Patent Description:
A wide range of medical procedures involve placing probes, such as catheters, within a patient's body. Location sensing systems have been developed for tracking such probes. Magnetic location sensing is one of the methods known in the art. In magnetic location sensing, magnetic field generators are typically placed at known locations external to the patient. A magnetic field sensor within the distal end of the probe generates electrical signals in response to these magnetic fields, which are processed to determine the coordinate locations of the distal end of the probe. These methods and systems are described in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, in <CIT>, and in <CIT> and <CIT> and <CIT>. Locations may also be tracked using impedance or current based systems.

One medical procedure in which these types of probes or catheters have proved extremely useful is in the treatment of cardiac arrhythmias. Cardiac arrhythmias and atrial fibrillation in particular, persist as common and dangerous medical ailments, especially in the aging population.

Diagnosis and treatment of cardiac arrhythmias include mapping the electrical properties of heart tissue, especially the endocardium and the heart volume, and selectively ablating cardiac tissue by application of energy. Such ablation can cease or modify the propagation of unwanted electrical signals from one portion of the heart to another. The ablation process destroys the unwanted electrical pathways by formation of non-conducting lesions. Various energy delivery modalities have been disclosed for forming lesions, and include use of microwave, laser, pulsed field, and more commonly, radiofrequency energies to create conduction blocks along the cardiac tissue wall. In a two-step procedure, mapping followed by ablation, electrical activity at points within the heart is typically sensed and measured by advancing a catheter containing one or more electrical sensors into the heart, and acquiring data at a multiplicity of points. These data are then utilized to select the endocardial target areas at which the ablation is to be performed.

Electrode catheters have been in common use in medical practice for many years, see for example <CIT>. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity. In use, the electrode catheter is inserted into a major vein or artery, e.g., femoral vein, and then guided into the chamber of the heart of concern. A typical ablation procedure involves the insertion of a catheter having a one or more electrodes at its distal end into a heart chamber. A reference electrode may be provided, generally taped to the skin of the patient or by means of a second catheter that is positioned in or near the heart. RF (radio frequency) current is applied between the tip electrode(s) of the ablating catheter, and the reference electrode, flowing through the media between the electrodes it, i.e., blood and tissue. The distribution of current depends on the amount of electrode surface in contact with the tissue as compared to blood, which has a higher conductivity than the tissue. Heating of the tissue occurs due to its electrical resistance. The tissue is heated sufficiently to cause cellular destruction in the cardiac tissue resulting in formation of a lesion within the cardiac tissue which is electrically non-conductive.

Therefore, when placing an ablation or other catheter within the body, particularly near the endocardial tissue, it is desirable to have the distal tip of the catheter in direct contact with the tissue. The contact can be verified, for example, by measuring the contact between the distal tip and the body tissue. <CIT>, <CIT> and <CIT> describe methods of sensing contact pressure between the distal tip of a catheter and tissue in a body cavity using a force sensor embedded in the catheter.

A number of references have reported methods to determine electrode-tissue contact, including <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; <CIT>; and <CIT>. A number of these references, e.g., <CIT>,<CIT>, and<CIT> determine electrode-tissue contact by measuring the impedance between the tip electrode and a return electrode. As disclosed in the '<NUM> patent, it is generally known than impedance through blood is generally lower that impedance through tissue. Accordingly, tissue contact has been detected by comparing the impedance values across a set of electrodes to premeasured impedance values when an electrode is known to be in contact with tissue and when it is known to be in contact only with blood. <CIT> describes a medical system, including a catheter configured to be inserted into a chamber of a heart of a living subject, and including catheter electrodes configured to contact tissue at respective locations within the chamber of the heart, and processing circuitry configured to receive signals from the catheter. In an embodiment, the system includes body-surface electrodes configured to be applied to a skin surface of the living subject and the processing circuitry is configured to measure an indication of electrical impedances between the body-surface electrodes and the catheter electrodes, and compute position coordinates of the catheter electrodes responsively to the indication of the electrical impedances.

describes using machine learning to determine catheter electrode contact. The '<NUM> Patent describes cardiac catheterization being carried out by memorizing a designation of a contact state between an electrode of the probe and the heart wall as an in-contact state or an out-of-contact state, and making a series of determinations of an impedance phase angle of an electrical current passing through the electrode and another electrode, identifying maximum and minimum phase angles in the series, and defining a binary classifier adaptively as midway between the extremes. A test value is compared to the classifier as adjusted by a hysteresis factor, and a change in the contact state is reported when the test value exceeds or falls below the adjusted classifier.

<CIT> of Mest describes a method for the in vivo re-calibration of a force sensing probe such as an electrophysiology catheter which provides for the generation of an auto zero zone. The distal tip of the catheter or other probe is placed in a body cavity within the patient. Verification that there is no tissue contact is made using electrocardiogram (ECG) or impedance data, fluoroscopy or other real-time imaging data and/or an anatomical mapping system. Once verification that there is no tissue contact made, the system recalibrates the signal emanating from the force sensor setting it to correspond to a force reading of zero grams and this recalibrated baseline reading is used to generate and display force readings based on force sensor data.

The present invention provides medical systems and methods in accordance with the appended claims. There is provided in accordance with an embodiment of the present disclosure, a medical system, including a catheter configured to be inserted into a chamber of a heart of a living subject, and including a distal end including catheter electrodes configured to contact tissue at respective locations within the chamber of the heart, at least one position sensor configured to provide at least one position signal indicative of a position of the distal end, a display, and processing circuitry configured to compute the position of the distal end of the catheter responsively to the at least one position signal, render to the display a three-dimensional (3D) anatomical map of the chamber of the heart and a 3D representation of the distal end of the catheter, and render to the display over at least part of the anatomical map, at least one intracardiac electrogram (IEGM) trace representing electrical activity in the tissue that is sensed by at least one of the catheter electrodes.

Further in accordance with an embodiment of the present disclosure the processing circuitry is configured to render to the display over at least part of the anatomical map, multiple IEGM traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes.

Still further in accordance with an embodiment of the present disclosure the processing circuitry is configured to receive signals from the catheter, and in response to the signals assess a respective quality of contact of each of at least a sub-set of the catheter electrodes with the tissue, and render to the display multiple IEGM traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective quality of contact of each of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations.

