Patent Publication Number: US-6210362-B1

Title: Steerable catheter for detecting and revascularing ischemic myocardial tissue

Description:
This application is a continuation of application Ser. No. 08/924,622, filed Sep. 5, 1997, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to steerable catheters which are particularly useful in direct myocardial revascularization procedures. 
     BACKGROUND OF THE INVENTION 
     Direct myocardial revascularization (DMR), also referred to as percutaneous myocardial revascularization, is a technique that allows physicians to treat patients who have sustained a myocardial infraction by burning channels in the myocardium that has been determined to be ischemic heart tissue. The channels, which are burned by a laser, allow for angiogenesis, i.e., the formation of blood vessels. 
     Several myocardial revascularization procedures are known that require that the chest wall be opened to access the heart muscle with laser devices. The procedures are not very desirable, as they require major surgery that can result in severe complications. Aita et al., U.S. Pat. No. 5,389,096, describes a procedure for performing myocardial revascularization percutaneous by inserting a guidable elongated flexible lasing apparatus, such as a catheter, into a patient&#39;s vasculature. The distal end of the catheter is guided to an area in the heart to be revascularized. The inner wall of the heart is then irradiated with laser energy to cause a channel to be formed from the endocardium into the myocardium. 
     For obvious reasons, DMR catheters require the physician to have more control and information than other catheters having an optic fiber, such as ablation catheters. Aita et al. generally describes a DMR catheter. The present invention is directed to an improved DMR catheter which allows the physician to have greater control and obtain more information than the catheter described in Aita el al. 
     SUMMARY OF THE INVENTION 
     The present invention provides a steerable catheter particularly useful in DMR procedures used to treat ischemic heart tissue. The steerable DMR catheter comprises a catheter body or shaft, a tip section attached to the distal end of the catheter body and a control handle attached to the proximal end of the catheter body. A puller wire is anchored at its proximal end in the control handle and extends through a lumen in the catheter body and a lumen in the tip section and is anchored at or about the distal end of the tip section. Manipulation of the control handle results in deflection of the tip section. An optic fiber suitable for transmission of laser energy extends through the control handle, catheter body and tip section, the distal end of the optic fiber being generally flush with the distal end surface of the tip section. The proximal end of the optic fiber extends proximally from the control handle to a suitable connector which connects the optic fiber to a source of laser energy. The optic fiber is used to transmit laser energy for creating channels, i.e. blind holes, in the heart tissue which induces revascularization. 
     In a preferred embodiment of the invention, the tip section of the DMR catheter comprises an electromagnetic sensor. The electromagnetic sensor is connected to a circuit board by means of a sensor cable which extends proximally through the tip section, catheter body, and control handle. The circuit board is preferably housed in the handle. Signals from the circuit board are transmitted through a cable to a computer and monitor. The electromagnetic sensor allows a physician to create a visual representation of the heart chamber and to view the location of the sensor, and therefore the catheter tip, within the chamber. 
     In another preferred embodiment, the DMR catheter comprises a tip electrode and one or more ring electrodes spaced proximally from the tip electrode. Each electrode is connected by means of electrode lead wires which extend through the tip section, catheter body and control handle to an appropriate connector, and from there, to a suitable monitor. The tip and ring electrodes allow the electrical activity of the heart tissue to be mapped. In a particularly preferred embodiment of the invention, the DMR catheter comprises both an electromagnetic sensor within the tip section and a tip electrode and one or more ring electrodes. This combination allows a physician to map the electrical activity of the heart wall of a particular chamber, e.g., the left ventricle, by means of the tip and ring electrodes to determine ischemic areas and simultaneously to record the precise location of the tip section within the heart by means of the electromagnetic sensor to create a three-dimensional representation of the heart chamber which is displayed visually on a monitor. Once an ischemic area has been mapped, the tip section is moved to that area and deflected to allow the optic fiber to be generally normal to the heart wall, and then laser energy is transmitted onto the heart tissue for creating a channel within the heart tissue. 
