Abstract:
Embodiments described herein relate to methods of using a catheter having a braided conductive member. One embodiment relates to a method for treating a condition of a patient that involves contacting an exterior wall of a blood vessel with the braided conductive member. Another embodiment relates to a method that involves contacting a wall of a blood vessel with the braided conductive member and controlling energy delivery to the braided conductive member based on at least one sensed temperature.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is a continuation of U.S. application Ser. No. 11/978,066, filed Oct. 26, 2007; which is a divisional of U.S. application Ser. No. 10/939,630, filed Sep. 13, 2004, now U.S. Pat. No. 7,306,594; which is a divisional of U.S. application Ser. No. 09/845,022, filed Apr. 27, 2001, now U.S. Pat. No. 6,837,886; all of which are entitled APPARATUS AND METHODS FOR MAPPING AND ABLATION IN ELECTROPHYSIOLOGY PROCEDURES, all of which are hereby incorporated herein by reference in their entirety, and which, in turn, claim the benefit of U.S. Provisional Application Ser. No. 60/261,015 entitled HIGH DENSITY MAPPING AND ABLATION CATHETER AND METHOD OF USE, filed Jan. 11, 2001; U.S. Provisional Application Ser. No. 60/204,457 entitled METHOD FOR CREATING ANNULAR EPICARDIAL LESIONS AT THE OSTIA OF THE PULMONARY VEINS, filed on May 16, 2000; U.S. Provisional Application Ser. No. 60/204,482 entitled METHOD AND DEVICE FOR CREATING ANNULAR ENDOCARDIAL LESIONS AT THE OSTIA OF THE PULMONARY VEINS, filed May 16, 2000; and U.S. Provisional Application Ser. No. 60/201,445 entitled TRANSMURAL CIRCUMFERENTIAL LESIONS MADE AT CANINE PV OSTIUM BY EXPANDABLE MESH ELECTRODES IN VIVO, filed May 3, 2000, all of which are also hereby incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The human heart is a very complex organ, which relies on both muscle contraction and electrical impulses to function properly. The electrical impulses travel through the heart walls, first through the atria and then the ventricles, causing the corresponding muscle tissue in the atria and ventricles to contract. Thus, the atria contract first, followed by the ventricles. This order is essential for proper functioning of the heart. 
         [0003]    Over time, the electrical impulses traveling through the heart can begin to travel in improper directions, thereby causing the heart chambers to contract at improper times. Such a condition is generally termed a cardiac arrhythmia, and can take many different forms. When the chambers contract at improper times, the amount of blood pumped by the heart decreases, which can result in premature death of the person. 
         [0004]    Techniques have been developed which are used to locate cardiac regions responsible for the cardiac arrhythmia, and also to disable the short-circuit function of these areas. According to these techniques, electrical energy is applied to a portion of the heart tissue to ablate that tissue and produce scars which interrupt the reentrant conduction pathways or terminate the focal initiation. The regions to be ablated are usually first determined by endocardial mapping techniques. Mapping typically involves percutaneously introducing a catheter having one or more electrodes into the patient, passing the catheter through a blood vessel (e.g. the femoral vein or artery) and into an endocardial site (e.g., the atrium or ventricle of the heart), and deliberately inducing an arrhythmia so that a continuous, simultaneous recording can be made with a multichannel recorder at each of several different endocardial positions. When an arrythormogenic focus or inappropriate circuit is located, as indicated in the electrocardiogram recording, it is marked by various imaging or localization means so that cardiac arrhythmias emanating from that region can be blocked by ablating tissue. An ablation catheter with one or more electrodes can then transmit electrical energy to the tissue adjacent the electrode to create a lesion in the tissue. One or more suitably positioned lesions will typically create a region of necrotic tissue which serves to disable the propagation of the errant impulse caused by the arrythromogenic focus. Ablation is carried out by applying energy to the catheter electrodes. The ablation energy can be, for example, RF, DC, ultrasound, microwave, or laser radiation. 
         [0005]    Atrial fibrillation together with atrial flutter are the most common sustained arrhythmias found in clinical practice. 
         [0006]    Current understanding is that atrial fibrillation is frequently initiated by a focal trigger from the orifice of or within one of the pulmonary veins. Though mapping and ablation of these triggers appears to be curative in patients with paroxysmal atrial fibrillation, there are a number of limitations to ablating focal triggers via mapping and ablating the earliest site of activation with a “point” radiofrequency lesion. One way to circumvent these limitations is to determine precisely the point of earliest activation. Once the point of earliest activation is identified, a lesion can be generated to electrically isolate the trigger with a lesion; firing from within those veins would then be eliminated or unable to reach the body of the atrium, and thus could not trigger atrial fibrillation. 
         [0007]    Another method to treat focal arrhythmias is to create a continuous, annular lesion around the ostia (i.e., the openings) of either the veins or the arteries leading to or from the atria thus “corralling” the signals emanating from any points distal to the annular lesion. Conventional techniques include applying multiple point sources around the ostia in an effort to create such a continuous lesion. Such a technique is relatively involved, and requires significant skill and attention from the clinician performing the procedures. 
         [0008]    Another source of arrhythmias may be from reentrant circuits in the myocardium itself. Such circuits may not necessarily be associated with vessel ostia, but may be interrupted by means of ablating tissue either within the circuit or circumscribing the region of the circuit. It should be noted that a complete ‘fence’ around a circuit or tissue region is not always required in order to block the propagation of the arrhythmia; in many cases simply increasing the propagation path length for a signal may be sufficient. Conventional means for establishing such lesion ‘fences’ include a multiplicity of point-by-point lesions, dragging a single electrode across tissue while delivering energy, or creating an enormous lesion intended to inactivate a substantive volume of myocardial tissue. 
         [0009]    Commonly-owned U.S. patent application Ser. No. 09/396,502, entitled Apparatus For Creating A Continuous Annular Lesion, which is hereby incorporated by reference, discloses a medical device which is capable of ablating a continuous ring of tissue around the ostia of either veins or arteries leading to or from the atria. 
       SUMMARY OF THE INVENTION 
       [0010]    The present invention encompasses apparatus and methods for mapping electrical activity within the heart. The present invention also encompasses methods and apparatus for creating lesions in the heart tissue (ablating) to create a region of necrotic tissue which serves to disable the propagation of errant electrical impulses caused by an arrhythmia. 
