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 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. 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 artery, 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 to the tip electrode(s) of the ablating catheter, and current flows through the media that surrounds it, i.e., blood and tissue, toward the reference electrode. 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 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>, 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 electro-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.

<CIT> discusses how the signal quality of an electrophysiological signal can be determined from information regarding proximal stability of an electrophysiology catheter at the time the signal is acquired and temporal stability of the electrophysiological signal. The proximal stability information can include a distance between the electrophysiology catheter and an anatomical surface, a velocity of the electrophysiology catheter, and/or contact force between the electrophysiology catheter and the anatomical surface. Graphical representations of signal quality scores can be output to a display in order to enable visualization thereof by a practitioner.

<CIT> discusses a neurofeedback system that comprises an electrode for contacting skin of a user for measuring a biofeedback signal of the user, a first signal processing unit for determining a signal characteristic of the measured biofeedback signal, wherein the signal characteristic represents a neurofeedback, a second signal processing unit for determining a biofeedback signal quality of the measured biofeedback signal by extracting a signal feature of the measured biofeedback signal and calculating a probability of a measurement error for said signal feature, which probability represents the biofeedback signal quality, and a feedback unit for providing feedback to the user, wherein the feedback comprises the neurofeedback and a feedback about the biofeedback signal quality.

The invention is defined by the independent claim, with further embodiments defined in the dependent claims.

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. 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. For small numbers of electrodes, monitoring the contact may be performed by presenting a measure of the contact, such as the impedance seen by an electrode or the force on the electrode, numerically or even graphically. However, as the number of active electrodes used in an ablation procedure increases, it becomes increasingly difficult for the physician to monitor any parameter for the individual electrodes. In the case of electrode contact, this problem is exacerbated by the fact that in most cases as the contact varies, so the parameter measuring the contact also varies.

Embodiments of the present invention solve the above problems during a medical procedure such as a mapping or ablation procedure, by presenting a physician with multiple IEGM traces (e.g., voltage versus time graphs) of signals acquired by electrodes of a catheter, while modifying a visual feature of those traces representing electrical activity sensed by the electrodes that are deemed to be in sufficient contact with the heart tissue. Therefore, the traces of electrodes with sufficient tissue contact are highlighted for easy identification by the physician.

The traces representing electrical activity sensed by the electrodes that are in sufficient contact with the heart tissue are typically modified to be brighter compared to traces representing electrical activity sensed by the electrodes that are not in sufficient contact with the heart tissue. The human eye is very sensitive to changes in brightness. Therefore, the brighter traces allow quicker identification of the relevant IEGM traces by the physician.

In some embodiments, traces representing electrical activity sensed by the electrodes that are in sufficient contact with the heart tissue are typically modified to be a different color compared to traces representing electrical activity sensed by the electrodes that are not in sufficient contact with the heart tissue.

In other embodiments, traces representing electrical activity sensed by the electrodes that are in sufficient contact with the heart tissue are typically modified to be a different color and to be brighter compared to traces representing electrical activity sensed by the electrodes that are not in sufficient contact with the heart tissue.

The physician may then inspect the highlighted signals and analyze those signals to find arrythmia and/or determine which electrodes are in contact with the tissue for ablation purposes.

As non-highlighted traces indicate electrodes without sufficient tissue contact, the physician may use this indication to adjust the position of the catheter to improve tissue contact of the electrodes associated with the non-highlighted traces.

In some embodiments, a fading effect is used to dim the brightness, or return the color, used to highlight a trace associated with an electrode in sufficient contact with the tissue, to the original brightness and/or color (used for traces associated with electrodes not in sufficient tissue contact), after the electrode associated with the trace is no longer in sufficient contact with the tissue. The fading effect takes place over a suitable time window, of one to three seconds. The fading effect helps to smooth out brightness and/or color changes that would otherwise occur due to intermittent and/or a varying quality of contact.

In the above discussion, sufficiency of tissue contact is used to decide whether or not to highlight 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.

In response to signals provided by the catheter, processing circuitry assesses a 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 electrical 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 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>, 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 view of a medical procedure system <NUM> constructed and operative in accordance with an embodiment of the present invention. Reference is also made to <FIG>, which is a schematic view of a catheter <NUM> for use in the system <NUM> of <FIG>.

