Patent Publication Number: US-8977344-B2

Title: Injection catheter with needle electrode

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a continuation of U.S. patent application Ser. No. 09/711,648, filed Nov. 13, 2000 (now U.S. Pat. No. 8,079,982) which is a continuation-in-part of U.S. patent application Ser. No. 09/280,202, filed Mar. 29, 1999, (now U.S. Pat. No. 6,165,164) which claims the benefit of U.S. Provisional Patent Application Nos. 60/088,019, filed on Jun. 4, 1998, and 60/088,984, filed on Jun. 11, 1998, the entire disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a catheter for infusing therapeutic or diagnostic agents into the tissue of organs having an injection needle that also serves as an electrode for mapping and/or ablation. 
     BACKGROUND OF THE INVENTION 
     Targeted delivery of therapeutic or diagnostic agents, such as occurs in gene therapy, is very desirable but often presents a difficult challenge. A potential benefit of targeted delivery is that there is an increased efficiency obtained by the precise placement of the therapeutic or diagnostic agent. There are several problems to his procedure which must be overcome in order to obtain satisfactory results from such therapy, such as the problems of obtaining access to the delivery site, transporting the therapeutic or diagnostic agent to the desired site, injecting the agent at the proper depth within the organ tissue, steering the distal end of the catheter to a desired location within the organ prior to infusing the agent, and positioning the distal tip of the catheter at precisely the same location where prior measurements have indicated that the drug should be infused. It is also important to for a physician to be able to monitor the position of the infusion needle with respect to the wall of the organ. In the case of an organ, such as the heart, in which the walls are in constant motion, the activity of positioning and monitoring the position of the distal tip of the catheter, or infusion needle, becomes especially difficult. 
     U.S. Pat. No. 3,598,119 discloses a medical device for injecting drugs in which the injection needle is guided through an inner lumen of a catheter for insertion of the needle under skin tissue. A bladder at the distal end of the catheter may be inflated through another lumen for holding the point of the needle point in a fixed position beneath the skin. 
     U.S. Pat. No. 4,578,061 discloses a catheter for injecting a liquid into a vein, or artery, through an injection needle which is longitudinally movable beyond the distal end of the catheter. A dual chamber system is utilized within the catheter tip to provide for movement of a plunger to extend the injection needle and also to allow for a plunger to be used to apply a predetermined dose of medication through the injection needle. 
     U.S. Pat. No. 4,578,061 discloses an injection catheter having a longitudinal movable needle which may be moved through a lumen in order to extend out of the side wall of the catheter for injecting a liquid into a blood vessel. The needle is normally retracted into the device so that the needle will not penetrate tissue as the device is moved through a body duct. Thereafter, the needle is moved out of the side of the catheter into a vessel wall in order to infuse a liquid into the wall of a vessel. 
     U.S. Pat. No. 5,244,460 is directed toward a method for improving blood flow to the heart. More particularly this patent is directed toward a medical procedure for improving the growth of cardiac blood vessels by inserting a catheter into a coronary artery and injecting into the heart a blood vessel growth promoting peptide through an injection port of the catheter. 
     U.S. Pat. No. 5,419,777 is directed toward a catheter for injection of a fluid into body cavities such as coronary vessels and arteries. This patent, as is the case with the &#39;061 patent, illustrates the use of an injection needle which protrudes laterally through the side walls of the distal tip of the catheter. In the case of drug injections to be made into coronary vessels and arteries, it is very desirable to have the needles extend out of the side walls of the catheter and at an acute angle to the walls of the vessel in order to penetrate the walls of the vessel for injection of the agent. 
     U.S. Pat. No. 5,431,168, assigned to the same assignee as the present patent application, is directed toward a steerable catheter which includes a puller wire for controlling the distal end of the catheter from a control handle which is mounted on the proximal end of the catheter. 
     Copending U.S. patent application Ser. No. 09/019,453, entitled “Intracardiac Drug Delivery,” assigned to an affiliated company of the assignee of this application, discloses an injection catheter system for infusing a diagnostic or therapeutic agent into the wall of an organ which includes an electromagnetic sensor disposed within the distal tip of the catheter for providing very precise location information for the distal tip of the catheter. The subject matter of this copending patent application is incorporated by reference into the subject patent application. 
     SUMMARY OF THE INVENTION 
     This present invention is directed to a catheter for infusing therapeutic or diagnostic agents into the tissue of organs wherein the injection needle can also be used for mapping and ablation. In one embodiment, the injection catheter comprises a catheter body comprising a flexible tubing having proximal and distal ends and at least one lumen therethrough. A tip section comprising a flexible tubing having proximal and distal ends is mounted at the distal end of the catheter body. It is understood that the tip section and catheter body can be two separate components fixedly attached together or a single integral tubing wherein the tip section is the distal end of the tubing on which is mounted, for example, the tip electrode and ring electrodes. 
     A needle control handle is provided at the proximal end of the catheter body. An injection needle extends through the tip section, catheter body, and needle control handle and has a proximal end attached to the needle control handle and a distal end within the tip section. The injection needle is longitudinally slidable within the tip section so that its distal end can extend beyond the distal end of the tip section upon suitable manipulation of the needle control handle. An electrode lead wire is electrically connected to the injection needle and to a suitable monitoring apparatus or to a source of ablation energy. 
