Impedance-based tracking of catheter location in relation to cavity wall

Abstract

To display and / or provide guidance to a physician during mapping.SOLUTION: A method of indicating movement of a receiving electrode of a distal end assembly with respect to a tissue cavity wall includes using the distal end assembly including a plurality of electrodes arranged on the distal end assembly configuration, transmitting an AC signal between one or more reference electrode(s) and a plurality of receiving electrodes attached to a plurality of splines, calculating a plurality of impedance values over time based on a received signal at each of the receiving electrodes, calculating a gradient over time of the impedance values at the receiving electrodes, dynamically rendering on a display a virtual representation of the distal end assembly including virtual representations of the plurality of receiving electrodes, and dynamically adjusting a graphical feature of at least one of the receiving electrodes displayed based on the calculated gradient over time of the impedance. Related apparatus and methods are also described.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] In some embodiments, the present disclosure relates to electroanatomical mapping using a cardiac catheter, and more specifically, to displaying and / or providing guidance to a physician during mapping.

Background Art

[0002] Internal organs can contain tissues and / or body fluids that can vary at different parts of the internal organ and can also vary in different regions of a cavity of the internal organ, such as different chambers of the heart. Thus, the tissue proximity determined based on an electronic signal provided by one or more electrodes may be based on specific tissue characteristics at a given location of an internal organ, such as different regions of the heart.

[0003] U.S. Patent No. 10,952,637 describes a method that includes receiving, from a probe including an electrode and positioned within a cavity in a patient's organ, (i) a proximity signal indicative of the proximity of the electrode to the wall of the cavity and (ii) a position signal indicative of the position of the electrode within the cavity.

[0004] U.S. Patent Application Publication No. 2023 / 0112251 describes a system including a catheter and a processor. The catheter includes a distal end assembly coupled to the distal end of a shaft for insertion into a cavity of a patient's organ, and the distal end assembly includes (i) one or more functional electrodes configured to be disposed in contact with the wall tissue of the cavity and (ii) a reference electrode configured to be disposed within the cavity without contacting the wall tissue. The processor is configured to (i) estimate one or more impedances between one or more of the functional electrodes and the reference electrode and, based on the impedance, determine whether at least some of the functional electrodes are in physical contact with the wall tissue.

Summary of the Invention

Means for Solving the Problems

[0005] Determining and / or indicating a direction towards or away from a tissue wall can assist a physician in guiding a medical device towards, away from, or substantially along a tissue wall surrounding a defined cavity.

[0006] One intent of aspects of the present disclosure is to assist a physician in guiding a catheter and / or catheter tip assembly within a heart chamber without using fluoroscopy.

[0007] A potentially beneficial effect can be to assist a physician in guiding a catheter and / or distal end assembly of a catheter to a target region such as a pulmonary vein.

[0008] Tissue impedance is typically greater than that of blood, and it is expected that greater impedance values will be measured at electrodes closer to the tissue than at electrodes further from the tissue.

[0009] Exemplary solutions include measuring impedance with one or more electrodes within a body cavity and identifying a gradient of impedance over time for each of the one or more electrodes.

[0010] An increase in impedance measured at the electrode, e.g., a positive gradient, indicates that the electrode is moving towards the tissue wall. A decrease in impedance, e.g., a negative gradient measured at the electrode, indicates that the electrode is moving away from the tissue wall. In the case of a basket-type catheter or a balloon-type catheter, when the physician operates the distal end assembly, some of the electrodes may advance towards the tissue wall, while at the same time, other electrodes facing away from the direction of movement move away from the tissue wall. Receiving an indication as to which electrode is approaching the tissue wall may be useful to the physician. Further, receiving an indication as to which electrode is moving away from the tissue may also be useful to the physician. Providing this information in real time may assist the physician, for example, in operating within the cavity and orienting the distal end assembly in a desired direction to reach the target area.

[0011] In some cases, for example, when circumferentially arranged electrodes show a sharp increase in impedance while the electrodes at the distal end of the distal end assembly show a relatively low increase in impedance or no increase in impedance, the entrance to the small hole may be identified.

[0012] In some embodiments, when the electrodes are three-dimensionally (3D) dispersed within the body cavity, data collected from two or more electrodes is used to calculate the 3D gradient of the impedance increasing over time, using the correspondence to the direction towards the surface of the tissue in 3D.

