Detecting ventricular activity using unipolar and bipolar signals

Abstract

This invention is entitled "Detection of Ventricular Activity Using Unipolar and Bipolar Signals". The invention relates to a method comprising receiving a bipolar signal sensed by a pair of electrodes at a location in a patient's heart; receiving a unipolar signal sensed by the electrodes at that location in the heart; calculating the derivative of the received bipolar signal; calculating the derivative of the received unipolar signal; evaluating the ratio between the derivative of the bipolar signal and the derivative of the unipolar signal at a local minimum of the derivative of the unipolar signal; and indicating ventricular activity when this ratio is less than a preset threshold ratio.

Description

TECHNICAL FIELD

[0001] The present invention relates generally to electrophysiological signals, and in particular to a method for assessing electrical propagation within a heart. BACKGROUND

[0002] Prior patent literature has proposed recording unipolar and bipolar electrical signals with respect to a heart. For example, U.S. Patent Application Publication 2018 / 0042505 describes a method that includes receiving a bipolar signal from a pair of electrodes in proximity to a myocardium of a human subject, and receiving a unipolar signal from one of the pair of electrodes. The method further includes delineating a window of interest (WOI) of the unipolar signal and the bipolar signal, computing a local unipolar minimum derivative of the unipolar signal and a time of occurrence of the local unipolar minimum derivative within the WOI, and computing a bipolar derivative of the bipolar signal at the time of occurrence within the WOI. The method further includes evaluating a ratio of the bipolar derivative to the local unipolar minimum derivative, and designating the time of occurrence as an activation time of the myocardium when the ratio is greater than a preset threshold ratio, counting a number of activation times and classifying the unipolar signal according to the number.

[0003] As another example, U.S. Patent Application Publication 2015 / 0208938 describes a bipolar electrogram and a unipolar electrogram recorded from electrodes of a probe and differentiated with respect to time. A peak is identified in the differentiated bipolar electrogram. An activity window is defined that includes bipolar activity about the peak. A negative extremum in the differentiated unipolar electrogram within the activity window is reported as a unipolar activation onset. In one aspect, a mark is selected from candidate minima in the differentiated unipolar electrogram within the activity window by excluding candidate minima that fail to associate with activity in the bipolar electrogram.

[0004] U.S. Patent Application Publication 2015 / 0208942 describes a diagnostic cardiac catheterization that includes recording a bipolar electrogram and a unipolar electrogram from an electrode on a catheter at a location in a heart, and defining a window of interest in which a rate of change of potential of the bipolar electrogram exceeds a predetermined value. A mark is established in the unipolar electrogram, where the mark represents a maximum rate of change of potential of the unipolar electrogram within the window of interest. A quality value is assigned to the mark, and a 3-dimensional map of a portion of the heart including its mark and its quality value is generated.

[0005] U.S. Patent Application Publication 2013 / 0281870 describes a method for characterizing electrocardiograms, the method including receiving a first unipolar signal from a first location of a heart and receiving a second unipolar signal from a second location of the heart. A bipolar signal is generated from the first unipolar signal and the second unipolar signal, and the bipolar signal is analyzed to delineate a time period during which a bipolar complex is generated at the first location and the second location. The method further includes analyzing the first unipolar signal over the time period to determine an activation time of the first location. SUMMARY

[0006] Exemplary embodiments of the invention described herein provide a method including receiving a bipolar signal sensed by a pair of electrodes at a location in a heart of a patient. A unipolar signal is received, the unipolar signal being sensed by an electrode at the location in the heart. A derivative of the received bipolar signal is calculated. A derivative of the received unipolar signal is calculated. A ratio between the derivative of the bipolar signal and the derivative of the unipolar signal at a local minimum of the derivative of the unipolar signal is evaluated. An occurrence of ventricular activity is indicated when the ratio is less than a preset threshold ratio.

[0007] In some exemplary embodiments, receiving the bipolar signal includes receiving a plurality of bipolar signals from a plurality of pairs of electrodes of a multi-electrode catheter, and further including comparing a time difference between the plurality of bipolar signals, and indicating the occurrence of ventricular activity when the time difference is less than a predetermined value.

