Abstract: A nondefibrillating and nonfibrillation-inducing energy is delivered at a first internal thoracic location. A first resulting electrical signal is detected at a second internal thoracic location in or near a target region of a heart. A first defibrillation threshold is estimated using the nondefibrillating and nonfibrillation-inducing energy, the first resulting electrical signal, and a target electric field strength. The defibrillation threshold represents an energy that when delivered at the first internal thoracic location creates an electric field strength in the target region of the heart that meets or exceeds the target electric field strength.

Abstract: A system detects events related to cardiac activity. The system comprises a primary cardiac signal sensing circuit, at least one secondary cardiac signal sensing circuit having a higher sensitivity than the primary sensing circuit, and a controller circuit coupled to the primary and secondary cardiac signal sensing circuits. The controller circuit determines a rate of depolarization using the primary sensing circuit and detects tachyarrhythmia using the rate. The controller circuit also detects tachyarrhythmia using the secondary sensing circuit and also deems the tachyarrhythmia valid if the controller circuit detects the tachyarrhythmia using both the primary and secondary sensing circuit.

Abstract: Methods and systems for detecting capture using pacing artifact cancellation are described. One or more pacing artifact templates are provided and a cardiac signal is sensed in a cardiac verification window. Each of the pacing artifact templates may characterize the pacing artifact associated with a particular pacing energy level, for example. A particular pacing artifact template is canceled from the cardiac signal. Capture is determined using the pacing artifact canceled cardiac signal. Detection of fusion/pseudofusion beats may be accomplished by comparing a cardiac signal to a captured response template.

Abstract: Methods and systems are described that involve synchronized ventricular pacing that promotes sensing of atrial events. The atrioventricular pacing delay is modified based on characteristics of previously sensed atrial events. The modified AV delay is implemented relative to a first atrial event. A second AV delay is implemented relative to a second atrial event if the second atrial event is sensed during the modified AV delay. A ventricular pacing pulse is delivered following the second AV delay.

Abstract: Methods and systems are directed to detecting atrial tachyarrhythmia. A plurality of A-A intervals is detected. The detected A-A intervals are selected and used to detect atrial tachyarrhythmia. Selecting A-A intervals may be based on determining that A-A intervals are qualified. Qualified A-A intervals may be determined if a duration of the particular A-A interval falls outside a predetermined duration range, for example. Qualified A-A intervals may also be determined based on events occurring between consecutively sensed atrial events of the particular A-A interval, and whether the duration of the particular A-A interval falls within the predetermined duration range, for example.

Abstract: Systems and methods are described for classifying a cardiac rhythm. A cardiac rhythm is classified using a classification process that includes a plurality of cardiac rhythm discriminators. Each rhythm discriminator provides an independent classification of the cardiac rhythm. The classification process is modified if the modification is likely to produce enhanced classification results. The rhythm is reclassified using the modified classification process.

Abstract: An implantable cardioverter/defibrillator (ICD) executes a rate accuracy enhancement algorithm to select measured atrial and ventricular intervals for classifying a detected tachycardia based on average atrial and ventricular rates calculated from the selected atrial and ventricular intervals. The detected tachycardia is classified as ventricular tachycardia (VT) if the average ventricular rate is substantially higher than the average atrial rate.

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: This document describes systems, devices, and methods that use multiple morphology templates for discriminating between rhythms, 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: Different types of cardiac arrhythmia are classified based on the morphology of the arrhythmic beats. Cardiac beats associated with an arrhythmic episode are compared to a plurality of representative beat morphologies, each representative beat morphology characterizing a type of arrhythmia of the heart. An arrhythmic episode may be classified as a particular type of arrhythmia if the morphology of the arrhythmic cardiac beats matches a representative beat morphology characterizing the particular type of arrhythmia. An appropriate therapy for the particular type of arrhythmia may be selected based on the arrhythmia classification. A particular type of arrhythmia may be associated with one or more therapies used to treat the arrhythmia. The therapy used to treat the arrhythmia may comprise a therapy identified as a previously successful therapy.