[0013] In some embodiments, a medical device such as the basket-shaped distal end assembly 28 of FIG. 2 is displayed to the physician. While the physician is operating the catheter within the heart cavity, the display shows a virtual representation of the distal end assembly in its current orientation and position. This virtual representation may be shown together with a map of the modeled cavity.

[0014] In some embodiments, the display may optionally display an increasing impedance over time by coloring or otherwise marking (e.g., highlighting) the display of the electrodes corresponding to the impedance gradient over time. The physician can confirm which electrodes are approaching the tissue wall based on their color / brightness / other markings and can accordingly manipulate the distal end.

[0015] In such embodiments, the display may optionally also display the direction in which the gradient is maximum, e.g., the direction in which the distal end assembly is approaching the tissue wall at the fastest rate, as an arrow, for example, pointing towards the tissue surface.

[0016] In some embodiments, the direction or arrow may be displayed away from the tissue surface, or perpendicular to the direction towards the tissue surface, or substantially parallel to the tissue surface.

[0017] Note also that the impedance gradient may be calculated and / or displayed by taking into account the measurement of the position in space using one or more position sensors of the receiving electrodes attached to a medical device such as the distal end assembly 28 of FIG. 2.

[0018] Note also that the impedance gradient may be calculated and / or displayed simultaneously with measuring the position of a medical device such as the basket-shaped electrode assembly 28 of FIG. 2 using one or more position sensors such as a magnetic-based single axis sensor (SAS).

Brief Description of the Drawings

[0019] Here, some embodiments of the present disclosure will be described herein with reference to the accompanying drawings for purposes of illustration only. Referring specifically to the drawings in detail, it is emphasized that the details shown are for purposes of illustration and are intended for an illustrative discussion of the embodiments of the present disclosure. In this regard, the description using the drawings will clarify to those skilled in the art how the embodiments of the present disclosure can be implemented.

[0020] In the drawings, it is as follows.

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5A

Figure 5B

DETAILED DESCRIPTION OF THE INVENTION

[0021] The present disclosure relates, in some of its embodiments, to electroanatomical mapping using a cardiac catheter, and more specifically to displaying and / or providing guidance to a physician during mapping.

[0022] For a better understanding of some embodiments of the present disclosure, reference is first made to the configuration and operation of a catheter-based position tracking system including an expandable end assembly, as illustrated in FIGS. 3, 4, and 5A - 5B of the drawings.

[0023] Referring to FIG. 1, FIG. 1 is a simplified diagram of a catheter-based electrophysiology mapping and ablation system according to an embodiment of the subject matter of the present disclosure, showing an exemplary catheter-based electrophysiology mapping and ablation system 10. The system 10 includes a plurality of catheters that are percutaneously inserted by a physician 24 into a chamber or vascular structure of the heart 12 through the patient's vasculature. Typically, a delivery sheath catheter is inserted into the left atrium or right atrium near the desired location of the heart 12. Thereafter, one or more catheters may be inserted into the delivery sheath catheter to reach the desired location within the heart 12. The plurality of catheters may include catheters dedicated to sensing intracardiac electrogram (IEGM) signals, ablation-only catheters, and / or catheters dedicated to both sensing and ablation. An exemplary catheter 14 configured to sense IEGM is illustrated herein. The physician 24 may place the distal tip 28 of the catheter 14 in contact with the heart wall to sense a target site in the heart 12. For ablation, the physician 24 may similarly place the distal end of the ablation catheter in contact with the target site for ablation of tissue.

[0024] Catheter 14 is an exemplary catheter that optionally distributes over a plurality of splines 62 at the distal tip 28 and includes one, preferably a plurality of electrodes 66 configured to sense IEGM signals. Catheter 14 may additionally include a position sensor (not shown) embedded within or near the distal tip 28 to track the position and orientation of the distal tip 28. Optionally and preferably, the position sensor is a magnetic-based position sensor that includes three magnetic coils for detecting three-dimensional (3D) position and orientation.

[0025] A magnetic-based position sensor may operate in conjunction with a position pad 25 that includes a plurality of magnetic coils 32 configured to generate a magnetic field within a predefined working volume. The real-time position of the distal tip 28 of the catheter 14 may be tracked based on the magnetic field generated by the position pad 25 and sensed by the magnetic-based position sensor. Details of magnetic-based position sensing techniques are described in U.S. Patent Nos. 5,539,199; 5,443,489; 5,558,091; 6,172,499; 6,239,724; 6,332,089; 6,484,118; 6,618,612; 6,690,963; 6,788,967; and 6,892,091.

