Patent Publication Number: US-2023149069-A1

Title: Planar catheter with overlapping electrode pairs

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of priority to prior filed U.S. Provisional Pat. Application No. 63/279,747 filed on Nov. 16, 2021, which is hereby incorporated by reference as if set forth in full herein. 
    
    
     BACKGROUND 
     Cardiac arrhythmia, such as atrial fibrillation, occurs when regions of cardiac tissue abnormally conduct electric signals to adjacent tissue, thereby disrupting the normal cardiac cycle and causing asynchronous rhythm. Sources of undesired signals can be located in tissue of an atria or a ventricle. Unwanted signals are conducted elsewhere through heart tissue where they can initiate or continue arrhythmia. 
     Procedures for treating arrhythmia include surgically disrupting the origin of the signals causing the arrhythmia, as well as disrupting the conducting pathway for such signals. More recently, it has been found that by mapping the electrical properties of the endocardium and the heart volume, and selectively ablating cardiac tissue by application of energy, it is possible to cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. 
     In this two-step procedure, which includes mapping followed by ablation, electrical activity at points in the heart is typically sensed and measured by advancing a catheter containing one or more electrical sensors into the heart and acquiring data at multiple points. These data are then utilized to select the target areas at which ablation is to be performed. 
     For greater mapping resolution, it is desirable for a mapping catheter to provide high-density signal maps through the use of several electrodes sensing electrical activity of tissue in an area on the order of a square centimeter. For mapping within an atria or a ventricle (for example, an apex of a ventricle), it is desirable for a catheter to collect larger amounts of data signals within shorter time spans. It is also desirable for such a catheter to be adaptable to different tissue surfaces, for example, flat, curved, irregular or nonplanar surface tissue and be collapsible for atraumatic advancement and withdrawal through a patient’s vasculature. It is also desirable to produce a catheter having increased electrode density and improved maneuverability within the heart of a patient. Accordingly, it may be advantageous to provide a shortened length end effector that is more maneuverable within a heart of a patient and has a higher density of electrodes. It may also be advantageous to provide a shortened length end effector that may include equidistantly spaced bipoles by bypassing every other electrode along a linear direction. 
     SUMMARY 
     Various embodiments described herein allow high density mapping and/or ablation of tissue surface in the heart, including an atria or a ventricle, by virtue of a catheter for electrophysiology applications. The catheter may include a tubular member and an end effector. The tubular member may include a proximal portion and a distal portion defining a longitudinal axis. The tubular member may be configured to be manipulated at the proximal portion to position the distal portion into a heart of a patient. The distal portion may include a cross-section disposed about the longitudinal axis which intersects a first and second orthogonal plane that extend along the longitudinal axis. The cross section of the distal portion may include a first opening intersecting the first orthogonal plane and the second orthogonal plane and extending along the longitudinal axis, and six apertures disposed circumferentially about the first opening. Each of the six apertures may be configured to receive a spine. The end effector may be coupled to the distal portion. The end effector may include a first, second, and third loop members. Each of the loop members may include two spines and a connector that connects the two spines. The first, second, and third loop members may be configured such that each connector of the first, second, and third loop members may overlap at a distal vertex. The end effector may be configured to be delivered through vasculature in a collapsed configuration and expand in the heart to a deployed configuration such that in the deployed configuration the loop members are approximately planar. 
     In another embodiment, an end effector for use with a for electrophysiology applications is disclosed. The end effector may have a distal end and a proximal end. The distal end may be configured to be delivered through vasculature in a collapsed configuration and expand in the heart to a deployed configuration. The end effector may include a plurality of electrodes disposed on a plurality of equidistantly spaced spine members parallel to a longitudinal axis. The plurality of electrodes may be arranged in a grid. The plurality of equidistantly spaced spine members may form columns of the grid such that within each respective column, the plurality of electrodes may be spaced from an immediately adjacent electrode by a first gap length. The plurality of electrodes may form rows of the grid across the plurality of spine members, such that within each respective row, the plurality of electrodes may be spaced from an immediately adjacent electrode by a second gap length that measures approximately twice the first gap length. 
     In another embodiment, a method of use of a catheter for high density mapping and/or ablation of tissue surface in the heart is disclosed. The example method can include one or more of the following steps presented in no particular order. The method may include moving a distal portion of an elongated shaft of an end effector extending distally from the distal portion through a catheter into a heart. The elongated shaft may define a longitudinal axis and the end effector may include a plurality of electrodes disposed on a plurality of equidistantly spaced spine members parallel to the longitudinal axis. The plurality of electrodes may be arranged in a grid, and the plurality of electrodes may form rows of the grid. The method may include moving the end effector from a distal end of the catheter by manipulation of a proximal portion of the elongated shaft. The method may include contacting the plurality of electrodes carried by the end effector to heart tissue by manipulation of the proximal portion of the elongated shaft. The method may include activating one or more first electrode bipoles disposed on at least one spine member. The one or more first electrode bipoles may include two electrodes having at least a third electrode positioned between the two electrodes. The method may include receiving, while the plurality of electrodes are in contact with the heart tissue, electrical potentials from the one or more first electrode bipoles. 
     According to some embodiments, the method may further include deflecting the end effector at an angle relative to the longitudinal axis to contact the one or more first electrode bipoles and one or more second electrode bipoles to the heart tissue, activating one or more second electrode bipoles disposed orthogonally to the longitudinal axis along a respective row of the grid, and receiving, while the plurality of electrodes are in contact with the cardiovascular tissue, electrical potentials from the cardiovascular tissue via the one or more second electrode bipoles. 
