Patent Application
20230200897
The subject matter disclosed herein relates to electrophysiologic catheters, particularly those capable of ablating cardiac tissue via electrodes disposed on a balloon surface.
Ablation of cardiac tissue has been used to treat cardiac arrhythmias. Ablative energies are typically provided to cardiac tissue by a tip portion, which can deliver ablative energy alongside the tissue to be ablated. Some of these catheters administer ablative energy from various electrodes disposed on or incorporated into three-dimensional structures, e.g., wire baskets and balloons.
A catheter balloon may be incorporated onto a distal end of a catheter shaft. The catheter balloon may comprise a membrane upon which are disposed flexible circuit strips. The flexible circuit strips may each comprise a substrate including an outer surface and an inner surface, with the inner surface disposed on the membrane. Contact electrodes may be disposed on the outer surfaces of the substrates. A cover may be disposed over a peripheral portion of each contact electrode and an adjacent portion of the corresponding substrate so that the peripheral portion of the contact electrode is not exposed.
The cover is intended to increase robustness of the contact electrode in response to fatigue that might arise from repeated expansion and contraction of the catheter balloon. The cover may comprise an inner edge and an outer edge, while the contact electrode may comprise a boundary disposed between the inner edge and outer edge, such that the cover extends over the boundary. The boundary may be disposed midway between the inner edge and the outer edge. Further, the substrate and the cover may be comprised of a same material, such as polyimide, which may be bonded to the substrate.
The contact electrode may have a fishbone configuration that includes a plurality of protrusions extending away from a main body. As such, the cover may extend from a first protrusion to a second protrusion, or there may be a gap in the cover between the first protrusion and the second protrusion.
While the specification concludes with claims, which particularly point out and distinctly claim the subject matter described herein, it is believed the subject matter will be better understood from the following description of certain examples taken in conjunction with the accompanying drawings, in which like reference numerals identify the same elements and in which:
The following detailed description should be read with reference to the drawings, in which like elements in different drawings are similarly numbered. 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. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, variations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention.
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%. In addition, 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.
Ablation of cardiac tissue to correct a malfunctioning heart is a well-known procedure. Typically, to successfully ablate, cardiac electropotentials need to be measured at various locations of the myocardium. In addition, temperature measurements during ablation provide data enabling the efficacy of the ablation to be measured. Typically, for an ablation procedure, the electropotentials and the temperatures are measured before, during, and after the actual ablation.
An ablation catheter may include a lumen, and a balloon may be deployed through the catheter lumen. A multi-layer flexible metal structure is attached to an exterior wall or membrane of the balloon. The structure comprises a plurality of electrode groups arranged circumferentially about the longitudinal axis, where each electrode group comprises multiple ablation electrodes, typically arranged longitudinally.
Each electrode group may also include at least one micro-electrode that is insulated physically and electrically from the ablation electrodes in its group. Each electrode group may also include at least a thermocouple. In some embodiments, each electrode group includes a micro-electrode and a thermocouple formed at a common location. Using a single catheter, with the three functionalities of ability to perform ablation, electropotential measurement, and temperature measurement, simplifies cardiac ablation procedures.
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 diagnostic/therapeutic catheter 24 (e.g., a balloon catheter), reflected in
As shown in
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 may be displayed on a three-dimensional representation 60 of the heart of the patient 18 on a screen 62. However, it may be displayed two-dimensionally, e.g., by fluoroscopy or MRI.
