Algorithm for detecting a seizure from cardiac data
First Claim
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1. A system, comprising:
- a cardiac data collector adapted to collect cardiac data from a patient'"'"'s heart, said cardiac data comprising a time series of fiducial time markers for candidate heartbeats;
a first module adapted to identify valid beats from said candidate heartbeats 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 heartbeat and at least one preceding heartbeat; and
accept as valid beats the candidate beats that pass said at least one beat validity test;
a second module adapted to form a first window comprising a first valid beat and at least one prior beat, wherein said first window is selected from;
a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and
a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15;
test said first window with at least one window test, wherein said at least one window test comprises a dispersion test; and
accept the beats in said window as suitable for seizure detection if said window has a dispersion less than a threshold level of dispersion;
a third module adapted to, in response to said beats in said window being accepted by said second module as suitable for seizure detection, determine a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said first window;
form a second window larger than said first window;
determine a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window;
determine a relative heart rate comprising at least one of a first ratio of said foreground to said background heart rate parameters and a second ratio of said background to said foreground heart rate parameters;
compare said relative heart rate to at least one of a first seizure threshold value associated with said first ratio and a second seizure threshold value associated with said second ratio; and
detect an epileptic seizure if at least one of said first ratio exceeds said first seizure threshold value, or said second ratio is below said second seizure threshold value; and
a medical device adapted to take a responsive action in response to said third module detecting an epileptic seizure, wherein the responsive action is selected from providing a warning to the patient or a caregiver, notifying the patient or the caregiver, logging the time of occurrence of said epileptic seizure, storing one or more seizure severity indices relating to said epileptic seizure, or treating said epileptic seizure.
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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
19 Claims
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1. A system, comprising:
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a cardiac data collector adapted to collect cardiac data from a patient'"'"'s heart, said cardiac data comprising a time series of fiducial time markers for candidate heartbeats; a first module adapted to identify valid beats from said candidate heartbeats 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 heartbeat and at least one preceding heartbeat; and
accept as valid beats the candidate beats that pass said at least one beat validity test;a second module adapted to form a first window comprising a first valid beat and at least one prior beat, wherein said first window is selected from;
a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and
a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15;
test said first window with at least one window test, wherein said at least one window test comprises a dispersion test; and
accept the beats in said window as suitable for seizure detection if said window has a dispersion less than a threshold level of dispersion;a third module adapted to, in response to said beats in said window being accepted by said second module as suitable for seizure detection, determine a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said first window;
form a second window larger than said first window;
determine a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window;
determine a relative heart rate comprising at least one of a first ratio of said foreground to said background heart rate parameters and a second ratio of said background to said foreground heart rate parameters;
compare said relative heart rate to at least one of a first seizure threshold value associated with said first ratio and a second seizure threshold value associated with said second ratio; and
detect an epileptic seizure if at least one of said first ratio exceeds said first seizure threshold value, or said second ratio is below said second seizure threshold value; anda medical device adapted to take a responsive action in response to said third module detecting an epileptic seizure, wherein the responsive action is selected from providing a warning to the patient or a caregiver, notifying the patient or the caregiver, logging the time of occurrence of said epileptic seizure, storing one or more seizure severity indices relating to said epileptic seizure, or treating said epileptic seizure. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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17. A system, comprising:
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a cardiac data collector adapted to collect cardiac data from a patient'"'"'s heart, said cardiac data comprising a time series of fiducial time markers for candidate heartbeats; a first module adapted to identify valid beats from said candidate heartbeats 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 heartbeat and at least one preceding heartbeat; and
accept as valid beats the candidate beats that pass said at least one beat validity test;a second module adapted to form a first window comprising a first valid beat and at least one prior valid beat, wherein said first window is selected from;
a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and
a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15; and
test said first window with at least one window test, wherein said at least one window test comprises determining whether the mean square error of a least squares linear fit of the beats in said first window is less than a threshold;a third module adapted to determine a foreground heart rate parameter comprising a statistical measure of central tendency of heart rate in said first window, in response to determining that the mean square error of a least squares linear fit of the beats in said first window is less than a threshold;
form a second window larger than said first window;
determine a background heart rate parameter comprising a statistical measure of central tendency of heart rate in said second window;
determine a relative heart rate comprising at least one of a first ratio of said foreground to said background heart rate parameters and a second ratio of said background to said foreground heart rate parameters;
compare said relative heart rate to at least one of a first seizure threshold value associated with said first ratio, a second seizure threshold value associated with said first ratio, a third seizure threshold value associated with said second ratio, and a fourth seizure threshold value associated with said second ratio; and
detect an epileptic seizure if at least one of said first ratio exceeds said first seizure threshold value, said first ratio is below said second seizure threshold value, said second ratio is below said first seizure threshold value, or said second ratio exceeds said second seizure threshold value; anda medical device adapted to take a responsive action in response to said third module detecting an epileptic seizure, wherein the responsive action is selected from providing a warning to the patient or a caregiver, notifying the patient or the caregiver, logging the time of occurrence of said epileptic seizure, storing one or more seizure severity indices relating to said epileptic seizure, or treating said epileptic seizure.
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18. A system, comprising:
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a cardiac data collection module adapted to collect cardiac data from a patient'"'"'s heart, said cardiac data comprising a time series of fiducial time markers for candidate heartbeats; a heartbeat determination module adapted to identify a series of candidate beat intervals from pairs of adjacent candidate heartbeats; a heartbeat validation module adapted to test at least a plurality of candidate heartbeats with at least one beat validity test selected from;
a) determining that a beat interval determined from said candidate heartbeat and the immediately preceding valid heartbeat is less than a maximum beat interval and greater than a minimum beat interval;
b) determining that a beat interval determined from said candidate heartbeat and the immediately preceding valid heartbeat is within an acceptable percentage of at least one of the immediately preceding beat interval or a recent short term beat interval measure; and
c) determining that a rate of change of heart rate determined from said candidate beat and a single immediately preceding heartbeat does not correspond to a rate of change of heart rate that is physiologically improbable; and
accept as valid beats each candidate heartbeat passing said at least one beat interval test;a window test module adapted to identify a plurality of beats suitable for seizure detection by forming a first window comprising a first valid beat and at least one preceding heartbeat, wherein said first window is selected from a time window of from 1 to 10 seconds, bounded on the most recent end by said first valid beat; and
a number of beats window comprising said first valid beat and a number of immediately preceding beats ranging from 2-15; and
test said beats in said first window with at least one window test, wherein said at least one window test comprises determining whether the mean square error of a least squares linear fit of the beats in said first window is less than a dispersion threshold;a foreground/background module adapted to determine, in response to determining that the mean square error of a least squares linear fit of the beats in said first window is less than said dispersion threshold, a foreground heart rate parameter comprising a statistical measure of central tendency in said first window;
form a background window larger than said first window; and
determine a background heart rate parameter comprising a statistical measure of central tendency in said background window;an epileptic seizure detection module adapted to determine a relative heart rate parameter comprising at least one of the ratio of said foreground to said background heart rate parameters and the ratio of said background to said foreground heart rate parameters;
compare said relative heart rate parameter to a seizure threshold value; and
detect the occurrence of an epileptic seizure event if said relative heart rate parameter crosses said seizure threshold value; anda medical device adapted to take a responsive action in response to said epileptic seizure detection module detecting an epileptic seizure event, wherein the responsive action is selected from providing a warning to the patient or a caregiver, notifying the patient or the caregiver, logging the time of occurrence of said epileptic seizure event, storing one or more seizure severity indices relating to said epileptic seizure event, or treating said epileptic seizure event. - View Dependent Claims (19)
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Specification