Patent Publication Number: US-7905864-B2

Title: Injection catheter with multi-directional delivery injection needle

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 09/562,611, filed May 1, 2000 now U.S. Pat. No. 6,623,473 which claims priority of U.S. Provisional Patent Application No. 60/165,354, filed Nov. 12, 1999, and 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 priority of U.S. Provisional Patent Application Nos. 60/088,019, filed Jun. 4, 1998 and Ser. No. 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 provides multi-directional drug delivery. 
     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 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 agent to the desired site, injecting the therapeutic 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. 
     Copending U.S. patent application Ser. No. 09/280,202 describes an injection catheter with an injection needle that has a passage therethrough, whereby a therapeutic agent is administered through the distal end of the needle. However, the efficiency at which the catheter delivers the drug is very important. One of the most difficult problems with therapeutic angiogenesis is getting the drug or other agent to properly absorb into the heart muscle to maximize its effect. If the drug is not properly injected and absorbed into the muscle, it may promote the growth of cancer cells or the spread of preexisiting cells throughout the body. It is undesirable to grow new blood vessels in certain parts of the body, such as the eyes or the kidneys. 
     SUMMARY OF THE INVENTION 
     This present invention is directed to a catheter for infusing therapeutic or diagnostic agents into the tissue of organs having an improved injection needle that provides multidirectional delivery. This design helps distribute a drug or other therapeutic agent more evenly into the heart muscle. 
     In accordance with the invention, the catheter comprises a catheter body comprising a flexible tubing having proximal and distal ends and at least one lumen therethrough. The catheter further comprises a tip section comprising a flexible tubing having proximal and distal ends, wherein the proximal end of the tip section is mounted at the distal end of the catheter body. A needle control handle is provided at the proximal end of the catheter body. An injection needle comprising elongated tubing extends through the tip section, catheter body, and needle control handle. The injection needle has a proximal end attached to the needle control handle, a distal region within the tip section, and an open distal end. The injection needle is longitudinally slidable within the tip section so that its distal region can extend beyond the distal end of the tip section upon suitable manipulation of the needle control handle. The distal region of the injection needle has at least one fluid port along its length. In use, fluid passes out of the needle through the open distal end and the at least one fluid opening along the length of the distal region. 
    
    
     
       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. 3  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. 
         FIGS. 3A ,  3 B, and  3 C are end cross-sectional views of alternative embodiments of injection needles in accordance with the invention. 
         FIG. 4  is a side cross-sectional view of the tip section of  FIG. 3  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. 
     
    
    
