Balloon catheter having a split electrode

Abstract

To provide a medical apparatus.SOLUTION: A medical apparatus includes a probe, which includes an insertion tube configured for insertion into a body cavity. A balloon is connected distally to the insertion tube and is inflated within the body with fluid that flows into the balloon through the insertion tube. Electrodes are disposed at different respective locations on a surface of the balloon and configured to contact a tissue within the body cavity, each electrode being divided into multiple segments, including at least two segments having different respective areas. An electrical signal generator applies radio-frequency (RF) signals simultaneously in parallel to the multiple segments of each electrode with an amplitude sufficient to ablate the tissue contacted by the electrode. Sensing circuitry acquires electrophysiological signals from at least one of the multiple segments of each electrode separately from and independently of the other segments of the electrode.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention generally relates to medical devices, and more particularly to devices and methods for ablation and sensing of biological tissue.

Background Art

[0002] Radiofrequency ablation (RFA) is a medical procedure that uses heat generated from radiofrequency (RF) alternating current (e.g., in the frequency range of 350 - 500 kHz) to ablate a part of the electrical conduction pathway of the heart or other dysfunctional tissue. Ablation is performed by inserting a probe, such as a catheter, into the tissue and applying an RF current to the electrode at the tip of the probe. The probe may also be used to acquire electrophysiological signals for diagnostic purposes.

[0003] U.S. Patent Application Publication No. 2015 / 0119877 describes a method, system, and apparatus for providing treatment to tissue within a body cavity. The system may include a support shaft, an expansion member coupled to the distal portion of the support shaft, and an ablation structure wound around the expansion member that is configured to engage the body cavity in various sizes and is smaller than the circumference of the expansion member.

[0004] U.S. Patent Application Publication No. 2012 / 0029500 describes a catheter that includes a flexible shaft having a length sufficient to access a patient's renal artery. A treatment element at the distal end of the shaft is sized for deployment within the renal artery. The treatment element includes a radially expandable structure configured to maintain its position within the renal artery.

[0005] U.S. Patent No. 10,653,480 describes a method of constructing an electrophysiological catheter having a flexible circuit electrode assembly. The method includes providing a flexible circuit having a substrate, a first conductive layer, and a second conductive layer.

Summary of the Invention

Means for Solving the Problems

[0006] The embodiments of the present invention described below provide improved probes for ablation and sensing, as well as methods for their manufacture and operation.

[0007] Accordingly, embodiments of the present invention provide a medical device including a probe. The probe includes an insertion tube configured for insertion into a patient's body cavity, a balloon configured to be distally connected to the insertion tube and to inflate within the body cavity with a fluid flowing through the insertion tube and into the balloon, and a plurality of electrodes disposed at respective different positions on the surface of the balloon and configured to contact tissue within the body cavity. Each electrode is divided into a plurality of segments including at least two segments having respective different areas. The medical device also includes an electrical signal generator configured to apply radio frequency (RF) signals in parallel and simultaneously to the plurality of segments of each electrode at an amplitude sufficient to ablate the tissue contacted by the electrode. A sensing circuit is configured to acquire electrophysiological signals from at least one of the plurality of segments of each electrode separately and independently from the other segments of the electrode.

[0008] In the disclosed embodiments, the at least two segments include a first segment and a second segment having respective first and second areas, and the first area is at least twice the second area.

[0009] In a further embodiment, the first area is at least four times the second area.

[0010] In yet a further embodiment, the balloon includes one or more perfusion apertures that pass through the first segment but not the second segment, and fluid flows out of the balloon through the perfusion apertures to perfuse at least the tissue contacted by the first segment.

[0011] In the disclosed embodiments, each electrode is segmented by at least one longitudinal isolation line. Additionally or alternatively, each electrode is segmented by at least one transverse isolation line.