Additionally in accordance with an embodiment of the present disclosure the processing circuitry is configured to render to the display the multiple IEGM traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective quality of contact of each of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations exceeding a threshold quality of contact.

Moreover in accordance with the medical system of the present invention the processing circuitry is configured to render to the display the multiple IEGM traces representing electrical activity in the tissue that is sensed by n respective ones of the catheter electrodes responsively to the respective quality of contact of each of the n respective ones of the catheter electrodes with the tissue of the heart being among n highest qualities of contact of the at least sub-set of the catheter electrodes.

Further in accordance with an embodiment of the present disclosure the processing circuitry is configured to receive a user input selecting the sub-set of the catheter electrodes.

Still further in accordance with an embodiment of the present disclosure the processing circuitry is configured to receive a user input selecting a region of the anatomical map, and render to the display the multiple IEGM traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective ones of the catheter electrodes being located in proximity to the selected region of the anatomical map, and the respective quality of contact of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations.

Additionally in accordance with an embodiment of the present disclosure the processing circuitry configured to move a position of the at least one IEGM trace rendered on the display to follow the movement in the position of the distal end of the catheter.

Moreover in accordance with an embodiment of the present disclosure the processing circuitry configured to execute a first software program configured to compute the position of the distal end of the catheter responsively to the at least one position signal, and render to the display the anatomical map of the chamber of the heart and the representation of the distal end of the catheter, and output data indicative of the at least one IEGM trace representing electrical activity in the tissue that is sensed by the at least one of the catheter electrodes, and a second software program configured to receive the data output by the first software program, and render to the display over the at least part of the anatomical map, the at least one IEGM.

Further in accordance with an embodiment of the present disclosure the processing circuitry is configured to render the at least one IEGM trace as a progressing IEGM trace representing current electrical activity in the tissue.

Still further in accordance with an embodiment of the present disclosure the processing circuitry is configured to render the at least one IEGM trace as a static IEGM trace representing recorded electrical activity in the tissue.

Additionally in accordance with an embodiment of the present disclosure the processing circuitry is configured to render the at least one IEGM trace as a progressing IEGM trace representing recorded electrical activity in the tissue.

Moreover, in accordance with an embodiment of the present disclosure the processing circuitry is configured to receive a user input selecting a point on the anatomical map, and render to the display the at least one IEGM trace responsively to the user input.

There is also provided in accordance with another embodiment of the present disclosure, a medical system, including a catheter configured to be inserted into a chamber of a heart of a living subject, and including a distal end including catheter electrodes configured to contact tissue at respective locations within the chamber of the heart, at least one position sensor configured to provide at least one position signal indicative of a position of the distal end, a display, and processing circuitry configured to compute the position of the distal end of the catheter responsively to the at least one position signal, assess a respective quality of contact of each of at least a sub-set of the catheter electrodes with the tissue, render to the display a three-dimensional (3D) anatomical map of the chamber of the heart and a 3D representation of the distal end of the catheter, and render to the display multiple intracardiac electrogram (IEGM) traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective quality of contact of each of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations.

Further in accordance with a non-claimed embodiment of the present disclosure the processing circuitry is configured to render to the display the multiple IEGM traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective quality of contact of each of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations exceeding a threshold quality of contact.

Still further in accordance with an embodiment of the present disclosure the processing circuitry is configured to render to the display the multiple IEGM traces representing electrical activity in the tissue that is sensed by n respective ones of the catheter electrodes responsively to the respective quality of contact of each of the n respective ones of the catheter electrodes with the tissue of the heart being among n highest qualities of contact of the at least sub-set of the catheter electrodes.

Additionally in accordance with an embodiment of the present disclosure the processing circuitry is configured to receive a user input selecting the sub-set of the catheter electrodes.

Moreover in accordance with an embodiment of the present disclosure the processing circuitry is configured to receive a user input selecting a region of the anatomical map, and render to the display the multiple IEGM traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective ones of the catheter electrodes being located in proximity to the selected region of the anatomical map, and the respective quality of contact of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations.

There is also provided in accordance with still another embodiment of the present disclosure, a medical method, including providing at least one position signal indicative of a position of a distal end of a catheter inserted into a chamber of a heart of a living subject, computing the position of the distal end of the catheter responsively to the at least one position signal, rendering to a display a three-dimensional (3D) anatomical map of the chamber of the heart and a 3D representation of the distal end of the catheter, and rendering to the display over at least part of the anatomical map, at least one intracardiac electrogram (IEGM) trace representing electrical activity in tissue of the chamber that is sensed by at least one catheter electrode of the catheter.

There is also provided in accordance with still another embodiment of the present disclosure, a medical method, including providing at least one position signal indicative of a position of a distal end of a catheter inserted into a chamber of a heart of a living subject, computing the position of the distal end of the catheter responsively to the at least one position signal, assessing a respective quality of contact of each of at least a sub-set of catheter electrodes of the catheter with tissue of the chamber, rendering to a display a three-dimensional (3D) anatomical map of the chamber of the heart and a 3D representation of the distal end of the catheter, and rendering to the display multiple intracardiac electrogram (IEGM) traces representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes responsively to the respective quality of contact of each of the respective ones of the catheter electrodes with the tissue of the heart at respective locations.

As mentioned previously, in a two-step procedure, mapping followed by ablation, electrical activity at points within the heart is typically sensed and measured by advancing a catheter containing one or more electrodes into the heart, and acquiring data at a multiplicity of points. These data are then utilized to select the target areas at which the ablation is to be performed.

In particular, the electrical activity is typically displayed as intracardial electrogram (IEGM) traces for analysis by a physician in order to find sources of arrhythmia. A catheter electrode, which is not in contact with tissue in the heart, generally measures some electrical signal from the heart tissue and a far field signal. When the catheter electrode is in contact with the heart tissue, the amplitude of the signal is mainly based on tissue conductivity, while the far field is minor. Therefore, the physician is generally interested in analyzing the IEGM traces of electrodes in contact with the tissue.