     In another aspect of the invention, the optic fiber comprises a protective jacket, preferably made out of aluminum. The optic fiber extends through the control handle and catheter body and into the tip section which carries a tip electrode. In the tip section, the optic fiber extends through an optic fiber lumen in the tip electrode, the distal end of the optic fiber being flush with the distal face of the tip electrode. The aluminum jacket is removed from the distal portion of the optic fiber which extends through the tip electrode. This removal avoids the possibility that particles of the aluminum jacket may break free into the heart, especially during laser transmission, which could result in a stroke. This removal also prevents the possibility of an electrical short between the aluminum jacket and the tip electrode, which could result in the patient receiving a lethally high voltage during laser transmission. 
     In another aspect of the invention, there is provided a DMR catheter having an infusion tube which extends from the proximal end of the catheter body through a lumen in the catheter body and into the tip section. The distal end of the infusion tube is open at the distal end of the tip section at a position adjacent the optic fiber so that fluids, including drugs to induce angiogenesis, may be passed through the catheter to the heart tissue. In a preferred embodiment, the DMR catheter comprises an infusion tube and a tip electrode having an infusion passage adjacent the optic fiber lumen. The infusion tube is connected to, preferably inserted into, the infusion passage in the tip electrode so that fluids passing through the infusion tube will enter and pass through the infusion passage in the tip electrode and to the heart tissue. The proximal end of the infusion tube terminates in a luer hub or the like. 
     In yet another aspect of the invention, the catheter body or shaft comprises a construction which exhibits improved torsional stability, resulting in improved tip control while minimizing wall thickness. The catheter body comprises a single central lumen and is formed by a tubular outer wall of polyurethane or nylon with a braided stainless steel mesh imbedded in the outer wall. The inner surface of the outer wall is lined with a stiffening tube, preferably made of polyimide or the like. The use of a polyimide stiffening tube provides improved torsional stability while at the same time minimizing the wall thickness of the catheter. This, in turn, maximizes the diameter of the central lumen. Such a construction is particularly useful in steerable DMR catheters in which an optic fiber, a puller wire, electrode leads, and an electromagnetic sensor cable all extend through the lumen of the catheter body, but is also useful in other steerable catheter constructions. 
     A preferred construction of the DMR catheter also includes a tubular spacer, between the polyimide stiffening tube and the tip section. The spacer is made of a material less stiff than the material of the stiffening tube, e.g., polyimide, but more stiff than the material of the tip section, e.g., polyurethane. Teflon® is the presently preferred material of the spacer. 
     In a preferred method for constructing the catheter, the stiffening tube is inserted into the tubular outer wall until the distal end of the stiffening tube butts against the tubular spacer. Force is applied to the proximal end of the stiffening tube which tube is then fixed in position, e.g., by glue, to the outer wall. The application of force on the proximal end of the stiffening tube assures that no gaps will form between the stiffening tube and tubular spacer or between the spacer and tip section as a result of repeated tip deflection. 
     In a steerable catheter construction comprising a stiffening tube and spacer, a puller wire preferably extends through a non-compressible compression coil which is fixed at its proximal end to the proximal end of the catheter body by means of a glue joint and fixed at its distal end to the proximal end of the tip section at a location distal to the spacer by means of a second glue joint. This arrangement prevents compression of the spacer during tip deflection which, in turn, permits the use of a thin walled spacer. 
     In yet another aspect to the invention, a control handle is provided which can be manipulated to deflect the tip section of the catheter. The control handle has a first member which is attached to the catheter body and a second member movable with respect to the first member, which is attached to the puller wire. In this arrangement, movement of the first member relative to the second member results in deflection of the tip. The handle comprises a guide tube through which the optic fiber extends. The guide tube is fixedly secured to the first or second member. Within this guide, the optic fiber is afforded lengthwise movement with respect to both the first and second members. 
    
    
     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 cross-sectional view of an embodiment of the catheter of the invention. 
     FIG. 2 a  is a side cross-sectional view of the catheter tip section showing an embodiment having three lumens and showing the position of the electromagnetic mapping sensor and the optic fiber. 
     FIG. 2 b  is a side cross-sectional view of the catheter tip section showing an embodiment having three lumens and showing the position of the electromagnetic mapping sensor and the puller wire. 
     FIG. 3 is a side cross-sectional view of the catheter body, including the junction between the catheter body and the tip section. 
     FIG. 4 is a side cross-sectional view of the catheter handle. 
