Wearable cardioverter defibrillator (WCD) system computing heart rate from noisy ECG signal
In embodiments, a WCD system includes electrodes with which it senses an ECG signal of the patient. A processor may detect sequential peaks within the ECG signal, measure durations of time intervals between the peaks, including between non-sequential peaks, and identify a representative duration that best meets a plausibility criterion. The plausibility criterion may be that the representative duration is the one that occurs the most often, i.e. is the mode. Then a heart rate can be computed from a duration indicated by the representative duration and, if the heart rate meets a shock condition, the WCD system may deliver a shock to the patient. An advantage can be that the representative duration can be close to a good R-R interval measurement of a patient, notwithstanding noise in the ECG signal that is in the shape of peaks.
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 sense a first Electrocardiogram (ECG) signal of the patient, and a second ECG signal after sensing the first ECG signal; and
a processor configured to:
detect peaks occurring sequentially within the first ECG signal,
establish pairs of the detected peaks, at least one of the pairs being established by peaks not occurring sequentially,
measure durations of time intervals defined by the established pairs,
identify, from the measured durations, a representative duration that best meets a plausibility criterion,
compute a heart rate of the patient from a duration indicated by the representative duration,
determine from the second 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 memory configured to store the computed heart rate.
2. The WCD system of claim 1 , further comprising:
a communication module configured to transmit wirelessly the stored heart rate.
3. The WCD system of claim 1 , further comprising:
a screen configured to display the stored heart rate.
4. The WCD system of claim 1 , in which
all possible pairs of the detected peaks are established.
5. The WCD system of claim 1 , in which
the electrodes are further configured to sense another ECG signal of the patient distinct from the ECG signal and from the second ECG signal, and
the processor is further configured to:
detect other peaks occurring sequentially within the other ECG signal,
establish other pairs of the detected other peaks, at least one of the other pairs being established by other peaks not occurring sequentially within the other ECG signal,
measure other durations of time intervals defined by the established other pairs, and
the representative duration is identified from both the measured durations and the measured other durations.
6. The WCD system of claim 1 , in which
the plausibility criterion includes that the representative duration is the one that occurs the most often among the measured durations.
7. The WCD system of claim 1 , in which
the plausibility criterion includes that a fraction of the identified representative duration occurs less often than an occurrence threshold.
8. The WCD system of claim 1 , in which
the plausibility criterion includes that, while the representative duration has a value of D and occurs M times, and
a duration having a value of D/N, where N takes one of the values of 2, 3, 4 and 5, occurs less often than M/N times.
9. The WCD system of claim 1 , in which
the heart rate is computed from the representative duration.
10. The WCD system of claim 1 , in which
the processor is further configured to:
discern clusters of the measured durations, and
the representative duration is identified from the cluster that best meets the plausibility criterion.
11. The WCD system of claim 10 , in which
the clusters are identified by filtering the measured durations.
12. The WCD system of claim 10 , in which
the plausibility criterion includes that the representative duration is the one that occurs the most often among the measured durations.
13. The WCD system of claim 10 , in which
the plausibility criterion includes that a fraction of the identified representative duration occurs less often than an occurrence threshold.
14. The WCD system of claim 10 , in which
the plausibility criterion includes that, while the representative duration has a value of D and occurs M times, and
a duration having a value of D/N, where N takes one of the values of 2, 3, 4 and 5, occurs less often than M/N times.