     In another embodiment, the invention is directed to a method for introducing a therapeutic or diagnostic agent into heart tissue of a patient. The method comprises introducing the distal end of a catheter as described above into the patient&#39;s heart. The injection needle is extended beyond the distal end of the tip section, and it is determined whether the injection needle has penetrated the heart tissue, preferably by measuring the impedance across the distal end of the injection needle. If the injection needle has penetrated the tissue, the therapeutic or diagnostic agent is injected into the heart tissue with the injection needle. Otherwise, the physician can reposition the distal end of the catheter and again attempt to penetrate the heart tissue. 
     In another embodiment, the invention is directed to a catheter comprising a catheter body, tip section and needle control handle as described above. An injection needle extends through the tip section, catheter body, and needle control handle and has a proximal end attached to the needle control handle and a distal end within the tip section. The injection needle is longitudinally slidable within the tip section so that its distal end can extend beyond the distal end of the tip section upon suitable manipulation of the needle control handle. An electrode is mounted on the injection needle near the distal end of the injection needle and electrically isolated from the injection needle. An electrode lead wire is electrically connected to the electrode and to a suitable monitoring apparatus or to a source of ablation energy. 
     In another embodiment, the invention is directed to a method for introducing a therapeutic or diagnostic agent into heart tissue of a patient. The method comprises introducing the distal end of a catheter as described in the preceding paragraph into the patient&#39;s heart. The injection needle is extended beyond the distal end of the tip section, and it is determined whether the injection needle has penetrated the heart tissue, preferably by measuring the impedance across the electrode mounted on the injection needle. If the injection needle has penetrated the tissue, the therapeutic or diagnostic agent is injected into the heart tissue with the injection needle. Otherwise, the physician can reposition the distal end of the catheter and again attempt to penetrate the heart tissue. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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 wherein: 
         FIG. 1  is a side plan view of one embodiment of the catheter of the present invention. 
         FIG. 2   a  is a side cross-sectional view of the needle control handle where the needle is in a retracted position. 
         FIG. 2   b  is a side cross-sectional view of the needle control handle where the needle is in an extended position. 
         FIG. 3A  is a side cross-sectional view of a tip section according to the invention having three lumens, showing the position of the electromagnetic mapping sensor and the injection needle. 
         FIG. 3B  is a side cross-sectional view of a tip section according to the invention showing a lead wire attached to the distal end of the injection needle. 
         FIG. 3C  is a side cross-sectional view of a tip section according to the invention showing an injection needle with a penetration-monitoring electrode mounted thereon. 
         FIG. 3D  is a close-up view of the penetration-monitoring electrode of  FIG. 3C . 
         FIG. 4  is a side cross-sectional view of the tip section of  FIG. 3A  showing the position of the electromagnetic mapping sensor and the puller wire. 
         FIG. 5  is a side cross-sectional view of the catheter body, including the junction between the catheter body and the section. 
         FIG. 6  is a transverse cross-sectional view of the tip section of  FIG. 3  along line  6 - 6  showing an embodiment having three lumens. 
         FIG. 7  is a transverse cross-sectional view of the catheter body along line  7 - 7 . 
         FIG. 8  is a side cross-sectional view of the catheter handle according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     In a preferred embodiment of the invention, there is provided a catheter for use for injection of a therapeutic or diagnostic agent into the heart. As shown in  FIG. 1 , 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, a deflection control handle  16  at the proximal end of the catheter body, and a needle control handle  17  proximal the catheter body. 
     With reference to  FIGS. 5 and 7 , the catheter body  12  comprises a single, central or axial lumen  18 . The catheter body  12  is flexible, i.e., bendable, but substantially non-compressible along its length. The catheter body  12  may be of any suitable construction and made of any suitable material. A presently preferred construction comprises an outer wall  22  made of a polyurethane or nylon. The outer wall  22  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  of the catheter will rotate in a corresponding manner. 
     The outer diameter of the catheter body  12  is not critical, but is preferably no more than about 8 French. Likewise the thickness of the outer wall  22  is not critical. The inner surface of the outer wall  22  is lined with a stiffening tube  20 , which can be made of any suitable material, preferably polyimide. The stiffening tube, along with the braided outer wall  22 , provides improved torsional stability while at the same time minimizing the wall thickness of the catheter, thus maximizing the diameter of the single lumen. The outer diameter of the stiffening tube  20  is about the same as or slightly smaller than the inner diameter of the outer wall  22 . Polyimide tubing is presently preferred because it may be very thin walled while still providing very good stiffness. This maximizes the diameter of the central lumen  18  without sacrificing strength and stiffness. Polyimide material is typically not used for stiffening tubes because of its tendency to kink when bent. However, it has been found that, in combination with an outer wall  22  of polyurethane, nylon or other similar material, particularly having a stainless steel braided mesh, the tendency for the polyimide stiffening tube  20  to kink when bent is essentially eliminated with respect to the applications for which the catheter is used. If desired, the stiffening tube  20  can be eliminated. 
