Abstract:
A catheter system includes an outer catheter having a lumen and an inner catheter sized to fit within and slide through the lumen of the outer catheter. Both catheters may be introduced into an anatomical site through a single introduction path. At the distal-end region of each catheter is an electrode system. One electrode system is for mapping the site; the other is for ablating the site. The distal-end regions of one or both of the catheters may be linear shaped, circular shaped, or radially expandable. When the catheter system is deployed the electrode systems carried by the distal-end regions of the mapping catheter and the ablation catheter are movable relative to each other and tend to lie in planes substantially parallel to each other. Another catheter system includes two separate electrode systems on a single expandable member shaped so that both electrode systems come in contact with separate sites.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates generally to an electrophysiological (“EP”) catheter system for use on biological tissue within a biological site, and more particularly, to a combined mapping and ablating catheter system for use in and around the pulmonary veins. 
     The heart beat in a healthy human is controlled by the sinoatrial node (“S-A node”) located in the wall of the right atrium. The S-A node generates electrical signal potentials that are transmitted through pathways of conductive heart tissue in the atrium to the atrioventricular node (“A-V node”) which in turn transmits the electrical signals throughout the ventricle by means of the His and Purkinje conductive tissues. Improper growth of, or damage to, the conductive tissue in the heart can interfere with the passage of regular electrical signals from the S-A and A-V nodes. Electrical signal irregularities resulting from such interference can disturb the normal rhythm of the heart and cause an abnormal rhythmic condition referred to as “cardiac arrhythmia.” 
     Cardiac arrhythmia, including atrial arrhythmia, may be of a multiwavelet reentrant type, characterized by multiple asynchronous loops of electrical impulses that are scattered about the atrial chamber and are often self propagating. In the alternative or in addition to the multiwavelet reentrant type, cardiac arrhythmia may also have a focal origin, such as when an isolated region of tissue in an atrium fires autonomously in a rapid, repetitive fashion. 
     While there are different treatments for cardiac arrhythmia, including the application of anti-arrhythmia drugs, in many cases ablation of the damaged tissue can restore the correct operation of the heart. Such ablation can be performed by percutaneous ablation, a procedure in which a catheter is percutaneously introduced into the patient and directed through an artery or vein to the atrium or ventricle of the heart to perform single or multiple diagnostic, therapeutic, and/or surgical procedures. In such case, an ablation procedure is used to destroy the tissue causing the arrhythmia in an attempt to remove the electrical signal irregularities or create a conductive tissue block to restore normal heart beat or at least an improved heart beat. Successful ablation of the conductive tissue at the arrhythmia initiation site usually terminates the arrhythmia or at least moderates the heart rhythm to acceptable levels. A widely accepted treatment for arrhythmia involves the application of RF energy to the conductive tissue. 
     In the case of atrial fibrillation (“AF”), a procedure published by Cox et al. and known as the “Maze procedure” involves the formation of continuous atrial incisions to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. While this procedure has been found to be successful, it involves an intensely invasive approach. It is more desirable to accomplish the same result as the Maze procedure by use of a less invasive approach, such as through the use of an appropriate EP catheter system providing RF ablation therapy. In this therapy, transmural ablation lesions are formed in the atria to prevent atrial reentry and to allow sinus impulses to activate the entire myocardium. 
     One such EP catheter system, as disclosed in U.S. Pat. Nos. 6,059,778 and 6,096,036, includes a plurality of spaced apart band electrodes located at the distal-end of the catheter and arranged in a linear array. The band electrodes are positioned proximal heart tissue. RF energy is applied through the electrodes to the heart tissue to produce a series of long linear lesions similar to those produced by the Maze procedure. 
     As previously mentioned, cardiac arrhythmia, such as atrial fibrillation, may be focal in nature. The foci, defined by regions exhibiting a consistent and centifugal pattern of electrical activation, may act as either a trigger of atrial fibrillation paroxysmal or may even sustain fibrillation. Such focal arrhythmia are known to originate from a tissue region along the pulmonary veins of the left atrium, and more particularly in the superior pulmonary veins. 
     Procedures for the treatment of focal arrhythmia involving the pulmonary vein generally require the use of two separate catheter systems—a mapping catheter system for locating the foci and an ablation catheter system for ablating the foci. Both catheter systems include their respective mapping or ablation catheter and either a guiding catheter or a guide wire for introducing the catheter into the left atrium of the heart. During a typical procedure, the mapping catheter is first introduced into the left atrium through a puncture in the septum between the right and left atria. The mapping catheter is then guided into the pulmonary vein. While the mapping catheter is still within the heart, the ablation catheter is introduced into the left atrium through either the same puncture as the mapping catheter or a separate puncture. Using the mapping catheter, the foci of the arrhythmia is located using any of several well known mapping techniques. After it is determined that the foci are located within the pulmonary vein, the ablation catheter is positioned either in the pulmonary vein or around the pulmonary vein ostium and the tissue is ablated. The procedure thus described requires the simultaneous placement of two separate catheters into the left atrium through either one or two separate introduction paths. In the case of the left atrium such introduction paths comprise punctures through the atrial septum between the right and left atria. Passing two catheters through a single puncture or two separate punctures increases patient trauma. It also increases the likelihood of damaging the heart through tearing of the septum. 
     Hence, those skilled in the art have recognized a need for a catheter system having two independent catheters, each capable of being introduced into the heart via a single transseptal introduction path. The need for a combined mapping and ablation catheter system for use in the pulmonary vein has also been recognized. The invention fulfills these needs and others. 
     SUMMARY OF THE INVENTION 
     Briefly, and in general terms, the invention is directed to a combination mapping and ablating catheter system for use during electrophysiological procedures in and around various biological sites, including the pulmonary veins. 
     In a first aspect, the invention relates to a catheter system that includes an outer catheter having a lumen therethrough and a distal-end region carrying a first electrode system. The catheter system also includes an inner catheter that is sized to fit within and slide through the lumen of the outer catheter. The inner catheter has a distal-end region carrying a second electrode system. 