         [0011]    In one embodiment, the present invention includes a medical device including a catheter having a braided conductive member at a distal end thereof, a mechanism for expanding the braided conductive member from an undeployed to a deployed position, and a mechanism for applying energy via the braided conductive member to blood vessel. 
         [0012]    In one embodiment, the medical device further includes a mechanism for irrigating the braided conductive member. 
         [0013]    In another embodiment, the medical device further includes at least one reference electrode disposed on a shaft of the catheter. 
         [0014]    In another embodiment, the medical device includes a mechanism for controlling the energy supplied to the braided conductive member. 
         [0015]    In another embodiment, the medical device further includes a mechanism for covering at least a portion of the braided conductive member when the braided conductive member is in the deployed position. 
         [0016]    In another embodiment, at least a portion of the braided conductive member has a coating applied thereto. 
         [0017]    In another embodiment, the medical device includes a mechanism for measuring temperature. 
         [0018]    In another embodiment, the medical device includes a mechanism for steering the catheter. 
         [0019]    The invention also includes a method for treating cardiac arrhythmia, including the steps of introducing a catheter having a braided conductive member at a distal end thereof into a blood vessel, expanding the braided conductive member at a selected location in the blood vessel so that the braided conductive member contacts a wall of the blood vessel, and applying energy to the wall of the blood vessel via the braided conductive member to create a lesion in the blood vessel. 
         [0020]    In another embodiment, the invention includes a method for treating cardiac arrhythmia, including the steps of introducing a catheter into a thoracic cavity of a patient, the catheter having a braided conductive member at a distal end thereof, contacting an exterior wall of a blood vessel in a vicinity of an ostium with the braided conductive member, and applying energy to the blood vessel via the braided conductive member to create a lesion on the exterior wall of the blood vessel. 
         [0021]    Another embodiment described herein relates to a method for treating a condition of a patient. The method comprises acts of introducing a portion of a catheter into a patient, the catheter having a braided conductive member at a distal end thereof, contacting an exterior wall of a blood vessel with the braided conductive member, and applying energy to the exterior wall via the braided conductive member to treat the condition. 
         [0022]    A further embodiment described herein relates to a method comprising an act of introducing a portion of a catheter into a patient, the catheter having a braided conductive member at a distal end thereof. The braided conductive member comprises a plurality of filaments. The method also comprises acts of contacting a wall of a blood vessel with the braided conductive member and energizing at least some of the plurality of filaments to apply energy to the wall via the braided conductive member. The method further comprises acts of sensing, during the act of energizing, at least one temperature using at least one temperature sensor coupled to the braided conductive member; and controlling energy delivery to the braided conductive member based on the at least one sensed temperature. 
         [0023]    The braided conductive member may be a wire mesh. 
         [0024]    The features and advantages of the present invention will be more readily understood and apparent from the following detailed description of the invention, which should be read in conjunction with the accompanying drawings, and from the claims which are appended at the end of the Detailed Description. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    In the drawings, which are incorporated herein by reference and in which like elements have been given like references characters, 
           [0026]      FIG. 1  illustrates an overview of a mapping and ablation catheter system in accordance with the present invention; 
           [0027]      FIGS. 2 and 3  illustrate further details of the catheter illustrated in  FIG. 1 ; 
           [0028]      FIGS. 4-7  illustrate further details of the braided conductive member illustrated in  FIGS. 2 and 3 ; 
           [0029]      FIGS. 8-10A  illustrate, among other things, temperature sensing in the present invention; 
           [0030]      FIGS. 11-13  illustrate further details of the steering capabilities of the present invention; 
           [0031]      FIGS. 14-17  illustrate further embodiments of the braided conductive member; 
           [0032]      FIGS. 18-19  illustrate the use of irrigation in connection with the present invention; 
           [0033]      FIGS. 20A-20E  illustrate the use of shrouds in the present invention; 
           [0034]      FIG. 21  illustrates a guiding sheath that may be used in connection with the present invention; 
           [0035]      FIGS. 22-24  illustrate methods of using the present invention. 
       
    
    
     DETAILED DESCRIPTION 
     System Overview 
       [0036]    Reference is now made to  FIG. 1 , which figure illustrates an overview of a mapping and ablation catheter system in accordance with the present invention. The system includes a catheter  10  having a shaft portion  12 , a control handle  14 , and a connector portion  16 . A controller  8  is connected to connector portion  16  via cable  6 . Ablation energy generator  4  may be connected to controller  8  via cable  3 . A recording device  2  may be connected to controller  8  via cable  1 . When used in an ablation application, controller  8  is used to control ablation energy provided by ablation energy generator  4  to catheter  10 . When used in a mapping application, controller  8  is used to process signals coming from catheter  10  and to provide these signals to recording device  2 . Although illustrated as separate devices, recording device  2 , ablation energy generator  4 , and controller  8  could be incorporated into a single device. In one embodiment, controller  8  may be a QUADRAPULSE RF CONTROLLER™ device available from CR Bard, Inc., Murray Hill, N.J. 
         [0037]    In this description, various aspects and features of the present invention will be described. The various features of the invention are discussed separately for clarity. One skilled in the art will appreciate that the features may be selectively combined in a device depending upon the particular application. Furthermore, any of the various features may be incorporated in a catheter and associated method of use for either mapping or ablation procedures. 
       Catheter Overview 
       [0038]    Reference is now made to  FIGS. 2-7 , which figures illustrate one embodiment of the present invention. The present invention generally includes a catheter and method of its use for mapping and ablation in electrophysiology procedures. Catheter  10  includes a shaft portion  12 , a control handle  14 , and a connector portion  16 . When used in mapping applications, connector portion  16  is used to allow signal wires running from the electrodes at the distal portion of the catheter to be connected to a device for processing the electrical signals, such as a recording device. 
         [0039]    Catheter  10  may be a steerable device.  FIG. 2  illustrates the distal tip portion  18  being deflected by the mechanism contained within control handle  14 . Control handle  14  may include a rotatable thumb wheel which can be used by a user to deflect the distal end of the catheter. The thumb wheel (or any other suitable actuating device) is connected to one or more pull wires which extend through shaft portion  12  and are connected to the distal end  18  of the catheter at an off-axis location, whereby tension applied to one or more of the pull wires causes the distal portion of the catheter to curve in a predetermined direction or directions. U.S. Pat. Nos. 5,383,852, 5,462,527, and 5,611,777, which are hereby incorporated by reference, illustrate various embodiments of control handle  14  that may be used for steering catheter  10 . 
