Patent ID: 12226219

DETAILED DESCRIPTION

The detailed description set forth below in connection with the appended drawings, where like numerals reference like elements, are intended as a description of various embodiments of the present disclosure and are not intended to represent the only embodiments. Each embodiment described in this disclosure is provided merely as an example or illustration and should not be construed as precluding other embodiments. The illustrative examples provided herein are not intended to be exhaustive or to limit the disclosure to the precise forms disclosed.

In the following description, specific details are set forth to provide a thorough understanding of exemplary embodiments of the present disclosure. It will be apparent to one skilled in the art, however, that the embodiments disclosed herein may be practiced without embodying all of the specific details. In some instances, well-known process steps have not been described in detail in order not to unnecessarily obscure various aspects of the present disclosure. Further, it will be appreciated that embodiments of the present disclosure may employ any combination of features described herein.

Wearable Cardioverter Defibrillators (WCDs) are worn by patients at risk for sudden cardiac arrest and other potential heart conditions. Some patients may be at risk to develop sustained ventricular arrhythmias and sudden death. Nonsustained ventricular tachycardia (NSVT) is usually asymptomatic and most often diagnosed during cardiac monitoring; NSVT is also a potential marker for the development of sustained ventricular arrhythmias. NSVT may occur frequently while a patient is sleeping and the WCD system, or other heart rate monitoring system, may not detect or recognize the presence of NSVT.

In some instances, sensors signals may experience artifacts from patient motion or from the environment, as WCD patients are often conscious, ambulatory people living normal lives. Therefore, a short NSVT is not typically recognized and stored for later review because artifacts may cause too many short-lived high-rate signal rhythms. The disclosure herein describes a method to detect NSVT and store the ECG signals for clinical review and optimal patient management.

Morphology information may screen noise episodes out from real episodes of NSVT. If detected QRS complexes have a consistent morphology, or shape, then the signal likely does not contain much noise. Noise would make the complexes appear different or varied. Episode determination becomes more specific by factoring morphology. The specific factoring may identify shorter runs of VT, or if longer durations are allowed, episodes could be opened with greater confidence of avoiding noise. Using consistent morphology as a factor in episode determination can also be used to store monomorphic VT episodes as well as SVT episodes. Monomorphic VT episodes typically have a greater QRS width than SVT episodes.

For exemplary purposes only, the embodiments herein will be described in reference to a WCD system and a defibrillator. However, the methodology for detecting and storing an NSVT episode can be performed by a WCD or any wearable medical monitoring device that monitors a patient's ECG.

FIG.1illustrates a system100with a patient102wearing an example of a WCD system104according to embodiments described herein. In some embodiments, the WCD system104may include one or more communication devices106, a support structure110, and an external defibrillator108connected to two or more defibrillation electrodes114,116, among other components.

The support structure110may be worn by the patient102. The patient102may be ambulatory, meaning the patient102can walk around and is not necessarily bed-ridden while wearing the wearable portion of the WCD system104. While the patient102may be considered a “user” of the WCD system104, this is not a requirement. For instance, a user of the WCD system104may also be a clinician such as a doctor, nurse, emergency medical technician (EMT) or other similarly tasked individual or group of individuals. In some cases, a user may even be a bystander. The particular context of these and other related terms within this description should be interpreted accordingly.

In some embodiments, the support structure110may include a vest, shirt, series of straps, or other system enabling the patient102to carry at least a portion of the WCD system104on the patient's body. In some embodiments, the support structure110may comprise a single component. For example, the support structure110may comprise a vest or shirt that properly locates the WCD system104on a torso112of the patient102. The single component of the support structure110may additionally carry or couple to all of the various components of the WCD system104.

In other embodiments, the support structure110may comprise multiple components. For example, the support structure110may include a first component resting on a patient's shoulders. The first component may properly locate a series of defibrillation electrodes114,116on the torso112of the patient102. A second component may rest more towards a patient's hips, whereby the second component may be positioned such that the patient's hips support the heavier components of the WCD system104. In some embodiments, the heavier components of the WCD system104may be carried via a shoulder strap or may be kept close to the patient102such as in a cart, bag, stroller, wheelchair, or other vehicle.

The external defibrillator108may be coupled to the support structure110or may be carried remotely from the patient102. The external defibrillator108may be triggered to deliver an electric shock to the patient102when patient102wears the WCD system104. For example, if certain thresholds are exceeded or met, the external defibrillator108may engage and deliver a shock to the patient102.