     In any of the embodiments described earlier, the following features can be combined in various permutations with the embodiments as well as with each other. The two spines of each loop members may extend along the longitudinal axis, and each of the spines may include a plurality of electrodes that have at least a first electrode, a second electrode, and a third electrode disposed thereon. Each electrode may be spaced from an immediately adjacent electrode on a respective spine member by a first gap length. The first electrode of a respective spine member and the third electrode of a respective spine member may form a first bipole. Each respective electrode of a first spine may be spaced from a corresponding electrode of a second spine by a second gap length that measures approximately twice the first gap length. Each electrode of the first spine may form second bipoles with the corresponding electrode of the second spine. The two spines of the first loop member may be attached to non-adjacent apertures of the cross-section of the distal portion. The two spines of the second loop member may be attached to immediately adjacent apertures, and the two spines of the third loop members may be attached to non-adjacent apertures of the cross-section such that the first loop member and the third loop member do not intersect the second loop member. The first loop member and the third loop member may be considered outer loops and the second loop member may be considered an inner loop such that the outer loops intersect one another along the longitudinal axis and do not intersect the inner loop along the longitudinal axis. Four apertures may be disposed on one side of the second orthogonal plane with three apertures disposed on a first side of the first orthogonal plane, and three apertures disposed on a second side of the first orthogonal plane. The second loop member may be positioned on one side of the second orthogonal plane. The first loop member may lie on a first plane, the second loop member may lie on a second plane, and the third loop member may lie on a third plane, the first, second, and third planes intersecting each other. Each spine may be configured such that in the deployed configuration each spine is approximately parallel to each other such that the plurality of electrodes are positioned to define an electrode grid. Each respective electrode of the first spine may be linearly spaced along the first spine member and form respective overlapping electrode pairs. The first gap length may be between immediately adjacent electrodes measured from a center of each of the immediately adjacent electrodes. Each spine may include a plurality of spine segments each having a length equal to the first gap length less a length of a respective electrode. Each spine member may include eight electrodes. Each of the electrodes may have an electrode length measuring from approximately 100 microns to approximately 750 microns. The first gap length may include a length selected from approximately 1 millimeter, approximately 1.2 millimeters, and approximately 2.4 millimeters. The plurality of electrodes may be configured to receive electrical potentials from the heart when the end effector is in the deployed configuration. The plurality of electrodes may be configured to ablate heart tissue when the end effector is in the deployed configuration. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A  is an illustration of a catheter having an end effector at a distal portion of the catheter and a proximal handle at a proximal portion of the catheter according to aspects of the present invention. 
         FIGS.  1 B and  1 C  are illustrations of orthogonal side plan views of a variation of the apparatus illustrated in  FIG.  1 A  according to aspects of the present invention. 
         FIGS.  2 A,  2 B,  2 C, and  2 D  are illustrations depicting orientation of loop members of the end effector according to aspects of the present invention. 
         FIG.  3    is an illustration of a side view of the end effector according to aspects of the present invention. 
         FIG.  4    is an illustration of a standard length end effector as is known in the art. 
         FIG.  5    is an illustration of a shortened length end effector, and a corresponding electrode grid, according to aspects of the present invention. 
         FIGS.  6 A and  6 B  are illustrations of views of the end effector pressed to a planar surface according to aspects of the present invention. 
         FIGS.  7 A,  7 B, and  7 C  are illustrations of an electrode spacing of an end effector, an end effector having a mechanical linkage connecting each loop member, and an interior lumen of a loop member, respectively, according to aspects of the present invention. 
         FIG.  8    is an illustration of a cardiovascular treatment utilizing the apparatus according to aspects of the present invention. 
         FIG.  9    is a flowchart of an exemplary method of treating a patient utilizing the apparatus according to aspects of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The following description of certain examples of the invention should not be used to limit the scope of the present invention. The drawings, which are not necessarily to scale, depict selected embodiments and are not intended to limit the scope of the invention. The detailed description illustrates by way of example, not by way of limitation, the principles of the invention. Other examples, features, aspects, embodiments, and advantages of the invention will become apparent to those skilled in the pertinent art from the following description, which is by way of illustration, one of the best modes contemplated for carrying out the invention. As will be realized, the invention is capable of other different or equivalent aspects, all without departing from the invention. Accordingly, the drawings and descriptions should be regarded as illustrative in nature and not restrictive. 
     Any one or more of the teachings, expressions, versions, examples, etc. described herein may be combined with any one or more of the other teachings, expressions, versions, examples, etc. that are described herein. The following-described teachings, expressions, versions, examples, etc. should therefore not be viewed in isolation relative to each other. Various suitable ways in which the teachings herein may be combined will be readily apparent to those skilled in the pertinent art in view of the teachings herein. Such modifications and variations are intended to be included within the scope of the claims. 
     As used herein, the terms “about” or “approximately” for any numerical values or ranges indicate a suitable dimensional tolerance that allows the part or collection of components to function for its intended purpose as described herein. More specifically, “about” or “approximately” may refer to the range of values ±10% of the recited value, e.g. “about 90%” may refer to the range of values from 81% to 99%. 
     As used herein, the terms “patient,” “host,” “user,” and “subject” refer to any human or animal subject and are not intended to limit the systems or methods to human use, although use of the subject invention in a human patient represents a preferred embodiment. 
     As used herein, the terms “tubular” and “tube” are to be construed broadly and are not limited to a structure that is a right cylinder or strictly circumferential in cross-section or of a uniform cross-section throughout its length. For example, the tubular structure or system is generally illustrated as a substantially right cylindrical structure. However, the tubular system may have a tapered or curved outer surface without departing from the scope of the present invention. 