[0026] The system 10 may include one or more electrode patches 38 positioned to contact the skin on the patient 23 to establish position referencing of the position pad 25 and impedance-based tracking of the electrodes 66. For impedance-based tracking, a current is directed to the electrodes 66 and sensed at the electrode-skin patches 38, whereby the position of each electrode can be triangulated via the electrode patches 38. Details of impedance-based position tracking techniques are described in U.S. Patent Nos. 7,536,218; 7,756,576; 7,848,787; 7,869,865; and 8,456,182.

[0027] The recorder 11 may record and display an electrogram 21 captured by the body surface ECG electrodes 18 and an intracardiac electrogram (IEGM) captured by the electrodes 66 of the catheter 14. The recorder 11 may include pacing capabilities for pacing the rhythm of the heart and / or may be electrically connected to an independent pacer.

[0028] System 10 may include an ablation energy generator 50 adapted to deliver ablation energy to one or more of the electrodes at the distal tip of a catheter configured to ablate. The energy generated by ablation energy generator 50 may include radiofrequency (RF) energy, pulsed-field ablation (PFA) energy, or a combination thereof, including unipolar or bipolar high-voltage DC pulses such that the energy can be used to effect irreversible electroporation (IRE), but is not limited thereto.

[0029] Patient Interface Unit (PIU) 30 is an interface configured to establish electrical communication between the catheter, other electrophysiological devices, a power source, and a workstation 55 for controlling the operation of system 10. The electrophysiological devices of system 10 may include, for example, multiple catheters, position pads 25, body surface ECG electrodes 18, electrode patches 38, ablation energy generator 50, and recorder 11. Optionally and preferably, PIU 30 additionally includes processing capabilities for implementing real-time calculation of the position of the catheter and performing ECG calculations.

[0030] Workstation 55 includes a memory, a processor unit having a memory or storage device in which appropriate operating software is stored, and user interface functions. Workstation 55 may optionally provide a plurality of functions including: (1) Rendering a 3D graphical representation of a model or anatomical map 20 to model endocardial anatomical structures in three dimensions (3D) and display them on display device 27; (2) Display, on the display device 27, a representative visual mark or image in which the activation sequence (or other data) compiled from the recorded potential map 21 is superimposed on the rendered anatomical map 20. (3) Render a 3D graphical representation of the model for 3D modeling of the catheter inserted into the body and displaying it on the display device 27. (4) Display the real-time positions and orientations of a plurality of catheters within the heart chamber. (5) Display on the display device 27 a target site such as the position where ablation energy is applied.

[0031] One commercial product embodying each element of the system 10 is available as the CARTO (trademark) 3 system, commercially available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0032] Various methods for measuring impedance Note that the technique for impedance-based tracking of catheter position with respect to tissue can function for various methods of measuring the impedance between electrodes.

[0033] In some embodiments, the impedance measurement can also be performed between one or more reference electrodes (if any) on the catheter and some electrodes within the body cavity of the patient.

[0034] In some embodiments, the reference electrode(s) is / are disposed within or on the end assembly so as to prevent the reference electrode(s) from touching the tissue.

[0035] In some embodiments, impedance measurements can also be performed between one or more reference electrodes that transmit an AC signal (e.g., an AC signal with a frequency in the kilohertz range such as 6.4 kHz) on an end assembly of a catheter within a body cavity of a patient and some receiving electrodes within the body cavity of the patient.

[0036] In some embodiments, measuring impedance can be performed between one or more electrodes on a patch on a patient's body and some electrodes within a body cavity of the patient.

[0037] In some embodiments, measuring impedance can be performed between one or more electrodes that transmit an AC electrical signal on an expandable end assembly of a catheter within a patient body cavity and some receiving electrodes on an outer surface or spline of the expandable end assembly. In some embodiments, the transmitting electrode(s) are positioned on the catheter so as to avoid contact with the cavity wall.

[0038] In some embodiments, measuring impedance can be performed between one or more adjacent electrodes on a distal end assembly.

[0039] Calculation of changes in impedance over time Note that techniques for impedance-based tracking of catheter position relative to tissue can be performed on the heart while the heart is beating. The heart wall is moving while the electrodes measure impedance values to calculate changes in impedance over time.

