Wearable cardioverter defibrillator (WCD) system reacting to high-frequency ECG noise
In embodiments a wearable cardioverter defibrillator (WCD) system is worn by an ambulatory patient. The WCD system analyzes an ECG signal of the patient, to determine whether or not the patient should be given an electric shock to restart their heart. If the WCD system determines that such a shock should be given, then it also determines whether or not a High Frequency (H-F) noise criterion is met by the ECG signal. If that H-F noise criterion is not met, the patient can be shocked. If, however, that H-F noise criterion is met, then the WCD system can confirm before shocking, by sensing another portion of the ECG signal, analyzing again, and so on. Thanks to the confirmation before shocking, the possibility is diminished that the ECG signal will indicate that a shock is needed falsely, due to H-F noise. This can further reduce false patient alarms, and so on.
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 an Electrocardiogram (ECG) signal of the patient; an
a processor configured to:
determine from a first portion of the sensed ECG signal, whether a first shock criterion is met,
determine whether the first portion of the sensed ECG signal meets a High-Frequency (H-F) noise criterion, wherein H-F noise is present in the sensed EGC signal when a peak in the sensed ECG signal has a duration 25 milliseconds or less,
responsive to the first shock criterion being met and the H-F noise criterion not being met, control 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, else
responsive to the first shock criterion being met and the H-F noise criterion being met, determine from a second portion of the sensed ECG signal, whether a second shock criterion is met, the second portion sensed subsequently to the first portion and, responsive to the second shock criterion being met, control the discharge circuit to discharge the stored electrical charge through the patient while the support structure is worn by the patient to deliver a shock to the patient;
wherein the processor is further configured to:
identify a potential R peak of a QRS complex in the first portion of the sensed ECG signal,
define an ECG segment as a segment of the first ECG signal portion that corresponds to the potential R peak, and
determine whether the H-F noise criterion is met responsive to the ECG segment meeting a segment noise criterion, the segment noise criterion being met responsive to the ECG segment containing at least one peak briefer than a threshold duration of 25 ms.
2. The WCD system of claim 1 , in which
the second shock criterion is the same as the first shock criterion.
3. The WCD system of claim 1 , in which
the ECG segment includes the potential R peak that it corresponds to.
4. The WCD system of claim 1 , in which
the ECG segment starts at the potential R peak that it corresponds to.
5. The WCD system of claim 1 , in which
the ECG segment has a duration between 160 ms and 200 ms.
6. The WCD system of claim 1 , further comprising:
a filter to filter the ECG segment, and
wherein the processor is further configured to:
determine whether the H-F noise criterion is met responsive to the filtered ECG segment meeting the segment noise criterion.
7. The WCD system of claim 6 , in which the filter is configured to pass frequencies between 8 Hz and 25 Hz.
8. The WCD system of claim 6 , in which
the ECG segment has a duration between 160 ms and 200 ms.
9. The WCD system of claim 6 , in which
the ECG segment starts at the potential R peak that it corresponds to.
10. The WCD system of claim 1 , in which
the segment noise criterion is met responsive to the ECG segment containing more zero-crossings than a crossings threshold.
11. The WCD system of claim 10 , in which
the crossings threshold is five.
12. The WCD system of claim 10 , in which
the ECG segment has a duration between 160 ms and 200 ms.
13. The WCD system of claim 1 , in which
the ECG segment has a duration between 160 ms and 200 ms.