# US 11,077,310 B1 · Wearable cardioverter defibrillator (WCD) system detecting QRS complexes in ECG signal by matched difference filter

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- Number: US 11,077,310 B1
- Document ID: US11077310B1
- Status: Granted
- Kind: B1
- Application number: 15/724,317
- Filed: 2017-10-04
- Granted: 2021-08-03
- Earliest claimed: 2016-10-04
- Assignees: West Affum Holdings Corp.
- Applicants: West Affum Holdings Corp.
- Inventors: Joseph L. Sullivan
- Web page: https://patentgrep.com/patent/US11077310B1

## CPC

- A61B 5/361: Detecting fibrillation
- A61N 1/3987: {characterised by the timing or triggering of the shock}
- A61B 5/363: Detecting tachycardia or bradycardia
- A61B 5/366: Detecting abnormal QRS complex, e.g. widening
- A61B 5/7275: {Determining trends in physiological measurement data; Predicting development of a medical condition based on physiological measurements, e.g. determining a risk factor}
- A61N 1/3904: {External heart defibrillators [EHD]}
- A61N 1/3925: {Monitoring; Protecting}
- A61N 1/046: {Specially adapted for shock therapy, e.g. defibrillation}
- A61B: DIAGNOSIS; SURGERY; IDENTIFICATION (usefulness limited to only animals A61D)
- A61N: ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY (measurement of bioelectric currents A61B; surgical instruments, devices or methods for transferring non-mechanical forms of energy to or from the body A61B18/00; anaesthetic apparatus in general A61M; incandescent lamps H01K; infrared radiators for heating H05B)

## Abstract

In embodiments, a wearable cardioverter defibrillator (WCD) system includes electrodes that render an ECG signal of the patient, and a processor that receives ECG data are derived from the rendered ECG signal. The processor may filter the received ECG data with a matched difference filter to detect QRS complexes, and compute a heart rate from the detected QRS complexes. The matched difference filter itself can have coefficient values associated with a baseline QRS complex, which improves detection.

## Claims

### Claim 1

A wearable cardioverter defibrillator (WCD) system, comprising:
a support structure configured to be worn by an ambulatory patient;
an energy storage module configured to store an electrical charge;
a discharge circuit coupled to the energy storage module;
electrodes configured to render an electrocardiogram (ECG) signal of the patient while the patient is wearing the support structure; and
a processor configured to:
receive ECG data that are derived from the rendered ECG signal, the ECG data having values f(m),
compute, from the values f(m), outputs for multiple values of a positive integer n according to an equation comprising a matched difference term (MDT) where, in the equation, MDT is a matched difference term that is a function of a difference of a first function F[] of the values f(m) and of a second function G[] of coefficient values g(m) that are associated with a baseline QRS complex,
detect QRS complexes from the computed outputs,
compute a heart rate from the detected QRS complexes,
determine, from the computed heart rate, whether or not a shock criterion is met, and
control, responsive to the shock criterion being met, the discharge circuit to discharge the stored electrical charge through the patient while the support structure is worn by the patient so as to deliver a shock to the patient.

### Claim 2 (depends on 1)

The WCD system of claim 1, in which
the received ECG data is derived from the rendered ECG signal without taking a time derivative of the rendered ECG signal.

### Claim 3 (depends on 1)

The WCD system of claim 1, in which
the processor is further configured to take a time derivative of the received ECG data before computing the outputs, and
the coefficient values represent a time derivative of the baseline QRS complex.

### Claim 4 (depends on 1)

The WCD system of claim 1, in which
the received ECG data is derived from the rendered ECG signal after the ECG signal of the patient passes through a capacitor in series, and
the coefficient values represent a time derivative of the baseline QRS complex.

### Claim 5 (depends on 1)

The WCD system of claim 1, in which
the MDT term comprises a fraction.

### Claim 6 (depends on 1)

The WCD system of claim 1, further comprising:
a memory, and in which
the electrodes are further configured to render previously a previous ECG signal of the patient while the patient was previously wearing the support structure,
the processor is further configured to receive previous ECG data that are derived from the previous ECG signal, and
the coefficient values of g(m) in the equation are derived from the previous ECG data.

### Claim 7

A non-transitory computer-readable storage medium storing one or more programs which, when executed by at least one processor of a wearable cardioverter defibrillator (WCD) system, the WCD system including a support structure configured to be worn by an ambulatory patient, an energy storage module storing an electrical charge, a discharge circuit coupled to the energy storage module and electrodes configured to render an electrocardiogram (ECG) signal of the patient while the patient is wearing the support structure, these one or more programs result in operations comprising:
receiving ECG data that are derived from the rendered ECG signal, the ECG data having values f(m);
computing, from the values f(m), outputs for multiple values of a positive integer n according to an equation comprising a matched difference term (MDT) where, in the equation, MDT is a matched difference term that is a function of a difference of a first function F[] of the values f(m) and of a second function G[] of coefficient values g(m) that are associated with a baseline QRS complex;
detecting QRS complexes from the computed outputs;
computing a heart rate from the detected QRS complexes;
determining, from the computed heart rate, whether or not a shock criterion is met; and
controlling, responsive to the shock criterion being met, the discharge circuit to discharge the stored electrical charge through the patient while the support structure is worn by the patient so as to deliver a shock to the patient.