[0040] In some cases, impedance is measured at the same time point relative to the cardiac cycle, such that movement of the distal end assembly can be measured relative to the same position on the heart wall.

[0041] In some cases, the impedance is measured at different times relative to the cardiac cycle, and the change in impedance resulting from the movement of the catheter tip assembly is calculated. For example, the change in the maximum value of the impedance over the cardiac cycle may indicate movement towards or away from the heart wall. In another embodiment, the change in the minimum value of the impedance over the cardiac cycle may indicate movement towards or away from the heart wall. In another embodiment, the change in the average value of the impedance over the cardiac cycle may indicate movement towards or away from the heart wall.

[0042] Calculation of the direction with respect to the tissue It should be noted that tissue impedance is typically greater than blood impedance, and it is expected that larger impedance values will be measured at electrodes closer to the tissue than at electrodes immersed in the blood away from the tissue wall.

[0043] In some embodiments, an indication of the proximity to the tissue, which is normalized, is normalized based on the patient-specific minimum and maximum impedance values of the patient.

[0044] In some embodiments, the gradient is calculated based on several impedance values.

[0045] The direction in which the value determined by the gradient increases is considered to be the direction towards the tissue wall. The direction in which the value determined by the gradient decreases is considered to be the direction away from the tissue wall. The direction perpendicular to the direction of the gradient is considered to be substantially parallel to the tissue wall.

[0046] Display In some embodiments, after the direction with respect to the tissue, i.e., the direction towards the tissue, the direction away from the tissue, and the direction parallel to the tissue wall, is calculated, the direction is optionally displayed by a display.

[0047] In some embodiments, the direction may optionally be displayed in the rendered display of the 3D working volume, along with a virtual representation of the distal end assembly indicating its real-time position and orientation.

[0048] In some embodiments, the coloring of the distal device or the electrodes on the distal device may be used to indicate whether the movement is towards the tissue wall, away from the tissue wall, or there is no change in impedance (potentially equivalent to movement parallel to the tissue wall). Optionally, the brightness, shading, or hue of the color displayed may be changed based on the magnitude and direction of the gradient.

[0049] In some embodiments, additional graphical features may also indicate how close each electrode is to the tissue. As a non-limiting example, the electrode closest to the tissue may be outlined in one color, and the electrode farthest from the tissue may be outlined in another color.

[0050] In some embodiments, the intensity of the coloring of the distal device, or the intensity of the coloring of the electrodes on the distal device, may be used to indicate relative proximity.

[0051] In some embodiments, an arrow corresponding to the direction of the tissue wall is displayed.

[0052] Referring now to FIG. 2, FIG. 2 is a more detailed isometric view of the expandable end assembly on the distal tip of the catheter of FIG. 1.

[0053] The expandable end assembly 28 includes a coupler 26 connected to the shaft at the distal end of the catheter 14 and a pusher 58 including a distal portion 60. The pusher 58 is configured to advance and retract through the catheter 14, for example, using a manipulator or handle (not shown). The expandable end assembly 28 may include a plurality of splines 64. Each spline 64 may include a plurality of electrodes 66 disposed thereon (only some are labeled for simplicity). Optionally, the expandable end assembly 28 may include a nose connector 70 connected to the distal portion 60 of the pusher 58.

[0054] In some embodiments, the reference electrode 59 may be attached to the pusher 59, adjacent to the coupler 26, or adjacent to the nose connector 70, as shown in FIG. 2. In some embodiments, two or more reference electrodes 59 may be used, for example, one adjacent to the coupler 26 and one adjacent to the nose connector 70. The reference electrode(s) 59 are optionally used to provide an AC signal for measuring the impedance between the electrode 66 and the reference electrode(s) 59.

[0055] FIG. 2 is intended to show that the electrodes 66 on the spline 64 are disposed in a three-dimensional (3D) distribution in space.

[0056] In some embodiments, the electrodes 66 disposed along the spline 64 may be disposed in a two-dimensional (2D) distribution in space, i.e., in a plane.

[0057] FIG. 2 shows a portion of the expandable end assembly 28 in physical contact with the cavity wall tissue 80.

[0058] In some embodiments, the catheter and / or the expandable end assembly 28 may include one or more position sensors (not shown) embedded at the distal end of the shaft 26, such as a position sensor (e.g., a multi-axis sensor), a position sensor disposed within the distal receptacle of the nose connector 70, and / or a position sensor (e.g., a single-axis sensor) disposed on one or more splines 54.