The defibrillation electrodes114,116can be configured to be worn by patient102in a number of ways. For instance, the defibrillator108and the defibrillation electrodes114,116can be coupled to the support structure110directly or indirectly. For example, the support structure110can be configured to be worn by the patient102to maintain at least one of the electrodes114,116on the body of the patient102, while the patient102is moving around, etc. The electrodes114,116can be thus maintained on the torso112by being attached to the skin of patient102, simply pressed against the skin directly or through garments, etc. In some embodiments, the electrodes114,116are not necessarily pressed against the skin but becomes biased that way upon sensing a condition that could merit intervention by the WCD system104. In addition, many of the components of defibrillator108can be considered coupled to support structure110directly, or indirectly via at least one of defibrillation electrodes114,116.

The WCD system104may defibrillate the patient102by delivering an electrical charge, pulse, or shock111to the patient102through a series of electrodes114,116positioned on the torso112. For example, when defibrillation electrodes114,116are in good electrical contact with the torso112of patient102, the defibrillator108can administer, via electrodes114,116, a brief, strong electric pulse111through the body. The pulse111is also known as shock, defibrillation shock, therapy, electrotherapy, therapy shock, etc. The pulse111is intended to go through and restart heart122, in an effort to save the life of patient102. The pulse111can further include one or more pacing pulses of lesser magnitude to pace heart122if needed. The electrodes114,116may be electrically coupled to the external defibrillator108via a series of electrode leads118. The defibrillator108may administer an electric shock111to the body of the patient102when the defibrillation electrodes114,116are in good electrical contact with the torso112of patient102. In some embodiments, devices (not shown) proximate the electrodes114,116may emit a conductive fluid to encourage electrical contact between the patient102and the electrodes114,116.

In some embodiments, the WCD system104may also include either an external or internal monitoring device or some combination thereof.FIG.1displays an external monitoring device124which may also be known as an outside monitoring device. The monitoring device124may monitor at least one local parameter. Local parameters may include a physical state of the patient102such as ECG, movement, heartrate, pulse, temperature, and the like. Local parameters may also include a parameter of the WCD104, environmental parameters, or the like. The monitoring device124may be physically coupled to the support structure110or may be proximate the support structure110. In either location, the monitoring device124is communicatively coupled with other components of the WCD104.

For some of these parameters, the device124may include one or more sensors or transducers. Each one of such sensors can be configured to sense a parameter of the patient102, and to render an input responsive to the sensed parameter. In some embodiments, the input is quantitative, such as values of a sensed parameter; in other embodiments, the input is qualitative, such as informing whether or not a threshold is crossed. In some instances, these inputs about the patient102are also referred to herein as patient physiological inputs and patient inputs. In some embodiments, a sensor can be construed more broadly, as encompassing many individual sensors.

In some embodiments, a communication device106may enable the patient102to interact with, and garnish data from, the WCD system104. The communication device106may enable a patient or third party to view patient data, dismiss a shock if the patient is still conscious, turn off an alarm, and otherwise engage with the WCD system104. In some embodiments, the communication device106may be a separable part of an external defibrillator108. For example, the communication device106may be a separate device coupled to the external defibrillator108. In some embodiments, the communication device106may be wired or wirelessly linked to the external defibrillator108and may be removable from the defibrillator108. In other embodiments, the communication device106may form an inseparable assembly and share internal components with the external defibrillator108. In some embodiments, the WCD system104may include more than one communication device106. For example, the defibrillator108may include components able to communicate to the patient and the WCD system104may include a separate communication device106remote form the defibrillator108.

In some embodiments, the communication device106may be communicatively coupled to an alert button128. The alert button128may be removably coupled to the support structure110. The patient102may couple the alert button128to the support structure110or may couple the alert button128to an article of clothing. The alert button128may have wired or wireless connection to the communication device106. In some embodiments, the alert button128may include a visual output, an audio output, and a user input. The visual output may include a light, such as an LED, a small screen, or some combination thereof. Likewise, the audio output may include one or more speakers. The output of the audio output may be loud enough to be heard over nominal background noise. In some embodiments, the audio output might have an adjustable volume range. In some embodiments, the alert button128may include a microphone. In still further embodiments, the alert button128may also include a haptic response.

In some embodiments, the defibrillator108may connect with one or more external devices126. For example, as shown inFIG.1, the defibrillator108may connect to various external devices126such as the cloud, a remote desktop, a laptop, a mobile device, or other external device using a network such as the Internet, local area networks, wide area networks, virtual private networks (VPN), other communication networks or channels, or any combination thereof.

In embodiments, one or more of the components of the exemplary WCD system104may be customized for the patient102. Customization may include a number of aspects including, but not limited to, fitting the support structure110to the torso112of patient102; baseline physiological parameters of patient102can be measured, such as the heart rate of patient102while resting, while walking, motion detector outputs while walking, etc. The measured values of such baseline physiological parameters can be used to customize the WCD system, in order to make its diagnoses more accurate, since patients' bodies differ from one another. Of course, such parameter values can be stored in a memory of the WCD system, and the like. Moreover, a programming interface can be made according to embodiments, which receives such measured values of baseline physiological parameters. Such a programming interface may input automatically in the WCD system these, along with other data.

