the following description of preferred embodiments of the invention is not intended to limit the invention to these embodiments , but rather to enable any person skilled in the art to make and use this invention . as shown in fig1 a and 2 , the system 10 of the preferred embodiments includes an elongate member 12 and a positioning mechanism 14 coupled to the elongate member 12 . the elongate member 12 may be radiopaque to allow it to be seen during fluoroscopy . this may be achieved with radiopaque marker bands or by including radiopaque filler materials in the elongate member such as barium sulfate or titanium dioxide . the positioning mechanism 14 performs one or more of the following functions : ( a ) facilitate locating an anatomical structure ( preferably a pulmonary vein 3000 in a left atrium of a heart 3002 , but alternatively any other suitable anatomical structure ), ( b ) anchor the elongate member 12 with respect to the anatomical structure , and ( c ) electrically stimulate and / or sense electrical signals from the anatomical structure . the system 10 is preferably designed for positioning an elongate member within a patient and , more specifically , for positioning a therapy and / or navigation catheter with respect to a pulmonary vein in the left atrium of the heart of a patient . the system 10 , however , may be alternatively used in any suitable environment and for any suitable reason . the elongate member . the elongate member 12 of the preferred embodiments is a catheter made of a flexible multi - lumen tube , but may alternatively be a cannula , tube or any other suitable elongate structure having one or more lumens . the elongate member 12 preferably has a separate lumen that houses the positioning mechanism 14 , but may alternatively house the positioning mechanism 14 in any other suitable configuration . the elongate member 12 preferably houses a single positioning mechanisms 14 ( as shown in fig1 a ), but may house more than one positioning mechanisms ( as shown in fig2 ). the elongate member 12 of the preferred embodiments functions to accommodate pull members , fluids , gases , energy delivery structures , electrical connections , therapy catheters , navigation catheters , pacing catheters , and / or any other suitable device or element . as shown in fig2 , the elongate member 12 preferably includes a distal tip assembly 16 positioned at a distal portion of the elongate member 12 . the distal tip assembly 16 preferably houses an energy delivery structure 18 that functions to deliver energy 20 to tissue , such as tissue of a heart 3002 . the energy delivery structure 18 preferably includes an ultrasound transducer subassembly , but may alternatively include any other suitable source of ablation energy such as radio frequency ( rf ) energy , microwaves , photonic energy , and thermal energy . ablation could alternatively be achieved using cooled fluids ( e . g ., cryogenic fluid ). the positioning mechanism . as shown in fig1 a and 1b , the positioning mechanism 14 of the preferred embodiments is coupled to a distal portion of the elongate member 12 . as shown in fig1 a , the positioning mechanism 14 is preferably coupled to the distal tip of the elongate member 12 . the positioning mechanism 14 is preferably coupled to the distal tip of the elongate member 14 such that fluid ( for cooling the energy delivery system 18 or for cooling the tissue , for example ) is able to flow through a lumen in the elongate member 12 and exit out of the elongate member as necessary . alternatively , as shown in fig1 b , the positioning mechanism 14 is preferably coupled to the side of the elongate member 12 near the distal end of the elongate member 12 . in some variations , the positioning member 14 is retractable into and exits from the elongate member 12 through the distal end or through a notch 22 near the distal end of the elongate member 12 . in these variations , the positioning member 14 preferably is held in or moves to a smaller configuration ( by folding , straightening , etc .) such that it fits within the elongate member 12 . the positioning member , when residing completely inside a lumen of the elongate member 12 , is preferably held in a generally straight shape , conforming to confines of the lumen . as the positing member 14 is advanced outwards , and / or as it exits the notch 22 , it preferably takes on a predetermined shape , for example as shown in fig1 b , 5 , and 11 . as shown in fig2 , the positioning mechanism 14 of the preferred embodiments performs one or more of the following functions : ( a ) facilitate locating an anatomical structure , ( b ) anchor the elongate member 12 with respect to the anatomical structure , and ( c ) electrically stimulate and / or sense electrical signals from the anatomical structure . regarding the first function , the positioning mechanism 14 facilitates locating an anatomical structure by providing an indication of where the positioning mechanism 14 is with respect to the anatomical structure . the indication is preferably a visual indication ( via a medical imaging system such as a fluoroscope ), but is alternatively or additionally a tactile indication 50 or audible indication 51 . fig2 also illustrates visualization of the anatomic structure 52 . additionally , the elongate member 12 and / or the positioning mechanism 14 may include indicia , such as markings indicating distance , that indicate the location of the anatomical structure and / or to indicate the depth of insertion of the system 10 where the anatomical structure was located . regarding the second function , the positioning mechanism 14 anchors the elongate member 12 with respect to the anatomical structure