Patent Publication Number: US-2022233147-A1

Title: Catheter with capacitive force sensor

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application is a divisional of and claims priority to U.S. patent application Ser. No. 15/986,730, filed May 22, 2018, now U.S. Pat. No. 11,298,082, the entire content of which is incorporated herein by reference. 
    
    
     FIELD OF INVENTION 
     This invention relates to medical devices. More particularly, this invention relates to improvements in cardiac catheterization, including electrophysiologic (EP) catheters, in particular, EP catheters for mapping and/or ablating ostia and tubular regions in the heart. 
     BACKGROUND 
     Cardiac arrhythmias, such as atrial fibrillation, occur when regions of cardiac tissue abnormally conduct electric signals to adjacent tissue, thereby disrupting the normal cardiac cycle and causing asynchronous rhythm. 
     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. By selectively ablating cardiac tissue by application of energy via a catheter, it is sometimes 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. 
     Circumferential lesions at or near the ostia of the pulmonary veins have been created to treat atrial arrhythmias. U.S. Pat. Nos. 6,012,457 and 6,024,740, both to Lesh, disclose a radially expandable ablation device, which includes a radiofrequency electrode. Using this device, it is proposed to deliver radiofrequency energy to the pulmonary veins in order to establish a circumferential conduction block, thereby electrically isolating the pulmonary veins from the left atrium. 
     U.S. Pat. No. 6,814,733 to Schwartz et al., which is commonly assigned herewith and herein incorporated by reference, describes a catheter introduction apparatus having a radially expandable helical coil as a radiofrequency emitter. In one application the emitter is introduced percutaneously, and transseptally advanced to the ostium of a pulmonary vein. The emitter is radially expanded, which can be accomplished by inflating an anchoring balloon about which the emitter is wrapped, in order to cause the emitter to make circumferential contact with the inner wall of the pulmonary vein. The coil is energized by a radiofrequency generator, and a circumferential ablation lesion is produced in the myocardial sleeve of the pulmonary vein, which effectively blocks electrical propagation between the pulmonary vein and the left atrium. 
     Another example is found in U.S. Pat. No. 7,340,307 to Maguire, et al., which proposes a tissue ablation system and method that treats atrial arrhythmia by ablating a circumferential region of tissue at a location where a pulmonary vein extends from an atrium. The system includes a circumferential ablation member with an ablation element and includes a delivery assembly for delivering the ablation member to the location. The circumferential ablation member is generally adjustable between different configurations to allow both the delivery through a delivery sheath into the atrium and the ablative coupling between the ablation element and the circumferential region of tissue. 
     More recently, inflatable catheter electrode assemblies have been constructed with flex circuits to provide the outer surface of the inflatable electrode assemblies with a multitude of very small electrodes. Examples of catheter balloon structures are described in U.S. Publication No. 2016/0175041, titled Balloon for Ablation Around Pulmonary Vein, the entire content of which is incorporated herein by reference. 
     Flex circuits or flexible electronics involve a technology for assembling electronic circuits by mounting electronic devices on flexible plastic substrates, such as polyimide, Liquid Crystal Polymer (LCP), PEEK or transparent conductive polyester film (PET). Additionally, flex circuits can be screen printed silver circuits on polyester. Flexible printed circuits (FPC) are made with a photolithographic technology. An alternative way of making flexible foil circuits or flexible flat cables (FFCs) is laminating very thin (0.07 mm) copper strips in between two layers of PET. These PET layers, typically 0.05 mm thick, are coated with an adhesive which is thermosetting, and will be activated during the lamination process. Single-sided flexible circuits have a single conductor layer made of either a metal or conductive (metal filled) polymer on a flexible dielectric film. Component termination features are accessible only from one side. Holes may be formed in the base film to allow component leads to pass through for interconnection, normally by soldering. 
     Because the quality of a lesion depends on a number of factors, including size and depth, the force at which an electrode contacts tissue is a useful to a medical professional when ablating tissue. And because an ablating electrode has many possible configurations, including a tip electrode, a ring electrode or an electrode on a balloon, a force sensor should be adaptable for use with any such electrodes, so that force can be measured whether tissue contact occurs at a catheter&#39;s distal tip as a point contact on tissue or its side while being dragged along tissue, or even simultaneously at multiple tissue surface locations circumferentially within an ostium or tubular region.’ 
