Abstract:
Cardiac catheterization is carried out using a probe having sensing electrodes disposed on a distal portion thereof, placing the sensing electrodes in galvanic contact with respective locations in an atrium of the heart, thereafter acquiring electrograms from the sensing electrodes while concurrently detecting ventricular depolarization events, generating from the electrograms a time-varying electroanatomic map showing electrical propagation in the heart, and displaying the electroanatomic map in a series of visual images, the images including an icon that visually indicates the ventricular depolarization events.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     This invention relates to medical imaging systems. More particularly, this invention relates to operator interfaces in medical imaging systems. 
     Description of the Related Art 
     Cardiac arrhythmias, such as atrial fibrillation, occur when regions of cardiac tissue abnormally conduct electric signals to adjacent tissue, thereby disrupting the normal cardiac cycle and causing asynchronous rhythm. 
     Electrical activity in the heart is typically measured by advancing a multiple-electrode catheter to measure electrical activity at multiple points in the heart chamber simultaneously. A graphical user interface integrated with modern imaging systems for monitoring cardiac catheterization presents an abundance of dynamically changing information from the multiple electrodes to the operator, and facilitates efficient processing of the information by the operator. 
     Receiving atrial electrogram signals from intracardiac catheters is complicated by undesirable far field signal component mixed with near field electrical signals. In this environment near field signals indicate local activation, i.e., propagation of a signal through local regions being sensed by the electrodes. Detection of local activation is widely employed as an electrophysiological indicator of the local state of the heart. The far field electrical signals contain no useful information about local heart activation and only disturb the measurements. 
     Commonly assigned U.S. Patent Application Publication No. 2014/0005664 by Govari et al., which is herein incorporated by reference, discloses distinguishing a local component in an intracardiac electrode signal, due to the tissue with which the electrode is in contact from a remote-field contribution to the signal, and explains that a therapeutic procedure applied to the tissue can be controlled responsively to the distinguished local component. 
     SUMMARY OF THE INVENTION 
     Modern imaging systems adapted to cardiac electrophysiology produce dynamic functional electroanatomic maps of the heart, such as a time-varying map of local activation times (LAT), also known as a 4-dimensional LAT map. However, an operator who is attempting to annotate atrial activation onset times using a multi-electrode catheter and is presented with conventional maps of this sort may experience difficulty distinguishing near-field atrial activity from far-field ventricular activity. 
     According to disclosed embodiments of the invention, an indication of ventricular depolarization is visualized on a 4-dimensional LAT map as an icon, which is presented using the same time-window and color scale as the dynamic map, but is time-referenced to ventricular activity, e.g., an R-wave or QRS complex rather than to a local activation time of a point or region of the heart. 
     There is provided according to embodiments of the invention a method for guiding a medical procedure, which is carried out by inserting into a heart of a living subject a probe having sensing electrodes disposed on a distal portion thereof, placing the sensing electrodes in galvanic contact with respective locations in an atrium of the heart, thereafter acquiring electrograms from the sensing electrodes while concurrently detecting ventricular depolarization events, generating from the electrograms a time-varying electroanatomic map showing electrical propagation in the heart, and displaying the electroanatomic map in a series of visual images, the images including an icon that visually indicates the ventricular depolarization events. 
     The icon may be spaced apart from the electroanatomic map on the images. Alternatively, the icon may be positioned on the electroanatomic map at a center of mass of a ventricle of the heart. 
     An aspect of the method includes indicating local activation times for the respective locations on the electroanatomic map. 
     A further aspect of the method includes detecting on the electroanatomic map an indication of atrial depolarization in at least one of the respective locations, making a determination from a visual state of the icon that an instance of ventricular depolarization has occurred concurrently with the indication of atrial depolarization, and reporting responsively to the determination that the indication of atrial depolarization is a suspect false annotation event. 
