Tissue proximity indicator threshold for cardiac ablation

Abstract

In one exemplary mode, an apparatus includes: a catheter including an electrode providing an intracardiac electrogram (IEGM) signal and a signal for sensing impedance; an ablation energy generator configured to conduct ablation energy to the electrodes of the catheter based on a user input; a controller configured to: sample the IEGM signal from the electrode before and after a given ablation, and sense an impedance between the electrode and tissue; and a processor configured to: compare the sensed impedance to a TPI threshold to determine a contact state of the electrode relative to the tissue, present an indication of the determined contact state to a display, calculate a change in the IEGM signal due to a given ablation, and determine a change in the IEGM signal due to the given ablation. And adjusting a TPI threshold for subsequent ablation based on the calculated change in the IEGM signal due to a given ablation of the tissue with the electrode.

Description

Technical Field

[0001] This disclosure relates to ablation using a therapeutic intracardiac catheter, and particularly, but not limited to, indicative of tissue proximity during cardiac ablation. Background Technology

[0002] A wide range of medical procedures involve placing probes, such as catheters, inside a patient's body. One medical procedure in which these types of probes or catheters have proven to be very useful is the treatment of cardiac arrhythmias. Cardiac arrhythmias, especially atrial fibrillation, have been a common and dangerous medical condition, particularly among the elderly.

[0003] The diagnosis and treatment of cardiac arrhythmias involve mapping the electrical properties of cardiac tissue, particularly the endocardium and cardiac volume, and selectively ablating cardiac tissue by applying energy. In such procedures, catheters are inserted into and optionally around the heart chambers. In most procedures, multiple catheters are inserted into the patient. Catheters may include mapping catheters, ablation catheters, temperature-sensing catheters, and image-sensing catheters. Some catheters are specifically designed for placement in particular anatomical structures, such as the coronary sinus, esophagus, atria, and ventricles. Catheters have multiple electrical channels; some catheters have more channels than others, depending on the number of sensors and electrodes included in each catheter. The number and type of catheters depend on the procedure and the physician's preferred workflow.

[0004] A typical ablation procedure involves inserting a catheter with one or more electrodes at its distal end into the ventricle. RF (radio frequency) current (or pulsed electric field ablation (PFA) energy) is applied through the tip electrode of the ablation catheter, and the current flows through the medium surrounding the tip electrode—the blood and tissue between the tip electrode and the unrelated electrodes. The current distribution depends on the amount of contact between the electrode surface and the tissue compared to blood, which has a higher conductivity. Due to the tissue's resistance, heating occurs. The tissue is sufficiently heated to destroy the cells in the cardiac tissue, resulting in the formation of a non-conductive lesion within the cardiac tissue.

[0005] Therefore, when placing an ablation catheter or other catheters in the body (especially near the endocardial tissue), it is desirable for the catheter ablation electrode to be in direct contact with the tissue. Electrode-tissue contact can be measured based on the impedance between the electrode at the distal end of the catheter and the return electrode. Attached Figure Description

[0006] This disclosure will be understood in conjunction with the following detailed description and the accompanying drawings, in which: Figure 1 This is a simplified illustration of a catheter-based electrophysiological mapping and ablation system constructed and operated according to examples of this disclosure; Figure 2 It is used for Figure 1A more detailed isometric view of the expandable distal end assembly of the system's catheter; Figure 3 It is shown that it is used for Figure 1 A simplified qualitative example of the impedance measured by electrodes in the body cavity as a function of the proximity of the electrodes to the cavity wall tissue in the system; and Figure 4A and Figure 4B It includes those used for Figure 1 The flowchart shows the steps involved in adjusting the threshold of the organizational proximity index in the system. Detailed Implementation

[0007] Overview As previously mentioned, the contact between the electrode and tissue can be measured based on the impedance between the electrode and tissue. The quality of contact between the electrode and tissue can be represented as a tissue proximity index (TPI). For example, a patient-specific TPI threshold can be used to determine whether the electrode has made sufficient contact with the tissue to provide successful ablation. From a physician's perspective, it is generally important to consider whether the cardiac signal at the ablation site is sufficiently attenuated by ablation for adequate electrode-tissue contact. If the cardiac signal at the tissue is sufficiently attenuated by ablation, then the electrode will subsequently make sufficient contact with the tissue during ablation.

