuration or shaped into another configuration when cooled. 
         [0039]    In the depicted embodiment of  FIGS. 2A and 2B , 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  comprises an imbedded braided mesh of stainless steel or the like, as is generally known in the art, to increase torsional stiffness of the catheter body  12  so that, when the control handle  16  is rotated, the intermediate section  14  will rotate in a corresponding manner. 
         [0040]    The outer diameter of the catheter body  12  is not critical, but is preferably no more than about 8 french, more preferably 7 french. Likewise the thickness of the outer wall  20  is not critical, but is thin enough so that the central lumen  18  can accommodate any desired wires, cables and/or tubes. The inner surface of the outer wall  20  is lined with a stiffening tube  21  to provide improved torsional stability. The outer diameter of the stiffening tube  21  is about the same as or slightly smaller than the inner diameter of the outer wall  20 . The stiffening tube  21  can be made of any suitable material, such as polyimide, which provides very good stiffness and does not soften at body temperature. 
         [0041]    With reference to  FIGS. 2A, 2B and 2C , the deflectable intermediate section  14  comprises a short section of tubing  22  having multiple lumens, each occupied by the various components extending through the intermediate section  14  from the catheter body  12 . In the illustrated embodiment, there are at least four off-axis lumens. Electrode lead  24  wires pass through a first lumen  31 . An elongated support member  25  with shape memory passes through a second lumen  32 . An irrigation tubing  26  for delivering irrigation fluid to the distal tip electrode  17  passes through a third lumen  34 . A cable  28  connected to a distal location sensor  29  (see  FIGS. 3A and 3B ) passes through the first lumen  31 . A puller wire  30  may pass through a fourth lumen  34  to provide the deflection section  14 . 
         [0042]    The multi-lumened tubing  22  of the intermediate section  14  is made of a suitable non-toxic material that is preferably more flexible than the catheter body  12 . A suitable material is braided polyurethane or PEBAX, i.e., polyurethane or PEBAX with an embedded mesh of braided stainless steel or the like. The plurality and size of each lumen are not critical, provided there is sufficient room to house the components extending therethrough. Position of each lumen is also not critical, except the position of the second and fourth lumens  32  and  34  being off-axis, as it is understood that deflections produced by the support member  25  and the puller wire  30  are toward the respective side of the tubing  22  along which each of these respective components extends. Thus, in some embodiments, the catheter is afforded opposite, bi-directional deflection where the support member  25  and the puller wire  30  are situated in diametrically-opposite lumens  32  and  34 . 
         [0043]    The useful length of the catheter, i.e., that portion that can be inserted into the patient&#39;s body can vary as desired. Preferably the useful length ranges from about 60 cm to about 95 cm. The length of the intermediate section  14  is a relatively small portion of the useful length, and preferably ranges from about 2 cm to about 10 cm, more preferably from about 5 cm to about 7 cm. 
         [0044]    A means for attaching the catheter body  12  to the intermediate section  14  is illustrated in  FIGS. 2A and 2B . The proximal end of the intermediate section  14  comprises an outer circumferential notch  35  that receives the inner surface of the outer wall  20  of the catheter body  12 . The intermediate section  14  and catheter body  12  are attached by glue or the like, for example, polyurethane. If desired, a spacer (not shown) can be provided within the catheter body  12  between the distal end of the stiffening tube  21  and the proximal end of the intermediate section  14  to provide a transition in flexibility at the junction of the catheter body  12  and the intermediate section, which allows the junction to bend smoothly without folding or kinking. An example of such a spacer is described in more detail in U.S. Pat. No. 5,964,757, the disclosure of which is incorporated herein by reference. 
         [0045]    Distal the intermediate section  14  is the distal section  15 . As shown in  FIGS. 3A and 3B , the distal section  15  includes a short section of tubing  13 , having a central lumen  16 , extending between a distal end of the tubing  22  and the distal tip electrode  17 . The tubing  13  houses the EM location sensor  29 . Extending through the central lumen  16  are lead wire  24 T for the distal tip electrode  17 , lead wires  24 R for the ring electrodes  19 , and the irrigation tubing  26 . 
         [0046]    A means for attaching the tubing  13  to the tubing  22  of the intermediate section  14  is illustrated in  FIGS. 3A and 3B . The distal end of the intermediate section  14  comprises an outer circumferential notch  37  that receives an inner circumferential notch of the proximal end of the tubing  13 . The tubing  22  and the tubing  13  are attached by glue or the like, for example, polyurethane. 