     FIG. 5 is a transverse cross-sectional view of the catheter tip section along line  5 — 5  showing an embodiment having three lumens. 
     FIG. 6 is a transverse cross-sectional view of the catheter body along line  6 — 6 . 
     FIG. 7 is a side cross-sectional view of the catheter body showing an infusion tube. 
     FIG. 8 is a transverse cross-sectional view of the catheter tip section showing an alternative embodiment having an infusion tube. 
     FIG. 9 is a cross-sectional view of a portion of the catheter tip section showing a preferred means for anchoring the puller wire. 
     FIG. 10 is a top cross-sectional view of a preferred puller wire anchor. 
     FIG. 11 is a side cross-sectional view of a preferred puller wire anchor. 
    
    
     DETAILED DESCRIPTION 
     In a particularly preferred embodiment of the invention, there is provided a catheter for use in direct myocardial revascularization (DMR). As shown in FIGS. 1-4, catheter  10  comprises an elongated catheter body  12  having proximal and distal ends, a tip section  14  at the distal end of the catheter body  12 , and a control handle  16  at the proximal end of the catheter body  12 . 
     With reference to FIGS. 3 and 6, the catheter body  12  comprises an elongated tubular construction having 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  can 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 sectionally 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 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. 
     A particularly preferred catheter has an outer wall  22  with an outer diameter of about 0.092 inch and an inner diameter of about 0.063 inch and a polyimide stiffening tube having an outer diameter of about 0.0615 inch and an inner diameter of about 0.052 inch. 
     As shown in FIGS. 2 a  and  2   b , the tip section  14  comprises a short section of tubing  19  having three lumens. 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.  3 . The proximal end of the tip section  14  comprises an outer circumferential notch  24  that receives the inner surface of the outer wall  22  of the catheter body  12 . The tip section  14  and catheter body  12  are attached by glue or the like. In the arrangement shown, a spacer  52  lies within the catheter body  12  between the distal end of the stiffening tube  20  and the proximal end of the tip section  14 . The spacer  52  is preferably made of a material which is stiffer than the material of the tip section  14 , e.g., polyurethane, but not as stiff as the material of the stiffening tube  20 , e.g., polyimide. A spacer made of Teflon® is presently preferred. A preferred spacer  52  has a length of from about 0.25 inch to about 0.75 inch, more preferably about 0.5 inch. Preferably the spacer  52  has an outer and inner diameter about the same as the outer and inner diameters of the stiffening tube  20 . The spacer  52  provides a transition in flexibility at the junction of the catheter body  12  and catheter tip  14 , which allows the junction of the catheter body  12  and tip section  14  to bend smoothly without folding or kinking. 
     The spacer  52  is held in place by the stiffening tube  20 . The stiffening tube  20 , in turn, is held in place relative to the outer wall  22  by glue joints  23  and  25  at the proximal end of the catheter body  12 . In a 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 butt up against and compress the spacer  52 . 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. Construction of the catheter body  12  whereby the stiffening tube  20  and spacer  58  are under compression has been found to be advantageous to prevent the formation of gaps between the stiffening tube  20  and spacer  58  or between spacer  58  and the tip section  14  which might otherwise occur after repeated tip deflections. Such gaps are undesirable because they cause the catheter to crease or fold over, hindering the catheter&#39;s ability to roll. 
     Extending through the single lumen  18  of the catheter body  12  are lead wires  40 , an optic fiber  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 optic fiber  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 of which are undesirable performance characteristics. 
     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. 
     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 , optic fiber  46  or sensor cable  74 . A non-conductive 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 joint  29  and at its distal end to the tip section  14  at a location distal to the spacer  52  by glue joint  50 . Both glue joints  29  and  50  preferably comprise polyurethane glue or the like. The glue may be applied by means of a syringe or the like through a hole made between the outer surface of the catheter body  12  and the single lumen  18 . Such a hole may be formed, for example, by a needle or the like that punctures the wall of the catheter body  12  and the stiffening tube  20  which is heated sufficiently to form a permanent hole. The glue is then introduced through the hole to the outer surface of the compression coil  44  and wicks around the outer circumference to form a glue joint about the entire circumference of the compression coil  44 . 
