Abstract: A method of discriminating between ischemic and cardiac memory effects in a heart, comprising receiving electrocardiographic (ECG) data, calculating, from the ECG data, a direction of a T-wave vector, diagnosing ischemia if the T-wave vector is between about 75 degrees and about 200 degrees, and diagnosing cardiac memory if the T-wave vector is between about zero degrees and minus 90 degrees. Also presented is a system for discriminating between ischemic and cardiac memory effects in a heart comprising means for performing an electrocardiogram, means for calculating a direction of a T-wave vector, means for diagnosing ischemia if the T-wave vector is between about 90 degrees and 180 degrees, and means for diagnosing cardiac memory if the T-wave vector is between about zero degrees and minus 90 degrees.

Abstract: A system for heart performance characterization and abnormality detection includes an acquisition device for acquiring an electrophysiological signal representing heart beat cycles of a patient heart. A detector detects one or more parameters of the electrophysiological signal of parameter type comprising at least one of, (a) amplitude, (b) time duration, (c) peak frequency and (d) frequency bandwidth, of multiple different portions of a single heart beat cycle of the heart beat cycles selected in response to first predetermined data. The multiple different portions of the single heart beat cycle being selected from, a P wave portion, a QRS complex portion, an ST segment portion and a T wave portion in response to second predetermined data. A signal analyzer calculates a ratio of detected parameters of a single parameter type of the multiple different portions of the single heart beat cycle.

Abstract: Pattern classification techniques are provided for use with an implantable medical device for detecting cardiac ischemia substantially in real-time. Values representative of morphological features of electrical cardiac signals are detected by the implantable medical device. Then, a determination is made as to whether the patient is subject to an on-going episode of cardiac ischemia by applying the values to a pattern classifier configured to identify patterns representative of cardiac ischemia. In one example, the determination is made substantially in real-time by the device itself based on the IEGM signals it detects. In other examples, the IEGM signals are relayed promptly to a bedside monitor or other external device, which analyzes the signals using the pattern classifier to detect ischemia. Therapy may be applied in response to cardiac ischemia. For example, if the implanted device is equipped with a drug pump, appropriate medications may be administered such as anti-thrombolytics.

Abstract: Disclosed is a “tracker system” that includes implanted electrical leads which are part of an implanted cardiotracker plus external equipment that includes external alarm means and a physician's programmer. The tracker system is designed to monitor the degradation of a patient's cardiovascular condition from one or more causes. These causes include the rejection of a transplanted heart and/or the progression of a stenosis in a coronary artery. As one or more stenoses in a coronary artery become progressively more narrow thereby causing reduced blood flow to the heart muscle coronary circulation, the tracker system can alert the patient by either or both internal and/or external alarm means to take the appropriate medical action. The physician's programmer can be used to display histograms of key heart signal parameters that are indicative of the patient's cardiovascular condition.

Abstract: An implantable medical device and associated method assess T-wave alternans by sensing a cardiac electrogram (EGM) signal and selecting a pair of consecutive T-wave signals from the EGM signal. A first amplitude and a second amplitude from each of the consecutive T-wave signals are determined. The differences between the first amplitudes and the second amplitudes of the consecutive T-wave signal pairs are used to compute a T-wave alternans metric.

Abstract: A system comprising a processor that includes a cardiac signal vector module and an ischemia detection module. The cardiac signal vector module is configured to measure a first dominant vector corresponding to a direction and magnitude of maximum signal power of a first segment of at least one cardiac cycle of a subject and at least a second dominant vector corresponding to a direction and magnitude of maximum signal power of a second segment of the cardiac cycle from an electrical cardiac signal. The ischemia detection module is configured to measure a change in the first dominant vector, to form a difference by subtracting a measured change in the second dominant vector from a measured change in the first dominant vector, and to declare whether an ischemic event occurred using the difference.