         [0047]    With reference to  FIGS. 4A, 4B and 4C , the distal tip electrode  17  has a generally solid cylindrical body with a proximal stem  17 P and an atraumatic distal end  17 D. The proximal stem  17 P is received in a distal end of the tubing  13 . A proximal face of the body has a blind hole  40  that receives a distal end of the lead wire  24 T anchored in the blind hole  40  by a crimped ferrule  41 . In some embodiments, the proximal face also has a longitudinal fluid passage  42  that receives a distal end of the irrigation tubing  26  through which fluid can flow from a fluid source (not shown), along the length of the catheter into the tip electrode  17  and exit the tip electrode  17  via fluid ports  46  and transverse fluid branches  44  that communicate with the longitudinal fluid passage  42 . 
         [0048]    In some embodiments, ring electrodes  19  are affixed to the outer surface of the connector tubing  13  as shown in  FIGS. 4A and 4B . As understood by one of ordinary skill in the art, lead wires  24 R are connected to the ring electrodes  19  via holes  50  ( FIG. 4A ) formed in the side wall of the tubing  13 . 
         [0049]    In the depicted embodiment, the support member  25  extends through the second lumen  32  of the tubing  22  to define one or more shapes of the intermediate deflection section  14 . The support member  25  is made of a material that is flexible and elastic, i.e., that can be straightened or bent out of its original shape upon exertion of a force and is capable of substantially returning to its original shape upon removal of the force. In accordance with a feature of the present invention, a suitable material for construction of the support member  25  also has temperature sensitivity in that the shapes or configurations the support member can assume depend on temperature of the support member. Accordingly, a suitable material for the support member  25  are Shaped Memory Alloys (SMA). These materials have interesting mechanical properties including shape memory and superelasticity which allow the support member  25  to have a “memorized shape.” That is, the support member  25  has been trained to remember a particular shape by an annealing process. 
         [0050]    In accordance with a feature of the present invention, the support member  25  has been arranged in a first configuration, for example, as shown in solid lines  FIG. 5 , and trained to remember the first configuration by high-temperature heating in the annealing phase. When the support member  25  is thereafter cooled to room temperature (about 70 F or 21 C), the support member is in the martensitic phase whereupon it is shaped into a second configuration, for example, as shown in broken lines in  FIG. 5 . When the support member  25  is subsequently heated to its transitional temperature (for example between about 158 F to 266 F or 70 C to 130 C), the support member  25  is in the austenite phase whereupon it generally returns to the first configuration trained in the annealing phase, for example, as shown in solid lines in  FIG. 5 . When the heating is terminated, the support member  25  can cool to below its transitional temperature where it can be reshaped. 
         [0051]    In some embodiments, the first “trained” configuration includes at least a bend X that is sharp or acute or at least a bend that has multiple different curvatures A, B, and C (each tracing an arc of a circle with a different radius RA, RB and RC), such that the overall curvature is not uniform along its length. The second configuration (in broken lines in  FIG. 5 ) may be a straight or more linear configuration, or a generally linear configuration with a light curvature. Trained configurations may also include 2-D configurations such as zig-zags or “S” and 3-D configurations such as spirals and helices. 
         [0052]    A suitable material includes nickel/titanium alloys. Such alloys typically comprise about 55% nickel and 45% titanium, but may comprise from about 54% to about 57% nickel with the balance being titanium. A suitable nickel/titanium alloy is Nitinol, which has excellent shape memory, together with ductility, strength, corrosion resistance, electrical resistivity and temperature stability. 
         [0053]    The support member  50  has a cross-section of a predetermined shape that may be generally circular or generally rectangular, including a square shape. It is understood that a generally rectangular cross section can provide greater stiffness compared to a circular cross-section of a comparable size. 
