turning now to the drawings , in which like reference numerals are used to designate like or corresponding elements among the several figures , in fig1 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 fig1 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 fig1 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 fig1 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 fig2 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 ( fig1 ) 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 fig3 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 ( fig1 ). 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 fig4 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 ( fig1 ) of the previous embodiment . in operation , as shown in fig5 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 ( fig1 ) 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 fig6 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 ( fig1 ) 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 fig7 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 fig8 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 fig1 . 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 fig7 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 fig7 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 fig8 the orifice 100 is positioned such that its center is generally aligned with the axis 87 of the proximal - end region 104 ( fig7 ) 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 ( fig7 ) 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 fig1 . with reference to fig9 a , 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 fig9 b , when tension is applied to the first steering tendon 120 ( fig9 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 fig9 c , when tension is applied to the second steering tendon 122 ( fig9 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 fig1 a , 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 fig1 a , 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 fig1 b , 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 fig1 c , 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 fig8 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 fig1 , 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 fig1 . 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 fig1 . 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 fig1 . 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 fig7 . with reference to fig1 a , 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 ( fig1 ) 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 fig1 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 ( fig1 ) 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 fig1 c , 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 fig1 , 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 fig1 , 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 fig1 , 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 .
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 .