Wearable cardioverter defibrillator (WCD) system computing patient heart rate by multiplying ECG signals from different channels

• US 10,589,109 B2
• Filed: 03/20/2018
• Issued: 03/17/2020
• Est. Priority Date: 04/10/2017
• Status: Active Grant

• Current Assignee: West Affum Holdings DAC
• Original Assignee: West Affum Holdings Corp
• Inventors: Kim, Jaeho
• Primary Examiner(s): Getzow, Scott M.
• Application Number:
  US15/927,017
• Publication Number:
  US 20180289974A1
• Time in Patent Office: 728 Days
• CPC Class Codes: A61B 5/341 Vectorcardiography [VCG]
• CPC Class Codes: A61B 5/352 Detecting R peaks, e.g. for synchronising diagnostic apparatus; Estimating R-R interval
• CPC Class Codes: A61B 5/363 Detecting tachycardia or bradycardia
• CPC Class Codes: A61B 5/7217 of noise originating from a therapeutic or surgical apparatus, e.g. from a pacemaker
• CPC Class Codes: A61B 5/7235 Details of waveform analysis A61B5/349 takes precedence
• CPC Class Codes: A61N 1/046 Specially adapted for shock therapy, e.g. defibrillation
• CPC Class Codes: A61N 1/0484 Garment electrodes worn by the patient
• CPC Class Codes: A61N 1/3904 External heart defibrillators [EHD]
• CPC Class Codes: A61N 1/3925 Monitoring; Protecting
• CPC Class Codes: A61N 1/3968 Constructional arrangements, e.g. casings A61N1/375 takes precedence
• CPC Class Codes: A61N 1/3987 characterised by the timing or triggering of the shock

Abstract

A wearable cardioverter defibrillator system includes a support structure that is configured to be worn by a patient. When thus worn, the support structure may attach electrodes at different locations of the patient'"'"'s body, so as to define different vectors. A measurement circuit may sense ECG signals from the different vectors substantially concurrently. A processor may multiply together these substantially concurrent ECG signals to derive a product waveform. The processor may then detect peaks in the product waveform, measure durations of time intervals between successive peaks, and determine the patient'"'"'s heart rate from these durations. An advantage can be that the heart rate may be computed notwithstanding noise in the individual ECG signals.

Claims

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 be attached at different locations of the patient'"'"'s body so as to define at least a first vector and a second vector distinct from the first vector;

a measurement circuit configured to sense a first Electrocardiogram (ECG) signal from the first vector, a second ECG signal from the second vector substantially contemporaneously with sensing the first ECG signal, and a subsequent ECG signal after sensing the first ECG signal; and

a processor configured to;

multiply values of the first ECG signal with values of the second ECG signal to derive a product waveform,

detect, in the product waveform, peaks that exceed a detection threshold,

measure durations of time intervals between pairs of successive ones of the detected peaks,

compute a heart rate of the patient from the measured durations of the time intervals,

determine from the subsequent ECG signal 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; and

a communication module configured to transmit wirelessly the computed heart rate.

2. The WCD system of claim 1, further comprising:

a screen configured to display the computed heart rate.

3. The WCD system of claim 1, in which

the first ECG signal is high-pass filtered to derive a high-pass filtered first ECG signal, and

the product waveform is derived by multiplying values of the high-pass filtered first ECG signal instead of multiplying values of the first ECG signal.

4. The WCD system of claim 1, in which

the electrodes further define a third vector,

the measurement circuit is further configured to sense a third ECG signal from the third vector, and

the processor is further configured to:

multiply values of the third ECG signal with the values of the first ECG signal and of the second ECG signal to derive the product waveform.

5. The WCD system of claim 4, in which

the electrodes further define a fourth vector,

the measurement circuit is further configured to sense a fourth ECG signal from the fourth vector, and

the processor is further configured to:

multiply values of the fourth ECG signal with the values of the first ECG signal, of the second ECG signal and of the third ECG signal, to derive the product waveform.

6. The WCD system of claim 1, in which

when a peak is detected at a certain moment, no other peaks are detected for an inactive time period after the certain moment.

7. The WCD system of claim 1, in which

the detection threshold changes with time.

8. The WCD system of claim 1, in which

responsive to a certain one of the peaks being thus detected, a certain amplitude of the certain detected peak is input, and

the detection threshold is then established responsive to the input certain amplitude.

9. The WCD system of claim 1, in which

the second ECG signal is time-shifted with respect to the first ECG signal to derive a time-shifted second ECG signal, and

the product waveform is derived by multiplying values of the time-shifted second ECG signal instead of multiplying values of the sensed second ECG signal.

