Patent Publication Number: US-9427278-B2

Title: Electrophysiology electrode having multiple power connections and electrophysiology devices including the same

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 12/688,618, filed Jan. 15, 2010 (U.S. Pat. No. 8,518,038), which is a continuation of U.S. patent application Ser. No. 10/255,025, filed Sep. 24, 2002 (U.S. Pat. No. 7,674,258), entitled “ELECTROPHYSIOLOGY ELECTRODE HAVING MULTIPLE POWER CONNECTIONS AND ELECTROPHYSIOLOGY DEVICES INCLUDING THE SAME,” the entire disclosures of which are incorporated herein by reference. 
    
    
     STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     NOT APPLICABLE 
     REFERENCE TO A “SEQUENCE LISTING,” A TABLE, OR A COMPUTER PROGRAM LISTING APPENDIX SUBMITTED ON A COMPACT DISK 
     NOT APPLICABLE 
     BACKGROUND OF THE INVENTION 
     1. Field of Inventions 
     The present inventions relate generally to therapeutic elements and, more particularly, to therapeutic elements which are well suited for the formation of relatively long lesions in body tissue. 
     2. Description of the Related Art 
     There are many instances where therapeutic elements must be inserted into the body. One instance involves the formation of therapeutic lesions to the treat cardiac conditions such as atrial fibrillation, atrial flutter and arrhythmia. Therapeutic lesions may also be used to treat conditions in other regions of the body including, but not limited to, the prostate, liver, brain, gall bladder, uterus and other solid organs. Typically, the lesions are formed by ablating tissue with one or more electrodes. Electromagnetic radio frequency (“RF”) energy applied by the electrode heats, and eventually kills (i.e. “ablates”), the tissue to form a lesion. During the ablation of soft tissue (i.e. tissue other than blood, bone and connective tissue), tissue coagulation occurs and it is the coagulation that kills the tissue. Thus, references to the ablation of soft tissue are necessarily references to soft tissue coagulation. “Tissue coagulation” is the process of cross-linking proteins in tissue to cause the tissue to jell. In soft tissue, it is the fluid within the tissue cell membranes that jells to kill the cells, thereby killing the tissue. Depending on the procedure, a variety of different electrophysiology devices may be used to position one or more electrodes at the target location. Each electrode is connected to a respective single power supply line and, in some instances, the power to the electrodes is controlled on an electrode-by-electrode basis. Examples of electrophysiology devices include catheters, surgical probes, and clamps. 
     Catheters used to create lesions typically include a relatively long and relatively flexible body that has one or more electrodes on its distal portion. The portion of the catheter body that is inserted into the patient is typically from 23 to 55 inches in length and there may be another 8 to 15 inches, including a handle, outside the patient. The proximal end of the catheter body is connected to the handle which includes steering controls. The length and flexibility of the catheter body allow the catheter to be inserted into a main vein or artery (typically the femoral artery), directed into the interior of the heart, and then manipulated such that the electrode contacts the tissue that is to be ablated. Fluoroscopic imaging is used to provide the physician with a visual indication of the location of the catheter. Exemplary catheters are disclosed in U.S. Pat. No. 5,582,609. 
     Surgical probes used to create lesions often include a handle, a relatively short shaft that is from 4 inches to 18 inches in length and either rigid or relatively stiff, and a distal section that is from 1 inch to 10 inches in length and either malleable or somewhat flexible. One or more electrodes are carried by the distal section. Surgical probes are used in epicardial and endocardial procedures, including open heart procedures and minimally invasive procedures where access to the heart is obtained via a thoracotomy, thoracostomy or median stemotomy. Exemplary surgical probes are disclosed in U.S. Pat. No. 6,142,994. 
     Clamps, which have a pair of opposable clamp members that may be used to hold a bodily structure or a portion thereof, are used in many types surgical procedures. Lesion creating electrodes have also been secured to certain types of clamps. Examples of clamps which carry lesion creating electrodes are disclosed in U.S. Pat. No. 6,142,994. Such clamps are particularly useful when the physician intends to position electrodes on opposite sides of a body structure in a bipolar arrangement. 
     The inventor herein has determined that, regardless of the type of electrophysiology device that is used, conventional apparatus and methods for forming therapeutic lesions are susceptible to improvement. For example, electrophysiology devices that are intended to form long lesions typically include a plurality of relatively short electrodes (typically about 10 mm). The inventor herein has determined that manufacturing costs could be reduced by reducing the number of electrodes without reducing the length of the lesions that the devices are capable of forming. The inventor herein has also determined that in some devices, such as bipolar clamps, the use of a plurality of spaced electrodes on opposite sides of a body structure may not be appropriate in all situations. 
     BRIEF SUMMARY OF THE INVENTION 
     An electrode assembly in accordance with the present inventions includes an electrode that is connected to at least two power supply lines. The present electrode assembly also provides a number of advantages over conventional electrode arrangements. For example, the present electrode assembly facilitates the formation of elongate lesions with fewer electrodes than conventional electrode arrangements. 
     The electrode assembly (or a plurality of electrode assemblies) may be used in electrophysiology devices including, but not limited to, catheters, surgical probes and clamps. In one exemplary bipolar clamp implementation, the present electrode assembly is provided on one clamp member and a similar electrode assembly (with an electrode and a pair of power return lines) is provided on the other clamp member. Such a clamp may be used to form long, continuous lesions without the gaps that may sometimes occur when a plurality of spaced power transmitting electrodes are positioned opposite a plurality of spaced return electrodes. 
     The above described and many other features and attendant advantages of the present inventions will become apparent as the inventions become better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Detailed description of preferred embodiments of the inventions will be made with reference to the accompanying drawings. 
         FIG. 1  is a plan view of an electrode assembly in accordance with a preferred embodiment of a present invention. 
         FIG. 2  is a plan view of an electrode support structure in accordance with a preferred embodiment of a present invention. 
         FIG. 3  is a plan view of an electrode assembly and electrode support structure in accordance with a preferred embodiment of a present invention. 
         FIG. 4  is a section view taken along line  4 - 4  in  FIG. 3 . 
         FIG. 5  is a front perspective view of a power supply and control device in accordance with a preferred embodiment of a present invention. 
         FIG. 6A  is a diagrammatic view of a system in accordance with a preferred embodiment of a present invention. 
         FIG. 6B  is a diagrammatic view of a system in accordance with a preferred embodiment of a present invention. 
