Substantially-median-based determination of long-term heart rates from ECG data of wearable cardioverter defibrillator (WCD) system
A wearable medical monitoring (WMM) system may be worn for a long time. Some embodiments of WMM systems are wearable cardioverter defibrillator (WCD) systems. In such systems, ECG electrodes sense an ECG signal of the patient, and store it over the long-term. The stored ECG signal can be analyzed for helping long-term heart rate monitoring of the patient. The heart rate monitoring can be assisted a) by special filtering techniques that remove short-term variations inherent in patients' short-term heart rate determinations, and b) by indication techniques that indicate when conditions hampered sensing of the ECG signal too much for a reliable heart rate determination.
1. A method for helping monitor a patient, the patient having worn a wearable cardioverter defibrillator (WCD) system for at least one hour during which the WCD system included a defibrillation electrode, a support structure worn by the patient so as to maintain the defibrillation electrode on a body of the patient, an energy storage module storing an electrical charge configured to be discharged via the defibrillation electrode through the patient so as to deliver a shock to the patient, an Electrocardiogram (ECG) electrode sensing an ECG signal of the patient, a WCD processor analyzing short segments of the sensed ECG signal, and a memory storing WCD system data about the sensed ECG signal, the stored WCD system data being generated from at least one hour of the sensed ECG signal, the method comprising:
receiving the stored WCD system data;
inputting computed raw heart rate (HR) values for respective ones of the short ECG signal segments;
aggregating groups of the raw HR values into respective first time bins that are arranged in a time sequence;
deriving first HR values for respective ones of the first time bins, the first HR value of a certain one of the first time bins being derived from the raw HR values aggregated into the certain first time bin;
replacing a certain one of the first HR values of a certain one of the first time bins by an adjusted first HR value that is derived from the first HR value of the first time bin that is within a filter range of the certain first time bin in the time sequence, but is not derived from the certain first HR value; and
then storing at least some of the first HR values and the adjusted first HR value, the stored first HR values and adjusted first HR value having been thus derived from the stored WCD system data that is generated from at least one hour of the sensed ECG signal.
2. The method of claim 1 , in which
the short segments of the sensed ECG signal have a duration of approximately 4.8 sec.
3. The method of claim 1 , in which
the stored WCD system data encodes amplitude values of the sensed ECG signal, and
further comprising:
computing, from the amplitude values, the raw HR values that are subsequently inputted.
4. The method of claim 1 , in which
the WCD processor further computes the raw HR values, and
the stored WCD system data includes the raw HR values that are subsequently inputted.
5. The method of claim 4 , in which
the WCD system further includes a plurality of ECG electrodes,
three or more channels are defined by the plurality of ECG electrodes,
three or more versions of the patient's ECG signal are sensed from the three or more channels,
the WCD processor analyzes short segments of the three or more versions of the patient's ECG signal, and
a certain one of the inputted HR values is computed by:
computing three or more respective tentative HR values from the three or more short segments of the three or more versions of the patient's ECG signal, and
deriving the certain inputted HR value from a middlemost-ranked one of the three or more respective tentative HR values.
6. The method of claim 1 , in which the first HR value of the certain first time bin is derived from all of the raw HR values aggregated into the certain first time bin.
7. The method of claim 1 , in which
the adjusted first HR value is the first HR value of the first time bin that is within the filter range of the certain first time bin in the time sequence.
8. The method of claim 1 , further comprising:
discarding, from the certain first time bin, a certain computed raw HR value that meets an error condition, and in which
the first HR value of the certain first time bin derived from at least some of the raw HR values aggregated and remaining into the certain first time bin after the discarding.
9. The method of claim 8 , in which
the certain computed raw HR value meets the error condition when it differs from another raw HR value aggregated into the certain first time bin by at least an error HR threshold, but
no two other raw HR values aggregated into the certain first time bin differ from each other by as much as the error HR threshold.