Abstract: Techniques are described for detecting and distinguishing among ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. In one technique, these conditions are detected and distinguished based on an analysis of: the interval between the QRS complex and the peak of a T-wave (QTmax), the interval between the QRS complex and the end of a T-wave (QTend), alone or in combination with a change in ST segment elevation. By exploiting QTmax and QTend in combination with ST segment elevation, changes in ST segment elevation caused by hypo/hyperglycemia can be properly distinguished from changes caused by cardiac ischemia. In another technique, hyperglycemia and hypoglycemia are predicted, detected and/or distinguished from one another based on an analysis of the amplitudes of P-waves, QRS-complexes and T-waves within the IEGM. Appropriate warning signals are delivered and therapy is automatically adjusted.

Abstract: Techniques are described for detecting ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. Ischemia is detected based on a shortening of the interval between the QRS complex and the end of a T-wave (QTmax), alone or in combination with a change in ST segment elevation. Alternatively, ischemia is detected based on a change in ST segment elevation combined with minimal change in the interval between the QRS complex and the end of the T-wave (QTend). Hypoglycemia is detected based on a change in ST segment elevation along with a lengthening of either QTmax or QTend. Hyperglycemia is detected based on a change in ST segment elevation along with minimal change in QTmax and in QTend. By exploiting QTmax and QTend in combination with ST segment elevation, changes in ST segment elevation caused by hypo/hyperglycemia can be properly distinguished from changes caused by ischemia.

Abstract: Techniques are described for detecting ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. Ischemia is detected based on a shortening of the interval between the QRS complex and the end of a T-wave (QTmax), alone or in combination with a change in ST segment elevation. Alternatively, ischemia is detected based on a change in ST segment elevation combined with minimal change in the interval between the QRS complex and the end of the T-wave (QTend). Hypoglycemia is detected based on a change in ST segment elevation along with a lengthening of either QTmax or QTend. Hyperglycemia is detected based on a change in ST segment elevation along with minimal change in QTmax and in QTend. By exploiting QTmax and QTend in combination with ST segment elevation, changes in ST segment elevation caused by hypo/hyperglycemia can be properly distinguished from changes caused by ischemia.

Abstract: Disclosed is a system for the detection of cardiac events that includes an implanted device called a cardiosaver, a physician's programmer and an external alarm system. The system is designed to provide early detection of cardiac events such as acute myocardial infarction or exercise induced myocardial ischemia caused by an increased heart rate or exertion. The system can also alert the patient with a less urgent alarm if a heart arrhythmia is detected. Using different algorithms, the cardiosaver can detect a change in the patient's electrogram that is indicative of a cardiac event within five minutes after it occurs and then automatically warn the patient that the event is occurring. To provide this warning, the system includes an internal alarm sub-system (internal alarm means) within the cardiosaver and/or an external alarm system (external alarm means) which are activated after the ST segment of the electrogram exceeds a preset threshold.

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 and a patient alarm means is further provided and electrically coupled to the electrical signal processor. The electrical signal is acquired in the form of electrogram segments, which are categorized according to heart rate, ST segment shift and type heart rhythm (normal or abnormal). Baseline electrogram segments are tracked over time.

Abstract: In a method for determining a cardiac condition, a sensed physiologic signal for a period of time including multiple cardiac cycles is received. Using the received physiologic data, a heart beat frequency to be used as a reference frequency is determined. A plurality of harmonics of the received physiologic signal is extracted based on the reference frequency, wherein the harmonics correspond to a plurality of alternans frequencies. Amplitudes of at least some of the extracted harmonics are determined, and are used to determine an alternans indicator value.

Abstract: Real time cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed in real time in a useful form on a computer screen or monitor. The monitor displays the high frequency data from the QRS complex in units of microvolts, juxtaposed with a display of conventional ECG data in units of millivolts or microvolts. The high frequency data are analyzed for their root mean square (RMS) voltage values and the discrete RMS values and related parameters are displayed in real time. The high frequency data from the QRS complex are analyzed with imbedded algorithms to determine the presence or absence of reduced amplitude zones, referred to herein as “RAZs”. RAZs are displayed as “go, no-go” signals on the computer monitor. The RMS and related values of the high frequency components are displayed as time varying signals, and the presence or absence of RAZs may be similarly displayed over time.