For focal catheters with one or two electrodes, a single IEGM trace is typically displayed for a physician to analyze. A physician can quickly determine based on the form of the signal whether the catheter electrode providing the signal is in contact with the tissue. However, multi-electrode catheters simultaneously capturing electrical activity from different tissue locations may provide data for a plurality of IEGM traces to be displayed at the same time on a single display. In some cases, the number of IEGM traces may be too numerous for the physician to easily determine which of the IEGM traces are provided by electrodes in contact with the tissue, and which are not.

An example of a multielectrode catheter is the Octaray® catheter, with in excess of <NUM> electrodes, produced by Biosense Webster Inc. , of Irvine, CA, USA. The Octaray includes eight deflectable arms disposed at the distal end of a shaft, with each of the deflectable arms including six electrodes. Details of such catheter can be found in <CIT>. Some catheters may include more electrodes, for example, but not limited to, <NUM> electrodes.

In addition to the need to determine electrode contact during mapping discussed above, the physician performing an ablation procedure monitors the contact of electrodes with tissue as effective ablation generally requires sufficient contact between the ablation electrode(s) and the tissue. Recently, ultra-fast ablation treatment technologies such as irreversible electroporation (IRE) have been introduced into the market. The speed as well as the ease at which the treatment may be executed may be improved by helping the physician focus on the clinically relevant input during the procedure.

Embodiments of the present invention solve at least some of the above problems during a medical procedure such as a mapping or ablation procedure, by presenting a physician with one or more IEGM traces (e.g., voltage versus time graphs) of signals acquired by electrodes of a catheter, overlaying the representation of the catheter and anatomical map so that the IEGM trace(s) are visible in the region of the screen where the physician is generally concentrating. In some embodiments, the IEGM trace(s) may move on the screen to follow movement of the catheter to allow the IEGM trace(s) to stay in the region of the screen where the physician is now concentrating.

In some embodiments, a main mapping software application may process signals provided by the catheter and body surface electrodes and provide other mapping functions such a generating and rendering the anatomical map and the representation of the catheter to a display. A secondary software application may receive data (for example, a position of the distal end of the catheter on the display, and IEGMs captured by the catheter electrodes) from the main mapping software application. The secondary software application may then display the IEGMs overlaying the anatomical map, typically centered around the distal end of the catheter. In this manner, the main mapping software application does not need to be changed, or undergoes minor changes, while other functionality is provided by the secondary software application. In other embodiments, the functionality provided herein may be implemented with a single software application.

In some embodiments, instead of showing all the IEGM traces of signals acquired by all the electrodes of the catheter, the number of IEGM traces displayed may be reduced to select one or more of the IEGM traces more relevant to the physician.

In some embodiments, the IEGM traces selected for display may be captured by groups of electrodes selected by the physician. For example, the physician may be more interested in certain groups of electrodes, such as electrodes at the distal tip of the catheter or electrodes around an equator of a basket or balloon distal end of the catheter. In some embodiments, the IEGM traces selected for display may be those electrodes in sufficient contact with tissue of a given region of the heart. The region of the heart may be a named region, which is selected by the physician (e.g., pulmonary vein, right atrium, left atrium, right ventricle, left ventricle), or a region selected on the anatomical map using a pointing device such as a mouse, stylus, or a finger.

Additionally, or alternatively, the number of IEGM traces displayed may be limited based on a quality of contact of the respective electrodes with tissue of the heart. For example, IEGM traces of electrodes having a sufficient quality of contact greater than a threshold quality of contact may be displayed, or the IEGM traces of the n electrodes having the highest quality of contact among the electrodes may be displayed.

In the above discussion, sufficiency of tissue contact is used to decide whether or not to display the IEGM traces. A quality of contact may be assessed based on different methods including impedance measurements, force or pressure measurements, or from analysis of IEGM traces, as will now be described in more detail.

The displayed may be current IEGM traces being currently captured by the electrodes or recorded IEGM traces which may be displayed as progressing IEGMs (in which different time windows of electrical activity of the tissue is shown over time) or static IEGMs (in which one or more time-windows of electrical activity of the tissue is shown without changing the IEGM data being displayed).

In response to signals provided by the catheter, processing circuitry assesses the respective quality of contact of each of the catheter electrodes with the tissue in the heart. Any one of the catheter electrodes may be in full or partial contact with the tissue of the heart. In some cases, any one 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 one of the catheter electrodes with the tissue may be assessed based on the signals provided by the catheter.

The term "quality of contact" as used in the specification and claims is defined herein as a quantitative indicator of the degree of contact between one of the catheter electrodes and the tissue. The "quality of contact" may be expressed directly, for example in terms a measured electrical impedance, or indirectly, for example in terms of contact force, pressure or IEGM amplitude, as will now be described below in more detail. In some embodiments, the "quality of contact" may be expressed as a measurement from the respective electrode to the tissue based on computing the position of the electrode as located in the generated anatomical map and the known location of the tissue given by the generated anatomical map.

In some embodiments, the catheter may provide signals which provide an indication of impedance between the catheter electrodes and body surface electrodes. The indication of the impedance provides an indication of a quality of contact, such that a higher value of impedance between one of the catheter electrodes and the body surface electrodes indicates a higher quality of contact between that catheter electrode and the tissue. A value of impedance may be selected to define a minimum quality of contact considered to represent sufficient contact between any one of the catheter electrodes and the tissue.

In some embodiments, the impedance between one of the catheter electrodes and another one of the electrodes on the catheter may be used as a measure of quality of contact. As disclosed in the '<NUM> patent mentioned in the background section above, it is generally known that impedance through blood is generally lower than impedance through tissue. Accordingly, tissue contact may be assessed by comparing impedance values across a set of electrodes to premeasured impedance values when an electrode is known to be in sufficient contact with tissue and when it is known to be in contact only with blood.

In some embodiments, the method of <CIT> to Gliner, at al. may be used to assess quality of contact using a machine learning based method.

In some embodiments, the catheter may provide signals from force or pressure sensors. The indication of force or pressure provides an indication of a quality of contact, such that a higher value of force or pressure indicates a higher quality of contact between a catheter electrode and the tissue. A value of force or pressure may be selected to define a minimum quality of contact considered to represent sufficient contact between any one of the catheter electrodes and the tissue.