     There is further provided according to embodiments of the invention an apparatus, including a processor connectable to an electrocardiographic sensor of ventricular activity and to a cardiac catheter having at least one sensing electrode disposed on a distal portion thereof. The apparatus includes a display linked to the processor, a memory accessible to the processor having programs and data objects stored therein. The programs include a graphical interface program. When the at least one sensing electrode is in galvanic contact with respective locations in an atrium of a heart, execution of the programs cause the processor to acquire electrograms from the at least one sensing electrode and concurrently detect ventricular depolarization events in the heart via the electrocardiographic sensor. The processor is further caused to generate from the electrograms a time-varying electroanatomic map showing electrical propagation in the heart, and to invoke the graphical interface program to present the electroanatomic map on the display as a series of visual images. The images include an icon that visually indicates the ventricular depolarization events. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       For a better understanding of the present invention, reference is made to the detailed description of the invention, by way of example, which is to be read in conjunction with the following drawings, wherein like elements are given like reference numerals, and wherein: 
         FIG. 1  is a pictorial illustration of a system for performing medical procedures in accordance with an embodiment of the invention; 
         FIG. 2  is a screen display generated by the system shown in  FIG. 1  in accordance with an embodiment of the invention; 
         FIG. 3  is a screen display generated by the system shown in  FIG. 1  in accordance with an embodiment of the invention; 
         FIG. 4  is a screen display generated by the system shown in  FIG. 1  in accordance with an embodiment of the invention; 
         FIG. 5  is a screen display generated by the system shown in  FIG. 1  in accordance with an embodiment of the invention; and 
         FIG. 6  is a flow-chart of a method of indicating ventricular electrical activity during atrial mapping in accordance with an embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various principles of the present invention. It will be apparent to one skilled in the art, however, that not all these details are necessarily needed for practicing the present invention. In this instance, well-known circuits, control logic, and the details of computer program instructions for conventional algorithms and processes have not been shown in detail in order not to obscure the general concepts unnecessarily. 
     Aspects of the present invention may be embodied in software programming code, which is typically maintained in permanent storage, such as a computer readable medium. In a client/server environment, such software programming code may be stored on a client or a server. The software programming code may be embodied on any of a variety of known non-transitory media for use with a data processing system, such as a USB memory, hard drive, electronic media or CD-ROM. The code may be distributed on such media, or may be distributed to users from the memory or storage of one computer system over a network of some type to storage devices on other computer systems for use by users of such other systems. 
     DEFINITIONS 
     “Annotations” refer to points on an electrogram that are considered to denote events of interest. In this disclosure the events are typically onset of the propagation of an electrical wave (local activation time) as sensed by an electrode. 
     Overview 
     Turning now to the drawings, reference is initially made to  FIG. 1 , which is a pictorial illustration of a system  10  for performing diagnostic and therapeutic procedures on a heart  12  of a living subject, which is constructed and operative in accordance with a disclosed embodiment of the invention. The system comprises a catheter  14 , which is percutaneously inserted by an operator  16  through the patient&#39;s vascular system into a chamber or vascular structure of the heart  12 . The operator  16 , who is typically a physician, brings the catheter&#39;s distal tip  18  into contact with the heart wall at an ablation target site. Functional electroanatomic maps, e.g., electrical activation maps may then be prepared, according to the methods disclosed in U.S. Pat. Nos. 6,226,542, and 6,301,496, and in commonly assigned U.S. Pat. No. 6,892,091, whose disclosures are herein incorporated by reference. One commercial product embodying elements of the system  10  is the CARTO® 3 System, available from Biosense Webster, Inc., 3333 Diamond Canyon Road, Diamond Bar, Calif. 91765. This system may be modified by those skilled in the art to embody the principles of the invention described herein. 
     Areas determined to be abnormal, for example by evaluation of the electrical activation maps, can be ablated by application of thermal energy, e.g., by passage of radiofrequency electrical current through wires in the catheter to one or more electrodes at the distal tip  18 , which apply the radiofrequency energy to the myocardium. The energy is absorbed in the tissue, heating it to a point (typically about 60° C.) at which it permanently loses its electrical excitability. When successful, this procedure creates non-conducting lesions in the cardiac tissue, which disrupt the abnormal electrical pathway causing the arrhythmia. The principles of the invention can be applied to different heart chambers to treat many different cardiac arrhythmias. 
     The catheter  14  typically comprises a handle  20 , having suitable controls on the handle to enable the operator  16  to steer, position and orient the distal end of the catheter as desired for the ablation. To aid the operator  16 , the distal portion of the catheter  14  contains position sensors (not shown) that provide signals to a position processor  22 , located in a console  24 . 
     Ablation energy and electrical signals can be conveyed to and from the heart  12  through one or more electrodes  32  located at or near the distal tip  18  via cable  34  to the console  24 . Pacing signals and other control signals may be conveyed from the console  24  through the cable  34  and the electrodes  32  to the heart  12 . One or more sensing electrodes  33 , also connected to the console  24 , are disposed near the ablation electrode  32  and have connections to the cable  34 . 
     Wire connections  35  link the console  24  with body surface electrodes  30  and other components of a positioning sub-system. The electrodes  32  and the body surface electrodes  30  may be used to measure tissue impedance at the ablation site as taught in U.S. Pat. No. 7,536,218, issued to Govari et al., which is herein incorporated by reference. A temperature sensor such as thermocouples  31 , may be mounted on or near the ablation electrode  32  and optionally or near the sensing electrodes  33 . 
