Abstract: A system and method provide precise detection of the time of occurrence of a cardiac event of a heart. The method comprises the steps of sensing electrical activity of the heart to generate an electrogram of the heart and applying the electrogram to an event detector having a plurality of spaced apart thresholds. The thresholds are selected such that the electrogram has an amplitude for crossing at least one of the thresholds. The method further comprises determining a characteristic identifying feature of the electrogram at each threshold crossing of the electrogram, comparing the determined characteristic identifying features to an electrogram template, and identifying the time of occurrence of the cardiac event based upon the comparison.

Abstract: During cross-chamber pacing, where anodal capture may not be desirable, pulses are applied between a cathode electrode in a first chamber and an anode electrode in a second chamber. A capture detector detects for capture of the second chamber by the pacing pulses. If capture of the second chamber persists, another electrode is selected as the anodal electrode. During single-chamber pacing, where anodal capture may be desirable, pulses are applied between a cathode electrode and an anode electrode associated with the same chamber. A capture detector detects for capture at both electrodes. If anodal capture is not detected, the energy of the pacing pulse is increased, until anodal capture is detected.

Abstract: Techniques are provided for updating a morphology template used to discriminate abnormal cardiac rhythms. In one example, a non-weighted candidate morphology template is generated based on far-field R-wave morphology. A weighted candidate morphology template is generated based on an ensemble average of the non-weighted candidate morphology template and a previous (i.e. active) morphology template. The previous morphology template is then selectively updated based on a comparison of additional R-waves against both the non-weighted and the weighted candidate templates. Thereafter, abnormal cardiac rhythms such as ventricular tachycardia and supraventricular tachycardia are discriminated using the updated morphology template based on newly-detected far-field R-waves. These techniques provide a method for updating the morphology discrimination template in response to long-term changes in morphology due to cardiac remodeling or cardiac disease progression.

Abstract: A system and method enables precise detection of the time of occurrence of a cardiac event of a heart. The method includes the steps of sensing electrical activity of the heart to generate an electrogram signal including the cardiac event, storing the electrogram signal, correlating the electrogram signal with an electrogram template, and identifying the time of occurrence of the cardiac event based upon the correlation.

Abstract: Techniques are provided for use by implantable medical devices such as pacemakers or by external systems in communication with such devices. An intracardiac electrogram (IEGM) is sensed within a patient in which the device is implanted using a cardiac signal sensing system. Cardiac events of interest such as arrhythmias, premature atrial contractions (PACs), premature ventricular contractions (PVCs) and pacemaker mediated tachycardias (PMTs) are detected within the patient using event detection systems and then portions of the IEGM representative of the events of interest are recorded in device memory. Subsequently, during an off-line or background analysis, the recorded IEGM data is retrieved and analyzed to identify false detections. In response to false detections, the cardiac signal sensing systems and/or the event detection systems of the implantable device are selectively adjusted or reprogrammed to reduce or eliminate any further false detections, including false-positives or false-negatives.

Abstract: Techniques are provided for use by implantable medical devices such as pacemakers or by external systems in communication with such devices. An intracardiac electrogram (IEGM) is sensed within a patient in which the device is implanted using a cardiac signal sensing system. Cardiac events of interest such as arrhythmias, premature atrial contractions (PACs), premature ventricular contractions (PVCs) and pacemaker mediated tachycardias (PMTs) are detected within the patient using event detection systems and then portions of the IEGM representative of the events of interest are recorded in device memory. Subsequently, during an off-line or background analysis, the recorded IEGM data is retrieved and analyzed to identify false detections. In response to false detections, the cardiac signal sensing systems and/or the event detection systems of the implantable device are selectively adjusted or reprogrammed to reduce or eliminate any further false detections, including false-positives or false-negatives.

Abstract: Techniques are provided for updating a morphology template used to discriminate abnormal cardiac rhythms. In one example, a non-weighted candidate morphology template is generated based on far-field R-wave morphology. A weighted candidate morphology template is generated based on an ensemble average of the non-weighted candidate morphology template and a previous (i.e. active) morphology template. The previous morphology template is then selectively updated based on a comparison of additional R-waves against both the non-weighted and the weighted candidate templates. Thereafter, abnormal cardiac rhythms such as ventricular tachycardia and supraventricular tachycardia are discriminated using the updated morphology template based on newly-detected far-field R-waves. These techniques provide a method for updating the morphology discrimination template in response to long-term changes in morphology due to cardiac remodeling or cardiac disease progression.

Abstract: A method for operating an implantable medical device includes delivering a plurality of pacing pulses to an atria of a patient's heart and monitoring intrinsic atrial activity to detect intrinsic atrial contractions between one or more of the plurality of pacing pulses. The method further includes detecting atrial undersensing as a function of the detection of intrinsic atrial contractions.

Abstract: A two-dimensional refractory period is defined in conjunction with the detection of cardiac events. Detection parameters associated with the two-dimensional refractory period may define a period of time during which a sensed cardiac signal is blanked or may define a period of time during which a given sensing threshold applies. The two-dimensional refractory period may be employed in atrial sensing to selectively blank far-field T-waves while enabling P-wave detection. The two-dimensional refractory period may be employed in ventricular sensing to selectively blank near-field T-waves while enabling detection of the QRS complex. The detection parameters associated with the two-dimensional refractory period may be adapted based on characteristics of previously detected cardiac signals.