     Accordingly, there is a desire for a catheter having an electrode with a force sensor that is configured for measuring a force applied by the electrode against tissue surface. And because a capacitive tactile sensor is reliably responsive to the an applied force and can be manufactured in very small sizes, an electrode having a capacitive force sensor can reliably measure an applied force whether the electrode is configured as a tip electrode, a ring electrode or even as an electrode on a balloon catheter. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an electrophysiology catheter with a micro capacitive tactile sensor provided in the distal section where tissue contact occurs, wherein the distal section may include a tip electrode, a ring electrode and/or a balloon catheter. The capacitive sensor is configured to exhibit a change in capacitance upon touching tissue and during tissue contact wherein the force applied with tissue contact is measured and reliably calibrated in assessing and determining the applied force. 
     In some embodiments, the catheter has an elongated catheter shaft, a distal tip electrode having a shell configured for contact with tissue and a capacitive force sensor having a first plate affixed to the shell, a second plate distal of the first plate and configured for contact with the tissue, and an elastically compressible dielectric between the first and second plates, wherein the force sensor has a first capacitance when the first and second plates are separated by a first distance, and the force sensor has a second capacitance when the first and second plates are separated by a second different from the first distance. The catheter also includes a first terminal connected to the first plate, and a second terminal connected to the second plate. 
     In some embodiments, the first and second plates are parallel to each other. 
     In some embodiments, the first and second plates are generally of the same size and shape. 
     In some embodiments, the capacitive force sensor is affixed to a distal face of the shell. 
     In some embodiments, the first plate protrudes above an outer surface of the shell. 
     In some embodiment, the shell has a recess and the capacitive force sensor is situated in the recess with at least the first plate exposed. 
     In some embodiments, the recess is formed in a distal face of the shell. 
     In some embodiments, the recess is formed in a circumferential wall of the shell. 
     In some embodiments, the first terminal passes through a first through-hole formed in the shell. 
     In some embodiments, the second terminal passes through a second through-hole formed in the shell. 
     In some embodiments, the first terminal extends along an outer surface of the shell. 
     In some embodiments, an electrophysiology catheter adapted for use in an ostium, includes a balloon having an membrane and configured with a distal end and a proximal end defining a longitudinal axis and at least one circumferential latitude, and a micro capacitive force sensor having a first plate on the balloon, a second plate configured for contact with the tissue, and an elastically compressible dielectric between the first and second plates, wherein the force sensor has a first capacitance when the first and second plates are separated by a first distance, and the force sensor has a second capacitance when the first and second plates are separated by a second different from the first distance. The catheter also has a first terminal connected to the first plate, and a second terminal connected to the second plate. 
     In some embodiments, the first plate is affixed to the membrane. 
     In some embodiments, the catheter also includes a contact electrode and the first plate is affixed to the contact electrode. 
     In some embodiments, the contact electrode is configured with an elongated body and a plurality of transverse members. 
     In some embodiments, the catheter also includes a first via through the membrane, wherein the first terminal is connected to the first via. 
     In some embodiments, the catheter also includes a second via through the membrane, the second terminal connected to the second via. 
     In some embodiments, the catheter includes a plurality of capacitive force sensors arranged along a circumferential latitude of the balloon. 
     In some embodiments, an electrophysiology catheter system having a catheter having a capacitive force sensor with has a first plate, a second plate, and a dielectric therebetween, and a processor having a memory device and a voltage source. The catheter also includes a first terminal connected to the first plate and the voltage source, and a second terminal connected to the second plate and the voltage source, wherein the memory device is configured to store instructions that, when executed by the processor, causes the processor to: actuate the voltage source, determine a capacitance across the capacitive force sensor, and detect a change in the capacitance. 
     In some embodiments, the capacitive force sensor has a first capacitance when the first and second plates are separated by a first distance, and the capacitive force sensor has a second capacitance when the first and second plates are separated by a second distance, and the processor is configured to detect the change in capacitance between the first and second capacitance. 
     In some embodiments, the dielectric is compressible. 
     In some embodiments, the dielectric is elastically compressible. 
     In some embodiments, the capacitive force sensor is positioned on a distal portion of the catheter configured for tissue contact. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features and advantages of the present invention will be better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings. It is understood that selected structures and features have not been shown in certain drawings so as to provide better viewing of the remaining structures and features. 
