Indicator electrode contact

Abstract

The present invention is entitled "Indicating Electrode Contact". In one embodiment, a medical system comprises: a catheter to be inserted into a chamber of the heart of a living subject, and the catheter comprises catheter electrodes configured to contact tissue at respective locations within the chamber of the heart; a display; and processing circuitry for: receiving signals from the catheter; and in response to the signals, evaluating respective contact qualities of each of the catheter electrodes with tissue in the heart, and plotting respective intracardiac electrogram traces representing electrical activity in the tissue sensed by the catheter electrodes at the respective locations to the display, while modifying visual features of at least some of the traces in response to respective contact qualities of the catheter electrodes with tissue of the heart at the respective locations.

Description

Technical Field

[0001] The present invention relates to medical systems and particularly, but not exclusively, to catheter based systems. Background Art

[0002] A large number of medical procedures involve placing probes such as catheters in the patient's body. Position sensing systems have been developed to track such probes. Magnetic position sensing is a method known in the art. In magnetic position sensing, a magnetic field generator is usually placed at a known position outside the patient's body. The magnetic field sensor in the distal end of the probe generates electrical signals in response to these magnetic fields, and the electrical signals are processed to determine the coordinate position of the distal end of the probe. These methods and systems are described in U.S. Patents 5,391,199, 6,690,963, 6,484,118, 6,239,724, 6,618,612 and 6,332,089, in PCT International Patent Publication WO 1996 / 005768, and in U.S. Patent Application Publication 2002 / 006455, and 2003 / 0120150, and 2004 / 0068178, the disclosures of which are all incorporated herein by reference. Impedance or current-based systems can also be used to track positions.

[0003] Arrhythmia treatment surgery is a medical procedure in which these types of probes or catheters have proven extremely useful. Cardiac arrhythmias and specifically atrial fibrillation continue to be common and dangerous medical conditions, especially in the elderly.

[0004] Diagnosis and treatment of arrhythmias include mapping the electrical properties of cardiac tissue, particularly the endocardium and cardiac volume, and selectively ablating cardiac tissue by applying energy. Such ablation can stop or alter the propagation of unwanted electrical signals from one part of the heart to another. Ablation methods destroy unwanted electrical pathways by forming non-conductive lesions. A variety of energy delivery modalities for forming lesions have been disclosed, and include the use of microwaves, lasers, and more commonly radiofrequency energy to form conduction blocks along the walls of cardiac tissue. In a two-step procedure (mapping followed by ablation), electrical activity at various points within the heart is typically sensed and measured by advancing a catheter including one or more electrical sensors into the heart and collecting data at multiple points. This data is then used to select a target area of ​​the endocardium to be ablated.

[0005] Electrode catheters have been commonly used in medical practice for many years. They are used to stimulate and map electrical activity in the heart, as well as to ablate sites of abnormal electrical activity. When used, the electrode catheter is inserted into a major vein or artery, such as the femoral artery, and then guided into the heart chamber of interest. A typical ablation procedure involves inserting a catheter having one or more electrodes at its distal end into the heart chamber. A reference electrode, which is usually taped to the patient's skin, can be provided, or a second catheter disposed in or near the heart can be used to provide the reference electrode. RF (radio frequency) current is applied to the top electrode of the ablation catheter, and the current flows to the reference electrode through the surrounding medium (i.e., blood and tissue). The distribution of the current depends on the amount of contact between the electrode surface and the tissue compared to blood, which has a higher conductivity than tissue. Due to the resistance of the tissue, heating of the tissue occurs. The tissue is heated sufficiently to cause cell destruction in the cardiac tissue, resulting in the formation of non-conductive ablation lesions in the cardiac tissue.

[0006] Therefore, when placing an ablation catheter or other catheter in the body (especially near endocardial tissue), it is desirable to have the distal tip of the catheter in direct contact with the tissue. The contact can be confirmed by, for example, measuring the contact between the distal tip and the body tissue. U.S. Patent Application Publications 2007 / 0100332, 2009 / 0093806, and 2009 / 0138007 (the disclosures of which are incorporated herein by reference) describe methods of sensing the contact pressure between the distal tip of the catheter and tissue in a body cavity using a force sensor embedded in the catheter.

[0007] Many references have reported methods for determining electrode-tissue contact, including U.S. Patents 5,935,079, 5,891,095, 5,836,990, 5,836,874, 5,673,704, 5,662,108, 5,469,857, 5,447,529, 5,341,807, 5,078,714, and Canadian Patent Application 2,285,342. Several of these references, such as U.S. Patents 5,935,079, 5,836,990, and 5,447,529, determine electrode-tissue contact by measuring the impedance between the tip electrode and the return electrode. As disclosed in the '529 patent, it is well known that the impedance through blood is generally lower than the impedance through tissue. Therefore, tissue contact is detected by comparing the impedance values ​​between a set of electrodes with the pre-measured impedance values ​​when the known electrodes are in contact with tissue and the known electrodes are in contact with blood only.

[0008] U.S. Patent 9,168,004 to Gliner et al., which is incorporated herein by reference, describes the use of machine learning to determine catheter electrode contact. The '004 patent describes a cardiac catheterization procedure performed by memorizing the assignment of the contact state between an electrode of a probe and a heart wall as either a contact state or a no contact state, and making a series of determinations of the impedance phase angle of the current passing through the electrode and another electrode, thereby identifying the maximum and minimum phase angles in the series, and adaptively bounding a binary classifier in the middle of the limit values. A test value is compared to the classifier adjusted by a hysteresis factor, and a change in contact state is reported when the test value exceeds or falls below the adjusted classifier.