     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  12 , a deflection control handle  16  at the proximal end of the catheter body  12 , 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 of the catheter  10  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. 3 ,  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 which 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  which causes the distal end of the stiffening tube  20  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. 3 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 . 
     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. 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 inputjack (not shown) that may be plugged into an appropriate monitor (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. 
     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 to the tip section  14 . 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 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 nonconductive sheath  26  made of polyimide tubing is presently preferred. 
     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 form 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 . 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. 
     The puller wire  42  extends 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 catheter tip section  14 . 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 are expanded longitudinally. Such 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 section  14  is deflected. 
     An injection needle  46  is provided, which comprises an elongated tubing including an internal bore defined by the inner annular surface of the tubing. The injection needle  46  extends from the needle control handle 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. 3 , the injection needle  46  is preferably formed with a beveled edge at the distal end 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 distal electrode  36 . The protective tube  47  additionally serves to provide a fluid-tight seal surrounding the injection needle  46 . 
     The injection needle has a distal region that is maintained within the tip section  14 , including the tip electrode  36 , and that is extendable beyond the distal end of the tip section.  FIG. 3  depicts the distal region of 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 human heart. The distal region of the injection needle  46  is withdrawn into the tip section  14 , including the tip electrode  36  if provide, 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 entitled “Injection Catheter with Needle Stop” to Dean Ponzi, filed on even date herewith, the entire disclosure of which is incorporated herein by reference. 
     The elongated tubing that forms the injection needle  46  can be made from a single piece of tubing or a plurality of pieces of tubing connected together at their ends, which can be made from the same material or different materials. In one embodiment, the injection needle  46  is made from a single piece of Nitinol tubing. Other suitable materials for the tubing are described in copending U.S. Patent Application entitled “Catheter with Injection Needle” to Dean Ponzi, filed on even date herewith, the entire disclosure of which is incorporated herein by reference. Preferably the elongated tubing forming 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. 
     The distal end of the injection needle  46  is open so that fluids, such as drugs and other agents, such as therapeutic or diagnostic agents, can pass through the internal bore of the needle and out the distal end. Additionally, the distal region of the injection needle  46 , i.e., that portion of the needle that is extendable beyond the distal end of the tip section  14 , is provided with one or more fluid ports  45  along its length, through which fluid can also pass. The fluid ports  45  can be of any suitable shape, such as round, oval, or rectangular (e.g., vertical or horizontal slots), and can be formed by any suitable method, such as by laser drilling. The fluid ports  45  can be provided on only one side of the needle  46 , as shown in  FIG. 3A , about the circumference of the needle, as shown in  FIG. 3B , or only on selected sides of the needle, as shown in  FIG. 3C . Preferably at least 3 fluid ports are provided, more preferably at least 5 fluid ports are provided. Preferably each fluid port  45  has a length ranging from about 0.005 inch to about 0.04 inch, more preferably about 0.02 inch. In a particularly preferred embodiment, four fluid ports are provided, with the most distal fluid port positioned a distance of about 2 inches from the distal end of the needle, and with a distance of about 0.02 inch provided between the fluid ports. In this preferred embodiment, two fluid ports are provided on one side of the needle, with the other two fluid ports on the opposite side of the needle. The fluid ports  45  enhance the ability of the drug or other agent passing through the needle to weep into the injection side and be more evenly distributed, allowing for better absorption of the agent by the heart tissue. 
     Additionally, an electromagnetic sensor  72  is contained within the distal end of the tip section  14 . The electromagnetic sensor  72  is connected to an electromagnetic sensor cable  74 , which extends through the third lumen  34  of the tip section  14  through the catheter body  12  into the control handle  16 . The electromagnetic sensor cable  74  comprises multiple wires encased within a plastic sheath. In the 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 tip electrode  36  and ring electrode  38 . By combining the electromagnetic sensor  72  and electrodes  36  and  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 tip electrode  36  and ring electrode  38  are 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 tip and ring electrodes  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, and the injection needle may then be extended out of the distal end of the tip electrode  36  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 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  12 , is accomplished by suitable manipulation of the control handle  16 . As shown in  FIG. 8 , the distal end of the control handle  16  comprises a piston  54  with a thumb control  56  for manipulating the puller wire  42 . 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 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 , located near the side of the control handle  16 . The electromagnetic sensor cable  74  connects to the circuit board  64  in the proximal end of the control handle. Wires  73  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 glue at glue joint  53 . This design allows the needle  46  and protective tube  47  longitudinal movement within the control handle  16  so that the needle  46  does not break when the piston  54  is adjusted to manipulate the puller wire  42 . Within the piston  54 , the electromagnetic sensor cable  74  and lead wires  40  are situated within a transfer tube  27   a , and the puller wire  42  is situated within another 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  situated near the side of the control handle  16  opposite the anchor pin  36 . To avoid undesirable bending of the injection needle  46 , a space  62  is provided 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 0.50 inch and more preferably about from about 0.60 inch to about 0.90 inch. 
     In the proximal end of the 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 control handle  16  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 control handle  16 . 
     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 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 . A Luer connector  86  is mounted in the distal end of the outer body. The piston  84  has an axial passage  85  through which the injection needle  46  extends, as described in more detail below. 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  21 , 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 . When the force is removed from the piston, 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 . 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 . 
     The piston  84  further comprises a longitudinal slot  100  extending along a portion of its outer edge. A set screw  102  extends through the outer body  80  and into the longitudinal slot  100 . This design limits the distance that the piston can be slid proximally out of the piston chamber  82 . 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. The thumb control  106  has a threaded inner surface  108  that interacts with the threaded outer surface  104  of the piston. 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. Nos. 6,123,699, 6,171,277, 6,183,463, and 6,468,260, the disclosures of which are incorporated herein by reference. 
     As an alternative to the above described embodiment, the puller wires (not shown) 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.