Abstract:
An elongate, malleable ablation probe including an elongate malleable body ( 38 ) and a plurality of longitudinally spaced apart electrodes ( 40 ) disposed at a distal end thereof. The electrodes ( 40 ) are separated one from another by insulative material. In one embodiment, a malleable insert is provided for insertion into a flexible longitudinal sleeve, the flexible longitudinal sleeve conforming to the shape of the malleable insert upon such insertion. In other embodiments, a malleable core is surrounded by a flexible body, the electrodes ( 40 ) being mounted to the body.

Description:
The application is a divisional of application Ser. No. 09/485,361, filed Dec. 14, 2000, now U.S. Pat. No. 6,540,742 which is a 371 of PCT/AU98/00590, filed Jul. 24, 1998, which application(s) are incorporated herein by reference. 

   The present invention relates to a method and apparatus for mapping and ablating tissue, and in particular to a malleable, shapeable probe for producing elongated linear lesions in tissue. 
   BACKGROUND 
   It is known that tissue, including damaged myocardial tissue, can be ablated by the application of radio frequency energy thereto via conductive electrodes embodied in a probe structure. RF ablation of tissue is commonly used in an attempt to remove myocardial defects, tumours, portions of tissue mass, and the like. RF ablation can be used to treat cardial disfunctions such as ventricular arrhythmia, atrial flutter, atrial fibrillation, ventricular tachycardia and the like. 
   Such disorders involve abnormal heart muscles causing abnormal activity of the electrical signals that are generated to create muscle contraction. One result of this abnormal electrical activity in the atrial part of the heart muscle may be an irregular heartbeat. A common feature of atrial fibrillation is impaired atrial contraction. The heart beat rate may also be increased. 
   Electrode catheters are commonly used to effect RF ablation of tissue to remove or otherwise interrupt the abnormal electrical activity caused by defective myocardial tissue. 
     FIG. 1  is a schematic diagram illustrating such a catheter  10 . The catheter  10  is typically made of a highly flexible plastic or rubber tube  14 . At the distal end of the catheter body  14  are located a number of metal electrodes  12  for delivering RF energy. The conventional catheter probe utilises ring-like electrodes concentrically arranged around the catheter body  14 . Alternatively, the catheter probe  10  alone or in combination with the ring-like electrodes may have a single electrode at the tip of the distal end of the catheter  10 . The catheter body  14  includes a number of internal electrical conductors (not shown) connected to respective ones of the electrodes  12  at one end. The conductors can be connected at an opposite end of the catheter  10  to a source of RF energy and other equipment. The RF energy is delivered via the conductors to the electrodes  12 . 
   In use, such a catheter probe  10  is inserted via an incision in a patient&#39;s body into a blood vessel, such as a vein, and the catheter is then manoeuvred through the blood vessel to the patient&#39;s heart. Thus, the electrodes  12  at the distal end of the catheter  10  can be inserted into an interior chamber of a patient&#39;s heart to ablate endocardial tissue.  FIG. 2  is a simplified schematic diagram illustrating the catheter  10  disposed within a portion of an atrium  20 . A defective portion of the myocardial tissue is detected by mapping electrical activity in the myocardial tissue, and then applying RF energy via one or more of the electrodes  12  adjacent to the defective portion. 
   A significant disadvantage of conventional catheter ablation is that, due to the very flexible nature of the catheter itself, it is difficult to accurately position and maintain the positioning of the electrodes relative to a portion of myocardial tissue. This is disadvantageous in that movement and imprecise placement of the catheter can result undesirably in the ablation or destruction of healthy tissue, while at the same time the tissue sought-to-be ablated may not have been ablated, thereby requiring further ablation. 
   As will be understood from  FIG. 2 , due to the readily flexible nature of the catheter body  14  and its limited ability to retain any particular form, the catheter  10  is difficult to position at a desired location, and often does not adequately conform to the tissue surface. As shown in  FIG. 2 , due to contact with a far wall of the atrium, the catheter body  14  flexes upwardly from its insertion at left into the atrial chamber and is then bent downwardly at its distal end by the irregularity  22  in the myocardial tissue of the atrium  20 . Due to the way in which the catheter  10  is bent and its imprecise positioning, only a small portion of the distal end of the catheter  10  contacts the tissue at location  22 . In fact, only a small portion of the third electrode contacts the defective, irregularly shaped tissue  22 . 