The medical procedure system <NUM> is used to determine the position of the catheter <NUM>, seen in an inset <NUM> of <FIG> and in more detail in <FIG>. The catheter <NUM> includes a shaft <NUM> and a plurality of deflectable arms <NUM> (only some labeled for the sake of simplicity) for inserting into a body-part of a living subject. The deflectable arms <NUM> have respective proximal ends connected to the distal end of the shaft <NUM>.

The catheter <NUM> includes a position sensor <NUM> disposed on the shaft <NUM> in a predefined spatial relation to the proximal ends of the deflectable arms <NUM>. The position sensor <NUM> may include a magnetic sensor <NUM> and/or at least one shaft electrode <NUM>. The magnetic sensor <NUM> may include at least one coil, for example, but not limited to, a dual-axis or a triple axis coil arrangement to provide position data for location and orientation including roll. The catheter <NUM> includes multiple electrodes <NUM> (only some are labeled in <FIG> for the sake of simplicity) disposed at different, respective locations along each of the deflectable arms <NUM>. Typically, the catheter <NUM> may be used for mapping electrical activity in a heart of the living subject using the electrodes <NUM>, or for performing any other suitable function in a body-part of a living subject.

The medical procedure system <NUM> may determine a position and orientation of the shaft <NUM> of the catheter <NUM> based on signals provided by the magnetic sensor <NUM> and/or the shaft electrodes <NUM> (proximal-electrode 52a and distal-electrode 52b) fitted on the shaft <NUM>, on either side of the magnetic sensor <NUM>. The proximal-electrode 52a, the distal-electrode 52b, the magnetic sensor <NUM> and at least some of the electrodes <NUM> are connected by wires running through the shaft <NUM> via a catheter connector <NUM> to various driver circuitries in a console <NUM>. In some embodiments, at least two of the electrodes <NUM> of each of the deflectable arms <NUM>, the shaft electrodes <NUM>, and the magnetic sensor <NUM> are connected to the driver circuitries in the console <NUM> via the catheter connector <NUM>. In some embodiments, the distal-electrode 52b and/or the proximal electrode 52a may be omitted.

The illustration shown in <FIG> is chosen purely for the sake of conceptual clarity. Other configurations of shaft electrodes <NUM> and electrodes <NUM> are possible. Additional functionalities may be included in the position sensor <NUM>. Elements which are not relevant to the disclosed embodiments of the invention, such as irrigation ports, are omitted for the sake of clarity.

A physician <NUM> navigates the catheter <NUM> to a target location in a body part (e.g., a heart <NUM>) of a patient <NUM> by manipulating the shaft <NUM> using a manipulator <NUM> near the proximal end of the catheter <NUM> and/or deflection from a sheath <NUM>. The catheter <NUM> is inserted through the sheath <NUM>, with the deflectable arms <NUM> gathered together, and only after the catheter <NUM> is retracted from the sheath <NUM>, the deflectable arms <NUM> are able to spread and regain their intended functional shape. By containing deflectable arms <NUM> together, the sheath <NUM> also serves to minimize vascular trauma on its way to the target location.

Console <NUM> comprises processing circuitry <NUM>, typically a general-purpose computer and a suitable front end and interface circuits <NUM> for generating signals in, and/or receiving signals from, body surface electrodes <NUM> which are attached by wires running through a cable <NUM> to the chest and to the back, or any other suitable skin surface, of the patient <NUM>.

Console <NUM> further comprises a magnetic-sensing sub-system. The patient <NUM> is placed in a magnetic field generated by a pad containing at least one magnetic field radiator <NUM>, which is driven by a unit <NUM> disposed in the console <NUM>. The magnetic field radiator(s) <NUM> is configured to transmit alternating magnetic fields into a region where the body-part (e.g., the heart <NUM>) is located. The magnetic fields generated by the magnetic field radiator(s) <NUM> generate direction signals in the magnetic sensor <NUM>. The magnetic sensor <NUM> is configured to detect at least part of the transmitted alternating magnetic fields and provide the direction signals as corresponding electrical inputs to the processing circuitry <NUM>.