To operate apparatus 12, the processor 46 communicates with a memory 50, which has many 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 functions of which are described below. The memory 50 typically comprises other modules, such as a force module for measuring the force on the distal end 22, a tracking module for operating the tracking method used by the processor 46, and an irrigation module allowing the processor to control irrigation provided for the distal end 22. For simplicity, such other modules are not illustrated in
With further reference to
The shaft 70 and the distal shaft end 88 define a longitudinal axis 78 of the balloon 80. The balloon 80 is deployed, in a collapsed configuration, via the lumen 23 of the probe 20. A proximal end of membrane 26 of balloon 80 is attached to first or proximal shaft portion 82P and a distal end of membrane 26 of balloon 80 is attached to second or distal shaft portion 82D, proximate to distal shaft end 88. Balloon 80 may be expanded to an expanded configuration after exiting from the distal end 22 by moving distal shaft end 88 proximally to shorten the distance between the distal end 89 of balloon 80 and proximal end 87 of balloon 80, and thus increase the width of balloon 80, i.e., by telescoping distal shaft portion 82D proximally in the proximal shaft portion 82P. Passing irrigation fluid into balloon 80 may further expand balloon 80. Balloon 80 may be returned to its collapsed configuration by ceasing the irrigation and then moving distal shaft end 88 away from proximal end 87 to decrease the width of and extend the length of balloon 80, i.e., by telescoping distal shaft portion 82D distally in proximal shaft portion 82P. This telescopic motion between the first shaft portion and the second shaft portion may be controlled by knob 85 of control handle 83, shown in
The membrane 26 supports and carries a combined electrode and temperature sensing member which is constructed as a multi-layer flexible circuit electrode assembly 84. The “flex circuit electrode assembly” 84 may have many different geometric configurations. In the illustrated embodiment, the flex circuit electrode assembly 84 has a plurality of radiating flexible-circuit strips 30. The strips 30 are evenly distributed about outer membrane surface 26o of balloon 80. Each comprises a substrate 34 that has wider proximal portion that gradually tapers to a narrower distal portion. As seen in
Each substrate 34 has a proximal tail 31P proximal to the wider proximal portion and a distal tail 31D distal of the narrower distal portion. As described below, distal tail portion 31D may extend up to distal shaft end 88 to be secured thereunder. Substrate 34 may be bonded to membrane 26 with an adhesive, such as an epoxy. Some adhesive may be disposed between inner surface 37 of substrate 34 and membrane 26.
The flex circuit electrode assembly 84 is described with respect to one of its strips 30 as shown in
The substrate 34 is formed with one or more irrigation pores or apertures 35 that are in alignment with the irrigation apertures 27 of the balloon member 26 so that fluid passing through the irrigation apertures 27 and 35 can pass to the ablation site on the ostium. Substrate 34 may be cut to shape by, and the irrigation pores 35 formed by, any suitable manufacturing technique, such as laser cutting.
The substrate 34 has a first or outer surface 36 facing away from the balloon membrane 26, and a second or inner surface 37 facing the balloon membrane 26. On its outer surface 36, the substrate 34 supports and carries the contact electrodes 33 that may be exposable to an environment, such as an interior of a portion of a heart, and particularly adapted for tissue contact with a pulmonary vein ostium. On its inner surface 37, the substrate 34 supports and carries a wiring electrode 38. The contact electrode 33 delivers RF energy to the ostium during ablation or is connected to a thermocouple junction for temperature sensing of the ostium. In the illustrated embodiment, the contact electrode 33 has a longitudinally elongated portion 40 and a plurality of thin transversal linear portions or protrusions 41 extending generally perpendicularly from each lateral side of the elongated portion 40 between enlarged proximal and distal ends 42P and 42D, generally evenly spaced therebetween. The elongated portion 40 has a greater width and each of the protrusions has a generally uniform lesser width. Accordingly, the configuration or trace of the contact electrode 33 may resemble a “fishbone” with protrusions 41 being “fish bones” of varying lengths extending from a main body of the electrode, but it should be noted that the invention is not limited to such configuration. In contrast to an area or “patch” ablation electrode, the protrusions 41 of the contact electrode 33 advantageously increase the circumferential or equatorial contact surface of the contact electrode 33 with the ostium while void regions 43 between adjacent protrusions 41 advantageously allow the balloon 80 to collapse inwardly or expand radially as needed at locations along its equator. In the illustrated embodiment, the protrusions 41 have different lengths, some being longer, others being shorter. For example, the plurality of protrusions includes a distal protrusion, a proximal protrusion and protrusions therebetween, where each of the protrusions in between has a shorter adjacent protrusion. For example, each protrusion has a length different from its distal or proximal immediately adjacent neighboring protrusion(s) such that the length of each protrusion generally follows the tapered configuration of each substrate 34. In the illustrated embodiment, there are 22 protrusions extending across (past each lateral side of) the elongated portion 40, with the longest protrusion being the third protrusion from the enlarged proximal end 42P. In some embodiments, contact electrode 33 includes an outer or contact layer 76 and an inner or seed layer 77 between contact layer and substrate 34. Contact layer 76 may comprise gold. Seed layer 77 may comprise titanium, tungsten, palladium, silver, or combinations thereof. Seed layer 77 may be sputtered onto substrate 34 and contact layer 76 may be sputtered, plated, or a combination thereof, onto the seed layer. The thickness of seed layer 77 may be between about 250 angstroms to about 350 angstroms, e.g., about 300 angstroms. The thickness of contact layer 76 may be between about 0.75 micrometers to about 1.25 micrometers, e.g., about 1 micrometer. Whatever material seed layer 77 comprises, e.g., titanium, it should be readily bondable to the material of substrate 34, e.g., polyimide.