by coupling to a portion of an anatomical structure ( for example a pulmonary vein 3000 and / or a left atrium 3002 of a heart ) and by providing stabilization of the elongate member 12 when manipulating at least a portion of the elongate member 12 and / or by providing an axis of rotation to the elongate member 12 as it is rotated . the elongate member 12 is preferably manipulated to position the energy delivery structure 18 within the left atrium of the heart 3002 ( or in any other suitable location ) and , once positioned there , is preferably manipulated to move the energy delivery structure 18 along an ablation path and to direct the energy delivery structure 18 towards tissue to provide a partial or complete zone of ablation along the ablation path . the ablation path preferably has any suitable geometry or geometries to provide a conduction block — isolation and / or block of conduction pathways of abnormal electrical activity , which typically originate from the pulmonary veins in the left atrium — for treatment of atrial fibrillation in a patient , but may alternatively provide any other suitable therapy . a linear ablation path is preferably created by moving and bending the elongate member 12 in an x , y , and / or z direction . a generally circular or elliptical ablation path 30 is preferably created by rotating the elongate member 12 about an axis . the elongate member 12 is preferably rotated in one of several variations . in a first variation , as shown in fig2 , the elongate member is rotated , as shown by arrow 3010 , around the two positioning mechanisms 14 , the energy delivery structure 18 preferably sweeps a generally circular ablation path 30 . the two positioning mechanisms 14 preferably assure that the rotation of the elongate member 12 and therefore the energy delivery structure 18 will occur in an ablation path 30 outside of the pulmonary veins 3000 and 3000 ′. the ablation path 30 may alternatively encircle a single pulmonary vein or encircle any other suitable number of pulmonary veins . in a second variation , as shown in fig3 , the elongate member is rotated , as shown by arrow 3012 , within the pulmonary vein 3000 such that the energy delivery structure 18 preferably sweeps a generally circular ablation path 30 , generally perpendicular to the axis of the pulmonary vein 3000 . in an alternative version of this second variation , the elongate member may alternatively be located outside of and adjacent to the pulmonary vein while still generally perpendicular to the axis of the pulmonary vein 3000 . the elongate member is preferably rotated such that the energy delivery structure 18 preferably sweeps a generally circular ablation path 30 around at least one ostium of a pulmonary vein . in this version of the second variation , the energy delivery structure 18 is preferably angled such that it is preferably at an acute angle with respect to the axis of the elongate member and such that the energy delivery structure preferably points and delivers energy 20 substantially towards the atrial wall and around the pulmonary vein ostium . in the second variation , the energy delivery structure 18 preferably rotates within the distal tip assembly 16 , delivering ablation energy though a window that runs around the circumference of the distal tip assembly 16 . the window is preferably made of a material that is transparent to ultrasound waves such as a poly 4 - methyl , 1 - pentene ( pmp ) material or may alternatively be an open window . alternatively , the elongate member 12 and / or distal tip assembly 16 may rotate , rotating the energy delivery structure within . the positioning mechanism 14 preferably does not rotate along with the elongate member 12 and / or the distal tip assembly 16 . in a third variation , as shown in fig4 , the positioning mechanism 14 is pressed against a portion of a heart chamber ( such as the ceiling wall of the left atrium ), or in any other suitable location and the elongate member 12 is rotated , as shown by arrow 3014 , around the axis created by the positioning mechanism 14 , the energy delivery structure 18 preferably sweeps a generally circular ablation path outside of the pulmonary veins 3000 and 3000 ′. the ablation path may alternatively encircle a single pulmonary vein or any other suitable number of pulmonary veins . in all variations , the energy delivery structure is preferably positioned with respect to the tissue at an appropriate angle . the energy delivery system is preferably directed towards the target tissue at an angle between 20 and 160 degrees to the tissue , more preferably at an angle between 45 and 135 degrees to the tissue , and most preferably at an angle of 65 and 115 degrees to the tissue . regarding the third function , the positioning mechanism 14 electrically stimulates and / or senses electrical signals from the anatomical structure by electrically coupling to the anatomical structure and sending and / or receiving electrical signals to the tissue . the positioning mechanism 14 preferably includes an even number of electrodes or electrically active portions such that a bipolar electrical system may be used , wherein each pair of electrodes or electrically active portions has an opposite polarity . the positioning mechanism 14 may alternatively include a single electrode or electrically active portion and use a monopolar electrical system , or may include any other suitable number of electrodes or electrically active portions . the positioning mechanism 14 functions to map the tissue by sensing the electrical conduction between the pulmonary veins and the other parts of the atrial wall on the endocardial side . the positioning mechanism 14 functions