     As shown in  FIGS. 3A ,  4  and  6 , the tip section  14  comprises a short section of tubing  19  having three lumens  30 ,  32  and  34 . The tubing  19  is made of a suitable non-toxic material that is preferably more flexible than the catheter body  12 . A presently preferred material for the tubing  19  is braided polyurethane, i.e., polyurethane with an embedded mesh of braided stainless steel or the like. The outer diameter of the tip section  14 , like that of the catheter body  12 , is preferably no greater than about 8 French. The size of the lumens is not critical. In a particularly preferred embodiment, the tip section has an outer diameter of about 7 French (0.092 inch) and the first lumen  30  and second lumen  32  are generally about the same size, having a diameter of about 0.022 inch, with the third lumen  34  having a slightly larger diameter of about 0.036 inch. 
     A preferred means for attaching the catheter body  12  to the tip section  14  is illustrated in  FIG. 5 . The proximal end of the tip section  14  comprises an inner counter bore  24  that receives the outer surface of the polyimide stiffener  20 . The tip section  14  and catheter body  12  are attached by glue or the like. 
     The stiffening tube  20  is held in place relative to the outer wall  22  at the proximal end of the catheter body  12 . In preferred construction of the catheter body  12 , a force is applied to the proximal end of the stiffening tube  20  that causes the distal end of the stiffening tube to firmly push against the counter bore  24 . While under compression, a first glue joint is made between the stiffening tube  20  and the outer wall  22  by a fast drying glue, e.g. Super Glue®. Thereafter a second glue joint is formed between the proximal ends of the stiffening tube  20  and outer wall  22  using a slower drying but stronger glue, e.g., polyurethane. Any other suitable method of attaching the catheter body  12  to the tip section  14  can be used. 
     Extending through the single lumen  18  of the catheter body  12  are lead wires  40 , an injection needle  46 , a sensor cable  74 , and a compression coil  44  through which a puller wire  42  extends. A single lumen  18  catheter body is preferred over a multi-lumen body because it has been found that the single lumen  18  body permits better tip control when rotating the catheter  10 . The single lumen  18  permits the lead wires  40 , the injection needle  46 , the sensor cable  74 , and the puller wire  42  surrounded by the compression coil  44  to float freely within the catheter body. If such wires and cables were restricted within multiple lumens, they tend to build up energy when the handle  16  is rotated, resulting in the catheter body  12  having a tendency to rotate back if, for example, the handle is released, or if bent around a curve, to flip over, either for which are undesirable performance characteristics. 
     With reference to  FIGS. 3A and 4 , mounted at the distal end of the tip section  14  is a tip electrode  36 . Preferably the tip electrode  36  has a diameter about the same as the outer diameter of the tubing  19 . The tip electrode  36  is connected to the tubing  19  by means of a plastic housing  21 , preferably made of polyetheretherketone (PEEK). The proximal end of the tip electrode  36  is notched circumferentially and fits inside the distal end of the plastic housing  21  and is bonded to the housing  21  by polyurethane glue or the like. The proximal end of the plastic housing  21  is bonded with polyurethane glue or the like to the distal end of the tubing  19  of the tip section  14 . Alternatively, the tip electrode  36  can be mounted directly to the distal end of the flexible tubing  19  of the tip section  14 , with the housing  21  eliminated. 
     Mounted on the distal end of the plastic housing  21  is a ring electrode  38 . The ring electrode  38  is slid over the plastic housing  21  and fixed in place by glue or the like. Alternatively, if the plastic housing  21  is eliminated, the ring electrode can be positioned over the flexible tubing  19  of the tip section  14 . If desired, additional ring electrodes may be used and can be positioned over the plastic housing  21  or over the flexible tubing  19  of the tip section  14 . 
     The tip electrode  36  and ring electrode  38  are each connected to a separate lead wire  40 . The lead wires  40  extend through the third lumen  34  of tip section  14 , the catheter body  12 , and the control handle  16 , and terminate at their proximal end in an input jack (not shown) that may be plugged into an appropriate monitoring system for measuring and displaying electrical activity (not shown) and/or a source of RF energy (not shown). If desired, the portion of the lead wires  40  extending through the catheter body  12 , control handle  16  and proximal end of the tip section  14  may be enclosed or bundled within a protective tube or sheath (not shown). 
     The lead wires  40  are attached to the tip electrode  36  and ring electrode  38  by any conventional technique. Connection of lead wire  40  to the tip electrode  36  is preferably accomplished by weld  43 , as shown in  FIG. 4 . 
     A puller wire  42  is provided for deflection of the tip section  14 . The puller wire  42  is anchored at its proximal end to the control handle  16  and anchored at its distal end in the tip section  14 , as discussed in more detail below. The puller wire  42  is made of any suitable metal, such as stainless steel or Nitinol, and is preferably coated with Teflon® or the like. The coating imparts lubricity to the puller wire  42 . The puller wire  42  preferably has a diameter ranging from about 0.006 to about 0.010 inches. 
     As discussed above, a compression coil  44  is provided in surrounding relation to a portion of the puller wire  42 . The compression coil  44  extends from the proximal end of the catheter body  12  to the proximal end of the tip section  14 . The compression coil  44  is made of any suitable metal, preferably stainless steel. The compression coil  44  is tightly wound on itself to provide flexibility, i.e., bending, but to resist compression. The inner diameter of the compression coil  44  is preferably slightly larger than the diameter of the puller wire  42 . For example, when the puller wire  42  has a diameter of about 0.007 inches, the compression coil  44  preferably has an inner diameter of about 0.008 inches. The Teflon® coating on the puller wire  42  allows it to slide freely within the compression coil  44 . Along most of its length, the outer surface of the compression coil  44  is covered by a flexible, non-conductive sheath  26  to prevent contact between the compression coil  44  and any of the lead wires  40 , injection needle  46  or sensor cable  74 . A non-conductive sheath  26  made of polyimide tubing is presently preferred. 