     The puller wire  42  extends into the second lumen  32  of the tip section  14 . The puller wire  42  is anchored to a tip electrode  36  or to the side of the catheter tip section  14 . With reference to FIGS. 2 b  and  3 , within the tip section  14 , and distal to the glue joint  51 , the turns of the compression coil are expanded longitudinally. Such expanded turns  47  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  47  then into a plastic, preferably Teflon®, sheath  81 , which prevents the puller wire  42  from cutting into the wall of the tip section  14  when the tip section  14  is deflected. 
     The distal end of the puller wire  42  may be anchored to the tip electrode  36  by solder or the like, as shown in FIG. 2 b  or to the side wall of the tip section  14 . If attached to the side wall, an embodiment comprising an anchor  80  fixedly attached to the distal end of the puller wire  42  is preferred, as illustrated in FIGS. 9-11. In such an embodiment, the anchor is formed by a metal tube  82 , e.g., a short segment of hypodermic stock, which is fixedly attached, e.g., by crimping, to the distal end of the puller wire  42 . The tube  82  has a section which extends a short distance beyond the distal end of the puller wire  42 . A cross-piece  84  made of a small section of stainless steel ribbon or the like is soldered or welded in a transverse arrangement to the distal end of the tube  82 , which is flattened during the operation. This creates a T-bar anchor  80 . A notch  86  is created in the side of the catheter tip section  14  resulting in an opening into the second lumen  32  carrying the puller wire  42 . The anchor  80  lies within the notch  86 . Because the length of the ribbon forming the cross-piece  84  is longer than the diameter of the opening into the second lumen  32 , the anchor  80  cannot be pulled completely into the second lumen  32 . The notch  86  is then sealed with polyurethane or the like to give a smooth outer surface. 
     With reference to FIGS. 2 a  and  2   b , 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 . 
     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 separate lead wires  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 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. 2 b . Connection of a lead wire  40  to a ring electrode  38  is preferably accomplished by first making a small hole through the plastic housing  21 . Such a hole can be created, for example, by inserting a needle through the plastic housing  21  and heating the needle sufficiently to form a permanent hole. A lead wire  40  is then drawn through the hole by using a microhook or the like. The ends of the lead wire  40  are then stripped of any coating and soldered or welded to the underside of the ring electrode  38 , which is then slid into position over the hole and fixed in place with polyurethane glue or the like. 
     In a particularly preferred embodiment of the invention, a temperature sensing means is provided for the tip electrode  36  and, if desired, the ring electrode  38 . Any conventional temperature sensing means, e.g., a thermocouple or thermistor, may be used. With reference to FIG. 2 b , a preferred temperature sensing means for the tip electrode  36  comprises a thermocouple formed by an enameled wire pair. One wire of the wire pair is a copper wire  41 , e.g., a number  40  copper wire which acts not only as part of the thermocouple, but as the electrode lead. The other wire of the wire pair is a construction wire  45 , e.g., a number  40  construction wire, which gives support and strength to the wire pair. The wires  41  and  45  of the wire pair are electrically isolated from each other except at their distal ends where they contact and are welded or soldered to the tip electrode  36 . Because it is desirable to monitor the temperature of the tip electrode  36  at a site adjacent the distal end of the optic fiber  46 , the thermocouple with a blind hole in the tip electrode  36  is fixed to the tip electrode  36  at the distal end of the blind hole as shown. 
     An optic fiber  46  for transmitting laser energy to create channels in the heart tissue slidably extends through the control handle  16  and catheter body  12  and into the first lumen  30  of the tip section  14 . As used herein, “channels” refers to percutaneous myocardial channels that are formed in the heart tissue when the laser is fired. Preferred channels are approximately 1.0 millimeter in diameter and up to about 5.0 millimeters deep. 
     The distal end of the optic fiber  46  extends through an optic fiber lumen in the tip electrode  36  and is fixed to the tip electrode  36  by glue or the like. The distal end of the optic fiber  46  is flush with the distal surface of the tip electrode. A connector (not shown) at the proximal end of the optic fiber  46  can be used to connect the proximal end of the optic fiber  46  to a laser (not shown). Any suitable laser can be used. A presently preferred laser is a Shaplan Ho: YAG 2040 Laser. 