         [0040]    Shaft portion  12  includes a distal tip portion  18 , a first stop  20  and an inner member  22  connected to the first stop portion  20 . Inner member  22  may be a tubular member. Concentrically disposed about inner member  22  is a first sheath  24  and a second sheath  26 . Also concentrically disposed about inner member  22  is a braided conductive member  28  anchored at respective ends  30  and  32  to the first sheath  24  and the second sheath  26 , respectively. 
         [0041]    In operation, advancing the second sheath  26  distally over inner member  22  causes the first sheath  24  to contact stop  20 . Further distal advancement of the second sheath  26  over inner member  22  causes the braided conductive member  28  to expand radially to assume various diameters and/or a conical shape.  FIG. 3  illustrates braided conductive member  28  in an unexpanded (collapsed or “undeployed”) configuration.  FIGS. 2 and 4  illustrate braided conductive member  28  in a partially expanded condition.  FIG. 1  illustrates braided conductive member  28  radially expanded (“deployed”) to form a disk. 
         [0042]    Alternatively, braided conductive member  28  can be radially expanded by moving inner member  22  proximally with respect to the second sheath  26 . 
         [0043]    As another alternative, inner member  22  and distal tip portion  18  may be the same shaft and stop  20  may be removed. In this configuration, sheath  24  moves over the shaft in response to, for example, a mandrel inside shaft  22  and attached to sheath  24  in the manner described, for example, in U.S. Pat. No. 6,178,354, which is incorporated herein by reference. 
         [0044]    As illustrated particularly in  FIGS. 4 and 5  a third sheath  32  may be provided. The third sheath serves to protect shaft portion  12  and in particular braided conductive member  28  during manipulation through the patient&#39;s vasculature. In addition, the third sheath  32  shields braided conductive member  28  from the patient&#39;s tissue in the event ablation energy is prematurely delivered to the braided conductive member  28 . 
         [0045]    The respective sheaths  24 ,  26 , and  32  can be advanced and retracted over the inner member  22 , which may be a tubular member, in many different manners. Control handle  14  may be used. U.S. Pat. Nos. 5,383,852, 5,462,527, and 5,611,777 illustrate examples of control handles that can control sheaths  24 ,  26 , and  32 . As described in these incorporated by reference patents, control handle  14  may include a slide actuator which is axially displaceable relative to the handle. The slide actuator may be connected to one of the sheaths, for example, the second sheath  26  to control the movement of the sheath  26  relative to inner member  22 , to drive braided conductive member  28  between respective collapsed and deployed positions, as previously described. Control handle  14  may also include a second slide actuator or other mechanism coupled to the retractable outer sheath  32  to selectively retract the sheath in a proximal direction with respect to the inner member  22 . 
         [0046]    Braided conductive member  28  is, in one embodiment of the invention, a plurality of interlaced, electrically conductive filaments  34 . Braided conductive member  28  may be a wire mesh. The filaments are flexible and capable of being expanded radially outwardly from inner member  22 . The filaments  34  are preferably formed of metallic elements having relatively small cross sectional diameters, such that the filaments can be expanded radially outwardly. The filaments may be round, having a dimension on the order of about 0.001-0.030 inches in diameter. Alternatively, the filaments may be flat, having a thickness on the order of about 0.001-0.030 inches, and a width on the order of about 0.001-0.030 inches. The filaments may be formed of Nitinol type wire. Alternatively, the filaments may include non metallic elements woven with metallic elements, with the non metallic elements providing support to or separation of the metallic elements. A multiplicity of individual filaments  34  may be provided in braided conductive member  28 , for example up to 300 or more filaments. 
         [0047]    Each of the filaments  34  can be electrically isolated from each other by an insulation coating. This insulation coating may be, for example, a polyamide type material. A portion of the insulation on the outer circumferential surface  60  of braided conductive member  28  is removed. This allows each of the filaments  34  to form an isolated electrode, not an electrical contact with any other filament, that may be used for mapping and ablation. Alternatively, specific filaments may be permitted to contact each other to form a preselected grouping. 
         [0048]    Each of the filaments  34  is helically wound under compression about inner member  22 . As a result of this helical construction, upon radial expansion of braided conductive member  28 , the portions of filaments  34  that have had the insulation stripped away do not contact adjacent filaments and thus, each filament  34  remains electrically isolated from every other filament.  FIG. 6 , in particular, illustrates how the insulation may be removed from individual filaments  34  while still providing isolation between and among the filaments. As illustrated in  FIG. 6 , regions  50  illustrate regions, on the outer circumferential surface  60  of braided conductive member  28 , where the insulation has been removed from individual filaments  34 . In one embodiment of the invention, the insulation may be removed from up to one half of the outer facing circumference of each of the individual filaments  34  while still retaining electrical isolation between each of the filaments  34 . 
         [0049]    The insulation on each of the filaments  34  that comprise braided conductive member  28  may be removed about the outer circumferential surface  60  of braided conductive member  28  in various ways. For example, one or more circumferential bands may be created along the length of braided conductive member  28 . Alternatively, individual sectors or quadrants only may have their insulation removed about the circumference of braided conductive member  28 . Alternatively, only selected filaments  34  within braided conductive member  28  may have their circumferentially facing insulation removed. Thus, an almost limitless number of configurations of insulation removal about the outer circumferential surface  60  of braided conductive member  28  can be provided depending upon the mapping and ablation characteristics and techniques that a clinician desires. 
         [0050]    The insulation on each of the filaments  34  may be removed at the outer circumferential surface  60  of braided conductive member  28  in a variety of ways as long as the insulation is maintained between filaments  34  so that filaments  34  remain electrically isolated from each other. 
         [0051]    The insulation can be removed from the filaments  34  in a variety of ways to create the stripped portions  50  on braided conductive member  28 . For example, mechanical means such as abration or scraping may be used. In addition, a water jet, chemical means, or thermal radiation means may be used to remove the insulation. 