to pace the tissue and maintain an artificial heart rate ( preferably temporarily ) by sending electrical pulses to the tissue . the positioning mechanism 14 preferably paces the tissue located in a position distal from the energy delivery structure 18 and / or the ablation path 30 , such that the energy delivery structure 18 and / or the ablation path 30 are between the positioning mechanism 14 that is pacing and the beating heart . the positioning mechanism may alternatively pace tissue in any other suitable location . the recording and sensing signals received and sent by the positioning mechanism are preferably compatible with conventional navigation and mapping systems such as carto xp ep navigation system ( biosense webster , diamond bar , calif . ), ensite system ( st . jude medical , st . paul , minn . ), and / or any other suitable mapping , navigation , or visualization system . as mentioned above , the positioning mechanism 14 of the preferred embodiments performs one or more of the following functions : ( a ) facilitate locating an anatomical structure , ( b ) anchor the elongate member 12 with respect to the anatomical structure , and ( c ) electrically stimulate and / or sense electrical signals from the anatomical structure . although the positioning mechanism 14 is preferably one of the several variations described below , the positioning mechanism 14 may be any suitable mechanism to perform one or more of these functions . first variation of the positioning mechanism . in a first variation , as shown in fig5 , 6 a , and 6 b , the positioning mechanism 14 ′ includes a plurality of wires each having a first end 24 and a second end 26 . the plurality of wires are preferably flexible wires , but may alternatively be movable in any other suitable fashion . the first end 24 is preferably coupled to the distal tip of the elongate member 12 , but may alternatively be attached in any other suitable location ( shown in fig4 ). the second end 26 preferably extends from the distal tip of the elongate member and is positioned in a fully extended position , as shown in fig5 . the second end 26 preferably deflects due to contact with a surface , as shown in fig6 a and 6b . the second end 26 is preferably biased towards the fully extended position , but may alternatively be biased towards any other suitable position . the first end 24 is preferably slidably coupled to the elongate member 12 such that it is partially or fully retractable into the elongate member 12 . for example , the plurality of wires may be pushed or pulled through the distal tip of the elongate member 12 by a wire that extends through the elongate member 12 . the plurality of wires may be pulled back through the distal tip of the elongate member 12 in order to return the wires to the fully extended position , as shown in fig5 . the plurality of wires may alternatively be fixed to the distal tip of the elongate member 12 or coupled to the elongate member 12 in any other suitable fashion . the wires are preferably made from a conductive material and / or a material with shape memory such as nickel / titanium or a shape memory polymer . the material is preferably flexible so as not to cause injury to the tissue of the heart where the positioning mechanism 14 ′ might contact and move against it . at least a portion of each wire is preferably made from a fluoro - opaque material , such as platinum or gold , such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion 28 is preferably located at the second end 26 of a wire , but may alternatively be located in any suitable position such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably flush with the wire , but may alternatively have a round or any other suitable shape such that it will not damage the tissue . additionally , the plurality of wires preferably includes at least one electrically active portion and / or at least one insulated portion ( e . g . an insulating coating on a portion of each wire ). the electrically active portion is preferably located at the second end 26 of a wire , but may alternatively be located in any suitable position , such as the center portion , such that it conies in contact with tissue . the plurality of wires preferably has any suitable geometry such that positioning mechanism 14 ′ may perform any combination of functions described . additionally , the plurality of wires preferably have a length and / or geometry such that when they deflect , they do not cover , block , or lay in front of the energy delivery structure 18 , or any portion thereof . therefore , they preferably do not block any portion of the energy delivered by the energy delivery structure 18 and cause a “ shadow ” effect . in a first version , as shown in fig5 , the wires are substantially straight . in a second version , as shown in fig8 a , the wires are curved or bent such that they are biased away from the elongate member 12 . in a third version , as shown in fig8 b , the plurality of wires includes six wires circumferentially disposed around the elongate member 12 . the plurality of wires preferably includes an even number of wires , but may alternatively include a single wire or any other suitable number of wires . in a fourth version , as shown in fig8 c , the plurality of wires includes multiple tiers or layers of wires . each tier or layer may include any suitable number of wires and each tier or level may include a different number of wires from any other tier or level . as shown in fig6 a and 6b , the plurality of wires function to facilitate locating an anatomical structure by flexing as they come in contact with the anatomical structure . for example , the wires will remain fully extended from