10. A computer system for helping monitor a patient, the patient having worn a wearable cardioverter defibrillator (WCD) system for at least one hour during which the WCD system included a defibrillation electrode, a support structure worn by the patient so as to maintain the defibrillation electrode on a body of the patient, an energy storage module storing an electrical charge configured to be discharged via the defibrillation electrode through the patient so as to deliver a shock to the patient, an Electrocardiogram (ECG) electrode sensing an ECG signal of the patient, a WCD processor analyzing short segments of the sensed ECG signal, and a memory storing WCD system data about the sensed ECG signal, the stored WCD system data being generated from at least one hour of the sensed ECG signal, the computer system comprising:
a screen;
one or more computer processors distinct from the WCD processor; and
a non-transitory computer-readable storage medium storing one or more programs which, when executed by the one or more computer processors, result in operations comprising:
receiving the stored WCD system data;
inputting computed raw heart rate (HR) values for respective ones of the short ECG signal segments;
aggregating groups of the raw HR values into respective first time bins;
deriving first HR values for respective ones of the first time bins, from at least some of the raw HR values aggregated into each first time bin;
marking as error-prone a certain one of the first HR values for which an error condition is determined to be met;
storing the first HR values, the stored first HR values having been thus derived from the stored WCD system data that is generated from at least one hour of the sensed ECG signal; and
causing to be displayed on the screen in a first manner the stored first HR values but not the certain first HR value, and in a second manner different from the first manner the certain first HR value.
11. The computer system of claim 10 , in which
the short segments of the sensed ECG signal have a duration of approximately 4.8 sec.
12. The computer system of claim 10 , in which
the stored WCD system data encodes amplitude values of the sensed ECG signal, and
when the one or more programs are executed by the one or more computer processors, the resulting operations further comprise:
computing, from the amplitude values, the raw HR values that are subsequently inputted.
13. The computer system of claim 10 , in which
the WCD processor further computes the raw HR values, and
the stored WCD system data includes the raw HR values that are subsequently inputted.
14. The computer system of claim 10 , in which
the error condition includes that the certain first HR value is derived from a certain one of the first time bins, the certain first time bin aggregating a group of the raw HR values of which one is larger than another one by at least an error HR threshold.
15. The computer system of claim 14 , in which
the error HR threshold is about 10%.
16. The computer system of claim 10 , in which
the WCD system further includes a plurality of ECG electrodes,
three or more channels are defined by the plurality of ECG electrodes,
three or more versions of the patient's ECG signal are sensed from the three or more channels, and
the error condition includes that one of the ECG electrodes is detected to be off.
17. The computer system of claim 10 , in which
the WCD system further includes a plurality of ECG electrodes,
three or more channels are defined by the plurality of ECG electrodes,
three or more versions of the patient's ECG signal are sensed from the three or more channels, and
the error condition includes that, in at least one of the versions, a detected noise exceeds a noise threshold.
18. The computer system of claim 10 , in which
the second manner includes displaying error indicia in relation to the certain first HR value.
19. The computer system of claim 11 , in which
the second manner further includes not displaying the certain first HR value at all.
20. A method for helping monitor a patient, the patient having worn a wearable medical monitor (WMM) system for at least one hour during which the WMM system included a plurality of Electrocardiogram (ECG) electrodes, a support structure worn by the patient so as to maintain the ECG electrodes on a body of the patient, the ECG electrodes thus defining two or more channels and sensing two or more versions of an ECG signal of the patient across the two or more channels, a WMM processor analyzing short segments of the sensed ECG signal, and a memory storing WMM system data about the sensed ECG signal, the stored WMM system data being generated from at least one hour of the sensed ECG signal, the method comprising:
receiving the stored WMM system data;
inputting computed raw heart rate (HR) values for respective ones of the short ECG signal segments;
aggregating groups of the raw HR values into respective first time bins that are arranged in a time sequence;
discarding, from their respective first time bins, computed raw heart rate (HR) values that meet an error condition;
deriving first HR values for respective ones of the first time bins, the first HR value of a certain one of the first time bins being derived from raw HR values aggregated and remaining into the certain first time bin after the discarding;
then storing at least some of the first HR values, the stored first HR values having been thus derived from the stored WMM system data that is generated from at least one hour of the sensed ECG signal.