[0008] In some exemplary embodiments, receiving the unipolar signal includes receiving a plurality of unipolar signals from a plurality of electrodes of a multi-electrode catheter, and the method further includes indicating the occurrence of ventricular activity if a time difference between the unipolar signals is less than a predetermined value.

[0009] In one exemplary embodiment, receiving the unipolar signal includes receiving the unipolar signal from one of the pair of electrodes.

[0010] In another exemplary embodiment, calculating the ratio includes defining a time interval including a window of interest and calculating the ratio over the window of interest.

[0011] In some exemplary embodiments, the method further includes alerting a user of the indication of the occurrence of ventricular activity.

[0012] In some exemplary embodiments, the method further includes presenting the bipolar signal to a user with an annotation on the bipolar signal indicating the ventricular activity.

[0013] In other exemplary embodiments, the method further includes analyzing consecutive bipolar signals in time, and indicating the occurrence of ventricular activity only when the ratio remains less than the preset threshold ratio for at least a predetermined duration of time.

[0014] According to an exemplary embodiment of the present invention, an apparatus including an interface and a processor is further provided. The interface is configured to receive a bipolar signal from a pair of electrodes placed at a location in the heart of a patient, and to receive a unipolar signal from an electrode placed at the same location in the heart. The processor is configured to: (a) calculate the derivative of the received bipolar signal, (b) calculate the derivative of the received unipolar signal, (c) evaluate the ratio between the derivative of the bipolar signal and the derivative of the unipolar signal at a local minimum of the derivative of the unipolar signal, and (d) indicate the occurrence of ventricular activity when the ratio is less than a preset threshold ratio.

[0015] This disclosure will be more fully understood through the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, wherein: Attached Figure Description

[0016] The invention will be more fully understood from the following detailed description of embodiments thereof, taken in conjunction with the accompanying drawings, wherein:

[0017] Figure 1 This is a schematic diagram of a catheter-based electrophysiological (EP) mapping system according to an exemplary embodiment of the present invention;

[0018] Figure 2 This is a use of an exemplary embodiment of the present invention. Figure 1 The system records bipolar and unipolar electrocardiogram (ECG) signals, and a graph showing the calculated ratio of unipolar ECG signals to bipolar ECG signals; and

[0019] Figure 3 This is a flowchart schematically illustrating a method and algorithm for detecting far-field ventricular activity according to an exemplary embodiment of the present invention. Detailed Implementation

[0020] SUMMARY

[0021] Electrophysiological (EP) signals acquired from the heart using a catheter are typically a combination of near-field and far-field bioelectrical signals. However, in clinical practice, near-field signals are usually more prominent. Furthermore, some far-field signals are considered interferences that can impair near-field sensing signals. For example, when acquiring signals from a catheter positioned in the atrium of the heart, physicians need to know when ventricular far-field activity interferes with near-field signals.

[0022] In the context of this invention, near-field bioelectrical signals are signals received from cardiac tissue at the local contact point between the diagnostic electrode and the tissue. Far-field bioelectrical signals are signals from regions far from the contacted tissue area. Typically, such far-field bioelectrical signals propagate via conduction through the blood and are sensed by the diagnostic electrode of the catheter, while the electrode acquires near-field signals through contact with the tissue.

[0023] The exemplary embodiments of the invention described below provide methods and apparatus for detecting transient far-field ventricular activity. In some exemplary embodiments, the processor receives a bipolar signal sensed by a pair of electrodes of a catheter placed in contact with the tissue being diagnosed (such as tissue of the left atrium of the heart), and a unipolar signal sensed by electrodes of the same catheter or another catheter placed in contact with the heart tissue.

[0024] Ventricular activity is typically represented by sharp changes in unipolar signals and by gentler changes in bipolar signals. Therefore, if the slope of a unipolar signal is large but the slope of a bipolar signal is small, this behavior may be caused by transient far-field ventricular activity.

