Abstract: An automated system and method for diagnosing and monitoring the outcomes of atrial fibrillation is described. A plurality of monitoring sets is retrieved from a database. Each of the monitoring sets include recorded measures relating to patient information recorded on a substantially continuous basis. A patient status change is determined in response to an atrial fibrillation diagnosis by comparing at least one recorded measure from each of the monitoring sets to at least one other recorded measure. Both recorded measures relate to the same type of patient information. Each patient status change is tested against an indicator threshold corresponding to the same type of patient information as the recorded measures which were compared. The indicator threshold corresponds to a quantifiable physiological measure of a pathophysiology resulting from atrial fibrillation.

Abstract: In a device and a method for determining a cardiac condition from a detected cardiac signal, an input signal is formed from the detected cardiac signal and supplied to an analysis unit. The analysis unit forms an analysis signal from the input signal, having a real part substantially corresponding to the input signal and an imaginary part that is a predetermined transformation of the input signal. A calculation unit operates on the analysis signal to calculated at least two heart-related parameters therefrom. The heart-related parameters are supplied to a processing unit that combines the heart-related parameters in a predetermined manner for identifying a cardiac condition.

Abstract: This document discusses, among other things, a method of identifying a non-fatal tachyarrhythmia episode by determining a degree of similarity between the episode and a template generated from a previous tachyarrhythmia episode.

Abstract: In a heart stimulation device a mode of operation is switched in response to detection of atrial tachyarrhythmia such as atrial fibrillation. The stimulation device may initially operate in a normal mode of pacing then, upon detection of atrial tachyarrhythmia, the stimulation device may change how it senses signals and it may switch to another mode of pacing at one or more sites in the ventricle.

Abstract: A method of determining a state of ventricular fibrillation from a waveform, includes: performing calculations on the Fourier transform of the waveform voltage values by using the quotient of the power in a high frequency band and of the power in a low frequency band; and determining the state of ventricular fibrillation by relating this ratio to the state of ventricular fibrillation. A defibrillation system for use in treatment of ventricular fibrillation includes at least one sensor to measure heart rhythm and at least one applicator to apply a defibrillation shock to a patient. The system further includes at least one processor which is adapted to calculate the ratio and also to obtain user input regarding survival of subgroups and average response times in the user's domain which allows calculation of an estimated maximum overall survival and selection of an optimum threshold for the ratio measure based on this maximum.

Abstract: A method and apparatus for determining oversensing in an implantable medical device that includes sensing a first cardiac signal and detecting cardiac events via a first electrode configuration, determining the presence of an episode requiring therapy in response to the detected cardiac events, sensing the first cardiac signal via a second electrode configuration, determining a baseline measurement of samples of the first cardiac signal sensed via the second electrode configuration, and determining whether to deliver therapy in response to the baseline measurement.

Abstract: An implantable subcutaneous cardiac device includes at least two subcutaneous electrodes adapted for placement external to a heart beneath the skin of a patient. The device further includes an arrhythmia detector that detects a sustained tachyarrhythmia of the heart and a pulse generator that delivers anti-tachycardia pacing pulses to the subcutaneous electrodes in response to detection of a sustained tachyarrhythmia. The pacing pulses preferably have waveforms devoid of any exponential voltage decay and include rounded or substantially constant portions to minimize pain.

Abstract: An implantable medical device and associated method for automatically generating morphology templates during fast cardiac rhythms, confirming a provisional template as a confirmed template, and using the confirmed template to classify subsequent detected arrhythmias. A provisional SVT template may be created during a fast ventricular rate and activated as a confirmed SVT template upon verification that the fast rate was due to an SVT. The confirmed SVT template may be used to discriminate SVT from VT/VF.