Abstract: Techniques are described for detecting and distinguishing among ischemia, hypoglycemia or hyperglycemia based on intracardiac electrogram (IEGM) signals. In one technique, these conditions are detected and distinguished based on an analysis of: the interval between the QRS complex and the peak of a T-wave (QTmax), the interval between the QRS complex and the end of a T-wave (QTend), alone or in combination with a change in ST segment elevation. By exploiting QTmax and QTend in combination with ST segment elevation, changes in ST segment elevation caused by hypo/hyperglycemia can be properly distinguished from changes caused by cardiac ischemia. In another technique, hyperglycemia and hypoglycemia are predicted, detected and/or distinguished from one another based on an analysis of the amplitudes of P-waves, QRS-complexes and T-waves within the IEGM. Appropriate warning signals are delivered and therapy is automatically adjusted.

Abstract: Method and apparatus for detecting cardiac repolarization abnormality using at least one electrocardiogram signal. The at least one electrocardiogram signal can be obtained from any number of continuous or non-continuous windows. The method can include deriving a total quantity of representative beats of the at least one electrocardiogram signal. At least one morphology shape descriptor can be used to determine a total quantity of values representing the total quantity of representative beats. Data corresponding to at least some of the total quantity of values can be used to assess cardiac repolarization abnormality.

Abstract: Categories are established for use in physiological monitoring devices and these categories are prioritized such that data indicative of a critical event self-triggers a communication to an external receiver for the purpose of re-transmitting the critical data for use by a clinician. The categories can be established by the clinician and, if desired, the precise monitored data parameters can be assigned to specific categories. Far-field transmission can be used to send certain stored data to an external receiver, provision is made for externally charging the device batteries.

Abstract: An implantable medical device includes an arrhythmia detection and classification system that classifies an arrhythmia episode based on an irregularity parameter and/or a complexity parameter. The arrhythmia episode is detected from a cardiac signal. The irregularity parameter is indicative of the degree of cycle length irregularity of the cardiac signal and the complexity parameter is indicative of the degree of morphological complexity of the cardiac signal. One example of the irregularity parameter is an irregularity sample entropy, or a parameter related to the irregularity sample entropy, computed to indicate the cycle length irregularity. One example of the complexity parameter is a complexity sample entropy, or a parameter related to the complexity sample entropy, computed to indicate the morphological complexity. In one embodiment, the detected arrhythmia episode is classified using both the irregularity parameter and the complexity parameter.

Abstract: A system or a method for analysing ECG curvature wherein at least one among a number of different parameters is isolated, for indicating symptoms of diseases having influence on the ECG curvature. The system and method provides for objective, fast and effective indication of a number of symptoms derivable from an ECG curve which may be indicative of one or more diseases. This can be achieved when a first number of selected parameters are combined in at least a first mathematical analysis, where the result of the analysis can be represented as a point in a coordinate system comprising at least two axes where the system can compare the actual placement in the coordinate system with a number of reference parameters stored in the system for indicating diseases having influence on the ECG curvature.

Abstract: A system for automatically evaluating the sensing and detection of physiological processes by an implantable medical device, such as an implantable cardiac stimulation device. The system includes an automatic testing algorithm which iteratively adjusts at least one of the threshold and gain settings of the device and evaluates the accuracy of the detection for refining the programming of the device. The algorithm can include sampling the physiological process beginning at a relatively low rate to avoid excessive burden on the processing and battery capacity available and progressively increasing the rate to obtain higher resolution data. The algorithm can also evaluate the observed physiological process for periodicity and can determine repetition of an irregular pattern, such as bigeminy, and use the determined pattern for predictive purposes to refine the programming of the device. The algorithm employs observation of a change in observed pattern as indicia for loss of proper detection.