the elongate member 12 when they are unobstructed in the left atrium of the heart 3002 , as shown in fig4 . as the system 10 is moved within the left atrium of the heart 3002 and begins to contact the ostium ( opening ) of a pulmonary vein 3000 , the plurality of wires will begin to deflect partially , as shown in fig6 a . as the system 10 is moved into the pulmonary vein 3000 , the wires will deflect more dramatically as shown in fig6 b . as the system is moved deeper into the pulmonary vein , the wires will not deflect as much , if at all , and an operator of the system 10 will be able to determine when the positioning mechanism 14 of the system 10 is correctly located within the pulmonary vein . furthermore , as shown in fig7 , the angle 3004 at which the system 10 enters the pulmonary vein 3000 with respect to the longitudinal axis of the pulmonary vein 3000 is determined . for example , if the system 10 is entering the pulmonary vein 3000 at angle 3004 , a wire to the left of the elongate member 12 will deflect to an angle 3006 with respect to the elongate member 12 while a wire to the right of the elongate member 12 will deflect to an angle 3008 with respect to the elongate member 12 . therefore , the angle 3004 at which the system 10 is entering the pulmonary vein 3000 is preferably determined from the size of angles 3006 and 3008 . these angles 3006 and 3008 are preferably detected visually under fluoroscopic guidance by the operator of the system 10 , but may alternatively be detected and processed by a processor in order to determine angle 3004 . upon the detection of the angle 3004 , an operator of the system 10 is alerted of an off - center entry , the operator adjusts and centers the system 10 and / or is instructed on how to do so . the system 10 may alternatively be adjusted automatically through a motor drive system or any other suitable system . the ablation path 30 is preferably altered such that energy delivery structure will be located substantially the same distance from each point of tissue along the ablation path 3 and / or the energy delivery structure is preferably adjusted to accommodate an off - center entry . the energy delivery structure is preferably adjusted by changing the power and / or frequency , bandwidth , and amplitude of the sound wave propagated into the tissue along certain portions of an ablation path 30 . due to an off - center entry , the energy delivery structure will be closer to some tissue along the ablation path 30 and further away from other tissue . in one example , the energy delivery structure is adjusted to use less power for the portions of the tissue that are closer to the energy delivery structure . the plurality of wires function to anchor the elongate member 12 with respect to the anatomical structure , preferably a pulmonary vein 3000 , by coupling to the anatomical structure . the outward biasing force of the plurality of wires against the interior wall of the pulmonary vein will preferably hold the positioning mechanism 14 ′ within the pulmonary vein due to friction . alternatively , the tips of the plurality of wires may function as barbs such that the plurality of wires are preferably advanced into the pulmonary vein , but the tips of the wires will prevent the positioning mechanism 14 from being pulled out of the pulmonary vein . in this version , the wires may be manually retracted upon completion of the procedure to allow for the removal of the positioning mechanism 14 ′. the positioning mechanism may alternatively function to anchor the elongate member 12 with respect to the anatomical structure in any other suitable fashion . second variation of the positioning mechanism . in a second variation , as shown in fig9 a and 9b , the positioning mechanism 14 ″ includes a plurality of wires , a first end cap 32 , a second end cap 34 , and a pull member 36 . the plurality of wires are circumferentially disposed around the elongate member 12 . the plurality of wires preferably includes an even number of wires such as two , four , six , eight , or more , but may alternatively include a single wire or any other suitable number of wires . the first end cap 32 is preferably coupled to the distal tip of the elongate member 12 , but may alternatively be attached in any other suitable location , as shown in fig4 . the second end cap 34 preferably extends from the distal tip of the elongate member 12 along the longitudinal axis of the elongate member 12 and transitions between a fully extended position , as shown in fig9 a , and a retracted position , as shown in fig9 b . when the second end cap 34 is in the fully extended position , the wires are preferably substantially straight . when the second end cap 34 is in the retracted position , the wires preferably flex and bend at one location along the wire to form a basket or cage - like structure . the second end cap 34 preferably transitions between a fully extended position and a retracted position by pulling the pull member 36 . the pull member 36 is preferably coupled to the second end cap 34 and runs through the first end cap 32 such that the first end cap 32 is slidably coupled to the pull member 36 . preferably , the pull member 36 is attached to the second end cap 34 with an adhesive band , but may alternatively be coupled to the second end cap 34 with any other suitable chemical and / or mechanical connection such as adhesive , welding , pins and / or screws . the pull member is preferably disposed within a lumen of the first end cap and the elongate member 12 , but may alternatively be held in any suitable location . the pull member preferably terminates at a slider in a proximal housing ( not shown ) that preferably includes