[0009] U.S. Patent Publication 2013 / 0085416 to Mest, incorporated herein by reference, describes a method for in vivo recalibration of a force sensing probe such as an electrophysiology catheter, which is used to generate an automatic zeroing zone. The distal tip of the catheter or other probe is placed in the body cavity of the patient. The absence of tissue contact is confirmed using an electrocardiogram (ECG) or impedance data, fluoroscopic or other real-time imaging data, and / or an electroanatomical mapping system. Once the absence of tissue contact is confirmed, the system recalibrates the signal from the force sensor to correspond to a force reading of zero grams and uses this calibrated baseline reading to generate and display a force reading based on the force sensor data. Summary of the invention

[0010] According to an embodiment of the present disclosure, a medical system is provided, which includes: a catheter configured to be inserted into a chamber of the heart of a living subject and including catheter electrodes configured to contact tissue at corresponding positions in the chamber of the heart; a display; and a processing circuit configured to: receive a signal from the catheter; and in response to the signal, evaluate the corresponding contact quality of each of the catheter electrodes with the tissue in the heart, and draw corresponding intracardiac electrogram (IEGM) traces representing electrical activity in the tissue sensed by the catheter electrode at the corresponding position to the display, while modifying visual features of at least some of the traces in response to the corresponding contact quality of the catheter electrodes with the tissue of the heart at the corresponding position.

[0011] Furthermore, in accordance with an embodiment of the present disclosure, the processing circuit is configured to increase the brightness of at least some of the traces in response to respective qualities of contact of the catheter electrode with tissue of the heart at respective locations.

[0012] In addition, according to an embodiment of the present disclosure, the processing circuit is configured to increase the brightness of the trace representing electrical activity sensed by a first one of the catheter electrodes having a high contact quality with the tissue relative to the trace representing electrical activity sensed by a second one of the catheter electrodes having a lower contact quality with the tissue.

[0013] Additionally, in accordance with an embodiment of the present disclosure, the processing circuit is configured to change a color of at least some of the traces in response to respective qualities of contact of the catheter electrodes with tissue of the heart at respective locations.

[0014] In addition, according to an embodiment of the present disclosure, the processing circuit is configured to change the color of the trace representing electrical activity sensed by a first one of the catheter electrodes having a high contact quality with the tissue relative to the trace representing electrical activity sensed by a second one of the catheter electrodes having a lower contact quality with the tissue.

[0015] Furthermore, in accordance with embodiments of the present disclosure, the processing circuit is configured to modify visual features of at least some traces representing electrical activity sensed by some of the catheter electrodes having a contact quality with the tissue greater than a predefined threshold contact quality.

[0016] Furthermore, according to an embodiment of the present disclosure, the processing circuit is configured to perform a first modification of a visual feature of one of the traces representing electrical activity sensed by one of the catheter electrodes having a contact quality with the tissue greater than a predefined threshold quality during a first time period, and to perform a second modification of a visual feature of one of the traces representing electrical activity sensed by one of the catheter electrodes having a contact quality with the tissue less than a predefined threshold quality during a second time period after the first time period.

[0017] Additionally, according to an embodiment of the present disclosure, the second modification of the visual characteristic changes as the second time period progresses.

[0018] Furthermore, according to an embodiment of the present disclosure, the second modification of the visual feature includes dimming of the visual feature as the second time period progresses.

[0019] Furthermore, according to an embodiment of the present disclosure, the system includes a body surface electrode configured to be applied to the skin surface of a living subject, wherein the processing circuit is configured to measure an indication of electrical impedance between the body surface electrode and the catheter electrode, and to calculate a position coordinate of the catheter electrode in response to the indication of the electrical impedance.

[0020] Additionally, in accordance with an embodiment of the present disclosure, the processing circuit is configured to assess a respective quality of contact of each of the catheter electrodes with tissue in the heart in response to the indication of the electrical impedance.

[0021] According to another embodiment of the present disclosure, a medical method is also provided, which includes: receiving a signal from a catheter, the catheter being configured to be inserted into a chamber of the heart of a living subject and including catheter electrodes configured to contact tissue at corresponding positions in the chamber of the heart; in response to the signal, evaluating the corresponding contact quality of each of the catheter electrodes with the tissue in the heart, and drawing corresponding intracardiac electrogram (IEGM) traces representing electrical activity in the tissue sensed by the catheter electrode at the corresponding position to a display, while modifying visual features of at least some of the traces in response to the corresponding contact quality of the catheter electrodes with the tissue of the heart at the corresponding position.

[0022] Additionally, in accordance with an embodiment of the present disclosure, the method includes increasing brightness of at least some of the traces in response to respective qualities of contact of the catheter electrode with tissue of the heart at respective locations.

[0023] Furthermore, according to an embodiment of the present disclosure, the increasing includes increasing the brightness of the trace representing electrical activity sensed by a first one of the catheter electrodes having a high contact quality with the tissue relative to the trace representing electrical activity sensed by a second one of the catheter electrodes having a lower contact quality with the tissue.

[0024] Furthermore, in accordance with an embodiment of the present disclosure, the method includes changing a color of at least some of the traces in response to respective qualities of contact of the catheter electrodes with tissue of the heart at respective locations.

[0025] Furthermore, according to an embodiment of the present disclosure, the changing includes changing the color of a trace representing electrical activity sensed by a first one of the catheter electrodes having a high contact quality with the tissue relative to a trace representing electrical activity sensed by a second one of the catheter electrodes having a lower contact quality with the tissue.

[0026] Additionally, in accordance with embodiments of the present disclosure, the modifying includes modifying visual features of at least some traces representing electrical activity sensed by some of the catheter electrodes having a contact quality with the tissue greater than a predefined threshold contact quality.

