Identifying reliable vectors

1. A wearable cardioverter defibrillator (WCD), comprising:

a support structure wearable by a patient;

a processor;

one or more electrocardiogram (ECG) sensors communicatively coupled with the processor and configured to be positioned on or proximate to the patient, at least in part, by the support structure; and

a discharge circuit configured to discharge a stored electrical charge through a body of the patient, the discharge circuit communicatively coupled with the processor;

the processor configured to:

receive, from the one or more ECG sensors, at least one ECG signal for a period of time from the patient;

analyze the at least one ECG signal to determine a first heart rate using a first method;

analyze the at least one ECG signal to determine a second heart rate using a second method different from the first method;

compare the first and second heart rates to each other;

determine a difference between the first and second heart rates;

determine, from the difference, whether a reliability threshold is satisfied;

classify the at least one ECG signal as reliable responsive to determining that the reliability threshold is satisfied; and

cause the discharge circuit to provide defibrillation therapy to the patient based, at least in part, on the at least one ECG signal being classified as reliable.

2. The WCD of claim 1 , wherein the processor is further configured to:

perform a rhythm analysis using at least the first heart rate when the at least one ECG signal is classified as reliable.

3. The WCD of claim 2 , wherein the processor is further configured to:

perform a rhythm analysis using a combination of the first and second heart rates of the at least one ECG signal including at least two ECG signals.

4. The WCD of claim 3 , wherein the at least two ECG signals are classified as reliable and the combination comprises a weighted average of the at least two ECG signals.

5. The WCD of claim 1 , wherein the first method is a time domain method and the second method is a frequency domain method.

6. The WCD of claim 1 , wherein the at least one ECG signal is classified as reliable when the first and second heart rates are within a predetermined number of beats.

7. The WCD of claim 6 , wherein the predetermined number of beats per minute is within five to fifteen beats per minute.

8. The WCD of claim 1 , wherein to determine, from the difference, whether the reliability threshold is satisfied, the processor is configured to determine whether the first and second heart rates are within a predetermined percentage difference.

9. The WCD of claim 8 , wherein the predetermined percentage difference is less than twenty percent.

10. The WCD of claim 9 , wherein the predetermined percentage difference is ten percent.

11. The WCD of claim 1 , wherein the processor is further configured to:

determine, from the difference, whether an unreliability threshold is satisfied; and

classify the at least one ECG signal as unreliable responsive to determining that the unreliability threshold is satisfied.

12. The WCD of claim 11 , wherein the unreliability threshold is equal to or greater than ten percent.

13. The WCD of claim 1 , wherein the first method includes one of an adaptive signal processing, Kalman filtering, independent component analysis, or principal component analysis.

14. The WCD of claim 1 , wherein the at least one ECG signal comprises three or more channels.

15. The WCD of claim 1 , wherein the at least one ECG signal includes two channels and the at least one ECG signal being classified as reliable when the two channels are classified as reliable.

16. The WCD of claim 15 , wherein the processor is further configured to:

perform a rhythm analysis using a combination of the first and second heart rates of the two channels.

17. The WCD of claim 16 , wherein the two channels are classified as reliable and the combination comprises a weighted average of the two channels.

18. The WCD of claim 1 , wherein the processor is further configured to:

receive physiological data from the patient for the period of time; and

analyze the physiological data to determine if a shockable condition is indicated.

19. The WCD of claim 18 , wherein the physiological data includes blood volume data.

20. The WCD of claim 19 , wherein the processor is further configured to:

determine whether the shockable condition is present based, at least in part, on the blood volume data.