Patent Description:
In cardiac electroanatomical mapping systems that are known in the art, an operator - typically a physician - inserts a catheter through a patient's vascular system into a chamber of the heart. An electrode or electrode assembly at the distal end of the catheter contacts the myocardial tissue in the chamber and receives electrical signals from the tissue, which are conveyed through the catheter to a mapping console. The operator manipulates the catheter within the heart in order to acquire signals from many points within the heart chamber, thus enabling the console to construct a map showing the physical structure of the walls of the heart chamber and the distribution of electrical activity over the walls.

As the operator cannot see the distal end of the catheter in the heart chamber, a number of techniques have been developed to assist the operator in visualizing and understanding the process of EP signal acquisition. For example, <CIT> describes a method for highlighting an electrode image according to an electrode signal. A graphical image of a heart of a patient is presented on a display screen, including icons representing a catheter that is positioned within the heart and an electrode on the catheter, while the electrode is in contact with tissue at a location in the heart. The method further includes acquiring, using the electrode, electrical signals from the tissue at the location, and processing the acquired signals so as to detect an occurrence of a predefined signal feature in the acquired signals. The method also includes, upon detecting the occurrence of the predefined signal feature, modifying a visual feature of at least one of the icon representing the electrode and the icon representing the catheter on the display screen.

As another example, <CIT> describes a method and system for visualization of electrophysiology information sensed by electrodes on a catheter. The method includes recording times of electrode signal acquisition, designating a reference electrode signal acquisition, assigning a relative time to each recorded time of electrode signal acquisition relative to the reference electrode signal acquisition, identifying the electrodes with signal acquisition, correlating assigned relative times to identified electrodes to generate a sequence of electrode signal acquisitions, and generating a visual representation of the sequence of electrode signal acquisitions generating a visual representation with a graphical image of the electrodes, wherein individual electrodes are visually marked to represent the sequence of electrode signal acquisitions.

European Patent Application Publication No. <CIT> describes a method for performing a medical procedure including bringing a probe into contact with an organ in a body of a patient. A map of the organ is displayed, and the location of the probe relative to the map is tracked. A therapy is applied via the probe at multiple tissue sites in the organ with which the probe is brought into contact. Stability of the contact between the probe and the tissue sites is assessed while applying the therapy. The map is automatically marked, responsively to the assessed stability, to indicate the tissue sites at which the therapy was applied. Typically, the system marks sites on the map that satisfy a certain stability criterion, which may be defined by the system operator.

<CIT> describes transducer-based systems and methods which may be configured to display a graphical representation of a transducer-based device, the graphical representation including graphical elements corresponding to transducers of the transducer-based device, and also including between graphical elements respectively associated with a set of the transducers and respectively associated with a region of space between the transducers of the transducer-based device. Selection of graphical elements and/or between graphical elements can cause activation of the set of transducers associated with the selected elements. Transducer activation characteristics, such as initiation time, activation duration, activation sequence, and energy delivery characteristics, can vary based on numerous factors. Visual characteristics of graphical elements and between graphical elements can change based on an activation-status of the corresponding transducers. Activation requests for a set of transducers can be denied if it is determined that a transducer in the set of transducers is unacceptable for activation.

European Patnet Application Publication No. <CIT> describes a system including a memory and a processor. The memory is configured to store a definition of a cardiac pacing protocol. The processor is configured to (a) receive the stored definition of the cardiac pacing protocol, (b) in accordance with the pacing protocol, to automatically pace from an intracardiac location and to acquire respective sensed ECG signals, (c) based on one or more prespecified criteria for validity of the sensed ECG data, automatically accept or reject the sensed ECG signals, (d) based on one or more prespecified criteria for identification of an arrhythmia, identify the intracardiac location as an arrhythmogenic focus or pathway, (e) overlay the identified intracardiac location an electrophysiological (EP) map, and (f) subsequently identify or reject a new intracardiac location as an arrhythmogenic focus or pathway and overlay the new location on the EP map when pacing again from the new intracardiac location.

<CIT> describes systems for facilitating processing of cardiac information based on sensed electrical signals including a processing unit configured to receive a set of electrical signals; receive an indication of a measurement location corresponding to each electrical signal of the set of electrical signals; and generate, based on at least one of an annotation waveform corresponding to each electrical signal of the set of electrical signals and a set of annotation mapping values, an annotation histogram.