         FIG. 7  is a flow chart of a method in accordance with a preferred embodiment of the present invention. 
         FIG. 8  is a plan view of an energy transmission assembly in accordance with a preferred embodiment of a present invention. 
         FIG. 9  is a section view taken along line  9 - 9  in  FIG. 8 . 
         FIG. 10  is a section view taken along line  10 - 10  in  FIG. 8 . 
         FIG. 11  is an enlarged view of a portion of the energy transmission assembly illustrated in  FIG. 8 . 
         FIG. 12  is a section view taken along line  12 - 12  in  FIG. 11 . 
         FIG. 13  is a plan view of a clamp in accordance with a preferred embodiment of a present invention. 
         FIG. 14  is a section view taken along line  14 - 14  in  FIG. 13 . 
         FIG. 15  is a top view of a portion of the clamp illustrated in  FIG. 13 . 
         FIG. 16  is a plan view showing the energy transmission assembly illustrated in  FIG. 8  in combination with the clamp illustrated in  FIG. 13 . 
         FIG. 17  is a section view of an energy transmission assembly in accordance with a preferred embodiment of a present invention. 
         FIG. 18  is a section view taken along line  18 - 18  in  FIG. 17 . 
         FIG. 19  is a section view of an energy transmission assembly in accordance with a preferred embodiment of a present invention. 
         FIG. 20  is a section view taken along line  20 - 20  in  FIG. 19 . 
         FIG. 21  is a section view of an energy transmission assembly in accordance with a preferred embodiment of a present invention. 
         FIG. 22  is a plan view of a surgical probe in accordance with a preferred embodiment of a present invention. 
         FIG. 23  is a section view taken along line  23 - 23  in  FIG. 22 . 
         FIG. 24  is a section view taken along line  24 - 24  in  FIG. 22 . 
         FIG. 25  is a section view taken along line  25 - 25  in  FIG. 22 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following is a detailed description of the best presently known modes of carrying out the inventions. This description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the inventions. 
     The detailed description of the preferred embodiments is organized as follows: 
     Electrodes, Temperature Sensing and Power Control 
     Energy Transmission Assemblies 
     Surgical Probes 
     The section titles and overall organization of the present detailed description are for the purpose of convenience only and are not intended to limit the present inventions. 
     Electrodes, Temperature Sensing and Power Control 
     As illustrated for example in  FIG. 1 , an electrode assembly  100  in accordance with a preferred embodiment of a present invention includes an electrode  102  and first and second power supply lines  104  and  106  that are connected to the electrode. In other words, the electrode assembly  100  is configured such that power is supplied to the electrode  102  at least two locations. The power will preferably, although not necessarily, be supplied to each of the locations simultaneously. In the exemplary implementation, the electrode  102  includes first and second generally cylindrical base portions  108  and  110  and a helical portion  112 . The power supply lines  104  and  106  are respectively connected to the base portions  108  and  110  by welds  114  and  116 . 
     Although the present electrode is not limited to any particular electrode configuration, the exemplary electrode  102  is preferably a spiral (or “helical”) coil that is relatively flexible. The exemplary electrode  102  is made of electrically conducting material, like copper alloy, platinum, or stainless steel, or compositions such as drawn-filled tubing (e.g. a copper core with a platinum jacket). The electrically conducting material can be further coated with platinum iridium or gold to improve its conduction properties and biocompatibility. An exemplary coil electrode configuration is disclosed in U.S. Pat. No. 5,797,905. With respect to the manufacture of a helical electrode, such an electrode may be manufactured by, for example, laser cutting a hypotube ( FIG. 1 ) or winding wire that is either round or rectangular in cross-section into the desired shape ( FIG. 17 ). 
     The structural and electrical characteristics of the electrode  102 , which will vary from application to application, are preferably such that the power supplied to one portion of the electrode will be substantially dissipated before it reaches a portion of the electrode to which power is being independently supplied. For cardiovascular applications, the length is preferably between about 2 cm and 8 cm in those instances where power is supplied at the longitudinal ends and the end to end resistance is about 5 ohm to about 15 ohm. Typically, about 80% of the power supplied to one of the ends will be dissipated prior to reaching the mid-point of the electrode. Such a combination of characteristic facilitates regional power control of the electrode in the manner described below with reference with  FIGS. 5-7 . The diameter preferably ranges from about 1.5 mm to about 3 mm for cardiovascular applications. In one preferred implementation where a laser cut hypotube is connected to a source of RF energy at each of its longitudinal ends, the wall thickness of the hypotube is about 0.12 mm, the length is 6.4 cm, the outer diameter is about 2 mm, and the end to end resistance is about 10 ohms. 
     In an exemplary three power supply line embodiment that is otherwise essentially identical to the two power supply line embodiment described above, the electrode preferably includes a third base portion at the mid-point between the base portions at the longitudinal ends of the electrode. The three power supply lines are respectively connected to the three base portions. Here, the length of the electrode preferably ranges from about 6 cm to about 12 cm and the resistance between adjacent base portions will be about 5 ohm to about 15 ohm and, in a preferred implementation, about 10 ohms. 
     As an alternative, the electrodes may be in the form of solid rings of conductive material, like platinum, or can comprise a conductive material, like platinum-iridium or gold, coated upon an underlying non-conductive support member using conventional coating techniques or an ion beam assisted deposition (IBAD) process. For better adherence, an undercoating of nickel or titanium can be applied. The electrodes can also be formed with a conductive ink compound that is pad printed onto an underlying non-conductive support member. A preferred conductive ink compound is a silver-based flexible adhesive conductive ink (polyurethane binder), however other metal-based adhesive conductive inks such as platinum-based, gold-based, copper-based, etc., may also be used to form electrodes. Such inks are more flexible than epoxy-based inks Power may also be supplied to these alternative electrodes at two or more positions. 
     Turning to  FIGS. 2-4 , the electrode  102  may be carried by a support structure  118 . The exemplary support structure  118  is a flexible tubular structure which has an outer diameter that is, depending on the diameter of the electrode  102 , typically between about 1.5 mm and about 3 mm. The support structure  118  in the illustrated embodiment, which is intended for use in cardiovascular applications, has an outer diameter of about 2 mm. Suitable support structure materials include, for example, flexible biocompatible thermoplastic tubing such as unbraided Pebax® material, polyethylene, or polyurethane tubing. The support structure  118  is provided with a pair of apertures  120  and  122  for the power supply lines  104  and  106  as well as a tip member  124 . 