FIG.2is a diagram displaying various components of an example external defibrillator108. The external defibrillator108may be an example of the defibrillator108described with reference toFIG.1. The components shown inFIG.2may be contained within a single unit or may be separated amongst two or more units in communication with each other. The defibrillator108may include a communication device106, processor202, memory204, defibrillation port208, and ECG port210, among other components. In some embodiments, the components are contained within a housing212or casing. The housing212may comprise a hard shell around the components or may comprise a softer shell for increased patient comfort.

The communication device106, processor202, memory204(including software/firmware code (SW)214), defibrillation port208, ECG port210, communication module216, measurement circuit218, monitoring device220, and energy storage module222may communicate, directly or indirectly, with one another via one or more buses224. The one or more buses224may allow data communication between the elements and/or modules of the defibrillator108.

The memory204may include random access memory (RAM), read only memory (ROM), flash RAM, and/or other types. The memory204may store computer-readable, computer-executable software/firmware code214including instructions that, when executed, cause the processor202to perform various functions (e.g., determine shock criteria, determine consciousness of patient, track patient parameters, establish electrode channels, determine noise levels in electrode readings, etc.). In some embodiments, the processor202may include an intelligent hardware device, e.g., a central processing unit (CPU), a microcontroller, an application-specific integrated circuit (ASIC), etc.

In some embodiments, the memory204can contain, among other things, the Basic Input-Output system (BIOS) which may control basic hardware and/or software operations such interactions and workings of the various components of the defibrillator108, and in some embodiments, components external to the defibrillator108. For example, the memory204may contain various modules to implement the workings of the defibrillator108and other aspects of the present disclosure.

In some embodiments, the defibrillator108may include a user interface206. The user interface406may be in addition to or part of the communication device106. The user interface406may display an ECG of the patient, a status of the defibrillator108, a status of a charge (e.g., a battery charge or an energy storage module), and the like.

In some embodiments, the defibrillator108may include a defibrillation port208. The defibrillation port208may comprise a socket, opening, or electrical connection in the housing212. In some instances, the defibrillation port208may include two or more nodes226,228. The two or more nodes226,228may accept two or more defibrillation electrodes (e.g., defibrillation electrodes114,116,FIG.1). The nodes226,228may provide an electrical connection between the defibrillation electrodes114,116and the defibrillator108. The defibrillation electrodes114,116may plug into the two or more nodes226,228via one or more leads (e.g., leads118), or, in some instances, the defibrillation electrodes114,116may be hardwired to the nodes226,228. Once an electrical connection is established between the defibrillation port208and the electrodes114,116, the defibrillator108may be able to deliver an electric shock to the patient102.

In some embodiments, the defibrillator108may include an ECG port210in the housing212. The ECG port210may accept one or more ECG electrodes230or ECG leads. In some instances, the ECG electrodes230sense a patient's ECG signal. For example, the ECG electrodes230may record electrical activity generated by heart muscle depolarization. The ECG electrodes230may utilize 4-leads to 12-leads or multichannel ECG, or the like. The ECG electrodes230may connect with the patient's skin.

In some embodiments, the defibrillator108may include a measurement circuit218. The measurement circuit218may be in communication with the ECG port210. For example, the measurement circuit218may receive physiological signals from ECG port210. The measurement circuit218may additionally or alternatively receive physiological signals via the defibrillation port208when defibrillation electrodes114,116are attached to the patient102. The measurement circuit218may determine a patient's ECG signal from a difference in voltage between the defibrillation electrodes114,116.

In some embodiments, the measurement circuit218may monitor the electrical connection between the defibrillation electrodes114,116and the skin of the patient102. For example, the measurement circuit218can detect impedance between electrodes114,116. The impedance may indicate the effective resistance of an electric circuit. An impedance calculation may determine when the electrodes114,116have a good electrical connection with the patient's body.

In some embodiments, the defibrillator108may include an internal monitoring device220within the housing212. The monitoring device220may monitor at least one local parameter. Local parameters may include physical state of the patient such as ECG, movement, heartrate, pulse, temperature, and the like. Local parameters may also include a parameter of the WCD system (e.g., WCD104,FIG.1), defibrillator108, environmental parameters, or the like.

In some embodiments, the WCD system104may include an internal monitoring device220and an external monitoring device (e.g., external monitoring device124). If both monitoring devices124,220are present, the monitoring devices124,220may work together to parse out specific parameters depending on position, location, and other factors. For example, the external monitoring device124may monitor environmental parameters while the internal monitoring device220may monitor patient and system parameters.

In some embodiments, the defibrillator108may include a power source232. The power source232may comprise a battery or battery pack, which may be rechargeable. In some instances, the power source232may comprise a series of different batteries to ensure the defibrillator108has power. For example, the power source232may include a series of rechargeable batteries as a prime power source and a series of non-rechargeable batteries as a secondary source. If the patient102is proximate an AC power source, such as when sitting down, sleeping, or the like, the power source232may include an AC override wherein the power source232draws power from the AC source.