[0027] Furthermore, according to an embodiment of the present disclosure, the method includes performing a first modification of a visual feature of one of the traces representing electrical activity sensed by one of the catheter electrodes having a contact quality with the tissue greater than a predefined threshold quality during a first time period, and performing a second modification of a visual feature of one of the traces representing electrical activity sensed by one of the catheter electrodes having a contact quality with the tissue less than a predefined threshold quality during a second time period after the first time period.

[0028] Furthermore, according to an embodiment of the present disclosure, the second modification of the visual characteristic changes as the second time period progresses.

[0029] Furthermore, according to an embodiment of the present disclosure, the second modification of the visual feature includes dimming of the visual feature as the second time period progresses.

[0030] Additionally, according to an embodiment of the present disclosure, the method includes measuring an indication of electrical impedance between a body surface electrode configured to be applied to a skin surface of a living subject and a catheter electrode, and calculating a position coordinate of the catheter electrode in response to the indication of electrical impedance.

[0031] Furthermore, in accordance with an embodiment of the present disclosure, the assessing includes assessing a respective quality of contact of each of the catheter electrodes with tissue in the heart in response to the indication of the electrical impedance.

[0032] According to another embodiment of the present disclosure, a software product is also provided, which includes a non-transitory computer-readable medium having program instructions stored therein, which, when read by a central processing unit (CPU), causes the CPU to: receive a signal from a catheter, the catheter being configured to be inserted into a chamber of the heart of a living subject and including catheter electrodes configured to contact tissue at corresponding positions in the chamber of the heart; in response to the signal, evaluate the corresponding contact quality of each of the catheter electrodes with the tissue in the heart, and draw corresponding intracardiac electrogram (IEGM) traces representing electrical activity in the tissue sensed by the catheter electrode at the corresponding position to a display, while modifying visual features of at least some of the traces in response to the corresponding contact quality of the catheter electrodes with the tissue of the heart at the corresponding position. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will be understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 A schematic diagram of a medical procedure constructed and operative in accordance with an embodiment of the present invention;

[0035] Figure 2 For use Figure 1 A schematic diagram of a catheter in a system;

[0036] Figure 3 To include Figure 1 A flowchart of exemplary steps in a method of operating a system;

[0037] Figure 4 To include electrical impedance based Figure 1 A flowchart of exemplary steps in a method of operating a system;

[0038] Figure 5 Reason Figure 1 a schematic diagram of a first exemplary intracardiac electrogram (IEGM) trace prepared by a system; and

[0039] Figure 6 Reason Figure 1 Schematic diagram of a second exemplary intracardiac electrogram (IEGM) trace prepared by a system. DETAILED DESCRIPTION

[0040] Overview

[0041] As mentioned previously, in a two-step procedure (mapping followed by ablation), electrical activity at various points in the heart is sensed and measured, typically by advancing a catheter containing one or more electrical sensors into the heart and acquiring data at multiple points. This data is then used to select a target area to be ablated.

[0042] Specifically, electrical activity is usually displayed as an intracardiac electrogram (IEGM) trace for analysis by physicians in order to find the source of arrhythmias. Catheter electrodes that are not in contact with tissue in the heart usually measure some electrical signals from the cardiac tissue and far-field signals. When the catheter electrodes are in contact with cardiac tissue, the amplitude of the signal depends primarily on tissue conductivity, while the far-field is secondary. Therefore, physicians are usually interested in analyzing the IEGM traces of electrodes in contact with tissue.

[0043] For focal catheters with one or two electrodes, a single IEGM trace is usually displayed for analysis by a physician. The physician can quickly determine whether the catheter electrode providing the signal is in contact with the tissue based on the form of the signal. However, a multi-electrode catheter that simultaneously collects electrical activity from different tissue locations can provide data from multiple IEGM traces to be displayed simultaneously on a single display. In some cases, the number of IEGM traces may be too large for the physician to easily determine which IEGM traces are provided by electrodes in contact with the tissue and which traces are not provided by electrodes in contact with the tissue.

[0044] An example of a multi-electrode catheter is the XT-500, which has more than 48 electrodes and is manufactured by Biosense Webster Inc. of Irvine, CA, USA. Catheter. Octaray includes eight flexible arms disposed at the distal end of the shaft, wherein each of the flexible arms includes six electrodes. Some catheters may include more electrodes, such as but not limited to 120 electrodes.

[0045] In addition to the need to determine electrode contact during the above-mentioned mapping, the physician performing the ablation procedure also monitors the contact of the electrode with the tissue, because effective ablation generally requires sufficient contact between the ablation electrode and the tissue. For a small number of electrodes, monitoring contact can be performed by presenting a measure of contact (such as impedance observed by the electrode or force on the electrode) in a numerical or even graphical manner. However, as the number of active electrodes used in ablation procedures increases, it becomes increasingly difficult for the physician to monitor any parameter of a single electrode. With respect to electrode contact, the problem is exacerbated by the fact that in most cases, as the contact changes, the parameter measuring the contact also changes.

[0046] Embodiments of the present invention address the above-described problems during medical procedures such as mapping or ablation procedures by presenting to the physician multiple IEGM traces (e.g., a graph of voltage versus time) of signals acquired by electrodes of a catheter while modifying the visual characteristics of these traces representing electrical activity sensed by electrodes believed to be in sufficient contact with cardiac tissue. Thus, the traces of electrodes with sufficient tissue contact are highlighted for easy identification by the physician.

[0047] Traces representing electrical activity sensed by electrodes that are in full contact with cardiac tissue are typically modified to be brighter than traces representing electrical activity sensed by electrodes that are not in full contact with cardiac tissue. The human eye is extremely sensitive to changes in brightness. Therefore, brighter traces allow physicians to more quickly identify relevant IEGM traces.