various actuating mechanisms to transition the second end cap from the fully extended position to the retracted position . the second end cap preferably returns to the fully extended position by the spring force of the plurality of wires ( they are preferably biased towards the substantially straight position ), but may alternatively return to the fully extended position in any other suitable fashion . the wires may alternatively flex or bend in multiple locations and each wire may bend in a different location . the wires are preferably biased towards the substantially straight position , but may alternatively be biased towards the bent position or any other suitable position . the wires are preferably made from a conductive material and / or a material with shape memory such as nickel / titanium alloys or a shape memory polymer , but may alternatively be made from any suitable material such as plastic . the material is preferably flexible so as not to cause injury to the tissue of the heart where the positioning mechanism 14 might contact and move against it . at least a portion of each wire is preferably made from a fluoro - opaque material ( also referred to herein using the term “ radiopaque ”), such as platinum or gold , such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably located in any suitable position such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably flush with the wire , but may alternatively have a round or any other suitable shape such that it will not damage the tissue . additionally , the plurality of wires preferably includes at least one electrically active portion and / or at least one insulated portion ( e . g . an insulating coating on a portion of each wire ). the electrically active portion is preferably located towards the center portion of each wire , but may alternatively be located in any suitable position such that it comes in contact with tissue . the positioning mechanism 14 ″ functions to facilitate locating an anatomical structure by the plurality of wires flexing as they come in contact with the anatomical structure . for example , when the wires are flexed or bent as shown in fig9 b , and as the system 10 is moved within the left atrium of the heart 3002 and begins to contact the ostium ( opening ) of a pulmonary vein 3000 , the plurality of wires will begin to deflect inward or away from the adjacent wires due to contact with a tissue surface . as the system is moved deeper into the pulmonary vein , the wires will not deflect as much if at all , and an operator of the system 10 will be able to determine when the positioning mechanism 14 ″ of the system 10 is correctly located within the pulmonary vein . the plurality of wires of the positioning mechanism 14 ″ function to anchor the elongate member 12 with respect to the anatomical structure , preferably a pulmonary vein 3000 , by coupling to the anatomical structure . preferably , the outward force of the plurality of wires in the flexed or bent position , as shown in fig9 b , against the interior wall of the pulmonary vein will hold the positioning mechanism 14 ″ within the pulmonary vein due to friction . in this version , the second end cap 34 will be returned to the fully extended position upon completion of the procedure , straightening the plurality of wires , to allow for the removal of the positioning mechanism 14 ″. the positioning mechanism 14 ″ may alternatively function to anchor the elongate member 12 with respect to the anatomical structure in any other suitable fashion . third , fourth , and fifth variation positioning mechanism . in a third variation , as shown in fig1 a and 10b , the positioning mechanism is a combination of the first and second variations of the positioning mechanisms 14 ′ and 14 ″. in this variation , the positioning mechanism preferably includes two pluralities of wires . the first plurality of wires has a first end 24 and a second end 26 as described above , and the second plurality of wires has a first end cap 32 , a second end cap 34 , and a pull member 36 also as described above . when the second end cap 34 is in the retracted position , as shown in fig1 b , the second plurality of wires preferably flex and bend in one location to form a basket or cage - like structure . the first plurality of wires deflect due to contact with a surface and will preferably deflect down and in between the second plurality of wires such that they will not obstruct the function of the second plurality of wires . in a fourth variation , as shown in fig1 , the positioning mechanism 14 ″′ is a coil . the coil is preferably made from a conductive material and / or a material with shape memory such as nickel / titanium alloys or a shape memory polymer . the material is preferably flexible so as not to cause injury to the tissue of the heart where the positioning mechanism 14 might contact and move against it . at least a portion of the coil is preferably made from a fluoro - opaque material , such as platinum or gold , such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably located in any suitable position such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably flush with the wire , but may alternatively have a round or any other suitable shape such that it will not damage the tissue . additionally , the coil preferably includes at least one electrically active portion and / or at least one insulated portion ( e . g . an insulating coating on a portion of each wire ). the electrically active portion is preferably located in any suitable position such that it comes in contact with tissue . the positioning mechanism 14 ″′ functions to facilitate locating an anatomical structure by the coil flexing as