[0059] Before detailing at least one embodiment of the present disclosure, it is to be understood that the present disclosure is not necessarily limited to the details of the construction and arrangement of the components and / or methods described in the following description, and / or illustrated in the drawings and / or examples, in its application. The present disclosure is capable of other embodiments or of being practiced or carried out in various ways.

[0060] Referring now to FIG. 3, FIG. 3 is a simplified qualitative diagram showing the impedance measured by an electrode in a body cavity as a function of the distance from the body cavity wall tissue, according to one aspect of the present disclosure.

[0061] FIG. 3 shows a graph having an X-axis 302 of qualitative proximity values to the cavity wall tissue and a Y-axis 304 of qualitative impedance values. The graph of FIG. 3 includes a line 306 showing the qualitative value of the impedance value of the electrode in the body cavity as a function of the proximity to the body cavity wall, and a continuation of line 306 to the region where the electrode contacts the body cavity wall at various pressures of different magnitudes.

[0062] The graph of FIG. 3 shows the expected impedance behavior in the body cavity as a function of proximity. Note that as the distance to the cavity wall decreases, the proximity to the cavity wall increases.

[0063] The graph of FIG. 3 shows the expected shape of the relationship between impedance and proximity.

[0064] In some embodiments, the in-vivo measurement may determine the impedance values at the endpoints and the minimum and maximum values. Such minimum and maximum values may optionally be determined for each patient by accumulating data in real time and determining the minimum and maximum values of the real-time data.

[0065] It should be noted that the minimum impedance value and the maximum impedance value of each electrode are, among other things, functions of the distance of the electrode to the reference electrode.

[0066] In some examples, the minimum impedance value and the maximum impedance value for each electrode are adjusted to determine the minimum impedance value and the maximum impedance value normalized for all electrodes.

[0067] In some examples, the data points for constructing line 306 are optionally measured in vivo by an electrode that moves within the body cavity where the impedance is measured. All or at least some of the measured values are used to generate line 306.

[0068] In some examples, only the maximum impedance value and the minimum impedance value are optionally discovered by in-vivo measurement, optionally for each patient.

[0069] In some examples, the data points for constructing line 306 are optionally measured in vivo by several electrodes that move within the body cavity where the impedance is measured and optionally by a position measurement system that measures the position of the electrodes.

[0070] In some examples, the data points for constructing line 306 are optionally obtained from a database containing data measured at a certain time in the past for a particular patient.

[0071] In some embodiments, the data points for constructing line 306 are optionally obtained from a database that includes data measured at some past time for an optionally averaged group of patients.

[0072] FIG. 3 also shows two specific levels of impedance along the Y-axis 304.

[0073] The first specific impedance level 308 represents an impedance where the distance to the cavity wall is close to 0, as if the electrode is just beginning to touch the cavity wall. The left line 306 of the contact impedance is within the "non-contact" impedance zone 312. In some embodiments, the value of the first specific impedance level 308 is determined as a specific percentage below the maximum value of line 306.

[0074] The second specific impedance level 310 represents the impedance of an electrode that touches and presses against the cavity wall at a level of force that is considered sufficient to perform ablation using the electrode, if desired. A corresponding "contact" zone 314 is shown, where the cavity wall is being pushed somewhat away from the contact point due to a greater force being applied to the cavity wall to create a sufficiently good contact. Beyond the "contact" zone 318, the impedance flattens out and reaches its maximum value, which is shown by the "saturation" zone 316 and a high impedance above the level referred to by reference numeral 310.

[0075] Referring now to FIG. 4, this is a simplified flowchart diagram of a method of illustrating the movement of the receiving electrode of the distal end assembly relative to the tissue cavity wall, according to one aspect of the present disclosure.