[0008] The TPI threshold can be selected and defines whether a given impedance value indicates sufficient contact to attenuate cardiac signals. For example, if the sensed impedance is greater than the TPI threshold, the sensed impedance indicates that the electrode is in sufficient contact with the tissue to successfully ablate it, while if the sensed impedance is not greater than the TPI threshold, the sensed impedance indicates that the electrode is not in sufficient contact with the tissue. Therefore, it is important to carefully select the TPI threshold so that it indicates the contact quality required to achieve successful ablation (e.g., the desired lesion).

[0009] In practice, the TPI threshold required to achieve the desired lesion is often patient-dependent and also location-dependent. Therefore, having a universal TPI threshold does not provide a good indicator of the “contact” between the electrode and the tissue. For example, a physician might use one TPI threshold to ablate around a pulmonary vein (PV) and another to ablate the roof of the atrium. As another example, a physician might use one TPI threshold to ablate the upper left PV (LSPV) and another to ablate the lower right PV (RIPV). Furthermore, physicians may use significantly different TPI thresholds for different patients.

[0010] Examples of this disclosure address at least some of the challenges described above by providing a system in which a TPI threshold is dynamically adjusted for each patient (and optionally) for each cardiac location. For example, a TPI threshold may be dynamically adjusted for patient X for PV, and another TPI threshold may be dynamically adjusted for patient X for RIPV.

[0011] Initially, a TPI threshold can be estimated. The disclosed example describes a method for estimating an initial TPI threshold based on minimum and maximum impedance. The system samples an intracardiac electrogram (IEGM) sensed by the electrodes and also performs impedance measurements to measure the impedance between the electrodes and the tissue. IEGM can be sensed between an electrode and another catheter electrode or one or more surface electrodes. The system measures the impedance and compares it to a TPI threshold to determine the contact status of the electrodes. For example, if the impedance is greater than the TPI threshold, the contact status is considered adequate, and if the measured impedance is less than the TPI threshold, the contact status is considered inadequate. The contact status can be displayed on a screen for physician review.

[0012] The physician decides to perform ablation at the current electrode location based on one or more factors. The system samples the IEGG, performs ablation, and samples the IEGG again after ablation to determine the magnitude or other measurement of the reduction in IEGG due to ablation. The reduction in IEGG can be defined as the decrease in the magnitude of the peak-to-peak voltage after ablation compared to before ablation. The TPI threshold adjustment is defined as a function of the magnitude of the reduction in IEGG, or alternatively as a function of the percentage reduction in voltage due to ablation. If the reduction in IEGG is greater than a given reduction, the TPI threshold is decreased based on the reduction in IEGG. If the reduction in IEGG is less than or equal to a given reduction, the TPI threshold is increased. The new TPI threshold can be calculated using the following formula: New TPI threshold = Old TPI threshold - (ΔV - B)A, Here, ΔV is the reduction in the voltage amplitude of the IEGM due to ablation, and A and B are threshold adjustment factors. A and B are chosen to achieve a gradual change in the TPI threshold towards the target TPI threshold, thereby achieving the desired lesion through ablation. For example, if the expected ΔV is approximately 4 mV, then B could be approximately 0.3 or 0.4, and A could be, for example, approximately 5. However, any suitable value for A and B can be selected by the user, for example. The above steps can be repeated at different ablation sites, allowing the TPI threshold to be adjusted after each successful ablation.

[0013] The TPI threshold can be electrode-specific, such that the electrode-specific TPI threshold is dynamically adjusted based on data collected relative to a given electrode. In some examples, the TPI threshold can be common to all electrodes (or a subset of electrodes), such that the common TPI threshold is dynamically adjusted based on data collected relative to any given electrode (of the catheter or subset of electrodes).