         [0054]    To heat the support member  25  into annealing phase, a lead wire  52 , e.g., copper wire, is electrically connected to the support member  25 , for example, wrapped around a proximal portion of the support member  25 , as shown in  FIG. 2B . The lead wire  52  extends proximally from the support member  25  through the central lumen  18  of the catheter body  12 , and into the control handle  11  where it is connected to an electrical pin connector at the proximal end of the control handle, through which a current can be delivered from a remote power supply (not shown) to heat the support member  25  by resistive heating. To complete the circuit, a return lead wire  52 R is electrically connected to the support member  25 , for example, wrapped around a distal portion of the support member  25 , as shown in  FIG. 3B , and extends proximally through the lumen  32  of the tubing  22  and the lumen  18  of the catheter body  12 , and into the control handle  11  where it is connected to the electrical pin connector. The support member  25  can be surrounded and covered by a thermally-insulating shrink sleeve  54  that extends along the length of the support member  25  to protect the catheter and the patient from excessive heat. 
         [0055]      FIG. 6  illustrates a catheter  10  of the present invention in use in a renal artery  100  accessed via the aorta  102 . In accordance with a feature of the present invention, the catheter has a shape memory support member  25  that assumes a first or “trained” configuration (in solid lines) when it is above its transitional temperature, and can be flexible and shaped into a second configuration (in broken lines) when it is below its transitional temperature. 
         [0056]    At room temperature with the support member  25  having been flexibly shaped into the second configuration (in broken lines), the catheter  10  is advanced atraumatically by an EP professional in a patient through an incision in a femoral artery (not shown). The catheter  10  is fed through a guiding sheath  106  whose distal end is positioned in the lower aorta  102  near the renal artery  100 . When the distal section  15  and the intermediate section  14  are near the renal artery  100 , the guiding sheath  106  is withdrawn to expose the distal section  15  and the intermediate section  14 , with the support member in its second configuration (in broken lines). 
         [0057]    To enter the renal artery  100 , the EP professional actuates a power supply (not shown) to deliver a current via the lead wire  52  to heat the support  25  to above its transitional temperature. Heated to above its transitional temperature, the support member  25  assumes its first or “trained” configuration (in solid lines) and sharply deflects the intermediate section  14  enabling the distal tip section  15  to readily enter the narrow renal artery  102  so that the distal tip electrode  17  can contact a renal nerve  104 . The sharp deflection of the intermediate section  14  provided by the support member  25  may be tempered or accentuated by the puller wire  30  as controlled by the EP professional via the deflection knob  58  ( FIG. 1 ) on the control handle  11 . 
         [0058]    When the EP professional is ready to relocate or remove the catheter from the renal region, the current to the lead wire  52  is discontinued and the support member  25  is cooled by surrounding blood flow to below its transitional temperature, whereupon the support member  25  is again flexible and (re)shapeable into the second configuration or another configuration and thus can be readily relocated or drawn proximally through the guiding sheath  106  to exit the patient&#39;s vasculature. 
         [0059]    It is understood that the support member  25  may be imparted with an endless variety of first and second configurations depending on the desire and need. Each of the first and second (or trained and subsequent) configurations may be a 1-D, 2-D or 3-D configuration. It is also understood that the first and second configurations may be tempered, accentuated, adjusted, varied, or even opposed or restricted, as needed or desired by the puller wire  30  extending through the fourth lumen  34 . The puller wire is actuated by the deflection knob  58  on the control handle  11  and has a distal end anchored at a predetermined location in the sidewall of the tubing  22  of the intermediate section  14 , for example, by a T-bar  56 , as shown in  FIG. 3B . Depending on the desired interaction between the puller wire  30  and the support member  25 , the location of the distal end can be varied relative to the position of the support member  25 . In some embodiments, the location may be proximal of the distal end of the support member  25 , distal of the distal end of the support member  25 , or along the length of the support member  25 . 
         [0060]    In alternate embodiments, the support member  25  and the puller wire  30  may both pass through a common lumen in the tubing  22  of the intermediate section  14 , as shown in  FIG. 7 , especially where the interaction of these components is intended to be complementary rather than in opposition. 
         [0061]    The portion of the puller wire  30  throughout the catheter body  12  is surrounded by a compression coil  43  which has a distal end near the junction of the catheter body  12  and the intermediate deflection section  14 , as shown in  FIG. 2B . The compression coil  43  is made of any suitable metal, preferably stainless steel, and is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the compression coil is preferably slightly larger than the diameter of the puller wire  30 . The outer surface of the compression coil is covered by a flexible, non-conductive sheath  45 , e.g., made of polyimide tubing. The compression coil may be formed of a wire having a square or rectangular cross-sectional area, which may make it less compressible than a compression coil formed from a wire having a circular cross-sectional area. As a result, the compression coil  43  keeps the catheter body  12  from deflecting when the puller wire  30  is drawn proximally as it absorbs more of the compression. The portion of the puller wire  30  extending through the intermediate section  14  is surrounded by a plastic, e.g., Teflon®, puller wire sheath, which prevents the puller wire  30  from cutting into the wall of the tubing  22  of the intermediate section  14  when the intermediate section  14  is deflected. 