Formed within the contact electrode 33 are one or more exclusion zones 47, each surrounding an irrigation aperture 35 formed in the substrate 34. The exclusion zones 47 are voids purposefully formed in the contact electrode 33 so as to avoid damage to the contact electrode 33 during construction of the electrode assembly 84 in accommodating the irrigation apertures 35 at their locations and in their function.
Also formed in the contact electrode 33 are one or more conductive blind vias 48 which are conductive or metallic formations that extend through through-holes in the substrate 34 and are configured as electrical conduits connecting the contact electrode 33 on the outer surface 36 and the wiring electrode 38 on the inner surface 37. It is understood that “conductive” is used herein interchangeably with “metallic” in all relevant instances. For example, the via may be fabricated by plating gold through the through-holes in substrate 34. Preferably, the thickness blind via 48 is less than or approximates the thickness of substrate 34. For example, the thickness of blind via 48 may be between about 4 micrometers and about 25 micrometers, e.g., about 10 micrometers to about 14 micrometers.
In the illustrated embodiment, the contact electrode 33 measures longitudinally between about 0.1 inch and 1.0 inch, and preferably between about 0.5 inch and 0.7 inch, and more preferably about 0.57 inch, and has four exclusion zones 47 and nine blind vias 48.
On the inner surface 37 of the substrate 34, the wiring electrode 38 is generally configured as an elongated body generally similar in shape and size to the elongated portion 40 of the contact electrode 33. The wiring electrode 38 loosely resembles a “spine” and also functions as a spine in terms of providing a predetermined degree of longitudinal rigidity to each substrate 34 of the electrode assembly 84. The wiring electrode 38 is positioned such that each of the blind vias 48 is in conductive contact with both the contact electrode 33 and the wiring electrode 38. In the illustrated embodiment, the two electrodes 33 and 38 are in longitudinal alignment with other, with all nine blind vias 48 in conductive contact with both electrodes 33 and 38. In some embodiments, the wiring electrode 38 has an inner portion of copper and a peripheral portion of gold.
The wiring electrode 38 is also formed with its exclusion zones 59 around the irrigation apertures 35 in the substrate 34. The wiring electrode 38 is further formed with solder pad portions, at least one active 61A, and there may be one or more inactive solder pad portions 61B. The solder pad portions 61A and 61B are extensions from a lateral side of the elongated body of the wiring electrode 38. In the illustrated embodiment, an active solder pad portion 61A is formed at about a mid-location along the elongated body, and a respective inactive solder pad portion 61B is provided at each of the enlarged distal end 42D and the enlarged proximal end 42P.
Attached, e.g., by a solder weld 63, to the active solder pad portion 61A are the wire pair, e.g., a constantan wire 51 and a copper wire 53. The copper wire 53 provides a lead wire to the wiring electrode 33, and the copper wire 53 and the constantan wire 51 provide a thermocouple whose junction is at solder weld 63. The wire pair 51/53 are passed through a through-hole 29 formed in the membrane 26. It is understood that, in other embodiments in the absence of the through-hole 29, the wire pair 51/53 may run between the membrane 26 and the substrate 34 and further proximally between the membrane 26 and the proximal tail 31P until the wire pair 51/53 enters the tubular shaft 70 via another through-hole (not shown) formed in the tubular shaft sidewall closer to the proximal ring 28P.
The substrates 34 are affixed to the balloon membrane 26 such that the outer surface 36 of the substrate 34 is exposed and the inner surface 37 of the substrate 34 is affixed to the balloon membrane 26, with the wiring electrode 38 and wire pair 51/53 sandwiched between the substrate 34 and the balloon membrane 26. The irrigation apertures 35 in the substrate 34 are aligned with the irrigation apertures 27 in the balloon membrane 26. The exclusion zones 59 in the wiring electrode 38 and the exclusion zones 47 in the contact electrode 33 are concentrically aligned with each other, as well as with the irrigation apertures 27 and 35 in balloon 26 and substrate 34, respectively.
