Method, apparatus and system for validating and quantifying cardiac beat data quality

1. A non-transitory computer readable program storage unit encoded with instructions that, when executed by a computer, perform a method for quantifying the quality of a fiducial time marker for a candidate heart beat, comprising:

obtaining a fiducial time marker for a candidate heart beat in a first time series of candidate heart beats;

setting a beat quality index for said candidate heart beat to a first value;

testing said candidate heart beat with a first beat validity test;

setting said beat quality index to a second value indicative of whether said first beat validity test was passed;

testing said candidate heart beat with a second beat validity test;

setting said beat quality index to a third value indicative of whether said second beat validity test was passed;

performing at least one responsive action based upon the value of said beat quality index, the responsive action selected from the group consisting of

indicating the occurrence of an epileptic seizure event;

delivering a neurostimulation therapy to the patient to treat an epileptic seizure event;

warning at least one of a caregiver, the patient, or a physician; and

logging said beat quality index to a memory.

2. The non-transitory computer readable program storage unit of claim 1 wherein indicating the occurrence of an epileptic seizure event based upon at least one of

a) the result of at least one of said first and said second beat validity tests; or

b) a first heart rate parameter determined from candidate heart beats in a first window, and a second heart rate parameter determined from candidate heart beats in a second window.

3. The non-transitory computer readable program storage unit of claim 1 wherein delivering a neurostimulation therapy comprises one of

initiating a programmed neurostimulation therapy; and

modifying a programmed neurostimulation therapy to obtain a second neurostimulation therapy and applying said second neurostimulation therapy to a target neural structure.

4. The non-transitory computer readable program storage unit of claim 1 , wherein the method further comprises modifying an earlier responsive action based upon a value of a second beat quality index.

5. The non-transitory computer readable program storage unit of claim 1 , wherein the first beat validity test and the second beat validity test are selected from a library of beat validity tests.

6. The non-transitory computer readable program storage unit of claim 1 , wherein at least one of said first and said second beat validity tests is a window test; and

wherein said window is one of a time window, a number of beats window, or an exponentially forgetting window having a first timeframe.

7. The non-transitory computer readable program storage unit of claim 1 , wherein the method further comprises storing beat quality index values for a plurality of candidate heart beats in said first time series as a second time series.

8. The non-transitory computer readable program storage unit of claim 1 , wherein the method further comprises

determining a third window;

determining a beat quality index for each candidate heart beat in said third window;

determining a window beat quality index, said window beat quality index comprising a statistical measure of central tendency of said beat quality indices for the candidate heart beats in said third window; and

logging said statistical measure of central tendency.

9. The non-transitory computer readable program storage unit of claim 8 , wherein said third time window begins at a time between 30 minutes before said seizure and 30 minutes after said seizure and has a duration from about 5 seconds to about 2 hours.

10. The non-transitory computer readable program storage unit of claim 1 , wherein each of said first beat validity test and said second beat validity test comprise a plurality of tests.

11. The non-transitory computer readable program storage unit of claim 6 , further comprising:

setting the first value to a first integer;

calculating an interbeat interval between said candidate heart beat and an immediately preceding candidate heart beat;

wherein said first beat validity test is selected from the group consisting of:

a) testing whether the interbeat interval falls within a range of physiologically plausible interbeat intervals;

b) testing whether the interbeat interval is less than an upper interbeat interval threshold;

c) testing whether the interbeat interval is greater than a lower interbeat interval threshold; and

d) testing whether a slope of change between the interbeat interval and one or more preceding interbeat intervals falls within a range of physiologically plausible slopes of change;

wherein setting said beat quality index to said second value comprises adding 1 to the first value.

12. The non-transitory computer readable program storage unit of claim 6 , further comprising:

setting the first value to a first integer;

wherein the at least one window test is said second beat validity test, and wherein said second beat validity test determines at least one of

a) whether a first heart rate variability measure of a plurality of candidate heart beats in said window is less than or equal to a predetermined heart rate variability threshold; and

b) whether said window contains a sufficient number of candidate heart beats determined to be within a range of physiologically plausible heart beats;

wherein setting said beat quality index to said third value comprises adding 1 to the beat quality index if said window passes the at least one window test.