       FIG.  1 A  illustrates an example apparatus  10  having an elongated shaft  9 , a distal electrode assembly or end effector  100 , and a deflection control handle  16 .  FIGS.  1 B and  1 C  and illustrations of orthogonal side plan views of a variation of the apparatus  10  illustrated in  FIG.  1 A . The apparatus  10  can have several design variations while including novel aspects illustrated herein. The apparatus  10  is presented for illustration purposes only and is not intended to be limiting. 
     The elongated shaft  9  has a proximal portion  12  in the shape of an elongated catheter body, an intermediate deflection section  14 , and distal portion  14 A. The deflection control handle  16  is attached to the proximal end of the catheter body  12 . The distal portion  14 A of the shaft is coupled to the end effector  100  via a connector tubing  46 . The elongated shaft  9  forms a tubular catheter body sized and otherwise configured to traverse vasculature. The end effector  100  has a plurality of loop members  1 ,  2 ,  3  that overlap at a common distal vertex  5  and are joined at the distal vertex  5  with a mechanical linkage  50 , as shown in  FIG.  2 A . Catheter body  12  can be of any suitable construction and made of any suitable material. In some embodiments, the catheter body may include an outer wall made of polyurethane or PEBAX. The outer wall may include an imbedded braided mesh of stainless steel or the like to increase torsional stiffness of the catheter body  12  such that, when the control handle  16  is rotated, the intermediate section  14  of the catheter  10  may rotate in a corresponding manner. The outer diameter of the catheter body is preferably no more than about 8 French, and more preferably about 7 French. The thickness of the outer wall may be thin enough such that a central lumen within catheter body  12  may house any desired wires, cables, and/or tubes. 
     When the device is unconstrained and aligned, the proximal portion  12 , intermediate section  14 , distal portion  14 A, and end effector  100  are generally aligned along a longitudinal axis L-L, as shown in  FIG.  1 A . The intermediate section  14  can be configured to bend to deflect the distal portion  14 A and end effector  100  from the longitudinal axis L-L. 
     The useful length of the elongated shaft  9 , i.e., that portion of the apparatus  10  that can be inserted into the body excluding the end effector, can vary as desired. Preferably the useful length ranges from about 110 cm to about 120 cm. The length of the intermediate section  14  is a relatively smaller portion of the useful length, and preferably ranges from about 3.5 cm to about 10 cm, more preferably from about 5 cm to about 6.5 cm. 
     Catheter body proximal portion  12  can be attached to the intermediate section  14  as shown and described in  FIGS.  2 A and  2 B  of U.S. Pat. No. 9,820,664, which is incorporated by reference herein with a copy in the Appendix of priority application U.S. 63/279,747. If desired, a spacer (not shown) can be located within the catheter body  12  between the distal end of the stiffening tube (if provided) and the proximal end of the intermediate section  14 . The spacer can provide a transition in flexibility at the junction of the catheter body  12  and intermediate section  14 , which can allow this junction to bend smoothly without folding or kinking. A catheter having such a spacer is described in U.S. Pat. No. 5,964,757, the disclosure of which is incorporated herein by reference with a copy provided in the Appendix of priority application U.S. 63/279,747. 
     As shown in  FIG.  1 A , the distal portion  14 A of the shaft  9  can be substantially contiguous with the intermediate section  14  such that the intermediate section includes the distal portion  14 A; the distal portion being distinguished from the intermediate section  14  by the positioning of one or more (optional) ring electrodes  38 R. As referred to herein, the distal portion  14 A of the shaft  9  can therefore correspond to a distal portion of the intermediate section  14 . 
     As shown in  FIG.  1 A , the distal portion  14 A of the shaft  9  is coupled to the end effector  100  with a connector tubing  46 . The connector tubing  46  includes an insert for connection of loop members  1 ,  2 ,  3  to provide electrical connection through the intermediate portion  14  of the catheter body. The connector tubing  46  can be affixed to the distal portion  14 A of the catheter by glue or the like. The connector tubing  46  can be shaped to house various components such as an electromagnetic position sensor, a puller wire anchor, ring electrodes  38 D,  38 P, etc. The connector tubing  46  may include an internal lumen configured to house various components, including lead wires configured to connect to ring electrodes  38 R,  38 D, and  38 P. Connector tubing  46  may additionally house lead wires configured to connect to electrodes  37  carried on the spines  1 A,  1 B,  2 A,  2 B,  3 A,  3 B. The internal lumen of connector tubing  46  may additionally house a cable for an electromagnetic position sensor. Electromagnetic location sensing technique is described in U.S. Pat. Nos. 5,391,199; 5,443,489; 5,558,091; 6,172,499; 6,590,963; and 6,788,967 which are incorporated by reference herein and attached to the Appendix of priority application U.S. 63/279,747. The magnetic position sensor can be utilized with impedance sensing electrode  38 R in a hybrid magnetic and impedance position sensing technique known as ACL described in U.S. Pat. Nos. 7,536,218; 7,756,567; 7,848,787; 7,869,865; and 8,456,182, which are incorporated by reference herein and attached to the Appendix of priority application U.S. 63/279,747. 
     The end effector  100  can be collapsed (compressed toward the longitudinal axis L-L) to fit within a guiding sheath or catheter (not illustrated). The shaft  9  can be pushed distally to move the end effector  100  distally through the guiding sheath. The end effector  100  can be moved to exit a distal end of the guiding sheath via manipulation of the shaft  9  and/or control handle  16 . An example of a suitable guiding sheath for this purpose is the Preface Braided Guiding Sheath, commercially available from Biosense Webster, Inc. (Irvine, California, USA). 