[0014] In some examples, physicians can choose to reset the TPI threshold to its original value (before any adjustment) at any time. Optionally, the system can reset the TPI threshold if the distance between two subsequent ablation sites is greater than a predefined distance. The predefined distance can be defined by the user (e.g., a physician) or the system. In this way, the system does not need to require excessive contact force for any reason.

[0015] System Description refer to Figure 1 This is a simplified illustration of an example catheter-based electrophysiological mapping and ablation system based on the currently disclosed subject matter, showing an example catheter-based electrophysiological mapping and ablation system 10. See also... Figure 2 , it is Figure 1 A more detailed isometric view of the expandable distal end assembly 28 of the conduit 14.

[0016] System 10 includes multiple catheters that are inserted by physician 24 through the skin into the chambers or vascular structures of heart 12 within the patient's vascular system (as seen in illustration 45). Typically, a delivery sheath catheter is inserted into the left or right atrium near the desired location within heart 12. One or more catheters can then be inserted into the delivery sheath catheter to reach the desired location within heart 12. The multiple catheters may include catheters specifically for sensing intracardiac electrogram (IEGM) signals, catheters specifically for ablation, and / or catheters specifically for both sensing and ablation. An example catheter 14 configured for sensing IEMM is illustrated herein. Physician 24 may position the distal end assembly 28 of catheter 14 in contact with the heart wall for sensing the target site within heart 12. For ablation, physician 24 may similarly position the distal end of an ablation catheter in contact with the target site for ablation of tissue.

[0017] As shown in Illustration 65, catheter 14 is an exemplary catheter comprising one, and preferably multiple, electrodes 26 optionally distributed over multiple splines 22 at an extendable distal end assembly 28 and configured to sense IEGM signals. Catheter 14 further comprises (i) a proximal position sensor 29 comprising two or three electromagnetic coils (EMCs) embedded in the distal end 46 of an axis 44 near the extendable distal end assembly 28, and (ii) optionally, one or more distal position sensors 39 that track the position of the distal end of the extendable distal end assembly 28. Optionally, and preferably, position sensors 29 and 39 are magnetically based position sensors. The illustration also shows the longitudinal axis 42 of catheter 14 and the distal edge 16 of the distal end assembly 28. Alternatively, catheter 14 has an elongated distal end comprising multiple annular electrodes. In this example catheter, the elongated distal end forms a loop in a neutral state, which is configured (e.g., sized and shaped to) be positioned around the orifices of four pulmonary veins extending from the left atrium of the patient.

[0018] Figure 2 Expanded views of illustrations 45 and 65 are provided, and an expandable distal end assembly 28 in contact with tissue 80 of the heart 12 is shown.

[0019] A magnetically based position sensor can operate in conjunction with a positioning pad 25, which includes a plurality of magnetic coils 32 configured to generate a magnetic field in a predefined workspace. The real-time position of the distal end assembly 28 of the conduit 14 can be tracked based on the magnetic field generated by the positioning pad 25 and sensed by the magnetically based position sensor. Details of the magnetically based position sensing technology are described in U.S. Patents Nos. 5,391,199, 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.

[0020] System 10 may also include one or more electrode patches 38 positioned to contact the skin of patient 23 to establish a position reference for impedance-based tracking of positioning pad 25 and electrodes 26. For impedance sensing, current is directed to electrodes 26 and sensed at the electrode skin patch 38 or between a pair of electrodes 26.

[0021] Recorder 11 can record and display an electrocardiogram 21 captured using surface ECG electrodes 18 and an intracardiac electrocardiogram (IEGM) captured using electrodes 26 of catheter 14. Recorder 11 may include pacing capability for pacing rhythms and / or be electrically connected to a separate pacemaker. System 10 may include an ablation energy generator 50 adapted to conduct ablation energy to one or more electrodes at the distal end of a catheter configured for ablation. The energy generated by ablation energy generator 50 may include, but is not limited to, radio frequency (RF) energy or pulsed field ablation (PFA) energy (including monopolar or bipolar high-voltage DC pulses that can be used to achieve irreversible electroporation (IRE), or combinations thereof.