     By providing an outer catheter having a lumen through which a separate inner catheter may slide, the invention allows for the simultaneous placement of two separate catheters into a biological site through a signal introduction path. As such, the likelihood of damaging the biological site is substantially reduced. 
     In detailed aspects of the invention, either one or both of the outer catheter and inner catheter further include a tendon having a distal end attached to the distal-end region of the respective catheter and a proximal end exiting the proximal end of the catheter. The tendon is attached such that movement of the tendon along the length of the catheter causes the distal-end region of that catheter to curve. In a another detailed aspect, the outer catheter further comprises a shaped-memory stylet for imparting a preshaped curve to the distal-end region of the outer catheter. In a further detailed aspect, the preshaped curve has a radius of curvature and the catheter further comprises a tendon having a distal end attached to the distal end of the catheter and a proximal end exiting the proximal end of the catheter. The tendon is attached such that movement of the tendon along the length of the catheter decreases the radius of curvature. 
     In another detailed facet of the invention, the outer catheter includes an outer tubular member and an inner tubular member slidably disposed within the outer tubular member. The inner tubular member defines the lumen of the outer catheter. The other catheter also includes a plurality of outwardly bendable segments. The segments are secured at their distal ends to the distal-end region of the inner tubular member and at their proximal ends to the outer tubular member at a point proximal the attachment points of the distal ends. Movement of the inner tubular member in the proximal direction relative the outer tubular member causes the segments to bend outward. 
     In another aspect, the invention relates to a catheter system that includes an outer catheter having tubular wall defining a lumen. The tubular wall includes a sidewall orifice. The outer catheter also includes a distal-end region carrying a first electrode system and a proximal-end region. The catheter system further includes an inner catheter sized to fit within the lumen of the outer catheter and to slide therein. The inner catheter is also sized to fit through the sidewall orifice. The inner catheter has a distal-end region carrying a second electrode system. 
     In a detailed facet of the invention, the tubular member comprises a resiliently deformable junction section between the distal-end region and the proximal end region. The junction section has a normally bent form that generally aligns the center of the sidewall orifice with the axis of the proximal-end region of the tubular wall. In another detailed aspect, the outer catheter further includes a tendon having a distal end attached proximate the inner wall of the tubular member and a proximal end exiting the proximal end of the tubular member. Movement of the tendon along the length of the tubular member causes the distal-end region to deflect about the junction section relative to the proximal-end region. In yet another detailed aspect, the outer catheter includes a shaped-memory stylet for imparting a generally circular curve to the distal-end region of the tubular wall. The curve lies substantially within a first plane. The inner catheter also includes a shaped-memory stylet for imparting a generally circular curve to the distal-end region of the inner catheter. This curve lies substantially within a second plane that is substantially parallel to the first plane. 
     In another detailed facet of the invention the first electrode system and the second electrode system each comprise a plurality of band electrodes positioned along the length of the their respective distal-end region. The catheter system further comprises an alignment system that is adapted to align the curved distal-end region of the inner catheter with the curved distal-end region of the outer catheter such that the band electrodes of the respective catheters are aligned with each other. In a further detailed aspect, the alignment system comprises a pair of markers, each visible under fluoroscopy. One marker is carried on the proximal region of the inner catheter while the other marker is carried on the proximal region of the outer catheter. 
     In another further detailed aspect, the alignment system comprises a groove along the outer surface of the proximal region of the inner catheter and a complementary protrusion along the inner surface of the outer catheter. 
     In another facet, the invention relates to a method of performing an electrophysiological procedure on biological tissue within a biological site. The method includes positioning a first catheter, having a distal-end region carrying a first electrode system, within the biological site proximate the biological tissue. The method further includes sensing electrical activity within the tissue through the first electrode system and processing the electrical activity to identify the origin of an electrophysiological condition. The method further includes guiding a second catheter, having a distal-end region carrying a second electrode system, via the first catheter, into the biological site. The method also includes positioning the second catheter such that the second electrode system is adjacent the identified origin and applying energy to the second electrode system to ablate the identified origin. 
     In a detailed aspect of the invention, the first catheter includes a tubular wall defining a lumen and guiding the second catheter includes sliding the second catheter through the lumen. In a further detailed facet, positioning the second catheter such that the second electrode system is adjacent the identified source includes sliding the second catheter through the lumen until the second electrode system is substantially coincident with the first electrode system and repositioning the first catheter relative the second catheter to expose the second electrode system. In another detailed aspect, the second catheter includes a tubular wall defining a lumen and guiding the second catheter includes sliding the second catheter over the first catheter. In a further detailed aspect, positioning the second catheter such that the second electrode system is adjacent the identified source includes sliding the second catheter over the first catheter until the second electrode system is coincident with the first electrode system. 
     In another facet, the invention relates to a method of performing an electrophysiological procedure on biological tissue proximate a pulmonary vein. The method includes positioning a first catheter, having a distal-end region carrying a first electrode system, near the ostium of the pulmonary vein and guiding a second catheter, via the first catheter, into the pulmonary vein. The second catheter has a distal-end region carrying a second electrode system. The method further includes sensing electrical activity within the pulmonary-vein tissue through the first electrode system, processing the electrical activity to confirm the existence of an abnormal electrophysiological condition originating within the pulmonary vein and upon confirmation, applying energy to the first electrode system to ablate the tissue near the ostium. 
     In a detailed facet of the invention, the first catheter further includes a resiliently deformable shaped-memory stylet for imparting a generally circular curve to the distal-end region of the first catheter and positioning the first catheter near the ostium of the pulmonary vein includes the steps of straightening the distal-end region to allow entry of the distal-end region into the heart, allowing the distal-end region to assume its curved shape and positioning the distal-end region at the ostium such that the curved portion of the region contacts the tissue defining the ostium. In another detailed aspect, the second catheter further includes a resiliently deformable shaped-memory stylet for imparting a generally circular curve to the distal-end region of the second catheter and positioning the second catheter within the pulmonary vein includes the steps of straightening the distal-end region to allow entry of the distal-end region into the pulmonary vein, allowing the distal-end region to assume its curved shape and positioning the distal-end region within the vein such that the curved portion of the region contacts the tissue defining the vein lumen. 