     The end effector  100  has first, second and third loop members  1 ,  2 , and  3 . Each loop member  1 ,  2 ,  3  has two spines  1 A,  1 B,  2 A,  2 B,  3 A,  3 B and a connector  1 C,  2 C,  3 C that connects the two spines of the respective loop member  1 ,  2 ,  3 . Spines  1 A,  1 B of a first loop member  1  are connected by a first connector  1 C; spines  2 A,  2 B of a second loop member  2  are connected by a second connector  2 C; and spines  3 A,  3 B of a third loop member  3  are connected by a third connector  3 C. 
     For each loop member  1 ,  2 ,  3  the spines  1 A,  1 B,  2 A,  2 B,  3 A,  3 B in the respective pair of spines can be substantially parallel to each other along a majority of their respective lengths when the end effector  100  is expanded in an unconstrained configuration as illustrated in  FIG.  1   . Preferably, all spines in the end effector are parallel to each other along the majority of their respective lengths when the end effector  100  is in the unconstrained configuration. Even when all spines are parallel, the spines are not necessarily all coplanar as described in greater detail elsewhere herein, for instance in relation to  FIGS.  2 A through  2 D . 
     Each spine  1 A,  1 B,  2 A,  2 B,  3 A or  3 B can have a length ranging between about 5 and 50 mm, preferably about 10 and 35 mm, and more preferably about 28 mm. The parallel portions of each spine  1 A,  1 B,  2 A,  2 B,  3 A,  3 B can be spaced apart from each other by a distance ranging between about 1 mm and 20 mm, preferably between 2 mm and 10 mm, and more preferably about 4 mm. Each spine  1 A,  1 A,  1 B,  2 A,  2 B,  3 A,  3 B preferably carries at least eight electrodes per spine member. The end effector preferably includes six spines as illustrated. With eight electrodes on six spines, the end effector  100  includes forty-eight electrodes. 
     A distal electrode  38 D and a proximal electrode  38 P are positioned near the distal portion  14 A of the shaft  9 . The electrodes  38 D and  38 P can be configured to cooperate (e.g. by masking of a portion of one electrode and masking a different portion on the other electrode) to define a referential electrode (an electrode that does not contact tissues). One or more impedance sensing electrodes  38 R can be configured to allow for location sensing via impedance location sensing technique, as described in U.S. Pat. Nos. 5,944,022; 5,983,126; and 6,445,864, which are incorporated by reference and attached to the Appendix of priority application U.S. 63/279,747. 
       FIGS.  2 A through  2 D  are illustrations depicting orientation of loop members of the shortened end effector.  FIGS.  2 B and  2 C  are cross sectional views of the end effector  100  and as indicated in  FIG.  2 A .  FIG.  2 D  is a view of the end effector  100  looking proximally from a distal end of the end effector  100  as indicated in  FIG.  2 A . As shown in  FIG.  2 A , each of the loop members  1 ,  2 ,  3 , respectively include proximal end segments  1 D,  2 D,  3 D,  1 E,  2 E,  3 E. affixed to the distal portion  14 A of the elongated shaft  9  of the apparatus  10 . The three loop members  1 ,  2 ,  3 , overlap at a common distal vertex  5  along the longitudinal axis L-L. As shown, each loop member  1 ,  2 ,  3  has two spines  1 A,  1 B,  2 A,  2 B,  3 A,  3 B and a connector  1 C,  2 C,  3 C that connects the two spines of the respective loop member  1 ,  2 ,  3 . Each spine segment  1 A,  1 B,  2 A,  2 B,  3 A, and  3 B have disposed thereon one or more electrodes  37 . As shown, each spine  1 A,  1 B,  2 A,  2 B,  3 A,  3 B carries at least eight electrodes per spine. The end effector preferably includes 6 spines as illustrated. Each electrode  37  on a respective spine may be separated from an adjacent spine by a distance of Lg1, as measured from a center of a first electrode  37  to a center of an immediately adjacent second electrode  37  (see  FIG.  5   ). According to some embodiments, the distance between each immediately adjacent electrode may be between approximately 1 mm and approximately 2.4 mm, and preferably approximately 1.2 mm. Each electrode  37  may have an electrode width L, which may be between approximately 100 microns to approximately 750 microns, and preferably approximately 500 microns. Loop  2  of end effector  100  may have a length LM1 as measured from the base of end effector  100  to the distal vertex  5 . Loop  1  and loop  3  may have a length LM2 as measured from the base of end effector  100  to the distal vertex  5 . As illustrated, length LM2 may be greater than length LM1. According to some embodiments, LM1 may be approximately 17 mm to approximately 24 mm, and LM2 may be approximately 18 mm to approximately 25 mm. Each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B, may form rows of a rectangular electrode grid when the electrodes  37  are in contact with the cardiovascular tissue. Along any given spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B, electrodes  37  may form longitudinal electrode pairs  37 A  between immediately adjacent electrodes  37 . Between any immediately adjacent spines (e.g.,  1 A &amp;  2 A,  2 A &amp;  3 A,  3 A &amp;  1 B,  1 B &amp;  2 B, and  2 B &amp;  3 B) electrode  37  on a first spine and a corresponding electrode  37  on a second spine may form lateral electrode pairs  37 B. As discussed above, longitudinal electrode pairs  37 A may consist of immediately adjacent electrodes  37  separated by distance Lg1. Lateral electrode pairs  37 B may consist of laterally adjacent electrodes  37  separated by a distance Lg2. According to some embodiments, end effector may be characterized by the distance Lg2 between lateral electrode pairs  37 B that is approximately twice that of distance Lg1 between longitudinal electrode pairs  37 A. 