         FIG. 1  is a schematic illustration of a medical procedure, according to an embodiment of the present invention. 
         FIG. 2  is a perspective view of a catheter suitable for use in the medical procedure of  FIG. 1 , according to an embodiment of the present invention. 
         FIG. 3  is an end cross-sectional view of a catheter body of the catheter of  FIG. 2 . 
         FIG. 4  is an end cross-sectional view of a deflection section of the catheter of  FIG. 2 . 
         FIG. 5A  is side cross-sectional view of a distal section of the catheter of  FIG. 2 , including a distal tip electrode with a capacitive force sensor in a neutral configuration. 
         FIG. 5B  is a detailed cross-sectional view of the capacitive force sensor of  FIG. 5A  in a tissue contact or compressed configuration. 
         FIG. 5C  is an end cross-sectional view of a proximal end of the distal tip electrode of  FIG. 5A , taken along line C-C. 
         FIG. 6  is a side cross-sectional view of a distal section of a catheter, in accordance with another embodiment of the present invention. 
         FIG. 7  is a top plan view of a balloon catheter suitable for use in the medical procedure of  FIG. 1 , according to another embodiment of the present invention. 
         FIG. 8  is a perspective view of a balloon of the balloon catheter of  FIG. 7 , along with a lasso catheter inserted therethrough. 
         FIG. 9  is a perspective view of a flexible circuit electrode assembly partially lifted off the balloon to reveal its underside and related elements, according to an embodiment of the present invention. 
         FIG. 10A  is an exploded view of a flexible circuit electrode assembly during a stage of construction, according to an embodiment of the present invention. 
         FIG. 10B  is a side cross-sectional view of a via formed in a balloon membrane, according to an embodiment of the present invention. 
         FIG. 11  is a detailed perspective view of a balloon membrane with capacitive force sensors, according to an embodiment of the present invention. 
         FIG. 12  is a detailed, exploded perspective view of a capacitive force sensor, according to another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     System Description 
     In the following description, like elements in the drawings are identified by like numerals, and like elements are differentiated as necessary by appending a letter to the identifying numeral. 
       FIG. 1  is a schematic illustration of an invasive medical procedure using apparatus  12 , according to an embodiment of the present invention. The procedure is performed by a medical professional  14 , and, by way of example, the procedure in the description hereinbelow is assumed to comprise ablation of a portion of a myocardium  16  of the heart of a human patient  18 . However, it is understood that embodiments of the present invention are not merely applicable to this specific procedure, and may include substantially any procedure on biological tissue or on non-biological materials. 
     In order to perform the ablation, medical professional  14  inserts a probe  20  into a sheath  21  that has been pre-positioned in a lumen of the patient. Sheath  21  is positioned so that a distal end  22  of probe  20  enters the heart of the patient. A catheter  24 , which is described in more detail below, is deployed through a lumen  23  of the probe  20 , and exits from a distal end of the probe  20 . 
     As shown in  FIG. 1 , apparatus  12  is controlled by a system processor  46 , which is located in an operating console  15  of the apparatus. Console  15  comprises controls  49  which are used by professional  14  to communicate with the processor. During the procedure, the processor  46  typically tracks a location and an orientation of the distal end  22  of the probe  20 , using any method known in the art. For example, processor  46  may use a magnetic tracking method, wherein magnetic field generators  25 X,  25 Y and  25 Z external to the patient  18  generate signals in coils positioned in the distal end of the probe  20 . The CARTO® available from Biosense Webster, Inc. of Diamond Bar, Calif., uses such a tracking method. 
     The software for the processor  46  may be downloaded to the processor in electronic form, over a network, for example. Alternatively or additionally, the software may be provided on non-transitory tangible media, such as optical, magnetic, or electronic storage media. The tracking of the distal end  22  is typically displayed on a three-dimensional representation  60  of the heart of the patient  18  on a screen  62 . 
     In order to operate apparatus  12 , the processor  46  communicates with a memory  50 , which has a number of modules used by the processor to operate the apparatus. Thus, the memory  50  comprises a temperature module  52 , an ablation module  54 , and an electrocardiograph (ECG) module  56 . The memory  50  typically comprises other modules, such as a force sensor module  53 , with a voltage source  51 , for sensing the force on the distal end  22 . The memory  50  may also include a tracking module  55  for operating the tracking method used by the processor  46 , and an irrigation module  57  allowing the processor to control irrigation provided for the distal end  22 . The modules may comprise hardware as well as software elements. 