     The optic fiber  46  comprises a quartz core  48 , a cladding made of doped silica or the like and a surrounding jacket  45 . The jacket  45  can be of any suitable material, preferably aluminum, but materials such as such as nylon and polyimide may also be used. An aluminum jacket  45  is preferred as it tends to maximize the strength of the optic fiber  46  so that when the optic fiber is bent, e.g., when the catheter tip  14  is deflected, the quartz core does not break. 
     At the distal end of the optic fiber  46 , the aluminum jacket  45  is stripped from the core  48 . There are two principle reasons for this. The first is to prevent material from the aluminum jacket (or any other type of jacket) from breaking off into the heart chamber, particularly during laser transmission, which could lead to a stroke. The second is to electrically isolate the aluminum jacket  45  from the tip electrode  36 . This is a safety measure to assure that a short circuit does not occur between the jacket  45  and tip electrode  36  that could deliver a potentially lethal burst of high voltage to the patient during laser transmission. A plastic, preferably polyimide, protective tube  47  is placed in surrounding relation to the portion of the optic fiber  46  covered by the jacket  45  that is situated within the tip electrode  36 . The protective tube  47  prevents electrical contact between the jacket  45  and the tip electrode  36 . The protective tube  47  extends beyond the distal end of the aluminum jacket  45  to help support the core  48 . The protective tube  47  cannot extend too close to the distal tip of the optic fiber  46 , however, because it would melt when the laser is fired. The protective tube  47  is fixed to the tip electrode  36  by glue or the like. 
     An electromagnetic sensor  72  is contained within the distal end of the tip section  14 . The electromagnetic sensor  72  is connected by means of 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 covered 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. A suitable electromagnetic sensor is described, for example, in U.S. Pat. No. 4,391,199, which is incorporated herein by reference. A preferred electromagnetic mapping sensor  72  is manufactured by Biosense Ltd. Israel 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 DMR 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 that 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 use of the laser is appropriate. Once the presence and location of ischemic tissue has been identified, the DMR catheter can be deflected so that the optic fiber is normal, i.e., at a right angle, to the ischemic tissue, and laser energy is fired through the optic fiber in coordination with the heart activity, e.g. during systole, to create a channel in the ischemic tissue, for example, as described in U.S. Pat. Nos. 5,554,152, 5,389,096, and 5,380,316, the disclosures of which are incorporated herein by reference. This procedure is repeated to create multiple channels. 
     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, a DMR 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 Cordis 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 Cordis Webster, Inc. 
     The electrode lead wires  40 , optic fiber  46  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 are provided tunnels through the glue joint  50 , which fixes the proximal end of the compression coil  44  inside the catheter body  12 . The tunnels are formed by transfer tubes  27 , preferably made of short segments of polyimide tubing. In the embodiment shown in FIG. 3, there are two transfer tubes  27  for the glue joint  50 . Each 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. Extending through one transfer tube  27  are the lead wires  40  and the electromagnetic sensor cable  74 . Extending through the other transfer tube  27  is the optic fiber  46 . 
     An additional transfer tube  29  is located at the joint between the tip section  14  and the catheter body  12 . Extending through this transfer tube is the optic fiber  46 . This transfer tube  29  provides a tunnel through the glue joint formed when the tip section  14  is glued to the catheter body  12 . It is understood that the number of transfer tubes may vary as desired. 
     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 . 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 optic fiber  46 , puller wire  42 , lead wires  40  and electromagnetic sensor cable  74  extend through the piston  54 . The puller wire  42  is anchored to an anchor pin  36 , located proximal to the piston  54 . The lead wires  40  and electromagnetic sensor cable  74  extend though 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  16 . Wires  80  connect the circuit board  64  to a computer and imaging monitor (not shown). 
     The optic fiber  46  extends through a guide tube  66 , preferably made of polyurethane, and is afforded longitudinal movement therein. The polyurethane guide tube  66  is anchored to the piston  54 , preferably by glue at glue joint  53 . This allows the optic fiber  46  longitudinal movement within the control handle  16  so that it does not break when the piston  54  is adjusted to manipulate the puller wire  42 . Within the piston  54 , the puller wire  42  is situated within a transfer tube  27 , and the electromagnetic sensor cable  74  and lead wires  40  are situated within another transfer tube  27  to allow longitudinal movement of the wires and cable near the glue joint  53 . 