In some embodiments, the defibrillator108may include an energy storage module222. The energy storage module222may store electrical energy in preparation or anticipation of providing a sudden discharge of electrical energy to the patient. In some embodiments, the energy storage module222may have its own power source and/or battery pack. In other embodiments, the energy storage module222may pull power from the power source232. In still further embodiments, the energy storage module222may include one or more capacitors234. The one or more capacitors234may store an electrical charge, which may be administered to the patient. The processor202may be communicatively coupled to the energy storage module222to trigger the amount and timing of electrical energy to provide to the defibrillation port208and, subsequently, the patient102.

In some embodiments, the defibrillator108may include a discharge circuit236. The discharge circuit236may control the energy stored in the energy storage module222. For example, the discharge circuit236may either electrical couple or decouple the energy storage module222to the defibrillation port208. The discharge circuit236may be communicatively coupled to the processor202to control when the energy storage module222and the defibrillation port208should or should not be coupled to either administer or prevent a charge from emitting from the defibrillator108. In some embodiments, the discharge circuit236may include on or more switches238. In further embodiments, the one or more switches238may include an H-bridge.

In some embodiments, the defibrillator108may include a communication module216. The communication module216may establish one or more communication links with either local hardware and/or software to the WCD system104and defibrillator108or to remote hardwire separate from the WCD system104. In some embodiments, the communication module216may include one or more antennas, processors, and the like. The communication module216may communicate wirelessly via radio frequency, electromagnetics, local area networks (LAN), wide area networks (WAN), virtual private networks (VPN), RFID, Bluetooth, cellular networks, and the like. The communication module216may facilitate communication of data and commands such as patient data, episode information, therapy attempted, CPR performance, system data, environmental data, and so on.

In some embodiments, the processor202may execute one or more modules. For example, the processor202may execute a detection module240and/or an action module242. The detection module240may be a logic device or algorithm to determine if any or a variety of thresholds are exceeded which may require action of the defibrillator108. For example, the detection module240may receive and interpret all of the signals from the ECG port210, the defibrillation port208, the monitoring device220, an external monitoring device, and the like. The detection module240may process the information to ensure the patient is still conscious and healthy. If any parameter indicates the patient102may be experiencing distress or indicating a cardiac episode, the detection module240may activate the action module242.

The action module242may receive data from the detection module240and perform a series of actions. For example, an episode may merely be a loss of batter power at the power source232or the energy storage module222, or one or more electrodes (e.g., ECG electrodes, defibrillation electrodes) may have lost connection. In such instances, the action module242may trigger an alert to the patient or to an outside source of the present situation. This may include activating an alert module. If an episode is a health risk, such as a cardiac event, the action module242may begin a series of steps. This may include issuing a warning to the patient, issuing a warning to a third party, priming the energy storage module222for defibrillation, releasing one or more conductive fluids proximate defibrillation electrodes114,116, and the like.

FIG.3is a diagram of sample embodiments of components of a WCD system300according to exemplary embodiments. The WCD system300may be an example of the WCD system104describe with reference toFIG.1. In some embodiments, the WCD system300may include a support structure302comprising a vest-like wearable garment. In some embodiments, the support structure302has a back side304, and a front side306that closes in front of the chest of the patient.

In some embodiments, the WCD system300may also include an external defibrillator308. The external defibrillator308may be an example of the defibrillator108describe with reference toFIGS.1and2. As illustrated,FIG.3does not show any support for the external defibrillator308, but as discussed, the defibrillator308may be carried in a purse, on a belt, by a strap over the shoulder, and the like as discussed previously. One or more wires310may connect the external defibrillator308to one or more electrodes312,314,316. Of the connected electrodes, electrodes312,314are defibrillation electrodes, and electrodes316are ECG sensing electrodes.

The support structure302is worn by the patient to maintain electrodes312,314,316on a body of the patient. For example, the back-defibrillation electrodes314are maintained in pockets318. In some embodiments, the inside of pockets318may comprise loose netting, so that the electrodes314can contact the back of the patient. In some instances, a conductive fluid may be deployed to increase connectivity. Additionally, in some embodiments, sensing electrodes316are maintained in positions that surround the patient's torso, for sensing ECG signals and/or the impedance of the patient.

In some instances, the ECG signals in a WCD system300may comprise too much electrical noise to be useful. To ameliorate the problem, multiple ECG sensing electrodes316are provided, for presenting many options to the processor (202. The multiple ECG sensing electrodes316provide different vectors for sensing the ECG signal of the patient.