[0025] In some exemplary embodiments, the processor first calculates the derivatives of the received bipolar and unipolar signals, and then calculates the ratio between the derivatives of the bipolar and unipolar signals. By comparing the calculated ratio with a preset threshold, for example, when the ratio is below a preset threshold ratio, the processor identifies the occurrence of interference with far-field ventricular activity. The processor then indicates the occurrence of ventricular activity to the user. In one exemplary embodiment, the ratio is a dynamic ratio that the processor can update based on, for example, the noise level in the acquired signal.

[0026] In some exemplary embodiments, the electrode sensing the unipolar signal is one of the electrodes in the electrode pair described above. In other exemplary embodiments, one or more ECG surface leads are used to receive the unipolar signal.

[0027] In some exemplary embodiments, the processor defines a time interval including a window of interest and calculates the ratio of the received unipolar signal to the bipolar signal within the window of interest. Alternatively or otherwise, the processor calculates the ratio of the slope of the received unipolar signal to the slope of the bipolar signal within the window of interest.

[0028] In some cases, local bioelectrical signals can exhibit similarity to far-field bioelectrical signals. In some exemplary embodiments, to distinguish local activity from far-field activity, the processor modulates signals from multi-electrode catheters (such as PentaRay)... TMThe bioelectrical signals from multiple electrode pairs of the catheter (manufactured by Biosense Webster) were analyzed. If the signal was generated due to far-field activity, the signal timing should be similar across different electrode pairs; however, if the signal was generated due to localized activity, the signal would be temporally dispersed, for example, exceeding predetermined values ​​independently of each other in time.

[0029] In some exemplary embodiments, the processor is further configured to alert or flag the physician for detected ventricular activity. The system can further utilize this process to select or exclude beats from the acquisition.

[0030] The method for detecting ventricular activity disclosed in this invention relies on the following proposal: ventricular activity usually occurs if a large unipolar signal or a large change in the sensed unipolar signal is detected, while small bipolar signals are present, or small changes are present in the bipolar signals, or more quantitatively, small changes are present, if the ratio of either pair of signals exceeds a given threshold.

[0031] In one exemplary embodiment, the processor analyzes the continuous bipolar signals in a timely manner, and if the ratio between the derivative of the bipolar signal and the derivative of at least one of the corresponding unipolar signals remains less than a preset threshold ratio for at least a predetermined duration, the processor indicates the occurrence of ventricular activity, and only in this case.

[0032] Typically, processors are programmed with software containing specific algorithms that enable them to perform each of the processor-related steps and functions listed above.

[0033] The method for detecting ventricular activity disclosed in this invention can enhance the value of diagnostic catheterization by enabling physicians to discard damaged bioelectric sensing signals.

[0034] System Description

[0035] Figure 1 This is a schematic diagram of a catheter-based electrophysiological (EP) mapping system 21 according to an exemplary embodiment of the present invention. Figure 1 The illustration shows a physician 27 using an electroanatomical mapping catheter 29 to perform electroanatomical mapping of the heart 23 of a patient 25. The mapping catheter 29 includes one or more arms 20 at its distal end, each of which is coupled to a bipolar electrode 22 including adjacent electrodes 22a and 22b.

[0036] During the mapping procedure, the position of electrode 22 is tracked when it is located within the patient's heart 23. For this purpose, an electrical signal is transmitted between electrode 22 and external electrodes 24. For example, three external electrodes 24 may be coupled to the patient's chest, and another three external electrodes may be coupled to the patient's back. (For ease of illustration,) Figure 1 Only one external electrode is shown.

[0037] Based on the signals and given the known locations of the electrodes 24 on the patient's body, the processor 28 calculates the estimated location of each electrode 22 within the patient's heart 23. Corresponding electrophysiological data, such as intracardiac ECG traces, are additionally acquired from the tissues of the heart 23 using the electrodes 22. Therefore, the processor can associate any given signal (such as an electrophysiological signal) received from the electrodes 22 with the location of the acquired signal. The processor 28 receives the generated signals via an electrical interface 35 and uses the information contained in these signals to construct an electrophysiological mapping 31 and an ECG trace 40, and presents these signals on a display 26.

