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: An implantable medical device can include a therapy circuit coupled to a therapy delivery terminal, the therapy circuit configured to generate a specified electrostimulation therapy for delivery to a tissue site via the therapy delivery terminal, and a measurement circuit for measuring at least two impedances of a first terminal combination including the therapy delivery terminal, the two impedances corresponding to at least two instances of excitation separated enough in time to capture an impedance artifact due at least in part to a motion of the heart, such as to determine an electrostimulation therapy lead status at least in part using the at least two impedances.

Abstract: An implantable medical device delivers anti-tachyarrhythmia therapies including anti-tachycardia pacing (ATP). If a detected tachyarrhythmia is classified as a type suitable for treatment using ATP, the implantable medical device selects one of an atrial ATP (A-ATP) mode, a ventricular ATP (V-ATP) mode, and a concurrent atrio-ventricular ATP (concurrent AV-ATP) mode according to the characteristics of the detected tachyarrhythmia. The concurrent ATP mode is an ATP mode during which the atrial pacing pulses and the ventricular pacing pulses are delivered concurrently. In one embodiment, the concurrent AV-ATP mode includes a synchronized atrio-ventricular ATP (synchronized AV-ATP) mode during which atrial and ventricular pacing pulses are delivered synchronously and an independent atrio-ventricular ATP (independent AV-ATP) mode during which atrial and ventricular pacing pulses are delivered concurrently but timed independently.

Abstract: One aspect of this disclosure relates to an apparatus for providing a selective capacitance. An embodiment of the apparatus includes a first and second capacitor in a stack, and a switching circuit connected between the first and second capacitors. The switching circuit has at least two states, and is adapted to provide a first defibrillation capacitance in a first state and a second defibrillation capacitance in a second state. A switching circuit embodiment includes a field effect transistor (FET) adapted to have a source connected to the first capacitor and a drain connected to the second capacitor, a bipolar junction transistor (BJT) adapted to have an emitter connected to the source of the FET and a collector connected to a gate of the FET, a first current source connected to the collector of the BJT, and a second current source connected to a base of the BJT.

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: 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: 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 to 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: A method of using an implantable medical device (IMD) to monitor a ventricular contraction rate of a subject, monitor an atrial contraction rate of the subject, declare tachyarrhythmia if the ventricular contraction rate exceeds the atrial contraction rate, and declare a slow tachyarrhythmia when the ventricular rate exceeds the atrial rate and the ventricular rate is less than a specified maximum pacing rate.

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: An implantable or other ambulatory device, such as a pacer, defibrillator, or other cardiac function management device, can use imaging information, such as one or more of cardiac functional magnetic resonance imaging (fMRI) information or cardiac magnetic resonance imaging (MRI) information, such as for helping optimize one or more parameters of the implantable or other ambulatory device.

Abstract: An ambulatory or implantable device, such as a pacer, defibrillator, or other cardiac rhythm management device, can tolerate magnetic resonance imaging (MRI) or other noise without turning on an integrated circuit diode by selectively providing a bias voltage that can overcome an expected induced voltage resulting from the MRI or other noise.

Abstract: An implantable device, such as a pacer, defibrillator, or other cardiac rhythm management device, can include a failsafe backup, such as a separate and independent safety core that can assume control over operation of the implantable device from a primary controller. In an example, the safety core can include a normal first safety core operating mode and a magnetic resonance imaging (MRI) second safety core operating mode that can provide different functionality from the normal first safety core operating mode.

Abstract: Physiologic information can be received from a subject during a portion of a magnetic resonance imaging (MRI) session using a sensing circuit of an implantable medical device (IMD). An indication of an active MRI scan can be received, and a time period to inhibit use of physiological information from the subject can be determined following the received indication of the active MRI scan.

Abstract: An implantable medical device can include a hermetically-sealed implantable housing, an exposed first conductor located on or near the housing, and at least one insulated second conductor located near the exposed first conductor. In an example, the implantable medical device can include an isolation test circuit to provide a test stimulus to the exposed first conductor and configured to measure a portion of the test stimulus coupled to the second conductor.

Abstract: An apparatus comprises first and second sensing circuits, a template generator circuit, and a correlation circuit. The correlation circuit is configured to identify a first fiducial position in a third cardiac signal sensed using the first sensing circuit during a detected rhythm with elevated ventricular rate, align the template correlation features and the correlation features of a fourth cardiac signal using the first fiducial position, calculate a correlation using the correlation features of the template and the correlation features of the fourth cardiac signal, and iteratively searching for a replacement to the first fiducial position in the third cardiac signal according to the calculated correlation.

Abstract: An apparatus comprising an implantable cardiac signal sensing circuit configured for sensing an intrinsic cardiac signal, a memory to store a template of a morphology of normal atrial-ventricular conduction, and a controller that includes a tachyarrhythmia detection circuit and a correlation circuit. The tachyarrhythmia detection circuit is configured for detecting a rhythm with elevated ventricular rate using the sensed intrinsic cardiac signal. The correlation circuit is configured for iteratively calculating a correlation between the sensed intrinsic cardiac signal and the template, and comparing the calculated correlation to a variable correlation threshold to determine whether the detected rhythm correlates to the template. The apparatus also includes a therapy circuit configured for inhibiting a ventricular tachycardia therapy when the detected rhythm correlates to the template. Other apparatuses and methods are described.

Abstract: A cardiac rhythm management system can be used to detect episode beats associated with cardiac events in a subject's body. These events may be monitored and depolarization morphology information can be derived for candidate arrhythmic beats in an arrhythmia episode. An arrhythmic beat morphology template may be formed from selecting at least one of the candidate arrhythmic beats based upon user's labeling according to specific morphologies of one or more candidate episodes. Methods of use are also presented.

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: This document discusses, among other things, detection of a sudden onset of a tachyarrhythmia. A sudden onset of tachyarrhythmia is determined by monitoring changes in intrinsic ventricular rate, such as by using one or more sensing channels in the ICD. A lowest tachyarrhythmia rate threshold is accompanied by a slightly lower “hysteresis tachyarrhythmia rate threshold.” If a sudden onset of tachyarrhythmia is declared, the sudden onset status is not reset by the ventricular rate falling below the lowest tachyarrhythmia rate threshold, but is instead reset by the ventricular rate falling below the slightly lower hysteresis tachyarrhythmia rate threshold.