     The optic fiber  46  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 optic fiber  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 optic fiber  46  and the polyurethane guide tube  66  extend through a second larger plastic guide tube  68 , preferably made of Teflon®, which affords the guide tube  66  and optic fiber  46  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 fiber  46  both from contact with the circuit board  64  and from any sharp bends as the guide tube  66  and optic fiber  46  emerge from the control handle  16 . 
     In another preferred catheter constructed in accordance with the present invention, there is provided an infusion tube  76  for infusing fluids, including drugs such as fibroblast growth factor (FGP), vaslar endothelial growth factor (VEGP), thromboxane-A2 or protein kinase-C. These are drugs that initiate or promote angiogenesis. FGP and VEGP work directly to initiate the formation of new blood vessels Thromboxane-A2 and protein kinase-C work indirectly to form new blood vessels. They are released by blood platelets during clot formation and have specific receptor sites which release FGF and VEGF. 
     Other preferred drugs tat may be infused include those which minimize the effect of foreign body reaction and extend the potency of the created channels. Drugs such as dexamethasone in various forms, e.g., dexamethasone sodium phosphate and dexamethasone acetate, can be delivered to sites to reduce inflammation associated with trauma and foreign body reaction which lead to the formation of fibrosis and collagen capsules which, in turn, close the created channels. 
     It is apparent that other drugs may be infused as desired. Moreover, saline, or the like, may be infused for controlling the temperature of the tip electrode. The infusion tube  76  may even be used for collecting tissue or fluid samples. The infusion tube  76  may be made of any suitable material, and is preferably made of polyimide tubing. 
     With reference to FIGS. 7 and 8, there is shown a catheter  10  having an infusion tube  76 . The catheter  10  comprises a single lumen catheter body  12  as described above and a catheter tip section  14  comprising four lumens. To accommodate four lumens in the tip section, the diameter of the catheter may need to be increased slightly. The infusion tube  76  extends through the catheter body  12  and into the fourth lumen  77  of the tip section  14 . The distal end of the infusion tube  76  extends into an opening or passage through the tip electrode  36  and is fixed, e.g., by glue, to the tip electrode  36 . The passage in the tip electrode  36  may be straight or branched as desired. Alternatively, the infusion tube  76  can replace the optic fiber  46  in the first lumen  30  of the triple lumen tip section  14  in the embodiment described above. 
     The proximal end of the infusion tube  76  extends out of a sealed opening in the side wall of the catheter body and terminates in a luer hub or the like. Alternatively, the infusion tube  76  may extend through the control handle and terminate in a luer hub or the like at a location proximal to the handle. In this arrangement, fluids, including drugs to promote revascularization, may be infused into the heart at the precise location of the revascularization procedure. 
     In another embodiment, as shown in FIG. 8, a guide wire hole  78  is provided at the distal end of the tip section  14 . The guide wire hole  78  extends from the side of the tip electrode  36  to the distal end of the tip electrode at an angle of about 30° to the longitudinal axis of the tip electrode. The guide wire hole  78  allows a guide wire (not shown) to be introduced into the heart and the catheter  10  to be passed over the guide wire until it is in the proper location within the heart. Generally, to get the guide wire into the heart, an introducing sheath is passed into the heart and then the guide wire is introduced into the heart from the introducing sheath. 
     In another preferred embodiment constructed in accordance with the present invention, two or more puller wires 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. 
     As an alternative to the above described embodiment, the 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. 
     A particularly preferred catheter construction comprising multiple puller wires including control handle construction is disclosed in pending patent application entitled Omni-Directional Steerable Catheter, naming as inventor Wilton W. Webster, Jr. (attorney docket number 29963) filed concurrently herewith and incorporated hereby by reference. Such application describes a suitable control handle for manipulating two or more puller wires. The described control handle includes a central passage that may be expanded to accommodate the electrode lead wires, electromagnetic sensor cable, optic fiber and even infusion tube. Further, an extension of the handle may be provided to house the circuit bound for the electromagnetic sensor, e.g., in the same manner as shown in FIG. 4 herein. 
     The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. 
     Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.