[0048] In some embodiments, traces representing electrical activity sensed by electrodes in sufficient contact with cardiac tissue are typically modified to a different color than traces representing electrical activity sensed by electrodes not in sufficient contact with cardiac tissue.

[0049] In other embodiments, traces representing electrical activity sensed by electrodes in sufficient contact with cardiac tissue are typically modified to be a different color and brighter than traces representing electrical activity sensed by electrodes not in sufficient contact with cardiac tissue.

[0050] The physician may then examine the highlighted signals and analyze them to locate arrhythmias and / or determine which electrodes are in contact with tissue for ablation purposes.

[0051] Because the unhighlighted traces indicate electrodes that do not have adequate tissue contact, the physician can use this indication to adjust the position of the catheter to improve tissue contact for the electrodes associated with the unhighlighted traces.

[0052] In some embodiments, a fading effect is used to dim the brightness or undo the color (for highlighting traces associated with electrodes in sufficient tissue contact) to restore to the original brightness and / or color (for traces associated with electrodes that do not have sufficient tissue contact) after the electrode associated with the trace is no longer in sufficient tissue contact. The fading effect may occur within any suitable time window, such as, but not limited to, one to three seconds. The fading effect helps eliminate brightness and / or color changes that would otherwise occur due to intermittent and / or varying contact quality.

[0053] In the above discussion, the adequacy of tissue contact is used to decide whether to highlight the IEGM trace. The quality of contact can be assessed based on different methods including impedance measurement, force or pressure measurement, or from analysis of the IEGM trace, as will now be described in more detail.

[0054] In response to the signal provided by the catheter, the processing circuit evaluates the corresponding contact quality of each of the catheter electrodes with the tissue in the heart. Any of the catheter electrodes may be in full or partial contact with the tissue of the heart. In some cases, any of the catheter electrodes may be in contact with the tissue via another fluid (such as blood of various thicknesses). The quality of contact (full or partial contact, or contact via another liquid) of any of the catheter electrodes with the tissue can be evaluated based on the signal provided by the catheter.

[0055] The term "contact quality" as used in this specification and claims is defined herein as a quantitative indicator of the degree of electrical contact between one of the catheter electrodes and the tissue. "Contact quality" may be expressed directly, for example, in measured electrical impedance, or indirectly, for example, in contact force, pressure, or IEGM amplitude, as will now be described in more detail below.

[0056] In some embodiments, the catheter can provide a signal that provides an indication of impedance between the catheter electrode and the body surface electrode. The indication of impedance provides an indication of contact quality, such that a higher impedance value between one of the catheter electrodes and the body surface electrode indicates a higher contact quality between the catheter electrode and the tissue. The impedance value can be selected to define a minimum contact quality that is considered to indicate adequate contact between any one of the catheter electrodes and the tissue.

[0057] In some embodiments, the impedance between one of the catheter electrodes and another of the electrodes on the catheter can be used as a measure of contact quality. As disclosed in the '529 patent mentioned in the background section above, it is well known that impedance through blood is generally lower than impedance through tissue. Therefore, tissue contact can be assessed by comparing the impedance values ​​between a set of electrodes with previously measured impedance values ​​when the electrodes are known to be in full contact with the tissue and when the electrodes are known to be in contact only with the blood.

[0058] In some embodiments, the method of U.S. Patent 9,168,004 to Gliner et al., which is incorporated herein by reference, can use a machine learning-based approach to assess contact quality.

[0059] In some embodiments, the catheter can provide a signal from a force sensor or a pressure sensor. The indication of force or pressure provides an indication of contact quality, such that higher force or pressure values ​​indicate higher contact quality between the catheter electrode and the tissue. The force or pressure value can be selected to define a minimum contact quality that is considered to indicate adequate contact between any of the catheter electrodes and the tissue.

[0060] In some embodiments, the generated IEGM trace can be used to assess the contact quality between any one of the catheter electrodes and the tissue. The maximum amplitude of the IEGM trace associated with one of the catheter electrodes indicates the contact quality between the catheter electrode and the tissue, such that a higher value of the maximum amplitude of the IEGM trace indicates a higher contact quality between the catheter electrode and the tissue. The amplitude value of the IEGM trace can be selected to define a minimum contact quality that is considered to represent adequate contact between any one of the catheter electrodes and the tissue.

[0061] System Description

[0062] Documents incorporated herein by reference shall be considered to be an integral part of this application, except that, to the extent that any term is defined in these incorporated documents in a manner that contradicts a definition explicitly or implicitly made in this specification, only the definition in this specification shall prevail.

[0063] See now Figure 1 , which is a schematic diagram of a medical surgical system 20 constructed and operative in accordance with an embodiment of the present invention. Referring now to Figure 2 , which is used for Figure 1 Schematic diagram of catheter 40 in system 20.

[0064] The medical surgical system 20 is used to determine the position of the catheter 40, such as in Figure 1 In Figure 25 and in Figure 2The catheter 40 includes a shaft 22 and a plurality of flexible arms 54 (only some are labeled for simplicity) for insertion into a body part of a living subject. The flexible arms 54 have respective proximal ends connected to the distal end of the shaft 22.

[0065] The catheter 40 includes an orientation sensor 53 disposed on the shaft 22 in a predefined spatial relationship relative to the proximal end of the flexible arm 54. The orientation sensor 53 may include a magnetic sensor 50 and / or at least one shaft electrode 52. The magnetic sensor 50 may include at least one coil, such as but not limited to a dual-axis or triple-axis coil arrangement, to provide orientation data of position and orientation (including yaw). The catheter 40 includes a plurality of electrodes 55 disposed at different corresponding positions along each of the flexible arms 54 (for simplicity, only some are labeled in FIG. 1 ). Figure 2 In general, catheter 40 may be used to map electrical activity in the heart of a living subject using electrodes 55, or may be used to perform any other suitable function in a body part of a living subject.