     A plurality of temperature sensors, such as thermocouples or thermistors, may be located on or under the electrode  102  for temperature control purposes. In the exemplary implementation, two pairs of temperature sensors  126   a / 126   b  and  128   a / 128   b  are employed. Each of the temperature sensors operate independently of one another. Temperature sensors  126   a  and  128   b  are located at the longitudinal edges of the electrode  102 , while temperature sensors  126   b  and  128   a  are spaced a distance equal to about ⅓ of the total electrode length from the respective longitudinal ends of the electrode. A third pair of temperature sensors could be provided in the aforementioned embodiment in which three power supply lines are connected to the electrode. In some embodiments, a reference thermocouple (not shown) may also be provided on the support structure  118  in spaced relation to the electrode  102 . Signals from the temperature sensors are transmitted to a power supply and control device by way of signal lines  130 . 
     The temperature sensors  126   a / 126   b  and  128   a / 128   b  are preferably located within a linear channel  132  that is formed in the support structure  118 . The linear channel may extend over the entire length of the support structure  118  or only over the portion that carries the electrode (or electrodes)  102 . The linear channel  132  insures that the temperature sensors will all face in the same direction (e.g. facing tissue) and be arranged in linear fashion. This arrangement results in more accurate temperature readings which, in turn, results in better temperature control. As such, the actual tissue temperature will more accurately correspond to the temperature set by the physician on the power supply and control device, thereby providing the physician with better control of the lesion creation process and reducing the likelihood that embolic materials will be formed. Such a channel may be employed in conjunction with any of the electrode support structures disclosed herein. 
     As illustrated for example in  FIGS. 5 and 6A , the electrode assembly  100  may be used in conjunction with an electrosurgical unit (“ESU”)  134  that supplies and controls power, such RF power. A suitable ESU is the Model  4810  ESU sold by Boston Scientific Corporation of Natick, Mass. The exemplary ESU  134  illustrated in  FIG. 5  includes a controller  135 , a source of RF power  137  that is controlled by the controller, and a plurality of displays and buttons that are used to set the level of power supplied to the electrode  102  and the temperature at various locations on the electrode. The exemplary ESU  134  illustrated is operable in a bipolar mode, where tissue coagulation energy emitted by the electrode  102  is returned through a return electrode  102   a , and a unipolar mode, where the tissue coagulation energy emitted by the electrode is returned through one or more indifferent electrodes (not shown) that are externally attached to the skin of the patient with a patch or one or more electrodes (not shown) that are positioned in the blood pool. The return electrode  102   x , which in a bipolar configuration is preferably (but not necessarily) identical to the electrode  102 , may be connected to the ESU  134  by a pair of power return lines  104   a  and  106   a . The return electrode  102   a  and power return lines  104   a  and  106   a  together define a return electrode assembly  100   a.    
     The ESU  134  in the illustrated implementation is provided with a power output connector  136  and a pair of return connectors  138 . The electrode  102  is connected to the power output connector  136  by way of the power supply lines  104  and  106  and a power connector  140 , while the return electrode  102   a  is connected to one of the return connectors  138  by way of the power return lines  104   a  and  106   a  and a return connector  142 . In a preferred implementation, the ESU output and return connectors  136  and  138  have different shapes to avoid confusion and the power and return connectors  140  and  142  are correspondingly shaped. In the exemplary bipolar energy transmission assembly  144  illustrated in  FIG. 8 , for example, the power connector  140  has a generally circular shape corresponding to the ESU power output connector  136  and the return connector  142  has a generally rectangular shape corresponding to the ESU return connector  138 . Signals from the temperature sensors  126   a / 126   b  and  128   a / 128   b  are transmitted to the ESU  134  by way of the signal lines  130  and the power connector  140 . 
     The exemplary ESU  134  illustrated in  FIGS. 5 and 6A  is configured to individually power and control a plurality of electrodes (typically relatively short electrodes that are about 10 mm in length). This is sometimes referred to as “multi-channel control” and the ESU  134  preferably includes up to 8 channels. The exemplary ESU  134  is also configured to individually power and control two or more portions of a single electrode as well as two or more portions of each of a plurality of electrodes during a lesion formation procedure. The electrode  102  in the exemplary implementation is divided into two portions for power control purposes—the electrode portion connected to the power supply line  104  on one side of the dash line in FIG.  6 A and the electrode portion connected to the power supply line  106  on the other side of the dash line. [It should be emphasized that this is not a physical division and that the electrode  102  is preferably a continuous, unitary structure.] The electrode  102  is placed adjacent to tissue and power to one portion is controlled by control channel CH1 and power to the other portion is controlled by control channel CH2. The power is preferably, although not necessarily, supplied to both portions simultaneously. The above-described power supply/lesion formation method is illustrated in  FIG. 7 . 
     More specifically, the level of power supplied to the electrode  102  by way of the power supply line  104  may be controlled based on the temperatures sensed by the temperature sensors  126   a / 126   b , while the level of power supplied to the electrode  102  by way of the power supply line  106  may be controlled based on the temperatures sensed by the temperature sensors  128   a / 128   b . In one exemplary control scheme, the level of power supplied to the electrode  102  by way of the power supply line  104  would be controlled based on the highest of the two temperatures sensed by the temperature sensors  126   a / 126   b , while the level of power supplied to the electrode  102  by way of the power supply line  106  would be controlled based on the highest of the two temperatures sensed by the temperature sensors  128   a / 128   b.    
     The amount of power required to coagulate tissue typically ranges from 5 to 150 w. Suitable temperature sensors and power control schemes that are based on sensed temperatures are disclosed in U.S. Pat. Nos. 5,456,682, 5,582,609 and 5,755,715. 
     The actual number and location of the temperature sensors may be varied in order to suit particular applications. As illustrated for example in  FIG. 6B , the temperature sensors  126   b  and  128   a  may be located on the return electrode  102   a  in certain bipolar implementations, such as the exemplary bipolar energy transmission assembly  144  illustrated in  FIG. 8 . Nevertheless, the power control scheme will preferably be the same in that the level of power supplied to the electrode  102  by way of the power supply line  104  would be controlled based on the temperatures sensed by the temperature sensors  126   a / 126   b , while the level of power supplied to the electrode  102  by way of the power supply line  106  would be controlled based on the temperatures sensed the temperature sensors  128   a / 128   b.    