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 system and method for detecting and classifying cardiac arrhythmias based on cardiac pressure signals or the combination of cardiac electrical and cardiac pressure signals. A cardiac electrogram signal is sensed to derive a cardiac rate from which an arrhythmia detection is made when the cardiac rate meets arrhythmia detection criteria. An intracardiac pressure signal is sensed to derive an indicator of tachycardia based on an analysis of the pressure signal in either the time domain or frequency domain. The detected arrhythmia is classified as tachycardia or fibrillation based on the tachycardia indicator wherein the tachycardia indicator is compared to tachycardia detection criteria and the arrhythmia is classified as tachycardia if tachycardia detection criteria are met and the arrhythmia is classified as fibrillation if the tachycardia detection criteria are not met.

Abstract: Cardiac treatment methods and devices providing templates representative of past tachyarrythmia events, each template associated with a therapy. A cardiac waveform is detected, and if it corresponds to a particular template associated with a previous therapy that was satisfactory in terminating a past event, the previous therapy is delivered again. If unsatisfactory, the previous therapy is eliminated as an option. If, for example, the previous therapy was an antitachycardia pacing therapy unsatisfactory in terminating the past tachyarrythmia event, delivery of the antitachycardia pacing therapy is eliminated as an option. Instead of ATP therapy, one or more of a cardioversion, defibrillation, or alternate anti-tachycardia pacing therapy may be associated with the particular template.

Abstract: Techniques for enabling both preventive overdrive pacing and antitachycardia pacing (ATP) within an implantable device are provided. The device gains the benefits of overdrive pacing for preventing the onset of a tachycardia and, if one nevertheless occurs, ATP is employed to terminate the tachycardia. In particular, a technique is provided for promptly detecting the onset of atrial tachycardia during preventive overdrive pacing based on loss of capture of atrial pacing pulses. A technique is also provided for using detection of loss of capture of atrial or ventricular pacing pulses to trigger automatic switching from overdrive pacing to ATP. A setup technique determines whether to enable the automatic switching from overdrive pacing to ATP within a particular patient. Also, techniques are provided for verifying loss of capture of atrial or ventricular backup pacing pulses and for detecting low amplitude ventricular fibrillation based on loss of capture of ventricular backup pacing pulses.

Abstract: A system and method for presenting information relating to heart data can involve operations including identifying arrhythmia events in physiological data obtained for a living being, receiving human assessments of at least a portion of the arrhythmia events, determining a measure of correlation between the human assessments and the identified events, and selectively presenting information regarding the identified events based on the measure of correlation. The operations can also include identifying atrial fibrillation events in physiological data obtained for a living being, obtaining heart rate data for the living being, and presenting information regarding the heart rate data and duration of the atrial fibrillation events together with a common time scale to pictographically represent heart rate trend with atrial fibrillation burden during a defined time period.

Abstract: A CRM system enhances intracardiac electrogram-based arrhythmia detection using a wireless electrocardiogram (ECG), which is a signal sensed with implantable electrodes and approximating a surface ECG. In one embodiment, an intracardiac electrogram allows for detection of an arrhythmia, and the wireless ECG allows for classification of the detected arrhythmia by locating its origin. In another embodiment, the wireless ECG is sensed as a substitute signal for the intracardiac electrogram when the sensing of the intracardiac electrogram becomes unreliable. In another embodiment, a cardiac signal needed for a particular purpose is selected from one or more intracardiac electrograms and one or more wireless ECGs based on a desirable signal quality. In another embodiment, intracardiac electrogram-based arrhythmia detection and wireless ECG-based arrhythmia detection confirm with each other before indicating a detection of arrhythmia of a certain type.

Abstract: An implantable cardioverter/defibrillator includes a tachycardia detection system that detects one-to-one (1:1) tachycardia, which is a tachycardia with a one-to-one relationship between atrial and ventricular contractions. When the 1:1 tachycardia is detected, the system discriminates ventricular tachycardia (VT) from supraventricular tachycardia (SVT) based on analysis of a cardiac time interval. Examples of the cardiac time interval include an atrioventricular interval (AVI) and a ventriculoatrial interval (VAI). A template time interval is created during a known normal sinus rhythm. The system measures a tachycardia time interval after detecting the 1:1 tachycardia, and indicates a VT detection if the tachycardia time interval differs from the template time interval by at least a predetermined percentage of the template time interval.