Embodiments of the present invention that are described hereinbelow provide improved systems for mapping of EP parameters.

There is therefore provided, in accordance with an embodiment of the invention, a system for electrophysiological measurement, including a probe having a distal end configured for insertion into a body cavity of a patient and including electrodes that are disposed along the distal end and are configured to contact tissue at multiple locations within the body cavity while an operator manipulates the probe. The system includes a display and a processor, which is configured to acquire electrophysiological (EP) signals from the electrodes within the body cavity, to apply one or more filtering criteria to the EP signals in order to select a first set of the EP signals while rejecting a second set of the EP signals, to render an image to the display based on the EP signals in the first set, and to output to the operator an indication of a reason for the rejection of the EP signals in the second set. The processor is configured to output the indication with respect to a rejection of the signals by a given filtering criterion only when a percentage of the EP signals that are rejected by the given filtering criterion is greater than a predefined threshold.

In some embodiments, the probe includes a catheter, and the distal end is configured for insertion into a chamber of the heart. In one such embodiment, the processor is configured to track a position of the distal end of the catheter within the chamber and to render to the display an electroanatomical map of the chamber based on the EP signals in the first set. In a disclosed embodiment, the distal end of the catheter includes multiple flexible spines along which the electrodes are disposed.

Typically, the processor is configured to present the indication of the reason for the rejection on the display in a form selected from a group consisting of a textual output and a graphical icon.

In a disclosed embodiment, at least one of the filtering criteria applies to a proximity of the electrodes relative to a wall of the body cavity, and the processor is configured to reject the EP signals in the second set responsively to the at least one of the filtering criteria when a distance between the location of the electrodes and the wall is greater than a given threshold and to indicate to the operator that the distal end of the probe should be brought closer to the wall of the body cavity.

Additionally or alternatively, when the body cavity includes a chamber of a heart of the patient, at least one of the filtering criteria applies to a cycle length of the heart while the processor acquires the EP signals, and the processor is configured to reject the EP signals in the second set responsively to the at least one of the filtering criteria when the cycle length changes during acquisition of the EP signals by more than a given threshold and to indicate to the operator that the EP signals in the second set were rejected because of a change in the cycle length during acquisition of the EP signals.

Further additionally or alternatively, at least one of the filtering criteria applies to a stability of the electrodes relative to a wall of the body cavity, and the processor is configured to reject the EP signals in the second set responsively to the at least one of the filtering criteria when the electrodes move by more than a maximal distance during acquisition of the EP signals and to indicate to the operator to stabilize a manipulation of the probe during the acquisition of the EP signals.

In some embodiments, at least one of the filtering criteria applies to a level of voltage measured by the electrodes, and the processor is configured to reject the EP signals in the second set responsively to the at least one of the filtering criteria and to indicate to the operator that the voltage of the EP signals in the second set was below a certain minimum.

In yet another embodiment, at least one of the filtering criteria applies to a density of the locations at which the EP signals are acquired, and the processor is configured to reject the EP signals in the second set responsively to the at least one of the filtering criteria and to indicate to the operator that the electrodes acquiring the EP signals in the second set were in a region of the body cavity in which a sufficient number of the EP signals was already acquired.

To produce an accurate electroanatomical map of a heart chamber, the mapping system typically acquires electrical signals from hundreds or even thousands of different points along the wall of the chamber. To reduce the time needed to acquire this large volume of data, mapping systems commonly use catheters having many electrodes at their distal ends, which are capable of sensing respective signals simultaneously at respective locations within the heart chamber. Furthermore, the system may acquire signals from the electrodes in a continuous mode, meaning that the signals received from the electrodes are automatically sampled and recorded continually as the operator moves the distal end of the catheter through the heart chamber.

This sort of continuous-mode mapping can give rise to many spurious measurements, i.e., signals acquired from one or more of the electrodes that do not accurately reflect the actual electrical activity in the myocardium. Such spurious measurements can occur, for example, when the electrode from which a signal was acquired was not actually in contact with the myocardium, or when the electrode was moving too rapidly across the myocardium to make a stable measurement from a well-defined location. It is desirable under such circumstances that the mapping console automatically filter the electrical signals and discard the spurious results, which might otherwise corrupt the map of the heart chamber. Methods and criteria for performing this sort of filtering are described, for example, in <CIT>, which is assigned to the assignee of the present patent application.