     Catheter 
       FIG. 2  is a schematic perspective view of a catheter  100  suitable for use with the aforementioned apparatus  12 . The catheter  100  has an elongated catheter body  102 , a deflection section  103  and a distal section  104  which includes a distal tip electrode  105 . As understood in the art, in some embodiments, the catheter body  102  has an outer wall  120  with a central lumen  121 , which may be lined with a stiffener tubing  122 , as shown in  FIG. 3 . Various components pass through the lumen  121 , including, for example, lead wires  130  for the tip electrode  105  and any ring electrodes (not shown), a pair of deflection puller wires (or tensile members)  131 A,  131 B, an irrigation tubing  132 , a cable  133  for an EM position sensor (not shown) housed in the distal section  104 , thermocouple wire or wire pair  151 / 153 , and any other cables or wires. 
     As understood in the art, in some embodiments, the deflection section  103  includes a shorter section of multi-lumened tubing  110  with multiple lumens. As shown in  FIG. 4 , the lumens include, for example, a first lumen  111  for the lead wires  130  and thermocouple wire or wire pair  151 / 153 , a second lumen  112  for the first puller wire  131 A, a third lumen  113  for the cable  133 , a fourth lumen  114  for the second puller wire  131 B, and a fifth lumen  115  for the irrigation tubing  132 . The size, shape and location of the lumens are not critical, except that the second and fourth lumens  122  and  124  may be off-axis and diametrically opposed for effective bi-directional deflection of the deflection section  103 . As understood in the art, portions of the puller wires  131 A,  131 B extending through the catheter body  102  are surrounded by respective compression coils  116  which generally limit deflection curvature of the catheter to the multi-lumened tubing  110  of the deflection section  103 , distal of the catheter body  102 . Portions of the puller wires  131 A,  131 B distal of the catheter body  102  are surrounded by respective protective sheaths  117  which prevent the puller wires from cutting into the side wall of the multi-lumened tubing  110  when the deflection section  103  is deflected. 
     As shown in  FIG. 5A . the tip electrode  105  of the distal section  104  has a shell  106  and a plug  107  defining an interior chamber  109  through which irrigation fluid enters the interior chamber  109  via a distal end section of the irrigation tubing  132  that passes through the plug  107  via a through-hole  108 . A distal end of lead wire  130  for tip electrode  105  terminates in a blind hole  123  formed in a proximal face of the plug  107 . Distal ends of thermocouple wire(s)  151  terminate in a blind hole  124  formed in the proximal face of the plug  107 . 
     On an outer surface  134  of a distal wall  135  of the shell  106 , a capacitive force sensor  136  is provided to sense the application of a force, including a force with any normal component, on the distal wall  135 , for example, when the distal wall  135  comes into contact with tissue surface  128  (see  FIG. 5B ). The capacitive force sensor  136  is situated in a recess  140  formed in the distal wall  135 , for example, by stamping (solid line) or shallow boring (broken line), and has two conductive plates  137 ,  138  and a dieletric  139  in between. It is understood that the recess  140  may also be formed in a circumferential sidewall  126  of the shell  106  for tissue contact when the distal section  104  lays against tissue and is dragged along the tissue surface. 
     In some embodiments, the plates are of similar construction in shape and size and are generally parallel to each other. With the plates  137  and  138  separated from each other by a distance D when the capacitive force sensor  136  is in its neutral state, the capacitive force sensor  136  has a thickness T while in its neutral state, free from any forces or contact. However, the dielectric has an elastic structure allowing deformation, including compression between the plates when the capacitive force sensor  136  is subjected to a force with a vector component perpendicular to the distal wall  135  of the tip shell  106 . Advantageously, the capacitance of the force sensor  136  changes when the distance between the plates  137  and  138  changes. In particular, the capacitance of the force sensor  136  increases when the distance between the plates decreases. 