[0022] The patient interface unit (PIU) 30 is configured to establish electrical communication between catheters, other electrophysiological equipment, a power supply, and a workstation 55 for operating the control system 10. The electrophysiological equipment of the system 10 may include, for example, multiple catheters, positioning pads 25, surface ECG electrodes 18, electrode patches 38, an ablation energy generator 50, and a recorder 11. Optionally and preferably, the PIU 30 also has processing capabilities for real-time calculation of catheter position and for performing ECG calculations.

[0023] Workstation 55 includes memory 57, a processor unit 56 containing appropriate operating software in the memory or storage device, and user interface features. Workstation 55 may provide a variety of functions, optionally including: (1) The endocardial anatomy is modeled in three dimensions (3D) and a 3D graphical representation of the model or anatomical mapping 20 is presented for display on the display device 27; (2) Display the activation sequence (or other data) compiled from the recorded electrophysiological map 21 on the display device 27 with representative visual markers or images superimposed on the presented anatomical map 20. (3) Model the catheter inserted into the body in three dimensions (3D) and present a 3D graphical representation of the model for display on display device 27; (4) Displays the real-time position and orientation of multiple catheters within the cardiac chambers; and (5) Display the target area where ablation energy has been applied on the display device 27.

[0024] A product embodying the components of system 10, the CARTO™ 3 system, is available from Biosense Webster, Inc., 31A Technology Drive, Irvine, CA 92618.

[0025] It should be noted that tissue impedance is generally greater than blood impedance, and a greater impedance value is expected to be measured at electrodes closer to the tissue than at electrodes further away from the tissue wall and immersed in the blood. In some examples, tissue proximity is based on patient-specific minimum and maximum impedance values ​​measured within the patient.

[0026] Now for reference Figure 3 This is a simplified qualitative example illustrating, according to one aspect of the present disclosure, the impedance measured by an electrode in the body cavity as a function of the distance from the cavity wall tissue 80. Figure 3 A graph showing the X-axis 302 and the Y-axis 304 of the impedance value with a qualitative proximity value (e.g., TPI) of the proximity to the cavity wall tissue 80 is shown. Figure 3 The graph includes line 306, which indicates the impedance value of the electrodes in the body cavity as a function of the qualitative proximity of the cavity wall, and also includes a continuation of line 306 into the region where the electrodes contact the cavity wall at various pressure levels.

[0027] Figure 3 The graph illustrates the expected impedance behavior within the body cavity as a function of proximity. It should be noted that proximity to the cavity wall increases as the distance from the cavity wall decreases. Figure 3 The graph shows the expected shape of the impedance approximation relationship.

[0028] In some exemplary modes, in vivo measurements can determine the impedance values, minimum and maximum values ​​at the endpoints. These minimum and maximum values ​​can be determined for each patient, optionally through real-time accumulated data, and by determining the minimum and maximum values ​​of the real-time data.

[0029] It should be noted that the minimum and maximum impedance values ​​for each electrode are functions of the distance from the electrode to the reference electrode. In some examples, the minimum and maximum impedance values ​​for each electrode are adjusted to determine the normalized minimum and maximum impedance values ​​for all electrodes.

[0030] In some examples, the data points used to construct line 306 are optionally measured in vivo by measuring impedance using electrodes that move within the body cavity. Line 306 is generated using all or at least some of the measurements.

[0031] In some examples, the maximum and minimum impedance values ​​are optionally determined only for each patient via in vivo measurements. In some examples, the data points used to construct line 306 are optionally measured in vivo via a position measurement system comprising several electrodes moving within the body cavity, electrodes for measuring impedance, and optionally electrodes for measuring electrode positions.