As a result of filtering the signals in this manner, however, many of the signals acquired by the catheter may be discarded, with the result that the rate of acquisition of map data is reduced, and the length of time needed to complete the mapping procedure is increased. The operator of the system may not understand the problems that gave rise to signal rejection and may thus be unable to remedy these problems. In existing systems, the operator may not even be aware that a large fraction of the acquired data has been discarded.

Embodiments of the present invention that are described herein address these problems by automatically providing guidance to the operator of an electroanatomical mapping system. The guidance indicates to the operator why many signals have been rejected and can thus help the operator in improving his or her mapping technique. For example, the operator may use the guidance that is provided in this manner in learning to manipulate the catheter so that the electrodes maintain good contact with the myocardium while sliding smoothly and not too quickly over the appropriate areas of the heart wall.

The disclosed embodiments provide a system for electrophysiological measurement comprising a probe having a distal end configured for insertion into a body cavity of a patient, such as a catheter for insertion into a chamber of the heart, with electrodes disposed along the distal end of the probe. The operator manipulates the probe so that the electrodes contact tissue at multiple locations within the body cavity. A processor connected to the probe acquires electrophysiological (EP) signals from the electrodes within the body cavity and applies filtering criteria to the EP signals. The processor selects a set of the EP signals that satisfy the filtering criteria and uses these signals in rendering an image, such as an electroanatomical map, to a display.

The processor rejects the EP signals that fail to satisfy the filtering criteria. The processor outputs to the operator an indication of the predominant reason or reasons for the rejection of these EP signals, for example in the form of a graphical icon and/or text on the display. The processor is configured to output the indication with respect to a rejection of the signals by a given filtering criterion only when a percentage of the EP signals that are rejected by the given filtering criterion is greater than a predefined threshold. In this way, the processor gives the operator insights into problems in his or her data acquisition techniques, and thus guides the operator in overcoming these problems in order to acquire EP data with greater efficiency and reliability.

<FIG> is a schematic pictorial illustration of a system <NUM> for mapping an EP parameter in a heart <NUM> of a patient <NUM>, in accordance with an embodiment of the present invention. The embodiment shown in the current figure and subsequent figures refers to an example of acquiring EP signals from a chamber of heart <NUM>. In alternative embodiments, the values of EP parameters may be acquired using other sorts of mapping apparatus, not only from within the heart, but also from other organs and tissue, as will be apparent to those skilled in the art after reading the present description.

An operator <NUM>, such as a physician, navigates a catheter <NUM> to a target location in heart <NUM> of patient <NUM>, by manipulating a shaft <NUM> of the catheter, using a manipulator <NUM> near the proximal end of the catheter. In the pictured example, catheter <NUM> comprises a basket assembly <NUM> at its distal end, as shown in an inset <NUM>, but alternatively other types of catheters may be used, as are known in the art. As seen in an inset <NUM>, operator <NUM> manipulates catheter <NUM> to perform electroanatomical mapping of a chamber of heart <NUM>. EP signals are acquired from the myocardial tissue by bringing electrodes <NUM> on basket assembly <NUM> into contact with the tissue within the heart, as further detailed below.

Basket assembly <NUM> is inserted into heart <NUM> in a collapsed configuration, for example through a sheath (not shown), and only after the catheter exits the sheath does the basket expand to its intended functional shape, as shown in inset <NUM>. By containing basket assembly <NUM> in a collapsed configuration, the sheath also serves to minimize vascular trauma along the way to the target location.

For purposes of position tracking, basket assembly <NUM> incorporates a magnetic sensor 50A, seen in inset <NUM>, at the distal end of catheter <NUM> (i.e., at the proximal end of the basket assembly). Typically, although not necessarily, sensor 50A is a Triple-Axis Sensor (TAS), comprising three miniature coils oriented in different directions. In the pictured embodiment, a second magnetic sensor 50B is incorporated in the distal end of basket assembly <NUM>. Sensor 50B may be a Single-Axis Sensor (SAS) or a Triple-Axis Sensor (TAS), for example. Alternatively, catheter <NUM> may comprise other sorts of magnetic sensors, at these or other locations. Alternatively or additionally, the catheter may comprise other sorts of position sensors, such as impedance-based or ultrasonic position sensors, as are known in the art.