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

Reference is now made to <FIG>, which is a schematic, pictorial illustration of a catheter tracking system <NUM>, in accordance with an embodiment of the present invention. The system <NUM> includes a catheter <NUM> configured to be inserted into a body part (e.g., a chamber of a heart <NUM>) of a living subject (e.g., a patient <NUM>) seen in detail in inset <NUM>. A physician <NUM> navigates the catheter <NUM> (for example, a basket catheter produced by Biosense Webster, Inc. of Irvine, CA, USA), seen in detail in inset <NUM>, to a target location in the heart <NUM> of the patient <NUM>, by manipulating a deflectable segment of an insertion tube <NUM> of the catheter <NUM>, using a manipulator <NUM> near a proximal end <NUM> of the insertion tube <NUM>, and/or deflection from a sheath <NUM>. In the pictured embodiment, physician <NUM> uses catheter <NUM> to perform anatomical mapping of a cardiac chamber.

The catheter <NUM> includes a distal end <NUM>. The distal end <NUM> of the catheter <NUM> includes an assembly <NUM> (e.g., a basket assembly as shown in <FIG> or a balloon assembly or any suitable distal end assembly, e.g., grid, flexible splines or a focal catheter) on which at least one (e.g., multiple) catheter electrode(s) <NUM> (only some labeled for the sake of simplicity) are disposed. The electrodes <NUM> are configured to contact tissue at respective locations with the chamber of the heart. The assembly <NUM> is disposed distally to the insertion tube <NUM> and may be connected to the insertion tube <NUM> via a coupling member of the insertion tube <NUM> at the distal end <NUM>. The coupling member of the insertion tube <NUM> may be formed as an integral part of the rest of the insertion tube <NUM> or as a separate element which connects with the rest of the insertion tube <NUM>.

The assembly <NUM> further comprises multiple flexible strips <NUM> (only two labeled for the sake of simplicity), to each of which are coupled the electrodes <NUM>. The assembly <NUM> may include any suitable number of electrodes <NUM>. In some embodiments, the assembly <NUM> may include ten flexible strips <NUM> and <NUM> electrodes, with twelve electrodes disposed on each flexible strip <NUM>.

The catheter <NUM> includes a pusher <NUM>. The pusher <NUM> is typically a tube that is disposed in a lumen of the insertion tube <NUM> and spans from the proximal end <NUM> to the distal end <NUM> of the insertion tube <NUM>. A distal end of the pusher <NUM> is connected to distal ends of the flexible strips <NUM>, typically via a coupling member of the pusher <NUM>. The coupling member of the pusher <NUM> may be formed as an integral part of the rest of the pusher <NUM> or as a separate element which connects with the rest of the pusher <NUM>. The distal end of the insertion tube <NUM> is connected to proximal ends of the flexible strips <NUM>, typically via the coupling member of the distal end <NUM>. The pusher <NUM> is generally controlled via the manipulator <NUM> to deploy the assembly <NUM> and change an ellipticity of the assembly <NUM> according to the longitudinal displacement of the pusher <NUM> with respect to the insertion tube <NUM>. The actual basket assembly <NUM> structure may vary. For example, flexible strips <NUM> may be made of a printed circuit board (PCB), or of a shape-memory alloy, or any suitable material.

Embodiments described herein refer mainly to a basket distal-end assembly <NUM>, purely by way of example. In alternative embodiments, the disclosed techniques can be used with a catheter having a balloon-based distal-end assembly or of any other suitable type of distal-end assembly.

Catheter <NUM> is inserted in a folded configuration, through sheath <NUM>, and only after the catheter <NUM> exits sheath <NUM> is catheter <NUM> able to change shape by retracting pusher <NUM>. By containing catheter <NUM> in a folded configuration, sheath <NUM> also serves to minimize vascular trauma on its way to the target location.

The distal end <NUM> of the catheter <NUM> comprises magnetic coil sensors 50A and 50B. The magnetic coil sensor 50A is shown in inset <NUM> at the distal edge of insertion tube <NUM> (i.e., at the proximal edge of basket assembly <NUM>). The sensor 50A may be a Single-Axis Sensor (SAS), or a Double-Axis Sensor (DAS) or a Triple-Axis Sensor (TAS). Similarly, the sensor 50B may be a SAS, DAS, or TAS. Magnetic coil sensors 50A and 50B and electrodes <NUM> are connected by wires running through insertion tube <NUM> to various driver circuitries in a console <NUM>.

In some embodiments, system <NUM> comprises a magnetic-sensing subsystem to estimate an ellipticity of the basket assembly <NUM> of catheter <NUM>, as well as its elongation/retraction state, inside a cardiac chamber of heart <NUM> by estimating the elongation of the basket assembly <NUM> from the distance between sensors 50A and 50B. Patient <NUM> is placed in a magnetic field generated by a pad containing multiple magnetic field generator coils <NUM>, which are driven by a unit <NUM>. The magnetic field generator coils <NUM> are configured to generate respective alternating magnetic fields, having respective different frequencies, into a region where a body-part (e.g., the heart <NUM>) of a living subject (e.g., the patient <NUM>) is located. The magnetic coil sensors 50A and 50B are configured to output electrical signals responsively to detecting the respective magnetic fields. For example, if there are nine magnetic field generator coils <NUM> generating nine respective different alternating magnetic fields with nine respective different frequencies, the electrical signals output by the magnetic coil sensors <NUM> will include components of the nine different frequency alternating magnetic fields. The magnitude of each of the magnetic fields varies with distance from the respective magnetic field generator coils <NUM> such that the location of the magnetic coil sensors <NUM> may be determined from the magnetic fields sensed by the magnetic coil sensors <NUM>. Therefore, the transmitted alternating magnetic fields generate the electrical signals in sensors 50A and 50B, so that the electrical signals are indicative of position and orientation of the magnetic coil sensors <NUM> in the heart chamber.

The generated signals are transmitted to console <NUM> and become corresponding electrical inputs to processing circuitry <NUM>. The processing circuitry <NUM> may use the signals to compute: the elongation of the basket assembly <NUM>, in order to estimate basket ellipticity and elongation/retraction state from the calculated distance between sensors 50A and 50B; and compute a relative orientation between the axes of the sensors 50A and 50B to estimate a shape of the expandable distal end assembly <NUM> (e.g., a basket shape) responsively to the relative orientation, as described in more detail below.