[0038] Processor 28 typically includes a general-purpose computer with software programmed to perform the functions described herein. This software can be downloaded to the computer electronically via a network, or alternatively or additionally, it can be located and / or stored on a non-transitory tangible medium (such as magnetic storage, optical storage, or electronic storage). Specifically, processor 28 runs specialized algorithms as disclosed herein (including...). Figure 3 (The method shown in the figure) The dedicated algorithm enables processor 28 to perform the disclosed steps, as further described below.

[0039] Figure 1 The exemplary illustrations shown are chosen solely for clarity of concept. Other types of electrophysiological sensing catheter geometries may also be employed, such as... The catheter (manufactured by Biosense-Webster Inc., Irvine, California). Additionally, a contact sensor may be fitted at the distal end of the mapping catheter 29 and transmit data indicating the physical quality of contact between the electrodes and tissue. In one exemplary embodiment, if the physical contact quality of one or more electrodes 22 is indicated as poor, their measurements are discarded, and if the contact quality of other electrodes is indicated as sufficient, their measurements are considered valid.

[0040] Detecting ventricular activity using unipolar and bipolar signals

[0041] Figure 2 This is a use of an exemplary embodiment of the present invention. Figure 1The system 21 records a graph of bipolar ECG signals (60) and unipolar ECG signals (62), and a graph of the corresponding calculated ratio (64) of the unipolar ECG signal to the bipolar ECG signal. The bipolar signal 60 is received from a pair of electrodes 22 of the catheter 29, and the unipolar signal 62 is received from a selected electrode of the electrode pair. The signals shown are received in time interval 50, in which two windows of interest (WOIs) 55 are shown, all defined by the processor 28. The processor 28 calculates the ratio 64 of the bipolar derivative signal to the bipolar derivative signal within the WOI 55 and compares the calculated ratio 64 with a preset threshold (or dynamic threshold) 67 to identify far-field ventricular activity. In the exemplary embodiment shown, the processor 28 indicates the occurrence of far-field ventricular activity (i.e., when the ratio 64 is below the threshold 67) by annotations 61, 63, and 65 overlaid on the ratio graph (64). However, additional graphics methods and actions (such as marking signals within the WOI for future processing) employed by the processor 28 are possible.

[0042] Figure 3 This is a flowchart schematically illustrating a method and algorithm for detecting far-field ventricular activity according to an exemplary embodiment of the present invention. According to the presented exemplary embodiment, the algorithm executes a process that begins at a data receiving step 70 by using processor 28 to receive bipolar and unipolar signals from catheter 29. Next, at a data selection step 72, processor 28 defines a time interval 50 including WOI 55. Then, at a multi-electrode pair ratio calculation step 74, processor 28 calculates a ratio 64 of the bipolar derivative signal to the unipolar derivative signal. At a checking step 76, processor 28 checks each electrode pair to determine whether the ratio 64 is below a preset threshold 67. When the answer for at least a portion of the considered electrode pairs is "no", the process returns to step 70 to obtain new signals. When the answer for a sufficient portion of the electrode pairs is "yes", the process continues.

[0043] To distinguish between local bioelectrical activity and far-field bioelectrical activity, the processor compares the timing of the effective fractions of the bioelectrical signals. If, at check step 78, the analysis shows that the signal timing is different across different electrode pairs, and the processor determines that the signal is generated due to local activity, the process returns to step 70 to collect a new signal.

[0044] If the time difference between the signals is less than a predetermined value, the processor 28 determines that the signal is generated due to transient far-field activity and indicates the detected ventricular activity, for example, by executing annotations 61, 63, and 65 in the ventricular activity indication step 80. Finally, using various possible audiovisual devices, the processor 28 alerts the physician 82 to the detected ventricular activity. In some embodiments, the processor compares the received different monopolar signals, and if the processor finds that the time difference between the different monopolar signals is less than a predetermined duration, the processor indicates the occurrence of ventricular activity.

[0045] Figure 3 The exemplary flowchart shown is chosen solely for conceptual clarity. This embodiment may also include additional steps in the algorithm, such as receiving multiple bipolar and monopolar ECG signals, and receiving an indication of the degree of physical contact between the electrodes and the tissue being diagnosed from a contact force sensor. This step, and other possible steps, have been intentionally omitted from this disclosure to provide a more simplified flowchart.

