the present invention will be described with reference to an ep catheter utilized in cardiac ep studies , such as the afocus ii eb diagnostic catheter of st . jude medical , atrial fibrillation division , inc ., which can provide access to difficult - to - reach portions of atrial anatomy , in particular the right superior and inferior pulmonary veins . the catheter described , depicted and claimed herein also provides relatively faster cardiac activity data collection ( especially in duodecapolar configurations ) by rapidly providing the necessary detail to efficiently diagnose complex cardiac arrhythmias . it should be understood , however , that the present teachings can be applied to good advantage in other contexts as well , such as radiofrequency ( rf ) ablation catheters or other diagnostic cardiac catheters . referring now to the drawings , fig1 a and 1b depict an ep catheter 10 according to a first aspect of the present invention . fig1 a is a plan view including a partially exploded depiction of an exemplary ep catheter 10 having a distal single shallow helical fixed - diameter loop cardiac mapping portion 16 with ep diagnostic , or mapping , electrodes 20 ( as depicted herein arranged in an exemplary decapolar configuration ), with the partially exploded depiction illustrating the catheter 10 in both a undeflected and a deflected configuration ( denoted as “ c ” and “ d ” respectively ). the off - axis , or peripheral , junction of the single shallow helical fixed - diameter loop to the neck region of the catheter allows 180 degree deflection in on the order of 50 mm ( as illustrated in said “ d ” configuration ). fig1 b is a plan view of the exemplary ep catheter 10 illustrated in fig1 a in an undeflected configuration ( i . e ., configuration “ c ” of fig1 a ). fig1 b shows an approximate minimum length for the catheter body of on the order of about 110 cm , although other lengths can be employed according to this disclosure . fig1 c is an enlarged view of the distal single shallow helical fixed - diameter loop cardiac mapping portion 16 of the exemplary ep catheter 10 of fig1 a ; namely , an illustration of a pair of electrodes 20 residing on a segment 16 ′ of the offset shaft - to - loop axis , single shallow helical fixed - diameter loop cardiac mapping portion 16 . the lateral edges 20 ′ of electrodes 20 are bonded to the adjacent relatively smaller ( e . g ., 4f ) diameter biocompatible tubing ( e . g ., ptfe or the like ) of portion 16 with a biocompatible material such as a polyurethane matrix composed of polycin 936 and vorite 689 ( mixed 52 : 48 percent , as an example ) produced by caschem inc . of bayonne , n . j . fig1 d is an elevational side view in partial cross section of a neck portion 18 formed just proximal of the distal single shallow helical fixed - diameter loop cardiac mapping portion 16 of the exemplary ep catheter 10 depicted in fig1 a and 1b . as shown , an extended braid tube / spring assembly 50 surrounds a variety of subcomponents of catheter 10 and is itself wrapped by a relatively smaller diameter biocompatible tubing 18 that covers the neck region and transitions the outer diameter to the about 4 f distal single shallow helical fixed - diameter loop cardiac mapping portion 16 . where the extended braid tube / spring assembly 50 terminates at its distal edge a small amount of medical grade adhesive polymer 20 ″ ( e . g ., like the polymer 20 ′ used at the edges of electrodes 20 ) can be applied . a polyimide tube 56 ′ passes through the assembly 50 ( and neck region 18 ) and into the distal single shallow helical fixed - diameter loop cardiac mapping portion 16 and isolates a plurality of elongate conductive strands 70 ′ ( shown in fig4 b ) that couple the electrodes 20 , 46 to remote circuitry via a handle ( 22 as shown in fig1 a and 1b ) having a mass termination where the conductors 70 pass through the handle to couple to an ep recording system or other diagnostic equipment , for example . a flat wire subassembly 52 , which includes segment of flat wire 59 , is coupled to an activation wire 54 and is adapted to impart and release tension to deflect the proximal end 16 in a plane defined by the flat wire subassembly 52 ( via manipulation of the handle , such as by rotation or linear actuation members , and the like ). the flat wire subassembly 52 is sometimes described as a planarity member or element because