Further details on constructing a diagnostic/therapeutic catheter in accordance with the foregoing disclosure may be found in U.S. patent application Ser. No. 15/360,966, published as U.S. Patent Application Publication No. 2017/0312022. The entire content of this application is incorporated by reference herein in its entirety.
Through ongoing research and product development efforts concerning the subject matter described above, Applicant has determined that balloon 80 must be able to withstand multiple cycles of being deployed from lumen 23 of probe 20 in a collapsed configuration, expanded to an expanded configuration, returned to the collapsed configuration, and withdrawn into lumen 23 of probe 20. The number of cycles may be from about five to about twenty. Thus, the overall integrity of the assembled balloon must withstand at least five to twenty fatigue cycles.
During these efforts, Applicant has identified an opportunity for ensuring the robustness of contact electrode 33 without comprising its function or compromising the integrity of balloon 80 during its multiple cycles of deployment. Specifically, as balloon 80 is repeatedly deployed and retracted, a very rare possibility arises that contact layer 76 may begin to be scraped or delaminated from seed layer 77. When such delamination occurs, contact layer 76 may crack or flake away from seed layer 77 at boundary 90 of contact electrode 33, primarily along protrusions 41. Although Applicant has determined that such delamination may be avoided by ensuring that boundary 90 has smooth edges, Applicant has also determined another technique for avoiding such delamination. This technique is described with reference to
Inner edge 92 of cover 91 should be positioned atop contact electrode 33 at a sufficient distance away from boundary 90 to ensure that cover 91 minimizes any likelihood of delamination without interfering with the ability of the contact electrode to properly ablate tissue. Thus, for example, a covering width, i.e., a width between boundary 90 and inner edge 92, may be between about 0.005 inchers and about 0.02 inches, e.g., about 0.013 inches.
While the location of outer edge 92 on substrate 34 need not be defined based on ablation functionality, providing more of cover 91 atop substrate 34 than is necessary to ensure a robust attachment of cover 91 to substrate 34 may inhibit other important characteristics of balloon 80, such as its conformance characteristics. For example, the overall width of cover 91 may be between about 0.01 inches to about 0.04 inches, e.g., about 0.025 inches. However, the width of cover 91 need not necessarily be precisely defined, nor include gap 93, as indicated in the preceding paragraph. Instead, referring to the detail view of
Cover 91 may comprise the same material as the substrate, e.g., polyimide. Polyimide is a preferred material for preventing delamination of a gold contact layer 76 because polyimide bonds readily to itself and to gold. Cover 91 may be applied by any suitable process, such as sputtering, lamination, or vapor deposition. A first mask may be provided over the entirety of contact layer 76 except for the portion of contact layer 76 between inner edge 92 and boundary 90. A second mask may be provided over portions of substrate 34 to define a location of outer edge 94. Thus, upon application of cover 91, boundary 90 is disposed under cover 91, between inner edge 92 and outer edge 94, e.g. midway between inner edge 92 and outer edge 94 as reflected in
Any of the examples or embodiments described herein may include various other features in addition to or in lieu of those described above. The teachings, expressions, embodiments, examples, etc., described herein should not be viewed in isolation relative to each other. Various suitable ways in which the teachings herein may be combined should be clear to those skilled in the art in view of the teachings herein.
Having shown and described exemplary embodiments of the subject matter contained herein, further adaptations of the methods and systems described herein may be accomplished by appropriate modifications without departing from the scope of the claims. In addition, where methods and steps described above indicate certain events occurring in certain order, it is intended that certain steps do not have to be performed in the order described but in any order as long as the steps allow the embodiments to function for their intended purposes. Therefore, to the extent there are variations of the invention, which are within the spirit of the disclosure or equivalent to the inventions found in the claims, it is the intent that this patent will cover those variations as well. Some such modifications should be apparent to those skilled in the art. For instance, the examples, embodiments, geometrics, materials, dimensions, ratios, steps, and the like discussed above are illustrative. Accordingly, the claims should not be limited to the specific details of structure and operation set forth in the written description and drawings.
The present application claims priority under 35 U.S.C. § 119 to U.S. Provisional Patent Application No. 63/293,114, filed Dec. 23, 2021. The entire content of this application is incorporated by reference herein in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 63293114 | Dec 2021 | US |