     As shown in  FIG. 5A , the inner plate  137  is affixed to surface  134  in the recess  140 , for example, by adhesive  141 , and in some embodiments, the plates  137  and  138  are generally parallel to the distal wall  135 . The depth of the recess  140  is less than the thickness T of the capacitive force sensor  136  in its neutral state so that the outer plate  138  is projected out in front of the distal wall  135  and is exposed so that it can be pressed toward the plate  137  upon contact with the tissue surface  128  when the catheter is advanced toward the tissue surface for mapping and/or ablation. 
     The first plate  137  is connected to a first terminal  117  and the second plate is connected to a second terminal  118 , each of which may take the form of a lead wire that passes through respective apertures  127  and  129  formed in the distal wall  135  of the shell  106 . The terminals  117  and  118 , appropriately protected by insulating sheaths (not shown), extend through the interior chamber  109  and a common or different through-hole(s)  119  formed in the plug  107  (see  FIG. 5C ). In some embodiments, a short, single-lumened connector tubing  144  extends between the distal end of the multi-lumened tubing  110  and the tip electrode  105 , to allow components to reorient as needed between their respective lumen and their respective blind holes or through-holes in the plug  107  of the tip electrode  105 . 
     In use, the capacitance of the force sensor  136  is measured by the force sensing module  53  of the operating console (see  FIG. 1 ). A voltage is applied across the capacitive force sensor  136  by the voltage source  51  of the force sensing module  53  via the terminals  117 ,  118 . The capacitance for the force sensor  136  in the neutral state with the plates  137  and  138  separated by a distance D (see  FIG. 5A ) is measured by the force sensing module  53  as C. When the tip electrode  105  approaches tissue, the tissue surface  128  contacts protruding outer plate  138  and exerts a force with a normal force component N which compresses the dielectric  139  changing the separation distance from D to D 1  (see  FIG. 5B ), where D 1 &lt;D, which changes the capacitance of the force sensor  136  from C to C 1 , where C 1 &gt;C. The force sensing module  53  detects the increase capacitance C 1  and, for example, responds by providing an indicia to the medical professional  14 , such as activating an audio signal and/or a visual signal. The measured capacitance remains at C 1  so long as the normal force component N remains. Where the normal force component increases (such as where the medical professional further presses the distal tip electrode into the tissue surface), the separation distance decreases further to D 2  where D 2 &lt;D 1 &lt;D and the measured capacitance increases correspondingly to C 2 , where C 2 &gt;C 1 &gt;C. Where the normal force component decreases (such as where the medical professional begins to retract the distal trip electrode from the tissue surface, the separation distance increases to D 3  where D 1 &lt;D 3 &lt;D, and the measured capacitance decreases correspondingly to C 3 , where C 1 &gt;C 3 &gt;C. In this manner, the change in the capacitance output of the force sensor  136  from C 1  to C 3  is detected and measured by the force sensor  136  which advantageously indicates the change in force applied to the tip electrode  105  that is reflective of the change in tissue contact between the tip electrode and tissue surface, for example, by changing the audio signal and/or the visual signal. 
     In some embodiments, the terminals  117  and  118  are connected to electrical extensions (e.g., embedded lead wires, not shown) of a flex circuit  145  that is affixed to the outer surface  134  of the shell  106 , as shown in  FIG. 6 . The flex circuit  145  or the embedded lead wires pass through one or more sealed through-holes  146  formed in the sidewall of the connector tubing  144  to enter into the lumen of the connector tubing  144  and proximally into an appropriate lumen of the multi-lumened tubing  110 . 
     In some embodiments, a catheter  224  has a distal inflatable member or balloon  280 , as shown in  FIG. 7  in an inflated deployed configuration. The balloon  280  is used to ablate an ostium  211  of a lumen, such as a pulmonary vein  213 . The inflatable balloon  280  of the catheter  224  has an exterior wall or membrane  226  of a bio-compatible material, for example, formed from a plastic such as polyethylene terephthalate (PET), polyurethane or PEBAX®. The balloon  280  is deployed, in a collapsed uninflated configuration and may be inflated and deflated by injection and emission of a fluid such as saline solution through a shaft  270 . The membrane  226  of the balloon  280  is formed with irrigation pores or apertures  227  through which the fluid can exit from the interior of the balloon  280  to outside the balloon for cooling the tissue ablation site at the ostium. While  FIG. 7  shows fluid exiting the balloon as jet streams, it is understood that the fluid may exit the balloon with any desired flow rate and/or pressure, including a rate where the fluid is seeping out of the balloon. A suitable balloon is described in U.S. application Ser. No. 15/360,966, filed Nov. 23, 2016, the entire disclosure of which is incorporated herein by reference. 