   Another disadvantage of such catheter probes  10  is that they are directed to ablating focal defects, where only a portion of an electrode in contact with the tissue produces a “spot” or pointlike lesion in the tissue. 
   A further catheter ablation probe has been proposed using the same type of highly flexible catheter structure in combination with an external guide wire provided between the distal end and an intermediate point of the catheter probe. The guide wire can be tightened or released so as to control arcuate flexing of a sequence of band-like electrodes arranged along the catheter. However, this probe is also disadvantageous in that movement and placement of the catheter is still imprecise and the electrodes may not have good contact with irregular surfaces to be ablated. Still further, the ring-like electrodes of such a catheter probe also produce a “spot” or pointlike lesion in the tissue. 
   Thus, conventional catheter probes have a number of significant disadvantages. Firstly, the electrodes of the probe are directed to producing spot or pointlike lesions in tissue. Secondly, due to the highly flexible nature of the catheter body, it is difficult to manoeuvre and accurately position and retain the position of the electrodes of the catheter at any position. Thirdly, again due to the very flexible nature of the catheter typically made of soft, bendable plastic, or rubber like substances, the distal end of the catheter does not readily conform to irregularly shaped surfaces of tissue. Accordingly, a need clearly exists for a probe capable of overcoming one or more disadvantages of conventional devices. 
   SUMMARY OF THE INVENTION 
   In a first aspect, the present invention provides an elongate, malleable ablation probe including: 
   an elongate malleable body; and 
   a plurality of longitudinally spaced apart electrodes disposed at a distal end of said malleable body, said electrodes being separated one from another by insulative material. 
   Preferably, the electrodes are flat and are arranged linearly along said probe. 
   In a second aspect, the present invention provides a probe for ablating tissue, including: 
   an elongate, bendable body; 
   a plurality of substantially flat spaced apart electrodes linearly arranged along a longitudinal extent of said body and connected with a surface of said body; 
   insulative material separating said spaced apart electrodes one from another; 
   a plurality of electrical conductors, wherein at least one of said plurality of conductors is connected to each respective one of the plurality of electrodes; and 
   a malleable core disposed within said elongate body, whereby said probe is deformable and is able to retain a shape formed by bending said probe. 
   In a third aspect, the present invention provides a probe for ablating of tissue, comprising: 
   a tubular body of bendable material defining an elongate cavity; 
   a plurality of flat electrodes linearly arranged along the longitudinal extent of said tubular body; 
   insulative portions separating said electrodes from each other; 
   a plurality of electrical conductors, at least one of which is connected with each respective one of said plurality of electrodes; and 
   an insert member having a predefined shape for insertion into the elongate cavity of said tubular body, wherein said tubular body conforms to the predefined shape upon insertion of the insert member into the elongate cavity. 
   In a fourth aspect, the present invention provides a probe for ablating tissue, comprising: 
   an elongate body of bendable material, wherein said body has a substantially flat surface extending along a longitudinal extent of a distal end of said body; 
   a plurality of flat electrodes arranged in a linear configuration on said flat surface of said body in a predetermined spaced apart relationship to each other; 
   insulative material separating said flat electrodes one from another; 
   a plurality of conductors, wherein at least one conductor is connected with each respective one of said plurality of electrodes; and 
   a malleable core formed in said body, wherein said probe is deformable. 
   Preferably, in each of the above aspects of the invention, one or more prongs are connected with each electrode, wherein the one or more prongs is used to puncture the body and is capable of being bent. 
   In a fifth aspect, the present invention provides a probe for ablating tissue, comprising: 
   a relatively rigid body; 
   at least one flat, elongate electrode formed in a surface of a distal portion of said rigid body; and 
   at least one electrical conductor connected with said electrode for delivery of RF energy thereto. 
   Preferably, a temperature sensing devices is connected to at least one electrode. Still further, at least two conductors of the plurality of conductors are connected to the electrode, and one of the conductors comprises a thermocouple as the temperature sensing device. 
   Still further, in each of the above aspects, the body is preferably made of insulative material. 