         [0052]    In one example of insulation removal, braided conductive member  28  may be rotated about inner member  22 , and a thermal radiation source such as a laser may be used to direct radiation at a particular point along the length of braided conductive member  28 . As the braided conductive member  28  is rotated and the thermal radiation source generates heat, the insulation is burned off the particular region. 
         [0053]    Insulation removal may also be accomplished by masking selected portions of braided conductive member  28 . A mask, such as a metal tube may be placed over braided conducive member  28 . Alternatively, braided conductive member  28  may be wrapped in foil or covered with some type of photoresist. The mask is then removed in the areas in which insulation removal is desired by, for example, cutting away the mask, slicing the foil, or removing the photoresist. Alternatively, a mask can be provided that has a predetermined insulation removal pattern. For example, a metal tube having cutouts that, when the metal tube is placed over braided conductive member  28 , exposes areas where insulation is to be removed. 
         [0054]      FIG. 6  illustrates how thermal radiation  52  may be applied to the outer circumferential surface  56  of a respective filament  34  that defines the outer circumferential surface  60  of braided conductive member  28 . As thermal radiation  52  is applied, the insulation  54  is burned off or removed from the outer circumference  56  of wire  34  to create a region  58  about the circumference  56  of filament  34  that has no insulation. 
         [0055]    The insulation  54  can also be removed in a preferential manner so that a particular portion of the circumferential surface  56  of a filament  34  is exposed. Thus, when braided conductive member  28  is radially expanded, the stripped portions of filaments may preferentially face the intended direction of mapping or ablation. 
         [0056]    With the insulation removed from the portions of filaments  34  on the outer circumferential surface  60  of braided conductive member  28 , a plurality of individual mapping and ablation channels can be created. A wire runs from each of the filaments  34  within catheter shaft  12  and control handle  14  to connector portion  16 . A multiplexer or switch box may be connected to the conductors so that each filament  34  may be controlled individually. This function may be incorporated into controller  8 . A number of filaments  34  may be grouped together for mapping and ablation. Alternatively, each individual filament  34  can be used as a separate mapping channel for mapping individual electrical activity within a blood vessel at a single point. Using a switch box or multiplexer to configure the signals being received by filaments  34  or ablation energy sent to filaments  34  results in an infinite number of possible combinations of filaments for detecting electrical activity during mapping procedures and for applying energy during an ablation procedure. 
         [0057]    By controlling the amount of insulation that is removed from the filaments  34  that comprise braided conductive member  28 , the surface area of the braid that is in contact with a blood vessel wall can also be controlled. This in turn will allow control of the impedance presented to an ablation energy generator, for example, generator  4 . In addition, selectively removing the insulation can provide a predetermined or controllable profile of the ablation energy delivered to the tissue. 
         [0058]    The above description illustrates how insulation may be removed from a filaments  34 . Alternatively, the same features and advantages can be achieved by adding insulation to filaments  34 . For example, filaments  34  may be bare wire and insulation can be added to them. 
         [0059]    Individual control of the electrical signals received from filaments  34  allows catheter  10  to be used for bipolar (differential or between filament) type mapping as well as unipolar (one filament with respect to a reference) type mapping. 
         [0060]    Catheter  10  may also have, as illustrated in  FIGS. 2 and 3 , a reference electrode  13  mounted on shaft  12  so that reference electrode  13  is located outside the heart during unipolar mapping operations. 
         [0061]    Radiopaque markers can also be provided for use in electrode orientation and identification. 
         [0062]    One skilled in the art will appreciate all of the insulation can be removed from filaments  34  to create a large ablation electrode. 
         [0063]    Although a complete catheter steerable structure has been illustrated, the invention can also be adapted so that inner tubular member  22  is a catheter shaft, guide wire, or a hollow tubular structure for introduction of saline, contrast media, heparin or other medicines, or introduction of guidewires, or the like. 
       Temperature Sensing 
       [0064]    A temperature sensor or sensors, such as, but not limited to, one or more thermocouples may be attached to braided conductive member  28  for temperature sensing during ablation procedures. A plurality of thermocouples may also be woven into the braided conductive member  28 . An individual temperature sensor could be provided for each of the filaments  34  that comprise braided conductive member  28 . Alternatively, braided conductive member  28  can be constructed of one or more temperature sensors themselves. 
         [0065]      FIG. 8  illustrates braided conductive member  28  in its fully expanded or deployed configuration. Braided conductive member  28  forms a disk when fully expanded. In the embodiment illustrated in  FIG. 8 , there are sixteen filaments  34  that make up braided conductive member  28 . 
         [0066]    Temperature monitoring or control can be incorporated into braided conductive member  28 , for example, by placing temperature sensors (such as thermocouples, thermistors, etc.) on the expanded braided conductive member  28  such that they are located on the distally facing ablative ring formed when braided conductive member  28  is in its fully expanded configuration. “Temperature monitoring” refers to temperature reporting and display for physician interaction. “Temperature control” refers to the capability of adding an algorithm in a feedback loop to titrate power based on temperature readings from the temperature sensors disposed on braided conductive member  28 . Temperature sensors can provide a means of temperature control provided the segment of the ablative ring associated with each sensor is independently controllable (e.g., electrically isolated from other regions of the mesh). For example, control can be achieved by dividing the ablative structure into electrically independent sectors, each with a temperature sensor, or alternatively, each with a mechanism to measure impedance in order to facilitate power titration. The ablative structure may be divided into electrically independent sectors so as to provide zone control. The provision of such sectors can be used to provide power control to various sections of braided conductive member  28 . 
         [0067]    As illustrated in  FIG. 8 , four temperature sensors  70  are provided on braided conductive member  28 . As noted previously, since the individual filaments  34  in braided conductive member  28  are insulated from each other, a number of independent sectors may be provided. A sector may include one or more filaments  34 . During ablation procedures, energy can be applied to one or more of the filaments  34  in any combination desired depending upon the goals of the ablation procedure. A temperature sensor could be provided on each filament  34  of braided conductive member  28  or shared among one or more filaments. In mapping applications, one or more of the filaments  34  can be grouped together for purposes of measuring electrical activity. These sectoring functions can be provided in controller  8 . 
