Abstract: Modern implantable cardiac stimulation devices include processing and data storage capabilities that may be exploited to track myocardial condition and autonomic tone. Implantable devices have a capability to measure and store electrogram information over a period of time in a relatively large capacity memory, with advances in technology allowing increases in memory size. The evoked response varies in amplitude and morphology with changes in autonomic tone, ventricular filling, paced rate, and other parameters. The implantable cardiac device can be configured to sense and accurately quantify the evoked response, derive parameters from the quantified evoked response, store the parameters over long time periods, and derive variability statistics from the parameters to assist in tracking the patient's condition over time, and guiding the patient's therapy.

Abstract: An implantable cardiac stimulation device, e.g., a pacemaker or an implantable cardioverter defibrillator (ICD), is provided which prolongs the atrial refractoriness of a heart. The implantable cardiac stimulation device includes a generator that delivers pacing pulses to an atrium of a heart and a detector that detects atrial activations of the heart. An inhibitor is coupled to the detector that inhibits the generator when an atrial activation is detected within an escape interval. A generator control coupled to the generator causes the generator to deliver a primary pacing pulse to the atrium at the end of the escape interval, absent an atrial activation being detected within the escape interval, and causes the generator to deliver a secondary pacing pulse to the atrium a delay time after an atrial activation is detected within the escape interval or the delivery of a primary pacing pulse to the atrium.

Abstract: An implantable cardiac stimulation device is provided which alters the stimulation regime during determination of a capture threshold level. In order to avoid the potential for fusion beats which would interfere with a capture threshold level determination, a two-fold approach is used. First, the atrial refractoriness of the atrium of the patient's heart is extended by supplying a secondary atrial stimulation pulse during a prescribed time period following delivery of a primary atrial stimulation pulse. Second, the atrium is overdriven by providing an atrial stimulation pulse at a rate in excess of the intrinsic heart rate. Accordingly, the potential for fusion beats is significantly decreased and the reliability of the determined capture threshold level is increased. In a preferred embodiment, two closely placed stimulation pulses, i.e.

Abstract: Techniques for providing capture verification during overdrive pacing are described. If an overdrive pacing pulse fails to evoke capture (i.e. a loss of capture occurs), a high voltage backup pulse is automatically delivered. Once a second loss of capture occurs during a single sequence of overdrive pacing pulses, an overdrive pulse capture threshold detection search, described herein, is performed while overdrive pacing continues. Various techniques for providing rate recovery are also described herein. The rate recovery techniques are designed to avoid problems that might arise from possible fusion of intrinsic beats and overdrive pacing pulses that fail to evoke capture. In a first rate recovery technique, capture detection is suspended during rate recovery due to the possibility of fusion. Instead, an extra safety margin is added to the overdrive pulses.

Abstract: A system and associated method for acquiring, storing, and displaying evoked response signal features for the purposes of monitoring evoked response variability and evaluating the performance of automatic capture. The system further acquires, stores, and displays the number of suspected fusion events for the purpose of improving fusion avoidance through either automatic modification to fusion avoidance mechanisms or by providing a clinician with diagnostic information helpful in selecting programmable operating parameters.

Abstract: A method and apparatus for reducing the incidence of atrial arrhythmias by using an overdrive algorithm to determine the application of overdrive stimulation pulses to a patient's heart, e.g., in the atria. In a first aspect of the invention, the apparatus first determines an overdrive pacing rate and then applies pairs of temporally spaced (staggered) pacing pulses, i.e., primary and secondary pacing pulses, at the determined overdrive pacing rate. In a further aspect of the invention, the pairs of pacing pulses are applied at the overdrive pacing rate to multiple spatially spaced electrodes, i.e., electrodes distributed among multiple sites in a patient's heart, e.g., in the atria. In accordance with a first preferred embodiment, the electrodes may be distributed within a single atrium, e.g., the right atrium, of the patient's heart.

Abstract: An implantable cardiac stimulation device establishes communication with at least first and second external devices which communicate using first and second communication protocols, respectively, and wherein the first and second protocols are different. The implantable device includes a pulse generator configured to generate stimulation pulses and a telemetry circuit arranged to establish communication with the first and second external devices according to the first and second communication protocols, respectively. A control circuit coupled to the telemetry circuit and the pulse generator detects the first and second external devices based upon the protocol used in establishing communication to provide a first response when the first external device is detected and a second response when the second external device is detected.