FIG.4is a conceptual diagram illustrating how multiple electrodes of a WCD system may defined a multi-vector embodiment for sensing ECG signals along different vectors according to various exemplary embodiments. A cross-section of a body of a patient422having a heart424is illustrated. InFIG.4, the patient422is viewed from the top looking down and the plane ofFIG.4intersects patient422proximate the torso of the patient422.

In some embodiments, four ECG sensing electrodes E1, E2, E3, E4are maintained on the torso of patient482, and have respective wire leads461,462,463,464. The electrodes E1, E2, E3, E4that surround the torso may be similar to the sensing electrodes316as described with reference toFIG.3.

Any pair of these four ECG sensing electrodes E1, E2, E3, E4defines a vector, along which an ECG signal may be sensed and, in some instances, measured. As such, electrodes E1, E2, E3, E4define six vectors471,472,473,474,475,476.

These vectors471,472,473,474,475,476define channels A, B, C, D, E, F respectively. ECG signals401,402,403,404,405,406may thus be sensed and/or measured from channels A, B, C, D, E, F, respectively, and in particular from the appropriate pairings of wire leads461,462,463,464for each channel.

As shownFIG.4, electrodes E1, E2, E3, E4are drawn on the same plane for simplicity, while in actuality the electrodes E1, E2, E3, E4may not be positioned on the same plane. Accordingly, vectors471,472,473,474,475,476are not necessarily on the same plane, either. Further, in some embodiments, the WCD system averages a value of the voltages of all four electrodes electronically and then determines the voltage of each electrode relative to the average value. Conceptually, this average value is the signal at some point in space in between the electrodes E1, E2, E3, E4. It continuously changes its virtual position based on the voltages of the electrodes E1, E2, E3, E4. In some embodiments, this virtual point is referred to herein as the M Central Terminal (MCT). Relative to the MCT, there are four resulting vectors: E1C=E1−CM, E2C=E2−CM, E3C=E3−CM and E4C=E4−CM, where CM is the average voltage value. In some embodiments, the vectors are virtually formed by selecting a pair of these signals and subtracting one from the other. For example, E1C−E2C=(E1−CM)−(E2−CM)=E1−E2+(CM−CM)=E1−E2=E12. Although six vectors are described inFIG.4, a different number of vectors may be used depending on the number of ECG electrodes present in the system and the desired number of vectors (up to the number of vectors that can be derived from the number of electrodes).

In some embodiments, to make the shock/no-shock determination as accurate as possible, a WCD system may assess the best ECG signals401,402,403,404,405,406for rhythm analysis and interpretation. For example, ECG signals with the most noise may be ignored, discarded, or not considered, leaving the remaining ECG signals as candidates for the shock/no shock determination.

In other embodiments, the vectors may be aggregated to make a shock/no shock decision, and/or to determine the patient's heart rate and/or QRS widths. For example, in some embodiments the aggregation can be implemented as disclosed in U.S. Pat. No. 9,757,581 issued Sep. 12, 2017 entitled “WEARABLE CARDIOVERTER DEFIBRILLATOR COMPONENTS MAKING AGGREGATE SHOCK/NO SHOCK DETERMINATION FROM TWO OR MORE ECG SIGNALS,” which is incorporated herein by reference.

FIG.5is a block diagram illustrating components of one example of a defibrillator500. The defibrillator500may be an example of the defibrillator108described with reference toFIGS.1and2and defibrillator308described with reference toFIG.3. In this example, the defibrillator500has detection module502and an alert module504. The detection module502may further include an NSVT module506.

In some embodiments, the NSVT module506may diagnose potential NSVT episodes and store episodic information for later review. For example, shorter runs of detected VT are analyzed to determine if there is a noisy signal. If there is noise in the signal, the episode is deemed a noise episode and is not saved. However, if the signal is validated, the NSVT module506flags a potential NSVT episode and the information is stored for later review.

In some embodiments, the NSVT module506may utilize morphonology information to ascertain the difference between noise and a potential cardiac event. Noisy signals typically have an erratic QRS complex as the noise in the signal affects the appearance of the complexes. However, QRS complexes with a consistent morphology or shape typically do not contain much noise. Using consistent morphology as a factor, the NSVT module506is able to more rigorously filter out potential cardiac episodes from noisy signals. The NSVT module506may open episodes for shorter VT occurrences, or if longer durations are allowed, the NSVT module506may open longer episodes with greater confidence of avoiding noise.

In some embodiments, the NSVT module506may also flag and store potential monomorphic VT episodes or SVT episodes. For some patients, monomorphic VT episodes may have a greater QRS width than SVT episodes, which the NSVT module506may factor into calculations. In some instances, a morphology analysis may screen out disorganized rhythms such as VF and polymorphic VT as potential NSVT but other portions of a shock decision algorithm may be used by the detection module502to detect and make a shock decision.