[0066] The medical surgical system 20 can determine the position and orientation of the shaft 22 of the catheter 40 based on the signals provided by the magnetic sensor 50 and / or the shaft electrodes 52 (proximal electrodes 52a and distal electrodes 52b) mounted on the shaft 22 and located on either side of the magnetic sensor 50. At least some of the proximal electrodes 52a, distal electrodes 52b, magnetic sensors 50, and electrodes 55 are connected to various driver circuits in the console 24 via wires extending through the shaft 22 via the catheter connector 35. In some embodiments, at least two of the electrodes 55 of each of the flexible arms 54, the shaft electrodes 52, and the magnetic sensors 50 are connected to the driver circuit in the console 24 via the catheter connector 35. In some embodiments, the distal electrodes 52b and / or the proximal electrodes 52a may be omitted.

[0067] Figure 2 The illustrations shown are chosen solely for conceptual clarity. Other configurations of shaft electrode 52 and electrode 55 are possible. Additional functionality may be included in position sensor 53. Elements not relevant to the disclosed embodiments of the present invention, such as irrigation ports, have been omitted for clarity.

[0068] The physician 30 navigates the catheter 40 to a target location in a body part (e.g., heart 26) of the patient 28 by manipulating the shaft 22 and / or deflection of the sheath 23 using the manipulator 32 near the proximal end of the catheter 40. The catheter 40 is inserted through the sheath 23 with the flexible arms 54 gathered together, and only after the catheter 40 is retracted from the sheath 23 are the flexible arms 54 able to expand and resume their intended functional shape. By housing the flexible arms 54 together, the sheath 23 also serves to minimize vascular trauma on its way to the target location.

[0069] The console 24 includes processing circuitry 41 (typically a general purpose computer) and suitable front-end and interface circuitry 44 for generating signals in and / or receiving signals from body surface electrodes 49, which are attached to the chest and back of the patient 28, or any other suitable skin surface, by wires passing through cables 39.

[0070] The console 24 also includes a magnetic sensing subsystem. The patient 28 is placed in a magnetic field generated by a pad including at least one magnetic field radiator 42, which is driven by a unit 43 disposed in the console 24. The magnetic field radiator 42 is configured to emit an alternating magnetic field into an area where a body part (e.g., the heart 26) is located. The magnetic field generated by the magnetic field radiator 42 generates a direction signal in the magnetic sensor 50. The magnetic sensor 50 is configured to detect at least a portion of the emitted alternating magnetic field and provide the direction signal as a corresponding electrical input to the processing circuit 41.

[0071] In some embodiments, the processing circuit 41 uses the position signals received from the shaft electrode 52, the magnetic sensor 50, and the electrode 55 to estimate the position of the catheter 40 within an organ (such as a heart chamber). In some embodiments, the processing circuit 41 correlates the position signals received from the electrodes 52, 55 with the previously acquired magnetic position-calibrated position signals to estimate the position of the catheter 40 within the heart chamber. The position coordinates of the shaft electrode 52 and the electrode 55 can be determined by the processing circuit 41 based on (among other inputs) the measured impedance between the electrodes 52, 55 and the body surface electrode 49, or the ratio of the current distribution. The console 24 drives the display 27, which shows the distal end of the catheter 40 within the heart 26.

[0072] Methods using current distribution measurements and / or position sensing of external magnetic fields are implemented in various medical applications, for example, in the Magnetic Field Imaging System manufactured by Biosense Webster Inc. (Irvine, California). and 7,848,787, PCT Patent Publication No. WO 96 / 05768, and U.S. Patent Application Publication Nos. 2002 / 0065455 A1, 2003 / 0120150 A1, and 2004 / 0068178 A1, the disclosures of which are incorporated herein by reference in their entirety.

[0073] 3 system applies an orientation tracking method based on active current positioning (ACL) impedance. In some embodiments, the processing circuit 41 is configured to use the ACL method to generate a mapping (e.g., a current-orientation matrix (CPM)) between an indication of electrical impedance and the orientation in the magnetic coordinate system of the magnetic field radiator 42. The processing circuit 41 estimates the orientation of the shaft electrode 52 and the electrode 55 by performing a lookup in the CPM.

[0074] The processing circuit 41 is typically programmed with software to perform the functions described herein. The software may be downloaded to the computer in electronic form over a network, for example, or it may alternatively or additionally be provided and / or stored on a non-transitory tangible medium such as magnetic, optical or electronic memory.

[0075] For simplicity and clarity, Figure 1 Only the elements related to the technology disclosed in the present invention are shown. System 20 generally includes additional modules and elements that are not directly related to the technology disclosed in the present invention and thus the additional modules and elements are not directly related to the technology disclosed in the present invention. Figure 1 and the corresponding descriptions are intentionally omitted.

[0076] The catheter 40 described above includes eight flexible arms 54, each of which has six electrodes. By way of example only, any suitable catheter may be used in place of the catheter 40, for example, a catheter having a different number of flexible arms and / or electrodes on each arm, or a different probe shape such as a balloon catheter or a lasso catheter.

[0077] The medical surgical system 20 may also use any suitable catheter, such as catheter 40 or a different catheter, and any suitable ablation method to perform ablation of cardiac tissue. The console 24 may include an RF signal generator 34 configured to generate RF power, which is applied by one or more electrodes of a catheter connected to the console 24 and one or more of the surface electrodes 49 to ablate the myocardium of the heart 26. The console 24 may include a pump (not shown) that pumps irrigation fluid to the distal end of the catheter performing the ablation via an irrigation channel. The catheter performing the ablation may also include a temperature sensor (not shown) for measuring the temperature of the myocardium during ablation and adjusting the ablation power and / or the irrigation rate of the pumping of the irrigation fluid according to the measured temperature.