The bow of the flexible strips <NUM> and/or the positions of the electrodes <NUM> (or other features) on the flexible strips <NUM> with respect to a fixed point on the catheter <NUM> (such as the distal tip of the insertion tube <NUM>) may be measured for various distances between the magnetic sensors 50A, 50B and for various relative orientation angles between the magnetic sensors 50A, 50B. For example, the positions of the electrodes <NUM> with respect to the fixed point on the catheter <NUM> may be measured for every <NUM> movement of the pusher <NUM> with respect to the insertion tube <NUM> and for every <NUM> degree of relative orientation between the magnetic sensors 50A, 50B (up to a maximum sideways movement of the assembly <NUM>). At each different distance/relative-orientation combination, the computed distance and computed relative orientation angle between the magnetic sensors 50A, 50B is recorded along with the position data of the electrodes <NUM>. This data may then be used to estimate the bow of the flexible strips <NUM> and/or the positions of the electrodes <NUM> (or other features) on the flexible strips <NUM> with respect to a fixed point on the catheter <NUM> (such as the distal tip of the insertion tube <NUM>) responsively to the computed distance and relative orientation angle between the magnetic sensors 50A, 50B.

Additionally, or alternatively, the bow of the flexible strips <NUM> may be estimated based on the following assumptions: (a) each of the flexible strips <NUM> is of a fixed and known length; (b) each of the flexible strips <NUM> is connected to the pusher <NUM> via a coupler, with the distal ends of the flexible strips <NUM> being substantially perpendicular (within an error of plus or minus <NUM> degrees) to the longitudinal axis of the insertion tube <NUM>; (c) each of the flexible strips <NUM> is connected to the insertion tube <NUM> via a coupler, which couples the proximal ends of the flexible strips <NUM> to the insertion tube <NUM>, substantially parallel (within an error of plus or minus <NUM> degrees) to the longitudinal axis of the insertion tube <NUM>. Based on the above assumptions (a)-(c), and the computed positions of the couplers based on the computed positions of the magnetic sensors 50A, 50B, the bow of each of the flexible strips <NUM> may be computed using a third-degree polynomial. In some embodiments, the bow of the flexible strips <NUM> and/or the positions of the electrodes <NUM> (or other features) on the flexible strips <NUM> with respect to a fixed point on the catheter <NUM> (such as the distal tip of the insertion tube <NUM>) may be computed based on the computed distance and orientation between the magnetic sensors 50A, 50B and a model of the catheter <NUM> which provides the bow of the flexible strips <NUM> and/or the positions of the electrodes <NUM> for the computed distance based on the mechanical properties and dimensions of the flexible strips <NUM>.

A method of position and/or direction sensing using external magnetic fields and magnetic coil sensors, such as sensors 50A and 50B, is implemented in various medical applications, for example, in the CARTO® system, produced by Biosense-Webster, and is described in detail in <CIT>, <CIT>, <CIT>, <CIT>,<CIT>and <CIT>, in <CIT>, and in <CIT>, <CIT> and <CIT>.

In some embodiments, the processing circuitry <NUM> uses position-signals received from the electrodes <NUM> or body surface electrodes <NUM>, and the magnetic sensor <NUM> to estimate a position or orientation of the assembly <NUM> inside a body part, such as inside a cardiac chamber. In some embodiments, the processing circuitry <NUM> correlates the position signals received from the electrodes <NUM>, <NUM> with previously acquired magnetic location-calibrated position signals, to estimate the position of the assembly <NUM> inside the body part. The position coordinates of the electrodes <NUM> may be determined by the processing circuitry <NUM> based on, among other inputs, measured impedances, voltages or on proportions of currents distribution, between the electrodes <NUM> and the body surface electrodes <NUM>.

The method of position sensing using current distribution measurements and/or external magnetic fields is implemented in various medical applications, for example, in the Carto® system, produced by Biosense Webster Inc. (Irvine, California), and is described in detail in <CIT>,<CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, <CIT>, and <CIT>, in <CIT>, and in <CIT>, <CIT> and <CIT>.

The Carto®<NUM> system applies Active Current Location (ACL) which is a hybrid current-distribution and magnetic-based position-tracking technology. In some embodiments, using ACL, the processing circuitry <NUM> estimates the positions of the electrodes <NUM>. In some embodiments, the signals received from the electrodes <NUM>, <NUM> are correlated with a current-to-position matrix (CPM) which maps current distribution ratios (or another electrical value) with a position that was previously acquired from magnetic location-calibrated position signals. The current distribution ratios are based on measurements of the body surface electrodes <NUM> of current flowing from the electrodes <NUM> to the body surface electrodes <NUM>.

In some embodiments, to visualize catheters which do not include a magnetic sensor, the processing circuitry <NUM> may apply an electrical signal-based method, referred to as Independent Current Location (ICL) technology. In ICL, the processing circuitry <NUM> calculates a local scaling factor for each voxel of the volume in which catheters are visualized. The factor is determined using a catheter with multiple electrodes having a known spatial relationship, such as a lasso-shaped catheter. However, although yielding accurate local scaling (e.g., over several millimeters), ICL is less accurate when applied to a volume of a whole heart chamber, whose size is in the order of centimeters. The ICL method, in which positions are calculated based on current distribution proportions can have errors and may yield a distorted shape of the assembly <NUM>, due to the non-linear nature of the current-based ICL space. In some embodiments, the processing circuitry <NUM> may apply the disclosed ICL method to scale ICL space and the assembly <NUM> shape into a correct one, based on known smaller scale distances between electrodes of a lasso-shaped catheter, for example, as well as based on larger scale distances, themselves based on the known distance between the electrodes <NUM> at the ends of the assembly <NUM>.

Processing circuitry <NUM>, typically part of a general-purpose computer, is further connected via a suitable front end and interface circuits <NUM>, to receive signals from body surface-electrodes <NUM>. Processing circuitry <NUM> is connected to surface-electrodes <NUM> by wires running through a cable <NUM> to the chest of patient <NUM>. The catheter <NUM> includes a connector <NUM> disposed at the proximal end <NUM> of the insertion tube <NUM> for coupling to the processing circuitry <NUM>.