     In another aspect, the invention relates to a catheter system including a catheter sheath carrying a circumferentially expandable member at its distal end. The catheter system further includes a first electrode system positioned on the expandable member and a second electrode system positioned on the expandable member, proximal the first electrode system. 
     In a detailed aspect of the invention, the expandable member includes a distal segment with a first expandable diameter and a proximal segment with a second expandable diameter greater than the first expandable diameter. The first electrode system is positioned at the distal segment and the second electrode system positioned at the proximal segment. In further detailed aspects either one or both of the first electrode system and second electrode system includes a plurality of electrode elements arranged to form a circumferential band around the expandable member. 
     In another aspect, the invention relates to a method of performing an electrophysiological procedure on biological tissue proximate a pulmonary vein. The method includes positioning a circumferentially expandable member having a distal-end region with a first electrode system and a proximal-end region with a second electrode system in the heart such that the distal-end region is at least partially within the pulmonary vein and the proximal-end region is adjacent the tissue defining the ostium of the pulmonary vein. The method also includes expanding the circumferentially expandable member such that the first electrode system contacts the tissue defining the pulmonary vein and the second electrode system contacts the tissue defining the ostium, sensing electrical activity within the pulmonary-vein tissue through the first electrode system and processing the electrical activity to confirm the existence of an abnormal electrophysiological condition originating within the pulmonary vein. The method further includes applying energy to the first electrode system to ablate the tissue near the ostium upon confirmation of the existence of an abnormal electrophysiological condition. 
     These and other aspects and advantages of the invention will become apparent from the following detailed description and the accompanying drawings which illustrate by way of example the features of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 depicts a catheter system configured in accordance with one embodiment of the invention including a mapping catheter slidably positioned within an open-lumen ablation catheter; 
     FIG. 2 depicts the catheter system of FIG. 1 positioned near the ostium of a vein with the ablation catheter retracted to exposed the mapping catheter such that the mapping catheter may locate the focal origin of an arrhythmia; 
     FIG. 3 depicts the catheter system of FIG. 2 positioned near the ostium of a vein with the ablation catheter advanced to coincide with the focal origin previously located by the mapping catheter; 
     FIG. 4 depicts the distal-end region of an alternate configuration of the catheter of FIG. 1 wherein the ablation catheter is slidably positioned within an open-lumen mapping catheter; 
     FIG. 5 depicts the catheter system of FIG. 4 positioned near the ostium of a vein with the mapping catheter advanced over the ablation catheter such that the mapping catheter may locate the focal origin of an arrhythmia; 
     FIG. 6 depicts the catheter system of FIG. 5 positioned near the ostium of a vein with the mapping catheter retracted to allow the ablation catheter to coincide with the focal origin previously located by the mapping catheter; 
     FIG. 7 is a side view with partial cutaway of a catheter system configured in accordance with another embodiment of the invention including an open-lumen ablation catheter having a precurved distal-end region (shown straightened by a guidewire), a steering system and a sidewall orifice and a mapping catheter sized to fit within the ablation catheter and having a normally curved distal-end region (shown straightened); 
     FIG. 8 is an isometric view of the catheter system of FIG. 7 with the distal-end region of the ablation catheter assuming its normally curved shape and the distal-end region of the mapping catheter advanced through the sidewall orifice to assume its normally curved shape; 
     FIG. 9A is a sideview, with partial cutaway of the ablation catheter of FIG. 7 showing the distal-end region in its normally curved state lying in a plane substantially perpendicular to the axis of the proximal-end region of the catheter; 
     FIGS. 9A and 9B are side views of the ablation catheter of FIG. 9A showing the normally curved distal end region deflected by the steering mechanism such that the distal-end region lies in a plane at an angle relative to the axis of the proximal-end region of the catheter. 
     FIG. 10A depicts the catheter system of FIG. 7 deployed near the ostium of a vein with the distal-end region of the ablation catheter straightened by a guidewire; 
     FIG. 10B depicts the catheter system of FIG. 10A with the guidewire removed, the distal-end region of the ablation catheter in its normally curved state and the mapping catheter positioned within the ablation catheter; 
     FIG. 10C depicts the catheter system of FIG. 10B with the distal-end region of the mapping catheter extending through the orifice of the ablation catheter and in its normally curved state; 
     FIG. 11 is a cross-sectional side view of a catheter system configured in accordance with another embodiment of the invention including an open-lumen ablation catheter having an expandable distal-end region (shown collapsed) and a mapping catheter sized to fit within the ablation catheter and having a normally curved distal-end region (shown straightened); 
     FIG. 12 is an isometric view of the catheter system of FIG. 11 with the distal-end region of the ablation catheter expanded and the mapping catheter advanced through the lumen to assume its normally curved shape; 
     FIG. 13A depicts the catheter system of FIG. 11 being deployed near the ostium of a vein with the ablation catheter being guided over a guidewire; 
     FIG. 13B depicts the catheter system of FIG. 13A with the guidewire removed, the distal-end region of the ablation catheter expanded and the mapping catheter positioned within the ablation catheter; 
     FIG. 13C depicts the catheter system of FIG. 13B with the distal-end region of the mapping catheter extending through the top of the ablation catheter to assume its normally curved shape; 
     FIG. 14 depicts a catheter system configured in accordance with another embodiment of the invention having an expandable member (shown collapsed) carrying a mapping electrode system at its distal end and an ablation electrode system near its proximal end; 
     FIG. 15 depicts the catheter of FIG. 14 with the radially expandable member expanded and deployed within a vein; and 
     FIG. 16 depicts a catheter system configured in accordance with another embodiment of the invention having a radially expandable member (shown expanded) and carrying a framework having a mapping electrode system at its distal end and an ablation electrode system near its proximal end. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Turning now to the drawings, in which like reference numerals are used to designate like or corresponding elements among the several figures, in FIG. 1 there is shown a catheter system  10  including an outer ablation catheter  12  having a lumen throughout and an inner mapping catheter  14  configured to fit and slide within the lumen of the outer ablation catheter. The catheters  12 ,  14  may be of various sizes depending on the intended use of the catheter system  10 . In one configuration of a catheter system intended for use within the heart, and particularly, the pulmonary vein, the outer ablation catheter has an outside diameter of 2.39 millimeters (0.094 inches) (7 French) and the inner mapping catheter has an outside diameter of 1.67 millimeters (0.0657 inches) (5 French). 