         [0068]      FIG. 10  illustrates a side view of braided conductive member  28  including temperature sensors  70 . As shown in  FIG. 10 , temperature sensors  70  emerge from four holes  72 . Each hole  72  is disposed in one quadrant of anchor  74 . The temperature sensors  70  are bonded to the outside edge  76  of braided conductive member  28 . Temperature sensors  70  may be isolated by a small piece of polyimide tubing  73  around them and then bonded in place to the filaments. The temperature sensors  7  may be woven and twisted into braided conductive member  28  or they can be bonded on a side-by-side or parallel manner with the filaments  34 . 
         [0069]    There are several methods of implementing electrically independent sectors. In one embodiment, the wires are preferably stripped of their insulative coating in the region forming the ablative ring (when expanded). However, sufficient insulation may be left on the wires in order to prevent interconnection when in the expanded state. Alternatively, adjacent mesh wires can be permitted to touch in their stripped region, but can be separated into groups by fully insulated (unstripped) wires imposed, for example, every 3 or 5 wires apart (the number of wires does not limit this invention), thus forming sectors of independently controllable zones. Each zone can have its own temperature sensor. The wires can be “bundled” (or independently attached) to independent outputs of an ablation energy generator. RF energy can then be titrated in its application to each zone by switching power on and off (and applying power to other zones during the ‘off period’) or by modulating voltage or current to the zone (in the case of independent controllers). In either case, the temperature inputs from the temperature sensors can be used in a standard feedback algorithm to control the power delivery. 
         [0070]    Alternatively, as illustrated in  FIG. 10A , braided conductive member  28  may be used to support a ribbon-like structure which is separated into discrete sectors. As shown in  FIG. 10A , the ribbon-like structure  81  may be, for example, a pleated copper flat wire that, as braided conductive member  28  expands, unfolds into an annular ring. Each of the wires  83   a - 83   d  lie in the same plane. Although four wires are illustrated in  FIG. 10A , structure  81  may include any number of wires depending upon the application and desired performance. Each of wires  83   a - 83   d  is insulated. Insulation may then be removed from each wire to create different sectors  85   a - 85   d.  Alternatively, each of wires  83   a - 83   d  may be uninsulated and insulation may be added to create different sectors. The different sectors provide an ablative zone comprised of independently controllable wires  83   a - 83   d.  Temperature sensors  70  may be mounted on the individual wires, and filaments  34  may be connected to respective wires  83   a - 83   d  to provide independent control of energy to each individual sector. One skilled in the art will appreciate that each of wires  83   a - 83   d  can have multiple sectors formed by removing insulation in various locations and that numerous combinations of sectors  85   a - 85   d  and wires  83   a - 83   d  forming ribbon-like structure  81  can be obtained. 
       Steering 
       [0071]    Reference is now made to  FIGS. 11-13  which illustrate aspects of the steering capabilities of the present invention. As illustrated in  FIGS. 1-2 , catheter  10  is capable of being steered using control handle  14 . In particular,  FIG. 1  illustrates steering where the steering pivot or knuckle is disposed on catheter shaft  12  in a region that is distal to the braided conductive member  28 . 
         [0072]      FIG. 11  illustrates catheter  10  wherein the pivot point or steering knuckle is disposed proximal to braided conductive member  28 . 
         [0073]      FIG. 12  illustrates catheter  10  having the capability of providing steering knuckles both proximal and distal to braided conductive member  28 . 
         [0074]      FIGS. 1-2 , and  11 - 12  illustrate two dimensional or single plane type steering. The catheter of the present invention can also be used in connection with a three dimensional steering mechanism. For example, using the control handle in the incorporated by reference &#39;852 patent, the catheter can be manipulated into a three-dimensional “lasso-like” shape, particularly at the distal end of the catheter. As shown in  FIG. 13 , the catheter can have a primary curve  80  in one plane and then a second curve  82  in another plane at an angle to the first plane. With this configuration, the catheter can provide increased access to difficult to reach anatomical structures. For example, a target site for a mapping or ablation operation may be internal to a blood vessel. Thus, the increased steering capability can allow easier access into the target blood vessel. In addition, the additional dimension of steering can allow for better placement of braided conductive member  28  during an ablation or mapping procedure. Catheter  10  can be inserted into a site using the steering capabilities provided by primary curve  80 . Thereafter, using the secondary curve  82 , braided conductive member  28  can be tilted into another plane for better orientation or contact with the target site. 
       Conductive Member Configurations and Materials 
       [0075]    Reference is now made to  FIGS. 14-17  which figures illustrate other configurations of braided conductive member  28 . As has been described above and will be described in more detail, braided conductive member  28  can include from one to 300 or more filaments. The filaments may vary from very fine wires having small diameters or cross-sectional areas to large wires having relatively large diameters or cross-sectional areas. 
         [0076]      FIG. 14  illustrates the use of more than one braided conductive member  28  as the distal end of catheter  10 . As shown in  FIG. 14 , three braided conductive members  28 A,  28 B, and  28 C are provided at the distal end of catheter  10 . Braided conductive members  28 A,  28 B, and  29 C may be, in their expanded conditions, the same size or different sizes. Each of the braided conductive members  28 A,  28 B, and  28 C can be expanded or contracted independently in the manner illustrated in  FIGS. 1-4  via independent control shafts  26 A,  26 B, and  26 C. The use of multiple braided conductive members provides several advantages. Rather than having to estimate or guess as to the size of the blood vessel prior to starting a mapping or ablation procedure, if braided conductive members  28 A,  28 B, and  28 C are of different expanded diameters, than sizing can be done in vivo during a procedure. In addition, one of the braided conductive members can be used for ablation and another of the braided conductive members can be used for mapping. This allows for quickly checking the effectiveness of an ablation procedure. 