     In those instances where a plurality of spaced electrodes  102  are provided, such as in the surgical probe  230  illustrated in  FIG. 22  that operates in a unipolar mode, each of the electrodes will preferably be connected to a respective pair of power supply lines  104  and  106  and include its own set of temperature sensors  126   a / 126   b  and  128   a / 128   b . Each of the electrodes  102  on the surgical probe  230  will also preferably be divided into two portions for power control purposes and the level of power supplied to the each electrode portion by way of the power supply lines  104  would be controlled based on the temperatures sensed by the temperature sensors  126   a / 126   b , while the level of power supplied to the electrode portions by way of the power supply lines  106  would be controlled based on the temperatures sensed by the temperature sensors  128   a / 128   b.    
     Energy Transmission Assemblies 
     The electrodes  102  may be used in conjunction with a wide variety of electro physiology devices. One example is an energy transmission assembly, which is an electrophysiology device that may be combined with a conventional surgical tool to form a tissue coagulating device. Although the present invention are not limited to any particular surgical tool, clamps are one example of a surgical tool that may be used in conjunction with energy transmission assemblies in accordance with the present inventions. As used herein, the term “clamp” includes, but is not limited to, clamps, clips, forceps, hemostats, and any other surgical device that includes a pair of opposable clamp members that hold tissue, at least one of which is movable relative to the other. In some instances, the clamp members are connected to a scissors-like arrangement including a pair of handle supporting arms that are pivotably connected to one another. The clamp members are secured to one end of the arms and the handles are secured to the other end. Certain clamps that are particularly useful in minimally invasive procedures also include a pair of handles and a pair of clamp members. Here, however, the clamp members and handles are not mounted on the opposite ends of the same arm. Instead, the handles are carried by one end of an elongate housing and the clamp members are carried by the other. A suitable mechanical linkage located within the housing causes the clamp members to move relative to one another in response to movement of the handles. The clamp members may be linear or have a predefined curvature that is optimized for a particular surgical procedure or portion thereof. The clamp members may also be rigid or malleable. 
     In one implementation, the exemplary energy transmission assembly that is generally represented by reference numeral  144  in  FIGS. 8-12  may be used to covert the conventional clamp  200  illustrated in  FIGS. 13-15  into the tissue coagulation device  220  illustrated in  FIG. 16 . Referring first to  FIGS. 13-15 , one example of a conventional clamp that may be used in conjunction with the present inventions is generally represented by reference numeral  200 . The clamp  200  includes a pair of rigid arms  202  and  204  that are pivotably connected to one another by a pin  206 . The proximal ends of the arms  202  and  204  are respectively connected to a pair handle members  208  and  210 , while the distal ends are respectively connected to a pair of clamp members  212  and  214 . The clamp members  212  and  214  may be rigid or malleable and, if rigid, may be linear or have a pre-shaped curvature. A locking device  216  locks the clamp in the closed orientation, and prevents the clamp members  212  and  214  from coming any closer to one another than is illustrated in  FIG. 13 , thereby defining a predetermined spacing between the clamp members. The clamp  200  is also configured for used with a pair of soft, deformable inserts (not shown) that may be removably carried by the clamp members  212  and  214  and allow the clamp to firmly grip a bodily structure without damaging the structure. To that end, the clamp members  212  and  214  are each include a slot  216  that is provided with a sloped inlet area  218  and the inserts include mating structures that are removably friction fit within the slots. The present energy transmission assemblies may be mounted on the clamp members in place of the inserts. 
     Turning to  FIGS. 8-10 , the exemplary energy transmission assembly  144  includes a power transmitting electrode assembly  100  (i.e. an electrode  102  and first and second power supply lines  104  and  106 ) and a return electrode assembly  100   a  (i.e. an electrode  102   a  and first and second power supply lines  104   a  and  106   a ). The electrode assemblies  100  and  100   a  are carried on respective support structures  118  and  118   a . The support structures  118  and  118   a  are connected to a flexible cable  146  by a molded plastic junction  148 . The first and second power supply lines  104  and  106  and signal lines  130  run from the electrode  102  extend through the support structure  118  and the cable  146  to the connector  140 . The first and second power return lines  104   a  and  106   a  run from the electrode  102   x , through the support structure  118   a  and the cable  146  to the connector  142 . In the exemplary implementation, the cable  146  is secured to a handle  150  with a strain relief element  152 . 
     The exemplary energy transmission assembly  144  also includes a pair of base members  154  and  154   a  which are used to connect the electrode assemblies  100  and  100   a  to the clamp  200 . Although the configuration of the energy transmission assemblies  144  may vary from application to application to suit particular situations, the exemplary energy transmission assembly is configured such that the electrodes  102  and  102   a  will be parallel to one another as well as relatively close to one another (i.e. a spacing of about 1-10 mm) when the clamp  200  is in the closed orientation. Such an arrangement will allow the energy transmission assembly to grip a bodily structure without cutting through the structure. Referring more specifically to  FIGS. 11-15 , the base member  154  includes a main portion  156 , with a groove  158  that is configured to receive the support structure  118  and electrode  102 , and a connector  160  that is configured to removably mate with the slot  216  in the clamp  200 . [It should be noted that the configuration of the base member  154   a  is identical to that of the base member  154  in the illustrated embodiment.] About 20% of the electrode surface (i.e. about 75° of the 360° circumference) is exposed in the illustrated embodiment. Adhesive may be used to hold the support structure  118  and electrode  102  in place. The exemplary connector  160  is provided with a relatively thin portion  162  and a relatively wide portion  164 , which may consist of a plurality of spaced members (as shown) or an elongate unitary structure, in order to correspond to the shape of the slot  216 . 
     The base members  154  and  154   a  are preferably formed from polyurethane. The length of the base members in the exemplary energy transmission assemblies will vary according to the intended application. In the area of cardiovascular treatments, it is anticipated that suitable lengths will range from, but are not limited to, about 4 cm to about 10 cm. In the exemplary implementation, where the electrodes  102  and  102   a  are preferably about 6.4 cm, the base members  154  and  154   a  will be about 6.6 cm. 
     As illustrated for example in  FIG. 16 , the exemplary energy transmission assembly  144  and clamp  200  may be combined to form a tissue coagulation device  220 . More specifically, the electrode assemblies  100  and  100   a  may be secured to the clamp members  212  and  214  by the base members  154  and  154   a . The coagulation device  220  may be used to form a lesion by, for example, positioning the electrode assemblies  100  and  100   a  on opposite sides of a tissue structure with the clamp members  212  and  214 . Energy from a power supply and control device (such as the ESU  134  illustrated in  FIG. 5 ) may be transmitted to both longitudinal ends of the electrode  102  by way of the connector  140  and returned to the power supply and control device by way of the electrode  102   a  and connector  142 . 