In some embodiments, the NSVT module506may analyze QRS morphology by generating a QRS template. For example, during a normal rhythm, the NSVT module506may generate and store a template.FIG.9is an example of a normal template formed during normal sinus rhythm at a lower heartrate.FIG.10Aillustrates an NSR heartrate graph used to calculate the template inFIG.9.

Referring back toFIG.5, when a high or abnormal heartrate tachycardia begins, the NSVT module506may compare incoming QRS complexes to the QRS template. If the correlation is high, the NSVT module506may flag the incident as SVT. If the incoming QRS complexes have a low to zero correlation to the normal template but the QRS complexes are correlating to each other, the NSVT module506flags the episode as a potential NSVT episode.

In some embodiments, the NSVT module506may compare incoming QRS complexes by calculating a Feature Correlation Coefficient shown below:

F⁢C⁢C=(8⁢∑i-18⁢xi⁢yi-(∑i=18⁢xi)⁢(∑i=18⁢yi))2(8⁢∑i=18⁢xi2-(∑i=18⁢xi)2)⁢(8⁢∑i=18⁢yi2-(∑i=18⁢yi)2)
The FCC may be calculated between two consecutive QRS complexes to determine the correlation.FIG.10Bshows the calculated FCC correlation for one example. In some embodiments, the NSVT module506may form a temporary NSVT template using the first few incoming QRS complexes and then calculate the FCC. As shown inFIG.6, the temporary template may be formed as a median or mean value of multiple waveforms. The exemplary waveform shown inFIG.6is a template waveform from median values. In further embodiments, the FCC to a normal template may be low but consistent.

In other embodiments, another method of detecting morphology consistency uses the QRS organization metric described in U.S. patent application Ser. No. 16/554,410 filed Aug. 28, 2019 with a request for non-publication. In these embodiments, the organization metric of the '410 application is similar to the FCC except that it uses the sum of the squared difference between the template and the incoming signal. An organization value of two (2) or more indicates a very clean signal. VF and polymorphic VT is generally less than one (1).

Analyzing the QRS morphology may help in flagging potential NSVT or other non-sustained VT episodes. The QRS morphology allows the NSVT module506to determine if the ECG signal is clear and absent of any extra noise. If there is no noise in the system but the signal is showing signs of heart distress such as an accelerated heart rate, the NSVT module506may store the information for later review. Table 1, shown below, illustrates several factors for storing a potential NSVT episode. In some embodiments, the NSVT module506will store an episode when one of the listed conditions is satisfied. In further embodiments, the NSVT module506will store episodic information when at least two conditions are satisfied.

TABLE 1Factors for Storing a Potential NSVT EpisodeSimilarStableSus-Similarto NSRtoHRtainedMor-Mor-RRSuddenSleepingCase(bpm)DurationphologyphologyIntervalsOnsetPostureNSVT>170>5 secYesNoYesYesYes/NoAnd<15 sec

In some embodiments, the sleeping status of the patient is a factor in storing potential NSVT episode information. For example, a standard patient wearing a WCD is ambulatory and may ascertain when an NSVT episode is occurring when the patient is awake. However, if the patient is sleeping, the patient may not feel a VT or NSVT event. Therefore, in some embodiments, the NSVT module506may be programmed to truncate NSVT detection based on a waking status of the patient. For example, the NSVT module506may run when the patient is sleeping. Sleeping may be detected by the supine position, time, a slowing heartrate, and the like. In other embodiments, a doctor or clinician may not want to rely on the patient's ability to detect and record NSVT modules and may have the NSVT module504continuously monitoring the patient.

In some embodiments, the NSVT module506may screen episodes to differentiate between actual episodes and noise by factoring in the stability of the interval between QRS complexes. Noise generally causes false QRS detections, which creates heartrate variability, or R-R variability. R is a point corresponding to the peak of the QRS complex of the ECG wave, and R-R is an interval between success R points. R-R intervals are considered stable if the difference between two consecutive R-R-intervals is less than 20 milliseconds.

In some embodiments, the NSVT module506may detect and record a potential sudden onset. For example, a sudden onset may occur when the HR suddenly changes more than 10% and the morphology is not similar to the normal QRS template. The NSVT may categorize the morphology as similar if the FFC calculation is greater than 0.9. VT may start with a sudden increase of HR. Similarly, NSVT may start with a sudden HR increase, with a stable R-R interval and similar incoming QRS morphology. However, in contrast to SVT, NSVT has a different QRS morphology to when compared to the NSR template. In contrast, when a gradual HR increase is present, the patient is likely experiencing sinus tachycardia when exercising.

FIGS.7A and7Bis an embodiment of R-R analysis. In the example shown,FIG.7Ashows a patient with consistent R-R intervals.FIG.7Bshows the difference between the R-R intervals.FIG.7Bshows the difference between R-R intervals to be less than 20 milliseconds. Therefore, the example shown is a situation where the ECG signal is clear, and the patient may be experiencing an episode NSVT. A standard monitoring device might not view this as an interval and might dismiss the interval as noise. However, by reviewing the R-R intervals and consistency rating, the NSVT module506detects a potential NSVT episode and stores it for later review by physicians.