In some embodiments, processing circuitry <NUM> renders to a display <NUM>, a representation <NUM> of at least a part of the catheter <NUM> and an anatomical map or body-part, (e.g., from a mapping process or from a scan (e.g., CT or MRI) of the body-part previously registered with the system <NUM>), responsively to computed position coordinates of the insertion tube <NUM> and the flexible strips <NUM>.

Processing circuitry <NUM> is typically programmed in software to carry out 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 non-transitory tangible media, such as magnetic, optical, or electronic memory. The system <NUM> may also include a memory <NUM> used by the processing circuitry <NUM>.

The example illustration shown in <FIG> is chosen purely for the sake of conceptual clarity. <FIG> shows only elements related to the disclosed techniques for the sake of simplicity and clarity. System <NUM> typically comprises additional modules and elements that are not directly related to the disclosed techniques, and thus are intentionally omitted from <FIG> and from the corresponding description. The elements of system <NUM> and the methods described herein may be further applied, for example, to control an ablation of tissue of heart <NUM>.

Reference is now made to <FIG> and <FIG>. <FIG> is a flowchart <NUM> including steps in a first method of operation of the system <NUM> of <FIG>. <FIG> is a schematic view of a representation <NUM> of the catheter <NUM> in an anatomical map <NUM> rendered in the system <NUM> of <FIG>.

As previously described with reference to <FIG>, the position of the distal end of the catheter <NUM> inside a chamber of the heart may be found using a variety of methods, for example, based on signals provided by at least one position sensor, which may include the magnetic coil sensors <NUM> and/or the electrodes <NUM> and/or the body surface electrodes <NUM>. The position sensor(s) <NUM>, <NUM>, <NUM> are configured to provide at least one position signal indicative of a position or orientation of the distal end with reference to a 3D anatomical map of the chamber of the heart. In some embodiments, the position of the distal end of the catheter <NUM> may be found using imaging techniques such as ultrasonic scanning and suitable processing of the ultrasound images. The processing circuitry <NUM> is configured to compute the position of the distal end of the catheter <NUM> responsively to the position signal(s) provided by the position sensor(s) <NUM>, <NUM>, <NUM> (block <NUM>). That is, circuitry <NUM> computes the position of the distal end of the catheter from the at least one position signal to define the position and orientation of the distal end or electrodes of the catheter with respect to a chamber of the heart and thereby render to the display a three-dimensional (3D) anatomical map of the chamber of the heart and a 3D representation of the location and orientation of the distal end of the catheter as referenced to the 3D anatomical map. By providing the 3D anatomical map and the 3D representation of the catheter, the physician is able to identify where the position of the distal end of the catheter (and its electrodes) are located with reference to the chamber of the heart and move the distal end of the catheter within the heart to specific locations in the heart chamber by viewing the 3D representations of the heart and catheter.

The processing circuitry <NUM> is configured to render to the display <NUM> the three-dimensional (3D) anatomical map <NUM> of the chamber of the heart <NUM> and the 3D representation <NUM> of the distal end of the catheter <NUM> (block <NUM>) as positioned or orientated with respect to the 3D anatomical map. The anatomical map <NUM> may be generated using any suitable anatomical map generation method, for example, but not limited to, Fast Anatomical Mapping (FAM). FAM is described in <CIT> In FAM, a smooth shell is generated around a three-dimensional (3D) cloud of data points, such as a cloud of computed electrode positions of the electrodes <NUM> so that the position and orientation of the distal end and electrodes <NUM> with respect to the chamber of the heart can be graphically represented in the 3D anatomical map <NUM> of the heart.

In some embodiments, the processing circuitry <NUM> is configured to receive signals from the catheter <NUM>, and in response to the signals, assess a respective quality of contact of each of (at least a sub-set of) the catheter electrodes <NUM> with the tissue (block <NUM>).

Any one of the catheter electrodes <NUM> may be in full or partial contact with the tissue of the heart <NUM>. In some cases, any one of the catheter electrodes <NUM> 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 one of the catheter electrodes <NUM> with the tissue may be assessed based on the signals provided by the catheter <NUM>.

As previously mentioned, the term "quality of contact" is a quantitative indicator of the degree of (electrical) contact between one of the catheter electrodes <NUM> and the tissue. The "quality of contact" may be expressed directly, for example in terms a measured electrical impedance, or indirectly, for example in terms of contact force, pressure or IEGM amplitude, as will now be described below in more detail. The "quality of contact" may also be expressed in terms of distance from the electrodes to the tissue based on computed positions of the electrodes <NUM> and the anatomical map <NUM>.

In some embodiments, the catheter <NUM> may provide signals which provide an indication of impedance between the catheter electrodes <NUM> and the body surface electrodes <NUM>. The indication of the impedance provides an indication of a quality of contact, such that a higher value of impedance between one of the catheter electrodes <NUM> and the body surface electrodes <NUM> indicates a higher quality of contact between that catheter electrode <NUM> and the tissue. A value of impedance may be selected to define a minimum quality of contact considered to represent sufficient contact between any one of the catheter electrodes <NUM> and the tissue.

In some embodiments, the impedance between one of the catheter electrodes <NUM> and another one of the electrodes on the catheter <NUM> may be used as a measure of quality of contact. As disclosed in the '<NUM> patent mentioned in the background section above, it is generally known that impedance through blood is generally lower than impedance through tissue. Accordingly, tissue contact may be assessed by comparing impedance values across a set of electrodes to premeasured impedance values when an electrode is known to be in sufficient contact with tissue and when it is known to be in contact only with blood.

In some embodiments, the method of <CIT>. may be used to assess quality of contact. The '<NUM> Patent describes using machine learning to determine catheter electrode contact. The '<NUM> Patent describes cardiac catheterization being carried out by memorizing a designation of a contact state between an electrode of the probe and the heart wall as an in-contact state or an out-of-contact state, and making a series of determinations of an impedance phase angle of an electrical current passing through the electrode and another electrode, identifying maximum and minimum phase angles in the series, and defining a binary classifier adaptively as midway between the extremes. A test value is compared to the classifier as adjusted by a hysteresis factor, and a change in the contact state is reported when the test value exceeds or falls below the adjusted classifier.