Abstract: Systems and techniques for monitoring cardiac activity. In one aspect, a method includes collecting information describing the variability in heart rate over a series of beats, designating variability at a lower end of physiological values as being largely irrelevant to atrial fibrillation, designating variability in a midrange of physiological values as being indicative of atrial fibrillation, designating variability in an upper range of physiological values as being negatively indicative of atrial fibrillation, and determining a relevance of the variability described in the collection to atrial fibrillation.

Abstract: The present invention provides a method and system for characterizing one beat of a patient's supraventricular rhythm. A plurality of templates is provided and updated using a plurality of qualified beats. Updating occurs by temporally aligning the shock channel waveforms of the template beats using rate channel fiducial points. The template beats are combined by point-by-point addition of the shock channel waveforms. The resultant updated template characterizes one of the patient's supraventricular conducted cardiac beats.

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 arrangement 10 for predicting tachyarrhythmia of a heart has a detection means 12 and an evaluation unit 18. The detection means 12 picks up electrical signals from the heart. The evaluation unit 18, which is connected to the detection means, determines a rate value that depends upon the respective heart rate. The evaluation unit also evaluate a plurality of correspondingly determined rates values, to determine a heart rate variability value that depends on the variability of the detected rate values, wherein the evaluation unit 18 responds to a rise in the heart rate variability value.

Abstract: Various embodiments are directed to providing systems and methods that can reduce the likelihood of arrhythmia onset by effecting a treatment, responsive to a detected premature event, that mimics or otherwise attempts to emulate a healthy heart's natural recovery process. In one particular embodiment, the premature event comprises a premature ventricular contraction or “PVC”, and the treatment comprises pacing the patient to mimic or otherwise emulate a turbulence pattern that is typically exhibited by a healthy heart when the heart attempts to recover from the PVC.

Abstract: A cardiac rhythm management system measures a time interval between a first fiducial marker indicative of a ventricular depolarization (e.g., a Q-wave, an R-wave, etc.) and a second fiducial marker indicative of a subsequent mitral valve closure (MVC) occurring during the same cardiac cycle. Such time intervals are used for detecting atrioventricular (AV) dissociation. The AV dissociation may, in turn, be used for discriminating between a supraventricular tachyarrhythmia (SVT) and a ventricular tachyarrhythmia (VT) or for any other diagnostic or therapeutic purpose. The AV dissociation and/or SVT/VT discrimination information may be communicated from an implantable cardiac rhythm management device to an external interface and/or used to determine the nature of therapy delivered to the subject. In a further example, amplitudes indicative of the MVCs are also used for determining whether AV dissociation exists.

Abstract: A cardiac rhythm management system including a highly sensitive technique for discriminating AF from AFL. An electrode disposed in or about a heart senses a cardiac signal. A controller through a sensing circuit receives the sensed cardiac signal from the electrode and processes the sensed cardiac signal to compute an average cycle length-to-cycle length variation based on serial interval relationships from the sensed cardiac signal, and then comparing the computed average cycle length-to-cycle length variation to one or more pre-determined threshold values to discriminate AF from AFL. As a result of substantial difference in cycle length-to-cycle length variation between AF and AFL (despite similar average cycle lengths), the sequence-based measure of cycle length-to-cycle length variability proves to be a highly specific and reliable discriminator of AF from AFL.

Abstract: An algorithm for detection of tachycardias and for discriminating between supraventricular tachycardia (SVT) and ventricular tachycardia (VT) when a 1:1 tachycardia condition is present that can be implemented in an implantable cardiac rhythm management device. Variability measures of AV and VA intervals during the tachycardia are computed and used to distinguish between SVT and VT.