     The membrane  226  supports and carries a combined electrode and temperature sensing member which is constructed as a multi-layer flexible circuit electrode assembly  284 . The “flex circuit electrode assembly”  284  may have many different geometric configurations. In the illustrated embodiment of  FIG. 8 , the flex circuit electrode assembly  284  has a plurality of strips  230 . The leaves  230  are generally evenly distributed about the distal end  288  and the balloon  280 . One or more contact electrodes  233  on each leaf come into galvanic contract with the ostium  211  during an ablation procedure, during which electrical current flows from the contact electrodes  233  to the ostium  211  to form lesions  231 . 
     For simplicity, the flex circuit electrode assembly  284  is described with respect to one of its leaf  230  as shown in  FIG. 9 , although it is understood that following description may apply to each leaf of the assembly. The flex circuit electrode assembly  284  includes a flexible and resilient sheet substrate  234 , constructed of a suitable bio-compatible materials, for example, polyimide. In some embodiments, the sheet substrate  234  has a greater heat resistance (or a higher melting temperature) compared to that of the balloon membrane  226 . In some embodiments, the substrate  234  is constructed of a thermoset material having a decomposition temperature that is higher than the melting temperature of the balloon membrane  226  by approximately 100C or more. 
     The substrate  234  is formed with one or more irrigation pores or apertures  235  that are in alignment with the irrigation apertures  235  of the balloon membrane  226  so that fluid in the interior of the balloon can pass through the irrigation apertures  235  and exit the balloon to the ablation sites on the ostium. 
     The substrate  234  has a first or outer surface  236  facing away from the balloon membrane  226 , and a second or inner surface  237  facing the balloon membrane  226 . On its outer surface  236 , the substrate  234  supports and carries the contact electrodes  233  adapted for tissue contact with the ostium. On its inner surface  237 , the substrate  234  supports and carries a wiring electrode  238 . The contact electrode  233  delivers RF energy to the ostium during ablation and/or is connected to a thermocouple junction for temperature sensing of the ostium. In the illustrated embodiment, the contact electrode  233  has a longitudinally elongated portion  240  and a plurality of thin transversal linear portions or fingers  241  extending generally perpendicularly from each lateral side of the elongated portion  240  between enlarged proximal and distal ends  242 P and  242 D, generally evenly spaced therebetween. The elongated portion  240  has a greater width and each of the fingers has a generally uniform lesser width. Accordingly, the configuration or trace of the contact electrode  233  resembles a “fishbone.” In contrast to an area or “patch” ablation electrode, the fingers  241  of the contact electrode  233  advantageously increase the circumferential or equatorial contact surface of the contact electrode  233  with the ostium while void regions  243  between adjacent fingers  241  advantageously allow the balloon  280  to collapse inwardly and/or expand radially as needed at locations along its equator. In the illustrated embodiment, the fingers  241  have different lengths, some being longer, others being shorter For example, the plurality of fingers include a distal finger, a proximal finger and fingers therebetween, where each of the fingers in between has a shorter adjacent finger. For example, each finger has a length different from its distal and/or proximal immediately adjacent neighboring finger(s) such that the length of each finger generally follows the tapered configuration of each leaf  230 . In the illustrated embodiment, there are 222 fingers extending across (past each lateral side of) the elongated portion  240 , with the longest finger being the third finger from the enlarged proximal end  242 P. In some embodiments, the contact electrode  233  includes gold  258 B with a seed layer  245 , between the gold  258 B and the membrane  226  (see  FIG. 10A  and  FIG. 10B ). The seed layer may include titanium, tungsten, palladium, silver, and/or combinations thereof. 
     Formed within the contact electrode  233  are one or more exclusion zone  247 , each surrounding an irrigation aperture  227  formed in the substrate  234 . The exclusion zones  247  are voids purposefully formed in the contact electrode  233 , as explained in detail further below, so as to avoid damage to the contact electrode  233  during construction of the electrode assembly  284  in accommodating the irrigation apertures  227  at their locations and in their function. 