[0032] In some examples, the data points used to construct line 306 are optionally obtained from a database that includes data measured for a specific patient at a certain historical time. In some examples, the data points used to construct line 306 are optionally obtained from a database that includes data measured (optionally averaged) for a group of patients at a certain historical time.

[0033] Figure 3 Two specific levels of impedance along the Y-axis 304 are also shown. The first specific impedance level 308 shows the impedance at which the electrode begins to contact the cavity wall, and the distance to the cavity wall is close to zero. Line 306 to the left of the contact impedance is in the “no-contact” impedance region 312. In some examples, the value of the first specific impedance level 308 is determined to be a specific percentage lower than the maximum value of line 306.

[0034] The second specific impedance level 310 shows the impedance of the electrodes that contact and push against the cavity wall with a force considered sufficient to perform ablation (if necessary) using the electrodes. A corresponding “contact” region 314 is shown, in which the cavity wall is slightly pushed from the contact point to produce a sufficiently good contact due to the greater force applied to the cavity wall. Outside the “contact” region 314, the impedance flattens out to its maximum value, and this is shown by the “saturation” region 316 and the high impedance above the level indicated by 310.

[0035] Now for reference Figure 4A and Figure 4B These figures include those used for Figure 1 Flowchart 400 shows the steps in the method for adjusting the threshold of the organizational proximity index in the system. First, for Figure 4A Each process shown is explained.

[0036] In some examples, processor unit 56 is configured, for example, using the reference above. Figure 3 The described method identifies the minimum and maximum impedances and their corresponding minimum and maximum TPI limits (box 402); and defines the estimated TPI threshold as a function between and based on the minimum and maximum TPI limits (box 404). In some examples, the estimated TPI threshold may be defined as a given distance from the minimum or maximum value, or at a given ratio between the minimum and maximum TPI limits.

[0037] In some examples, processor unit 56 is configured to receive user input to determine threshold adjustment parameters A and B (box 406), as described in more detail below.

[0038] PIU 30 (or any suitable controller) is configured to: sample intracardiac electrogrammage (IEGM) signals from a given electrode (e.g., one of the electrodes 26) (e.g., prior to ablation at the target tissue location) (box 408); and sense the impedance between the given electrode 26 and tissue 80 based on, for example, impedance measured between the given electrode 26 and another catheter electrode 26 or surface electrode 18 (box 410). Catheter 14 ( Figure 1 It includes a given electrode 26 that provides an IEGG signal, and a signal for sensing the impedance between the given electrode 26 and the tissue 80.

[0039] Processor unit 56 is configured to compare the measured impedance with an (estimated or current) TPI threshold to determine the contact state of a given electrode 26 relative to tissue 80 (box 414). In some examples, the contact state is no contact if the measured impedance is less than or equal to the TPI threshold, and in contact if the measured impedance is greater than the TPI threshold. In other examples, the contact state is no contact if the measured impedance is less than the TPI threshold, and in contact if the measured impedance is greater than or equal to the TPI threshold. The contact state indicates whether the proximity of the given electrode 26 to tissue 80 is sufficient to cause a predefined reduction in the IEGM signal due to ablation. The reduction in the IEGM signal can be defined as the reduction in the IEGM signal measured after ablation, based on the peak-to-peak measurement of the IEGM signal in a target window of the IEGM signal, compared to the measurement performed before ablation.

[0040] Processor unit 56 is configured to present an indication (box 416) of the contact state of a given electrode relative to tissue to display device 27. The indication may include text values ​​(e.g., “in contact” or “out of contact”) and / or color values ​​(e.g., “red” for out of contact and “green” for in contact).

[0041] Now describing Figure 4B The steps are shown in the figure.

[0042] The ablation energy generator 50 is configured to conduct ablation energy to a given electrode 26 of the catheter 14 based on user input, typically under the control of the physician 24, and the processor unit 56 is configured to check the movement stability of the given electrode 26 during ablation, for example by monitoring the position of the given electrode 26 during ablation (box 418).