In some embodiments, the processing circuitry <NUM> uses the position-signals received from the shaft electrodes <NUM>, the magnetic sensor <NUM> and the electrodes <NUM> to estimate a position of the catheter <NUM> inside an organ, 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 catheter <NUM> inside a cardiac chamber. The position coordinates of the shaft electrodes <NUM> and the electrodes <NUM> may be determined by the processing circuitry <NUM> based on, among other inputs, measured impedances, or on proportions of currents distribution, between the electrodes <NUM>, <NUM> and the body surface electrodes <NUM>. The console <NUM> drives a display <NUM>, which shows the distal end of the catheter <NUM> inside the heart <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 an Active Current Location (ACL) impedance-based position-tracking method. In some embodiments, using the ACL method, the processing circuitry <NUM> is configured to create a mapping (e.g., current-position matrix (CPM)) between indications of electrical impedance and positions in a magnetic coordinate frame of the magnetic field radiator(s) <NUM>. The processing circuitry <NUM> estimates the positions of the shaft electrodes <NUM> and the electrodes <NUM> by performing a lookup in the CPM.

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.

<FIG> shows only elements related to the disclosed techniques, for the sake of simplicity and clarity. The 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 catheter <NUM> described above includes eight deflectable arms <NUM> with six electrodes per arm <NUM>. Any suitable catheter may be used instead of the catheter <NUM>, for example, a catheter with a different number of flexible arms and/or electrodes per arm, or a different probe shape such as a balloon catheter or a lasso catheter, by way of example only.

The medical procedure system <NUM> may also perform ablation of heart tissue using any suitable catheter, for example using the catheter <NUM> or a different catheter and any suitable ablation method. The console <NUM> may include an RF signal generator <NUM> configured to generate RF power to be applied by an electrode or electrodes of a catheter connected to the console <NUM>, and one or more of the body surface electrodes <NUM>, to ablate a myocardium of the heart <NUM>. The console <NUM> may include a pump (not shown), which pumps irrigation fluid into an irrigation channel to a distal end of a catheter performing ablation. The catheter performing the ablation may also include temperature sensors (not shown) which are used to measure a temperature of the myocardium during ablation and regulate an ablation power and/or an irrigation rate of the pumping of the irrigation fluid according to the measured temperature.

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

As previously mentioned, the catheter <NUM> is configured to be inserted into a chamber of the heart <NUM> of a living subject (the patient <NUM>). The catheter electrodes <NUM> are configured to contact tissue at respective locations within the chamber of the heart <NUM>.

The processing circuitry <NUM> is configured to receive (block <NUM>) signals from the catheter <NUM>. The signals may be received from any of the catheter electrodes <NUM>, the shaft electrodes <NUM>, and/or the magnetic sensor <NUM> and in some embodiments, from other sensors, such as force or pressure sensors which may provide measurements for use in assessing a quality of contact of the catheter electrodes <NUM> with the tissue. The signals may also be used to compute positions of the catheter electrodes <NUM>.

The processing circuitry <NUM> is configured, in response to the signals, to compute (block <NUM>) positions of the catheter electrodes <NUM>. The computation of the positions of the catheter electrodes <NUM> may be performed based on any suitable position tracking system, for example, based on measured impedances and/or spread of currents, or using the ACL method described above with reference to <FIG>.

The processing circuitry <NUM> is configured, in response to the signals, to assess (block <NUM>) a respective quality of contact of each of the catheter electrodes <NUM> with the tissue in the heart <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.

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>, as described in more detail with reference to <FIG>. 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 deflectable arms <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>, 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 electro-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.

Reference is now made to <FIG>, which is a flowchart <NUM> including exemplary steps in an example, unclaimed method of operation of the system <NUM> of <FIG> based on electrical impedances. The flowchart <NUM> includes steps which may be performed instead of, or in addition to, the steps of blocks <NUM> and <NUM> of <FIG>. Reference is also made to <FIG> and <FIG>.

The processing circuitry <NUM> is configured to measure (block <NUM>) an indication of electrical impedances between the body surface electrodes <NUM> and the catheter electrodes <NUM>. The processing circuitry <NUM> is configured to compute (block <NUM>) position coordinates of the catheter electrodes <NUM> responsively to the indication of the electrical impedances. The computation of the position coordinates may be based on any suitable position tracking method for example, the ACL method described above with reference to <FIG>, or using measured impedances, or proportions of currents distribution, between the electrodes <NUM> and the body surface electrodes <NUM>.