Basket assembly <NUM> comprises multiple expandable spines <NUM>, which are mechanically flexible. Multiple electrodes <NUM> are fixed to each spine <NUM>, for a total of, for example, <NUM> electrodes. Electrodes <NUM> are configured to touch the tissue within heart <NUM> for the purpose of sensing EP signals, i.e., intracardiac electrogram signals in the pictured example. Magnetic sensors 50A and 50B and electrodes <NUM> are connected by wires (not shown) running through shaft <NUM> to processing circuits in a console <NUM>.

Alternatively, system <NUM> may comprise other types of catheters, with other sorts of electrode arrays, such as an inflatable balloon catheter with electrodes <NUM> on its outer surface, or a catheter having one or more flexible arms or having a curved "lasso" at its distal end.

System <NUM> comprises a position-tracking sub-system <NUM> in console <NUM> for finding the position and orientation of basket assembly <NUM>, and thereby identifying the locations of electrodes <NUM>. Patient <NUM> is placed in a magnetic field generated by a pad containing magnetic field generator coils <NUM>, which are driven by position-tracking sub-system <NUM>. The magnetic fields generated by coils <NUM> give rise to electrical signals in sensors 50A and 50B, which are indicative of the position and orientation of the sensors. The signals from sensors 50A and 50B are transmitted back to position-tracking sub-system <NUM>, which converts the signals to corresponding digital inputs to a processor <NUM>. Processor <NUM> uses these inputs to compute the position and orientation of basket assembly <NUM> and thus to find the respective location coordinates of each of electrodes <NUM>.

Methods of position and orientation sensing using external magnetic fields and magnetic sensors, such as sensors 50A and 50B, are implemented in various medical applications, for example, in the CARTO® system, available from Biosense Webster, Inc. (Irvine, California). Such methods are described in detail in <CIT>, <CIT>, <CIT>, <CIT>, <CIT> and <CIT>, in <CIT>, and in <CIT>, <CIT> and <CIT>.

Alternatively or additionally, as noted above, system <NUM> may use other methods of position sensing to find the locations of electrodes <NUM>. For example, processor <NUM> may map the locations of electrodes <NUM> by measuring impedances between electrodes <NUM> and body-surface electrodes <NUM>, which are placed on the chest of patient <NUM> and connected to console <NUM> by leads <NUM>.

Processor <NUM> additionally receives EP signals from electrodes <NUM> on basket assembly <NUM> via front-end circuits <NUM>. These circuits apply analog and/or digital filters and amplifiers to the signals under the control of the processor. Processor <NUM> uses the information contained in these EP signals together with the coordinates provided by magnetic sensors 50A and 50B in constructing an electroanatomical map <NUM> of the chamber of heart <NUM> in which basket assembly <NUM> is located, such as a map showing the voltage levels or local activation time (LAT) of the EP signals as a function of location along the chamber walls. During and/or following the procedure, processor <NUM> renders electroanatomical map <NUM> to a display <NUM>.

In choosing the EP signals to include in the map, processor <NUM> applies filtering criteria, while rejecting the signals that do not meet these criteria. These criteria may be fixed, or they may be adjusted by an operator of system <NUM>, for example as described in the above-mentioned <CIT>. Examples of such criteria and their application are presented hereinbelow. When a percentage of the EP signals that are rejected by a given filtering criterion is greater than a predefined threshold, processor <NUM> outputs an indication of the reason for rejection, for example in graphical and/or textual form, to display <NUM>.

Processor <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. In particular, processor <NUM> runs a dedicated algorithm that enables the processor to perform the disclosed steps of data acquisition, mapping, and operator guidance, as described below.

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.

<FIG> is a schematic illustration of a graphical user interface (GUI), which is presented on display <NUM> of system <NUM>. Processor <NUM> renders electroanatomical map <NUM> of a chamber of heart <NUM> to display <NUM>, based on the EP signals acquired by electrodes <NUM> and the position information provided by position-tracking sub-system <NUM>. Processor <NUM> superimposes a basket icon <NUM> on map <NUM>, showing the current position of basket assembly <NUM> at the distal end of catheter <NUM> within the heart chamber, with icon segments <NUM> corresponding to electrodes <NUM>.

Map <NUM> shows the three-dimensional (3D) form of the inner wall of a heart chamber into which the distal end of catheter <NUM> is inserted, with coloring to indicate the EP parameters sensed by electrodes <NUM>. The 3D form of the chamber wall is reconstructed, for example, by a process of fast anatomical mapping (FAM), which locates the outer bounds of a point cloud formed by the position coordinates of basket assembly <NUM> as it moves through the heart chamber. FAM techniques that can be used in this context are described, for example, in <CIT> and in <CIT>. The coloring may indicate the LAT or voltage level measured by electrodes <NUM> at each location along the reconstructed form of the chamber wall.