10. The WCD system of claim 9, in which

the processor is further configured to:

detect a first test peak occurring in the first ECG signal,

detect a second test peak occurring in the second ECG signal,

detect a time lag between the first test peak and the second test peak, and

in which the second ECG signal is time-shifted according to the time lag.

11. 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 be attached at different locations of the patient'"'"'s body so as to define at least a first vector and a second vector distinct from the first vector;

a measurement circuit configured to sense a first Electrocardiogram (ECG) signal from the first vector, a second ECG signal from the second vector substantially contemporaneously with sensing the first ECG signal, and a subsequent ECG signal after sensing the first ECG signal;

a processor configured to;

multiply values of the first ECG signal with values of the second ECG signal to derive a product waveform,

detect, in the product waveform, peaks that exceed a detection threshold,

measure durations of time intervals between pairs of successive ones of the detected peaks,

compute a heart rate of the patient from the measured durations of the time intervals,

determine from the subsequent ECG signal 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; and

a screen configured to display the computed heart rate.

12. The WCD system of claim 11, in which

the first ECG signal is high-pass filtered to derive a high-pass filtered first ECG signal, and

the product waveform is derived by multiplying values of the high-pass filtered first ECG signal instead of multiplying values of the first ECG signal.

13. The WCD system of claim 11, in which

the electrodes further define a third vector,

the measurement circuit is further configured to sense a third ECG signal from the third vector, and

the processor is further configured to:

multiply values of the third ECG signal with the values of the first ECG signal and of the second ECG signal to derive the product waveform.

14. The WCD system of claim 13, in which

the electrodes further define a fourth vector,

the measurement circuit is further configured to sense a fourth ECG signal from the fourth vector, and

the processor is further configured to:

multiply values of the fourth ECG signal with the values of the first ECG signal, of the second ECG signal and of the third ECG signal, to derive the product waveform.

15. The WCD system of claim 11, in which

when a peak is detected at a certain moment, no other peaks are detected for an inactive time period after the certain moment.

16. The WCD system of claim 11, in which

the detection threshold changes with time.

17. The WCD system of claim 11, in which

responsive to a certain one of the peaks being thus detected, a certain amplitude of the certain detected peak is input, and

the detection threshold is then established responsive to the input certain amplitude.

18. The WCD system of claim 11, in which

the second ECG signal is time-shifted with respect to the first ECG signal to derive a time-shifted second ECG signal, and

the product waveform is derived by multiplying values of the time-shifted second ECG signal instead of multiplying values of the sensed second ECG signal.

19. The WCD system of claim 18, in which

the processor is further configured to:

detect a first test peak occurring in the first ECG signal,

detect a second test peak occurring in the second ECG signal,

detect a time lag between the first test peak and the second test peak, and

in which the second ECG signal is time-shifted according to the time lag.

20. 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 further including a support structure configured to be worn by an ambulatory patient, an energy storage module that can store an electrical charge, a discharge circuit coupled to the energy storage module, electrodes attached at different locations of the patient'"'"'s body so as to define at least a first vector and a second vector distinct from the first vector, and a measurement circuit, these one or more programs result in operations comprising;

sensing, by the electrodes, a first Electrocardiogram (ECG) signal from the first vector;

sensing a second ECG signal from the second vector substantially contemporaneously with sensing the first ECG signal;

multiplying values of the first ECG signal with values of the second ECG signal to derive a product waveform;

detecting, in the product waveform, peaks that exceed a detection threshold;

measuring durations of time intervals between pairs of successive ones of the detected peaks;

computing a heart rate of the patient from the measured durations of the time intervals;

sensing a subsequent ECG signal after sensing the first ECG signal;

determining from the subsequent ECG signal 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.

21. 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, electrodes attached at different locations of the patient'"'"'s body so as to define at least a first vector and a second vector distinct from the first vector, a measurement circuit and a processor, the method comprising:

sensing, by the electrodes, a first Electrocardiogram (ECG) signal from the first vector;

sensing a second ECG signal from the second vector substantially contemporaneously with sensing the first ECG signal;

multiplying values of the first ECG signal with values of the second ECG signal to derive a product waveform;

detecting, in the product waveform, peaks that exceed a detection threshold;

measuring durations of time intervals between pairs of successive ones of the detected peaks;

computing a heart rate of the patient from the measured durations of the time intervals;

sensing a subsequent ECG signal after sensing the first ECG signal;

determining from the subsequent ECG signal 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.