[0076] The method of FIG. 4 includes the following: Using the distal end assembly comprising a plurality of electrodes arranged in a three-dimensional (3D) configuration on the distal end assembly (402), wherein in some embodiments, the position of the distal end assembly is tracked within the 3D working volume, using the distal end assembly comprising a plurality of electrodes arranged in a three-dimensional (3D) configuration on the distal end assembly (402). Tracking may include tracking a position sensor(s) in one or more of the connector, pusher, nose connector, reference electrode, spline, and receiving electrode of the distal end assembly. Tracking potentially enables rendering a graphical representation of the distal end assembly on a display in real time based on the tracking. Rendering optionally includes displaying the electrodes attached to the distal end assembly and Transmitting an alternating current (AC) signal (404) between one or more reference electrode(s) and a plurality of receiving electrodes attached to a plurality of splines, Calculating a plurality of impedance values over time (406) based on the signals received at each of the receiving electrodes. In some embodiments, the impedance values are such that the distances from the reference electrode(s) to different receiving electrodes are different, Calculating the gradient over time of the impedance value at each of the receiving electrodes (408), Dynamically rendering a virtual representation of the distal end assembly within a three-dimensional working volume on a display, the virtual representation including a virtual representation of each of the plurality of receiving electrodes on the distal end assembly, dynamically rendering a virtual representation of the distal end assembly within a three-dimensional working volume on a display (410), and Based on the calculated gradient of the impedance over time, dynamically adjusting at least one graphical feature of the plurality of receiving electrodes being displayed (412), may be normalized.

[0077] In some embodiments, dynamically adjusting includes rendering the receiving electrodes differently based on different values of the gradient over time of the impedance measured at the receiving electrodes.

[0078] Different renderings or graphical features corresponding to different values of the gradient can be implemented by different graphical features such as color-coding, and / or shading, and / or blinking, and / or highlighting of the display of the electrode(s).

[0079] In some cases, only two different types of graphical features are used to render the received electrodes, which are the first graphical feature when the value of the gradient over time exceeds a first, positive threshold, and a different second graphical feature when the value of the impedance gradient over time is less than a second, negative threshold.

[0080] The first, positive threshold can function to distinguish electrodes having a larger impedance gradient value, which indicates that the electrode is closer to and moving towards the tissue cavity wall, and to display the closer electrode differently from further electrodes having a smaller value of impedance gradient.

[0081] The second, negative threshold can serve to distinguish between electrodes having a negative impedance gradient value, which indicates that the electrode is moving away from the tissue cavity wall.

[0082] In some cases, only three different types of graphical features are used to mark the received electrodes, which are the first graphical feature when the value of the gradient over time exceeds a first, positive threshold, a different second graphical feature when the value of the gradient over time is less than a second, negative threshold, and a third graphical feature when the value of the gradient over time is between the negative and positive thresholds.

[0083] In some embodiments, calculating a plurality of impedance values may include normalizing the impedance values, and calculating a spatial gradient includes using the normalized impedance values.

[0084] In some embodiments, normalizing may include normalizing the impedance at each of the receiving electrodes using the previously measured maximum value and the previously measured minimum value of the impedance.

[0085] The method of FIG. 4 provides visual indications for guiding a physician on how to manipulate a catheter along the tissue wall of a heart chamber to map the heart chamber and / or for indicating to the physician how to manipulate the catheter to reach a target location.

[0086] Referring now to FIGS. 5A and 5B, these figures are diagrams of the distal end assembly of the catheter of FIG. 2 displayed on a display, which displays directions based on a spatial gradient superimposed on a display of an expandable catheter according to one aspect of the present disclosure.

[0087] FIGS. 5A - 5C show all components of the expandable basket-shaped distal end assembly 28 of FIG. 2 as displayed on a display 500, and when these components are indicated by reference numerals, they are referenced by the same reference numerals as in FIG. 2.

[0088] FIG. 5A shows an arrow 502 in the direction of movement of the distal end assembly 28. Arrow 502 points towards the tissue wall 80.

[0089] The electrode, referred to as 66a, is moving towards the tissue wall 80 and is measuring an increase in impedance, e.g., a positive gradient over time that exceeds a certain positive threshold. Electrode 66a faces the tissue wall, moves towards the tissue, and is marked by a graphical feature, e.g., a first specific color indicating an increase in impedance, or a first specific luminance, or some other indication marking.

[0090] In some embodiments, the physician may be manipulating the catheter within the cavity before or at the start of anatomical mapping and thus may not be aware of the tissue wall depiction. The displayed indication provided on electrode 66a may assist the physician in maneuvering the distal end assembly 28 towards the region of interest and / or along the tissue wall.

[0091] FIG. 5B shows an arrow 504 in the direction of movement of the distal end assembly 28. Arrow 504 points in a direction away from the cavity wall tissue 80.

[0092] The electrode, referred to as 66a, is moving away from the cavity wall tissue 80 and is measuring a decrease in impedance, e.g., a negative gradient over time that is more negative or smaller than a certain negative threshold. The electrode is displayed as being in the direction away from the tissue and moving away from the tissue, e.g., by some particular color indicating a decrease in impedance, or by a particular luminance, or by some other indication marking.