     Electrically connected to the outer ablation catheter  12  is an energy generator/processor  16 . The energy generator/processor  16  is adapted to provide energy to an ablation electrode system  18  located at the distal-end region  20  of the outer ablation catheter  12  and to monitor the temperature at the ablation electrode system. Electrically connected to the inner mapping catheter  14  is a mapping processor  22  adapted to receive electrical signals from a mapping electrode system  24  located at the distal-end region  26  of the inner mapping catheter. Details regarding the ablation electrode system  18 , the mapping electrode system  24  and their respective electrical connections are provided below. 
     With continued reference to FIG. 1, the inner mapping catheter  14  includes a catheter handle  28  attached to a proximal end  30  of a mapping catheter sheath  32 . Housed within the mapping catheter sheath  32  are a first steering tendon  36  and a second steering tendon  38 . The first steering tendon  36  and the second steering tendon  38  exit the proximal end of the catheter sheath  32  and enter the catheter handle  28 . Within the catheter handle  28 , the first  36  and second  38  steering tendons attach to a steering controller  40 . The distal ends of the steering tendons  36 ,  38  are attached to a distal-end region  26  of the inner mapping catheter  14 . 
     With further reference to FIG. 1, the profile of the distal-end region  26  of the mapping catheter sheath  32  can be adjusted by rotating the steering controller  40 . The steering controller  40  can be rotated by rotating a knob  42  either clockwise or counterclockwise. Rotating the knob  42  clockwise from a neutral position causes one of the steering tendons  36 ,  38  to translate axially in the proximal direction, thus creating a first changed profile  44  of the distal-end region  26 . Similarly, rotating the knob  42  counterclockwise from a neutral position causes the other steering tendon  36 ,  38  to translate axially in the proximal direction, thus creating a second changed profile  46  of the distal-end region  26 . Although FIG. 1 depicts the handle  28  being used with a dual-profile catheter with two steering tendons  36 ,  38 , the handle is also functional for single-profile catheters with a single steering tendon. 
     The ablation electrode system  18  includes one or more band electrodes  48  arranged in a linear array. In a preferred embodiment, the ablation electrode system  18  includes three, 3 millimeter wide band electrodes spaced 4 millimeters apart. A plurality of feed wires (not shown) extend through wire lumen (not shown) running the length of the ablation catheter sheath  34 . The wires are electrically connected to the ablation electrodes  48  at their distal ends and to an electrical connector  49  at their proximal ends. The electrical connector  49  provides the interface between the energy generator/processor  16  and the lead wires. The lead wires transfer energy from the energy generator/processor  16  to the band electrodes  48 . The lead wires may also provide temperature signals to the energy generator/processor  16 . 
     The mapping electrode system  24  includes a plurality of band electrodes  50  and a tip electrode  51  arranged in a linear array. The band electrodes  50  are spaced close together for high resolution and in a preferred embodiment includes eight 1 millimeter wide band electrodes spaced 1 millimeter apart. A plurality of lead wires (not shown) extend through the mapping catheter sheath  32 . The wires are electrically connected to the mapping electrodes  50 ,  51  at their distal ends and to an electrical connector (not shown) at the rear of the handle  28  at their proximal ends. The electrical connector provides the interface between the mapping processor  22  and the lead wires. The lead wires transfer electrical signals to the mapping processor. 
     To assist in steering the catheter system  10  through the patient&#39;s vascular system and to assure proper placement of the ablation electrode system  18 , the distal-end region  26  of the mapping catheter sheath  32  is made more rigid than the distal-end region  20  of the ablation catheter sheath  34 . This may be accomplished, for example, by forming the distal-end region  26  of the mapping catheter sheath  32  of a higher durometer than the distal-end region  20  of the ablation catheter sheath  34 . As such, the distal-end region  20  of the outer ablation catheter  12  assumes the shape of the distal-end region  26  of the inner mapping catheter  14 . 
     To prevent fluid from entering the space between the inside wall of the outer ablation catheter  12  and the outside surface of the inner mapping catheter  14 , a seal (not shown) is included in the outer ablation catheter. The seal is a soft rubber short-length tubing or O-ring formed of an elastomeric material, e.g., silicon, Santoprene, Viton, and is adhered to the inside diameter of the outer ablation catheter  12  lumen near the distal end. The seal forms a tight seal against the outer surface of the inner mapping catheter  14 . The seal is pliable enough to allow for movement of the outer ablation catheter  12  relative to the inner mapping catheter  14  yet rigid enough to function as a seal. The outer ablation catheter  12  also includes a locking mechanism  47  for locking the outer ablation catheter to the inner mapping catheter  14 . An example of one such locking mechanism is described in U.S. application Ser. No. 09/746,721 the disclosure of which is hereby incorporated by reference. 