[0043] In some examples, at decision box 420, processor unit 56 determines whether the stability of a given electrode 26 is within a given limit (e.g., user-defined). If the stability of the given electrode 26 is not within the given limit, the method returns to... Figure 4AThe step shown in block 408 involves processor unit 56 being configured to sample the IEGM signal from given electrode 26 prior to another ablation (e.g., at a different ablation site). If the stability of given electrode 26 is within a given limit, the method proceeds to the step in block 422.

[0044] PIU 30 (or any suitable controller) is configured to sample intracardiac electrogram (IEGM) signals from a given electrode 26 (e.g., after ablation at the target tissue location) (box 422), and the processing unit is configured to calculate the change in the peak-to-peak voltage of the IEGM signal due to the current ablation.

[0045] Processor unit 56 is configured to adjust the TPI threshold for subsequent ablation based on a calculated change in the IEGM signal resulting from the current ablation of tissue 80 using the given electrode 26 (box 426). Therefore, while the stability of the given electrode is checked in the step of box 418, the step of box 426 depends on the stability of the movement of the given electrode 26 being within one or more given limits. The TPI threshold is adjusted based on a decrease in IEGM. If the observed decrease in IEGM is greater than a given decrease, the TPI threshold is decreased based on the decrease in IEGM. If the observed decrease in IEGM is less than or equal to a given decrease, the TPI threshold can be increased. Adjustment of the TPI threshold allows for gradual adjustment until the TPI threshold reaches or approaches a target TPI threshold. A new TPI threshold can be calculated using the following formula: New TPI threshold = Old TPI threshold - (ΔV - B)A, ΔV is the reduction in the voltage amplitude of the IEGM due to ablation, and A and B are threshold adjustment factors. A and B are chosen to achieve a gradual change in the TPI threshold toward the target “actual” TPI threshold. For example, if ΔV is expected to be about 4 mV, then B could be about 0.3 or 0.4, and A could be, for example, about 5. However, any suitable value for A and B can be selected by the user, for example.

[0046] In some exemplary modes, processor unit 56 is configured to adjust the TPI threshold for each electrode 26 of catheter 14. In other words, system 10 manages multiple TPI thresholds that are electrode-specific and adjusted based on data from the respective electrode 26. In other exemplary modes, processor unit 56 is configured to adjust the TPI thresholds such that the same TPI threshold is maintained for the multiple electrodes 26 of catheter 14.

[0047] Processor unit 56 is configured to iteratively adjust the TPI threshold based on the corresponding previous TPI threshold and the corresponding decrease in the voltage of the IEGM signal due to ablation at the corresponding ablation site. In other words, steps 408 to 426 are repeated at different ablation sites, and the TPI threshold can be adjusted at step 426 after each ablation to converge toward an optimal TPI threshold that best indicates the proximity required to achieve the desired reduction in peak-to-peak IEGM voltage due to ablation (or the desired lesion).

[0048] In practice, some or all of these functions of processor 56 may be combined in a single physical component, or alternatively, implemented using multiple physical components. These physical components may include hardwired or programmable devices, or a combination of both. In some examples, at least some of the functions of processor unit 56 may be implemented by a programmable processor under the control of suitable software. This software may be downloaded electronically to the device via, for example, a network. Alternatively or additionally, the software may be stored in a tangible, non-transitory computer-readable storage medium, such as optical, magnetic, or electronic memory.

[0049] As used herein, the term “about” or “approximately” for any numerical value or range indicates appropriate dimensional tolerances that allow a collection of parts or components to achieve the intended purpose as described herein. More specifically, “about” or “approximately” may refer to a range of ±20% of the enumerated value; for example, “about 90%” may refer to a range of values ​​from 72% to 108%. Example

[0050] Example 1: An apparatus comprising: a catheter including electrodes providing an intracardiac electrogram (IEGM) signal and a signal for sensing impedance; an ablation energy generator configured to conduct ablation energy to the electrodes of the catheter based on user input; a controller configured to: sample the IEGM signal from the electrodes before and after a given ablation; and sense the impedance between the electrodes and tissue; and a processor configured to: compare the sensed impedance with a TPI threshold to determine a contact state of the electrodes relative to the tissue; present an indication of the determined contact state to a display; calculate a change in the IEGM signal due to the given ablation; and adjust the TPI threshold for subsequent ablation based on the calculated change in the IEGM signal due to the given ablation of the tissue using the electrodes.