[0093] SUMMARY OF THE DISCLOSURE

EXAMPLE

[0094] A method of indicating movement of a receiving electrode of a distal end assembly relative to a tissue cavity wall, the method comprising: using the distal end assembly including a plurality of electrodes disposed on the distal end assembly in a three-dimensional (3D) configuration; transmitting an alternating current (AC) signal between one or more reference electrodes and a plurality of receiving electrodes attached to a plurality of splines; calculating a plurality of impedance values over time based on the signals received at each of the receiving electrodes; calculating a gradient over time of the impedance value at each of the receiving electrodes; Dynamically rendering a virtual representation of the distal end assembly within a three-dimensional working volume on a display, the virtual representation including virtual representations of each of the plurality of receiving electrodes on the distal end assembly, and dynamically rendering the virtual representation of the distal end assembly within the three-dimensional working volume on the display. Dynamically adjusting at least one graphical feature of the plurality of receiving electrodes, the at least one graphical feature being displayed based on the calculated temporal gradient of the impedance. A method comprising:

Example

[0095] The method according to Example 1, wherein a first graphical feature is defined for a calculated positive gradient that exceeds a defined positive threshold, and a second graphical feature is defined for a calculated negative gradient that is below a defined negative threshold.

Example

[0096] 3. The method according to any one of Examples 1 to 2, wherein a third graphical feature is defined for a calculated gradient between the negative threshold and the positive threshold.

Example

[0097] The method according to any one of Examples 1 to 3, wherein calculating the plurality of impedance values at each of the receiving electrodes includes normalizing the impedance values at each of the receiving electrodes, and calculating the temporal gradient of the impedance includes using the normalized impedance values.

Example

[0098] The method according to Example 4, wherein normalizing includes normalizing the impedance at each of the receiving electrodes using a previously measured maximum value and a previously measured minimum value of the impedance.

Example

[0099] The method according to any one of Examples 1 to 5, wherein the one or more reference electrodes (plural possible) include reference electrodes disposed on the stem of the basket catheter.

Example

[0100] The method according to any one of Examples 1 to 6, wherein at least one of the plurality of receiving electrodes attached to the plurality of splines includes an ablation electrode.

Example

[0101] The method according to any one of Examples 1 to 7, wherein the spatial position of the spline is measured by a position sensor.

Example

[0102] The method according to any one of Examples 1 to 8, wherein the spatial position of the receiving electrode is measured by a position sensor.

[0103] Those skilled in the art to which the present disclosure pertains will understand that, although the present disclosure has been described with respect to preferred embodiments, the concepts on which the present disclosure is based can be readily utilized as a basis for designing other structures, systems, and processes for carrying out several purposes of the present disclosure.

[0104] Furthermore, it should be understood that the expressions and terms used in this specification are for the purpose of explanation and should not be regarded as limiting. It should be noted that the terms "comprising", "including", and "having" used throughout the appended claims should be construed to mean "including but not limited to". The indefinite articles "a" and "an" used in this specification and the claims should be understood to mean "at least one" unless clearly indicated to the contrary. The phrase "and / or" used in this specification and the claims should be understood to mean "either or both" of the elements so combined, i.e., elements that may exist conjunctively in some cases and disjunctively in other cases. The term "each" need not be construed exclusively as referring to each and every one, and may in some cases refer to "at least some" when technically relevant.

[0105] All patents and patent applications referred to in this specification are hereby incorporated by reference in their entirety as if each individual patent or patent application was specifically and individually indicated to be incorporated herein by reference. It should be noted that any citation or identification of a reference document in this application should not be construed as an admission that such document is available as prior art to the present disclosure.

[0106] Therefore, it is important to note that the scope of the present disclosure should not be construed as being limited by the exemplary embodiments described herein. Other variations are possible within the scope of the present disclosure as defined in the appended claims. Other combinations and sub - combinations of features, functions, elements, and / or characteristics may be claimed by amending the claims or presenting new claims in this application or related applications. Such amendments or new claims are considered to be within the subject matter of the invention described herein, regardless of whether they are directed to different combinations or the same combination, and regardless of whether they are different from, broader than, narrower than, or the same as the scope of the original claims.