[0078] See now Figure 3 , which includes Figure 1 Flowchart 60 of exemplary steps in a method of operating the system 20. See also Figure 1 and Figure 2 .

[0079] As previously mentioned, catheter 40 is configured to be inserted into a chamber of heart 26 of a living subject (patient 28). Catheter electrodes 55 are configured to contact tissue at corresponding locations within the chamber of heart 26.

[0080] The processing circuit 41 is configured to receive (block 62) signals from the catheter 40. Signals may be received from any of the catheter electrode 55, the shaft electrode 52, and / or the magnetic sensor 50, and in some embodiments, signals may be received from other sensors (such as force sensors or pressure sensors) that may provide measurements for assessing the quality of contact of the catheter electrode 55 with the tissue. These signals may also be used to calculate the position of the catheter electrode 55.

[0081] The processing circuit 41 is configured to calculate (block 64) the position of the catheter electrode 55 in response to the signal. The calculation of the position of the catheter electrode 55 may be based on any suitable position tracking system (e.g., based on measured impedance and / or current spread) or using the above referenced Figure 1 The ACL method is implemented.

[0082] The processing circuit 41 is configured to evaluate (block 66) the respective contact quality of each of the catheter electrodes 55 with tissue in the heart 26 in response to the signal. Any of the catheter electrodes 55 may be in full or partial contact with tissue of the heart 26. In some cases, any of the catheter electrodes 55 may be in contact with the tissue via another fluid, such as blood of varying thicknesses. The quality of contact (full or partial contact, or contact via another fluid) of any of the catheter electrodes 55 with the tissue may be evaluated based on the signal provided by the catheter 40.

[0083] As mentioned previously, the term "contact quality" is a quantitative indicator of the degree of electrical contact between one of the catheter electrodes 55 and the tissue. "Contact quality" may be expressed directly, such as in measured electrical impedance, or indirectly, such as in contact force, pressure, or IEGM amplitude, as will now be described in more detail below.

[0084] In some embodiments, the catheter 40 may provide a signal that provides an indication of the impedance between the catheter electrode 55 and the body surface electrode 49, as shown in FIG. Figure 4 The indication of impedance provides an indication of contact quality, such that a higher impedance value between one of the catheter electrodes 55 and the body surface electrode 49 indicates a higher contact quality between the catheter electrode 55 and the tissue. The impedance value may be selected to define a minimum contact quality that is considered to indicate adequate contact between any one of the catheter electrodes 55 and the tissue.

[0085] In some embodiments, the impedance between one of the catheter electrodes 55 and another of the electrodes on the catheter 40 can be used as a measure of the quality of contact. As disclosed in the '529 patent mentioned above in the background section, it is well known that impedance through blood is generally lower than impedance through tissue. Therefore, tissue contact can be assessed by comparing the impedance values ​​between a set of electrodes with previously measured impedance values ​​when the electrodes are known to be in full contact with the tissue and when the electrodes are known to be in contact only with the blood.

[0086] In some embodiments, the method of U.S. Pat. No. 9,168,004 to Gliner et al., which is incorporated herein by reference, may be used to assess contact quality. The '004 patent describes the use of machine learning to determine catheter electrode contact. The '004 patent describes a cardiac catheterization performed by memorizing the assignment of the contact state between an electrode of a probe and a heart wall as a contact state or a non-contact state, and making a series of determinations of the impedance phase angle of the current passing through the electrode and another electrode, thereby identifying the maximum and minimum phase angles in the series, and adaptively bounding a binary classifier in the middle of the limit values. A test value is compared to a classifier adjusted by a hysteresis factor, and a change in contact state is reported when the test value exceeds or falls below the adjusted classifier.

[0087] In some embodiments, the catheter 40 may provide a signal from a force sensor or pressure sensor (not shown) disposed at different locations on the flexible arm 54 that provides an indication of the force or pressure applied by the catheter electrode 55 on the tissue. The indication of force or pressure provides an indication of contact quality, such that a higher force or pressure value indicates a higher contact quality between the catheter electrode 55 and the tissue. The force or pressure value may be selected to define a minimum contact quality that is considered to represent adequate contact between any one of the catheter electrodes 55 and the tissue. These embodiments may use any suitable force or pressure sensor and any suitable method for measuring force or pressure, including any of the patents or patent publications mentioned in the background section and including the method described in U.S. Patent Publication 2013 / 0085416 to Mest, which is incorporated herein by reference and describes a method for in vivo recalibration of a force sensing probe such as an electrophysiology catheter, which is used to generate an automatic zeroing region. The distal tip of the catheter or other probe is placed in the body cavity of the patient. The absence of tissue contact is confirmed using electrocardiogram (ECG) or impedance data, fluoroscopic or other real-time imaging data, and / or an electroanatomical mapping system. Once the absence of tissue contact is confirmed, the system recalibrates the signal from the force sensor to correspond to a force reading of zero grams and uses this calibrated baseline reading to generate and display a force reading based on the force sensor data.

[0088] In some embodiments, the contact quality between any one of the catheter electrodes 55 and the tissue can be assessed using an intracardiac electrogram (IEGM) trace generated by the processing circuit 41. The maximum amplitude of the IEGM trace associated with one of the catheter electrodes 55 indicates the contact quality between that catheter electrode 55 and the tissue, such that higher values ​​of the maximum amplitude of the IEGM trace indicate higher contact quality between that catheter electrode 55 and the tissue. The amplitude values ​​of the IEGM trace can be selected to define a minimum contact quality that is considered to represent adequate contact between any one of the catheter electrodes 55 and the tissue.