     In the depicted embodiment, the compression coil  44  is anchored at its proximal end to the proximal end of the stiffening tube  20  in the catheter body  12  by glue to foam a glue joint  50  and at its distal end to the tip section  14  in the second lumen  32 , also forming a glue joint  50 . If a stiffening tube  20  is not used, the proximal end of the compression coil  44  can be glued directly to the outer wall  22  of the catheter body  12 . 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  12  and the single lumen. Alternatively, the distal end of the compression coil  44  can be anchored in the distal end of the catheter body  12 , for example, by gluing the compression coil to the stiffening tube  20  or the outer wall  22 , if a stiffening tube is not used. 
     The puller wire  42  extends out of the distal end of the compression coil  44  and into the second lumen  32  of the tip section  14 . The distal end of the puller wire  42  is anchored to the tip electrode  36  or to the side of the tip section  14  by any suitable method known in the art. Examples of suitable methods for anchoring the puller wire  42  in the tip section  14  are described in U.S. Pat. Nos. 5,383,923 and 5,827,278, the disclosures of which are incorporated herein by reference. With reference to  FIGS. 4 and 5 , within the tip section  14 , and distal to the glue joint  50 , the turns of the compression coil  44  are expanded  49  longitudinally. The expanded turns  49  are both bendable and compressible and preferably extend for a length of about 0.5 inch. The puller wire  42  extends through the expanded turns  49  then into a plastic, preferably Teflon®, sheath  81 , which prevents the puller  42  from cutting into the wall of the tip section  14  when the tip section is deflected. If desired, the expanded turns  49  can be eliminated. 
     An extendable and retractable injection needle  46  is provided for injection of drugs and therapeutic and diagnostic agents into the heart tissue. The injection needle  46  extends from the needle control handle  17  through the catheter body  12 , through the first lumen  30  of the tip section  14  and through a passage  51  in the tip electrode  36 . As illustrated in  FIG. 3A , the injection needle  46  is preferably formed with a beveled edge  41  at the distal tip of the needle. The needle  46  is coaxially mounted within a protective tube  47 , preferably made of polyimide, which serves to prevent the needle from buckling and also serves to electrically insulate the needle from the tip electrode  36 . The protective tube  47  additionally serves to provide a fluid-tight seal surrounding the injection needle  46  to prevent body fluids from entering the distal end of the catheter. Preferably the protective tube  47  is provided along the entire length of the injection needle  46 , although it can cover only the distal portion of the injection needle if desired. 
       FIG. 3A  depicts the injection needle  46  extending beyond the distal end of the tip electrode  36 , as it would be positioned in order to infuse diagnostic or therapeutic fluid into the heart tissue. The catheter is designed to permit the distal end of the injection needle  46  to be withdrawn into the tip electrode  36  during the period of time that the catheter is inserted through the vasculature of the body and also during the period of time in which the catheter is removed from the body to avoid injury. Alternatively, the tip section  14  can be provided without a tip electrode  36 , in which case the distal end of the injection needle  46  could be retracted into the first lumen  30  of the tip section  14 . In either embodiment, the injection needle  46  is extendable and retractable beyond the distal end of the catheter. If desired, the catheter can include a needle stop mechanism for limiting the distance that the needle extends beyond the distal end of the tip section  14 . Such a mechanism is described in copending U.S. patent application Ser. No. 09/563,769, entitled “Injection Catheter with Needle Stop” to Dean Ponzi, the entire disclosure of which is incorporated herein by reference. 
     The injection needle  46  is made from one or more straight pieces of small diameter tubing having an outer diameter that allows the tubing to fit within the catheter. Preferably the injection needle  46  has an inner diameter ranging from about 0.007 inch to about 0.011 inch, and an outer diameter ranging from about 0.012 inch to about 0.016 inch. Preferably the injection needle  46  has a total length ranging from about 65 to about 85 inches, more preferably about 75 inches, although the length can vary as desired depending on the length of the catheter in which it is used and the application for which it is to be used. 
     In one embodiment, the injection needle  46  is formed of Nitinol or other conductive material. Alternatively, a portion of the needle is formed of plastic with the distal portion of the needle being formed of a conductive metal, such as Nitinol. The needle, whether all metal or part metal and part plastic, preferably has straight position memory so that when it is bent to a small radius, its natural tendency is to spring back to the straight position. This property is particularly important for the distal region of the injection needle (i.e., the portion of the needle within the tip section  14 ), because when the tip section is deflected, the needle will deflect with the tip section. When the tip section is then straightened from its deflected position, the memory of the distal region of the needle pushes the tip section back towards the straight position to the same axis as the catheter body. If desired, at least a portion of the tubing, such as the portion that forms the distal region of the needle, is provided with a lubricious coating, such as Teflon® or silicone, preferably having a thickness ranging from about 0.0003 inch to about 0.002 inch. In another alternative embodiment, a biocompatible lubricant, such as mineral oil is injected around the needle once assembled. 