         [0077]    Reference is now made to  FIGS. 15A and 15B , which figures illustrate other shapes of braided conductive member  28 . As described up to this point, braided conductive member  28  is generally symmetrical and coaxial with respect to catheter shaft  12 . However, certain anatomical structures may have complex three-dimensional shapes that are not easily approximated by a geometrically symmetrical mapping or ablation structure. One example of this type of structure occurs at the CS ostium. To successfully contact these types of anatomical structures, braided conductive member  28  can be “preformed” to a close approximation of that anatomy, and yet still be flexible enough to adapt to variations found in specific patients. Alternatively, braided conductive member  28  can be “preformed” to a close approximation of that anatomy, and be of sufficient strength (as by choice of materials, configuration, etc.) to force the tissue to conform to variations found in specific patients. For example  FIG. 15A  illustrates braided conductive member  28  disposed about shaft  12  in an off-center or non concentric manner. In addition, braided conductive member  28  may also be constructed so that the parameter of the braided conductive member in its expanded configuration has a non-circular edge so as to improve tissue contact around the parameter of the braided conductive member.  FIG. 15B  illustrates an example of this type of configuration where the braided conductive member  28  is both off center or non concentric with respect to catheter shaft  12  and also, in its deployed or expanded configuration, has an asymmetric shape. The eccentricity of braided conductive member  28  with respect to the shaft and the asymmetric deployed configurations can be produced by providing additional structural supports in braided conductive member  28 , for example, such as by adding nitinol, ribbon wire, and so on. In addition, varying the winding pitch or individual filament size or placement or deforming selective filaments in braided conductive member  28  or any other means known to those skilled in the art may be used. 
         [0078]      FIGS. 16A-16C  illustrate another configuration of braided conductive member  28  and catheter  10 . As illustrated in  FIGS. 16A-16C , the distal tip section of catheter  10  has been removed and braided conductive member  28  is disposed at the distal end of catheter  10 . One end of braided conductive member  28  is anchored to catheter shaft  12  using an anchor band  90  that clamps the end  32  of braided conductive member  28  to catheter shaft  12 . The other end of braided conductive member  28  is clamped to an activating shaft such as shaft  22  using another anchor band  92 .  FIG. 16A  illustrates braided conductive member  28  in its undeployed configuration. As shaft  22  is moved distally, braided conductive member  28  emerges or everts from shaft  12 . As shown in  FIG. 16B , braided conductive member  28  has reached its fully deployed diameter and an annular tissue contact zone  29  can be placed against an ostium or other anatomical structure. As illustrated in  FIG. 16C , further distal movement of shaft  22  can be used to create a concentric locating region  94  that can help to provide for concentric placement within an ostium of a pulmonary vein, for example. Concentric locating region  94  may be formed by selective variations in the winding density of filaments  34  in braided conductive member  28 , preferential predeformation of the filaments, additional eversion of braided conductive member  28  from shaft  12 , or by other means known to those skilled in the art. 
         [0079]    Reference is now made to  FIG. 17 , which figure illustrates a further embodiment of braided conductive member  28 . As illustrated in  FIG. 17 , braided conductive member  28  is composed of one or several large wires  96  rather than a multiplicity of smaller diameter wires. The wire or wires can be moved between the expanded and unexpanded positions in the same manner as illustrated in  FIG. 1 . In addition, a region  98  may be provided in which the insulation has been removed for mapping or ablation procedures. The single wire or “corkscrew” configuration provides several advantages. First, the wire or wires do not cross each other and therefore there is only a single winding direction required for manufacture. In addition, the risk of thrombogenicity may be reduced because there is a smaller area of the blood vessel being blocked. In addition, the connections between the ends of the large wire and the control shafts may be simplified. 
         [0080]    The catheter  10  of the present invention can be coated with a number of coatings that can enhance the operating properties of braided conductive member  28 . The coatings can be applied by any of a number of techniques and the coatings may include a wide range of polymers and other materials. 
         [0081]    Braided conductive member  28  can be coated to reduce its coefficient of friction, thus reducing the possibility of thrombi adhesion to the braided conductive member as well as the possibility of vascular or atrial damage. These coatings can be combined with the insulation on the filaments that make up braided conductive member  28 , these coatings can be included in the insulation itself, or the coatings can be applied on top of the insulation. Examples of coating materials that can be used to improve the lubricity of the catheter include PD slick available from Phelps Dodge Corporation, Ag, Tin, BN. These materials can be applied by an ion beam assisted deposition (“IBAD”) technique developed by, for example, Amp Corporation. 
         [0082]    Braided conductive member  28  can also be coated to increase or decrease its thermal conduction which can improve the safety or efficacy of the braided conductive member  28 . This may be achieved by incorporating thermally conductive elements into the electrical insulation of the filaments that make up braided conductive member  28  or as an added coating to the assembly. Alternatively, thermally insulating elements may be incorporated into the electrical insulation of the filaments that make up braided conductive member  28  or added as a coating to the assembly. Polymer mixing, IBAD, or similar technology could be used to add Ag, Pt, Pd, Au, Ir, Cobalt, and others into the insulation or to coat braided conductive member  28 . 
         [0083]    Radioopaque coatings or markers can also be used to provide a reference point for orientation of braided conductive member  28  when viewed during fluoroscopic imaging. The materials that provide radiopacity including, for example, Au, Pt, Ir, and other known to those skilled in the art. These materials may be incorporated and used as coatings as described above. 
         [0084]    Antithrombogenic coatings, such as heparin and BH, can also be applied to braided conductive member  28  to reduce thrombogenicity to prevent blood aggregation on braided conductive member  28 . These coatings can be applied by dipping or spraying, for example. 
         [0085]    As noted above, the filament  34  of braided conductive member  28  may be constructed of metal wire materials. These materials may be, for example, MP35N, nitinol, or stainless steel. Filaments  34  may also be composites of these materials in combination with a core of another material such as silver or platinum. The combination of a highly conductive electrical core material with another material forming the shell of the wire allows the mechanical properties of the shell material to be combined with the electrical conductivity of the core material to achieve better and/or selectable performance. The choice and percentage of core material used in combination with the choice and percentage of shell material used can be selected based on the desired performance characteristics and mechanical/electrical properties desired for a particular application. 
       Irrigation 
       [0086]    It is known that for a given electrode side and tissue contact area, the size of a lesion created by radiofrequency (RF) energy is a function of the RF power level and the exposure time. At higher powers, however, the exposure time can be limited by an increase in impedance that occurs when the temperature at the electrode-tissue interface approaches a 100° C. One way of maintaining the temperature less than or equal to this limit is to irrigate the ablation electrode with saline to provide convective cooling so as to control the electrode-tissue interface temperature and thereby prevent an increase in impedance. Accordingly, irrigation of braided conductive member  28  and the tissue site at which a lesion is to be created can be provided in the present invention.  FIG. 18  illustrates the use of an irrigation manifold within braided conductive member  28 . An irrigation manifold  100  is disposed along shaft  22  inside braided conductive member  28 . Irrigation manifold  100  may be one or more polyimid tubes. Within braided conductive member  28 , the irrigation manifold splits into a number of smaller tubes  102  that are woven into braided conductive member  28  along a respective filament  34 . A series of holes  104  may be provided in each of the tubes  102 . These holes can be oriented in any number of ways to target a specific site or portion of braided conductive member  28  for irrigation. Irrigation manifold  100  runs through catheter shaft  12  and may be connected to an irrigation delivery device outside the patient used to inject an irrigation fluid, such as saline, for example, such as during an ablation procedure. 