       FIG.  2 B  illustrates a cross-sectional view through the connector tubing  46 . The connector  46  includes a tubular insert  200  that has its center coinciding with the longitudinal axis L-L. Orthogonal planes P 4  and P 5  are in alignment with the longitudinal axis to define four quadrants in the insert  200 . A parallel reference plane P 5  is approximately parallel to the end effector  100  illustrated in  FIG.  3   , below. An orthogonal reference plane P 4  is approximately orthogonal to the parallel reference plane P 5  and approximately parallel to the orthogonal axis O-O. Apertures  202 ,  204 ,  206 ,  208 ,  210 ,  212  of the insert  200  are sized, positioned, and otherwise configured for insertion of respective end segments  2 D,  2 E,  3 E,  1 E,  3 D,  1 D. Apertures  202 ,  204 ,  206 ,  208 ,  210 ,  212  may be disposed circumferentially about a center opening  214 . Center opening  214  is disposed at the intersection of orthogonal plane P 4  and orthogonal plane P 5  for insertion of puller wires, electrical wires, and/or as any other components to and from the end effector  100 . According to some embodiments, center opening  214  may house an irrigation port for providing irrigation to the vasculature or heart of a patient. Components which traverse the apertures  202 ,  204 ,  206 ,  208 ,  210 ,  212  and central opening  214  are not illustrated in  FIG.  2 B  for the purposes of illustration. 
     With this arrangement of apertures  202 ,  204 ,  206 ,  208 ,  210  and  212 , loop members  1 ,  2  and  3  are arrayed in a non-coplanar unconstrained arrangement, shown in the sectional view of  FIG.  2 C  (as viewed from the proximal end), whereby loop  3  defines a plane P 3  (demarcated by spines  3 A and  3 B with connector  3 C) that intersects orthogonal plane P 4  with loop  1  having a plane P 1  (demarcated by spines  1 A and  1 B with connector  1 C) that intersects both orthogonal planes P 4  and P 5  and loop  2  having a plane P 2  (demarcated by spines  2 A and  2 B and connector  2 C) that intersects orthogonal plane P 4  and is substantially parallel to orthogonal plane P 5 .  FIG.  2 D  is a view of the distal end of the end effector looking proximally. In particular, loop  1  (defined by spines  1 A,  1 B and connector  1 C) is arrayed to define plane P 1  that is contiguous to or extend through spines  1 A,  1 B and loop  1  whereas spines  2 A,  2 B and connector  2 C of loop  2  are arrayed to define a plane P 2  that intersects with plane P 1 . Spines  3 A,  3 B and connector  3 C of loop  3  are arrayed to define a plane P 3  that intersects with both planes P 1  and P 2 . The planes P 1 , P 2 , and P 3  defined by the respective loops  1 ,  2  and  3  are configured so that the loops  1 ,  2  and  3  are not contiguous to or arrayed such that a common plane passes through the loops. Thus, planes P 1 , P 2  and P 3  are non-parallel and intersect each other. It is noted that the longitudinal axis L-L may be contiguous to the second plane P 2 . In alternative embodiment, longitudinal axis L-L may be disposed in between a region bounded by planes P 1 , P 2  and P 3 . 
       FIGS.  2 A through  2 D  are one example of non-coplanar arrangement of loop members  1 ,  2 ,  3  in an end effector. There are numerous possible arrangements non-coplanar arrangements of loop members which can result in an end effector having the general appearance of the illustrated end effector  100 . 
       FIG.  3    is an illustration of a side view of the end effector  100 . The three loop members  1 ,  2 ,  3  overlap at a common distal vertex  5  along the longitudinal axis L-L. The end effector  100  is in an unconstrained configuration as illustrated in  FIG.  3   . When the end effector is unconstrained, the loop members  1 ,  2 ,  3  are not coplanar with each other.  FIG.  3    also illustrates an orthogonal axis O-O orthogonal to the longitudinal axis L-L and approximately orthogonal to the end effector  100 . 
       FIG.  4    is an illustration of a standard length end effector according to aspects of the present invention. As compared to the shortened end effector illustrated in  FIG.  2   , the standard length end effector has a different geometry as defined by the spacing between adjacent spines of the end effector  100 . For example, longitudinal electrode pairs  37 A along any given spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B, have a gap length Lg1, while lateral electrode pairs  37 B between two adjacent spines have a gap length Lg2. While the shortened end effector  100  may exhibit a lateral gap length Lg2 that is approximately twice the longitudinal gap length Lg1, the standard length end effector may exhibit a lateral gap length Lg2 approximately equal to the longitudinal gap length Lg1. Advantages of the shortened end effector design may include increased electrode density, improved maneuverability of the end effector within the heart and vasculature, improved conformance to the tissue while the end effector  100  is in the deployed configuration, and improved usability within patients that have more compact cardiac anatomies. 