In some embodiments, the catheter <NUM> may provide signals from force or pressure sensors (not shown), disposed at different locations on the flexible strips <NUM>, that provide an indication of force or pressure exerted by the catheter electrodes <NUM> on the tissue. The indication of force or pressure provides an indication of a quality of contact, such that a higher value of force or pressure indicates a higher quality of contact between that catheter electrode <NUM> and the tissue. A value of force or pressure may be selected to define a minimum quality of contact considered to represent sufficient contact between any one of the catheter electrodes <NUM> and the tissue. These embodiments, may use any suitable force or pressure sensors as well as any suitable method for measuring the force or pressure, including any of the Patents or Patent Publications mentioned in the background section including the method described in <CIT> of Mest and describes a method for the in vivo re-calibration of a force sensing probe such as an electrophysiology catheter which provides for the generation of an auto zero zone. The distal tip of the catheter or other probe is placed in a body cavity within the patient. Verification that there is no tissue contact is made using electrocardiogram (ECG) or impedance data, fluoroscopy or other real-time imaging data and/or an anatomical mapping system. Once verification that there is no tissue contact made, the system recalibrates the signal emanating from the force sensor setting it to correspond to a force reading of zero grams and this recalibrated baseline reading is used to generate and display force readings based on force sensor data.

In some embodiments, intracardiac electrogram (IEGM) traces generated by the processing circuitry <NUM> may be used to assess the quality of contact between any one of the catheter electrodes <NUM> and the tissue. The maximum amplitude of the IEGM trace associated with one of the catheter electrodes <NUM> is indicative of the quality of contact between that catheter electrode <NUM> and the tissue, such that a higher value of the maximum amplitude of the IEGM trace indicates a higher quality of contact between that catheter electrode <NUM> and the tissue. An amplitude value of the IEGM trace may be selected to define a minimum quality of contact considered to represent sufficient contact between any one of the catheter electrodes <NUM> and the tissue.

In some embodiments, the steps of the methods of <FIG> and <FIG> are executed via a single software program. In some embodiments, the method described with reference to <FIG> is executed by a first software program and the method described with reference to <FIG> is executed by a second software program.

In some embodiments, the processing circuitry <NUM> is configured to execute a main mapping software application <NUM> (also referred herein as a "first software program") to perform the steps of blocks <NUM>-<NUM>, while a secondary software application <NUM> (<FIG>) (also referred herein as a "second software program) may receive data (for example, a position of the distal end of the catheter <NUM> on the display <NUM>, and IEGMs of the catheter electrodes <NUM>) from the main mapping software application. The steps performed by the secondary software application are described with reference to <FIG>. In this manner, the main mapping software application does not need to be changed, or undergoes minor changes, while other functionality is provided by the secondary software application. In other embodiments, the steps described with reference to <FIG> and <FIG> may be implemented with a single software application.

Therefore, in some embodiments, the main mapping software application <NUM> running on the processing circuitry <NUM> is configured to output data indicative of the IEGM trace(s) representing electrical activity in the tissue that is sensed by the catheter electrode(s) <NUM>, and a position of the distal end of the catheter <NUM> on the display <NUM> (block <NUM>), for example using a TCP-based communication protocol.

Reference is now made to <FIG>, which is a flowchart <NUM> including steps in a second method of operation of the system <NUM> of <FIG>. Reference is also made to <FIG>.

As previously mentioned, the steps described with reference to <FIG> may be performed by the secondary software application <NUM>. Therefore, the processing circuitry <NUM> is configured to execute the secondary software application <NUM> to receive the data output by the main mapping software application <NUM> (block <NUM>), for example using a TCP-based communication protocol. In other embodiments, the steps described with reference to <FIG> and <FIG> may be implemented with a single software application.

The physician <NUM> is able to select a region of, and/or a point on, the anatomical map <NUM>, and/or a sub-set of the electrodes <NUM> as criteria in rendering one or more IEGMs to the display <NUM>, as described in more detail below with reference to <FIG>. In some embodiments, the processing circuitry <NUM> is configured to receive a user input selecting a sub-set of the catheter electrodes (block <NUM>). The sub-set may be selected from predefined sub-sets. For example, one sub-set may include electrodes at the distal tip of a basket-shaped catheter or electrodes around an equator of a basket or balloon-shaped catheter. In some embodiments, the processing circuitry <NUM> is configured to receive a user input selecting a region <NUM> of the anatomical map <NUM> (block <NUM>). The region may be selected from a predefined list of regions, such as pulmonary vein, right atrium, left atrium, right ventricle, left ventricle, or the region <NUM> may be selected by delineating the region on the anatomical map <NUM> using a pointing device such as a mouse, stylus, or finger, as shown in <FIG>. In some embodiments, the processing circuitry <NUM> is configured to receive a user input selecting a point <NUM> on the anatomical map <NUM> (block <NUM>).

Reference is now made to <FIG>, which is a schematic view of the representation <NUM> of the catheter <NUM> in the anatomical map <NUM> of <FIG> with multiple intracardiac electrograms (IEGM) traces <NUM> overlaying the map <NUM>. Reference is also made to <FIG>.

The processing circuitry <NUM> is configured to render to the display <NUM>, over at least part of the anatomical map <NUM> (and/or over at least part of the representation <NUM> of the catheter <NUM>), one or more IEGM traces <NUM> representing electrical activity in the tissue of the heart <NUM> that is sensed by one or more of the catheter electrodes <NUM> (block <NUM>). For example, if the physician <NUM> selected the point <NUM> in the step of block <NUM>, the processing circuitry <NUM> may be configured to render to the display one IEGM trace <NUM> which represents electrical activity closest to the point <NUM>. The rendered IEGM trace <NUM> may represent current electrical activity captured by one of the electrodes <NUM> at, or near, the point <NUM>, or previously captured electrical activity at, or near, the point <NUM>. Therefore, in some embodiments, the processing circuitry <NUM> is configured to render one IEGM trace <NUM> at least partially over the anatomical map <NUM> responsively to receiving the user input selecting the point <NUM> on the anatomical map <NUM>.

