ALGORITHM FOR DETECTING A SEIZURE FROM CARDIAC DATA
First Claim
1. A computer readable program storage unit encoded with instructions that, when executed by a computer, perform a method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
- obtaining a time series of fiducial time markers for candidate heart beats;
identifying valid beats from said candidate heart beats by subjecting a plurality of candidate beats to at least one beat validity test, said at least one beat validity test comprising at least one beat interval test applied to a candidate beat interval derived from a candidate heart beat and at least one preceding heart beat; and
accepting as valid beats the candidate beats that pass said at least one beat validity test;
identifying valid beats suitable for seizure detection by forming a first window for each valid beat, said first window comprising a first valid beat and at least one preceding heart beat;
testing said first window with at least one window test; and
accepting as suitable for seizure detection said first valid beat from each said first window that passes said at least one window test; and
detecting an epileptic seizure by at least one of;
(1) forming a second window for each valid beat suitable for seizure detection, said second window comprising a first valid beat suitable for seizure detection and at least one prior valid beat suitable for seizure detection;
determining a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window;
forming a third window for each valid beat suitable for seizure detection, said third window comprising said first valid beat suitable for seizure detection from said second window and at least two prior valid beats suitable for seizure detection;
determining a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said third window;
determining a relative heart rate comprising at least one of the ratio of said foreground and said background heart rate parameters and the ratio of said background and said foreground heart rate parameters; and
comparing said relative heart rate to a first seizure threshold value associated with an epileptic seizure event;
(2) a) determining at least one short-term heart rate comprising at least one ofi) a first instantaneous heart rate from said first valid beat and the immediately preceding valid beat, orii) a fourth window heart rate comprising a statistical measure of central tendency of heart rate using said valid beats in said fourth window; and
b) comparing said at least one short-term heart rate to a short-term heart rate threshold associated with an epileptic seizure event;
or(3) a) determining a fifth window heart rate comprising a statistical measure of central tendency of heart rate using said valid beats in said fifth window;
b) determining a slope of the least squares linear fit of the valid beats in said fifth window;
c) comparing said fifth window heart rate to at least one of an upper fifth window heart rate threshold and a lower fifth window heart rate threshold associated with an epileptic seizure event;
d) comparing said slope of the least squares linear fit of said valid beats in said fifth window to at least one of a lower slope threshold and an upper slope threshold associated with an epileptic seizure event;
further comprising, if at least one of said relative heart rate exceeds said first seizure threshold value, said short-term heart rate exceeds said short-term heart rate seizure threshold value, said fifth window heart rate is below said upper fifth window heart rate threshold, said fifth window heart rate exceeds said lower fifth window heart rate threshold, said slope of said least squares linear fit is below said upper slope threshold, or said slope of said least squares linear fit exceeds said lower slope threshold, indicating the occurrence of a seizure event.
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Abstract
Methods, systems, and apparatus for detecting the seizure in a patient using a medical device. The determination is performed by collecting cardiac data; determining valid heart beats suitable for seizure detection from the cardiac data; calculating heart rate data of interest from the valid heart beats; and identifying a seizure event from the heart rate data. The medical device may then take a responsive action, such as warning, logging the time of the seizure, computing and storing one or more seizure severity indices, and/or treating the seizure.