Abstract: A method for operating an implantable medical device includes determining the difference of the absolute value of the voltage of a test QRS complex and the voltage of a baseline QRS template at a plurality of corresponding sample points and detecting ischemia if the sum of the differences at the plurality of sample points is greater than an ischemia detection threshold.

Abstract: Known methods of heart function analysis, while useful, suffer from a number of limitations. These include the fact that these methods are inherently static, in that they consider an individual electrocardiogram (ECG) that can only provide a picture of heart function at a particular moment in time. Furthermore, the assessment depends upon the expertise of specialists performing a visual analysis of ECG traces, which may be subjective, and of limited sensitivity. Accordingly, a method of processing ECG signals comprises the steps of extracting data from at least one ECG signal, determining a time derivative of the data and generating a normalised index value representative of the energy in the time derivative. The index value is compared with corresponding historical data of the patient.

Abstract: Cardiac electrical data are received from a patient, manipulated to determine various useful aspects of the ECG signal, and displayed and stored in a useful form using a computer. The computer monitor displays various useful information, and in particular graphically displays various permutations of reduced amplitude zones and kurtosis that increase the rapidity and accuracy of cardiac diagnoses. New criteria for reduced amplitude zones are defined that enhance the sensitivity and specificity for detecting cardiac abnormalities.

Abstract: A system comprising an implantable medical device includes a ventricular heart signal sensing circuit, a pacing therapy circuit, and a controller circuit coupled to the signal sensing circuit and the therapy circuit. The controller circuit is operable to detect a ventricular tachycardia heart rhythm from the cardiac signal, measure an amount of time the heart signal is one of inside or outside of an effective amplitude band, and initiate ATP therapy if the measured amount of time is less than a threshold amount of time.

Abstract: Template formation methods for use in implantable cardiac rhythm management devices. In an illustrative method, a signal is captured signal an implanted cardiac rhythm management device, and parameters for analysis of the captured signal are then defined. Then, in the example, additional signals can be captured and used to either verify or discard the captured signal defined parameters. The template formation methods provide for creating a robust template to compare with sensed cardiac complexes. Devices and systems configured to perform template formation and verification methods are also shown.

Abstract: Techniques are provided for tracking patient respiration based upon intracardiac electrogram (IEGM) signals or other electrical cardiac signals. Briefly, respiration patterns are detected based upon cycle-to-cycle changes in morphological features associated with individual electrical events with the IEGM signals. For example, slight changes in the peak amplitudes of QRS-complexes, P-waves or T-waves are tracked to identify cyclical variations representative of patient respiration. Alternatively, the integrals of the morphological features of the individual events may be calculated for use in tracking respiration. In any case, once respiration patterns have been identified, episodes of abnormal respiration, such as apnea, hyperpnea, nocturnal asthma, or the like, may be detected and therapy automatically delivered. In particular, techniques for detecting abnormal respiration based on various respiratory parameters derived from the IEGM—such as respiration depth and respiration power—are described.

Abstract: An implantable cardiac stimulation device includes a system that identifies and prevents the occurrence of impending atrial arrhythmias. A sensing circuit senses atrial activity of a patient's heart to provide an atrial activity signal. A processor compares the atrial activity signal to a predetermined standard indicative of an impending accelerated atrial arrhythmia to identify an impending accelerated atrial arrhythmia. A therapy circuit provides accelerated atrial arrhythmic preventive therapy to the patient when an impending accelerated atrial arrhythmia is identified. Data associated with the identification and therapy delivery is stored in a memory.

Abstract: A device and method for delivering electrical stimulation to the heart in a manner which provides a protective effect against subsequent ischemia is disclosed. The protective effect is produced by configuring a cardiac pacing device to intermittently switch from a normal operating mode to a stress augmentation mode in which the spatial pattern of depolarization is varied to thereby subject a particular region or regions of the ventricular myocardium to increased mechanical stress.