[0012] Furthermore, according to one embodiment of the present invention, a method for medical treatment and diagnosis is also provided. The method includes providing a probe for insertion into a patient's body cavity, the probe including an insertion tube, a balloon distally connected to the insertion tube, and a plurality of electrodes disposed at different respective positions on the surface of the balloon, each electrode being segmented into a plurality of segments including at least two segments having different respective areas. The method further includes inflating the balloon in the body cavity with a fluid flowing through the insertion tube into the balloon such that one or more of the electrodes on the surface of the inflated balloon contact tissue in the body cavity. A radio frequency (RF) signal is applied in parallel and simultaneously to a plurality of segments of one or more of the electrodes at an amplitude sufficient to ablate the tissue in contact with the electrodes. An electrophysiological signal is acquired separately and independently from at least one of each of the plurality of segments of one or more of the electrodes from the other segments of the electrodes.

[0013] The present invention will be more fully understood by considering the following "Detailed Description of the Invention" in conjunction with the drawings.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Detailed Description of the Invention

[0015] In radiofrequency ablation (RFA) procedures, an alternating current typically having a frequency of 350 - 500 kHz is driven through the tissue of interest. The current is carried into the tissue via electrodes of a catheter placed in contact with the tissue. These electrodes may also be used for diagnostic purposes by acquiring electrophysiological signals from the tissue they are in contact with.

[0016] Some RFA procedures use a balloon catheter having a balloon located at the distal end and electrodes arrayed on the surface of the balloon. The balloon is inflated within the body cavity and the electrodes are brought into contact with the tissue to be ablated. To avoid damage to the electrodes and the tissue due to excessive current density, the electrodes on the balloon are typically large, for example about 5 mm 2 in size.

[0017] To ablate tissue within the body, for example in the left atrium of the heart, a small-diameter balloon can be used. For example, a small-diameter balloon having a diameter of less than 15 mm can be used. Despite the small size of the balloon itself, the electrodes are large enough to be able to transmit the RFA current without being damaged. In this case, the size of these electrodes prevents them from being effectively used for diagnosis, which is because each electrode acquires signals from a relatively large area of the tissue and at any given time this area typically generates multiple signals. The balloon can have separate electrodes for signal acquisition, but this solution can be impractical due to the small size of the balloon.

[0018] Embodiments of the invention described herein address this problem by providing a probe having a balloon with segmented electrodes. An electrical signal generator applies RF signals in parallel and simultaneously to a plurality of segments of each electrode at an amplitude sufficient to ablate tissue contacted by the electrodes. On the other hand, a sensing circuit can acquire electrophysiological signals from at least one of the segments of each electrode separately and independently from other segments. Thus, the electrodes have an effective area sufficient to safely deliver RFA current while allowing signals to be acquired with precise spatial resolution.

[0019] In the disclosed embodiments, the probe comprises an insertion tube for insertion into a patient's body cavity and a balloon connected to the distal end of the insertion tube and inflatable with fluid flowing through the insertion tube into the balloon. The surface of the balloon has a plurality of electrodes for contacting tissue within the body cavity, and each electrode is divided into segments of unequal area.

[0020] The electrical signal generator applies high-frequency (RF) signals in parallel and simultaneously to the segments of each electrode at an amplitude sufficient to ablate tissue contacted by the electrodes. For RFA, by connecting the segments, particularly the larger segments, in parallel, a sufficiently large surface area is ensured to avoid damage to the electrodes by the RF current.

[0021] The sensing circuit acquires separate and independent electrophysiological signals from separate segments of each electrode. In particular, by acquiring signals from the smaller segments, each segment can reliably acquire its signal from a small local area of tissue.

[0022] In a further embodiment, the irrigation opening passes through the larger segments utilized for RFA, such that fluid can flow out of the balloon through the irrigation opening to irrigate the tissue contacted by the larger segments. However, the smaller segments are mainly utilized for signal acquisition and may not have an irrigation opening to deliver only a small amount of ablation current.