     If desired, the distal end of the injection needle  46  is provide with one or more fluid openings (not shown) along its length. The fluid openings can be of any suitable shape, such as round, oval, or rectangular. The fluid openings can be provided only on one side of the needle  46 , or about the circumference of the needle. The fluid openings enhance the ability of the drug or other agent passing through the needle to weep into the injection site and be more evenly distributed, allowing for better absorption of the agent by the heart tissue. 
     A needle electrode lead wire  39  is electrically connected to the injection needle  46  to permit the injection needle to also function as an electrode. In one embodiment, the injection needle  46  comprises metal along its entire length, and the needle electrode lead wire  39  is attached near the proximal end of the injection needle within the deflection control handle  16 , as described in more detail below. 
     In an alternative embodiment, as shown in  FIG. 3B , the needle electrode lead wire  39  is electrically connected near the distal end of the injection needle  46  within the tip section  14 . In this embodiment, the needle electrode lead wire  39  extends within the protective tube  47  along with the injection needle  46 , and the distal end of the needle electrode lead wire is soldered, welded or otherwise electrically attached to the injection needle within the protective tube. In this embodiment, it is only necessary that the distal end of the injection needle  46 , i.e., the end to which the needle electrode lead wire  39  is attached, be made of metal, and the remainder of the injection needle can be made of metal or plastic, as desired. 
     Preferably in this embodiment the needle electrode lead wire  39  comprises a pair of wires, a first wire of a high conductivity material (e.g., copper) and a second wire of a high strength material different from the first material (e.g., constantan) non-conductively bonded to the first wire. This pair of wires acts as a thermocouple in addition to an electrode lead wire. More details on such an arrangement are disclosed in U.S. Pat. No. 5,893,885, the disclosure of which is incorporated herein by reference. If desired, the portion of the injection needle  46  to which the needle electrode lead wire  39  is attached can be covered with a thin coating of Teflon or the like (not shown) to enhance the ability of the injection needle to slide within the protective tube  47  and to prevent the needle electrode lead wire from getting stuck or caught on the protective tube as the injection needle is being slid in and out of the tip section  14 . 
     The injection needle  46  can be used to infuse therapeutic agents, diagnostic agents and the like. Particularly preferred agents include angiogenesis activators, angiogenesis inhibitors, and antiarrhythmic drugs. Examples of angiogenesis activators include vascular endothelial growth factor, vascular endothelial growth factor receptor, neuropilin-1, angiopoietins, such as Ang1,tyrosine kinases (Tie), such as Tie2, transforming growth factor-β1, transforming growth factor-β receptors, endoglin, chemokines, hepatocyte growth factor, monocyte chemoattractant protein-1 integrins, such as α v β 3 , α v β 5 , α 5 β 1 , VE-cahedrin, platelet-endothelial cell-adhesion molecule, ephrins, plasminogen activators, matrix metalloproteinases, and cyclo-oxygenase-2. Examples of angiogenesis inhibitors include vascular endothelial growth factor receptor-1, neuropilin-1, angiopoietins, such as Ang2, angiostatin and related plasminogen kringles, endostatin (collagen XVIII fragment), vasostatin, calreticulin, platelet factor-4, matrix metalloproteinase inhibitors, prothrombin kringle-2, antithrombin III fragment, maspin, canstatin, proliferin-related protein, and restin. Examples of antiarrhythmic drugs include sodium channel blockers, potassium channel blockers, membrane-stabilizing agents, and α-adrenoceptor blockers, β-adrenoceptor blockers and calcium channel blockers. 
     In use, the injection needle  46  can function as a mapping electrode and/or as an ablation electrode. For example, the injection needle  46  can be used to map the electrical activity of the heart, alone or in combination with the tip electrode  36  and/or ring electrodes  38 , prior to injection of a therapeutic or diagnostic agent into the heart tissue. Using this method, the physician can more precisely position the injection needle at a desired location. The invention is also contemplated for epicardial applications. 
     Alternatively, the injection needle  46  can be used to ablate heart tissue before, during or after injection of the therapeutic or diagnostic agent, as desired. Ablation often enhances the effectiveness of a therapeutic agent. Specifically, creating an injury that causes an inflamation response, which results in having white blood cells coming to injury site and fighting the inflamation, makes the target site susceptible to an agent. 
     Additionally, the injection needle  46  can be used to determine the extent of needle penetration in the heart tissue. For this methodology, it is preferred that the needle electrode lead wire  39  be attached to the proximal end of the injection needle  46 . During a procedure, the physician monitors the impedance of the injection needle  46  relative to the tip electrode  36  (or a ring electrode  38 , if a tip electrode is not used). If the distal end of the injection needle  46  is within the heart tissue, the difference in impedance will be relatively high (e.g., around 500 to 600Ω). Accordingly, the physician can then proceed to inject the therapeutic or diagnostic agent. In contrast, if the distal end of the injection needle  46  for some reason has not penetrated the heart tissue, but is only in contact with blood, the difference in impedance will be relatively low (e.g., around 100 to 150Ω). This information indicates to the physician that he or she should reattempt to penetrate the heart tissue with the needle before injecting the agent. 