Abstract: This document discusses, among other things, a combination pacer/defibrillator that is tailored for bradycardia patients. In one example, its shock-delivery specificity exceeds its sensitivity to shockable ventricular tachyarrhythmias. In another example, its specificity exceeds 95%, or 99%, or even 99.5%. Sensitivity is programmed to a high desired sensitivity value, but only if it can be done without decreasing the specificity below the desired specificity threshold value. This can be conceptualized as “avoiding at all costs” delivering false shocks, even at the expense of failing to deliver a shock to a treatable ventricular tachyarrhythmia. Specificity enhancements include, among other things, inhibiting shock delivery when the patient is breathing or not supine, using multiple channels or a high rate VT/VF detection threshold.

Abstract: A method and system for generating a characterization of one beat of a patient's supraventricular rhythm (SVR) involves performing such characterization while the heart is being paced. During SVR characterization, various pacing parameters are modified and the patient's supraventricular rhythm is characterized while the pacing parameters are modified. The SVR characterization process is effective in single and multiple chamber pacing modes.

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: A cardiac rhythm management device is configured to discriminate between ventricular and supraventricular tachycardias (referred to as SVT/VT discrimination) by utilizing a morphology criterion in which the morphology of electrogram waveforms during ventricular beats are analyzed to determine if the beats are normally conducted. After the delivery of a cardioversion/defibrillation shock, however, the intraventricular conduction system is left in a modified state which alters the subsequently generated electrogram signal. Use of the morphology criterion for SVT/VT discrimination is discontinued after delivery of such a shock and resumed after a predetermined minimum number of normally conducted ventricular beats has been detected.

Abstract: Methods and devices for classifying a cardiac pacing response involve using a first electrode combination for pacing and a second electrode combination for sensing a cardiac signal following pacing. The cardiac response to pacing may be classified using the sensed cardiac signal. One process involves using the sensed cardiac signal to detect the cardiac response as a fusion/pseudofusion beat. Another process involves using the sensed cardiac signal to classify the cardiac response to pacing as one of at least three cardiac response types.

Abstract: Methods and devices for classifying a cardiac response to pacing involve establishing a plurality of classification windows relative to and following a pacing pulse. One or more characteristics of a cardiac signal sensed following the pacing pulse are detected within one or more particular classification windows. The characteristics may be compared to one or more references. Classification of the cardiac response may be performed based on the comparison of the one or more characteristics to the one or more references and the particular classification windows in which the one or more characteristics are detected.

Abstract: A method and system for generating a characterization of one beat of a patient's supraventricular rhythm (SVR) involves performing such characterization while the heart is being paced. During SVR characterization, various pacing parameters are modified and the patient's supraventricular rhythm is characterized while the pacing parameters are modified. The SVR characterization process is effective in single and multiple chamber pacing modes.

Abstract: A method and system provides for generating a snapshot representative of one beat of a patient's normal cardiac rhythm. Cardiac rate channel signals and shock channel signals are sensed. A fiducial point is determined for a predefined number of the cardiac rate channel signals. A predefined number of the shock channel signals are aligned using the fiducial point. A template is generated using the aligned shock channel signals, whereby the template is representative of one of the patient's normal supra-ventricular conducted cardiac beats. The template is updated on a periodic basis.

Abstract: The present invention provides a method and system for verifying capture in the heart. One or more pacing artifact templates characterizing a post pace artifact signal associated with a particular pace voltage or range of voltages are provided. A pacing artifact template is canceled from a cardiac signal sensed following a pacing pulse. Capture is detected by comparing the pacing artifact canceled cardiac signal to an evoked response reference. According to one aspect of the invention, the evoked response reference used to detect capture is an evoked response template. Capture is determined by comparing the evoked response template may be compared to the pacing artifact canceled cardiac signal. Fusion/pseudofusion detection may be determined by determining a correlation between a captured response template and a sensed cardiac signal.

Abstract: The present invention provides a method and system for detecting capture using pacing artifact cancellation. One or more pacing artifact templates are provided and a cardiac signal is sensed in a cardiac verification window. Each of the pacing artifact templates may characterize the pacing artifact associated with a particular pacing energy level, for example. A particular pacing artifact template is canceled from the cardiac signal. Capture is determined using the pacing artifact canceled cardiac signal. Detection of fusion/pseudofusion beats may be accomplished by comparing a cardiac signal to a captured response template.