Abstract: An implantable cardiac stimulation device with automatic threshold testing capabilities. The device utilizes an algorithm for measuring a first and a second threshold settings. The first threshold setting is determined by decreasing the stimulation energy from an initially high, supra-threshold value until loss of capture is detected, and is set as the pulse energy at which capture is still detected. The second threshold setting is determined by increasing the stimulation energy from an initially low, sub-threshold value until capture is detected, and is set as the stimulation energy at which capture is regained. The algorithm further determines if the threshold test results are reliable by comparing the difference between the first and second threshold settings to an expected difference, known as the Wedensky Effect value. A deviation from the Wedensky Effect value which is known for a given patient, indicates a discrepancy in the threshold test result.

Abstract: An implantable cardiac stimulation device and associated method perform an automatic calibration procedure for evaluating whether automatic capture verification can be recommended. The calibration procedure calculates and displays a number of variables for use by a medical practitioner in programming automatic capture operating parameters. An average paced depolarization integral (PDI) is determined from the cardiac signals following delivery of multiple stimulation pulse below and above capture threshold such that both pure lead polarization signals and evoked response signals may be analyzed. From the paced depolarization integral data, a capture threshold, a stimulation response curve, a minimum evoked response, a maximum lead polarization, an evoked response sensitivity, an evoked response safety margin, and a polarization safety margin are determined. Based on these variables, the calibration procedure determines if automatic capture verification can be recommended.

Abstract: An implantable stimulation device delivers a stimulation pulse in the ventricular chamber of a patient's heart and automatically adjusts a post-ventricular atrial blanking period. The stimulation device generates a ventricular stimulation pulse to trigger an evoked response, in order to produce a ventricular far-field signal that follows a successfully captured ventricular stimulation pulse. The stimulation device further includes an atrial sense circuit that senses the ventricular far-field signal, and a control system that adaptively segments the post-ventricular atrial blanking period in a post-ventricular atrial blanking period (PVAB) which is fixed in duration, and a variable far-field interval (FFI) window.

Abstract: A multi-chamber stimulation device and associated method reliably and automatically distinguish fusion from loss of capture during ventricular stimulation. The stimulation device provides immediate and accurate fusion detection when a loss of capture is suspected in the ventricles without delivering back-up stimulation pulses. To achieve this objective, the far-field signal present in the atrial channel is examined for evidence of a far-field R-wave whenever the ventricular channel detects a loss of capture. If a far-field R-wave is present, fusion is confirmed, and a far-field R-wave is absent, loss of capture is confirmed. Additionally, the stimulation device inhibits unnecessary back-up stimulation and threshold tests when fusion occurs, and provides appropriate adjustment of stimulation parameters based on confirmed fusion detection such that fusion re-occurrence is minimized.

Abstract: An implantable cardiac stimulation device includes a system that monitors progression or regression of a patient's heart condition. The system includes a plurality of electrode configurations for sensing cardiac activity of the heart. A sensing circuit provides an electrical signal representing electrical activity of the heart from each of the sensing electrode configurations. A processor coupled to the sensing circuit determines, at spaced apart times, and over time, a ventricular repolarization interval in each of the electrical signals and a corresponding ventricular repolarization interval dispersion. A memory stores the ventricular repolarization interval dispersions for transmission by a telemetry circuit to an external receiver for analysis.

Abstract: An implantable stimulator device provides automatic electrode polarity switching during an atrial capture verification mode. In systems using a bipolar sensing configuration in the atrium, polarity switching will be advantageous in detecting far-field R-waves for verification of capture. This automatic polarity switching feature is programmable and enables or disables automatic switching from bipolar to unipolar sensing at the onset of a far-field interval window and switching again back to bipolar pacing at the end of the far-field interval window.

Abstract: An implantable cardiac stimulation device establishes communication with at least first and second external devices which communicate using first and second communication protocols, respectively, and wherein the first and second protocols are different. The implantable device includes a pulse generator configured to generate stimulation pulses and a telemetry circuit arranged to establish communication with the first and second external devices according to the first and second communication protocols, respectively. A control circuit coupled to the telemetry circuit and the pulse generator detects the first and second external devices based upon the protocol used in establishing communication to provide a first response when the first external device is detected and a second response when the second external device is detected.

