Systems and methods for cardiac segmentation analysis

Abstract

A system for the detection of cardiac events occurring in a human patient is provided. At least two electrodes are included in the system for obtaining an electrical signal from a patient's heart. An electrical signal processor is electrically coupled to the electrodes for processing the electrical signal. Electrical signals are acquired in segments and segment score rules are applied to the segments to classify them. To detect an abnormal cardiovascular condition, diagnostic rules are applied to the classification data. Patient state information modulates the acquisition of electrical data, the application of segment score rules, and the application of diagnostic rules.

1 . A device for tracking the cardiovascular condition of a human patient, the device including:
 a sensor adapted to sense the signal from the patient's heart, the signal being a waveform which is related to of a multiplicity of beats,   a digital processor configured to compute from the waveform a plurality of values of a heart signal feature, the digital processor further configured to (i) partition cardiac data corresponding to a plurality of heart beats into a plurality of cardiac segments, wherein the partitioning is performed according to patient state information; (ii) compute a segment score for each of the plurality of cardiac segments using at least one segment score rule, thereby generating a set of segment scores, wherein each segment score characterizes a feature of each of the cardiac segments; (iii) apply at least one diagnostic rule to the set of segment scores to detect the occurrence of a cardiac abnormality.   
   
   
       2 . The system of  claim 1  wherein the partitioning of cardiac data corresponding to a plurality of heart beats produces electrogram segments comprised of identical durations. 
   
   
       3 . The system of  claim 1  wherein the partitioning of cardiac data corresponding to a plurality of heart beats produces electrogram segments comprised of an identical number of heart beats. 
   
   
       4 . The system of  claim 1  wherein the partitioning of cardiac data corresponding to a plurality of heart beats produces electrogram segments which are programmably defined by the monitoring program to contain data related to a specified number of heart beats. 
   
   
       5 . The system of  claim 1  wherein the system also contains a sensing subsystem for sensing cardiac data that is obtained from an implanted sensor. 
   
   
       6 . The system of  claim 1  wherein cardiac data corresponds to a measurement of at least one of the following: electrogram; electrocardiogram; cardiac sound data; cardiac data measured from a strain gauge; cardiac data measured from a pressure gauge; optical data measured from the heart; flow data; and chemical data measured from a chemical sensor. 
   
   
       7 . The system of  claim 1  wherein each of the set of said segment scores is computed using at least two segment score rules each rule relating to a different characteristics of the cardiac data within the cardiac segment. 
   
   
       8 . The system of  claim 7  wherein said segment score rules each relates to at least one of the following: st-elevation; QRS complexity; a QRS integration measure; flow rate;
 and, flow rate at different times during each heart-beat.   
   
   
       9 . The system of  claim 1  wherein the segment scores are binary and indicate one of normal and abnormal. 
   
   
       10 . The system of  claim 1  wherein the segment scores are quantitative and indicate a degree of abnormality. 
   
   
       11 . The system of  claim 1  wherein the cardiac abnormality is one of: reflective of ischemia; related to ischemia; predictive of impending ischemia; and, reflective of recent ischemia. 
   
   
       12 . A device for tracking the cardiovascular condition of a human patient, the device including:
 an electrode adapted to sense the electrical signal from the patient's heart, the electrical signal being a waveform which consists of a multiplicity of beats,   a digital processor configured to compute from the waveform a plurality of values of a heart signal feature, the digital processor further configured to (i) partition cardiac data corresponding to a plurality of heart beats into a plurality of cardiac segments; (ii) compute a segment score for each of the plurality of cardiac segments using at least one segment score rule, thereby generating a set of segment scores, wherein each segment score characterizes a feature of each of the cardiac segments, and wherein the segment score depends on patient state information; (iii) apply at least one diagnostic rule to the set of segment scores to detect the occurrence of a cardiac abnormality.   
   
   
       13 . The system of  claim 12  wherein the segment scores are binary and indicate one of normal and abnormal. 
   
   
       14 . The system of  claim 12  wherein the segment scores are quantitative and indicate a degree of abnormality. 
   
   
       15 . The system of  claim 12  wherein the diagnostic rule detects the cardiac abnormality if both a first detection criterion and a second detection criterion are satisfied, and wherein the first detection criterion requires N1 number of segment scores to have a characteristic which is above a first threshold and a second criterion requires N2 number of segment scores to have the characteristic which is above a second higher threshold. 
   
   
       16 . The system of  claim 15  wherein N1 is smaller than N2. 
   
   
       17 . The system of  claim 12  wherein the diagnostic rule is modified as a function of heart rate. 
   
   
       18 . The system of  claim 12  wherein at least one of the first threshold or the second threshold is modified as a function of at least one of the following: heart rate; recent patient activity levels; recent history of patient heart rate; and, a patient state value. 
   
   
       19 . The system of  claim 15  wherein the N1 number of segment scores must occur sequentially. 
   
   
       20 . The system of  claim 15  wherein the N1 number of segment scores must occur within a specified time-period. 
   
   
       21 . The system of  claim 12  wherein the diagnostic rule detects the cardiac abnormality if either a first detection criterion or a second detection criterion is satisfied, and wherein the first detection criterion requires N1 number of segment scores to have a characteristic which is above a first threshold and a second criterion requires N2 number of segment scores to have the characteristic which is above a second higher threshold. 
   
   
       22 . The system of  claim 12  wherein said at least one segment score is computed using at least one of an intra-beat segment score rule or an inter-beat segment score rule. 
   
   
       23 . The system of  claim 22  wherein the intra-beat segment score rule evaluates a characteristic within each beat, said characteristic being at least one of: st-deviation; a characteristic which pertains to cardiac repolarization; a characteristic which pertains to cardiac depolarization; or, QRST complexity. 
   
   
       24 . The system of  claim 22  wherein the inter-beat segment score rule evaluates a characteristic across a plurality of beats, said characteristic being at least one of: heart rate; heart rate variability; and QRS variance of all the beats in the segment. 
   
   
       25 . The system of  claim 24  wherein the beats are obtained from electrogram data. 
   
   
       26 . The system of  claim 24  wherein the beats are obtained from electrocardiogram data obtained from an electrode recorded from one of: an external device, and a subdermally located device. 
   
   
       27 . A device for tracking the cardiovascular condition of a human patient, the device including:
 a sensor adapted to sense a signal from the patient's heart, the signal being a waveform which consists of a multiplicity of beats,   a digital processor configured to compute from the waveform a plurality of values of a heart signal feature, the digital processor further configured to (i) partition cardiac data corresponding to a plurality of heart beats into a plurality of cardiac segments; (ii) compute a segment score for each of the plurality of cardiac segments using at least one segment score rule, thereby generating a set of segment scores, wherein each segment score characterizes a feature of each of the cardiac segments; (iii) apply at least one diagnostic rule to the set of segment scores to generate a diagnostic score indicative of the patient's cardiovascular condition, (iv) generate a patient state index parameter based at least in part on the diagnostic score; and (v) use the patient state index parameter to modulate at least one of the actions specified in subparagraphs (i) through (iii) above.   
   
   
       28 . The device for tracking the cardiovascular condition of a human patient, of  claim 27  wherein the diagnostic rule utilizes a self-normative value of the patient which is selected according to the patient state index parameter.