         [0087]    The irrigation system can also be used to deliver a contrast fluid for verifying location or changes in vessel diameter. For example, a contrast medium may be perfused prior to ablation and then after an ablation procedure to verify that there have been no changes in the blood vessel diameter. The contrast medium can also be used during mapping procedures to verify placement of braided conductive member  28 . In either ablation or mapping procedures, antithrombogenic fluids, such as heparin can also be perfused to reduce thrombogenicity. 
         [0088]      FIG. 19  illustrates another way of providing perfusion/irrigation in catheter  10 . As illustrated in  FIG. 19 , the filaments  34  that comprise braided conductive member  28  are composed of a composite wire  110 . The composite wire  110  includes an electrically conductive wire  112  that is used for delivering ablation energy in an ablation procedure or for detecting electrical activity during a mapping procedure. Electrical wire  112  is contained within a lumen  114  that also contains a perfusion lumen  116 . Perfusion lumen  116  is used to deliver irrigation fluid or a contrast fluid as described in connection with  FIG. 18 . Once braided conductive member  28  has been constructed with composite wire  110 , the insulation  118  surrounding wire filament  112  can be stripped away to form an electrode surface. Holes can then be provided into perfusion lumen  116  to then allow perfusion at targeted sites along the electrode surface. As with the embodiment illustrated in  FIG. 18 , the perfusion lumens can be connected together to form a manifold which manifold can then be connected to, for example, perfusion tube  120  and connected to a fluid delivery device. 
       Shrouds 
       [0089]    The use of a shroud or shrouds to cover at least a portion of braided conductive member  28  can be beneficial in several ways. The shroud can add protection to braided conductive member  28  during insertion and removal of catheter  10 . A shroud can also be used to form or shape braided conductive member  28  when in its deployed state. Shrouds may also reduce the risk of thrombi formation on braided conductive member  28  by reducing the area of filament and the number of filament crossings exposed to blood contact. This can be particularly beneficial at the ends  30  and  32  of braided conductive member  28 . The density of filaments at ends  30  and  32  is greatest and the ends can therefore be prone to blood aggregation. The shrouds can be composed of latex balloon material or any material that would be resistant to thrombi formation durable enough to survive insertion through an introducer system, and would not reduce the mobility of braided conductive member  28 . The shrouds can also be composed of an RF transparent material that would allow RF energy to pass through the shroud. If an RF transparent material is used, complete encapsulation of braided conductive member  28  is possible. 
         [0090]    A shroud or shrouds may also be useful when irrigation or perfusion is used, since the shrouds can act to direct irrigation or contrast fluid to a target region. 
         [0091]      FIGS. 20A-20E  illustrate various examples of shrouds that may be used in the present invention.  FIG. 20A  illustrates shrouds  130  and  132  disposed over end regions  31  and  33 , respectively, of braided conductive member  28 . This configuration can be useful in preventing coagulation of blood at the ends of braided conductive member  28 .  FIG. 20B  illustrates shrouds  130  and  132  used in conjunction with an internal shroud  134  contained inside braided conductive member  28 . In addition to preventing blood coagulation in regions  31  and  32 , the embodiment illustrated in  FIG. 20B  also prevents blood from entering braided conductive member  28 . 
         [0092]      FIG. 20C  illustrates shrouds  130  and  132  being used to direct and irrigation fluid or contrast medium along the circumferential edge of braided conductive member  28 . In the embodiment illustrated in  FIG. 20C , perfusion can be provided as illustrated in  FIGS. 18 and 19 . 
         [0093]      FIG. 20D  illustrates the use of an external shroud that covers braided conductive member  28 . Shroud  136  completely encases braided conductive member  28  and thereby eliminates blood contact with braided conductive member  28 . Shroud  136  may be constructed of a flexible yet ablation-energy transparent material so that, when used in an ablation procedure, braided conductive member  28  can still deliver energy to a targeted ablation site. 
         [0094]      FIG. 20E  also illustrates an external shroud  137  encasing braided conductive member  28 . Shroud  137  may also be constructed of a flexible yet ablation-energy transparent material. Openings  139  may be provided in shroud  137  to allow the portions of braided conductive member  28  that are exposed by the opening to come into contact with tissue. Openings  139  may be elliptical, circular, circumferential, etc. 
       Guiding Sheaths 
       [0095]    There may be times during ablation or mapping procedures when catheter  10  is passing through difficult or tortuous vasculature. During these times, it may be helpful to have a guiding sheath through which to pass catheter  10  so as to allow easier passage through the patient&#39;s vasculature. 
         [0096]      FIG. 21  illustrates one example of a guiding sheath that may be used in connection with catheter  10 . As illustrated in  FIG. 21 , the guiding sheath  140  includes a longitudinal member  142 . Longitudinal member  142  may be constructed of a material rigid enough to be pushed next to catheter shaft  12  as the catheter is threaded through the vasiculature. In one example, longitudinal member  142  may be stainless steel. Longitudinal member  142  is attached to a sheath  144  disposed at the distal end  146  of longitudinal member  142 . The split sheath  144  may have one or more predetermined curves  148  that are compatible with the shapes of particular blood vessels (arteries or veins) that catheter  10  needs to pass through. Split sheath  144  may extend proximally along longitudinal member  142 . For example, sheath  144  and longitudinal member  142  may be bonded together for a length of up to 20 or 30 centimeters to allow easier passage through the patient&#39;s blood vessels. Sheath  144  includes a predetermined region  150  that extends longitudinally along sheath  144 . Region  150  may be, for example, a seam, that allows sheath  144  to be split open so that the guiding sheath  140  can be pulled back and peeled off catheter shaft  12  in order to remove the sheath. 
         [0097]    In another embodiment, longitudinal member  142  may be a hypotube or the like having an opening  152  at distal end  146  that communicates with the interior of sheath  144 . In this embodiment, longitudinal member  142  can be used to inject irrigation fluid such as saline or a contrast medium for purposes of cooling, flushing, or visualization. 