   In a sixth aspect, the present invention provides a method of ablating tissue, said method comprising the steps of: 
   deforming an elongated, malleable ablation probe to conform to an irregular surface of said tissue, wherein said probe comprises a linear arrangement of flat electrodes separated one from another by insulative material along a longitudinal extent of said probe; and 
   ablating said tissue using one or more of said electrodes contacting said tissue. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described hereinafter, by way of example only, with reference to the drawings, in which: 
       FIG. 1  is a perspective view of a conventional catheter probe; 
       FIG. 2  is a side elevation view of the catheter probe of  FIG. 1  during use; 
       FIG. 3  is a bottom plan view of a hand-held surgical device incorporating an RF ablation probe according to the invention; 
       FIG. 4  is top plan view of the device of  FIG. 3 ; 
       FIG. 5  is a right side elevation view of the device of  FIG. 3 ; 
       FIGS. 6A and 6B  are sectional, side elevation and cross-sectional, front elevation views of the RF ablation probe according to the embodiments of the invention, generally, and in particular the embodiment shown in  FIG. 3 ; 
       FIGS. 7A to 7D  illustrate the use of the RF ablation probe shown in  FIG. 3  to septate myocardial tissue; 
       FIGS. 8 ,  9  and  10  are side elevation, top plan and cross-sectional front views of a second embodiment of an RF ablation probe according to the invention; 
       FIGS. 11 ,  12  and  13  are side elevation, cross-sectional front, and sectional, side elevation views of a third embodiment of an RF ablation probe according to the invention; and 
       FIGS. 14 and 15  are side elevation and top plan views of a fourth embodiment of an RF ablation probe according to a the invention. 
   

   DETAILED DESCRIPTION 
   Overview 
   The embodiments of the invention are directed to probes for ablating tissue to produce lesions, and in particular, to producing elongated linear lesions. The embodiments of the present invention are particularly useful for producing thin linear lesions of epicardial and endocardial tissue to septate the tissue, creating “corridors” to inhibit, minimise or eliminate reentrant pathways in such tissue. The first, second and third embodiments are particularly advantageous in that the probes have a structure enabling them to be readily and easily shaped to conform to the contour and/or irregularities of the surface of a tissue body. 
   The probe has a “memory” capability and will retain its shape when bent. In this way, the probe can be plastically deformed to substantially complement the shape of an irregular surface. In the following description, numerous specific details such as conductive materials for electrodes, specific types of tubing and fillers for probe bodies, specific malleable or plastically deformable materials for providing the above noted memory capability, etc. are described in detail to provide a more thorough description of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments which do not employ the same specific details. Furthermore, well-known and understood aspects and features have not been described in detail so as not to unnecessarily obscure the present invention. 
   FIRST EMBODIMENT 
   A hand-held surgical device  34  incorporating a first embodiment radio frequency (RF) ablation probe according to the invention is illustrated in  FIGS. 3 to 6 . The probe has a malleable tip capable of being bent or deformed and maintaining the shaped configuration thus provided. To effect this, an elongate insulative body  38  of electrically and thermally insulative material is provided with a malleable core  44 , preferably made of a soft metal such as copper and disposed within the insulative body  38 . 
   A linear arrangement of spaced-apart flat electrodes  40  is disposed along the length of one surface of the elongated, insulative body  38  at its distal end. In the embodiment shown, the insulative body  38  is tubular in form and comprises flexible, bendable plastics or rubber material. One or more electrical leads or conductors  42  are connected to each of the electrodes  40  to deliver RF energy from a remote source. Preferably, the conductors  42  pass through the interior of the insulative probe body  38 . Further, the electrical conductors  42  may be used to couple electrical signals from the electrodes to one or more remote devices connected at the opposite end of the probe, for example, to implement mapping of electrical activity in the myocardium. 
   This configuration and assembly of an RF ablation probe is particularly advantageous in that it is readily capable of being shaped and configured so that the linear arrangement of flat electrodes complements the contour and irregularities of a tissue body to be ablated. In particular, the probe can be readily shaped manually by a surgeon to conform to the surface of myocardial tissue and structures observed during surgery. The bendable, malleable characteristics of the RF ablation probe are provided by the malleable core member of the probe so that the probe is adaptable to variously shaped surfaces and has a memory capability to retain its formed shape. 