it comes in contact with the anatomical structure . for example , as the system 10 is moved within the left atrium of the heart 3002 and begins to contact the wall of the atrium or the ostium ( opening ) of a pulmonary vein 3000 , the coil will begin to deflect . as the system is moved deeper into the pulmonary vein , the wires will not deflect as much if at all , and an operator of the system 10 will be able to determine when the positioning mechanism 14 ″′ of the system 10 is correctly located within the pulmonary vein . the coil of the positioning mechanism 14 ″′ functions to anchor the elongate member 12 with respect to the anatomical structure , preferably a pulmonary vein 3000 , by coupling to the anatomical structure . preferably , the outward force of the coil against the interior wall of the pulmonary vein will hold the positioning mechanism 14 ″′ within the pulmonary vein due to friction . the positioning mechanism 14 ″′ may alternatively function to anchor the elongate member 12 with respect to the anatomical structure in any other suitable fashion . in a fifth variation , as shown in fig1 , the positioning mechanism includes at least one distal wire 38 and at least one proximal wire 40 , each wrapped around at least a portion of the elongate member 12 . the wires are preferably made from a conductive material and / or a material with shape memory such as nickel / titanium alloys or a shape memory polymer . the material is preferably flexible so as not to cause injury to the tissue of the heart where the wires might contact and move against it . at least a portion of each of the wires is preferably made from a fluoro - opaque material , such as platinum or gold , such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably located in any suitable position such that it may be seen while positioned inside the internal structures of a patient through the use of a fluoroscope . the fluoro - opaque portion is preferably flush with the wire , but may alternatively have a round or any other suitable shape such that it will not damage the tissue . additionally , each of the wires preferably includes at least one electrically active portion 42 and / or at least one insulated portion ( e . g . an insulating coating on a portion of each wire ). the wires each preferably include an even number of electrically active portions 42 such that a bipolar electrical system may be used , wherein each pair of electrodes or electrically active portions has an opposite polarity . for clarity , only a single electrically active portion 42 per wire has been shown in fig1 . the wires may alternatively include a single electrode or electrically active portion and use a monopolar electrical system , or may include any other suitable number of electrodes or electrically active portions . the electrically active portion 42 is preferably located in any suitable position such that it comes in contact with tissue . the distal wire 38 is preferably located distally from the energy delivery structure 18 , and the proximal wire is preferably located proximally from the energy delivery structure . the wires are preferably each coupled to the elongate member 12 at one end of the wire and then the other end is preferably wrapped around at least a portion of the elongate member 12 such that the other ends unwind towards the tissue once the distal tip assembly 16 is placed within the pulmonary vein 3000 or any other suitable structure . the wires preferably unwind such that the electrically active portion 42 of each wire is in contact with the tissue . the wires are preferably wrapped around the elongate member such that as the elongate member 12 and / or distal tip assembly are rotated ( as shown by arrow r in fig1 ), the electrically active portions 42 of the wires sweep along the tissue . the wires are further preferably wrapped around at least a portion of the elongate member such that they are biased away from one another . for example , the distal wire 38 may be wrapped such that the end is biased towards the distal end of the catheter . this will encourage the wires to not block the energy delivery structure and to not contact one another . there is preferably at least one distal wire and at least one proximal wire such that , as the energy delivery structure 18 delivers energy to the tissue to form an ablation path and / or conduction block , there will be at least one wire distal to the conduction block and at least one wire proximal to the ablation path and / or conduction block . although omitted for conciseness , the preferred embodiments include every combination and permutation of the various elongate members 12 and positioning mechanism 14 . while the above is a complete description of the preferred embodiments of the invention , various alternatives , modifications , and equivalents may be used . therefore , the above description should not be taken as limiting in scope of the invention which is defined by the appended claims .
methods and apparatus for an ablation device used in the treatment of atrial fibrillation comprise an elongate shaft and a positioning mechanism adjacent the distal end of the shaft . the positioning mechanism is adapted to facilitate location of an anatomic structure and also to anchor the elongate shaft adjacent the anatomic structure . the positioning mechanism comprises an electrode for stimulating the anatomic structure as well as sensing electrical signals . also , an energy delivery element is adjacent the distal end of the shaft and is adapted to stimulate the anatomic structure and create a zone of ablation that blocks abnormal electrical activity thereby reducing or eliminating atrial fibrillation in the patient .