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Citations
24 Claims
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1. A computer readable program storage unit encoded with instructions that, when executed by a computer, perform a method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
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obtaining a time series of fiducial time markers for candidate heart beats; identifying valid beats from said candidate heart beats by subjecting a plurality of candidate beats to at least one beat validity test, said at least one beat validity test comprising at least one beat interval test applied to a candidate beat interval derived from a candidate heart beat and at least one preceding heart beat; and accepting as valid beats the candidate beats that pass said at least one beat validity test; identifying valid beats suitable for seizure detection by forming a first window for each valid beat, said first window comprising a first valid beat and at least one preceding heart beat; testing said first window with at least one window test; and accepting as suitable for seizure detection said first valid beat from each said first window that passes said at least one window test; and detecting an epileptic seizure by at least one of; (1) forming a second window for each valid beat suitable for seizure detection, said second window comprising a first valid beat suitable for seizure detection and at least one prior valid beat suitable for seizure detection; determining a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window; forming a third window for each valid beat suitable for seizure detection, said third window comprising said first valid beat suitable for seizure detection from said second window and at least two prior valid beats suitable for seizure detection; determining a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said third window; determining a relative heart rate comprising at least one of the ratio of said foreground and said background heart rate parameters and the ratio of said background and said foreground heart rate parameters; and comparing said relative heart rate to a first seizure threshold value associated with an epileptic seizure event; (2) a) determining at least one short-term heart rate comprising at least one of i) a first instantaneous heart rate from said first valid beat and the immediately preceding valid beat, or ii) a fourth window heart rate comprising a statistical measure of central tendency of heart rate using said valid beats in said fourth window; and b) comparing said at least one short-term heart rate to a short-term heart rate threshold associated with an epileptic seizure event; or (3) a) determining a fifth window heart rate comprising a statistical measure of central tendency of heart rate using said valid beats in said fifth window; b) determining a slope of the least squares linear fit of the valid beats in said fifth window; c) comparing said fifth window heart rate to at least one of an upper fifth window heart rate threshold and a lower fifth window heart rate threshold associated with an epileptic seizure event; d) comparing said slope of the least squares linear fit of said valid beats in said fifth window to at least one of a lower slope threshold and an upper slope threshold associated with an epileptic seizure event; further comprising, if at least one of said relative heart rate exceeds said first seizure threshold value, said short-term heart rate exceeds said short-term heart rate seizure threshold value, said fifth window heart rate is below said upper fifth window heart rate threshold, said fifth window heart rate exceeds said lower fifth window heart rate threshold, said slope of said least squares linear fit is below said upper slope threshold, or said slope of said least squares linear fit exceeds said lower slope threshold, indicating the occurrence of a seizure event. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A computer readable program storage unit encoded with instructions that, when executed by a computer, perform a method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
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obtaining a time series of fiducial time markers for candidate heart beats; identifying valid beats from said candidate heart beats by subjecting a plurality of candidate beats to at least one beat validity test, said at least one beat validity test comprising at least one beat interval test applied to a candidate beat interval derived from a candidate heart beat and at least one preceding heart beat; and accepting as valid beats the candidate beats that pass said at least one beat validity test; and detecting an epileptic seizure by at least one of; (1) forming a second window for each valid beat, said second window comprising a first valid beat and at least one prior valid beat; determining a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window; forming a third window for each valid beat, said third window comprising said first valid beat from said second window and at least two prior valid beats; determining a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said third window; determining a relative heart rate comprising at least one of the ratio of said foreground and said background heart rate parameters and the ratio of said background and said foreground heart rate parameters; and comparing said relative heart rate to a first seizure threshold value associated with an epileptic seizure event; (2) a) determining at least one short-term heart rate comprising at least one of i) a first instantaneous heart rate from said first valid beat and the immediately preceding valid beat, or ii) a fourth window heart rate comprising a statistical measure of central tendency of heart rate using said valid beats in said fourth window; and b) comparing said at least one short-term heart rate to a short-term heart rate threshold associated with an epileptic seizure event; or (3) a) determining a fifth window heart rate comprising a statistical measure of central tendency of heart rate using said valid beats in said fifth window; b) determining a slope of the least squares linear fit of the beats in said fifth window; c) comparing said fifth window heart rate to at least one of an upper fifth window heart rate threshold and a lower fifth window heart rate threshold associated with an epileptic seizure event; and d) comparing said slope of the least squares linear fit of said valid beats in said fifth window to at least one of a lower slope threshold and an upper slope threshold associated with an epileptic seizure event; further comprising, if at least one of said relative heart rate exceeds said first seizure threshold value, said short-term heart rate exceeds said short-term heart rate seizure threshold value, said fifth window heart rate is below said upper fifth window heart rate threshold, said fifth window heart rate exceeds said lower fifth window heart rate threshold, said slope of said least squares linear fit is below said upper slope threshold, or said slope of said least squares linear fit exceeds said lower slope threshold, indicating the occurrence of a seizure event.