[0023] System Description 1 is a schematic, pictorial illustration of a medical device 20 during an RFA procedure in accordance with one embodiment of the present invention. A physician 22 performs an RFA procedure on a subject 24 using an ablation catheter 26 (further details of the catheter are described below). The physician 22 further utilizes the ablation catheter 26 to acquire electrophysiological signals from tissue of the subject 24, either simultaneously or alternately with the emission of RF current. The embodiment shown in the current and subsequent figures refers to an example of an RFA procedure on a heart chamber 27. In alternative embodiments, the RFA procedure and electrophysiological signal acquisition can be performed on other organs and tissues, as well as the heart 27, as will be apparent to those skilled in the art upon reviewing this specification.

[0024] As shown in inset 36, ablation catheter 26 comprises a shaft 28 and a distal assembly 30, with the shaft serving as an insertion tube for inserting the distal assembly into a heart chamber 27. Distal assembly 30 comprises a balloon 32 having a plurality of ablation electrodes 34, which are divided into segments having unequal areas, as shown in FIG. 2. A portion of distal assembly 30 and shaft 28 is also shown in inset 38.

[0025] The medical device 20 further comprises a processor 42, sensing circuitry 43, and an electrical signal generator 44, which typically reside within a console 46. The processor, sensing circuitry, and signal generator may each comprise one or more circuit components. The catheter 26 is connected to the console 46 via an electrical interface 48, such as a port or socket. RF signals are conveyed from the signal generator 44 to the distal assembly 30, and electrophysiological signals are conveyed from the distal assembly to the sensing circuitry 43 via electrical wires (not shown) that extend through the interface 48 and the catheter 26.

[0026] Processor 42 receives setup parameters for the treatment from physician 22 (or other operator) before and / or during the ablation treatment. For example, using one or more suitable input devices such as a keyboard, mouse, or touch screen (not shown), physician 22 defines the electrical and temporal parameters of the RFA signal applied to some or all of the segments of electrode 34. Processor 42 passes appropriate control signals to signal generator 44 to perform RFA. Processor 42 also instructs sensing circuit 43 to acquire electrophysiological signals from specific segments of electrode 34, as described in more detail in FIG. 2.

[0027] Processor 42 can be further configured to track the respective positions of electrode 34 during the RFA treatment and during electrophysiological signal acquisition using any suitable tracking technique. For example, distal assembly 30 can include one or more electromagnetic position sensors (not shown), which output signals that vary depending on the position of the sensor in the presence of an external magnetic field generated by one or more magnetic field generators 50. Based on these signals, processor 42 can confirm the position of electrode 34. Magnetic field generator 50 is connected to console 46 via cable 52 and interface 54. Alternatively, for each electrode 34, processor 42 can confirm the respective impedance between the electrode and a plurality of external electrodes 56 on the body surface of various different location targets 24, and then calculate the ratio between these impedances, which indicates the location of the electrode. As yet another alternative, the processor can use both electromagnetic tracking and impedance-based tracking, as described, for example, in U.S. Patent No. 8,456,182, the disclosure of which is incorporated herein by reference.

[0028] In some embodiments, processor 42 displays a relevant image 60 of the target anatomy on display screen 58, for example, annotated to indicate the current position and orientation of distal assembly 30. Alternatively or additionally, processor 42 may display a map of electrophysiological signals acquired through electrodes 34 on screen 58.

[0029] Processor 42, sensing circuitry 43, and electrical signal generator 44 may typically include both analog and digital elements. Thus, sensing circuitry 43 may include multiple inputs with respective analog-to-digital converters (ADCs) for receiving analog electrophysiological signals from catheter 26 and converting them to digital form for passing to processor 42. Electrical signal generator 44 typically includes RF analog circuitry for generating RF signals for ablation, as well as a digital-to-analog converter (DAC) for receiving digital control signals from processor 42.

[0030] Alternatively, if the processor 42 is configured to send and / or receive analog signals, the electrophysiological and / or control signals may be passed between the processor 42, the sensing circuitry 43, and the electrical signal generator 44, respectively, in analog form.