     Also formed in the contact electrode  233  are one or more conductive blind vias  248  which are conductive or metallic formations that extend through through-holes (not shown) in the substrate  234  and are configured as electrical conduits connecting the contact electrode  233  on the outer surface  236  and the wiring electrode  238  on the inner surface  237 . It is understood that “conductive” is used herein interchangeably with “metallic” in all relevant instances. 
     On the inner surface  237  of the substrate  234 , the wiring electrode  238  is generally configured as an elongated body generally similar in shape and size to the elongated portion  240  of the contact electrode  233 . The wiring electrode  238  loosely resembles a “spine” and also functions as a spine in terms of providing a predetermined degree of longitudinal rigidity to each leaf  230  of the electrode assembly  284 . The wiring electrode  238  is positioned such that each of the blind vias  248  is in conductive contact with both the contact electrode  233  and the wiring electrode  238 . In the illustrated embodiment, the two electrodes  233  and  238  are in longitudinal alignment with other, with all nine blind vias  248  in conductive contact with both electrodes  233  and  238 . In some embodiments, the wiring electrode  238  has an inner portion of copper and an outer portion of gold. 
     The wiring electrode  238  is also formed with its exclusion zones  259  around the irrigation apertures  235  in the substrate  234 . The wiring electrode  238  is further formed with solder pad portions  261 , at least one active  261 A, and there may be one or more inactive solder pad portions  261 B. The solder pad portions  261 A and  261 B are extensions from a lateral side of the elongated body of the wiring electrode  238 . In the illustrated embodiment, an active solder pad portion  261 A is formed at about a mid-location along the elongated body, and a respective inactive solder pad portion  261 B is provided at each of the enlarged distal end  242 D and the enlarged proximal end  242 P. 
     Attached, e.g., by a solder weld  263 , to the active solder pad portion  261 A are the wire pair, e.g., a constantan wire  251  and a copper wire  253 . The copper wire  253  provides a lead wire to the wiring electrode  233 , and the copper wire  253  and the constantan wire  251  provide a thermocouple whose junction is at solder weld  263 . The wire pair  251 / 253  are passed through a through-hole  229  formed in the membrane  226  into the interior of the balloon  280 . It is understood that, in other embodiments in the absence of the through-hole  229 , the wire pair  251 / 253  may run between the membrane  226  and the substrate  234  and further proximally between the membrane  226  and a proximal tail  230 P until the wire pair  251 / 253  enters the tubular shaft  270  via a through-hole (not shown) formed in the tubular shaft sidewall near its distal end. 
     The flex circuit electrode assembly  284 , including the leaves  230  and the tail  230 P, is affixed to the balloon membrane  226  such that the outer surface  236  of the substrate  234  is exposed and the inner surface  237  of the substrate  234  is affixed to the balloon membrane  226 , with the wiring electrode  238  and wire pair  251 / 253  sandwiched between the substrate  234  and the balloon membrane  226 . The irrigation apertures  235  in the substrate  234  are aligned with the irrigation apertures  227  in the balloon membrane  226 . The exclusion zones  259  in the wiring electrode  238  and the exclusion zones  247  in the contact electrode  233  are concentrically aligned with each other, as well as with the irrigation apertures  227  and  235 . 
     In some embodiments, one or more substrates  234  of the balloon  280  each include at least one capacitive force sensor  136  strategically positioned at predetermined locations between the equator and the distal end of the balloon  280 , for example, generally along one or more latitudes, e.g., L 1 , L 2  and L 3 , of the balloon  280  as shown in  FIG. 8 , for circumferential contact with an ostium or tubular region. For example, a capacitive force sensor  136 , with plates  137  and  138  and a dielectric  139  therebetween, may be positioned generally along a latitude L 1  distal of each contact electrode  233 , as shown in  FIG. 11 . In some embodiments, each capacitive force sensor  136  has its plate  138  affixed to the outer surface  234  of the membrane  226 , situated within a through-hole  228  formed in the respective substrates  234  of the contact electrodes  233 . (In some embodiments, the plate  138  may be affixed to the membrane  226 .) Terminals  117  and  118  for each respective capacitive force sensor  136  are each connected to a respective full via  248 F that includes conductive formation that extends through a through-hole (not shown) in the respective substrates  234  and the membrane  226  to connect to respective lead wires  267  and  268 , respectively, that extend into the interior of the balloon  280  and toward the proximal end of the balloon and through the shaft  270 . It is understood that the lead wires may be included in a ribbon cable that extends through the interior of the balloon  280 . In some embodiments, capacitive force sensor  136  (shown in broken lines in  FIG. 11 ) may be provided within an exclusion zone  247 ′ formed in the contact electrode  233 . 