     In another alternative embodiment, as shown in  FIGS. 3C and 3D , a penetration-monitoring electrode  48  is mounted on the injection needle  46  for monitoring whether and to what extent the injection needle has penetrated the tissue. In the depicted embodiment, the penetration-monitoring electrode  48  is electrically isolated from the injection needle  46  by a thin non-conductive (preferably Teflon) covering  59  on the needle. The penetration-monitoring electrode  48  can be mounted by any other suitable non-conductive method, such as with polyurethane glue. A lead wire  61  is electrically connected to the penetration-monitoring electrode  48  by any suitable means, such as weld, solder, or the like. The penetration-monitoring electrode  48  is positioned at a position along the length of the injection needle  46  that generally corresponds to the desired depth that the needle penetrate the heart tissue. In this embodiment, the injection needle  46  may optionally also act as a separate electrode, i.e., have an electrode lead wire  39  electrically connected thereto. 
     In use, once the physician believes he or she has penetrated the tissue with the injection needle  46 , he monitors the impedance of the penetration-monitoring electrode  48  relative to the tip electrode  36  (or a ring electrode  38 ). If the penetration-monitoring electrode  48  is in contact with the heart tissue, the difference in impedance will be relatively high, and if the penetration-monitoring electrode is not in contact with the tissue, but only in contact with blood, the difference in impedance will be relatively low. Similar to the method described above, this information indicates to the physician whether the injection needle has penetrated the heart tissue at the desired depth. 
     Additionally, a location sensor, preferably an electromagnetic location sensor  72 , is contained within the distal end of the tip section  14 . The electromagnetic sensor  72  is connected to the electromagnetic sensor cable  74 , which extends through the third lumen  34  of the tip section  14 , through the catheter body  12 , and into the deflection control handle  16 . The electromagnetic sensor cable  74  comprises multiple wires encased within a plastic sheath. In the deflection control handle  16 , the wires of the sensor cable  74  are connected to a circuit board  64 . The circuit board  64  amplifies the signal received from the electromagnetic sensor and transmits it to a computer in a form understandable by the computer. Also, because the catheter is designed for single use only, the circuit board contains an EPROM chip which shuts down the circuit board after the catheter has been used. This prevents the catheter, or at least the electromagnetic sensor, from being used twice. Suitable electromagnetic sensors for use in connection with the present invention are described, for example, in U.S. Pat. No. 4,391,199 and U.S. patent application Ser. No. 09/160,063, entitled “Miniaturized Position Sensor,” the disclosures of which are incorporated herein by reference. A preferred electromagnetic mapping sensor  72  is manufactured by Biosense Webster, Inc. and marketed under the trade designation NOGA. To use the electromagnetic sensor  72 , the patient is placed in a magnetic field generated, for example, by situating under the patient a pad containing coils for generating a magnetic field. A reference electromagnetic sensor is fixed relative to the patient, e.g., taped to the patient&#39;s back, and the injection catheter containing a second electromagnetic sensor is advanced into the patient&#39;s heart. Each sensor comprises three small coils which in the magnetic field generate weak electrical signals indicative of their position in the magnetic field. Signals generated by both the fixed reference sensor and the second sensor in the heart are amplified and transmitted to a computer which analyzes the signals and then displays the signals on a monitor. By this method, the precise location of the sensor in the catheter relative to the reference sensor can be ascertained and visually displayed. The sensor can also detect displacement of the catheter that is caused by contraction of the heart muscle. 
     Using this technology, the physician can visually map a heart chamber. This mapping is done by advancing the catheter tip into a heart chamber until contact is made with the heart wall. This position is recorded and saved. The catheter tip is then moved to another position in contact with the heart wall and again the position is recorded and saved. 
     The electromagnetic mapping sensor  72  can be used alone or, more preferably, in combination with the needle electrode  46 , tip electrode  36  and/or ring electrode  38 . By combining the electromagnetic sensor  72  and one or more of the electrodes  46 ,  36  and/or  38 , a physician can simultaneously map the contours or shape of the heart chamber, the electrical activity of the heart, and the extent of displacement of the catheter and hence identify the presence and location of the ischemic tissue. Specifically, the electromagnetic mapping sensor  72  is used to monitor the precise location of the tip electrode in the heart and the extent of catheter displacement. The needle electrode  46 , tip electrode  36  and ring electrode  38  can be used to monitor the strength of the electrical signals at that location. Healthy heart tissue is identified by strong electrical signals in combination with strong displacement. Dead or diseased heart tissue is identified by weak electrical signals in combination with dysfunctional displacement, i.e., displacement in a direction opposite that of healthy tissue. Ischemic, or hibernating or stunned, heart tissue is identified by strong electrical signals in combination with impaired displacement. Hence, the combination of the electromagnetic mapping sensor  72  and needle, tip and/or ring electrodes  46 ,  36  and  38  is used as a diagnostic catheter to determine whether and where to infuse a drug into the wall of the heart. Once the presence and location of ischemic tissue has been identified, the tip section  14  of the catheter can be deflected so that the injection needle  46  is generally normal, i.e., at a right angle, to the ischemic tissue. The injection needle  46  may then be extended out of the distal end of the tip electrode  36  (if not already extended for mapping purposes) and into the wall of the heart. 
     It is understood that, while it is preferred to include both electrophysiology electrodes and an electromagnetic sensor in the catheter tip, it is not necessary to include both. For example, an injection catheter having an electromagnetic sensor but no electrophysiology electrodes may be used in combination with a separate mapping catheter system. A preferred mapping system includes a catheter comprising multiple electrodes and an electromagnetic sensor, such as the NOGA-STAR catheter marketed by Biosense Webster, Inc., and means for monitoring and displaying the signals received from the electrodes and electromagnetic sensor, such as the Biosense-NOGA system, also marketed by Biosense Webster, Inc. 