### Claim 8 (depends on 7)

The medium of claim 7, in which
the received ECG data is derived from the rendered ECG signal without taking a time derivative of the rendered ECG signal.

### Claim 9 (depends on 7)

The medium of claim 7, in which when the one or more programs are executed by the at least one processor, the program operations further comprise:
taking a time derivative of the received ECG data before computing the outputs.

### Claim 10 (depends on 7)

The medium of claim 7, in which
the received ECG data is derived from the rendered ECG signal after the ECG signal of the patient passes through a capacitor in series.

### Claim 11 (depends on 7)

The medium of claim 7, in which
the MDT term comprises a fraction.

### Claim 12 (depends on 7)

The medium of claim 7, in which
the WCD system further includes a memory, in which when the one or more programs are executed by the at least one processor, the operations further comprise:
further rendering previously a previous ECG signal of the patient while the patient was previously wearing the support structure;
receiving previous ECG data that are derived from the previous ECG signal, and in which the coefficient values of g(m) in the equation are derived from the previous ECG data.

### Claim 13

A method for a wearable cardioverter defibrillator (WCD) system, the WCD system including a support structure configured to be worn by an ambulatory patient, an energy storage module storing an electrical charge, a discharge circuit coupled to the energy storage module and electrodes, the method comprising:
rendering an electrocardiogram (ECG) signal of the patient while the patient is wearing the support structure;
receiving ECG data that are derived from the rendered ECG signal, the ECG data having values f(m);
computing, from the values f(m), outputs for multiple values of a positive integer n according to an equation comprising a matched difference term (MDT) where, in the equation, MDT is a matched difference term that is a function of a difference of a first function F[] of the values f(m) and of a second function G[] of coefficient values g(m) that are associated with a baseline QRS complex;
detecting QRS complexes from the computed outputs;
computing a heart rate from the detected QRS complexes;
determining, from the computed heart rate, whether or not a shock criterion is met; and controlling, responsive to the shock criterion being met, the discharge circuit to discharge the stored electrical charge through the patient while the support structure is worn by the patient so as to deliver a shock to the patient.

### Claim 14 (depends on 13)

The method of claim 13, in which
the received ECG data is derived from the rendered ECG signal without taking a time derivative of the rendered ECG signal.

### Claim 15 (depends on 13)

The method of claim 13, further comprising:
taking a time derivative of the received ECG data before computing the outputs.

### Claim 16 (depends on 13)

The method of claim 13, in which
the received ECG data is derived from the rendered ECG signal after the ECG signal of the patient passes through a capacitor in series.

### Claim 17 (depends on 13)

The method of claim 13, in which
the MDT term comprises a fraction.

### Claim 18 (depends on 13)

The method of claim 13, in which
the WCD system further includes a memory, and further comprising:
further rendering previously a previous ECG signal of the patient while the patient was previously wearing the support structure;
receiving previous ECG data that are derived from the previous ECG signal, and in which the coefficient values of g(m) in the equation are derived from the previous ECG data.

### Claim 19

A wearable cardioverter defibrillator (WCD) system, comprising:
a support structure configured to be worn by a patient;
an energy storage module configured to store an electrical charge;
a discharge circuit coupled to the energy storage module;
electrodes configured to output an electrocardiogram (ECG) signal of the patient while the patient is wearing the support structure;
a heart rate detector to detect a heart rate of the patient; and
a processor configured to:
receive ECG data that are derived from the ECG signal, the ECG data having values f(m),
compute, from the values f(m), outputs for multiple values of a positive integer n according to an equation comprising a matched difference term (MDT) where, in the equation, MDT is a matched difference term that is a function of a difference of a first function F[] of the values f(m) and of a second function G[] of coefficient values g(m) that are associated with a baseline QRS complex,
detect QRS complexes from the computed outputs,
compute a heart rate from the detected QRS complexes,
determine, from the detected heart rate, whether or not a shock criterion is met,
control, responsive to the shock criterion being met, the discharge circuit to discharge at least a portion of the stored electrical charge through the patient while the support structure is worn by the patient so as to deliver a shock to the patient;
assess agreement between the detected heart rate and the computed heart rate, and
update the MDT for subsequent computing of the outputs when agreement is high.

### Claim 20 (depends on 19)

The WCD system of claim 19, in which
the received ECG data is derived from the ECG signal without taking a time derivative of the ECG signal.

### Claim 21 (depends on 19)

The WCD system of claim 19, in which
the processor is further configured to take a time derivative of the received ECG data before computing the outputs, and
the coefficient values represent a time derivative of the baseline QRS complex.