       Methods of Use 
       [0098]    Reference is now made to  FIGS. 22 ,  23 , and  24 , which figures illustrate how the catheter of the present invention may be used in endocardial and epicardial applications. 
         [0099]    Referring to  FIG. 22 , this figure illustrates an endocardial ablation procedure. In this procedure, catheter shaft  12  is introduced into a patient&#39;s heart  150 . Appropriate imaging guidance (direct visual assessment, camera port, fluoroscopy, echocardiographic, magnetic resonance, etc.) can be used.  FIG. 22  in particular illustrates catheter shaft  12  being placed in the left atrium of the patient&#39;s heart. Once catheter shaft  12  reaches the patient&#39;s left atrium, it may then be introduced through an ostium  152  of a pulmonary vein  154 . As illustrated, braided conductive member  28  is then expanded to its deployed position, where, in the illustrated embodiment, braided conductive member  28  forms a disk. Catheter shaft  12  then advanced further into pulmonary vein  154  until the distal side  156  of braided conductive member  28  makes contact with the ostium of pulmonary vein  154 . External pressure may be applied along catheter shaft  12  to achieve the desired level of contact of braided conductive member  28  with the ostium tissue. Energy is then applied to the ostium tissue  152  in contact with braided conductive member  28  to create an annular lesion at or near the ostium. The energy used may be RF (radiofrequency), DC, microwave, ultrasonic, cryothermal, optical, etc. 
         [0100]    Reference is now made to  FIG. 23 , which figure illustrates an epicardial ablation procedure. As illustrated in  FIG. 23 , catheter shaft  12  is introduced into a patient&#39;s thoracic cavity and directed to pulmonary vein  154 . Catheter  10  may be introduced through a trocar port or intraoperatively during open chest surgery Using a steering mechanism, preformed shape, or other means by which to make contact between braided conductive member  128  and the outer surface  158  of pulmonary vein  154 , braided conductive member  28  is brought into contact with the outer surface  158  of pulmonary vein  154 . Appropriate imaging guidance (direct visual assessment, camera port, fluoroscopy, echocardiographic, magnetic resonance, etc.) can be used. As illustrated in  FIG. 23 , in this procedure, braided conductive member  28  remains in its undeployed or unexpanded condition. External pressure may be applied to achieve contact between braided conductive member  28  with pulmonary vein  154 . Once the desired contact with the outer surface  158  of pulmonary vein  154  is attained, ablation energy is applied to surface  158  via braided conductive member  28  using, for example, RF, DC, ultrasound, microwave, cryothermal, or optical energy. Thereafter, braided conductive member  28  may be moved around the circumference of pulmonary vein  154 , and the ablation procedure repeated. This procedure may be used to create, for example, an annular lesion at or near the ostium. 
         [0101]    Use of the illustrated endocardial or epicardial procedures may be easier and faster than using a single “point” electrode since a complete annular lesion may be created in one application of RF energy. 
         [0102]    Reference is now made to  FIG. 24  which figure illustrates an endocardial mapping procedure. In the procedure illustrated in  FIG. 24 , catheter shaft  12  is introduced into pulmonary vein  154  in the manner described in connection with  FIG. 22 . Once braided conductive  28  has reached a desired location within pulmonary vein  154 , braided conductive member  28  is expanded as described in connection with, for example,  FIGS. 2-5  until filaments  34  contact the inner wall  160  of pulmonary vein  154 . Thereafter, electrical activity within pulmonary vein  154  may be detected, measured, and recorded by an external device connected to the filaments  34  of braided conductive member  28 . 
         [0103]    Access to the patient&#39;s heart can be accomplished via percutaneous, vascular, surgical (e.g. open-chest surgery), or transthoracic approaches for either endocardial or epicardial mapping and/or mapping and ablation procedures. 
         [0104]    The present invention is thus able to provide an electrophysiology catheter capable of mapping and/or mapping and ablation operations. In addition, the catheter of the invention may be used to provide high density maps of a tissue region because electrocardiograms may be obtained from individual filaments  34  in braided conductive member  28  in either a bipolar or unipolar mode. 
         [0105]    Furthermore, the shape of the electrode region can be adjusted by controlling the radial expansion of braided conductive member  28  so as to improve conformity with the patient&#39;s tissue or to provide a desired mapping or ablation profile. Alternatively, braided conductive member  28  may be fabricated of a material of sufficient flexural strength so that the tissue is preferentially conformed to match the expanded or partially expanded shape of the braided conductive member  28 . 
         [0106]    The catheter of the present invention may be used for mapping procedures, ablation procedures, and temperature measurement and control on the distal and/or proximal facing sides of braided conductive member  28  in its fully expanded positions as illustrated in, for example,  FIG. 1 . In addition, the catheter of the present invention can be used to perform “radial” mapping procedures, ablation procedures, and temperature measurement and control. That is, the outer circumferential edge  76 , illustrated, for example, in  FIG. 8 , can be applied against an inner circumferential surface of a blood vessel. 
         [0107]    Furthermore, being able to use the same catheter for both mapping and ablation procedures has the potential to reduce procedure time and reduce X-ray exposure. 
         [0108]    The ability to expand braided conductive member  28  in an artery or vein against a tissue structure such as a freewall or ostium can provide good contact pressure for multiple electrodes and can provide an anatomical anchor for stability. Temperature sensors can be positioned definitively against the endocardium to provide good thermal conduction to the tissue. Lesions can be selectively produced at various sections around the circumference of braided conductive member  28  without having to reposition catheter  10 . This can provide more accurate lesion placement within the artery or vein. 
         [0109]    Braided conductive member  28 , in its radially expanded position as illustrated in particular in  FIGS. 1 and 8  is advantageous because, in these embodiments, it does not block the blood vessel during a mapping or ablation procedure, but allows blood flow through the braided conductive member thus allowing for longer mapping and/or ablation times, which can potentially improve accuracy of mapping and efficacy of lesion creation. 
         [0110]    Having thus described at least one illustrative embodiment of the invention, various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be within the spirit and scope of the invention. Accordingly, the foregoing description is by way of example only and is not intended as limiting. The invention is limited only as defined in the following claims and the equivalents thereto.