Abstract: A method implemented in a dual chamber cardiac rhythm management device for identifying non-sinus ventricular depolarizations following an atrial event. The PR interval for a sensed ventricular beat that occurs after either an atrial pace or an atrial sensed event is examined and if it falls into a non-physiologic range, it is classified as an ectopic beat. If the PR interval is close to a physiologic range, the RR to AA ratio and a PR interval for the current beat are compared to those for an immediately preceding beat. Attention is also paid to the morphology of the ventricular depolarization in determining whether a beat is ectopic or not.

Abstract: A method and apparatus delivering therapy in an implantable medical device that includes sensing a first cardiac signal and detecting cardiac events via a first electrode configuration, determining the presence of an episode requiring therapy in response to the detected cardiac events, sensing a second cardiac signal via a second electrode configuration, comparing, in response to an episode being present, portions of the second cardiac signal corresponding to the detected cardiac events with a predetermined template, and determining whether to deliver therapy in response to the comparing.

Abstract: A method and system for classifying tachyarrhythmia episodes as associated or disassociated. Primary and auxiliary depolarizations are detected from different cardiac regions during a tachycardia episode. A first time interval is positioned to surround each of one or more primary depolarizations, including auxiliary depolarizations that occur in the first time interval. The auxiliary depolarizations occurring in the first time interval are then counted. Based on the number and the location of the auxiliary depolarizations counted in the first time intervals, the one or more primary depolarizations and the auxiliary depolarizations of the tachycardia episode are classified as disassociated or associated.

Abstract: An apparatus for discriminating between cardiac events that includes an input circuit receiving signals indicative of the cardiac events, a first output circuit generating pulses in response to the received signals, and a microprocessor determining whether a signal received by the input circuit subsequent to the generated pacing pulses corresponds to a predetermined cardiac event in response to an elapsed time period between the generated pulses and the subsequently received signal and a predetermined discrimination threshold.

Abstract: In one embodiment, a method includes sensing depolarizations of a heart at a plurality of different locations, and determining a sequence of the sensed depolarizations. The method may further include identifying a tachycardia condition and stimulating the heart at the plurality of locations based on the determined sequence. For example, the method may be implemented by an implantable medical device in order to improve anti-tachycardia pacing (ATP).

Abstract: A method and apparatus for assessing the risk of atrial fibrillation in a patient by calculating the relative frequency of short and long intervals between successive heart beats during sinus rhythm is presented. An imbalance of short over long sinus intervals has been found to indicate a higher risk of atrial fibrillation. An implantable cardiac device may be configured to automatically deliver interventional therapy to restore sinus interval balance when such an imbalance is detected.

Abstract: An implantable cardiac stimulation device, such as a pacemaker or Implantable Cardioverter Defibrillator, is configured to automatically monitor the effects of antiarrhythmic drugs on cardiac electrical signals within a patient to verify the efficacy of the drugs taken. In one example, an analysis of patient cardiac electrical signals is performed by comparing the cardiac electrical signals with values representative of the effects of different classes of antiarrhythmic drugs. If the implantable device determines that the prescribed antiarrhythmic drugs have not been effective, a warning signal is generated. The warning signal is conveyed directly to the patient via a bedside monitor and to the patient's physician via remote connection to an external programmer device so that both are notified of the drug efficacy problems.

Abstract: Various exemplary methods include altering conduction and/or operation of the AV node and/or AV bundle to help classify arrhythmias.

Abstract: Analyzes surface electrocardiographic and intracardiac signals to identify and separate electrical activity corresponding to distinct but superimposed events in the heart. Assesses the spatial phase, temporal phase, rate, spectrum and reproducibility of each event to determine uniformity of activation in all spatial dimensions. Uses numerical indices derived from these analyses to diagnose arrhythmias. Uses these indices to determine the location of an arrhythmia circuit, and to direct the movement of an electrode catheter to this location for ablation or permanent catheter positioning. Subsequently, uses these indices to determine whether ablation has successfully eliminated the circuit. Uses variability in these indices from the surface electrocardiogram to indicate subtle beat-to-beat fluctuations which reflect the tendency towards atrial and ventricular arrhythmias.