it promotes such planar deflection . a short segment of polyimide tubing 56 ′ surrounds a junction of several components ; namely , a lubricous tubing member 58 ( e . g ., peek tubing ) that receives a proximal end of an elongate shape memory member 30 ( formed of nitinol , for example ) that is preformed into a desired dimension and configuration for distal portion 16 . in one embodiment , the distal portion 16 has an overall outer diameter of about 15 mm ( i . e ., for the outermost loop ) with a 4 f dimension for portion 16 ′ and 1 mm ( wide ) platinum electrodes 20 and a 2 mm ( long ) tip electrode 46 . in this embodiment , the electrodes 20 can be spaced apart in bipolar pairs or evenly ( e . g ., about 3 mm , 5 mm or other nominal spacing between them ). in a bipolar pair configuration the electrode spacing can vary , of course , although in on embodiment the spacing for 1 mm ( wide ) ring - type electrodes is 1 mm per bipolar pair with 2 . 5 mm between pairs . in this embodiment the spacing between the tip electrode 46 to the most distal ring - type electrode 20 can be 1 mm or 2 mm or other value . in the embodiments depicted herein the diameter of the outer loop of the distal portion 16 is fixed ( e . g ., at about 15 , mm , 20 mm or less than about 33 mm , or more , if desired ). at the junction of the flat wire subassembly 52 with the nitinol wire 30 wrapped in , for example , peek tubing urethane adhesive ( denoted by reference numeral 26 in fig2 b ) can be applied between , above , and around the components within the polyimide tubing 56 ′ to encapsulate same . similarly , urethane adhesive 26 can be impregnated into the interstices of the neck region 18 and distal portion 16 to reduce or eliminate any migration of the nitinol wire 30 or peek tubing 58 or polyimide tube 60 ( surrounding conductor 70 ′) during use . in general , ep catheter 10 can include an elongate catheter body 12 , which , in some embodiments , is tubular ( e . g ., it defines at least one lumen therethrough ). catheter body 12 includes a proximal region 14 , a distal portion 16 , and a neck region 18 between proximal region 14 and distal portion 16 . one of ordinary skill in the art will appreciate that the relative lengths of proximal region 14 , distal portion 16 , and neck region 18 depicted in fig1 a and 1b are merely illustrative and can vary without departing from the spirit and scope of the present invention but likely should not have a magnitude of less than about 110 cm . of course , the overall length of catheter body 12 should be long enough to reach the intended destination within the patient &# 39 ; s body . catheter body 12 will typically be made of a biocompatible polymeric material , such as polytetrafluoroethylene ( ptfe ) tubing ( e . g ., teflon ® brand tubing ). of course , other polymeric materials , such as fluorinated ethylene - propylene copolymer ( fep ), perfluoroalkoxyethylene ( pfa ), poly ( vinylidene fluoride ), poly ( ethylene - co - tetrafluoroethylene ), and other fluoropolymers , can be utilized . additional suitable materials for catheter body 12 include , without limitation , polyimide - based thermoplastic elastomers ( namely poly ( ether - block - amide ), such as pebax ®), polyester - based thermoplastic elastomers ( e . g ., hytrel ®), thermoplastic polyurethanes ( e . g ., pellethane ®, estane ®), ionic thermoplastic elastomers , functionalized thermoplastic olefins , and any combinations thereof . in general , suitable materials for catheter body 12 can also be selected from various thermoplastics , including , without limitation , polyamides , polyurethanes , polyesters , functionalized polyolefins , polycarbonate , polysulfones , polyimides , polyketones , liquid crystal polymers and any combination thereof . it is also contemplated that the durometer of catheter body 12 can vary along its length . in general , the basic construction of catheter body 12 will be familiar to those of ordinary skill in the art , and thus will not be discussed in further detail herein . referring now to fig2 a which is a close up isometric view of the distal single shallow helical fixed - diameter loop cardiac mapping portion 16 of the exemplary ep catheter 10 of fig1 a and 1b ( with a perspective view of connecting elements within interior portions of the catheter body , or shaft , illustrated ) according to some embodiments of the present