     One example of a procedure that may be performed with the exemplary tissue coagulation device  220  is the formation of transmural epicardial lesions to isolate the sources of focal (or ectopic) atrial fibrillation and, more specifically, the creation of transmural lesions around the pulmonary veins. Lesions may be created around the pulmonary veins individually or, alternatively, lesions may be created around pairs of pulmonary veins. For example, a first transmural epicardial lesion may be created around the right pulmonary vein pair and a second transmural epicardial lesion may be created around the left pulmonary vein pair. Thereafter, if needed, a linear transmural epicardial lesion may be created between the right and left pulmonary vein pairs. A linear transmural lesion that extends from the lesion between the right and left pulmonary vein pairs to the left atrial appendage may also be formed. These linear lesions may be formed with the tissue coagulation device  220  by forming a hole in the atria, inserting one of the clamp members (and corresponding electrode assembly) into the atria, and then closing the clamp members along the desired portion of the atria. Alternatively, a linear transmural epicardial lesion may be formed with the surgical probe illustrated in  FIG. 22 . It should also be noted that, instead of forming multiple lesions, a single lesion may be formed around all four of the pulmonary veins. 
     The exemplary energy transmission assembly  144  may be modified in a variety of ways. For example, a layer of Dacron or a Dacron/collagen composite may be placed over the exposed surface of the electrodes  102  and  102   x . This material, when wetted with saline, reduces tissue desiccation and makes current densities more uniform. As such, surface char is avoided and transmural lesion formation is ensured. 
     The base members that carry the electrode assemblies may also be reconfigured in order to account for situations where the associated clamp lacks the aforementioned slots  216 . As illustrated for example in  FIGS. 17 and 18 , the energy transmitting portion of an exemplary energy transmission assembly  166  includes an electrode assembly  100 ′ and a base member  168  that carries an electrode  102 ′ (thereby acting as a support structure) and is configured to be removably slipped over and secured to a clamp member, such as one of the clamp members  212  and  214 . The electrode assembly  100 ′ is substantially similar to the electrode assembly  100 . Here, however, the electrode  102 ′ is in the form of a wound wire (although a laser cut hypotube-type electrode could also be employed here). In one exemplary implementation, the energy transmission assembly will be a bipolar arrangement that includes a second generally identical base member and electrode, as is discussed above with reference to  FIG. 8 . Such a bipolar energy transmission assembly may be configured such that the transmitting and return electrodes will be parallel to one another as well as relatively close to one another when the clamp is in the closed orientation in order to allow the energy transmission assembly to grip a bodily structure without cutting through the structure. Alternatively, in a unipolar implementation, the structure illustrated in  FIGS. 17 and 18  may be used in combination with an indifferent electrode that is externally attached to the skin of the patient with a patch or one or more electrodes that are positioned in the blood pool. 
     The exemplary base member  168  is preferably formed from a soft, resilient, low durometer material that is electrically insulating. Suitable materials include polyurethane, silicone and polyurethane/silicone blends having a hardness of between about 20 Shore D and about 72 Shore D. The base member  168  includes a longitudinally extending aperture  170  into which the clamp member may be inserted. The aperture  170  should be sized and shaped such that the base member  168  will be forced to stretch when the clamp member is inserted. If, for example, the aperture  170  has the same cross-sectional shape as the clamp member (e.g. both are elliptical), then the aperture should be slightly smaller in their cross-sectional dimensions than the corresponding clamp member. The stretching of the apertures  170  creates a tight interference fit between the base member  168  and clamp member. Additionally, although the aperture  170  has a semi-circular cross-section in the exemplary embodiment, the aperture may have a round, rectangular, square or elliptical cross-section, or define any other cross-sectional shape, depending on the particular application. 
     The exemplary base member  168  also includes a slot  172  that secures the electrode assembly  100 ′ in place. The configuration of the slot  172  will, of course, depend on the configuration of the electrode assembly that it is holding. The illustrated electrode  102 ′ is generally cylindrical in shape and the slot  172  has a corresponding arcuate cross-sectional shape. The arc is preferably greater than 180 degrees so that the base member  168  will deflect when the electrode  102 ′ is inserted into the slot  172  and then snap back to hold the electrode in place. Adhesive may also be used to secure the electrode  102 ′, especially in those instances where the arc is less than 180 degrees. 
     In order to accommodate the power supply lines  104  and  106  and the temperature sensor signal lines  130  ( FIG. 18 ), the exemplary base member  168  is also provided with a wire aperture  174 , a pair of power line holes  176  and four signal line holes  178  for the temperature sensors  126   a ′/ 126   b′  and  128   a ′/ 128   b ′. The number of power line and signal line holes will, of course, depend on the configuration of the electrode assembly  100 ′. A cable  180  provided for the power supply lines  104  and  106  and temperature sensor signal lines  130 . 
     Energy transmission assemblies in accordance with the present inventions may also be provided with apparatus that cools the tissue during tissue coagulation procedures. The tissue cooling apparatus disclosed herein employ conductive fluid to cool tissue during coagulation procedures. More specifically, and as described below and in U.S. application Ser. No. 09/761,981, which is entitled “Fluid Cooled Apparatus For Supporting Diagnostic And Therapeutic Elements In Contact With Tissue” and incorporated herein by reference, heat from the tissue being coagulated is transferred to ionic fluid to cool the tissue while energy is transferred from an electrode or other energy transmission device to the tissue through the fluid by way of ionic transport. The conductive fluid may be pumped through the tissue cooling apparatus ( FIGS. 19 and 20 ) or the tissue cooling apparatus may be saturated with the fluid prior to use ( FIG. 21 ). In either case, cooling tissue during a coagulation procedure facilitates the formation of lesions that are wider and deeper than those that could be realized with an otherwise identical device which lacks tissue cooling apparatus. Preferably, tissue cooling apparatus will be associated with both the transmitting electrode and the return electrode in a bipolar implementation. 