[0031] Additionally, the processor 42 typically includes a digital filter for extracting signals at given frequencies from the received electrophysiological signals.

[0032] Typically, the functionality of the processor 42 described herein is implemented, at least in part, in software. For example, the processor 42 may include a programmed digital computing device including at least a central processing unit and a random access memory (RAM). Program code, including software programs, and / or data are loaded into the RAM for execution and processing by the CPU. The program code and / or data can be downloaded to the processor in electronic form, for example, via a network. Alternatively or additionally, the program code and / or data can be provided and / or stored on a non-transitory tangible medium such as magnetic, optical, or electronic memory. When such program code and / or data are provided to the processor, they result in a machine or a dedicated computer configured to perform the tasks described herein.

[0033] At the start of the RFA procedure, the physician 22 inserts the catheter 26, with the balloon 32 in a deflated configuration, through the sheath 62 into the heart 27 via the vasculature of the subject 24. Only after the catheter has exited, the sheath is inflated with fluid flowing into the balloon through the shaft 28 to the balloon in its intended functional shape. This functional shape is shown in the insertion views 36 and 38. By accommodating the deflated balloon 32, the sheath 62 also serves to minimize trauma to the blood vessels as the balloon is brought to the target location. The physician 22 maneuvers the catheter 26 to the target location within the heart 27 of the subject 24 by using the manipulator 64 near the proximal end of the catheter and / or deflection from the sheath 62. The physician 22 contacts the distal assembly 30 to tissue such as the myocardial tissue of the heart 27. Next, under the control of the physician 22 and the processor 42, the electrical signal generator 44 generates an RFA signal, which is carried through the catheter 26 parallel to the segments of the electrodes 34.

[0034] In monopolar RFA, the current of the ablation signal flows between the ablation electrode 34 and an external electrode or "return patch" 66, and the return patch is externally coupled between the subject 24, typically the skin of the subject's torso, and the generator 44. In bipolar RF ablation, the current of the signal flows between pairs of the ablation electrodes 34.

[0035] The processor 42 acquires electrophysiological signals received separately and independently by selected segments of the electrode 34 from the tissue of the subject 24, either simultaneously with or alternating with the RFA. The electrophysiological signals are conveyed from the electrode 34 to the processor 42 through the catheter 26.

[0036] Despite the particular type of ablation procedure illustrated in FIG. 1, the principles of the present invention can be applied to any suitable type of multi-channel ablation procedure.

[0037] FIG. 2 is a schematic view of the distal end of the catheter 26 according to an embodiment of the present invention.

[0038] As described above, the catheter 26 includes a shaft 28 (having only the portion shown herein) and a distal assembly 30. The distal assembly 30 includes a balloon 32 and electrodes 34 at different respective positions on the surface of the balloon. The balloon 32 has a polar axis 106 that coincides with the longitudinal axis 104 of the distal end 102 of the shaft 28. A plurality of flexible circuit boards 105 are disposed on an expandable member about the longitudinal axis 104. Each board 105 is provided with an electrode 34. As shown, there are a plurality of electrode members (designated individually as 34) for each board 105. Each of the electrodes 34 is divided into segments 114 along longitudinal isolation lines 108 and transverse isolation lines 110 (where "longitudinal" and "transverse" are defined with reference to the polar axis 106). For example, the electrode 34a (one of the electrodes 34), shown in more detail in the inset figure 112, is divided into six segments 114a, 114b, 114c, 114d, 114e, and 114f. Four of the segments 114a - 114d have the same (or approximately the same) area, while the segments 114e and 114f are smaller than the segments 114a - 114d and each has an area that is, for example, about one - quarter (1 / 4) of the area of each of the segments 114a - 114d. Each segment 114 (i.e., 114a, 114b, 114c, or 114d) is individually connected to other conductors, such as respective wires or electrical traces (not shown) that pass through the shaft 28 and lead to the console 46. Thus, as described above, the sensing circuit 43 and the electrical signal generator 44 are enabled to address the segments individually or in parallel for sensing and ablation purposes. That is, each of the larger electrode segments 116a, 116b, 116c, 116d and the smaller electrode segments 116e and 116f are electrically insulated from each other on the expandable member.