invention . as illustrated , the proximal and distal ends of the flat wire subassembly 52 ( e . g ., implemented to promote planarity during deflection ) are emphasized . fig2 b is an isometric illustration of the neck region 18 and the single shallow helical fixed - diameter loop distal portion 16 , polyimide tubing 56 , and the flat wire subassembly 52 . fig2 b ′ is an enlarged isometric fragmented view of the interior details of the ends of the various connecting elements within the interior of the catheter body 14 , 18 of fig2 a . as depicted , the proximal end of a flattened peek tube 58 that contains the nitinol wire 30 is adhered with urethane adhesive 26 ( or other suitable medical grade adhesive ) to segment of flat wire 59 of the flat wire subassembly 52 and wrapped in polyimide tubing 56 ′ for containment . the proximal end of the flat wire subassembly 52 couples via a segment of polyimide tubing 56 filled with urethane adhesive 26 that also encapsulates the smaller diameter polyimide tubing 61 where the activation wire 54 resides . a gap of about 1 - 2 mm between the tubing 56 and the distal end of extended braid / spring subassembly 50 should be optionally maintained ( as depicted ) and the activation wire 54 and conductor wires 70 ( within polyimide tube 60 ) are conveyed through braid / spring subassembly 50 to a handle or other remote location . fig2 c is an enlarged fragmented plan view of the interior details of the ends of the connecting elements within the interior of the catheter body shown in fig2 a . as depicted , the flattened section of the peek tubing 58 disposed within the polyimide tubing 56 ′ can comprise a 1 mm segment to promote adhesion to the urethane adhesive 26 impregnated therein and thus to the flat wire subassembly 52 , including segment of flat wire 59 . similarly , the proximal end of the flat wire subassembly 52 can be surrounded by polyimide tubing 56 and impregnated with urethane adhesive ( not shown ) to promote mechanical coupling to the adjacent extended braid / spring subassembly 50 . a suitable biocompatible compound 20 ″ ( e . g ., such as polymer 20 ′) can be applied to the junction between the outer covering for distal portion 16 ′ and the neck region 18 . fig3 is an elevational view showing exemplary dimensions of the distal single shallow helical fixed - diameter loop cardiac mapping portion 16 of the exemplary ep catheter 10 of fig1 a and 1b according to an embodiment of the present disclosure . for example , the “ plane ” of the single shallow helical fixed - diameter loop distal portion 16 can be on the order of 2 mm to the neck region 18 , although other dimensions can be used if desired . whatever dimension is used the wire support length therefrom should be a reasonable length . fig4 a depicts the distal single shallow helical fixed - diameter loop cardiac mapping portion 16 of the exemplary ep catheter 10 of fig1 a and 1b ( with cross references to details shown in fig4 b and 4c ). in the illustrated embodiment the single shallow helical fixed - diameter loop distal portion 16 includes evenly - spaced ten - pole electrodes 20 with a nominal separation between adjacent electrodes 20 . of course , other dimensions can be used for the electrodes 20 and the spacing therebetween . at the proximal end of the catheter body 12 ( not specifically shown ) a plurality of individually electrically insulated elongate conductors 70 emerge and are adapted to be individually coupled to mass termination terminal 72 within a handle for ultimate electrical communication with an ep recording system , an electroanatomical localization and visualization system ( e . g ., such as the ensite system of st . jude medical , inc . operating the onemap facility or other similar systems for monitoring cardiac activity and providing one or more visual representations of same ). fig4 b is an enlarged fragmentary view in partial cross section and partial cut - away of the distal tip electrode 46 and two ring - type electrodes 20 and flat wire subassembly 52 connection within the catheter body 12 , respectively , shown in fig4 a . each electrode 20 , 46 couples via an elongate conductor 70 ′ in fig4 b to remote ep recording and / or localization and visualization equipment . a biocompatible adhesive 21 ( e . g ., loctite adhesive ) can be applied to the junction of the biocompatible tubing 16 of the distal portion 16 and the electrode 