The processing circuitry <NUM> is configured to assess (block <NUM>) the respective quality of contact of each of the catheter electrodes <NUM> with the tissue in the heart <NUM> responsively to the indication of the electrical impedances as described in more detail with reference to <FIG> hereinabove.

Reference is now made to <FIG>, which is a schematic view of first exemplary intracardial electrogram (IEGM) traces <NUM> prepared by the system <NUM> of <FIG>. <FIG> shows three IEGM traces <NUM>.

The trace <NUM>-<NUM> represents electrical activity in the tissue that is sensed by one of the catheter electrodes <NUM> (<FIG>), which has been assessed not to be in sufficient contact with the tissue of the heart <NUM> (<FIG>).

The trace <NUM>-<NUM> has been highlighted using a brighter trace than used for the trace <NUM>-<NUM> or a different color than used for the trace <NUM>-<NUM>. The trace <NUM>-<NUM> represents electrical activity in the tissue that is sensed by one of the catheter electrodes <NUM> (<FIG>), which has been assessed to be in sufficient contact with the tissue.

The trace <NUM>-<NUM> has been partially highlighted (using a brighter trace than that used for the trace <NUM>-<NUM> or a different color than that used for the trace <NUM>-<NUM>) in a region <NUM> corresponding to a first time period when the catheter electrode <NUM>, which sensed the electrical activity represented by the trace <NUM>-<NUM>, was assessed to be in sufficient contact with the tissue. After the first time period of sufficient contact, the catheter electrode <NUM> was not in sufficient contact with the tissue. A fading effect is used in a region <NUM> of the trace <NUM>-<NUM>, corresponding to a second time period after the first time period. The fading effect is used to dim the brightness, or return the color, used to highlight the trace <NUM>-<NUM> in region <NUM>, to the original brightness and/or color (used for traces associated with electrodes not in sufficient tissue contact), after the electrode <NUM> associated with the trace <NUM>-<NUM> is no longer in sufficient contact with the tissue. The fading effect takes place over any suitable time window ofone to three seconds. The fading effect helps to smooth out brightness and/or color changes that would otherwise occur due to intermittent and/or a varying quality of contact.

Reference is now made to <FIG>, which is a schematic view of second exemplary intracardial electrogram (IEGM) traces <NUM> prepared by the system <NUM> of <FIG>. <FIG> shows traces <NUM> representing electrical activity sensed by about <NUM> of the catheter electrodes <NUM>. It can be seen that identifying the catheter electrodes <NUM> in sufficient contact with the tissue from the traces <NUM> without using trace highlighting would be a very difficult, if not, impossible, task for the physician <NUM> (<FIG>) to perform. <FIG> shows that four of the traces <NUM> (labeled <NUM>-<NUM>) have been highlighted using a brighter format and/or different color compared to the other non-highlighted traces <NUM> for easier identification. The traces <NUM> may be displayed on the display <NUM> (<FIG>) with text indicating which of the traces <NUM> corresponds to which of the catheter electrodes <NUM> by using some suitable identification for each of the catheter electrodes <NUM>. For example, the trace <NUM> corresponding to a fifth catheter electrode <NUM> on a first one of the deflectable arms <NUM> may be labeled "A5", and the trace <NUM> corresponding to a first catheter electrode <NUM> on a third one of the deflectable arms <NUM> may be labeled "C1".

Reference is again made to <FIG>. Reference is also made to <FIG> and <FIG>. The processing circuitry <NUM> is configured, in response to the signals received from the catheter <NUM>, to render (block <NUM>) to the display <NUM> respective intracardiac electrograms (IEGM) traces <NUM> representing electrical activity in the tissue that is sensed by the catheter electrodes <NUM> at respective locations, while modifying a visual feature of at least some of the traces (e.g., traces <NUM>-<NUM> of <FIG>) responsively to the respective quality of contact of the catheter electrodes <NUM> with the tissue of the heart <NUM> at the respective locations. The processing circuitry <NUM> is configured to modify the visual feature of the traces (e.g., traces <NUM>-<NUM> of <FIG>) representing the electrical activity sensed by ones of the catheter electrodes <NUM> having a quality of contact with the tissue greater than a predefined threshold quality of contact. The predefined threshold quality of contact may be defined with respect to any one or more of the following by way of example only: a predefined impedance, a predefined force, a predefined pressure, and/or a predefined IEGM amplitude, as described above.