       FIG.  5    is an illustration of the shortened length end effector  100 . As shown in  FIG.  5   , electrodes  37  disposed on spines  1 A,  2 A,  3 A,  1 B,  2 B, and  3 B may define an electrode grid. For example, rows I, II, III, IV, V, and VI define the rows of the electrode grid, and numbers  1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8  define the columns of the electrode grid. As shown, the electrode grid includes 48 electrodes  37 . The electrode grid may be substantially rectangular or square in shape, thereby allowing electrical signals propagating in orthogonal directions (e.g., a first electrical signal propagating along one of rows I-VI and a second electrical signal propagating along one of columns 1-8) to be measured with a high resolution due to the (rectangular or square) grid that end effector  100  provides. As discussed with respect to  FIG.  2   , shortened end effector may exhibit a lateral gap distance Lg2 that is approximately twice the longitudinal distance Lg1. Nevertheless, shortened end effector may provide equidistant electrode spacing by bypassing every other electrode in the longitudinal direction to provide for equidistantly spaced electrode bipoles in both the longitudinal (e.g., along rows I-VI) and the lateral (e.g., along columns 1-8) directions. For example, along any given row I, II, III, IV, V, and VI there exist numerous longitudinal electrode bipole pairs  37 A that have a gap distance equivalent to the lateral gap distance Lg2 (e.g., pair 1-3, pair 2-4, pair 3-5, pair 4-6, pair 5-7, and/or pair 6-8 along any given row I-VI). By providing lateral electrode bipole pairs as described above, shortened end effector  100  exhibits equidistantly spaced electrode bipole pairs in both the lateral and longitudinal directions while providing a more compact and easier to maneuver end effector for imaging the heart and surrounding vasculature. Closely-spaced electrode bipoles  37  allow for more accurate detection of near field pulmonary vein potential versus far field atrial signals, which is important when treating atrial fibrillation. More specifically, near pulmonary vein potentials are very small signals whereas atrial signals are typically far larger. Accordingly, a physician may encounter difficulty in determining whether a measured potential is due to a small, close potential (e.g., from the pulmonary vein) or a larger, albeit more distant potential (e.g., from the atria). The closely spaced electrode bipoles enabled by the shortened end effector  100  allow an operating physician to more accurately determine whether he is measuring a close signal or a far signal. Accordingly, by providing closely-spaced electrodes, the physician is able to target exactly the locations of myocardial tissue that have pulmonary vein potentials and therefore allows the physician to delivery therapy to the appropriate tissue. Additionally, the closely-spaced electrode electrodes allow the physician to determine the anatomical location of the ostium/ostia based on the measured electrical signal. 
       FIGS.  6 A and  6 B  are illustrations of views of the end effector pressed to a planar surface. In the illustrated example, the loop members  1 ,  2 ,  3  can be pressed to a planar surface S via manipulation of the shaft  9  of the device. More specifically, when the end effector  100  is positioned within a patient, manipulation of the catheter body  12  and the control handle  16  can be used to position the end effector  100  against a surface within a wall of an internal cavity of the patient such internal walls of the heart and/or blood vessels. When the end effector  100  is positioned against the planar surface S, a majority of each length of each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B can become contiguous and aligned to the planar surface. Further, when the end effector  100  is positioned against the planar surface S, a majority of each length of each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B can become aligned with a majority of each length of the other spines. The surface S need not necessarily be planar in order for the spines  1 A,  2 A,  3 A,  1 B,  2 B,  3 B to become contiguous and aligned to the surface. The end effector  100  may be able to conform to a curved surface, for instance. 
     As illustrated in  FIG.  6 B , when the majority of each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B is pressed to the surface S, the connecting segments  1 C,  2 C,  3 C can be stacked on top of the surface S at the distal vertex  5  at the linkage  50 . A first connecting segment  1 C nearest to the surface S can be separated from the surface S by the linkage  50 . A second connecting segment  3 C stacked onto the first connecting segment  1 C can be separated from the surface S by the linkage  50  and the first connecting segment  1 C. A third connecting segment  2 C can be separated from the surface S by the linkage  50  and the first and second connecting segments  1 C,  3 C. Therefore, at least a portion of each connecting segment  1 C,  2 C,  3 C can be separated from the planar surface S when the majority of each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B is pressed to the planar surface. Alternatively, the linkage  50  can be inset into the first connecting segment  1 C such that the first connecting segment is substantially contiguous to the planar surface S. In that case, only the second and third connecting segments  3 C,  2 C are separated from the planar surface S at the distal vertex  5 . 
     Proximal segments  1 D,  2 D,  3 D,  1 E,  2 E,  3 E of the loop members  1 ,  2 ,  3  can be bent such that at least a portion of each of the proximal segments curves away from the surface S. 
     When the majority of each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B is pressed to the surface S, at least some of the electrodes  37  on each spine can be in contact with the surface S. In some examples, every electrode  37  on each spine can be in contact with the surface S. 
     When the majority of each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B is pressed to the surface S, the majority of each respective length of each loop member can become contiguous to the surface S, where the respective length of each loop member includes the length of the respective loop member’s spines  1 A,  2 A,  3 A,  1 B,  2 B,  3 B, connectors  1 C,  2 C,  3 C, and proximal segments  1 D,  2 D,  3 D,  1 E,  2 E,  3 E (distal to the connector tubing  46 ). 
       FIG.  7 A  is an illustration depicting electrode spacing and dimensions on the shortened end effector. The electrodes  37  can include one or more pairs of closely-spaced bipolar electrodes  37  which are configured to pick up electrocardiogram signals from tissue. In the present example, the electrodes  37  of an adjacent longitudinal pair has a separation space gap distance Lg1 therebetween of approximately 1 mm to 200 microns and preferably no greater than about 200 microns. Each electrode  37  has an electrode area Ae and electrode length L. The electrode length can be from about 2 mm to about 0.5 mm. Each electrode  37  preferably has a length of 1 mm to 0.5 mm. The electrodes  37  as illustrated are cylindrical such that the electrode area is calculated as a produce of the circumference C and length L of the electrode. The spine has a diameter D. As described with reference to  FIG.  2 A  and  FIG.  5   , according to some embodiments, laterally spaced electrode pairs  37 B may have a gap distance Lg2. In some embodiments, the lateral gap distance Lg2 may be approximately twice the longitudinal gap distance Lg1. 