Abstract: An implantable cardiac stimulation device, e.g., a pacemaker or an implantable cardioverter defibrillator (ICD), is provided which prolongs the atrial refractoriness of a heart. The implantable cardiac stimulation device includes a generator that delivers pacing pulses to an atrium of a heart and a detector that detects atrial activations of the heart. An inhibitor is coupled to the detector that inhibits the generator when an atrial activation is detected within an escape interval. A generator control coupled to the generator causes the generator to deliver a primary pacing pulse to the atrium at the end of the escape interval, absent an atrial activation being detected within the escape interval, and causes the generator to deliver a secondary pacing pulse to the atrium a delay time after an atrial activation is detected within the escape interval or the delivery of a primary pacing pulse to the atrium.

Abstract: An implantable pacemaker delivers a stimulation pulse in the ventricular chamber of patient's heart and automatically verifies ventricular capture. A control system of the pacemaker sets a far-field interval window after a predetermined delay period from the delivery of the stimulation pulse, for verifying ventricular capture. The far-field interval window is approximately 100 msec, and provides an opportunity for the control system to sense the far-field signal that occurs in response to the stimulation pulse. The delivery of the stimulation pulse also initiates a post ventricular atrial blanking period on an atrial channel, and the far-field interval window is initiated during the post ventricular atrial blanking period.

Abstract: An implantable cardiac stimulation device is provided which alters the stimulation regime during determination of a capture threshold level. In order to avoid the potential for fusion beats which would interfere with a capture threshold level determination, a two-fold approach is used. First, the atrial refractoriness of the atrium of the patient's heart is extended by supplying a secondary atrial stimulation pulse during a prescribed time period following delivery of a primary atrial stimulation pulse. Second, the atrium is overdriven by providing an atrial stimulation pulse at a rate in excess of the intrinsic heart rate. Accordingly, the potential for fusion beats is significantly decreased and the reliability of the determined capture threshold level is increased. In a preferred embodiment, two closely placed stimulation pulses, i.e.

Abstract: A pacemaker, or other implantable medical device, connected to heart tissue, detects atrial and ventricular electrical signals. The pacemaker analyzes the signals to determine whether the signals are representative of P-waves or R-waves according to atrial and ventricular sensitivity threshold values. Signals determined to be P-waves or R-waves are identified as sensed signals. Otherwise the signals are identified as not-sensed signals. The pacemaker further determines whether the sensed signals were detected during a refractory period or an alert period and its current tracking mode (e.g., VDD, DDD vs. DDI, VVI). Information pertaining to these atrial and ventricular signals is transmitted to an external programmer which generates representative histograms. The histograms present the number of counts detected within each of a set of high pass filtered amplitude ranges and further indicate the relative numbers of sensed vs. not-sensed counts.

Abstract: An implantable pacemaker automatically verifies atrial capture and performs atrial stimulation energy assessment when atrial capture is absent. The pacemaker delivers a stimulation pulse in the atrial chamber of the heart and samples the resulting far-field signal from the ventricular chamber during a predetermined far-field interval window. The pacemaker then compares the far-field signal sample to a predetermined far-field signal recognition template. If the far-field signal sample is approximately equal to the far-field signal recognition template, then atrial capture is deemed verified; otherwise, the pacemaker performs an atrial stimulation energy determination. Optionally, the pacemaker automatically determines the timing of the far-field interval window and defines the far-field signal recognition template.

Abstract: The system of the present invention records and stores, in long-term memory and in form of data snapshots, medical data acquired prior to and subsequent to an occurrence of cardiac episodes and implantable device functions defined as important by the medical practitioner. The system provides the medical practitioner with the ability to specify trigger criteria representative of important cardiac episodes and implantable device functions. The system of the present invention allows the medical practitioner to control the amount of medical data stored in the data snapshots. The system allows the medical practitioner to specify a mode of storing data snapshots when the maximum storage capacity of long-term memory has been reached. In a first mode, the system stores data snapshots in a circular buffer manner, overwriting the older data snapshots. In a second mode, the system stops storing new data snapshots after the maximum storage capacity of long-term memory has been reached.