     While the operational descriptions to follow focus on the use of the catheter system  10  for treating focal arrthymias originating within and around the pulmonary vein, the system may be used for treatment of other locations both within and outside of the heart. For procedures not involving the pulmonary vein, the catheter system  10  may be initially placed within the subject biological site using the steering system of the inner mapping catheter  14 . In such placement procedures, the outer ablation catheter  12  and the inner mapping catheter  14  are positioned relative each other such that their distal ends are substantially aligned. The catheters  12 ,  14  are then introduced into a patient&#39;s vascular system and are guided therethrough and into the desired biological site, using the mapping catheter&#39;s steering system. For procedures involving the pulmonary vein, the catheter system  10  may be initially placed within the left atrium through a transseptal approach using a guiding sheath (not shown). Once positioned, the guiding sheath and the catheter system  10  are moved relative to each other to expose the distal end regions  20 ,  26  of the catheter system  10 . 
     With reference to FIG. 2, once the outer ablation catheter  12  and the inner mapping catheter  14  are positioned in the left atrium near the pulmonary vein  52 , the outer ablation catheter is retracted in the proximal direction relative to the inner mapping catheter to expose the distal-end region  26  of the inner mapping catheter. The distal-end region  26  is guided into the vein and is positioned against the tissue  56  defining the vein lumen. The profile of the distal-end region  26  of the inner mapping catheter  14  may be deflected using the steering system to ensure better contact between the mapping electrode system  24  and the tissue  56 . Electrical signals traveling through the tissue  56  are sensed by the mapping electrode system  24  and are sent to the mapping processor  22  (FIG. 1) for analysis. The mapping electrode system  24  is repositioned and then the process is repeated until the foci  54  of the arrthymia are located. 
     With reference to FIG. 3, once the foci  54  are located, the outer ablation catheter  12  is advanced distally over the inner mapping catheter  14  until the ablation electrode system  18  is at or near the foci  54 . Because the distal-end region  20  of the outer ablation catheter  14  is more pliable than the inner mapping catheter  12 , it assumes the shape of the mapping catheter and is thus placed at or near the foci  54 . In a preferred embodiment, markers (not shown) are placed on both the inner mapping catheter  14  and outer ablation catheter  12 . Under fluoroscopy, the markers are used to align the ablation electrode system  18  with the mapping electrode system  24  and hence with the foci  54 . Once properly positioned, energy is applied to the ablation electrode system  18  from the energy generator/processor  16  (FIG.  1 ). In a preferred embodiment the energy generator/processor  16  provides RF energy. In alternate embodiments, other forms of energy may be applied such as cyroablation, light, radiation, laser and any other energy capable of permanently disrupting the electrical continuity of the pulmonary vein  52 . In the embodiment shown, the RF energy passes through the ablation electrode system  18  into the tissue  56  at or near the foci  54  to ablate the tissue. 
     With reference to FIG. 4, in an alternate configuration of this embodiment of the invention, the catheter system  10  includes an inner ablation catheter  58  having an ablation electrode system  60  and an outer mapping catheter  62  having a mapping electrode system  64 . The inner ablation catheter  58  includes a steering mechanism like that described with reference to the inner mapping catheter  14  (FIG. 1) of the previous embodiment. 
     In operation, as shown in FIG. 5, once the outer mapping catheter  62  and the inner ablation catheter  58  are positioned in the heart, the distal-end region  66  of the outer mapping catheter  62  is guided into the vein  52  and is positioned against the tissue  56  defining the vein lumen. Electrical signals traveling through the tissue  56  are sensed by the mapping electrode system  64  and are sent to the mapping processor  22  (FIG. 1) for analysis. The mapping electrode system  64  is repositioned and then the process is repeated until the foci  54  of the arrthymia are located. 
     With reference to FIG. 6, once the foci  54  are located, the outer mapping catheter  62  is retracted proximally relative to the inner ablation catheter  58  to expose the ablation electrode system  60  at or near the foci  54 . The distal-end region  68  of the inner ablation catheter  58  is positioned such that it contacts the tissue  56  at or near the foci  54 . The distal-end region  68  of the ablation catheter  58  may be deflected using the steering system to ensure adequate contact between the ablation electrode system  60  and the tissue  56 . Once adequately positioned, energy is applied to the ablation electrode system  60  by the energy generator/processor  16  (FIG. 1) to ablate the tissue  56  at or near the foci  54 . 
     In other embodiments of the invention the catheter system includes an ablation catheter that is specially configured to ablate a circumferential band of tissue near the entry of the pulmonary vein lumen. A “circumferential band” as used herein is a continuous line that is traced around a region of space and which starts and ends at substantially the same location. The catheter system also includes a mapping catheter that is also specially configured to circumscribe a band of tissue within the vein lumen. 
     With reference to FIG. 7 one such catheter system  80  includes an outer ablation catheter  82  having a tubular wall  84  defining a lumen  86 . The lumen  86  extends between the distal end  88  and proximal end (not shown) of the tubular wall  84 . The tubular wall  84  has a distal-end region  90  that carries an ablation electrode system  92 . In a preferred embodiment, the ablation electrode system  92  includes a plurality of band electrodes  94  and a tip electrode  96 . The lumen  86  extends through the tip electrode  92  to allow for placement of the ablation catheter  82  over a guidewire  98 . In an alternate configuration the ablation catheter  82  is guided through a sheath. In such a configuration, the need to extend the lumen  86  through the tip electrode  92  is eliminated. The tubular wall  84  includes an orifice  100  positioned within a junction section  102  located between the distal-end region  90  and the proximal-end region  104 . 
     The catheter system  80  further includes an inner mapping catheter  106  configured to fit into and slide within the lumen  86  of the outer ablation catheter  80  and to fit through the orifice  100  contained within the tubular wall  84 . The inner mapping catheter  106  includes a tubular wall  108  having a distal-end region  110  that carries a mapping electrode system  112 . In a preferred embodiment, the mapping electrode system  112  includes a plurality of band electrodes  114  and a tip electrode  116 . 