[0089] See now Figure 4 , which includes impedance-based Figure 1 Flowchart 80 of exemplary steps in a method of operating system 20. Flowchart 80 includes steps that may be substituted for or in addition to Figure 3 The steps of frame 64 and frame 66 are performed. Figure 1 and Figure 2 .

[0090] The processing circuit 41 is configured to measure (block 82) an indication of electrical impedance between the body surface electrode 49 and the catheter electrode 55. The processing circuit 41 is configured to calculate (block 84) a position coordinate of the catheter electrode 55 in response to the indication of electrical impedance. The calculation of the position coordinate may be based on any suitable position tracking method (e.g., as described above with reference to Figure 1 The ACL method described above) or the impedance or current distribution ratio measured between the electrode 55 and the body surface electrode 49 is used for execution.

[0091] The processing circuit 41 is configured to evaluate (block 86) the respective contact quality of each of the catheter electrodes 55 with tissue in the heart 26 in response to the indication of electrical impedance, as described above with reference to Figure 3 Described in more detail.

[0092] See now Figure 5 , the reason for which Figure 1 Schematic diagram of a first exemplary intracardiac electrogram (IEGM) trace 88 prepared by the system 20. Figure 5 Three IEGM traces 88 are shown.

[0093] Trace 88-1 represents the Figure 2 ) that has been assessed to be out of contact with the heart 26 ( Figure 1 )’s tissues in full contact.

[0094] Trace 88-2 has been highlighted using a brighter color or a different color than that used for trace 88-1. Trace 88-2 represents the electrical conduction of the catheter electrode 55 ( Figure 2 ) is performed to sense electrical activity in tissue sensed by a catheter electrode in the apparatus that has been assessed to be in adequate contact with the tissue.

[0095] Trace 88-3 has been partially highlighted (using a brighter trace than or a different color than that used for trace 88-1) in region 90 corresponding to a first time period (at which time the catheter electrode 55 sensing electrical activity represented by trace 88-3 is assessed to be in sufficient contact with tissue). After the first time period of sufficient contact, the catheter electrode 55 is not in sufficient contact with the tissue. A fading effect is used in region 92 of trace 88-3 corresponding to a second time period after the first time period. After the electrode 55 associated with trace 88-3 is no longer in sufficient contact with the tissue, a fading effect is used to dim the brightness or undo the color (for the trace 88-3 of the highlighted region 90) to restore to the original brightness and / or color (for the trace associated with the electrode not having sufficient tissue contact). The fading effect may occur within any suitable time window, such as, but not limited to, one to three seconds. The fading effect helps to eliminate brightness and / or color changes that would otherwise occur due to intermittent and / or varying contact quality.

[0096] See now Figure 6 , the reason for which Figure 1 Schematic diagram of a second exemplary intracardiac electrogram (IEGM) trace 88 prepared by the system 20. Figure 6 A trace 88 representing electrical activity sensed by approximately 42 of the catheter electrodes 55 is shown. It can be seen that, without using trace highlighting, it is easy for the physician 30 to identify the catheter electrodes 55 that are in sufficient contact with the tissue from the trace 88. Figure 1 ) would be an extremely difficult (if not impossible) task to perform. Figure 6 Four of the traces 88 (labeled 88-4) are shown as being highlighted in a brighter form and / or a different color than the other unhighlighted traces 88 for easier identification. The traces 88 may be displayed on the display 27 ( Figure 1 ), the text indicates which trace 88 corresponds to which catheter electrode 55 by using some suitable identifier for each of the catheter electrodes 55. For example, the trace 88 corresponding to the fifth catheter electrode 55 on the first of the flexible arms 54 may be labeled "A5", and the trace 88 corresponding to the first catheter electrode 55 on the third of the flexible arms 54 may be labeled "C1".

[0097] See again Figure 3 . See also Figure 1 and Figure 2 The processing circuit 41 is configured to plot (block 68) to the display 27 corresponding intracardiac electrogram (IEGM) traces 88 representing electrical activity in tissue sensed by the catheter electrodes 55 at corresponding locations in response to the signals received from the catheter 40, while modifying at least some of the traces (e.g., Figure 6 In some embodiments, the processing circuit 41 is configured to modify the traces representing electrical activity sensed by some of the catheter electrodes 55 that have a contact quality with the tissue greater than a predefined threshold contact quality (e.g., Figure 6 By way of example only, the predefined threshold contact quality may be defined relative to any one or more of: a predefined impedance, a predefined force, a predefined pressure, and / or a predefined IEGM amplitude, as described above.

[0098] In some embodiments, processing circuitry 41 is configured to modify the visual feature by increasing (block 70) the brightness of at least some of traces 88 in response to respective qualities of contact of catheter electrodes 55 with tissue of the heart at respective locations. In some embodiments, processing circuitry is configured to increase the brightness of traces representing electrical activity sensed by a first one of catheter electrodes 55 having a high quality of contact with the tissue (e.g., Figure 6 The brightness of trace 88-4).

[0099] In some embodiments, in addition to or in lieu of increasing the brightness of at least some of traces 88, processing circuitry 41 is configured to change the color of at least some of traces 88 in response to the respective quality of contact of catheter electrodes 55 with tissue of heart 26 at respective locations. In some embodiments, processing circuitry 41 is configured to change the color of traces representing electrical activity sensed by a first one of catheter electrodes 55 having a high quality of contact with the tissue (e.g., Figure 6 The color of trace 88-4) is changed (and optionally the brightness is increased).

[0100] As mentioned above Figure 5 As described, a fading effect may be used to indicate a time period after the electrode contact falls below a predefined threshold contact quality. Processing circuit 41 is configured to modify (block 72) the visual features of trace 88 for a time period after the contact quality falls below a predefined threshold contact quality. The steps of block 72 are now described in more detail.