     FIG. 4  illustrates a top plan view of the hand-held surgical device  30  including the probe structure  38  with the electrodes  40 . The handle  34  is connected at one end by an electrical cable  32  to remote equipment (not shown), including an RF energy generator. Mapping equipment can also be connected to the probe. Temperature control equipment can also be connected to the probe for optimal functioning. The other end of the handle  34  has the adaptable malleable RF ablation probe  38 ,  40  extending therefrom. The probe body  38  has a number of the flat electrodes  40  linearly arranged in the upper surface thereof in a predetermined spaced apart relationship. Preferably, the probe has four rectangular flat electrodes  40 . However, differing numbers of electrodes, e.g.,  3 ,  5 , etc, can be practiced without departing from the scope and spirit of the invention. The arrangement, shape and number of electrodes can be selected to produce elongated lesions of 1 to 10 cm. The long flat shape of the electrodes  40  maximises tissue contact while minimising the thermal momentum of each electrode. The small thickness and low mass of the electrodes  40  allow a respective temperature sensing device such as a thermistor or thermocouple associated with the electrode  40  to measure the true tissue temperature with relative accuracy. 
   As shown in  FIG. 3 , the handle of the hand-held device  34  also incorporates a button switch  36  which can be actuated to deliver RF energy to one or more of the electrodes  40  via internal conductors  42 . While the upper surface of each electrode  40  is flat, a side elevation view of  FIG. 5  illustrates that in this embodiment a number of thin legs are preferably provided on both longitudinal edges of the electrodes  40 . Using such legs, the substantially flat electrode  40  on the upper surface of the probe body  38  can be crimped or otherwise fastened thereto. The terminal ends of the crimping legs shown in  FIG. 3  are generally indicated by the bracket with reference numeral  40 . 
   This embodiment of the invention may be practiced using crimping alone, or in combination with bio-compatible adhesives such as a two-component epoxy resin. The respective under-surfaces of the electrodes  40  can be adhered to the insulative body  38  using such an epoxy resin. The epoxy resin should have a suitable binding strength that remains stable between body temperature and 120° C., if crimping and other mechanical fastening techniques are to be avoided. In the light of the foregoing, it will be apparent to those skilled in the art that other methods of fastening or incorporating electrodes in an insulative body well-known to such persons can be practiced without departing from the scope and spirit of the present invention. 
   The electrodes  40  must be electrically conductive, and preferably are made of metal. Still further, in the embodiment shown, the electrodes  40  are made of stainless steel. However, it will be apparent to one skilled in the art that other materials having high electrical conductivity and capable of withstanding temperatures between room temperature and about 120° C. can be used without departing from the scope and spirit of the invention. 
     FIG. 5  indicates that the RF ablation probe  38 ,  40  can be bent, adapted, shaped or otherwise deformed or deflected as indicated by the arrow in the side elevation view. In particular, the distal end of the probe body  38  having the four electrodes  40  is curved downwardly relative to the position shown in the top plan view of  FIG. 4 . In this embodiment, the stainless steel electrodes  40  incorporated in the distal end of the probe  38  each preferably have dimensions of 4 mm×2.5 mm, with a spacing of 4 mm between each pair of electrodes  40 . Thus, the electrodes  40  have a thin, flat, substantially rectangular form. The malleable tip may preferably be 3 to 6 cm in length. However, other sizes and shapes of electrodes and spacing therebetween may be practiced without departing from the scope and spirit of the invention. Smaller electrodes with equally smaller spacing therebetween may be practiced, thereby offering increased bendability to the probe structure. For example, small square electrodes of 2.5×2.5 mm with inter-electrode distances of 2.5 mm or less may be practiced. 
     FIGS. 6A and 6B  are sectional side elevation and cross-sectional front elevation views, respectively, of the probe  38 ,  40  of  FIGS. 3 to 5 . To simplify the drawing, the crimping legs extending from each of the four electrodes  40  are not illustrated. The malleable member is a copper core  44  included within the insulative body  38  that runs lengthwise along the longitudinal extent of the probe  38 . Arranged along the upper flat surface of the insulative body  38  are four rectangular electrodes  40 . Preferably, each flat electrode  40  has a thermocouple or other temperature sensing device connected therewith for measuring the temperature of the electrode  40 . Thus, one of the electrical leads  42  may be made of a metal conductor such as stainless steel, while the other lead comprises a thermocouple, such as nickel. Alternatively, a thermistor can be connected to the electrode  40  as the temperature sensing device. In each case, the electrical lead(s)  42  is fixedly connected to a respective electrode  40 , and this is preferably done by spot welding. As indicated in  FIG. 6B , the upper surface of the insulative probe body  38  is preferably flat and the electrodes  40  (e.g.,  40 A) are likewise flat. 