In the present embodiment, processor <NUM> acquires the EP signals and position coordinates in continuous mode, as the operator manipulates catheter <NUM> within the heart <NUM>, and updates map <NUM> continually based on the acquired information. In other words, the processor does not wait for a specific operator input to capture data from catheter <NUM>, but rather samples the EP signals and position data autonomously at regular intervals. As noted earlier and described in greater detail in the above-mentioned <CIT>, processor <NUM> applies filtering criteria to the EP signals in order to select the set of signals to be incorporated in map <NUM> and reject the signals that do not satisfy the criteria.

Based on the results of application of the filtering criteria, processor <NUM> also renders an operator guidance icon <NUM> and/or guidance text <NUM> to display <NUM>. Alternatively or additionally, this guidance information may be conveyed by other means, such as an audio output from console <NUM>. Icon <NUM> and text <NUM> indicate the reason or reasons for rejection of a substantial fraction of the EP signals by the filtering criteria and thus guide the operator in achieving more effective signal acquisition. Icon <NUM> may be color-coded, for example, according to the reasons for rejection. Optionally, icon segments <NUM> may be color-coded in a similar fashion to show the locations of electrodes <NUM> whose output signals were rejected for the corresponding reasons.

By way of example, but not limitation, the reasons for rejection of EP signals and the corresponding operator indications and guidance can include the following:.

The above criteria and operator indications are presented by way of example, and other sorts of guidance may be derived from the EP signals and location data and presented to the operator in similar fashion.

<FIG> is a flow chart that schematically illustrates a method for electroanatomical mapping with automated operator guidance. The process is described here, for the sake of concreteness and clarity, with reference to the elements of system <NUM> (<FIG>). Alternatively, the principles of this method may be applied, mutatis mutandis, in other system configurations used for EP signal acquisition, in the heart as well as in other body cavities.

Operator <NUM> inserts catheter <NUM> into heart <NUM>, so that basket assembly <NUM> opens and electrodes <NUM> sense EP signals within the heart, at a signal acquisition step <NUM>. Processor <NUM> collects the signals continuously, as explained above, while operator <NUM> manipulates the catheter within the heart. The processor applies filter criteria to the EP signals, such as the criteria described above, in order to select the set of the signals that satisfy the criteria, at a signal selection step <NUM>. The processor extracts the parameters of interest from these signals, such as the voltage or LAT, and uses these parameters together with the coordinates of the electrodes that acquired the signals in constructing a map of the heart chamber. The processor continues to construct and add to the map continually as the operator moves the distal end of the catheter along the wall of the heart chamber.

Over each period of signal acquisition, processor <NUM> evaluates the percentage of the EP signals that are rejected by the filtering criteria, at a rejection assessment step <NUM>. When the percentage of the signals rejected by a given filtering criterion exceeds a predefined threshold, the processor outputs an indication of the reason for rejection, at an acquisition guidance step <NUM>. The guidance at this step typically takes the form of icon <NUM> and/or text <NUM>, as shown in <FIG>, but it may alternatively be provided by other means.

Whether or not the acquisition guidance is provided at a given stage in the mapping process, acquisition of signals and addition of data points to map <NUM> continues until mapping of the chamber is completed, at a map completion step <NUM>.

Claim 1:
A system (<NUM>) for electrophysiological measurement, comprising:
a probe (<NUM>) having a distal end configured for insertion into a body cavity of a patient and comprising electrodes (<NUM>) that are disposed along the distal end and are configured to contact tissue at multiple locations within the body cavity while an operator manipulates the probe (<NUM>);
a display (<NUM>); and
a processor (<NUM>) configured to acquire electrophysiological (EP) signals from the electrodes (<NUM>) within the body cavity, to apply one or more filtering criteria to the EP signals in order to select a first set of the EP signals while rejecting a second set of the EP signals, to render an image to the display (<NUM>) based on the EP signals in the first set, and to output to the operator an indication of a reason for the rejection of the EP signals in the second set, wherein the processor (<NUM>) is configured to output the indication with respect to a rejection of the signals by a given filtering criterion only when a percentage of the EP signals that are rejected by the given filtering criterion is greater than a predefined threshold.