Abstract: A method for curvature based complex identification and classification comprises sensing a cardiac signal and computing curvatures at sample points on the sensed cardiac signal. Then to extract features from the computed curvatures, and compare the extracted features with a set of predetermined templates, and then to classify the sensed cardiac signal based on the outcome of the comparison.

Abstract: A technique is provided for detecting episodes of cardiac ischemia based on an examination of post-T-wave signal segments. Since cardiac ischemia is often a precursor to acute myocardial infarction (AMI) or ventricular fibrillation (VF), the technique thereby provides a method for predicting the possible onset of AMI or VF so that a warning may be delivered to the patient. The warning preferably includes both a perceptible electrical notification signal applied directly to subcutaneous tissue and a warning signal delivered via short range telemetry to a handheld warning device external to the patient. In one example, the onset of cardiac ischemia is identified by detecting a sharp falling edge within post-T-wave signals by filtering the signals using a high-pass filter having a cutoff frequency of at least 1 Hz. The total amount of energy in the filtered signal is calculated and compared against various thresholds.

Abstract: A cardiac rhythm management device is configured to detect oscillations in cardiac rhythm by comparing electrogram signals during successive heart beats. Upon detection of electrical alternans, the device may adjust its operating behavior to compensate for the deleterious effects of the condition.

Abstract: An implantable ischemia detecting devices generates a plurality of electrograms for analysis. A processor integrates the ST segment and T wave of each electrogram and normalizes the resulting integral by a normalizing factor to provide a ST segment score and T wave score, respectively. The ST segment and T wave scores are then utilized to compute a total ST segment and T wave score for analysis in detecting or monitoring ischemia of a patient's heart.

Abstract: The present invention provides methods and apparatus for generating a trigger from the R wave of an electrocardiogram (ECG) waveform using a threshold that adapts to the slope of the R wave while still within the leading edge of the R wave.

Abstract: A cardiac monitoring and/or stimulation method and systems provide monitoring, defibrillation and/or pacing therapies, including systems detecting and/or treating cardiac arrhythmia. A system includes a housing coupled to a plurality of electrodes configured for subcutaneous non-intrathoracic sensing. A signal processor receives a plurality of composite signals associated with a plurality of sources, separates a signal from the plurality of composite signals using blind source separation, and identifies a cardiac signal. The signal processor may iteratively separate signals from the plurality of composite signals until the cardiac signal is identified. A method of signal separation includes detecting a plurality of composite signals at a plurality of locations, separating a signal using blind source separation, and identifying a cardiac signal. The separation may include a principal component analysis and/or an independent component analysis.

Abstract: A technique is provided for detecting episodes of cardiac ischemia based on an examination of the total energy of T-waves. Since cardiac ischemia is often a precursor to acute myocardial infarction (AMI) or ventricular fibrillation (VF), the technique thereby provides a method for predicting the possible onset of AMI or VF. Briefly, the technique integrates internal electrical cardiac signals occurring during T-waves and then compares the result against a running average. If the result exceeds the average by some predetermined amount, ischemia is thereby detected and a warning signal is provided to the patient. The maximum slope of the T-wave is also exploited. Techniques are also set forth herein for reliably detecting T-waves, which help prevent P-waves from being misinterpreted as T-waves on unipolar sensing channels. The T-wave detection technique may be used in conjunction with ischemia detection or for other purposes.

Abstract: A technique is provided for detecting episodes of cardiac ischemia based on an examination of the total energy of T-waves. Since cardiac ischemia is often a precursor to acute myocardial infarction (AMI) or ventricular fibrillation (VF), the technique thereby provides a method for predicting the possible onset of AMI or VF. Briefly, the technique integrates internal electrical cardiac signals occurring during T-waves and then compares the result against a running average. If the result exceeds the average by some predetermined amount, ischemia is thereby detected and a warning signal is provided to the patient. The maximum slope of the T-wave is also exploited. Techniques are also set forth herein for reliably detecting T-waves, which help prevent P-waves from being misinterpreted as T-waves on unipolar sensing channels. The T-wave detection technique may be used in conjunction with ischemia detection or for other purposes.