     The console  24  typically contains one or more ablation power generators  25 . The catheter  14  may be adapted to conduct ablative energy to the heart using any known ablation technique, e.g., radiofrequency energy, ultrasound energy, and laser-produced light energy. Such methods are disclosed in commonly assigned U.S. Pat. Nos. 6,814,733, 6,997,924, and 7,156,816, which are herein incorporated by reference. 
     The positioning processor  22  is an element of a positioning subsystem in the system  10  that measures, inter alia, location and orientation coordinates of the catheter  14 . 
     In one embodiment, the positioning subsystem comprises a magnetic position tracking arrangement that determines the position and orientation of the catheter  14  by generating magnetic fields in a predefined working volume and sensing these fields at the catheter, using field generating coils  28 . The positioning subsystem may employ impedance measurement, as taught, for example in U.S. Pat. No. 7,756,576, which is hereby incorporated by reference, and in the above-noted U.S. Pat. No. 7,536,218. 
     As noted above, the catheter  14  is coupled to the console  24 , which enables the operator  16  to observe and regulate the functions of the catheter  14 . Console  24  includes a processor, preferably a computer with appropriate signal processing circuits. The processor is coupled to execute a graphical user interface program that is operative to produce the visual displays described below by driving a monitor  29 . The signal processing circuits typically receive, amplify, filter and digitize signals from the catheter  14 , including signals generated by the above-noted sensors and a plurality of location sensing electrodes (not shown) located distally in the catheter  14 . The digitized signals are received and used by the console  24  and the positioning system to compute the position and orientation of the catheter  14 , and to analyze the electrical signals from the electrodes. 
     Typically, the system  10  includes other elements, which are not shown in the figures for the sake of simplicity. For example, the system  10  may include an electrocardiogram (ECG) monitor, coupled to receive signals from one or more body surface electrodes, to provide an ECG synchronization signal and signal ventricular depolarization events to the console  24 . As mentioned above, the system  10  typically also includes a reference position sensor, either on an externally-applied reference patch attached to the exterior of the subject&#39;s body, or on an internally-placed catheter, which is inserted into the heart  12  maintained in a fixed position relative to the heart  12 . Conventional pumps and lines for circulating liquids through the catheter  14  for cooling the ablation site are provided. 
     With modern imaging systems used for monitoring cardiac catheterization, an increasing abundance of dynamically changing information is presented to the operator, to the extent that efficient processing of the information by the operator is impaired. Modern navigation and ablation catheters typically have multiple sensors, sensing electrodes, and ablation electrodes, which can be active in many combinations. Each of these has its own time-varying status, which is important for the operator to evaluate concurrently with extensive electroanatomic information regarding cardiac function. 
     User Interface 
     Reference is now made to  FIG. 2 , which is a typical screen display of an electroanatomic map of the left atrium, which is generated by the graphical user interface program on monitor  29  by the system  10  ( FIG. 1 ), in accordance with an embodiment of the invention. Right pane  37  shows electrograms obtained from multiple electrodes catheter. Left pane  39  presents a snapshot of a 4-dimensional LAT map  41  that was obtained at a time corresponding to vertical line  43  in the right pane  37 . A spherical icon  45  activates upon detection of an R-wave or QRS complex in one of the tracings or in another ECG lead (not shown). In the snapshot of the left pane  39 , the icon  45  is not activated, suggesting that signals being received from atrial regions  47 ,  49  at the time of the snapshot are not far-field signals from the ventricle. While the icon  45  is spherical, both its shape and its location with respect to the map  41  are exemplary and not limiting. Other shapes and locations of the icon  45  are possible, so long as the relative states of activation of the icon and the atria are readily presented to the operator. 
     In one embodiment the icon  45  is spaced apart from the map  41 . Alternatively, the icon  45  may be placed approximately the center of mass of the ventricles. In any case, visual indicia, e.g., coloring of the icon  45 , are referenced to detections of ventricular depolarization, such as an R wave or QRS complex. The color scale for the icon  45  and the map  41  should be the same, in order to facilitate its interpretation by the operator. A different color scale would be less intuitive, and even confusing to the operator. It would likely create a distorted impression of the information displayed on the map. 
     Reference is now made to  FIG. 3 , which is a screen display similar to  FIG. 2 , in accordance with an embodiment of the invention. Atrial depolarization is detected in atrial region  51 . The icon  45  is active, indicating that ventricular depolarization has occurred. However the activation time is not consistent with the activation times of the atrial region  51 . It may be concluded with confidence that the signals received at the time of the snapshot from the atrial region  51  are not affected by far-field signals from the ventricle. 