[0039] The electrode 34a includes perfusion openings 116a, 116b, 116c, and 116d each passing through respective segments 114a, 114b, 114c, and 114d, providing a path for fluid to flow out of the balloon 32 and perfuse the tissue contacted by each segment and the tissue near it. However, the two smaller segments 114e and 114f typically do not have perfusion openings and may be perfused, for example, by the openings 116c and 116d. In alternative embodiments, the smaller segments may also have perfusion openings as well.

[0040] In other embodiments, the number of segments of each electrode 34 may be six or more. Additionally or alternatively, the ratio between the areas of the larger and smaller segments may differ from 4:1 (the number "4" indicating that the larger segment is about four times the size of the smaller segment), but is typically at least 2:1, and the number of perfusion openings may differ for the larger segments. Further, FIG. 2 shows the electrode 34 segmented along the longitudinal and transverse lines 108 and 110, but this segmentation may be performed by the longitudinal lines only, or by the transverse lines only. The dividing lines may also have different geometric shapes, such as an angle other than 90 degrees with respect to the transverse line 110.

[0041] For the purpose of ablation using the electrode 34a, the processor 42 instructs the signal generator 44 to apply an RF signal at an amplitude sufficient to ablate the tissue contacted by the electrode. The RF signal is applied in parallel and simultaneously to all or some of the segments 114a - 114f, providing a conductive area large enough for the RF current to pass through without damaging the electrode 34a.

[0042] For the purpose of acquiring electrophysiological signals using the electrode 34a, the processor 42 connects the sensing circuit 43 to one or more of the segments 114a to 114f, for example, the smaller segments 114e to 114f. Thus, the conductive area over which the electrophysiological signals are acquired is small enough to prevent the signals from being averaged over a large area of the tissue. The electrophysiological signals may be acquired in this way from multiple segments and multiple different electrodes simultaneously.

[0043] It should be understood that the above embodiments are given by way of example, and the present invention is not limited to what is specifically illustrated and described above in this specification. Rather, the scope of the present invention includes both various combinations and sub - combinations of the various features described above in this specification, as well as its variations and modifications not disclosed in the prior art that would occur to those skilled in the art upon reading the foregoing description.

[0044] 〔Embodiment〕 (1) A medical device, A probe, An insertion tube configured for insertion into a body cavity of a patient, A balloon, which is distally connected to the insertion tube and is configured to inflate within the body cavity with a fluid flowing through the insertion tube into the balloon, and A plurality of electrodes disposed at different respective positions on the surface of the balloon and configured to contact tissue within the body cavity, each electrode being divided into a plurality of segments including at least two segments having different respective areas, An electrical signal generator configured to apply high - frequency (RF) signals in parallel and simultaneously to the plurality of segments of each electrode at an amplitude sufficient to ablate the tissue contacted by the electrode, A sensing circuit configured to acquire electrophysiological signals separately and independently from at least one of the plurality of segments of each electrode from the other segments of the electrode. A medical device comprising. (2) The apparatus according to Embodiment 1, wherein the at least two segments include a first segment and a second segment each having a respective first area and a second area, and the first area is at least twice the second area. (3) The apparatus according to Embodiment 2, wherein the first area is at least four times the second area. (4) The apparatus according to Embodiment 2, wherein the balloon comprises one or more irrigation apertures that pass through the first segment but not the second segment, and the fluid flows out of the balloon through the irrigation apertures to irrigate the tissue in contact with at least the first segment. (5) The apparatus according to Embodiment 1, wherein each electrode is divided into the segments by at least one longitudinal isolation line.