In some embodiments, the NSVT module506may detect NSVT based on the sustained duration of VT. For example, if VT lasts between 5 seconds and 15 seconds, it is considered non-sustained VT (NSVT). As shown inFIG.8A, the VT episode is about 10.5 seconds, which indicates an NSVT episode. The circle inFIG.8Aindicates the QRS detection whereas the solid and dotted lines indicate ECG waveform and the R-wave detection threshold.FIG.8Brepresents the calculated FCC value using circles. As shown, the FCC value is above 0.9 indicating a lack of QRS morphology variability which indicates a clear signal and a high correlation to the template. The short duration of VT combined with the clear signal is indicative of an NSVT episode.

The action module504may store episode information for later use. In some embodiments, the action module504may also transmit the episode data. For example, if the defibrillator500is connected to the internet, the action module504may upload episode and data to a secure location for physician review. The action module504may also take other steps unrelated to an NSVT episode, for example, the action module504may issue patient alerts, initiate a shock to the patient, and the like.

FIG.11is a flow chart illustrating an example of a method1100for WCD systems, in accordance with various aspects of the present disclosure. For clarity, the method1000is described below with reference to aspects of one or more of the systems described herein.

At block1102, the method1100may process at least one electrocardiogram signal. For example, a defibrillator or other cardiac monitoring device may be in communication with at least two ECG electrodes. The at least one ECG electrode may be positioned to read a heartrate of a patient. The method1100may receive at least one signal from the ECG and process the signal. Processing the signal may include reading QRS impulses, heartrate, noise level, and the like.

At block1104, the method1100may diagnose or flag an episode based at least in part on the processing of the at least one ECG signal. For example, the method1100may analyze the ECG signal for an NSVT time duration or threshold and a QRS criterion. When the ECG signals satisfies both the time duration and the QRS criterion, the method100may save episodic information for later review as a potential NSVT episode. The time threshold may be brief. For example, the NSVT time threshold may be between 5 seconds and 15 seconds. In some embodiments, the method1100may use a QRS template as the QRS criterion. For example, in some embodiments, the method1100may use the first few QRS complexes to form a temporary QRS template. If the following QRS signals from the ECG signal match or substantially match the temporary QRS template, the method1100may determine the signal is free of noise and the patient is experiencing an NSVT episode. In other embodiments, the method1100may additionally or alternatively compare the incoming QRS complexes to the NSR QRS template. If the incoming complexes substantially match the NSR QRS template, the method1100may determine an SVT episode is potentially occurring. Regardless, the QRS stability ensures the method1100is receiving a clear signal.

In some embodiments, the method1100may flag an NSVT episode when the ECG signal exceeds a heart rate threshold and the NSVT time threshold. The heart rate threshold may be greater than 170 BPM. If the patient is experiencing a high heart rate for a short duration, this is categorized as nonsustained VT and the episodic information is saved for later review.

In some embodiments, the method1100may flag an NSVT episode by examining QRS complexes. For example, in some embodiments, the method1100may analyze the normal sinus rhythm (NSR) QRS complexes and develop an NSR QRS template (SeeFIG.9). If the NSR template does not match incoming QRS complexes, the method1100may determine that an event is happening. The event may include a noisy signal or may include a cardiac event. To differentiate, the method1100may analyze the incoming QRS complexes to determine if they are consistent. If the incoming QRS complexes are consistent, the method1100may develop a temporary QRS template and compare subsequent QRS complexes to the temporary QRS template. If the subsequent complexes match the temporary template, the method1100may record and flag the episode for a NSVT episode.

In some embodiments, the method1100may flag an NSVT episode by reviewing R-R stability. Noise generally causes false QRS detections, which creates heartrate variability, or R-R variability. R is a point corresponding to the peak of the QRS complex of the ECG wave, and R-R is an interval between success R points. R-R intervals are considered stable if the difference between two consecutive R-R-intervals is less than 20 milliseconds. Therefore, the R-R stability criterion is satisfied when a difference between at least two consecutive R-R intervals is less than 20 milliseconds.

Thus, the method1100may provide for storing potential episodes of NSVT. It should be noted that the method1100is just one implementation and that the operations of the method1000may be rearranged or otherwise modified such that other implementations are possible.

FIG.12is a flow chart illustrating an example of a method1200for WCD systems, in accordance with various aspects of the present disclosure. For clarity, the method1200is described below with reference to aspects of one or more of the systems described herein.

