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

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.

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.

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.