     Referring first to  FIGS. 19 and 20 , the energy transmitting portion of an exemplary energy transmission assembly  166 ′ includes an electrode  102 ′ and a base member  168 ′ that carries the electrode and is configured to be removably secured to a clamp member, such as one of the clamp members  212  and  214 . Many aspects of the exemplary energy transmission assembly  166 ′ are substantially similar to the assembly  166  and similar elements are represented by similar reference numerals. Here, however, a tissue cooling apparatus  182  is also provided. In one exemplary implementation, the energy transmission assembly will be a bipolar arrangement that includes a second generally identical base member, electrode and cooling apparatus, as is discussed above with reference to  FIG. 8 . Such a bipolar energy transmission assembly may be configured such that the transmitting and return electrodes will be parallel to one another as well as relatively close to one another when the clamp is in the closed orientation in order to allow the energy transmission assembly to grip a bodily structure without cutting through the structure. Alternatively, in a unipolar implementation, the structure illustrated in  FIGS. 19 and 20  may be used in combination with an indifferent electrode that is externally attached to the skin of the patient with a patch or one or more electrodes that are positioned in the blood pool. Additionally, although the aperture  170 ′ has an elliptical cross-section in the exemplary embodiment, the apertures may have a round, rectangular, square or semi-circular cross-section, or define any other cross-sectional shape, depending on the particular application. 
     The exemplary tissue cooling apparatus  182  includes a nanoporous outer casing  184  through which ionic fluid (represented by arrows F) is transferred. The ionic fluid preferably flows from one longitudinal end of the tissue cooling apparatus  182  to the other. The outer casing  184  is secured to the base member  168 ′ over the electrode  102 ′ such that a fluid transmission space  186  is defined therebetween. More specifically, the proximal and distal ends of the outer casing  184  are secured to the base member  168 ′ with anchoring devices (not shown) such as lengths of heat shrink tubing, Nitinol tubing or other mechanical devices that form an interference fit between the casing and the base member. Adhesive bonding is another method of securing the outer casing  184  to the base member  168 ′. The fluid transmission space will typically be about 0.5 mm to about 2.0 mm high and slightly wider than the associated electrode  102 ′. 
     The ionic fluid is supplied under pressure from a fluid source (not shown) by way of a supply line  188  and is returned to the source by way of a return line  190  in the exemplary implementation illustrated in  FIGS. 19 and 20 . The supply line  188  is connected to a fluid lumen  192  that runs from the proximal end of the base member  168 ′ to the distal region of the outer casing  184 . The fluid lumen  192  is connected to the fluid transmission space  186  by an aperture  194 . 
     The electrically conductive ionic fluid preferably possesses a low resistivity to decrease ohmic loses, and thus ohmic heating effects, within the outer casing  184 . The composition of the electrically conductive fluid can vary. In the illustrated embodiment, the fluid is a hypertonic saline solution, having a sodium chloride concentration at or near saturation, which is about 5% to about 25% weight by volume. Hypertonic saline solution has a relatively low resistivity of only about 5 ohm-cm, as compared to blood resistivity of about 150 ohm-cm and myocardial tissue resistivity of about 500 ohm-cm. Alternatively, the ionic fluid can be a hypertonic potassium chloride solution. 
     With respect to temperature and flow rate, a suitable inlet temperature for epicardial applications (the temperature will, of course, rise as heat is transferred to the fluid) is about 0 to 25° C. with a constant flow rate of about 2 to 20 ml/min. The flow rate required for endocardial applications where blood is present would be about three-fold higher (i.e. 6 to 60 ml/min.). Should applications so require, a flow rate of up to 100 ml/min. may be employed. In a closed system where the fluid is stored in a flexible bag, such as the Viaflex® bag manufactured by Baxter Corporation, and heated fluid is returned to the bag, it has been found that a volume of fluid between about 200 and 500 ml within the bag will remain at room temperature (about 22° C.) when the flow rate is between about 2 ml/min. and 20 ml/min. Alternatively, in an open system, the flexible bag should include enough fluid to complete the procedure. 160 ml would, for example, be required for a 20 minute procedure where the flow rate was 8 ml/min. 
     The fluid pressure within the outer casing  184  should be about 30 mm Hg in order to provide a structure that will resiliently conform to the tissue surface in response to a relatively small force normal to the tissue. Pressures above about 100 mm Hg will cause the outer casing  184  to become too stiff to properly conform to the tissue surface. For that reason, the flow resistance to and from the outer casing  184  should be relatively low. 
     The pores in the nanoporous outer casing  184  allow the transport of ions contained in the fluid through the casing and into contact with tissue. Thus, when the electrode  102 ′ transmits RF energy into the ionic fluid, the ionic fluid establishes an electrically conductive path through the outer casing  184  to the tissue being coagulated. Regenerated cellulose membrane materials, typically used for blood oxygenation, dialysis or ultrafiltration, are a suitable nanoporous material for the outer casing  184 . The thickness of the material should be about 0.002 to 0.005 inch. Although regenerated cellulose is electrically non-conductive, the relatively small pores of this material allow effective ionic transport in response to the applied RF field. At the same time, the relatively small pores prevent transfer of macromolecules through the material, so that pressure driven liquid perfusion is less likely to accompany the ionic transport, unless relatively high pressure conditions develop within the outer casing  184 . 
     Hydro-Fluoro™ material, which is disclosed in U.S. Pat. No. 6,395,325, is another material that may be used. Materials such as nylons (with a softening temperature above 100° C.), PTFE, PEI and PEEK that have nanopores created through the use of lasers, electrostatic discharge, ion beam bombardment or other processes may also be used. Such materials would preferably include a hydrophilic coating. Nanoporous materials may also be fabricated by weaving a material (such as nylon, polyester, polyethylene, polypropylene, fluorocarbon, fine diameter stainless steel, or other fiber) into a mesh having the desired pore size and porosity. These materials permit effective passage of ions in response to the applied RF field. However, as many of these materials possess larger pore diameters, pressure driven liquid perfusion, and the attendant transport of macromolecules through the pores, are also more likely to occur. 
     The electrical resistivity of the outer casing  184  will have a significant influence on lesion geometry and controllability. Low-resistivity (below about 500 ohm-cm) requires more RF power and results in deeper lesions, while high-resistivity (at or above about 500 ohm-cm) generates more uniform heating and improves controllability. Because of the additional heat generated by the increased body resistivity, less RF power is required to reach similar tissue temperatures after the same interval of time. Consequently, lesions generated with high-resistivity structures usually have smaller depth. The electrical resistivity of the outer casing can be controlled by specifying the pore size of the material, the porosity of the material, and the water adsorption characteristics (hydrophilic versus hydrophobic) of the material. A detailed discussion of these characteristics is found in U.S. Pat. No. 5,961,513. A suitable electrical resistivity for epicardial and endocardial lesion formation is about 1 to 3000 ohm-cm measured wet. 