     As shown in FIG. 8, the distal-end regions  90 ,  110  of both the ablation catheter  82  and the mapping catheter  106  respectively are formed such that they normally assume an arc shape that nearly forms a complete circle having a radius of curvature. The respective arcs formed in the distal-end regions  90 ,  110  each lie in a plane substantially parallel to each other. When the distal-end regions  90 ,  110  assume their normally arced shape, the electrodes  114 ,  116  carried by the mapping catheter  106  and the electrodes  94 ,  96  carried by the ablation catheter  82  circumscribe a predefined circle or partial circle. The arc of the ablation catheter  82  is sized to fit around all or part of a vein ostium while the arc of the mapping catheter  110  is sized to fit within the vein. Catheters having different sized arcs may be used depending on the particular anatomy being treated. In one embodiment, the arc shape is provided by shaped-memory nitinol stylets (not shown) carried within the tubular walls  84 ,  108  of the catheters at the distal-end regions  90 ,  110 . Alternatively, the shaped-memory may be provided by heat-setting the polymer of the catheter. 
     In an alternate configuration, the tubular walls  84 ,  108  of the catheters each include a lumen (not shown) that carries a tendon  85 ,  109 . The distal end of the ablation catheter tendon  85  is attached to the distal tip of the tubular wall  84  near the tip electrode  96 . Likewise, the distal end of the mapping tendon  109  is attached to the tubular wall  108  near the tip electrode  116 . The proximal end of each tendon  85 ,  109  is attached to a steering mechanism, such as that shown in FIG.  1 . Applying tension to the tendons  85 ,  109  along the length of the catheter shaft causes the radius of curvature of the respective distal-end regions  90 ,  110  to tighten, i.e., become smaller. Subsequent removal of tension from the tendons  85 ,  109  allows the distal-end regions  90 ,  110  to assume their preformed radius of curvature. 
     Though configured to normally assume their arced shapes, the distal-end regions  90 ,  110  of both catheters  82 ,  106  are resiliently deformable and may assume a linear shape when forced to. More specifically, as shown in FIG. 7, the distal-end region  90  of the ablation catheter  82  assumes a linear shape when it is positioned over a guidewire  98 . With regard to the mapping catheter  106 , its distal-end region  110  assumes a linear shape when it is positioned within the lumen  86  of the ablation catheter  82 . 
     With continued reference to FIG. 7, the junction section  102  positioned between the distal-end region  90  and the proximal-end region  104  of the ablation catheter  82  is formed of a resiliently deformable material, such as Pebax, Nylon or Urethane. The junction section  102  is normally bent to an angle of approximately 90 degrees. When the junction section  102  is in its normally bent form, as shown in FIG. 8, the orifice  100  is positioned such that its center is generally aligned with the axis  87  of the proximal-end region  104  (FIG. 7) of the tubular wall  84 . The mapping catheter  106  is similarly configured to include a bend like that of the ablation catheter  82 . 
     In a preferred embodiment, the ablation catheter  82  (FIG. 7) includes a steering mechanism for deflecting the distal-end region  90 . In one configuration, the steering mechanism includes an anchor band  118  positioned within the junction section  102 , proximal to the orifice  100 . The anchor band  118  is secured to the inner surface of the junction section  102  or to a support mechanism (not shown) attached to the distal-end region  90 . The steering mechanism further includes a first steering tendon  120  and a second steering tendon  122 , each attached at their distal ends to the anchor band  118 . The proximal ends of the tendons  120 ,  122  exit the proximal end of the tubular wall  84  where they are attached to a steering controller similar to that shown in FIG.  1 . 
     With reference to FIG. 9A, when the steering controller is in a neutral position, i.e., no tension is applied to either tendon  120 ,  122 , the arc formed by the distal-end region  90  of the ablation catheter  82  lies in a plane substantially perpendicular to the axis  87  of the proximal-end region  104 . With reference to FIG. 9B, when tension is applied to the first steering tendon  120  (FIG.  9 A), the arc formed by the distal-end region  90  of the ablation catheter  82  is deflected in a first direction such that the arc lies in a plane at an angle relative to the axis  87  of the proximal-end region  104 . With reference to FIG. 9C, when tension is applied to the second steering tendon  122  (FIG.  9 A), the arc formed by the distal-end region  90  of the ablation catheter  82  is deflected in a second direction, opposite the first direction, such that the arc lies in a plane at an angle relative to the axis  87  of the proximal-end region  104 . 
     With reference to FIG. 10A, in operation, the ablation catheter  82  is introduced into a patient&#39;s vascular system and is guided therethrough and into the heart using a guidewire  98 . As is meant to be shown in FIG. 10A, the catheter  82  has been advanced into the left atrium of the patient&#39;s heart through the septum, and is now directed towards the pulmonary vein that connects to the left atrium of the heart. Alternatively, the ablation catheter  82  may be guided into the heart through a sheath. With reference to FIG. 10B, once the ablation catheter  82  is positioned in the heart, the ablation catheter and guidewire  98  are moved relative each other such that the distal-end region  90  of the ablation catheter  82  is no longer constrained to a straight position by the guidewire and assumes its normally arced shape. The ablation electrode system  92  is then positioned at the ostium  124  of the pulmonary vein. Once the ablation electrode system  92  is positioned, the mapping catheter  106  is guided through the lumen  86  of the ablation catheter  82  toward the orifice  100  in the tubular wall  84 . As previously mentioned, the distal-end region  110  of the mapping catheter  106  is formed of a material less rigid than the proximal-end region of ablation catheter  82 . As such the normally arced shape of the distal-end region  10  assumes the shape of the proximal-end region  104  of the ablation catheter  82 . 
     As shown in FIG. 10C, as the distal-end region  110  of the mapping catheter  106  passes through the orifice  100  and is no longer constrained by the proximal-end region  104  of the ablation catheter  82 , it assumes its normally arced shape. The distal-end region  110  is advanced into the pulmonary vein  126  until the mapping electrode system  112  contacts the tissue  128 . Electrical signals, i.e., pulmonary vein potentials, are sensed by the mapping electrode system  112  and sent to the mapping processor where they are analyzed to determine if the pulmonary vein contains an arrthymogenic origin for atrial arrhythmia. 