In some embodiments, the processing circuitry <NUM> is configured to modify the visual feature by increasing (block <NUM>) a brightness of at least some of the traces <NUM> responsively to the respective quality of contact of the catheter electrodes <NUM> with the tissue of the heart at the respective locations. In some embodiments, the processing circuitry is configured to increase the brightness of the traces (e.g., traces <NUM>-<NUM> of <FIG>) representing the electrical activity sensed by first ones of the catheter electrodes <NUM> having a high quality of contact with the tissue relative to the traces <NUM> representing the electrical activity sensed by second ones of the catheter electrodes having a lower quality of contact with the tissue.

In some embodiments, in addition to, or instead of increasing the brightness of at least some of the traces <NUM>, the processing circuitry <NUM> is configured to change a color of at least some of the traces <NUM> responsively to the respective quality of contact of the catheter electrodes <NUM> with the tissue of the heart <NUM> at the respective locations. In some embodiments, the processing circuitry <NUM> is configured to change the color (and optionally increase the brightness) of the traces (e.g., traces <NUM>-<NUM> of <FIG>) representing the electrical activity sensed by first ones of the catheter electrodes <NUM> having a high quality of contact with the tissue relative to the traces <NUM> representing the electrical activity sensed by second ones of the catheter electrodes having a lower quality of contact with the tissue.

As described above with reference to <FIG>, a fading effect may be used to indicate time periods after electrode contact falls below the predefined threshold quality of contact. The processing circuitry <NUM> is configured to modify (block <NUM>) the visual feature of the trace(s) <NUM> for a period of time after the quality of contact decreases below the predefined threshold quality of contact. The step of block <NUM> is now described in more detail.

Reference is again made to <FIG>. The processing circuitry <NUM> (<FIG>) is configured to perform a first modification (for example, in the region <NUM>) of the visual feature of one of the traces <NUM>-<NUM>, for example, representing the electrical activity sensed by one of the catheter electrodes <NUM> (<FIG>) having a quality of contact with the tissue greater than the predefined threshold quality during a first time period. The processing circuitry <NUM> is also configured to perform a second modification or fading effect (for example, in the region <NUM>) of the visual feature of the trace <NUM>-<NUM>, for example, representing the electrical activity sensed by that catheter electrode <NUM> having a quality of contact with the tissue less than the predefined threshold quality during a second time period following the first time period. 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 dimmer (and/or the color of the trace <NUM>-<NUM> reverting to its original color used prior to the first time period) as the second time period progresses.

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. 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.

Claim 1:
A medical system (<NUM>), comprising:
a catheter (<NUM>) configured to be inserted into a chamber of a heart (<NUM>) of a living subject (<NUM>), and including catheter electrodes (<NUM>) configured to contact tissue at respective locations within the chamber of the heart (<NUM>);
a display (<NUM>); and
processing circuitry configured to receive (<NUM>) signals from the catheter (<NUM>), and in response to the signals:
assess (<NUM>) a respective quality of contact of each of the catheter electrodes (<NUM>) with the tissue in the heart (<NUM>); and
render (<NUM>) to the display (<NUM>) respective intracardiac electrograms (IEGM) traces (<NUM>) representing electrical activity in the tissue that is sensed by the catheter electrodes (<NUM>) at the respective locations, while modifying a visual feature of at least some of the traces (<NUM>-<NUM>) responsively to the respective quality of contact of the catheter electrodes (<NUM>) with the tissue of the heart (<NUM>) at the respective locations;
wherein the processing circuitry is configured to modify the visual feature of the at least some traces (<NUM>-<NUM>) representing the electrical activity sensed by ones of the catheter electrodes (<NUM>) having a quality of contact with the tissue greater than a predefined threshold quality of contact; and
wherein the processing circuitry is configured to:
perform a first modification of the visual feature of one of the traces (<NUM>-<NUM>) representing the electrical activity sensed by one of the catheter electrodes (<NUM>) having a quality of contact with the tissue greater than the predefined threshold quality during a first time period;
perform a second modification of the visual feature of the one trace (<NUM>-<NUM>) representing the electrical activity sensed by the one catheter electrode (<NUM>) having a quality of contact with the tissue less than the predefined threshold quality during a second time period following the first time period; and
the system characterized in that the second modification of the visual feature changes as the second time period progresses;
wherein the second time period lasts one to three seconds.