         [0062]    The present invention also is directed to a catheter with one or more heat-responsive support members, each of which may occupy respective lumens or they may share a common lumen in the tubing  22  of the intermediate section  14 , and/or be jointly energized by a common lead wire or separately energized by respective lead wires, to provide different movements and configurations along same or different portions of the catheter. 
         [0063]    In  FIG. 8C , a catheter includes support members  25 A and  25 B sharing a common lumen  32  but each having a respective lead wire  52 A and  52 B and a respective return wire  52 AR and  52 BR. Support member  25 A is trained with one configuration and support member  25 B is trained with another configuration. Accordingly, an EP professional can select which configuration for the catheter to assume depending on which support member he activates by heating.  FIG. 8A  illustrates the catheter when a current is delivered by the lead wire  52 A to heat-activate support member  25 A into its trained configuration.  FIG. 8B  illustrates the catheter when a current is delivered by the lead wire  52 B to heat-activate support member  25 B into its trained configuration. Both support members  25 A and  25 B have a trained configuration with deflection in generally the same direction. 
         [0064]    In  FIG. 9C , a catheter includes support members  25 C and  25 D, each occupying a different lumen and each having a different lead wire  52 C and  52 D and a different return wire  52 CR and  52 DR.  FIG. 9A  illustrates the catheter when a current is delivered by lead wire  25 C to heat-activate support member  25 C into its trained configuration.  FIG. 9B  illustrates the catheter when a current is delivered the lead wire  25 D to heat-activate support member  25 D into its trained configuration. In this illustrated embodiment, the support members  25 C and  25 D may have trained configurations in generally opposing directions. 
         [0065]      FIG. 10A  illustrated a catheter with serially-arranged support members  25 M and  25 N, each configured for receiving a current by a dedicated lead wire  52 M and  52 N and a dedicated return wire  52 MR and  52 NR. A thermally insulating connector  38  extends between and connects the two members.  FIG. 10B  illustrates the catheter when a current is delivered by lead wire  25 M to heat activate support member  25 M into is trained configuration, without current being delivered by lead wire  25 N which leaves support member  25 N unaffected (shown in broken lines). When a current is subsequently delivered to support member  25 N, it assumes its trained configuration (shown in solid lines). It is understood that the support members  25 M and  25 N may be heat activated jointly, or in any time sequence to achieve the desired movement or configuration. 
         [0066]    Irrigation fluid is delivered to the distal assembly  17  by the irrigation tubing  43  whose proximal end is attached to a luer hub (not shown) proximal of the control handle  16  and receives fluid delivered by a pump (not shown). The irrigation tubing extends through the control handle  16 , the central lumen  18  of the catheter body  12 , the third lumen  33  of the intermediate section  14 , the central lumen of the tubing  13  and into the fluid passage  42  of the tip electrode  17 . 
         [0067]    The proximal end of each electrode lead wires  24 T and  24 R is electrically connected to a suitable connector (not shown) distal of the control handle  11  for transmitting electrical signals from tissue and/or delivery electrical energy to accomplish ablation. The lead wires extend into the control handle  11  and are connected to an electrical connector at a proximal end of the control handle  11 . 
         [0068]    The catheter of the present invention may be used in any region of anatomy, including the heart and the renal region. Deployed in or near the patient&#39;s heart, the catheter is designed to facilitate electrophysiological mapping of a chamber or tubular region of the heart and to transmit energy, e.g., radiofrequency (RF) current, to the catheter electrodes for ablation purposes. For ablation, the catheter is used in conjunction with a multi-channel RF generator and irrigation pump. Deployed in the renal region, the catheter is designed to enter a renal artery to ablate renal nerves. 
         [0069]    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. Any feature or structure disclosed in some embodiments may be incorporated in lieu of or in addition to other features of any other embodiments, as needed or appropriate. As understood by one of ordinary skill in the art, the drawings are not necessarily to scale. 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.