13. A method for quantifying the quality of a candidate heart beat, comprising:

obtaining a fiducial time marker for a candidate heart beat;

testing said candidate heart beat with a first beat validity test;

setting said beat quality index to a first value indicative of whether said first beat validity test was passed;

testing said candidate heart beat with a second beat validity test;

setting said beat quality index to a second value indicative of whether said second beat validity test was passed; and

performing at least one responsive action based upon the value of said beat quality index, the responsive action selected from the group consisting of:

indicating the occurrence of an epileptic seizure event;

delivering a neurostimulation therapy to the patient to treat a medical condition;

warning at least one of a caregiver, the patient, or a physician; and

logging said beat quality index to a memory.

14. The method of claim 13 wherein indicating the occurrence of an epileptic seizure event is based upon at least one of:

a) the result of at least one of said first and said second beat validity tests; or

b) a first heart rate parameter determined from candidate heart beats in a first window, and a second heart rate parameter determined from candidate heart beats in a second window.

15. The method of claim 13 , wherein said first heart rate parameter comprises a statistical measure of central tendency of heart rate in said first time window, and wherein said first time window has a duration of from about 2 seconds to about 30 seconds; and

wherein said second heart rate parameter comprises a statistical measure of central tendency of heart rate within said second time window, and wherein said second time window has a duration of from about 30 seconds to about 86,400 seconds.

16. The method of claim 13 further comprising:

calculating an interbeat interval between said candidate heart beat and an immediately preceding candidate heart beat;

wherein said first beat validity test is selected from the group consisting of:

a) testing whether the interbeat interval falls within a range of physiologically plausible interbeat intervals;

b) testing whether the interbeat interval is less than an upper interbeat interval threshold;

c) testing whether the interbeat interval is greater than a lower interbeat interval threshold; and

d) testing whether a slope of change between the interbeat interval and one or more preceding interbeat intervals falls within a range of physiologically plausible slopes of change;

wherein setting said beat quality index to said second value comprises setting said beat quality index to a value indicative of the outcome of said first beat validity test.

17. The method of claim 13 wherein delivering a neurostimulation therapy to the patient to treat a medical condition comprises applying vagus nerve stimulation therapy to said patient.

18. A method for quantifying the quality of a candidate heart beat, comprising:

receiving a reference time marker for a signal portion representative of a candidate heart beat;

determining a first quality criterion for validating said candidate heart beat;

testing said candidate heart beat with a first beat validity test using at least said first quality criterion;

determining a second quality criterion for validating said candidate heart beat;

testing said candidate heart beat with a second beat validity test using at least said second quality criterion;

associating a beat quality certification to said candidate heart beat based on said first and second beat validity tests; and

performing at least one responsive action based upon the value of said beat quality certification, the responsive action selected from the group consisting of:

indicating the occurrence of an epileptic seizure event;

delivering a neurostimulation therapy to the patient to treat a medical condition;

warning at least one of a caregiver, the patient, or a physician; and

logging said beat quality index to a memory.

19. The method of claim 18 , wherein said first and second quality criteria comprise first and second thresholds.

20. The method of claim 18 further comprising:

calculating an interbeat interval between said candidate heart beat and an immediately preceding candidate heart beat;

wherein said first and second beat validity tests are selected from the group consisting of:

a) testing whether the interbeat interval falls within a range of physiologically plausible interbeat intervals;

b) testing whether the interbeat interval is less than an upper interbeat interval threshold;

c) testing whether the interbeat interval is greater than a lower interbeat interval threshold; and

d) testing whether a slope of change between the interbeat interval and one or more preceding interbeat intervals falls within a range of physiologically plausible slopes of change;

wherein associating a beat quality certification to said candidate heart beat based on said first and second beat validity tests comprises setting said beat quality index to a value indicative of the outcome of said first and said second beat validity tests.

21. The method of claim 20 further comprising:

testing said candidate heart beat with a third beat validity test, and wherein associating a beat quality certification to said candidate heart beat comprises setting said beat quality index to a value indicative of the outcome of said first, said second, and said third beat validity tests.

22. The method of claim 18 further comprising testing said candidate heart beat with at least a third beat validity test;

and wherein associating a beat quality certification to said candidate heart beat comprises setting said beat quality index to a unique value indicative of the outcome of each of said plurality of beat validity tests.