[0046] While the exemplary embodiments described herein primarily relate to cardiac diagnostic applications, the methods and systems described herein can also be used in other medical applications, such as in defibrillators and pacemakers.

[0047] It should be understood that the exemplary embodiments described above are cited by way of example, and the present invention is not limited to the specific contents shown and described above. Rather, the scope of the present invention includes combinations and sub-combinations of the various features described above, as well as variations and modifications thereof, which should be apparent to those skilled in the art upon reading the above description, and which are not disclosed in the prior art.

Claims

1. A method for automatically detecting far-field ventricular activity using unipolar and bipolar signals, the method comprising: It receives bipolar signals sensed by a pair of electrodes located in the patient's heart; Receives a unipolar signal sensed by an electrode at the location in the heart; Calculate the derivative of the received bipolar signal; Calculate the derivative of the received unipolar signal; Evaluate the ratio between the derivative of the bipolar signal and the derivative of the unipolar signal; Receiving the bipolar signals includes receiving multiple bipolar signals from multiple electrode pairs of the multi-electrode conduit, and includes comparing the time differences between the multiple bipolar signals. When the ratio is less than a preset threshold ratio and the time difference is less than a predetermined value, it indicates the occurrence of far-field ventricular activity.

2. The method of claim 1, wherein receiving the unipolar signal comprises receiving a plurality of unipolar signals from a plurality of electrodes of a multi-electrode catheter, and comprises indicating the occurrence of far-field ventricular activity if the time difference between the unipolar signals is less than a predetermined value.

3. The method of claim 1, wherein receiving the unipolar signal comprises receiving the unipolar signal from one of the pair of electrodes.

4. The method of claim 1, wherein calculating the ratio includes defining a time interval including a window of interest and calculating the ratio within the window of interest.

5. The method of claim 1, further comprising an indication to alert the user to the occurrence of the far-field ventricular activity.

6. The method of claim 1, further comprising presenting the bipolar signal to a user, the bipolar signal having annotations indicating the far-field ventricular activity.

7. The method of claim 1, further comprising timely analysis of the continuous bipolar signal, and indicating the occurrence of the far-field ventricular activity only when the ratio remains less than a preset threshold ratio for at least a predetermined duration.

8. An apparatus for automatically detecting far-field ventricular activity using unipolar and bipolar signals, the apparatus comprising: An interface configured to receive bipolar signals from a pair of electrodes placed at a location in the patient's heart, and to receive unipolar signals from the electrodes placed at the location in the heart. as well as Processor, the processor being configured to: Calculate the derivative of the received bipolar signal; Calculate the derivative of the received unipolar signal; Evaluate the ratio between the derivative of the bipolar signal and the derivative of the unipolar signal; Receiving the bipolar signal includes receiving multiple bipolar signals from multiple electrode pairs of a multi-electrode conduit, and includes comparing the time differences between the multiple bipolar signals; and When the ratio is less than a preset threshold ratio and the time difference is less than a predetermined value, it indicates the occurrence of far-field ventricular activity.

9. The apparatus of claim 8, wherein the processor is configured to receive the unipolar signal by receiving a plurality of unipolar signals from a plurality of electrodes of a multi-electrode catheter, and to indicate the occurrence of far-field ventricular activity if the time difference between the unipolar signals is less than a predetermined value.

10. The apparatus of claim 8, wherein the processor is configured to receive a unipolar signal from one of the pair of electrodes.

11. The apparatus of claim 8, wherein the processor is configured to define a time interval including a window of interest and to calculate the ratio of the unipolar signal to the bipolar signal within the window of interest.

12. The apparatus of claim 8, wherein the processor is further configured to alert the user to an indication of the occurrence of the far-field ventricular activity.

13. The apparatus of claim 8, wherein the processor is further configured to present the bipolar signal to a user, the bipolar signal having annotations indicating far-field ventricular activity.

14. The apparatus of claim 8, wherein the processor is further configured to analyze the continuous bipolar signal in a timely manner and indicate the occurrence of the far-field ventricular activity only when the ratio remains less than a preset threshold ratio for at least a predetermined duration.

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