     The electrode lead wires  40  and electromagnetic sensor cable  74  must be allowed some longitudinal movement within the catheter body so that they do not break when the tip section  14  is deflected. To provide for such lengthwise movement, there is provided a tunnel through the glue joint  50 , which fixes the proximal end of the compression coil  44  inside the catheter body  12 . The tunnel is formed by a transfer tube  27 , preferably made of a short segment of polyimide tubing. Preferably the transfer tube  27  is approximately 60 mm long and has an outer diameter of about 0.021 inch and an inner diameter of about 0.019 inch. 
     Longitudinal movement of the puller wire  42  relative to the catheter body  12 , which results in deflection of the tip section  14 , is accomplished by suitable manipulation of the deflection control handle  16 . As shown in  FIG. 8 , the deflection control handle  16  comprises a handle housing  52  and a piston  54  having an axial passage  55  and a thumb control  56 . The proximal end of the catheter body  12  is connected to the piston  54  by means of a shrink sleeve  28 . 
     The injection needle  46  within the protective tube  47 , the puller wire  42 , the lead wires  40  and the electromagnetic sensor cable  74  extend through the axial passage  55  of the piston  54 . The puller wire  42  is anchored to an anchor pin  57  located proximal to the piston  54 . The lead wires  40  and electromagnetic sensor cable  74  extend through a first tunnel  58  in the handle housing  52 , located near a side of the deflection control handle  16 . The electromagnetic sensor cable  74  connects to the circuit board  64  in the proximal end of the deflection control handle  16 . Wires  80  connect the circuit board  64  to a computer and imaging monitor (not shown). 
     The injection needle  46  and protective tube  47  extend through a guide tube  66 , preferably made of polyurethane, and are afforded longitudinal movement therein. The guide tube  66  is anchored to the piston  54 , preferably by a glue joint  53 . This design affords the injection needle  46  and protective tube  47  longitudinal movement within the deflection control handle  16  so that the needle does not break when the piston  54  is adjusted to manipulate the catheter body  12  relative to the handle housing  52  and the puller wire  42 . Within the piston  54 , the electromagnetic sensor cable  74  and lead wires  40  are situated within a first transfer tube  27   a , and the puller wire  42  is situated within a second transfer tube  27   b  to allow longitudinal movement of the wires and cable near the glue joint  53 . 
     The injection needle  46 , protective tube  47  and guide tube  66  extend through a second tunnel  60  in the handle housing  52  situated near the side of the control handle  16  opposite the anchor pin  57 . To avoid undesirable bending of the injection needle  46 , a space  62  is provided in the handle housing  52  between the proximal end of the piston  54  and the distal end of the second tunnel  60 . Preferably the space  62  has a length of at least about 0.50 inch and more preferably about from about 0.60 inch to about 0.90 inch. 
     In the proximal end of the deflection control handle  16 , the injection needle  46 , protective tube  47  and polyurethane guide tube  66  extend through a second larger plastic guide tube  68 , preferably made of Teflon®, which affords the guide tube  66 , injection needle  46 , and protective tube  47  longitudinal slidable movement. The second guide tube  68  is anchored to the inside of the handle housing  52  by glue or the like and extends proximally beyond the control handle  16 . The second guide tube  68  protects the injection needle  46  both from contact with the circuit board  64  and from any sharp bends as the guide tube  66 , needle  46 , and protective tube  47  emerge from the deflection control handle  16 . 
     In the depicted embodiment, the needle electrode lead wire  39  is electrically connected to the injection needle  46  within the deflection control handle  16 . Specifically, a hole  67  is provided in the guide tube  66  and protective tube  47 . The needle electrode lead wire  39  passes through the hole  67  and is attached to the injection needle  46  by weld, solder or the like within the guide tube  66  and protective tube  47 . Alternatively, for the embodiment depicted in  FIG. 3B , where the needle electrode lead wire  39  is connected to the distal end of the injection needle  46 , the needle electrode lead wire passes through the hole  67  and extends along the length of the injection needle  46  like within the guide tube  66  and protective tube  47 . 
     Extension and retraction of the injection needle  46  out the distal end of the tip electrode  36  is accomplished by the needle control handle  17 . As illustrated in  FIGS. 2   a  and  2   b , the needle control handle  17  comprises a generally cylindrical outer body  80  having proximal and distal ends, a piston chamber  82  extending a part of the way therethrough, and a needle passage  83  extending a part of the way therethrough. The piston chamber  82  extends from the proximal end of the needle control handle part way into the body  80 , but does not extend out the distal end of the body. The needle passage  83 , which has a diameter less than that of the piston chamber  82 , extends from the proximal end of the piston chamber to the proximal end of the outer body  80 . 
     A piston  84 , having proximal and distal ends, is slidably mounted within the piston chamber  82 . The piston  84  has an axial passage  85  through which the injection needle  46  extends, as described in more detail below. A Luer connector  86  is mounted in the distal end of the outer body  80 . A compression spring  88  is mounted within the piston chamber  82  between the distal end of the piston  84  and the outer body  80 . 