Abstract: A method and computer program product comprising an algorithm adapted to execute a method of identifying the spatial coordinates of a sustaining source of fibrillatory activity in a heart by computing a set of point-dependent dominant frequencies and a set of point-dependent regularity indices for a set of products of point-dependent unipolar discrete power spectra and point-dependent bipolar discrete power spectra, derived by spectral analyses of corresponding unipolar and bipolar cardiac depolarization signals simultaneously acquired from a set of points of the heart. A maximum dominant frequency is selected whose associated coordinates identify the point of the sustaining source of fibrillatory activity. The magnitude of the regularity index is interpreted to verify the identification of the spatial coordinates of the sustaining source of fibrillatory activity. When indicated, surgical intervention is directed to the spatial coordinates of the sustaining source of fibrillatory activity.

Abstract: A system and method for selectively treating a ventricular tachycardia based on sensed atrial and ventricular intervals from the patient's heart. A detection window of the ten most recent atrial and ventricular intervals are analyzed for the occurrence of either tachycardia or fibrillation. When a majority of the sensed intervals are satisfied, the apparatus starts a duration time interval. Ventricular intervals and atrial intervals are compare, ventricular interval greater than the atrial interval by a bias factor the system delivers tachycardia therapy to the heart. Alternatively, the method withholds tachycardia therapy to the heart when the atrial rate is classified as atrial fibrillation and the ventricular response is unstable.

Abstract: Systems and methods employing a weighted zero crossing sum metric (WZCSM) derived from the EGM that improves the specificity of discriminating between a monomorphic tachyarrhythmia and a polymorphic tachyarrhythmia are provided that examine frequency content and baseline information of the EGM as discriminatory signatures are disclosed. In preferred embodiments, high rate polymorphic QRS complexes are discriminated from high rate monomorphic QRS complexes to increase the specificity of detection of polymorphic VT and VF. Zero crossing points (ZCPs) and weighted ZCP slopes of the high pass filtered EGM signal in baseline and sense event windows are identified. The weighted ZCPs of the baseline window are summed to provide a baseline WZCSB, and the weighted ZCPs of the VSENSE event window are summed to provide a VSENSE event WZCSE. A WZCSM is derived from the VSENSE event WZCSE and the baseline WZCSB that is compared to a threshold.

Abstract: Determining termination of an identified tachyarrhythmia episode may involve analysis of a relative decrease in tachyarrhythmia rate, a normalization of electrogram morphology criteria, or both. An implanted medical device may obtain a tachyarrhythmia rate and a morphology of a cardiac waveform. The device may compare the tachyarrhythmia rate to a threshold tachyarrhythmia rate and the morphology to a template morphology, and classify the heart beat as indicating termination of the tachyarrhythmia episode when the tachyarrhythmia rate is less than the threshold tachyarrhythmia rate, the morphology categorizes as normal, or both. For arrhythmias with no therapy delivered, observation of arrhythmia behavior at the point of termination may lead to improved classification. In addition, observation of a relative decrease in tachyarrhythmia rate immediately after therapy application can lead to application of slower but more specific criteria for redetection.

Abstract: Techniques are provided for distinguishing Cheyne-Stokes Respiration (CSR) caused by central sleep apnea (CSA) from CSR caused by congestive heart failure (CHF) and for evaluating the severity of CHF, if present, based up CSR. A time period associated with the CSR is determined based upon separate evaluation of apnea and hyperpnea periods during CSR and then the time period is compared against a time-varying discrimination threshold derived from integrated thoracic impedance signals. If the time period exceeds the threshold, the CSR of the patient is caused by CHF; otherwise, the CSR is caused by CSA. Thereafter, the course of therapy delivered to the patient is controlled based upon the type of CSR. In addition, if the CSR is caused by CHF, the time period associated with CSR is employed to determine the severity of CHF—with longer time periods being associated with more severe CHF.