     If it is determined that the pulmonary vein contains an arrthymogenic origin  130 , the ablation electrode system  92  is positioned such that it circumferentially engages the tissue around the pulmonary vein ostium  124 . Energy is then applied to the ablation electrode system  92  to ablate the tissue around the ostium  124  to thereby form a circumferential lesion  132  which blocks electrical conduction from the arrthymogenic origin  130  along the pulmonary vein  126  wall into the left atrium. To ensure the formation of a continuous circumferential lesion  132 , energy may be applied to the ablation electrode system  92  using a combination unipolar/bipolar technique and/or phasing technique such as that described in U.S. Pat. Nos. 6,050,994, 6,059,778 and 6,171,305, the disclosures of which are hereby incorporated by reference. 
     With reference to FIG. 8, in a preferred embodiment of the catheter system  80  the distal-end region  110  of the mapping catheter  106  and the distal-end region  90  of the ablation catheter  82  may be positioned relative each other such that the mapping electrodes  114 ,  116  align with the ablation electrodes  94 ,  96 . Specifically, the catheter mapping electrodes may be positioned such that the tip electrode  116  aligns with the ablation tip electrode  96 , the mapping band electrode  114  adjacent the mapping tip electrode aligns with the ablation band electrode  94  adjacent the ablation tip electrode and so on. Alignment of the electrodes  94 ,  96 ,  114 ,  116  may be accomplished using a marker visible under fluoroscopy located on the shafts of the catheter. Using a marker allows for the mapping catheter  106  and the ablation catheter  82  to rotate relative each other. 
     Alternatively, alignment of the electrodes  94 ,  96 ,  114 ,  116  may be accomplished by a guide system carried by the catheter system. The guide system may include a linear groove (not shown) along the interior of the proximal-end region  104  of the ablation catheter  82  and a complimentary linear protrusion (not shown) along the exterior of the proximal-end region of the mapping catheter  106 . During deployment of the mapping catheter  106  through the ablation catheter  82 , the protrusion is positioned within the groove to align the catheter such that their respective electrodes are aligned. Alternatively, the groove may be carried by the mapping catheter  106  and the protrusion by the ablation catheter  82 . In this case, the catheters  82  and  106  are not free to rotate relative to each other. 
     With reference to FIG. 11, in another embodiment of the invention, a catheter system  140  includes an outer ablation catheter  142  having an expandable ablation electrode system  144 . The ablation catheter  142  includes an outer tubular member  146  and an inner tubular member  148  slidably disposed within the outer tubular member. The inner tubular member  148  defines an outer-catheter lumen  150 . The outer ablation catheter  142  further includes a plurality of outwardly bendable segments  152  that, in this embodiment, take the form of elongated strips. Each segment  152  is secured at its distal end  154  to the distal end  156  of the inner tubular member  148  and at its proximal end  158  to the outer tubular member  146  at a point proximal the attachment points of the distal ends. Configured as such, movement of the inner tubular member  148  in the proximal direction relative the outer tubular member  146  causes the segments  152  to bend outward, as shown in FIG.  12 . The width of the strips  152  depends on the number required to be placed about the catheter. The more strips that are required, the narrower each one may be. However, there may be a maximum width regardless of how few strips exist. Further, the strips may not be “elongated” but may be shorter in length depending on the radius desired to be obtained when the strips are bent outward. 
     An ablation electrode  160  is located on each of the segments  152 . Lead wires (not shown) run the length of the ablation catheter  142  and connect the ablation electrodes  160  to an energy generator/processor such as that shown in FIG.  1 . The lead wires are carried by a lumen (not shown) contained within the outer tubular member  146  and the bendable segments  152 . 
     The catheter system  140  further includes an inner mapping catheter  162  configured to fit and slide within the outer-catheter lumen  150 . The inner mapping catheter  162  includes a tubular wall  164  having a distal-end region  166  that carries a mapping electrode system  168 . In a preferred embodiment, the mapping electrode system  168  includes a plurality of band electrodes  170  and a tip electrode  176 . The distal-end region  166  of the tubular wall  164  has shaped-memory properties and is formed to normally assume an arc shape that nearly forms a complete circle as shown in FIG.  12 . The distal-end region  166  of the mapping catheter  162  is less rigid than the inner tubular member  148  of the ablation catheter  142  and assumes the shape of the inner tubular member when it is positioned therein. The configuration of the mapping catheter  162  is similar to that of FIG.  7 . 
     With reference to FIG. 13A, in operation, the ablation catheter  142  is introduced into a patient&#39;s vascular system and is guided therethrough and into the heart using a guidewire  174 . Alternatively, the ablation catheter  142  may be guided into the heart through a sheath. Once the ablation catheter  142  is positioned in the heart, the guidewire  174  is removed and the inner tube  148  (FIG. 11) of the ablation catheter  142  is retracted relative to the outer tube  146 , thereby causing the ablation electrode system  144  to assume its expanded form as shown in FIG.  13 B. The ablation electrode system  144  is then positioned at the ostium  124  of the pulmonary vein  126 , such that the ablation electrodes  160  contact the tissue  128 . 
     Once the ablation electrode system  144  is positioned at the pulmonary vein ostium, the mapping catheter  162  is guided through the lumen  150  (FIG. 11) of the ablation catheter  142 . As previously mentioned, the mapping catheter  162  is formed of a material less rigid than the inner tubular member  148  of the ablation catheter  142 , as such the normally arced shape of the distal-end region assumes the shape of the inner tubular member  148 . 