In some embodiments, the processing circuitry <NUM> is configured to render to the display <NUM> over at least part of the anatomical map <NUM>, multiple IEGM traces <NUM> representing electrical activity in the tissue of the heart <NUM> that is sensed by respective catheter electrodes <NUM>.

The number of IEGM traces <NUM> rendered to the display <NUM> may be dependent on the quality of contact of each electrode <NUM> or a sub-set of electrodes <NUM> (for example, the sub-set of electrodes <NUM> selected in the step of block <NUM>) so that the more relevant IEGM traces <NUM> are rendered to the display <NUM>. Therefore, in some embodiments, the processing circuitry <NUM> is configured to render to the display <NUM> (over at least part of the anatomical map <NUM>) multiple IEGM traces <NUM> representing electrical activity in the tissue that is sensed by respective catheter electrodes <NUM> responsively to the respective quality of contact of each respective catheter electrode <NUM> with the tissue of the heart at the respective locations. In some embodiments, the processing circuitry <NUM> is configured to render to the display <NUM> (over at least part of the anatomical map <NUM>) the multiple IEGM traces <NUM> representing electrical activity in the tissue that is sensed by respective catheter electrodes <NUM> responsively to the respective quality of contact of each respective catheter electrode <NUM> with the tissue of the heart at the respective locations exceeding a threshold quality of contact. In other words, the IEGM traces <NUM> of the electrodes <NUM> (or the selected sub-set of the electrodes <NUM>) having a quality of contact exceeding the threshold quality of contact are rendered to the display <NUM> over at least part of the anatomical map <NUM> by the processing circuitry <NUM>.

The number of IEGM traces <NUM> rendered to display <NUM> may be limited to n IEGM traces <NUM> so that the IEGM traces <NUM> of n corresponding electrodes <NUM> (or n electrodes <NUM> of the selected sub-set of the electrodes <NUM>) closest to the tissue (measured by the quality of contact) are rendered to the display <NUM>. Therefore, in some embodiments, the processing circuitry <NUM> is configured to render to the display <NUM> n IEGM traces <NUM> representing electrical activity in the tissue that is sensed by n respective catheter electrodes <NUM> (e.g., n electrodes <NUM> from all the electrodes <NUM> or of the selected sub-set of electrodes <NUM>) responsively to the respective quality of contact of each of the n respective catheter electrodes <NUM> with the tissue of the heart being among n highest qualities of contact of the electrodes <NUM> or the sub-set of the catheter electrodes <NUM>. The value n may be set to any suitable number by the physician <NUM>. The value n may depend on the number of electrodes <NUM> and/or the size of the display <NUM>.

In some embodiments, the IEGM traces <NUM> may be limited to the IEGM traces <NUM> captured by respective electrodes <NUM> from one or more selected regions <NUM> of the heart <NUM>. Therefore, in some embodiments, the processing circuitry <NUM> is configured to render to the display <NUM> multiple IEGM traces <NUM> representing electrical activity in the tissue that is sensed by respective catheter electrodes <NUM> responsively to: the respective catheter electrodes <NUM> being located in proximity to the selected region <NUM> of the anatomical map <NUM>; and optionally the respective quality of contact of the respective catheter electrodes <NUM> with the tissue of the heart <NUM> at the respective locations (exceeding a threshold quality of contact).

The IEGM traces <NUM> may be progressing signals (i.e., dynamically change with time) or static signals of current, or previously recorded, electrical activity captured from the tissue of the heart <NUM>. Therefore, in some embodiments, the processing circuitry <NUM> is configured to render the IEGM trace(s) <NUM> as progressing IEGM trace(s) representing current electrical activity in the tissue. In some embodiments, the processing circuitry <NUM> is configured to render the IEGM trace(s) <NUM> as static IEGM trace(s) representing recorded electrical activity in the tissue. In some embodiments, the processing circuitry <NUM> is configured to render the IEGM trace(s) <NUM> as progressing IEGM trace(s) representing recorded electrical activity in the tissue.

In some embodiments, the processing circuitry <NUM> is configured to move a position of the IEGM trace(s) <NUM> rendered on the display <NUM> to follow movement in the position of the distal end of the catheter <NUM> (block <NUM>), as provided by the step of block <NUM> of <FIG>.

More specifically, "about" or "approximately" may refer to the range of values ±<NUM>% of the recited value, e.g., "about <NUM>%" may refer to the range of values from <NUM>% to <NUM>%.

Various features of the invention which are, for clarity, described in the contexts of separate embodiments may also be provided in combination in a single embodiment, where in accordance with the scope of the appended claims. Conversely, various features of the invention which are, for brevity, described in the context of a single embodiment may also be provided separately or in any suitable sub-combination, where in accordance with the scope of the appended claims.

Claim 1:
A medical system (<NUM>), comprising:
a catheter (<NUM>) configured to be inserted into a chamber of a heart of a living subject, and including a distal end (<NUM>) comprising catheter electrodes (<NUM>) configured to contact tissue at respective locations within the chamber of the heart;
at least one position sensor (50A, 50B) configured to provide at least one position signal indicative of a position of the distal end;
a display (<NUM>); and
processing circuitry (<NUM>) configured to:
compute the position of the distal end of the catheter responsively to the at least one position signal;
assess a respective quality of contact of each of at least a sub-set of the catheter electrodes with the tissue;
render to the display a three-dimensional (3D) anatomical map of the chamber of the heart and a 3D representation of the distal end of the catheter;
select multiple intracardiac electrogram (IEGM) traces (<NUM>), representing electrical activity in the tissue that is sensed by respective ones of the catheter electrodes, to be rendered to the display, responsively to the respective quality of contact of each of the respective ones of the catheter electrodes with the tissue of the heart at the respective locations; and
render to the display the selected multiple intracardiac electrogram (IEGM) traces (<NUM>),
wherein the processing circuitry is configured to select the multiple IEGM traces representing electrical activity in the tissue that is sensed by n respective ones of the catheter electrodes responsively to the respective quality of contact of each of the n respective ones of the catheter electrodes with the tissue of the heart being among n highest qualities of contact of the at least sub-set of the catheter electrodes.