Abstract: Identifying infants at risk for SIDS includes applying electrodes to an infant, receiving electrical signals from the electrodes, analyzing the received electrical signals to measure alternans of a heart of the infant, and identifying whether the infant is at risk for SIDS. A system for identifying infants at risk for SIDS includes an input unit configured to receive electrical signals from electrodes applied to an infant, a processor connected to the input unit and configured to process the received electrical signals to measure alternans of a heart of the infant, and a comparator configured to compare the measured alternans with alternans in a population of infants.

Abstract: A method of differentiating between ischemic and cardiac memory inverted T-waves includes performing an electrocardiogram of a patient; identifying inverted T-waves in at least some of precordial leads; identifying T-waves in leads I and aVL; diagnosing ischemia if leads I and aVL show inverted T-waves; and diagnosing cardiac memory if the leads I and aVL show non-inverted T-waves. The method may also include identifying T-waves in lead III; confirming ischemic diagnosis if the lead III shows deeper inverted T-waves than in the precordial leads; and confirming cardiac memory diagnosis otherwise.

Abstract: In an implantable heart stimulating device, system and method, a control circuit has first and second circuits for sensing and pacing. The first circuit can be connected to a first electrode member suited to be positioned in or at a first ventricle of the heart. The second circuit can be connected to a second electrode member suited to be positioned in or at a second ventricle of the heart. The control circuit is able to detect whether signals sensed by the second circuit are likely to be far field signals. The control circuit performs this detection by at least determining whether, during a predetermined time (length, more signals are sensed by the second circuit than by the first circuit.

Abstract: A template selection method involves providing a plurality of templates representing a type of cardiac event. One or more characteristics of each template are evaluated. The evaluations are compared and a template is selected as a current template based on the comparison.

Abstract: An implantable device detects and discriminates between ischemia and myocardial infarction. The device includes a plurality of electrodes that provide a plurality of cardiac activity sensing electrode configurations. A sensing circuit provides a plurality of electrograms in response to cardiac activity sensed by the electrode configurations. A discriminator detects and discriminates between ischemia and myocardial infarction responsive to ST segments of the electrograms. The device may further discriminate an equivocal condition and initiate a secondary analysis for diagnosing spasm, anxiety, or exercised induced ischemia.

Abstract: Methods and apparatus for determining T-wave alternan signatures (i.e., morphology and polarity) derived from a physiologic signal representative of a subject's heart activity; assessing changes in the myocardium Action Potential (“AP”) through analysis of the alternan signature derived from a physiologic signal representative of a subject's heart activity; and/or assessing spatial disassociation of alternan characteristics that are likely associated with the initiation of re-entrant arrhythmias.

Abstract: A method of assessing the cardiac arrhythmia risk in a subject to provide a measure of cardiac or cardiovascular health in that subject is described herein. In one embodiment, the method comprises the steps of: (a) collecting at least one QT and RR interval data set from the subject; (b) separating fluctuations from slow trends in said at least one QT and RR interval data set; (c) comparing said QT and RR fluctuations to one another and (d) generating from the comparison of step (c) partial measures of risk of cardiac arrhythmia in said subject. A greater difference between QT and RR fluctuations indicates greater risk of cardiac arrhythmia in said subject. The data sets are collected in such a manner that they reflect almost exclusively the conduction in the heart muscle and minimize the effect on the data sets of rapid transients due to autonomic nervous system and hormonal control.

Abstract: The supraventricular rhythm of a patient's heart is characterized using cardiac beats collected during a plurality of time periods, some of which are noncontiguous. Pacing parameters may be modified to allow the development of a spontaneous rhythm. Waveforms of the collected cardiac beats are stored for later processing, or are combined with previously collected beats and the combination is stored. When a sufficient number of cardiac beats are collected, the patient's supraventricular rhythm is characterized using the collected cardiac beats.