     Additionally, or alternatively, the electrodes  37  need not completely circumscribe the respective loop  1 ,  2 ,  3 ; in which case the electrodes  37  can have a rectangular shape that is rectilinear or arced having a width W such that the electrode area Ae is a produce of the electrode length L and width W, the width being the arc length when the rectangular shape is arced. In examples where the electrode pair configurations are in shapes other than rectilinear, rectangular, or cylindrical, a conversion factor CF may be used to determine the appropriate gap distance between the electrodes based on the known area of either one of the pair of electrodes. The conversion factor CF may range from about 2 to 0.1 in the inverse of the same root dimensional unit as the planar area of an electrode. In one example, where the planar area of one electrode is about 0.08 squared-mm, the smallest gap distance Lg1 along the longitudinal axis extending through both electrodes can be determined by applying the conversion factor CF (in the inverse of the same root dimensional unit of the area or mm) to arrive at a gap distance Lg1 of about 100 microns. In another example where the area of one electrode is 0.24 squared-mm, the conversion factor CF (in the inverse of the same root dimensional unit or mm -1 ) can be 1.25 mm -1  or less, giving the range of the smallest gap distance Lg1 from about 300 microns to about 24 microns. Regardless of the shape of the electrodes, a preferred conversion factor CF is about 0.8 (in the inverse of the same root dimensional unit for the electrode area). 
       FIG.  7 B  is another illustration of the shortened end effector  100  including a mechanical linkage  50 . At least one pair of closely-spaced bipolar microelectrodes  37  is provided on each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B in the present example. More particularly, each spine  1 A,  2 A,  3 A,  1 B,  2 B,  3 B carries four pairs of adjacent bipolar microelectrodes  37  corresponding to eight microelectrodes  37  per spine. This number may be varied as desired. As discussed with respect to  FIG.  5   , in some embodiments, the end effector  100  may provide electrode bipoles that bypass every other electrode in the longitudinal direction to provide for equidistantly spaced electrode bipoles in both the longitudinal (e.g., along rows I-VI of  FIG.  5   ) and the lateral (e.g., along columns 1-8 of  FIG.  5   ) directions.  FIG.  5    also illustrates a mechanical linkage  50  coupling connectors  1 C,  2 C,  3 C together in a single connection point. The mechanical linkage  50  functions to maintain a spatially fixed arrangement between the loops  1 ,  2 ,  3  at the common distal vertex  5 . 
       FIG.  7 C  is an illustrations of an interior loop member lumen. As shown in  FIG.  7 C , interior loop member lumen may include an inner housing  94  and outer housing  90  surrounding a support frame  81 . The illustrated interior loop member lumen can be used in loop members  1 ,  2 ,  3  illustrated and otherwise disclosed herein according to the teachings herein. The outer housing  90  can include polymeric tube (e.g. thermoplastic polyurethane) having a single lumen sized to house the support frame  81  and wires  40  that provide electrical connections to the end effector electrodes  37 . The lumen of the outer housing  90  can also be sized to house an irrigation tube  96  having an irrigation lumen therethrough. In this configuration, the support frame is surrounded by a sleeve to isolate its edges from damaging the conductors. The inner housing  94  can be shaped, sized, and otherwise configured to closely surround the support frame  81 . The inner housing  94  can include a polymeric material, for example a shrink sleeve applied during a reflow process. Because neither the wires  40  nor the irrigation tube  96  need extend beyond the spines of the loop member, the outer housing  90  need not cover the connector segment of the loop member. Within the outer housing  90 , the inner housing  94  can be bonded to the outer housing  90 . The bond between the inner housing  94  and outer housing  90  can inhibit fluid leakage. The bond between the inner housing  94  and outer housing  90  can promote conformity of the shape of the outer housing  90  to that of the support frame  81  inhibiting shifting of the support frame  81  within the outer housing  90  when the end effector  100  is deformed from its unconstrained configuration. 
       FIG.  8    is an illustration of an exemplary medical procedure and associated components of a cardiac electrophysiology (EP) mapping catheter system that may utilize the apparatus  10  (also referred to as a catheter assembly). A physician PH is illustrated grasping the handle  16  of the apparatus, with the end effector  100  (not shown in  FIG.  8   ) disposed in a patient PA to perform EP mapping in or near the heart H of the patient PA. The apparatus  10  is coupled with a guidance and drive system  110  via a cable  130 . The apparatus  10  can optionally be coupled with a fluid source  142  via a fluid conduit  140 . A set of field generators  120  are positioned underneath the patient PA and are coupled with guidance and drive system  110  via another cable  122 . Field generators  120  are also optional. 
     The guidance and drive system  110  can include a console  112  and a display  118 . The console  112  can include a first driver module  114  and a second driver module  116 . The first driver module  114  can be coupled with the apparatus via a cable  130 . In some variations, the first driver module  114  is operable to receive EP mapping signals obtained via electrodes  37  of end effector  100 . The console  112  can include a processor (not shown) that processes such EP mapping signals and thereby provides EP mapping. In addition, or in the alternative, the first driver module  114  may be operable to provide RF power to the electrodes  37  of end effector  100  to thereby ablate tissue. In some versions, the first driver module  114  is also operable to receive position indicative signals from a position sensor in end effector  100 . In such versions, the processor of console  112  is also operable to process the position indicative signals from the position sensor to thereby determine the position of the end effector  100  within the patient PA. 