[0101] See again Figure 5 . Processing circuit 41 ( Figure 1 ) is configured to perform, during a first time period, for example, indicating that the catheter electrode 55 ( Figure 2 ) is performed (e.g., in region 90). Processing circuitry 41 is further configured to perform, during a second time period following the first time period, a second modification or fading effect of the visual feature of trace 88-3 representing electrical activity sensed by one of catheter electrodes 55 having a contact quality with tissue less than a predefined threshold quality (e.g., in region 92). In some embodiments, the second modification or fading effect of the visual feature changes as the second time period progresses. In some embodiments, the second modification or fading effect of the visual feature includes the visual feature becoming darker as the second time period progresses (and / or the color of trace 88-3 reverts to its original color used prior to the first time period).

[0102] For the sake of clarity, various features of the present invention described in the context of independent embodiments may also be provided in combination in a single embodiment. Conversely, for the sake of simplicity, various features of the present invention described in the context of a single embodiment may also be provided individually or in any suitable sub-combination.

[0103] The above embodiments are cited by way of example, and the present invention is not limited by what is specifically shown and described above. On the contrary, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which should occur to those skilled in the art when reading the above description, and which are not disclosed in the prior art.

Claims

1. A medical system comprising: a catheter configured to be inserted into a chamber of a heart of a living subject and comprising catheter electrodes configured to contact tissue at corresponding locations within the chamber of the heart; monitor; and a processing circuit configured to receive a signal from the catheter and in response to the signal: assessing a respective quality of contact of each of the catheter electrodes with the tissue in the heart; and plotting to the display respective intracardiac electrogram (IEGM) traces representing electrical activity in the tissue sensed by the catheter electrode at the respective locations while modifying visual characteristics of at least some of the traces in response to the respective quality of contact of the catheter electrode with the tissue of the heart at the respective locations; wherein the processing circuit is configured to modify the visual features of the at least some traces representing the electrical activity sensed by some of the catheter electrodes having a contact quality with the tissue greater than a predefined threshold contact quality, and wherein the processing circuit is configured to: performing a first modification of the visual characteristic of one of the traces representative of the electrical activity sensed by one of the catheter electrodes having a contact quality with the tissue greater than the predefined threshold contact quality during a first time period; and performing a second modification of the visual characteristic of the one trace representing the electrical activity sensed by the one catheter electrode having a contact quality with the tissue less than the predefined threshold contact quality during a second time period after the first time period, wherein the second modification of the visual feature changes over the second time period, The second time period lasts from one to three seconds.

2. The system of claim 1 , wherein the processing circuit is configured to increase the brightness of at least some of the traces in response to the respective quality of contact of the catheter electrode with the tissue of the heart at the respective locations.

3. The system of claim 2 , wherein the processing circuit is configured to increase the brightness of the trace representing the electrical activity sensed by a first one of the catheter electrodes having a high contact quality with the tissue relative to the trace representing the electrical activity sensed by a second one of the catheter electrodes having a lower contact quality with the tissue.

4. The system of claim 1 , wherein the processing circuit is configured to change a color of at least some of the traces in response to the respective qualities of contact of the catheter electrode with the tissue of the heart at the respective locations.

5. The system of claim 4 , wherein the processing circuit is configured to change the color of the trace representing the electrical activity sensed by a first one of the catheter electrodes having a high contact quality with the tissue relative to the trace representing the electrical activity sensed by a second one of the catheter electrodes having a lower contact quality with the tissue.

6. The system of claim 1, wherein the second modification of the visual feature comprises dimming of the visual feature over the second time period.

7. The system of claim 1 , further comprising a body surface electrode configured to be applied to a skin surface of the living subject, wherein the processing circuit is configured to: measure an indication of an electrical impedance between the body surface electrode and the catheter electrode; and calculate a position coordinate of the catheter electrode in response to the indication of the electrical impedance.

8. The system of claim 7, wherein the processing circuit is configured to assess the respective quality of contact of each of the catheter electrodes with the tissue in the heart in response to the indication of the electrical impedance.

9. A software product comprising a non-transitory computer-readable medium having program instructions stored therein, the instructions, when read by a central processing unit (CPU), causing the central processing unit (CPU) to: receiving a signal from a catheter configured to be inserted into a chamber of a heart of a living subject and comprising catheter electrodes configured to contact tissue at corresponding locations within the chamber of the heart; In response to the signal, assessing a respective quality of contact of each of the catheter electrodes with the tissue in the heart; and plotting to a display respective intracardiac electrogram (IEGM) traces representing electrical activity in the tissue sensed by the catheter electrode at the respective locations, while modifying visual characteristics of at least some of the traces in response to the respective quality of contact of the catheter electrode with the tissue of the heart at the respective locations; the instructions, when read by the central processing unit (CPU), causing the central processing unit (CPU) to increase the brightness of a trace representing the electrical activity sensed by a first one of the catheter electrodes having a high quality of contact with the tissue relative to a trace representing the electrical activity sensed by a second one of the catheter electrodes having a lower quality of contact with the tissue, wherein the instructions further cause the central processing unit (CPU) to modify the visual features of the at least some traces representing the electrical activity sensed by some of the catheter electrodes having a contact quality with the tissue greater than a predefined threshold contact quality; performing a first modification of the visual characteristic of one of the traces representative of the electrical activity sensed by one of the catheter electrodes having a contact quality with the tissue greater than the predefined threshold contact quality during a first time period; performing a second modification of the visual feature of the one trace representing the electrical activity sensed by the one catheter electrode having a contact quality with the tissue less than the predefined threshold contact quality during a second time period after the first time period; and wherein the second modification of the visual feature changes over the second time period, The second time period lasts from one to three seconds.

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