### Claim 22 (depends on 19)

The WCD system of claim 19, in which
the received ECG data is derived from the ECG signal after the ECG signal of the patient passes through a capacitor in series, and
the coefficient values represent a time derivative of the baseline QRS complex.

### Claim 23 (depends on 19)

The WCD system of claim 19, in which
the MDT term comprises a fraction.

### Claim 24 (depends on 19)

The WCD system of claim 19, further comprising:
a memory, and in which
the processor is further configured to receive previous ECG data that are derived from the previous ECG signal while the patient was previously wearing the support structure, and
the coefficient values of g(m) in the equation are derived from the previous ECG data.

### Claim 25

A method for a wearable cardioverter defibrillator (WCD) system, the WCD system including a support structure configured to be worn by a patient, an energy storage module storing an electrical charge, a discharge circuit coupled to the energy storage module and electrodes, and a heart rate detector to detect a heart rate of the patient, the method comprising:
detecting a heart rate of the patient with the heart rate detector;
outputting an electrocardiogram (ECG) signal of the patient while the patient is wearing the support structure;
receiving ECG data that are derived from the ECG signal, the ECG data having values f(m);
computing, from the values f(m), outputs for multiple values of a positive integer n according to an equation comprising a matched difference term (MDT) where, in the equation, MDT is a matched difference term that is a function of a difference of a first function F[] of the values f(m) and of a second function G[] of coefficient values g(m) that are associated with a baseline QRS complex;
detecting QRS complexes from the computed outputs;
computing a heart rate from the detected QRS complexes;
determining, from the detected heart rate, whether or not a shock criterion is met;
controlling, responsive to the shock criterion being met, the discharge circuit to discharge at least a portion of the stored electrical charge through the patient while the support structure is worn by the patient so as to deliver a shock to the patient;
assessing agreement between the detected heart rate and the computed heart rate; and
updating the MDT for subsequent computing of the outputs when agreement is high.

### Claim 26 (depends on 25)

The method of claim 25, in which
the received ECG data is derived from the ECG signal without taking a time derivative of the ECG signal.

### Claim 27 (depends on 25)

The method of claim 25, further comprising:
taking a time derivative of the received ECG data before computing the outputs.

### Claim 28 (depends on 25)

The method of claim 25, in which
the received ECG data is derived from the ECG signal after the ECG signal of the patient passes through a capacitor in series.

### Claim 29 (depends on 25)

The method of claim 25, in which
the MDT term comprises a fraction.

### Claim 30 (depends on 25)

The method of claim 25, in which
the WCD system further includes a memory, and further comprising:
further outputting previously a previous ECG signal of the patient while the patient was previously wearing the support structure;
receiving previous ECG data that are derived from the previous ECG signal, and in which the coefficient values of g(m) in the equation are derived from the previous ECG data.

### Claim 31

A wearable cardioverter defibrillator (WCD), comprising:
a support structure configured to be worn by a patient;
an energy storage module configured to store an electrical charge;
a discharge circuit coupled to the energy storage module;
electrodes configured to obtain an electrocardiogram (ECG) signal of the patient while the patient is wearing the support structure; and
a processor configured to:
process the ECG signal to detect a QRS complex in the ECG signal using an adaptive matched filter;
compute a heart rate of the patient based at least at least in part on the detected QRS complex;
determine based at least in part on the computed heat rate whether a shock criterion is met; and
responsive to the shock criterion being met, control the discharge circuit to discharge at least a portion of the stored electrical charge through the patient while the support structure is worn by the patent to deliver a shock to the patient;
wherein the processor is configured to:
assess a quality of the ECG signal; and
update a kernel of the adaptive matched filter when the quality of the ECG signal is high.

### Claim 32 (depends on 31)

The WCD of claim 31, further comprising a heart rate monitor to obtain the heart rate of the patient, wherein the processor is further configured to assess agreement between the computed heart rate and the heart rate obtained with the heart rate monitor, and wherein the processor is configured to assess the quality of the ECG as high when agreement between the computed heart rate and the heart rate obtained with the heart rate monitor is high.

### Claim 33 (depends on 31)

The WCD of claim 31, wherein the ECG signal is processed by the processor without taking a time derivative of the ECG signal.

### Claim 34 (depends on 31)

The WCD of claim 31, wherein the processor is further configured to take a time derivative of the received ECG signal to process the ECG signal.

### Claim 35 (depends on 31)

The WCD of claim 31, wherein the ECG signal passes through a series connected capacitor prior to being processed by the processor.

### Claim 36 (depends on 31)

The WCD of claim 31, wherein the processor is configured to continuously process the ECG signal using the adaptive matched filter.

### Claim 37 (depends on 31)

The WCD of claim 31, wherein the processor is configured to process segments of the ECG signal using the adaptive matched filter.

### Claim 38 (depends on 31)

The WCD of claim 31, wherein the processor is configured to assess the quality of the ECG signal as high when QRS complexes in a single segment are highly organized.