     Generally speaking, low or essentially no liquid perfusion through the nanoporous outer casing  184  is preferred. When undisturbed by attendant liquid perfusion, ionic transport creates a continuous virtual electrode at the tissue interface. The virtual electrode efficiently transfers RF energy without need for an electrically conductive metal surface. Pore diameters smaller than about 0.1 μm retain macromolecules, but allow ionic transfer through the pores in response to the applied RF field. With smaller pore diameters, pressure driven liquid perfusion through the pores is less likely to accompany the ionic transport, unless relatively high pressure conditions develop within the outer casing  184  Larger pore diameters (up to 8 μm) can also be used to permit ionic current flow across the membrane in response to the applied RF field. With larger pore diameters, pressure driven fluid transport across the membrane is much higher and macromolecules (such as protein) and even small blood cells (such as platelets) could cross the membrane and contaminate the inside of the probe. Red blood cells would normally not cross the membrane barrier, even if fluid perfusion across the membrane stops. On balance, a pore diameter of 1 to 5 μm is suitable for epicardial and endocardial lesion formation. Where a larger pore diameter is employed, thereby resulting in significant fluid transfer through the porous region, a saline solution having a sodium chloride concentration of about 0.9% weight by volume would be preferred. 
     With respect to porosity, which represents the volumetric percentage of the outer casing  184  that is composed of pores and not occupied by the casing material, the magnitude of the porosity affects electrical resistance. Low-porosity materials have high electrical resistivity, whereas high-porosity materials have low electrical resistivity. The porosity of the outer casing  184  should be at least 1% for epicardial and endocardial applications employing a 1 to 5 μm pore diameter. 
     Turning to water absorption characteristics, hydrophilic materials are generally preferable because they possess a greater capacity to provide ionic transfer of RF energy without significant liquid flow through the material. 
     As illustrated for example in  FIG. 21 , an exemplary energy transmission assembly  166 ″ includes a base member  168 ″ that carries an electrode  102 ′ and a tissue cooling apparatus  196 . The tissue cooling apparatus  196  consists of a wettable fluid retention element  198  that is simply saturated with ionic fluid (such as saline) prior to use, as opposed to having the fluid pumped through the apparatus in the manner described above with reference to  FIGS. 19 and 20 . The electrode  102 ′ is carried within the fluid retention element  198 . The energy transmission assembly  166 ″ illustrated in  FIG. 21  may be provided in both bipolar and unipolar implementations. 
     Suitable materials for the fluid retention element  198  include biocompatible fabrics commonly used for vascular patches (such as woven Dacron®), open cell foam materials, hydrogels, nanoporous balloon materials (with very slow fluid delivery to the surface), and hydrophilic nanoporous materials. The effective electrical resistivity of the fluid retention element  198  when wetted with 0.9% saline (normal saline) should range from about 1 Ω-cm to about 2000 Ω-cm. A preferred resistivity for epicardial and endocardial procedures is about 1000 Ω-cm. 
     Other variations concern the manner in which the energy transmission assembly is secured to the clamp or other device. For example, the energy transmission assemblies may be permanently secured to a clamp or other device. Also, in any of the unipolar implementations described above, the base member may, if desired, be configured to be secured to both clamp members of a single clamp simultaneously instead on one clamp member. 
     Surgical Probes 
     As shown by way of example in  FIGS. 22-25 , a surgical probe  230  in accordance with a preferred embodiment of a present invention includes a relatively short shaft  232 , a shaft distal section  234  and a handle  234 . The shaft  232  consists of a hypotube  238 , which is either rigid or relatively stiff, and an outer polymer tubing  240  over the hypotube. The handle  236  preferably consists of two molded handle halves and is provided with strain relief element  242 . The shaft  232  in the illustrated embodiment may be from 4 inches to 18 inches in length and is preferably 6 inches to 8 inches. The distal section  234 , which is preferably either malleable, somewhat flexible or some combination thereof, may be from 1 inch to 10 inches in length and is preferably 2 to 3 inches. With respect to the distal section  234  in the exemplary embodiment, a plurality of electrode assemblies  100 , including electrodes  102  (or  102 ′) and power supply lines  104  and  106 , are carried on a support structure  118 . A tissue cooling apparatus, such as those disclosed in U.S. application Ser. No. 09/761,981, may be positioned over the electrodes  102  if desired. 
     As used herein the phrase “relatively stiff’ means that the shaft (or distal section or other structural element) is either rigid, malleable, or somewhat flexible. A rigid shaft cannot be bent. A malleable shaft is a shaft that can be readily bent by the physician to a desired shape, without springing back when released, so that it will remain in that shape during the surgical procedure. Thus, the stiffness of a malleable shaft must be low enough to allow the shaft to be bent, but high enough to resist bending when the forces associated with a surgical procedure are applied to the shaft. A somewhat flexible shaft will bend and spring back when released. However, the force required to bend the shaft must be substantial. Rigid and somewhat flexible shafts are preferably formed from stainless steel, while malleable shafts are formed from annealed stainless steel. 
     One method of quantifying the flexibility of a shaft, be it shafts in accordance with the present inventions or the shafts of conventional catheters, is to look at the deflection of the shaft when one end is fixed in cantilever fashion and a force normal to the longitudinal axis of the shaft is applied somewhere between the ends. Such deflection (cr) is expressed as follows:
 
 σ=WX   2 (3 L−X )/6 EI  
 
where:
 
W is the force applied normal to the longitudinal axis of the shaft,
 
L is the length of the shaft,
 
X is the distance between the fixed end of the shaft and the applied force,
 
E is the modulous of elasticity, and
 
I is the moment of inertia of the shaft.
 
     When the force is applied to the free end of the shaft, deflection can be expressed as follows:
 
 σ=WL   3 /3 EI  
 
     Assuming that W and L are equal when comparing different shafts, the respective E and 
     I values will determine how much the shafts will bend. In other words, the stiffness of a shaft is a function of the product of E and I. This product is referred to herein as the “bending modulus.” E is a property of the material that forms the shaft, while 1 is a function of shaft geometry, wall thickness, etc. Therefore, a shaft formed from relatively soft material can have the same bending modulus as a shaft formed from relatively hard material, if the moment of inertia of the softer shaft is sufficiently greater than that of the harder shaft. 