Abstract: A method of generating a template in an implantable medical device for implantation within a patient, and a processor readable medium for performing the method, that includes generating a template from collected events corresponding to the patient, delaying the generation of the template for a first predetermined time period in response to the template not being generated within a predetermined number of collected events, determining whether the template is valid, and monitoring the template to determine whether the template is an accurate representation of the patient.

Abstract: A system and method for discriminating cardiac rhythms occurring in an antegrade direction from cardiac rhythms occurring in a retrograde direction. Atrial and ventricular contractions are sensed, from which atrial and ventricular cycle lengths are determined. Ventricular contractions are also analyzed to determine the occurrence of a tachycardia episode that has a one-to-one association of atrial contractions to ventricular contractions. During a tachycardia episode having a one-to-one association of atrial contractions to ventricular contractions, the atrial cycle lengths are paired with the ventricular cycle lengths, where for each of the atrial cycle lengths the atrial cycle length is paired with at least one ventricular cycle length started before the first atrial contraction of each of the atrial cycle lengths and paired with at least one ventricular cycle length started after the first atrial contraction of each of the atrial cycle lengths.

Abstract: Detection of arrhythmias is facilitated using irregularity of ventricular beats measured by delta-RR (?RR) intervals that exhibit discriminatory signatures when plotted in a Lorenz scatter-plot. An “AF signature metric” is established characteristic of episodes of AF that exhibit highly scattered (sparse) distributions or formations of 2-D data points. An “AFL signature metric” is established characteristic of episodes of AFL that exhibit a highly concentrated (clustered) distribution or formation of 2-D data points. A set of heart beat interval data is quantified to generate highly scattered (sparse) formations as a first discrimination metric and highly concentrated (clustered) distributions or formations as a second discrimination metric. The first discrimination metric is compared to the AF signature metric, and/or the second discrimination metric is compared to the AFL signature metric. AF or HFL is declared if the first discrimination metric satisfies either one of the AF signature metric.

Abstract: A method and apparatus are provided for improving the detection of certain cardiac rhythms by combining dual chamber interval-related detection methods with electrogram morphology analysis. A prioritized set of rules are defined wherein each rule is directed at identifying a particular arrhythmia or type of arrhythmia. Each rule includes clauses that may be related to sensed event intervals and interval patterns and at least one rule includes at least one clause relating to the EGM morphology.

Abstract: Multiple morphology templates for discliminating between rhythms have been used, such as supraventricular tachyarrhythmias (SVTs) and ventricular tachyarrhythmias (VTs), for delivering a countershock in response to a VT episode, but withholding delivery of such a countershock in response to an SVT episode. In certain examples, the particular morphology used for storing morphological features is selected at least in part using a sensor-indicated activity level of a subject, or a metabolic need of the subject.

Abstract: Various techniques are described for preventing pacemaker mediated tachycardia (PMT) within biventricular pacing systems and for detecting and terminating PMT should it nevertheless arise. In a first prevention technique, refractory periods applied to the atrial channel are synchronized to begin with a second of a pair of ventricular pacing pulses to more effectively prevent T-wave oversensing on the atrial channel. In a second prevention technique, the sensitivity of the atrial channel is reduced during T-waves also to prevent T-wave oversensing. In a third prevention technique, template matching is performed on the ventricular channels to prevent T-wave oversensing. In a fourth prevention technique, T-wave detection windows are applied to both the ventricular and atrial channels subsequent to any paced or sensed events. In a first detection technique, PMT is detected based upon a degree of variation within V-pulse to P-wave pacing intervals.

Abstract: A method and apparatus to determine possible atrial fibrillation that includes detecting irregular pulse rhythms from a succession of time intervals each corresponding to a respective interval of time between successive pulse beats of a sequence of the pulse beats; analyzing the detected irregular pulse rhythms to make a determination of possible atrial fibrillation; indicating the possible atrial fibrillation from the determination. If a sphygmomanometer is used, a plurality of pulse beats may be detected with it including the sequence of pulse beats; and respiratory variation in systolic pressure of the pulse beats may be compensated by designating the succession of time intervals to exclude at least an initial one of the plurality of time intervals.