[0051] Example 2: The device according to Example 1, wherein the processor is configured to iteratively adjust the TPI threshold based on a corresponding previous TPI threshold and a corresponding decrease in the voltage of the IEGM signal due to ablation at the corresponding ablation site.

[0052] Example 3: The device according to Example 1 or 2, wherein the processor is configured to: check the mobility stability of the electrode during ablation; and adjust the TPI threshold based on the mobility stability of the electrode within a given limit.

[0053] Example 4: The device according to any one of Examples 1 to 3, wherein the processor is configured to reduce the TPI threshold based on at least a given decrease in the IEGM signal observed due to ablation of the tissue using the electrode.

[0054] Example 5: The device according to any one of Examples 1 to 3, wherein the processor is configured to increase the TPI threshold based on a given decrease in the IEGM signal observed to be less than that caused by ablation of the tissue using the electrode.

[0055] Example 6: The device according to any one of Examples 1 to 5, wherein the processor is configured to receive user input to determine a threshold adjustment factor.

[0056] Example 7: The device according to any one of Examples 1 to 6, wherein the processor is configured to: identify a minimum impedance and a maximum impedance and corresponding minimum TPI limit and maximum TPI limit; and define the estimated TPI threshold as a function between the minimum TPI limit and the maximum TPI limit and based on the minimum TPI limit and the maximum TPI limit.

[0057] Example 8: The device according to any one of Examples 1 to 7, wherein the processor is configured to adjust the TPI threshold of each electrode of the catheter.

[0058] Example 9: The device according to any one of Examples 1 to 7, wherein the processor is configured to adjust the TPI threshold such that the same TPI threshold is maintained for the plurality of electrodes of the catheter.

[0059] Example 10: The device according to any one of Examples 1 to 9, wherein the processor is configured to calculate a new TPI threshold based on a previous TPI threshold minus a first factor multiplied by the following: a decrease in the voltage of the IEGM signal minus a second factor.

[0060] Example 11: A method comprising: providing an intracardiac electrogram (IEGM) signal and a signal for sensing impedance by electrodes of a catheter; conducting ablation energy to the electrodes of the catheter based on user input; sampling the IEGM signal from the electrodes before and after a given ablation; sensing the impedance between the electrodes and tissue; comparing the sensed impedance with a TPI threshold to determine a contact state of the electrodes relative to the tissue; presenting an indication of the determined contact state to a display; calculating the change in the IEGM signal due to the given ablation; and adjusting the TPI threshold for subsequent ablation based on the calculated change in the IEGM signal due to the given ablation of the tissue using the electrodes.

[0061] Example 12: According to the method of Example 11, the method further includes iteratively adjusting the TPI threshold based on the corresponding previous TPI threshold and the corresponding decrease in the voltage of the IEGM signal due to ablation at the corresponding ablation site.

[0062] Example 13: The method according to Example 11 or 12, the method further includes checking the mobility stability of the electrode during ablation, and wherein the adjustment includes adjusting the TPI threshold based on the mobility stability of the electrode within a given limit.

[0063] Example 14: The method according to any one of Examples 11 to 13, the method further includes reducing the TPI threshold based on at least a given decrease in the IEGM signal observed due to ablation of the tissue using the electrode.

[0064] Example 15: The method according to any one of Examples 11 to 13, the method further includes increasing the TPI threshold based on observing a given decrease in the IEGM signal that is less than that caused by ablation of the tissue using the electrode.

[0065] Example 16: The method according to any one of Examples 11 to 15, the method further includes receiving the user input to determine a threshold adjustment factor.