At block1102, the method1200may analyze at least one ECG signal. At block1202, the method1200may generate a temporary QRS template using the first few QRS complexes of a suspected episode. Once a temporary QRS template is generated, at block1204, the method1200may compare incoming QRS complexes to the temporary QRS template. If the QRS morphology varies greatly between incoming QRS complexes and the normalized QRS template, the method1200may determine the signal contains noise and not track an NSVT episode. In some embodiments, the method1200may analyze the at least one ECG signal to determine if the incoming QRS complexes correlate to the NSR template as mentioned previously.

However, if the incoming QRS complexes substantially match the temporary QRS template, resulting in a low morphology, the method1200may determine the signal is good and at block1104, diagnose or flag an episode of NSVT. Then at block1206, the method1200may store the episode of potential NSVT based at least in part on the diagnosing. This may enable doctors and clinicians to later review the episode information and determine the patient may be at risk to develop sustained VT.

Thus, the method1200may provide for storing potential episodes of NSVT. It should be noted that the method1200is just one implementation and that the operations of the method1200may be rearranged or otherwise modified such that other implementations are possible.

A person skilled in the art will be able to practice the present invention after careful review of this description, which is to be taken as a whole. Details have been included to provide a thorough understanding. In other instances, well-known aspects have not been described, in order to not obscure unnecessarily this description.

Some technologies or techniques described in this document may be known. Even then, however, it is not known to apply such technologies or techniques as described in this document, or for the purposes described in this document.

This description includes one or more examples, but this fact does not limit how the invention may be practiced. Indeed, examples, instances, versions or embodiments of the invention may be practiced according to what is described, or yet differently, and also in conjunction with other present or future technologies. Other such embodiments include combinations and sub-combinations of features described herein, including for example, embodiments that are equivalent to the following: providing or applying a feature in a different order than in a described embodiment; extracting an individual feature from one embodiment and inserting such feature into another embodiment; removing one or more features from an embodiment; or both removing a feature from an embodiment and adding a feature extracted from another embodiment, while providing the features incorporated in such combinations and sub-combinations.

In general, the present disclosure reflects preferred embodiments of the invention. The attentive reader will note, however, that some aspects of the disclosed embodiments extend beyond the scope of the claims. To the respect that the disclosed embodiments indeed extend beyond the scope of the claims, the disclosed embodiments are to be considered supplementary background information and do not constitute definitions of the claimed invention.

In this document, the phrases “constructed to”, “adapted to” and/or “configured to” denote one or more actual states of construction, adaptation and/or configuration that is fundamentally tied to physical characteristics of the element or feature preceding these phrases and, as such, reach well beyond merely describing an intended use. Any such elements or features can be implemented in a number of ways, as will be apparent to a person skilled in the art after reviewing the present disclosure, beyond any examples shown in this document.

Incorporation by reference: References and citations to other documents, such as patents, patent applications, patent publications, journals, books, papers, web contents, have been made throughout this disclosure. All such documents are hereby incorporated herein by reference in their entirety for all purposes.

Parent patent applications: Any and all parent, grandparent, great-grandparent, etc. patent applications, whether mentioned in this document or in an Application Data Sheet (“ADS”) of this patent application, are hereby incorporated by reference herein as originally disclosed, including any priority claims made in those applications and any material incorporated by reference, to the extent such subject matter is not inconsistent herewith.

Reference numerals: In this description a single reference numeral may be used consistently to denote a single item, aspect, component, or process. Moreover, a further effort may have been made in the preparation of this description to use similar though not identical reference numerals to denote other versions or embodiments of an item, aspect, component or process that are identical or at least similar or related. Where made, such a further effort was not required, but was nevertheless made gratuitously so as to accelerate comprehension by the reader. Even where made in this document, such a further effort might not have been made completely consistently for all of the versions or embodiments that are made possible by this description. Accordingly, the description controls in defining an item, aspect, component or process, rather than its reference numeral. Any similarity in reference numerals may be used to infer a similarity in the text, but not to confuse aspects where the text or other context indicates otherwise.

The claims of this document define certain combinations and subcombinations of elements, features and acts or operations, which are regarded as novel and non-obvious. The claims also include elements, features and acts or operations that are equivalent to what is explicitly mentioned. Additional claims for other such combinations and subcombinations may be presented in this or a related document. These claims are intended to encompass within their scope all changes and modifications that are within the true spirit and scope of the subject matter described herein. The terms used herein, including in the claims, are generally intended as “open” terms. For example, the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” etc. If a specific number is ascribed to a claim recitation, this number is a minimum but not a maximum unless stated otherwise. For example, where a claim recites “a” component or “an” item, it means that the claim can have one or more of this component or this item.

In construing the claims of this document, the inventor(s) invoke 35 U.S.C. § 112(f) only when the words “means for” or “steps for” are expressly used in the claims. Accordingly, if these words are not used in a claim, then that claim is not intended to be construed by the inventor(s) in accordance with 35 U.S.C. § 112(f).