Abstract: A method, system, and article of manufacture for responding to medical alerts, one embodiment of which comprises receiving a medical alert having an associated alert location, detecting a current location for each of a plurality of medical staff members, and selecting a medical staff member to respond to the medical alert based at least in part on the distance between the alert location and the current location. Some embodiments may further comprise receiving a plurality of medical alerts, determining if any of the medical alerts indicates an emergency situation, generating a prioritized task from non-emergency alerts, and selecting a highest priority medical alert from the prioritized list.

Abstract: The present invention provides a system and a method for discriminating supraventricular tachyarrhythmias from ventricular arrhythmias during a tachycardia episode. First cardiac signals and second cardiac signals are sampled for cardiac complexes. A first feature on the first cardiac signal and a second feature on the second cardiac signal are utilized to determine an average time difference for a plurality of normal sinus rhythm complexes. A time difference between the first feature and the second feature is then determined for each cardiac complex of a tachycardiac rhythm. The cardiac complex is characterized as a ventricular tachycardia complex if the time difference exceeds the average time difference by a predetermined amount. Otherwise, it is classified as VT if its morphology after alignment is different from that during normal sinus rhythm.

Abstract: A circuit and method for detecting cardiac rhythm abnormalities employ unipolar signals respectively obtained from a cardiac lead having a tip at which a number of separate electrodes are disposed, the electrodes being simultaneously in contact with cardiac tissue. The respective unipolar signals which are obtained from the multiple electrodes exhibit a time relationship relative to each other, and this time relationship is analyzed to determine whether a cardiac rhythm abnormality is present or one or more of the unipolar signals is compared to a template which is known to represent a cardiac abnormality. Analysis of the time relation is undertaken by determining the absolute value of a time offset between any two of the unipolar signals, or by correlating any two of the unipolar signals.

Abstract: Devices and methods for testing a pulmonary vein to determine whether or not ablation would be effective in terminating atrial fibrillation. The devices and methods include a catheter having an expandable balloon attached to the distal end of the catheter. The balloon has pores on the distal end of the balloon for administering a fluid into the target pulmonary vein. The fluid inhibits the electrical impulses generated by the target pulmonary vein. Once the electrical impulses of the target pulmonary vein have been inhibited it can be determined whether or not the atrial fibrillation continues to occur. If the atrial fibrillation has been eliminated, then ablation or other therapy is appropriate. Thus, the devices and methods limit unnecessary treatment of a pulmonary vein.

Abstract: A method and apparatus for method for discriminating heart rhythms includes computing a first predetermined number of RR intervals from received QRS intervals, and computing a median RR interval corresponding to a predetermined number of the first predetermined number of RR intervals. A predetermined beat-to-beat variation and a corresponding predetermined count are determined based on the computed median RR interval. Beat-to-beat variation differences between the first predetermined number of RR intervals are computed and a determination is made as to whether the computed beat-to-beat variation differences are greater than the predetermined beat-to-beat variation, and as to whether a number of the computed beat-to-beat variation differences that are greater than the predetermined beat-to-beat variation is greater than the predetermined count. The heart rhythm is identified as an irregular rhythm in response to the number being greater than or equal to the predetermined count.

Abstract: An implantable medical device and method are provided for assessing autonomic tone and risk factors associated with arrhythmias and, based on this assessment, an early recurrence of ventricular tachycardia or ventricular fibrillation is predicted. Specifically, changes in R—R interval, heart rate variability, patient activity, and myocardial ischemia are measured prior to and after a detected an arrhythmia episode. A recurrence score is calculated as a weighted sum of measured parameters and compared to a prediction criterion. The prediction criterion may be a preset threshold score or an individualized episode template based on previously calculated recurrence scores associated with recurring episodes. Stored parameters and episode-related data may be downloaded for offline analyses for optimizing prediction criteria and monitoring patient status.