[0107] 〔Embodiments〕 (1) A method of indicating movement of a receiving electrode of a distal end assembly relative to a tissue cavity wall, the method comprising: using a distal end assembly that includes a plurality of electrodes disposed on the distal end assembly in a three - dimensional (3D) configuration; transmitting an alternating current (AC) signal between one or more reference electrodes and a plurality of receiving electrodes attached to a plurality of splines; calculating a plurality of impedance values over time based on the signals received at each of the receiving electrodes; calculating the gradient over time of the impedance value at each of the receiving electrodes; dynamically rendering a virtual representation of the distal end assembly within a three - dimensional working volume on a display, the virtual representation including a virtual representation of each of the plurality of receiving electrodes on the distal end assembly; dynamically adjusting a graphical feature of at least one of the plurality of receiving electrodes, the graphical feature being displayed based on the calculated gradient over time of the impedance. (2) The method according to embodiment 1, wherein the first graphical feature is defined for a calculated positive gradient that exceeds a defined positive threshold, and the second graphical feature is defined for a calculated negative gradient that is below a defined negative threshold. (3) The method according to any one of embodiments 1 to 2, wherein a third graphical feature is defined for a calculated gradient between the negative threshold and the positive threshold. (4) The calculating of the plurality of impedance values at each of the receiving electrodes includes normalizing the impedance values at each of the receiving electrodes, and the calculating of the gradient of the impedance over time includes using the normalized impedance values. The method according to any one of embodiments 1 to 3. (5) The method according to embodiment 4, wherein the normalizing includes normalizing the impedance at each of the receiving electrodes using a previously measured maximum value and a previously measured minimum value of the impedance.

[0108] (6) The method according to any one of embodiments 1 to 5, wherein the one or more reference electrodes include reference electrodes disposed on a stem of a basket catheter. (7) The method according to any one of embodiments 1 to 6, wherein at least one of the plurality of receiving electrodes attached to the plurality of splines includes an ablation electrode. (8) The method according to any one of embodiments 1 to 7, wherein the spatial position of the spline is measured by a position sensor. (9) The method according to any one of embodiments 1 to 8, wherein the spatial position of the receiving electrode is measured by a position sensor.

Claims

**Claim 1** A method for indicating movement of a receiving electrode of a distal end assembly relative to a tissue cavity wall, the method comprising: using a distal end assembly that includes a plurality of electrodes disposed on the distal end assembly in a three-dimensional (3D) configuration; transmitting an alternating current (AC) signal between one or more reference electrodes and a plurality of receiving electrodes attached to a plurality of splines; calculating a plurality of impedance values over time based on the signals received at each of the receiving electrodes; calculating a gradient over time of the impedance value at each of the receiving electrodes; dynamically rendering a virtual representation of the distal end assembly within a three-dimensional working volume on a display, the virtual representation including a virtual representation of each of the plurality of receiving electrodes on the distal end assembly; and dynamically adjusting at least one graphical feature of at least one of the plurality of receiving electrodes based on the calculated gradient over time of the impedance, the at least one graphical feature being displayed based on the calculated gradient over time of the impedance. **Claim 2** The method of claim 1, wherein a first graphical feature is defined for a calculated positive gradient that exceeds a defined positive threshold, and a second graphical feature is defined for a calculated negative gradient that is less than a defined negative threshold. **Claim 3** The method according to any one of claims 1 to 2, wherein a third graphical feature is defined for a calculated gradient between the negative threshold and the positive threshold. **Claim 4** The method according to any one of claims 1 to 3, wherein calculating the plurality of impedance values at each of the receiving electrodes includes normalizing the impedance value at each of the receiving electrodes, and calculating the gradient over time of the impedance includes using the normalized impedance values. **Claim 5** The method of claim 4, wherein normalizing includes normalizing the impedance at each of the receiving electrodes using a previously measured maximum value and a previously measured minimum value of the impedance at each of the receiving electrodes. **Claim 6** The method according to any one of claims 1 to 5, wherein the one or more reference electrodes include reference electrodes disposed on a stem of a basket catheter. **Claim 7** The method according to any one of claims 1 to 6, wherein at least one of the plurality of receiving electrodes attached to the plurality of splines includes an ablation electrode.

8. The method according to any one of claims 1 to 7, wherein the spatial position of the spline is measured by a position sensor.

9. The method according to any one of claims 1 to 8, wherein the spatial position of the receiving electrode is measured by a position sensor.

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