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19. A computer readable program storage unit encoded with instructions that, when executed by a computer, perform a method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart, the method comprising:
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obtaining a time series of fiducial time markers for patient heart beats; and detecting an epileptic seizure by at least one of; (1) forming a second window for each patient heart beat, said second window comprising a first heart beat and at least one prior heart beat; determining a foreground heart rate parameter comprising a target percentile value in a uniform distribution Percentile Tracking Filter of heart rate in said second window; forming a third window for each patient heart beat, said third window comprising said first heart beat from said second window and at least two prior heart beats; determining a background heart rate parameter comprising a target percentile value in a uniform distribution Percentile Tracking Filter of heart rate in said third window; determining a relative heart rate comprising at least one of the ratio of said foreground and said background heart rate parameters and the ratio of said background and said foreground heart rate parameters; and comparing said relative heart rate to a first seizure threshold value associated with an epileptic seizure event; (2) a) determining at least one short-term heart rate comprising at least one of i) a first instantaneous heart rate from said first heart beat and the immediately preceding heart beat, or ii) a fourth window heart rate comprising a target percentile value in a uniform distribution Percentile Tracking Filter of heart rate using said heart beats in said fourth window; and b) comparing said at least one short-term heart rate to a short-term heart rate threshold associated with an epileptic seizure event; and (3) a) determining a fifth window heart rate comprising a target percentile value in a uniform distribution Percentile Tracking Filter of heart rate using said heart beats in said fifth window; b) determining a slope of the least squares linear fit of the beats in said fifth window; c) comparing said fifth window heart rate to at least one of an upper fifth window heart rate threshold and a lower fifth window heart rate threshold associated with an epileptic seizure event; and d) comparing said slope of the least squares linear fit of said heart beats in said fifth window to at least one of a lower slope threshold and an upper slope threshold associated with an epileptic seizure event; further comprising, if at least one of said relative heart rate exceeds said first seizure threshold value, said short-term heart rate exceeds said short-term heart rate seizure threshold value, said fifth window heart rate is below said upper fifth window heart rate threshold, said fifth window heart rate exceeds said lower fifth window heart rate threshold, said slope of said least squares linear fit is below said upper slope threshold, or said slope of said least squares linear fit exceeds said lower slope threshold, indicating the occurrence of a seizure event. - View Dependent Claims (20, 21, 22, 23)
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24. A method for detecting epileptic seizures based upon a time of beat sequence of the patient'"'"'s heart comprising:
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obtaining a time of beat sequence for a series of candidate heart beats; identifying a series of candidate beat intervals from pairs of adjacent candidate heart beats; testing at least a plurality of candidate beat intervals with at least one beat interval test selected from a) determining that said candidate beat interval is less than a maximum beat interval and greater than a minimum beat interval; b) determining that said candidate beat interval is within an acceptable percentage of at least one of the immediately preceding beat interval or a recent short term beat interval measure; c) determining that the slope of the current candidate beat interval does not correspond to a rate of change of heart rate that is physiologically improbable; accepting as valid beats each pair of candidate heart beats from each candidate beat interval passing said at least one beat interval test; forming a foreground window defined by at least one of a) a duration of 30 seconds or less; and b) from 2-90 beats; determining a foreground heart rate parameter comprising a statistical measure of central tendency in said foreground window; forming a background window defined by at least one of a) a duration exceeding the duration of the foreground window; and b) a number of beats exceeding the number of beats in said foreground window; determining a background heart rate parameter comprising a statistical measure of central tendency in said background window; determining a relative heart rate parameter comprising at least one of the ratio of said foreground and said background heart rate parameters and the ratio of said background and said foreground heart rate parameters; comparing said relative heart rate parameter to a seizure threshold value; and indicating the occurrence of a seizure event if said relative heart rate parameter exceeds said seizure threshold value.
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Specification