     The guidance and drive system  110  can further include non-transitory computer readable medium with instructions thereon to cause the drive system  110  to perform functionality described herein and/or as are known related to use of similar equipment. In some examples, the non-transitory computer readable memory can be in communication with the first driver module  114  (e.g. by virtue of being in communication with a processor of the first driver module  114  and/or the processor of the console  112 ). The non-transitory computer readable medium can include instructions thereon that when executed by the first driver module  114  cause the first driver module  114  to receive EP mapping signals from the spine electrodes  37  and a reference signal from one of distal electrode  38 D, proximal electrode  38 P, or a combinations of both. 
     The second driver module  116  is coupled with field generators  120  via a cable  122 . The second driver module  116  is operable to activate field generators  120  to generate an alternating magnetic field around the heart H of the patient PA. For instance, the field generators  120  may include coils that generate alternating magnetic fields in a predetermined working volume that contains the heart H. 
     Some versions of the apparatus  10  include a position sense near or within the end effector  100  that is operable to generate signals that are indicative of the position and orientation of end effector  100  within the patient PA. Each position sensor may include a wire coil or a plurality of wire coils (e.g., three orthogonal coils) that are configured to generate electrical signals in response to the presence of an alternating electromagnetic field generated by field generators  120 . Other components and techniques that may be used to generate real-time position data associated with end effector  100  may include wireless triangulation, acoustic tracking, optical tracking, inertial tracking, and the like. By way of example only, position sensing may be provided in accordance with at least some of the teachings of U.S. Pat. No. 9,480,416, which is incorporated herein by reference and attached to the Appendix of priority application U.S. 63/279,747. Alternatively, apparatus  10  may lack a position sensor near the end effector  100 . 
     The display  118  is coupled with the processor of console  112  and is operable to render images of patient anatomy. Such images may be based on a set of preoperatively or intraoperatively obtained images (e.g., a CT or MRI scan, 3-D map, etc.). The views of patient anatomy provided through the display  118  may also change dynamically based on signals from the position sensor near the end effector  100 . 
     The processor of the console  112  may also drive the display  118  to superimpose the current location of end effector  100  on the images of the patient’s anatomy, such as by superimposing an illuminated dot, a crosshair, a graphical representation of end effector  100 , or some other form of visual indication. 
     The fluid source  142  can include a bag containing saline or some other suitable irrigation fluid. The conduit  140  can include a flexible tube that is further coupled with a pump  144 , which is operable to selectively drive fluid from the fluid source  142  to the irrigation tube  15  of the apparatus  10 . In some variations, such as including a reference electrode  38 D and/or  38 P as configured in  FIG.  5   , the conduit  140 , fluid source  142 , and pump  144  are omitted entirely. 
       FIG.  9    is a flowchart of an exemplary method of treating a patient utilizing the apparatus according to aspects of the present invention. In step  905 , the method may include moving a distal portion of an elongated shaft (e.g., elongated shaft of  FIG.  1   ) and an end effector (e.g., end effector  100 ) extending distally from the distal portion through a catheter (e.g., catheter  10 ) and into a heart. The elongated shaft may define a longitudinal axis (e.g., longitudinal axis L-L) and the end effector may include a plurality of electrodes (e.g., electrodes  37 ) that are disposed on a plurality of equidistantly spaced spine members parallel to the longitudinal axis (e.g., spines  1 A,  1 B,  2 A,  2 B,  3 A,  3 B). The plurality of electrodes may be arranged in a grid (e.g., as shown in  FIG.  5   ) with the plurality of electrodes forming rows of the grid. 
     In step  910 , the method may include moving the end effector from a distal end of the catheter via manipulation of a proximal portion of the elongated shaft (e.g., control handle  16 , as shown in  FIG.  1   ). In step  915 , the method may include contacting a plurality of electrodes (e.g., electrodes  37 ), carried by the end effector (e.g., end effector  100 ), to heart tissue via manipulation of the proximal portion of the elongated shaft. In step  920 , the method may include activating one or more first electrode bipoles (e.g., electrode bipole  37 A) disposed on at least one spine member. The first electrode bipole may consist of two electrodes having at least a third electrode positioned between the two electrodes. As discussed with respect to  FIG.  5   , a bipole configuration that skips every other electrode on a given spine allows for the shortened end effector  100  to provide a longitudinal gap distance Lg1 approximately equivalent to the lateral gap distance Lg2 of the shortened end effector  100 . 
     In optional step  925 , the method may include activating a first electrode bipole disposed on a first spine member and a second electrode bipole (e.g., lateral bipole  37 B) disposed orthogonally to the longitudinal axis along a respective row of the grid. 
     In step  930 , the method may include receiving, while the plurality of electrodes are in contact with the heart tissue, electrical potentials via the one or more first electrode bipoles (e.g., longitudinal bipoles  37 A). In optional step  935  the method may include receiving, while the plurality of electrodes are in contact with the heart tissue, electrical potentials via the one or more second electrode bipoles (e.g., lateral bipoles  37 B). 
     The descriptions contained herein are examples of embodiments of the invention and are not intended in any way to limit the scope of the invention. As described herein, the invention contemplates many variations and modifications of system components, including alternative combinations of components illustrated in separate figures, alternative materials, alternative component geometries, and alternative component placement. Modifications and variations apparent to those having skilled in the pertinent art according to the teachings of this disclosure are intended to be within the scope of the claims which follow.