     The proximal end of the injection needle  46  is mounted to the Luer connector  86  by means of a first rigid tube  90 , preferably made of stainless steel, which has a proximal end fitted into the Luer connector. This arrangement fixedly attaches the injection needle  46  to the piston  84  so that it moves longitudinally with the piston. The first rigid tube  90  is also fixedly attached to the piston  84  and moves longitudinally with the piston. The injection needle  46  and first rigid tube  90  extend through the axial passage  85  of the piston  84 . Within the axial passage  85 , a second rigid tube  91 , preferably made of stainless steel, has a proximal end mounted coaxially within the distal end of the first rigid tube  90 . The proximal end of the second rigid tube  91  is mounted within the protective tube  47 , which has its proximal end inside the axial passage  85 , and the distal end of the second rigid tube is attached, directly or indirectly, to the outer body  80 . The guide tube  66 , through which the protective tube  47  and injection needle  46  extend, as discussed above, is fixedly attached to the outer body  80  by means of a shrink sleeve  92 , as is generally known in the art. 
     In use, force is applied to the piston  84  to cause distal movement of the piston relative to the outer body  80 , which compresses the compression spring  88 . This movement causes the injection needle  46  to correspondingly move distally relative to the outer body, guide tube  66 , protective tube  47  and catheter body  12 , so that the distal end of the injection needle extends outside the distal end of the tip electrode  36 . Upon distal movement of the piston  84 , the first rigid tube  91  moves distally over the second rigid tube  91  to prevent the injection needle  46  from buckling within the axial passage  85 . When the force is removed from the piston  54 , the compression spring  88  pushes the piston  84  proximally to its original position, thus causing the distal end of the injection needle  46  to retract back into the tip electrode  36 . 
     The piston  84  further comprises a longitudinal slot  100  extending along a portion of its outer edge. A set screw  102  extends through a hole in the outer body  80  and into the longitudinal slot  100 . This design limits the distance that the piston  84  can be slid proximally out of the piston chamber  82 , and, if desired, the distance that the piston can be slid distally to extend the injection needle  46 . When the distal end of the injection needle  46  is in the retracted position, preferably the set screw  102  is at or near the distal end of the longitudinal slot  100 . 
     The proximal end of the piston  84  has a threaded outer surface  104 . A circular thumb control  106  is mounted on the proximal end of the piston  84 . The thumb control  106  has a threaded inner surface  108  that interacts with the threaded outer surface  104  of the piston  84 . The thumb control  106  acts as a stop, limiting the distance that the piston  84  can be pushed into the piston chamber  82 , and thus the distance that the injection needle  46  can be extended out the distal end of the catheter. The threaded surfaces of the thumb control  106  and piston  84  allow the thumb control to be moved closer or farther from the proximal end of the outer body  80  so that the extension distance of the injection needle can be controlled by the physician. A tension screw  110  is provided in the thumb control  106  to control the tension between the thumb control and piston  84 . As would be recognized by one skilled in the art, the thumb control  106  can be replaced by any other mechanism that can act as a stop for limiting the distance that the piston  84  extends into the piston chamber  82 , and it is not necessary, although it is preferred, that the stop be adjustable relative to the piston. 
     In another preferred embodiment constructed in accordance with the present invention, two or more puller wires (not shown) are provided to enhance the ability to manipulate the tip section. In such an embodiment, a second puller wire and a surrounding second compression coil extend through the catheter body and into separate off-axis lumens in the tip section. The lumens of the tip section receiving the puller wires may be in adjacent quadrants. The first puller wire is preferably anchored proximal to the anchor location of the second puller wire. The second puller wire may be anchored to the tip electrode or may be anchored to the wall of the tip section adjacent the distal end of tip section. 
     The distance between the distal end of the compression coils and the anchor sites of each puller wire in the tip section determines the curvature of the tip section  14  in the direction of the puller wires. For example, an arrangement wherein the two puller wires are anchored at different distances from the distal ends of the compression coils allows a long reach curve in a first plane and a short reach curve in a plane 90° from the first, i.e., a first curve in one plane generally along the axis of the tip section before it is deflected and a second curve distal to the first curve in a plane transverse, and preferably normal to the first plane. The high torque characteristic of the catheter tip section  12  reduces the tendency for the deflection in one direction to deform the deflection in the other direction. Suitable deflection control handles for use with such a catheter are described in U.S. Pat. No. 6,123,699, entitled “Omni-Directional Steerable Catheter”, and U.S. patent application Ser. No. 09/130,359, filed Aug. 7, 1998, entitled “Bi-Directional Control Handle for Steerable Catheter”, Ser. No. 09/143,426, filed Aug. 28, 1998, entitled “Bidirectional Steerable Catheter with Bidirectional Control Handle”, and Ser. No. 09/546,310, filed Apr. 10, 2000, entitled “Single Gear Drive Bidirectional Control Handle for Steerable Catheter”, the disclosures of which are incorporated herein by reference. 
     As an alternative to the above described embodiment, two puller wires may extend into diametrically opposed off-axis lumens in the tip section. In such an embodiment, each of the puller wires may be anchored at the same location along the length of the tip section, in which case the curvatures of the tip section in opposing directions are the same and the tip section can be made to deflect in either direction without rotation of the catheter body. 
     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 meaningful 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.