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 use in monitoring a patient, the method comprising:
receiving, from a wearable cardioverter defibrillator (WCD) system, WCD system data, wherein the WCD system includes an electrocardiogram (ECG) electrode and the WCD system data comprises data generated based, at least in part, on an ECG signal of the patient that was sensed by the ECG electrode for at least one hour;
computing raw heart rate (HR) values for respective ones of short ECG signal segments of the ECG signal;
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 WCD system data;
displaying in a first manner the stored first HR values but not the certain one of the first HR values, and displaying in a second manner different from the first manner the certain one of the first HR values.
2. The method of claim 1 , wherein
the short ECG signal segments have a duration of approximately 4.8 sec.
3. The method of claim 2 , wherein
the second manner further includes not displaying the certain one of the first HR values at all.
4. The method of claim 1 , wherein
the WCD system data encodes amplitude values of the ECG signal, and
the method further comprises:
computing, from the amplitude values, the raw HR values that are subsequently inputted.
5. The method of claim 1 , wherein
a processor of the WCD system is configured to compute the raw HR values.
6. The method of claim 1 , wherein
the error condition includes that the certain one of the first HR values is derived from a certain one of the first time bins, wherein the certain one of the first time bins aggregates a group of the raw HR values of which one is larger than another one by at least an error HR threshold.
7. The method of claim 6 , wherein
the error HR threshold is about 10%.
8. The method of claim 1 , wherein
the ECG electrode comprises the ECG electrode included with a plurality of ECG electrodes,
three or more channels being defined by the plurality of ECG electrodes, and
the error condition includes that one of the plurality of ECG electrodes is detected to be off.
9. The method of claim 1 , wherein
the ECG electrode comprises the ECG electrode included with a plurality of ECG electrodes,
three or more channels being defined by the plurality of ECG electrodes,
the error condition includes that, in at least one of the three or more channels, a detected noise exceeds a noise threshold.
10. The method of claim 1 , wherein
the second manner includes not displaying the certain one of the first HR values at all.
11. The method of claim 1 , wherein
the second manner includes displaying error indicia in relation to the certain one of the first HR values.
12. A wearable medical monitor (WMM) system, comprising:
a plurality of electrocardiogram (ECG) electrodes;
a support structure configured to be worn by a patient so as to maintain the ECG electrodes on a body of the patient, wherein the ECG electrodes define two or more channels;
a memory; and
one or more processors that are communicatively coupled to the plurality of ECG electrodes and the memory, wherein the one or more processors are configured to:
receive, from the plurality of ECG electrodes, an ECG signal, the received ECG signal is sensed by the plurality of ECG electrodes for at least one hour,
analyze short ECG segments of the ECG signal,
compute raw heart rate (HR) values for respective ones of the short ECG segments,
aggregate groups of the raw HR values into respective first time bins that are arranged in a time sequence,
discard, from their respective first time bins, computed raw heart rate (HR) values that meet an error condition,
derive 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 one of the first time bins after the computed raw heart rate (HR) values that meet the error condition are discarded, and
store in the memory at least some of the first HR values.
13. The WMM system of claim 12 , wherein
the short ECG segments have a duration of approximately 4.8 sec.
14. The WMM system of claim 12 , wherein
the error condition occurs when a particular raw HW value differs from another raw HR value aggregated into the certain one of the first time bins by at least an error HR threshold, but no two other raw HR values aggregated into the certain ones of the first time bins differ from each other by as much as the error HR threshold.
15. The WMM system of claim 14 , wherein
the error HR threshold is about 10%.
16. The WMM system of claim 12 , wherein
the error condition includes that one of the ECG electrodes is detected to be off.
17. The WMM system of claim 12 , wherein
the error condition includes that, in at least one of the two or more channels, a detected noise exceeds a noise threshold.
18. The WMM system of claim 12 , wherein
the one or more processors are further configured to:
replace 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 values of the certain one of the first time bins that is within a filter range of the certain one of the first time bins in the time sequence, but is not derived from the certain one of the first HR values.
19. The WMM system of claim 12 , further comprising:
a screen that is communicatively coupled to the processor,
the one or more processors are further configured to:
mark as error-prone at least some of the first HR values derived for first time bins from which raw HR values were discarded; and
display on the screen the first HR values, and
display on the screen error indicia in relation to the first HR values that are marked as error-prone.
20. The WMM system of claim 12 , wherein
the one or more processors are further configured to:
aggregate groups of the first time bins into respective second time bins; and
derive second HR values for respective ones of the second time bins, the second HR value of a certain one of the second time bins being derived from at least some of the first HR values of the first time bins that are aggregated into the certain one of the second time bins, and
wherein the second HR values are stored instead of the first HR values.
21. The WMM system of claim 20 , further comprising:
a screen that is communicatively coupled to the one or more processors,
wherein the one or more processors are further configured to:
mark as error-prone at least some of the second HR values derived for second time bins that include aggregated first time bins from which raw HR values were discarded;
display the second HR values; and
display error indicia in relation to the second HR values that are marked as error-prone.
22. A non-transitory computer-readable storage medium storing instructions for use by a wearable medical monitor system in monitoring a patient, the instructions when executed by the WMM system cause the WMM system to perform operations comprising:
receiving, from a WMM of the WMM system, WMM system data, wherein the WMM system includes an electrocardiogram (ECG) electrode and the WMM system data comprises data generated based, at least in part, on an ECG signal of the patient that was sensed by the ECG electrode for at least one hour;
computing raw heart rate (HR) values for respective ones of short ECG signal segments of the ECG signal;
aggregating groups of the computed raw HR values into respective first time bins that are arranged in a time sequence;
discarding, from their respective first time bins, the computed raw 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 the computed raw HR values aggregated and remaining into the certain one of the first time bins after the computed raw HR values that meet the error condition are discarded,
storing at least some of the first HR values.