     In some embodiments, one or more capacitive force sensors  136 A are affixed at predetermined locations X on the membrane  226  along one or more latitudes, with the plates  138  affixed to the membrane  226 , as shown in  FIG. 11 . Terminals  117  and  118  for each respective capacitive force sensor  136  are each passed through a respective through-hole formed in the membrane  226 , sealed by plugs  250 , into the interior of the balloon  280  toward the proximal end of the balloon and through the shaft  270 . In some embodiments, lead wires  267  and  268  may be connected to terminals  117  and  118 , respectively, in the interior of the balloon  280 . 
     It is understood that in some embodiments, the dielectric  139  between the plates  137  and  138  may be air, and that an elastic spring member  148 , e.g., wave spring, may be situated between the plates ( FIG. 12 ) to support the plates at a separation distance D therebetween, where the spring member  148  is elastically compressible to allow the separation distance D to decrease when a contact force is applied to the plates upon tissue contact. 
     It is also understood that in some embodiments, the capacitive force sensor are formed by 3-D printing, including 3-D printing directly onto the catheter distal tip surface on which the sensor is carried on the catheter, and that 3-D printing may be used to form the plates, as well as any mechanical spring for separating and support the plates. 
     In use, the capacitance of the force sensor  136  is measured by the force sensing module  53  (see  FIG. 1 ). The capacitance for the force sensor  136  in the neutral state with the plates  237  and  238  separated by a distance D is measured by the force sensing module  53  as C. As the balloon  280  approaches an ostium, a distal circumferential portion of the balloon comes into contact with the ostium which exerts a force with a normal force component N that compresses the dielectric  239  changing the separation distance from D to D 1 , where D 1 &lt;D, which changes the capacitance of the force sensor  136  from C to C 1 , where C 1 &gt;C. The force sensing module  53  detects the increase capacitance C 1  and, for example, responds by providing an indicia to the medical professional  14 , such as sounding an audio signal or a visual signal. The measured capacitance remains at C 1  so long as the normal force component N remains. Where the normal force component increases (such as where the medical professional further presses the balloon  280  against the ostium), the separation distance decreases further to D 2  where D 2 &lt;D 1 &lt;D and the measured capacitance increases correspondingly to C 2 , where C 2 &gt;C 1 &gt;C. Where the normal force component decreases (such as where the medical professional slightly retracts the balloon from the ostium, the separation distance increases to D 3  where D 1 &lt;D 3 &lt;D, measured capacitance decreases correspondingly to C 3 , where C 1 &gt;C 3 &gt;C. In this manner, the change in the capacitance output of the force sensors  236  detected and measured by the force sensors  236  advantageously indicates the change in force applied to the tip electrode  105  reflective of the change in tissue contact between the balloon and the ostium. Different readings or different changes in readings by the force sensing module of the capacitive force sensors along one or more latitudes of the balloon can indicate the angle of contact, e.g., off-axis tilt angle of the longitudinal axis of the balloon relative to the longitudinal axis of the ostium. For example, where contact is sensed by x numbers of capacitive force sensors along latitude La and contact is sensed by y numbers of capacitive force sensors along latitude Lb, where x≠y, a system processing these signals could provide an indicator of an inference to user that the longitudinal axis of the balloon is not aligned with the longitudinal axis of the ostium. 
     The preceding description has been presented with reference to presently preferred embodiments of the invention. Workers skilled in the art and technology to which this invention pertains will appreciate that alterations and changes in the described structure may be practiced without meaningfully departing from the principal, spirit and scope of this invention. Any feature or structure disclosed in one embodiment may be incorporated in lieu of or in addition to other features of any other embodiments, as needed or appropriate. As understood by one of ordinary skill in the art, the drawings are not necessarily to scale. Accordingly, the foregoing description should not be read as pertaining only to the precise structures described and illustrated in the accompanying drawings, but rather should be read consistent with and as support to the following claims which are to have their fullest and fair scope.