     Reference is now made to  FIG. 4 , which is another screen display similar to  FIG. 2  showing the posterior wall of the atria, in accordance with an embodiment of the invention. The snapshot of the 4-dimensional LAT map is obtained at a time corresponding to vertical line  53 . At this time activity is noted on tracing  55  and a concurrent deflection indicative of ventricular depolarization is seen on tracing  57 . The icon  45  is active, consistent with the occurrence of ventricular depolarization. An atrial region  59  is monitored by a lead from which the tracing  55  was obtained. The region  59  shows apparent activation in the region of the sino-atrial (SA) node; however, because it is concurrent with the activation of the icon  45 , the region  59  cannot be reliably interpreted on this snapshot, as the lead may have detected far-field ventricular activity While the operator could reference the tracing  57 , evaluate the ordered atrial activations on the right pane, and deduce that the activation of region  59  as well as activations of neighboring regions are inconsistent with physiologic SA node activation, the illuminated state (or other visual appearance) of the icon  45  relieves the operator from the burden of this sort of analysis. 
     Reference is now made to  FIG. 5 , which is a screen display similar to  FIG. 2 , in accordance with an embodiment of the invention. A large region  61  shows apparent activation, but is coincident with ventricular depolarization, as shown by the illuminated state of the icon  45 . The map  41  indicates locations  63  of mapping electrodes of the cardiac catheter (not shown). 
     While snapshots are necessarily shown in the above-described figures, in practice the operator views a 4-dimensional LAT map, and becomes immediately aware of ventricular depolarization when activation of the icon  45  occurs. This avoids the inconvenience of reference to and interpretation of the extensive data shown on the right pane  37 . In particular, the information provided by the icon  45  relates presumptive atrial annotations to ventricular depolarization. When a presumptive annotation is represented at an atrial location on the map  41  the operator can immediately determine if ventricular depolarization is present at the same time. If so, the event is suspect as being a false annotation because it may be corrupted by far-field signals from the ventricle. 
     Operation 
     Reference is now made to  FIG. 6 , which is a flow-chart of a method of indicating ventricular electrical activity during atrial mapping in accordance with an embodiment of the invention. The process steps are shown in a particular linear sequence in  FIG. 6  for clarity of presentation. However, it will be evident that many of them can be performed in parallel, asynchronously, or in different orders. Those skilled in the art will also appreciate that a process could alternatively be represented as a number of interrelated states or events, e.g., in a state diagram. Moreover, not all illustrated process steps may be required to implement the method. 
     At initial step  65  the heart is catheterized conventionally using any suitable multi-electrode catheter. Catheters such as the PentaRay® NAV or Navistar® Thermocool® catheters, available from Biosense Webster, are suitable for initial step  65 . The electrodes of the catheter is placed in galvanic contact with respective locations in one of the atria. 
     Next, at step  67  recording of cardiac electrical activity occurs and an activation map of the heart is generated. Step  67  comprises step  69  where atrial activity is recorded. Step  69  is usually performed concurrently with the multiple electrodes of the catheter, each having a respective location in the atrium, as indicated in  FIG. 5 . At the same time ventricular activity is recorded in step  71 , for example by using body surface electrodes. QRS complexes or R waves indicative of ventricular depolarization are input to the processor  22  ( FIG. 1 ), which activates of an icon on a graphical user interface, e.g., the icon  45  shown in the preceding figures. The time relationships of ventricular depolarization shown on the graphical display as the same visual scheme as that of the atrial electrodes, except that the visual scheme is linked to ventricular depolarization rather than to depolarization of the atria. 
     At step  73  atrial depolarization is detected in one or more of the locations of the catheter electrodes. 
     Control now proceeds to decision step  75 , where it is determined if concurrent ventricular depolarization was present concurrently with the atrial depolarization by reference to the above-mentioned icon. If the determination at decision step  75  is affirmative, then control proceeds to step  77 . The state of the icon constitutes the operator that the detection of atrial depolarization may not be reliable. The icon thus alerts the operator to the possibility that the detection of atrial depolarization may be a false is a suspect atrial activation, i.e., a false annotation event, and that far-field ventricular activity may be responsible. 
     If the determination at decision step  75  is negative, then control proceeds to step  79 . The detection of atrial depolarization is considered to be valid, and a local activation time of the location in which the atrial depolarization was detected is noted. There is no concern for VFF detection. 
     After performing step  77  or step  79  control returns to step  67  to iterate the procedure. 
     It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.