[0066] Example 17: The method according to any one of Examples 11 to 16, the method further comprising: identifying a minimum impedance and a maximum impedance and corresponding minimum TPI limit and maximum TPI limit; and defining the estimated TPI threshold as a function between the minimum TPI limit and the maximum TPI limit and based on the minimum TPI limit and the maximum TPI limit.

[0067] Example 18: The method according to any one of Examples 11 to 17, wherein the adjustment includes adjusting the TPI threshold of each electrode of the catheter.

[0068] Example 19: The method according to any one of Examples 11 to 17, wherein the adjustment includes adjusting the TPI threshold such that the same TPI threshold is maintained for the plurality of electrodes of the catheter.

[0069] Example 20: The method according to any one of Examples 11 to 19, the method further includes calculating a new TPI threshold based on a previous TPI threshold minus a first factor multiplied by a second factor: the decrease in voltage of the IEGM signal minus a second factor.

[0070] For clarity, the various features of this disclosure described in the context of individual embodiments may also be provided in combination in a single embodiment. Conversely, for simplicity, the various features of this disclosure described in the context of individual embodiments may also be provided individually or in any suitable sub-combination.

[0071] The above embodiments are cited by way of example, and this disclosure is not limited to the content specifically shown and described above. Rather, the scope of this disclosure includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which will occur to those skilled in the art upon reading the above description and which are not disclosed in the prior art.

Claims

1. An apparatus comprising: The catheter (14) includes electrodes (26) that provide intracardiac electrogram (IEGM) signals and signals for sensing impedance. Ablation energy generator (50), which is configured to conduct ablation energy to the electrode (26) of the catheter (14) based on user input. Controller (30), the controller is configured to: The IEGM signal from the electrode (26) is sampled before and after a given ablation; and The impedance between the electrode (26) and the tissue (80) is sensed; and Processor (56), the processor being configured to: The sensed impedance is compared with a tissue proximity index (TPI) threshold to determine the contact state of the electrode (26) relative to the tissue (80); Present an indication of the determined contact state to the display (27); Calculate the change in the IEGM signal due to the given ablation; and The TPI threshold for subsequent ablation is adjusted based on the calculated change in the IEGM signal resulting from the given ablation of the tissue (80) using the electrode (26).

2. The device according to claim 1, wherein, The processor (56) is configured to iteratively adjust the TPI threshold based on the corresponding previous TPI threshold and the corresponding decrease in the voltage of the IEGM signal due to ablation at the corresponding ablation site.

3. The device according to claim 1, wherein, The processor (56) is configured to: The stability of the electrode (26) during ablation was examined; and The TPI threshold is adjusted within a given limit based on the mobility stability of the electrode (26).

4. The device according to claim 1, wherein, The processor (56) is configured to reduce the TPI threshold based on at least a given decrease in the IEGM signal observed due to the ablation of the tissue (80) by the electrode (26).

5. The device according to claim 1, wherein, The processor (56) is configured to increase the TPI threshold based on a given decrease in the IEGM signal observed due to ablation of the tissue (80) using the electrode (26).

6. The device according to claim 1, wherein, The processor (56) is configured to receive user input to determine a threshold adjustment factor.

7. The device according to claim 1, wherein, The processor (56) is configured to: Identify the minimum and maximum impedances, as well as the corresponding minimum and maximum TPI limits; as well as The estimated TPI threshold is defined as a function between the minimum TPI limit and the maximum TPI limit, and based on the minimum TPI limit and the maximum TPI limit.

8. The device according to claim 1, wherein, The processor (56) is configured to adjust the TPI threshold of each electrode (26) of the conduit (14).

9. The device according to claim 1, wherein, The processor (56) is configured to adjust the TPI threshold such that the same TPI threshold is maintained for the multiple electrodes (26) of the catheter (14).

10. The device according to any one of claims 1 to 9, wherein, The processor (56) is configured to calculate a new TPI threshold based on the previous TPI threshold minus a first factor multiplied by the following: the decrease in voltage of the IEGM signal minus a second factor.

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