Abstract: Techniques for detecting tachyarrhythmia and also for preventing T-wave oversensing use signals filtered by a narrowband bradycardia filter in combination with signals filtered by a narrowband tachycardia filter. A separate wideband filter may also be used.

Abstract: A method is provided to determine pacing parameters for an implantable medical device (IMD) and collects heart sounds during the cardiac cycles. The method comprises changing a value for a pacing parameter between the cardiac cycles and analyzing a characteristic of interest from the heart sounds. The method comprises setting a desired value for the pacing parameter based on the characteristic of interest from the heart sounds. The system comprises inputs configured to be coupled to at least one lead having electrodes to sense intrinsic events and to deliver pacing pulses over cardiac cycles. The system has a sensor for collecting heart sounds during cardiac cycles and controller to control delivery of pacing pulses based on pacing parameters. The controller changes a value for at least one of the pacing parameters between the cardiac cycles and provides an analysis module to analyze a characteristic of interest from the heart sounds.

Abstract: A method for operating an implantable medical device includes delivering a plurality of pacing pulses to an atria of a patient's heart and monitoring intrinsic atrial activity to detect intrinsic atrial contractions between one or more of the plurality of pacing pulses. The method further includes detecting atrial undersensing as a function of the detection of intrinsic atrial contractions.

Abstract: A cardiac monitoring system includes a communication subsystem, a comparison module, and a display module. The communication subsystem receives literal data from a cardiac medical device. The literal data includes cardiac signals and marker data. The cardiac signals represent electrical activity of a heart that is sensed by the medical device. The marker data represents one or more algorithms running on the medical device. The comparison module compares the cardiac signals and marker data to one or more heuristic rules to derive heuristic information about the cardiac signals and the marker data. The heuristic information represents a relationship among the cardiac signals and the marker data. The display module directs a display device to visually present the cardiac signals and a visual indicator representative of the heuristic information. The heuristic information can assist an operator, such as a physician, in changing one or more algorithms running on the medical device.

Abstract: Systems and methods are provided for use by an implantable medical device capable of automatically adjusting the sensitivity with which electrical cardiac signals are sensed within a patient, i.e. a device equipped with Automatic Sensitivity Control (ASC.) In a first example, ASC parameters are automatically adjusted by the device itself based on parameters derived from both R-waves and T-waves and further based on a detected noise floor. In a second example, a profile representative of the shape of cardiac signals is generated by the device. ASC parameters are then adjusted based on the profile. In various embodiments, histograms are used to determine sizes and shapes of the R-waves and T-waves via statistical prevalence techniques. The histograms are also employed to derive the aforementioned profile.

Abstract: Techniques for detecting tachyarrhythmia and also for preventing T-wave oversensing use signals filtered by a narrowband bradycardia filter in combination with signals filtered by a narrowband tachycardia filter. A separate wideband filter may also be used.

Abstract: Systems and methods are provided for use by an implantable medical device capable of automatically adjusting the sensitivity with which electrical cardiac signals are sensed within a patient, i.e. a device equipped with Automatic Sensitivity Control (ASC.) In a first example, ASC parameters are automatically adjusted by the device itself based on parameters derived from both R-waves and T-waves and further based on a detected noise floor. In a second example, a profile representative of the shape of cardiac signals is generated by the device. ASC parameters are then adjusted based on the profile. In various embodiments, histograms are used to determine sizes and shapes of the R-waves and T-waves via statistical prevalence techniques. The histograms are also employed to derive the aforementioned profile.

Abstract: An implantable medical device includes a lead, a pulse generator, an autothreshold module and a control module. The lead includes electrodes positioned within a heart. At least one of the electrodes senses cardiac signals. The pulse generator delivers a stimulus pulse through at least one of the electrodes. The autothreshold module performs a threshold search when operating in an autothreshold mode and causes atrial stimulus pulses to be delivered in an atrium of the heart at an overdrive rate during the threshold search. The control module determines an AV conduction time and applies an overdrive AV adjustment to the AV conduction time to generate an AV delay. The autothreshold module uses the AV delay in connection with delivering ventricular stimulus pulses to a ventricle of the heart.

Abstract: An implantable medical device includes a first, short-range telemetry circuit; a second, long-range telemetry circuit; a first power system that powers the first telemetry circuit; and a second power system that powers the second telemetry circuit. The second power system includes an internal charging system and a rechargeable battery coupled to the internal charging system. The internal charging system may be configured for electromagnetic-inductive or RF-transmission coupling with an external charging system. A controller monitors the energy level of the rechargeable battery and provides an signal indicative of the level.

Abstract: During a period of time comprising a plurality of cardiac cycles, a time relationship between ventricular events and atrial detections is established. Based on the relationship, a post-ventricular atrial refractory period is defined. The period includes an absolute atrial refractory period and a segmented relative atrial refractory period, wherein the segmented relative atrial refractory period includes at least one blanking window during which atrial detections of ventricular events have or are likely to occur.

Abstract: An implantable medical device includes a lead, a pulse generator, an autocapture module, an autothreshold module, a fusion detection module, and a control module. The lead includes electrodes configured to be positioned within a heart. At least one of the electrodes is capable of sensing cardiac signals. The pulse generator delivers a stimulus pulse through at least one of the electrodes. The autocapture module senses an evoked response of the heart after delivery of the stimulus pulse when operating in an autocapture mode. The autothreshold module performs a threshold search when operating in an autothreshold mode. The fusion detection module identifies fusion-based behavior in the heart. The control module automatically switches between the autothreshold and autocapture modes based on a presence of the fusion-based behavior.