   This embodiment of the invention is made by affixing, preferably using an epoxy resin, the flat electrodes  40  to an upper surface of the insulative plastics or rubber-like, hollow tubing  38  and then spot welding each pair of electrical conductors  42  to the respective electrode  40 . This welding also serves to increase the mechanical strength binding the electrodes  40  to the body  38 . The malleable member or core  44  is provided in the hollow interior of the tubular body  38 . The crimping legs shown in  FIGS. 3 and 5 , are then crimped to securely bind the elements  38 ,  40 ,  44  together. In an alternative configuration, prior to crimping of legs, the hollow interior containing the electrical leads  42  and the malleable core  44  can be filled with an insulative, rubbery material such as SILASTIC (trade mark) to form a solid matrix. 
   While the first embodiment of the invention has been described with reference to electrodes formed and bound to the probe body by affixing using adhesive and crimping, it will be readily apparent to one skilled in the art that other techniques can be practiced without departing from the scope and spirit of the invention. Further, rather than affixing or crimping the electrode to an insulative body, where the body itself provides the insulation between electrodes, the insulative portion(s) may be applied separately by, for example, spray coating and silicon layer. 
   USE OF THE FIRST EMBODIMENT 
     FIGS. 7A to 7D  illustrate an exemplary use of the malleable ablation probe  38 ,  40  to produce linear lesions. To septate an interior surface of the right atrium  96 , a small cut  94  is made into the myocardial tissue. A surgeon then illuminates the aperture using a light  92  and observes the interior surfaces of the chamber. Having observed the surface to be ablated, the surgeon shapes, bends or otherwise deforms the RF ablation probe  38 ,  40  so that the malleable tip containing the electrodes  40  conforms with the surface to be ablated. The surgeon can test fit the tip and remove it for minor shape adjustments until a satisfactorily complementary fit is achieved between the tip electrodes and the tissue surface. 
     FIG. 7B  illustrates a reverse “S” shape formed by the RF ablation probe  38 , which is inserted via the aperture  94  into the atrium  96 . The upper surface of the probe  38  containing the electrodes  40  is bent to conform with the contoured inner surface of the atrium  96  and in particular, to take account of the protruding, irregularly shaped mass of tissue  98 . In this manner, a full, solid contact is formed between the flat electrodes  40  and the tissue to be ablated.  FIG. 7C  likewise illustrates an irregularly shaped surface  100  formed in the opposite wall of the atrium. The probe  38  is shown formed into an exaggerated “L” shape with a bend formed in the lower leg of the “L” to conform with the protruding surface  100 . 
   In this manner, a number of elongated lesions can be formed within the interior surface of the atrium  96 , as indicated schematically by solid lines  102  in  FIG. 7D . It will be appreciated by one skilled in the art that the lines  102  represent linear transmural lesions in the interior surface of the atrium  96  as produced in accordance with the use of the malleable probe  38  to ablate endocardial tissue as shown in  FIGS. 7B and 7C . Likewise, the bendable, adaptable RF ablation probe can used to produce elongated, thin lesions from the epicardial surface. 
   SECOND EMBODIMENT 
     FIGS. 8 to 10  illustrate side elevation, top plan and cross-sectional front elevation views of an RF ablation probe according to the second embodiment of the invention. The RF ablation probe  60  comprises a hollow, substantially tubular body  58  made of teflon plastic, a number of flat, conductive electrodes  50 , and a malleable core  54  (not shown in  FIGS. 8 and 9 ) contained within the centre of the thermally and electrically insulative body  58 . In particular, the teflon body  58  has a relatively rigid yet bendable structure and is capable of being permanently formed to have a particular shape. As indicated in  FIG. 8 , the upper surface of the distal end of the tubular body  58  is crimped to produce a flat surface. The electrodes  50  are arranged on the flat upper surface, and again are separated by thermally and electrically insulative material. 
   The electrodes  50  have a like construction to those described hereinbefore with reference to the first embodiment. The flat upper surface of the tubular body  58  provides a complementary surface to that of the underside of each of the electrodes  50  and thereby ensures a solid connection between the two surfaces. Adhesive such as a bio-compatible epoxy resin is preferably used to bond the undersurface of each electrode  50  with the upper flat surface of the tubular body  58 . 