[0045] (6) The apparatus according to Embodiment 1, wherein each electrode is divided into the segments by at least one latitudinal isolation line. (7) A method for medical treatment and diagnosis, comprising: providing a probe for insertion into a patient's body cavity, the probe comprising: an insertion tube, a balloon distally connected to the insertion tube, and a plurality of electrodes disposed at respective different positions on the surface of the balloon, each electrode being divided into a plurality of segments including at least two segments each having a different respective area; inflating the balloon in the body cavity with a fluid flowing into the balloon through the insertion tube such that one or more of the electrodes on the surface of the inflated balloon contact the tissue in the body cavity; applying radio frequency (RF) signals in parallel and simultaneously to the one or more of the plurality of segments of the electrodes at an amplitude sufficient to ablate the tissue in contact with the electrodes; obtaining an electrophysiological signal from at least one of the plurality of segments of each of the one or more of the electrodes, separately and independently from other segments of the electrode. A method comprising this. (8) The method according to embodiment 7, wherein the at least two segments include a first segment and a second segment having respective first and second areas, and the first area is at least twice the second area. (9) The method according to embodiment 8, wherein the first area is at least four times the second area. (10) providing one or more perfusion openings in the probe that pass through the first segment but not through the second segment; and perfusing the tissue in contact with the first segment with fluid flowing out of the balloon through the perfusion openings. The method according to embodiment 8, comprising this.

[0046] (11) The method according to embodiment 7, wherein each electrode is divided into the segments by at least one longitudinal isolation line. (12) The method according to embodiment 7, wherein each electrode is divided into the segments by at least one transverse isolation line. (13) A medical device, A probe, an insertion tube configured for insertion into a body cavity of a patient; an expandable member having a longitudinal axis, distally connected to the insertion tube and configured to expand about the longitudinal axis within an organ. A probe comprising an expandable member. A plurality of electrodes radially arranged about the longitudinal axis, each electrode of the plurality of electrodes being disposed on a respective flexible circuit board, each electrode being divided into a plurality of segments, the plurality of segments including at least two larger electrode segments having substantially equal surface areas, and two smaller electrode segments each having approximately one-quarter of the surface area of each of the two larger electrode segments, the larger electrode segments and the smaller electrode segments being insulated from each other to define separate electrodes; and a medical device comprising the plurality of electrodes. (14) The medical device according to embodiment 13, wherein the at least two larger electrode segments include four larger electrode segments. (15) The medical device according to embodiment 14, wherein the four larger electrode segments and the two smaller electrode segments are disposed on a single flexible electrode substrate.

Claims

**Claim 1** A medical device, A probe, An insertion tube configured for insertion into a patient's body cavity, A balloon, which is distally connected to the insertion tube and is configured to inflate within the body cavity with a fluid flowing through the insertion tube into the balloon, and A plurality of electrodes disposed at different respective positions on the surface of the balloon and configured to contact tissue within the body cavity, each electrode being divided into a plurality of segments including at least two segments having different respective areas, An electrical signal generator configured to apply radio frequency (RF) signals in parallel and simultaneously to the plurality of segments of each electrode at an amplitude sufficient to ablate the tissue contacted by the electrode, A sensing circuit configured to acquire an electrophysiological signal separately and independently from at least one of the plurality of segments of each electrode from the other segments of the electrode, The at least two segments include a first segment and a second segment having a first area and a second area respectively, the first area being at least twice the second area, and the second segment being disposed more distally than the first segment, The electrode includes one or more perfusion openings that pass through the first segment but not through the second segment, and the fluid flows out of the balloon through the perfusion openings to perfuse at least the tissue in contact with the first segment, the device. **Claim 2** The device according to claim 1, wherein the first area is at least four times the second area. **Claim 3** The device according to claim 1, wherein each electrode is divided into the segments by at least one longitudinal isolation line. **Claim 4** The device according to claim 1, wherein each electrode is divided into the segments by at least one transverse isolation line.

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