     As shown in FIG. 13C, as the distal-end region  166  of the mapping catheter  162  passes through the top of the inner tubular member  148 , it assumes its normally curved shape. The distal-end region  166  is advanced into the pulmonary vein until the mapping electrode system  168  contacts the tissue  128 . Electrical signals are sensed by the mapping electrode system  168  and sent to a mapping processor where they are analyzed to determine if the pulmonary vein contains an arrthymogenic origin for atrial arrhythmia. 
     If it is determined that the pulmonary vein contains an arrthymogenic origin  130 , the ablation electrode system  144  is positioned to ensure that it circumferentially engages the tissue around the pulmonary vein ostium  124 . Energy is then applied to the ablation electrode system  144  to ablate the tissue around the ostium  124  to thereby form a circumferential lesion  132  which blocks electrical conduction from the arrthymogenic origin  130  along the longitudinal axis of the pulmonary vein  126  wall into the left atrium. To ensure the formation of a continuous circumferential lesion  132 , energy may be applied to the ablation electrode system  144  using a combination unipolar/bipolar technique and/or phasing technique such as those described in U.S. Pat. Nos. 6,050,994, 6,059,778 and 6,171,305, the disclosures of which are hereby incorporated by reference. 
     With reference to FIG. 14, in another embodiment of the invention, a catheter system  200  includes a catheter shaft  202  having a radially expandable member  204  at its distal end. In one configuration, the expandable member  204  comprises an inflatable balloon having a distal-end region  206  and a proximal-end region  208 . The balloon  204  is configured such that when it is inflated, the outside diameter of the distal-end region  206  is less than the outside diameter of the proximal-end region  208 . A plurality of mapping electrodes  210  arranged in an array at the distal end of the balloon  204  form a mapping electrode system  212 . The mapping electrodes  210  may comprise a metallic material deposited on the outer surface of the balloon using known techniques, such as but not limited to plasma depositing, sputter coating or chemical vapor deposition. An ablation electrode system  214  is positioned at the proximal-end region  208  of the balloon  204 . The ablation electrode system  214  may comprise one or more ablation electrodes  216  arranged to form a circumferential band around the balloon  204 . The ablation electrodes  216  may comprise a metallic material deposited on the outer surface of the balloon  204 . 
     The catheter shaft  202  includes a lumen that allows for deployment of the catheter system  200  over a guide wire  218 . Alternatively, the catheter system  200  may be deployed through a guiding sheath. 
     With reference to FIG. 15, in operation, the distal end of the catheter system  200  is guided by a guide wire  218  to the interior of the pulmonary vein  126 . Once properly positioned, the balloon  204  is inflated to a level sufficient to force contact between the mapping electrode system  212  and the circumferential wall of the vein  126 . The mapping electrodes  210  sense pulmonary vein potentials throughout the circumference and depth of the pulmonary vein  126  and pass them to a mapping processor to determine if the pulmonary vein contains an arrthymogenic origin for atrial arrhythmia. 
     If it is determined that the pulmonary vein contains an arrthymogenic origin  130 , the balloon is further inflated to force contact between the ablation electrode system  214  and the tissue around the pulmonary vein ostium  124 . Energy is then applied to the ablation electrode system  214  to ablate the tissue around the ostium  124  to thereby form a circumferential lesion  132  which blocks electrical conduction from the arrthymogenic origin  130  along the longitudinal axis of the pulmonary vein  126  wall into the left atrium. To ensure the formation of a continuous circumferential lesion  132 , energy may be applied to the ablation electrode system  214  using a combination unipolar/bipolar technique and/or phasing technique such as that described in U.S. Pat. Nos. 6,050,994, 6,059,778 and 6,171,305, the disclosures of which are hereby incorporated by reference. 
     In the configuration thus described, a single balloon is used to deploy both the mapping electrode system and the ablation electrode system. In alternate configurations (not shown) of this embodiment, the catheter system employ multiple balloons. A first balloon deploys the mapping electrode system while a second balloon deploys the ablation electrode system. 
     With reference to FIG. 16, in another embodiment of the catheter system  240 , the expandable member  242  comprises a matrix framework  244  or mesh positioned on an inflatable device  246 , such as a balloon. The framework  244  is secured to the balloon  246  through known adhesive bonding techniques and is expanded by inflation of the balloon. The construction of the framework  244  determines the size of its expansion. Specifically, a more “loose” framework  244  allows for greater expansion. Mapping electrodes  248  and ablation electrodes  250  are mounted on the framework  244  at the distal-end region  252  and the proximal-end region  254 , respectively to define a mapping electrode system  256  and an ablation electrode system  258 . The ablation electrodes  250  are positioned adjacent each other in a single row around the balloon  246  to form a circumferential electrode band. By using only a single row of electrodes  250 , a narrow ablation band is provided, as such, the ablation site is localized and the risk of pulmonary vein stenosis is minimized. In alternative configurations, more rows of ablation electrodes  250  may be added to increase the width of the ablation band circumference. The mapping electrodes  248  and ablation electrodes  250  are isolated from each other by insulating coatings on the balloon  246  and/or on the framework  244 . 
     In one configuration, the framework  244  includes metallic and non-metallic portions. A first metallic portion contains the mapping electrodes  248  while a second metallic portion contains the ablation electrodes  250 . Conductive wires carried by the metallic portions serve as lead wires between the electrodes  248 ,  250  and the catheter shaft  262 . The lead wires are carried within the wall of the expandable member  242  and into the catheter shaft  262 . For a configuration deployed using a guidewire  264 , the lead wires are carried by the wall of the catheter shaft  262  to the proximal end of the catheter. The metallic portions are separated by a non-metallic portion  260 . In a preferred embodiment, the non-metallic portion is formed from PTFE or other non-thrombogenic material. 
     In alternate configurations, deployment of the framework could be through the use of mechanical means such as a spring tension or a deployment tendon/wire to expand and contract the framework. 
     It will be apparent from the foregoing that while particular forms of the invention have been illustrated and described, various modifications can be made without departing from the spirit and scope of the invention. Accordingly, it is not intended that the invention be limited, except as by the appended claims.