   Still further, it is preferable to weld or incorporate prongs or teeth  56  capable of being bent to the under surface of each electrode  50 . With reference to  FIG. 10 , such prongs or teeth  56  rigidly connected to the under surface of an electrode  50  can be used to puncture the tubular body  58  when the electrode  50  is pressed into contact therewith. Once the teeth or prongs  56  are inserted through the tubular body  58  so that the electrode  50  is in direct contact with the surface of the tubular body  58 , the teeth or prongs  56  are bent within the interior of the body  58  to rigidly interconnect the electrode  50  and the tubular body  58 . This may be done in addition to applying adhesive between the lower surface of the electrodes  50  and the tubular body  58 . 
   With a malleable core  54 , preferably made of copper, inserted within the internal cavity of the tubular body  58 , the internal cavity may then be filled with a sufficiently bendable matrix  52 . Preferably, a rubber like spongy matrix  52  made of SILASTIC (trade mark) or the like is used. It will be apparent to a person skilled in the art, however, that other bendable materials can be used without departing from the scope and spirit of the invention. 
   The RF ablation probe  60  according to the second embodiment may be practiced in numerous ways including the exemplary manner described hereinbefore with reference to  FIGS. 7A to 7D . The second embodiment is advantageous in that it provides a linear arrangement of flat electrodes capable of producing an elongated lesion in a malleable probe structure having a memory function. In particular, the probe may be bent or shaped to conform with an irregular or contoured surface and retain such shape. 
   THIRD EMBODIMENT 
     FIGS. 11 to 13  illustrate an RF ablation probe  70  according to a third embodiment of the invention. Again, a number of flat electrodes  80  are arranged at predetermined spaces on a top surface of an elongate probe body  82 . The body of  82  of the probe is tubular and preferably made of a rubber or soft plastic materials, such as SILASTIC, which is thermally and electrically insulative. Electrical conductors or leads connected to each electrode  80  are not shown in  FIGS. 11 to 12  to simplify the diagram. 
   In this embodiment, rather than having an internal malleable core, a rigid, pre-formed or shaped insert member  84  is inserted into the internal cavity of the tubular body  82  at its distal end to thereby give the probe  70  a corresponding pre-formed shape. The insert member  84  in this example has an S-shape. In  FIGS. 11 and 13 , the pre-formed, rigid, cylindrical insert member  84  is preferably made of stainless steel or a rigid plastic body and can be inserted into the interior cavity of the body  82  to thereby give the probe  70  a corresponding S-like shape. For example, pre-formed insert members  84  can be made to complement the form of known tissue bodies. Alternatively, the insert member  84  can take the form of a deformable material, allowing a surgeon to customise its bent shape prior to use. 
   Using such pre-defined inserts  84 , the flexible probe  70  is provided with a pre-determined shape so as to conform the probe  70  to that shape. The probe  70  can be used to produce linear lesions. 
   FOURTH EMBODIMENT 
     FIGS. 14 and 15  illustrate a forth embodiment of an RF ablation probe  110  for producing elongated, thin linear lesions in a tissue. In this embodiment, the probe  110  consists of a solid, rigid body  112 , preferably having an S or L-shaped terminal region  114  at the distal end. The upper surface of the distal end  114  of the probe  110  is provided with a flat surface. An elongated, flat conductive electrode  116  is provided on the flat surface, and preferably has a rectangular shape. 
   The body  112  of the probe  110  is preferably made of a rigid material such as metal coated with an appropriate insulative material. Alternatively, the probe can be made of plastic and contain electrical conductors preferably internally connected to the electrode  116 . RF energy can be delivered to tissue in contact with the electrode  116 . Further, the temperature of the electrode in contact with tissue can be sensed using a thermocouple or other temperature sensing device connected therewith. Still further, the electrode  116  may be used for detecting or mapping electrical activity in the tissue contacting the electrode  116 . 
   This probe  110  can be used to produce linear, elongated transmural lesions in endocardial and epicardial tissue, and is able to apply or transfer significant pressure between the electrode  116  and the tissue in contact therewith. This ensures that a solid contact is formed with the tissue for delivery of RF energy to the tissue. 
   Only a small number of embodiments of the invention has been described. Changes and/or modifications obvious to one skilled in the art in view of the specification can be made without departing from the scope and spirit of the invention.