46 to eliminate body fluid ingress therein . a so - called safety wire ( or element ) 71 can couple to the electrode 46 and a proximal location to reduce or eliminate the chance that the electrode 46 might separate from the catheter assembly 10 . fig4 c is an enlarged fragmentary view in partial cross section of the catheter body near the neck region shown in fig4 a and indicates a cross sectional view along lines a - a therein which is reflected in fig5 hereinbelow described . the dimensions indicated on fig4 c are merely exemplary and illustrative and not intended as limiting in any way . fig5 is a cross - sectional view of the ep catheter 10 illustrated in fig4 c taken along line a - a as shown in fig4 c . the biocompatible tubing overlaying next region 18 includes ( electrode 20 ) conductor wires , denoted by reference numeral 70 in fig5 , surrounded by polyimide tubing 60 and nominally spaced from nitinol wire 30 by a space impregnated with urethane adhesive 26 . one of ordinary skill in the art will appreciate that electrodes 20 can be ring - type electrodes or any other electrodes suitable for a particular application of ep catheter 10 . for example , where ep catheter 10 is intended for use in a contactless ep study , electrodes 20 can be configured as described in u . s . application ser . no . 12 / 496 , 855 , filed 2 jul . 2009 , which is hereby incorporated by reference as though fully set forth herein . of course , in addition to serving sensing purposes ( e . g ., cardiac mapping and / or diagnosis ), electrodes 20 can be employed for therapeutic purposes ( e . g ., cardiac ablation and / or pacing ). referring again to the present disclosure in general , various handles and their associated actuators for use in connection with deflecting ep catheters are known , and thus handle 22 will not be described in further detail herein except that is has a means for imparting tension ( e . g ., push - pull knob 24 depicted in fig1 a and 1b , although other biasing structures can of course be used ) to an activation wire . in use , ep catheter 10 is introduced into a patient &# 39 ; s body proximate an area of interest , such as a pulmonary vein ostium . of course , ep catheter can be introduced surgically ( e . g ., via an incision in the patient &# 39 ; s chest ) or non - surgically ( e . g ., navigated through the patient &# 39 ; s vasculature to a desired site ). activation wire 54 can be actuated in order to deflect proximal region 14 of catheter body 12 such that distal portion 16 is oriented generally towards the ostium of interest . electrodes 20 can then be employed for diagnostic or therapeutic purposes . all directional references ( e . g ., upper , lower , upward , downward , left , right , leftward , rightward , top , bottom , above , below , vertical , horizontal , clockwise , and counterclockwise ) are only used for identification purposes to aid the reader &# 39 ; s understanding of the present invention , and do not create limitations , particularly as to the position , orientation , or use of the invention . joinder references ( e . g ., attached , coupled , connected , and the like ) are to be construed broadly and can include intermediate members between a connection of elements and relative movement between elements . as such , joinder references do not necessarily infer that two elements are directly connected and in fixed relation to each other . it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative only and not limiting . changes in detail or structure can be made without departing from the invention as defined in the appended claims .
an ep catheter includes a tubular body having a proximal region , a neck region , and a distal portion predisposed into a single shallow helical fixed - diameter loop configuration and including a plurality of diagnostic electrodes . in deflectable catheter forms , at least one activation wire extends through at least a portion of the proximal region of the catheter body and is adapted to deflect the up to approximately 180 degrees relative to the proximal region . the catheter can be operated manually by a clinician or via a clinician - surrogate such as a computer processor - controlled surgical system . in addition , a variety of localization , visualization , and / or orientation - specific elements can be incorporated into the devices described , depicted , and claimed herein .