Abstract: A method in a computer system for detecting myocardial infarction including the steps of (a) receiving ECG data, (b) analyzing that data for the presence of benign ST data, and (c), when the ST data is not benign, (1) establishing a pathological threshold, (2) normalizing any deviation in the ECG data, (3) applying a pattern analysis to the normalized ECG data, and (4) generating a score indicating the presence of a myocardial infarction based on the pattern analysis and the threshold.

Abstract: Method and apparatus for determining alternans data of an ECG signal. The method can include determining at least one value representing at least one morphology feature of each beat of the ECG signal and generating a set of data points based on a total quantity of values and a total quantity of beats. The data points can each include a first value determined using a first mathematical function and a second value determined using a second mathematical function. The method can also include several preprocessing algorithms to improve the signal to noise ratio. The method can also include separating the data points into a first group of points and a second group of points and generating a feature map by plotting the first group of points and the second group of points in order to assess an alternans pattern of variation. The feature map can be analyzed by statistical tests to determine the significance difference between groups and clusters.

Abstract: An implantable cardiac device and method provides for monitoring a progression or regression in heart disease during an extended time period. A sensor generates an electrogram signal representing electrical activity of a patient's heart. From the generated electrogram signal, a processor determines morphology measurements wherein the morphology measurements indicate a progression or regression in the heart disease. The morphology measurements are stored in a memory during the extended period of time. A telemetry circuit transmits the stored morphology measurements to an external receiver for retrieval or display. The morphology measurements may be of electrogram intrinsic activity or evoked response activity characteristics.

Abstract: A system and method for use in an implantable cardiac device that delivers electrical therapy to a patient's heart determines if a T wave alternan pattern of the patient's heart exists. The system includes a sensing circuit that generates an electrical signal representing electrical activity of the patient's heart. A morphology detector measures a magnitude of a T wave characteristic of each T wave in the electrical signal of a predetermined number of cardiac cycles of the heart. A discriminator then determines, responsive to the measured T wave characteristic magnitudes, if a T wave alternan pattern exists. A T wave alternan pattern may be determined to exist if the number of measured T wave characteristic magnitudes greater than and less than a T wave characteristic magnitude baseline are substantially equal and each greater than a given number.

Abstract: A programmable signal analysis device for detecting and counting neurological and muscular events in living tissue that incorporates one or more signal threshold levels to identify an event, a counter to count events, and a timer to determine event frequency as events per unit time. The threshold levels and counter/timer operating modes/parameters are digitally programmable to identify and count events, i.e., electrical signals having defined parameters. Such a circuit is of particular use in a microstimulator/sensor which is capable of being injected into living tissue at the site of interest. The microstimulator/sensor is used to stimulate a neural pathway or muscle and/or to block a neural pathway to alleviate pain or block stimulation of a muscle.

Abstract: Algorithms for detecting, sizing and locating old myocardial infarcts by evaluating particular ECG lead data derived from selected ECG leads, where that particular data is presented hierarchically for review and confirmation, and includes selected voltage-amplitude ratios of R/Q and R/S. For a given human subject, the specific hierarchical pattern of lead data to be examined is selected on the basis of predetermined personal and demographic data, and completely in light of various, well-known, so-called confounders and excluders.

Abstract: A method for monitoring the progression of the hemodynamic status of a patient by tracking autonomic tone. For example, the method may be applied to patients suffering from heart failure, diabetic neuropathy, cardiac ischemia, sleep apnea and hypertension. An implantable or other ambulatory monitor senses a pulse amplitude signal such as a vascular plethysmography signal. Variations of the signal amplitude on a scale greater than the heartbeat to heartbeat scale are indicative of variations in autonomic tone. A significant reduction in pulse amplitude and pulse amplitude variability are indicative of a heart failure exacerbation or other disease state change. This information may be used to warn the patient or healthcare providers of changes in the patient's condition warranting attention.