     For example, a relatively stiff 2 inch shaft (either malleable or somewhat flexible) would have a bending modulus of at least approximately 1 lb.-in. 2  Preferably, a relatively stiff 2 inch shaft will have a bending modulus of between approximately 3 lb.-in. 2  and approximately 50 lb.-in. 2 . By comparison, 2 inch piece of a conventional catheter shaft, which must be flexible enough to travel through veins, typically has bending modulus between approximately 0.1 lb.-in. 2  and approximately 0.3 lb.-in. 2 . It should be noted that the bending modulus ranges discussed here are primarily associated with initial deflection. In other words, the bending modulus ranges are based on the amount of force, applied at and normal to the free end of the longitudinal axis of the cantilevered shaft, that is needed to produce 1 inch of deflection from an at rest (or no deflection) position. 
     As noted above, the deflection of a shaft depends on the composition of the shaft as well as its moment of inertia. The shaft could be made of elastic material, plastic material, elasto-plastic material or a combination thereof. By designing the shaft to be relatively stiff (and preferably malleable), the surgical tool is better adapted to the constraints encountered during the surgical procedure. The force required to bend a relatively stiff 2 inch long shaft should be in the range of approximately 1.5 lbs. to approximately 12 lbs. By comparison, the force required to bend a 2 inch piece of conventional catheter shaft should be between approximately 0.2 lb. to 0.25 lb. Again, such force values concern the amount of force, applied at and normal to the free end of the longitudinal axis of the cantilevered shaft, that is needed to produce 1 inch of deflection from an at rest (or no deflection) position. 
     Ductile materials are preferable in many applications because such materials can deform plastically before failure due to fracturing. Materials are classified as either ductile or brittle, based upon the percentage of elongation when the fracture occurs. A material with more than 5 percent elongation prior to fracture is generally considered ductile, while a material with less than 5 percent elongation prior to fracture is generally considered brittle. Material ductility can be based on a comparison of the cross sectional area at fracture relative to the original cross area. This characteristic is not dependent on the elastic properties of the material. 
     Alternatively, the shaft could be a mechanical component similar to shielded (metal spiral wind jacket) conduit or flexible Loc-Line®, which is a linear set of interlocking ball and socket linkages that can have a center lumen. These would be hinge-like segmented sections linearly assembled to make the shaft. 
     In those instances where a malleable shaft  232  is desired, the hypotube  238  may be a heat treated malleable hypotube. By selectively heat treating certain portions of the hypotube, one section of the hypotube can be made more malleable than the other. The outer tubing  240  may be formed from Pebax® material, polyurethane, or other suitable materials. 
     As noted above, the distal section  234  can be either somewhat flexible, in that it will conform to a surface against which it is pressed and then spring back to its original shape when removed from the surface, malleable, or some combination thereof. A bending modulus of between 3 lb.-in. 2  and 50 lb.-in. 2  is preferred. In the exemplary implementation illustrated in  FIGS. 22-25 , the distal section  234  includes a malleable proximal portion and a flexible distal portion. Although the relative lengths of the portions may vary to suit particular applications, the malleable proximal portion and a flexible distal portion are equal in length in the illustrated embodiment. 
     The exemplary malleable portion includes a mandrel  242  made of a suitably malleable material, such as annealed stainless steel or beryllium copper, that may be fixed directly within the distal end of the shaft&#39;s hypotube  238  and secured by, for example, soldering, spot welding or adhesives. Sufficient space should be provided to allow the power supply lines  104  and  106  and the temperature sensor signal lines  130  to pass. An insulating sleeve  244  is placed over the mandrel  242  to protects the power supply lines  104  and  106  and the temperature sensor signal lines  130 . The insulating sleeve  244  is preferably formed from Pebax® material, polyurethane, or other suitable materials. Turning to the flexible portion, a spring member  246 , which is preferably either a solid flat wire spring (as shown), a round wire, or a three leaf flat wire Nitinol spring, is connected to the distal end of the mandrel  242  with a crimp tube or other suitable instrumentality. The distal end of the spring member  246  is connected to a tip member  248  by, for example, soldering, spot welding or adhesives. Other spring members, formed from materials such as 17-7 or carpenter&#39;s steel, may also be used. The spring member  246  is also enclosed within the insulating sleeve  244 . The spring member  246  may be pre-stressed so that the distal tip is pre-bent into a desired shape. Additional details concerning distal sections that have a malleable proximal portion and a flexible distal portion are provided in U.S. application Ser. No. 09/536,095, which is entitled “Loop Structure For Positioning Diagnostic Or Therapeutic Element On The Epicardium Or Other Organ Surface” and incorporated herein by reference. 
     In an alternative configuration, the distal section  234  may be formed by a hypotube that is simply a continuation of the shaft hypotube  238  covered by a continuation of the outer tubing  240 . However, the distal end hypotube can also be a separate element connected to the shaft hypotube  238 , if it is desired that the distal end hypotube have different stiffness (or bending) properties than the shaft hypotube. It should also be noted that the distal section  234  may be made malleable from end to end by eliminating the spring member  246  and extending the malleable mandrel  242  to the tip member  248 . Conversely, the distal section  234  may be made flexible from end to end by eliminating the malleable mandrel  242  and extending the spring member  246  from the hypotube  238  to the tip member  248 . 
     With respect to the connection of the electrode assemblies  100  on the exemplary surgical probe  230  illustrated in  FIGS. 22-25  to the ESU  134  or other power supply and control device, the power supply lines  104  and  106  and temperature sensor signal lines  130  associated with each electrode  102  pass through the distal section  234  and shaft  232  and are connected to a PC board  250  in the handle  236 . The handle also includes a port  252  that is configured to receive a connector cable (not shown) the connects the PC board  250  (and, therefore, the electrode assemblies  100 ) to the ESU  134  or other power supply and control device. 
     Although the present inventions have been described in terms of the preferred embodiments above, numerous modifications and/or additions to the above-described preferred embodiments would be readily apparent to one skilled in the art. By way of example, but not limitation, the present electrode assemblies may also be used in conjunction with steerable and non-steerable catheter-type probes. It is intended that the scope of the present inventions extend to all such modifications and/or additions and that the scope of the present inventions is limited solely by the claims set forth below.